fixing device

专利摘要:
FIXING DEVICE. The present invention relates to a fixation device configured to fix an image to a recording material that includes: a cylindrical rotating element including an electroconductive layer; a coil having a spiral-shaped part which is arranged within the rotating element; and a core arranged in the spiral-shaped part; with the magnetic resistance of the core being, with an area from one end to the other end of the region of maximum image passage in a recording material in the generatrix direction, equal to or less than 30% of the combined magnetic resistance consisting of the magnetic resistance of the electroconductive layer and magnetic resistance of a region between the electroconductive layer and the core.
公开号:BR112014031156B1
申请号:R112014031156-0
申请日:2013-06-13
公开日:2022-02-01
发明作者:Yuki Nishizawa；Hiroshi Mano；Minoru Hayasaki；Aoji Isono；Akira Kuroda；Toshio Miyamoto；Michio Uchida；Seiji Uchiyama
申请人:Canon Kabushiki Kaisha；
IPC主号:

专利说明:

Field of Invention
[0001] The present invention relates to a fixture to be installed in an image forming apparatus such as a copier with electrophotography system, printer or the like. Fundamentals of Invention
[0002] In general, a fixture to be installed in an imaging apparatus such as an electrophotography copier, printer, or the like, is configured to heat a recording material where a toner image does not Fixed is loaded to fix the toner image onto the recording material while conveying the recording material through a nip portion formed of a rotating cylindrical heating element and a pressing roller which is in contact therewith.
[0003] In recent years, a fastening device with an electromagnetic induction heating system where an electroconductive layer of a rotating cylindrical heating element can be directly heated has been developed and put into practice. The clamping device with electromagnetic induction heating system has the advantage that the heating time is short.
[0004] With the fixtures described in PTL 1, PTL 2 and PTL 3, according to an eddy current induced in an electroconductive layer of a rotating cylindrical heating element with a magnetic field generated from a magnetic field generator , the electroconductive layer is heated. With such fixtures as the electroconductive layer of the rotating cylindrical heating element, the magnetic metal which readily passes magnetic flux such as iron, nickel or the like whose thickness is 200 mm to 1 mm, or an alloy mainly consisting thereof, is employed.
[0005] Incidentally, in order to try to reduce the heating time of a fixture, the heating capacity of the rotating cylindrical heating element has been reduced, and consequently, it is advantageous that the thickness of the electroconductive layer of the rotating cylindrical heating element be small. However, with the fixtures described in the literature mentioned above, reducing the thickness of the rotating cylindrical heating element results in deterioration of the heating efficiency. Furthermore, with regard to the fixing devices described in the literature mentioned above, even in the case of using a material whose relative permeability is low, the heating efficiency deteriorates. Then, with the fixtures described in the literature mentioned above, a thick material having high relative permeability was selected as the material of the rotating cylindrical heating element.
[0006] Consequently, the fixtures described in the literatures mentioned above have a problem that a material to be used as the electroconductive layer of the rotating cylindrical heating element is restricted to a material having high relative permeability, and restrictions are imposed. in costs, material processing method, and device configuration. Citation List Patent Literature Japanese Patent PTL 1 Submitted to Public Inspection No. 2000-81806 Japanese Patent PTL 2 Submitted to Public Inspection No. 2004-341164 Japanese patent PTL 3 submitted to public inspection No. 9-102385 Summary of the Invention
[0007] The present invention provides a fastening device where restrictions regarding the thickness and material of an electroconductive layer are small, and the electroconductive layer can be heated with high efficiency.
[0008] According to a first embodiment of the invention, a fixing device configured to fix an image to a recording material by heating the recording material on which the image is formed, includes: a cylindrical rotating element including a electroconductive layer; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, which has a spiral-shaped portion that is arranged on the cylindrical rotating element such that a spiral axis of the spiral-shaped portion is positioned substantially in parallel with a generating direction of the cylindrical rotating element; and a core configured to induce a line of magnetic force from the alternating magnetic field, which is arranged in the spiral-shaped portion; with core reluctance being, with an area from one end to the other end of the region of maximum image pass in a recording material in the generatrix direction, equal to or less than 30% of the combined magnetic resistance consisting of the magnetic resistance of the electroconductive layer and magnetic resistance of a region between the electroconductive layer and the core.
[0009] According to a second embodiment of the invention, a fixing device configured to fix an image to a recording material by heating the recording material on which the image is formed, including: a cylindrical rotating element including an electroconductive layer ; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, having a spiral-shaped portion that is arranged on the cylindrical rotating element such that a spiral axis of the spiral-shaped portion is positioned substantially in parallel with a generating direction of the cylindrical rotating element; and a core configured to induce lines of magnetic force from the alternating magnetic field, which has a shape where a loop is not formed outside the cylindrical rotating member and is arranged in the spiral-shaped portion; with 70% or more lines of magnetic force emitted from one end in the generative direction of the core passing over the outside of the electroconductive layer and returning to the other end of the core.
[0010] According to a third embodiment of the invention, a fixing device configured to fix an image to a recording material by heating the recording material on which the image is formed, including: a cylindrical rotating element including an electroconductive layer ; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, which has a spiral-shaped portion that is arranged on the cylindrical rotating element such that a spiral axis of the spiral-shaped portion is positioned substantially in parallel with a generating direction of the cylindrical rotating element; and a core configured to induce lines of magnetic force from the alternating magnetic field, which is arranged in the spiral portion; with relative permeability of the electroconductive layer and relative permeability of an element in the area between the electroconductive layer and the core, in an area from one end to the other end of the region of maximum image pass in a recording material in the generatrix direction, being less than than 1.1; and where the fixture satisfies the following relational expression (1) with a cross section perpendicular to the generating direction over the entire area: 0.06 x μc x Sc > Ss + Sa (1) where Ss represents a cross-sectional area of the electro layer - conductive, Sa represents a cross-sectional area of a region between the electroconductive layer and the core, Sc represents a cross-sectional area of the core, and mc represents a relative permeability of the core.
[0011] According to a fourth embodiment of the invention, a fixing device configured to fix an image to a recording material by heating the recording material on which the image is formed, including: a cylindrical rotating element including an electroconductive layer ; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, which has a spiral-shaped portion that is arranged on the cylindrical rotating element so that the spiral axis of the spiral-shaped portion is positioned substantially in parallel with a generating direction of the cylindrical rotating element; and a core configured to induce lines of magnetic force from the alternating magnetic field, which is arranged in the spiral portion; with the electroconductive layer being formed of a non-magnetic material, and the core having a shape where a loop is not formed outside the cylindrical rotating element.
[0012] According to a fifth embodiment of the invention, a fixing device configured to fix an image to a recording material by heating the recording material on which the image is formed, including: a cylindrical rotating element including an electroconductive layer ; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, which has a spiral-shaped portion that is arranged on the cylindrical rotating element so that a spiral axis of the spiral-shaped portion is positioned substantially in parallel with a generating direction of the cylindrical rotating element; and a core configured to induce lines of magnetic force from the alternating magnetic field, which is arranged in the spiral portion; with the electroconductive layer being formed of a non-magnetic material, and the thickness of the electroconductive layer being equal to or less than 75 mm. Brief Description of Drawings
[0013] Figure 1 is a perspective view of a fastening film, a magnetic core, and a coil.
[0014] Figure 2 is a schematic configuration diagram of an imaging apparatus according to a first embodiment.
[0015] Figure 3 is a schematic cross-sectional view of a fixture according to the first embodiment.
[0016] Figure 4A is a schematic view of a magnetic field of a magnetic field in the vicinity of a solenoid coil.
[0017] Figure 4B is a schematic diagram of a magnetic flux density distribution on a solenoid central axis.
[0018] Figure 5A is a schematic view of a magnetic field in the vicinity of a solenoid coil and a magnetic core.
[0019] Figure 5B is a schematic diagram of a magnetic flux density distribution on a solenoid central axis.
[0020] Figure 6A is a schematic view of the vicinity of an end part of a magnetic core of a solenoid coil.
[0021] Figure 6B is a schematic diagram of a magnetic flux density distribution on a solenoid central axis.
[0022] Figure 7A is a schematic view of a coil shape and a magnetic field.
[0023] Figure 7B is a schematic diagram of a region where a magnetic flux penetrating a circuit is stabilized.
[0024] Figure 8A is a schematic view of a coil shape in a magnetic field.
[0025] Figure 8B is a schematic diagram of a region where a magnetic flux is stabilized.
[0026] Figure 9A is a diagram illustrating an example of lines of magnetic force for the purpose of a first embodiment.
[0027] Figure 9B is a diagram illustrating an example of lines of magnetic force under the purpose of the first embodiment.
[0028] Figure 9C is a diagram illustrating an example of lines of magnetic force under the purpose of the first embodiment.
[0029] Figure 10A is a schematic view of a structure where a finite length solenoid is arranged.
[0030] Figure 10B is a cross-sectional view and a side view of the structure.
[0031] Figure 11A is a space magnetic equivalent circuit diagram including a core, a coil, and a cylinder body per unit length.
[0032] Figure 11B is a magnetic equivalent circuit diagram of a configuration according to the first embodiment.
[0033] Figure 12 is a schematic view of a magnetic core and a space.
[0034] Figure 13A is a schematic cross-sectional view of current and magnetic field within a cylindrical rotating element.
[0035] Figure 13B is a longitudinal perspective view of the cylindrical rotating element.
[0036] Figure 14A is a diagram illustrating the conversion of high frequency current from an excitation coil to jacket circumference current.
[0037] Figure 14B is an equivalent circuit of an excitation coil and a jacket.
[0038] Figure 15A is an explanatory diagram regarding circuit efficiency.
[0039] Figure 15B is an explanatory diagram regarding circuit efficiency.
[0040] Figure 15C is an explanatory diagram regarding circuit efficiency.
[0041] Figure 16 is a diagram of an experimental device to be used for energy conversion efficiency measurement experiments.
[0042] Figure 17 is a diagram illustrating a relationship between a relationship of lines of magnetic force outside a cylindrical rotating element and conversion efficiency.
[0043] Figure 18A is a diagram illustrating a relationship between conversion efficiency and a frequency with the first mode configuration.
[0044] Figure 18B is a diagram illustrating a relationship between conversion efficiency and thickness with the first embodiment configuration.
[0045] Figure 19 is a schematic diagram of a fixture at the time of a magnetic core being split.
[0046] Figure 20 is a schematic diagram of lines of magnetic force at the moment a magnetic core is split.
[0047] Figure 21 is a diagram illustrating the measured results of energy conversion efficiency with the first modality configurations and a comparative example 1.
[0048] Figure 22 is a diagram illustrating the measured results of energy conversion efficiency with the second modality configurations and a comparative example 2.
[0049] Figure 23 is a diagram illustrating a configuration of a fixture with induction heating system serving as comparative example 2.
[0050] Figure 24 is a schematic view of a magnetic field in a fixture with induction heating system serving as comparative example 2.
[0051] Figure 25A is a schematic cross-sectional view of a magnetic field in the fixture with induction heating system serving as comparative example 3.
[0052] Figure 25B is an enlarged schematic cross-sectional view of a magnetic field in the induction heating fixture serving as comparative example 3.
[0053] Figure 26 is a diagram illustrating the measured results of energy conversion efficiency with the configurations of a third modality and a comparative example 3.
[0054] Figure 27 is a cross-sectional view in the longitudinal direction of a magnetic core and a coil of a comparative example 4.
[0055] Figure 28 is a schematic diagram of a magnetic field in a fixture with induction heating system serving as comparative example 4.
[0056] Figure 29A is an explanatory diagram of an eddy current direction in the fixture with induction heating system serving as comparative example 4.
[0057] Figure 29B is an explanatory diagram of an eddy current direction in the fixture with induction heating system serving as comparative example 4.
[0058] Figure 29C is an explanatory diagram of an eddy current direction in the fixture with induction heating system serving as comparative example 4.
[0059] Figure 30 is a diagram illustrating the measured results of energy conversion efficiency with the configurations of a fourth modality and comparative example 4.
[0060] Figure 31 is an explanatory diagram of an E// eddy current.
[0061] Figure 32 is an explanatory diagram of an eddy current El.
[0062] Figure 33A is a diagram illustrating a shape of a magnetic core according to another embodiment.
[0063] Figure 33B is a diagram illustrating a shape of a magnetic core according to another embodiment.
[0064] Figure 34 is a diagram illustrating an air core clamping device.
[0065] Figure 35 is a diagram illustrating a magnetic core in the case of forming a closed magnetic path.
[0066] Figure 36 is a cross-sectional configuration diagram of a fixture according to a fifth embodiment.
[0067] Figure 37 is an equivalent circuit of a magnetic path of the fixture according to the fifth embodiment.
[0068] Figure 38 is a diagram to describe a shape of the magnetic force line and reduction in the amount of heat.
[0069] Figure 39 is a schematic configuration diagram of a fixture according to a sixth embodiment.
[0070] Figure 40A is a cross-sectional view of the fixture according to the sixth embodiment.
[0071] Figure 40B is a cross-sectional view of the fixture according to the sixth embodiment. Detailed Description of the Invention First Mode (1) Example of Image Formation Device
[0072] Next, an embodiment of the present invention will be described based on the drawings. Figure 2 is a schematic configuration diagram of an imaging apparatus 100 in accordance with the present embodiment. The imaging apparatus 100 according to the present embodiment is a laser beam printer using an electrophotographic process. 101 denotes a rotating drum-like electrophotographic photosensitive element (hereinafter called a photosensitive drum) serving as an image supporting element, and is driven by rotation with the predetermined peripheral speed. The photosensitive drum 101 is regularly charged with a predetermined polarity and a predetermined potential by a charging cylinder 102 in the process of rotation. 103 denotes a laser beam digitizer serving as an ex-position unit. The scanner 103 emits a laser beam L modulated according to the image information to be input from an external device such as an unpictured image scanner or computer or the like, and exposes a charged face of the photosensitive drum 101 by scanning . In accordance with this scan exposure, the charge on the surface of the photosensitive drum 101 is removed, an electrostatic latent image according to the imaging information is formed on the surface of the photosensitive drum 101. 104 denotes a developing apparatus, toner is supplied from a developing roller 104a to the surface of the photosensitive drum 101, and an electrostatic latent image is formed as a toner image. 105 denotes a paper feed cassette in which recording material P that is loaded is housed. A paper feed roller 106 is actuated based on a paper feed start signal, and the recording material P inside the paper feed cassette 105 is fed by pulling apart one sheet at a time. The recording material P is introduced into a transfer part 108T formed from the photosensitive drum 101 and a transfer roller 108 via a recording roller 107 at a predetermined time. Specifically, at the moment when a leading end part of a toner image on the photosensitive drum 101 reaches the transfer part 108T, the transport of recording material P is controlled by the registration roller 107 so that the leading end part of the recording material P reaches transfer point 108T. While recording material P introduced into transfer part 108T is conveyed to that transfer part 108T, transfer inducing voltage is applied to transfer cylinder 108 by applied transfer inducing energy which is not illustrated. Transfer induction voltage having the opposite polarity of the toner is applied to the transfer cylinder 108, and accordingly, a toner image on the surface side of the photosensitive drum 101 is transferred to the surface of the recording material P on the back side. transfer 108T. The recording material P on which the toner image has been transferred onto the transfer part 108T is separated from the surface of the photosensitive drum 101 and undergoes a fixing process in a fixture A via an orientation guide 109. The fixture A will be described later. On the other hand, the surface of the photosensitive drum 101, after the recording material is separated from the photosensitive drum 101, is subjected to cleaning in a cleaning device 110, and is repeatedly used for the imaging operation. Recording material P passing through fixture A is discharged into a paper output tray 112 from a paper output port 111. (2) Fixation Device 2-1. Schematic Configuration
[0073] Figure 3 is a schematic cross-sectional view of the fixture. According to the first embodiment, the fastening device A includes a fastening film serving as a cylindrical rotating cylindrical heating element, a film guide 9 (belt guide) serving as a nip part forming element that is in contact with the inner face of the fixing film 1, and a pressing cylinder 7 serving as an opposing element. The press cylinder 7 forms a nip part N together with the nip part forming element via the fixing film 1. The embossing material P, where a toner image T is supported, is heated while being transported by the nip part N to fix the toner image T on the recording material P.
[0074] The nip part forming element 9 is pressed against the pressing cylinder 7 placing the fixing film 1 between them by pressing force around the total pressure of 50 N to 100 N (approximately 5 kgf at approximately 10 kgf) using a bearing unit not shown and a pressing unit. Press cylinder 7 is driven by rotation in an arrow direction using a drive source not shown, the rotational force acts on the clamping film 1 according to the friction force on the nip portion N, and the clamping film 1 is driven by pressing cylinder 7 to rotate. The narrowing part forming element 9 also has the function of serving as a film guide configured to guide the inner face of the fixing film 1, and is made of polyphenylene sulfide (PPS) which is a heat resistant resin. , or similar.
[0075] Fixing film 1 (fixing strap) includes an electroconductive layer 1a (base layer) made of metal whose diameter (outside diameter) is 10 to 100 mm, an elastic layer 1b formed on the outside of the electroconductive layer 1a, and a surface layer 1c (release layer) formed on the outside of the elastic layer 1b. Next, the electroconductive layer 1a will be called “cylindrical rotating element” or “cylindrical element”. Fixing film 1 has flexibility.
[0076] With the first embodiment, as the cylindrical rotating element 1a, aluminum whose relative permeability is 1.0, and the thickness is 20 mm is employed. As the material of the cylindrical rotating element 1a, copper (Cu) or silver (Ag) which is a non-magnetic element can be used, or austenitic stainless steel (SUS) can be used. As one of the characteristics of the present modality, it is mentioned that there are many options of materials to be used as the cylindrical rotating element 1a. Thus, there is an advantage that a material that excels in workability, or an inexpensive material, can be employed.
[0077] The thickness of the cylindrical rotating element 1a is equal to or less than 75 mm, and preferably equal to or less than 50 mm. This is because it is desirable to provide adequate flexibility to the cylindrical rotating element 1a, and also to reduce its amount of heat. A small diameter is advantageous to reduce the amount of heat. Another advantage of reducing the thickness to 75 mm or preferably equal to or less than 50 mm is the improvement in flexibility performance. Fixing film 1 is driven by rotation in a pressed state by nip part forming element 9 and pressing cylinder 7. Fixing film 1 is pressed and deformed at nip part N and receives stress for each rotation. Even if this repeating curvature is continuously applied to the fastening film 1 until the life of the fastening device, the electroconductive layer 1a made of metal of the fastening film 1 must be designed so as not to cause breakage by fatigue. By reducing the thickness of the electrically conductive layer 1a, the tolerability against fatigue failure of the electrically conductive layer 1a made of metal is significantly improved. This is because when the electroconductive layer 1a is pressed and deformed according to the shape of the curved surface of the nip forming element 9, the thinner the electroconductive layer 1a, the lower the internal stress acting on the layer electrical conductor 1a. In general, when the thickness of a layer of metal to be used for the bonding film reaches 50 mm or less, this effect becomes marked, and it is able to obtain sufficient tolerability against fatigue failure. According to the reasons mentioned above, in order to realize the minimization of the amount of heat, and the improvement in tolerability against fatigue rupture, it is important to make full use of the electroconductive layer 1a in order to suppress its thickness to 50 mm or less. The present embodiment has an advantage that the thickness of the electroconductive layer 1a can be reduced to 50 mm or less even with a fastening device with an electromagnetic induction heating system.
[0078] The elastic layer 1b is formed of silicon rubber whose hardness is 20 degrees (JIS-A, 1 kg load), and in a thickness of 0.1 to 0.3 mm. Additionally, the fluorocarbon resin tube whose thickness is 10 to 50 mm is covered in the elastic layer 1b as the surface layer 1c (release layer). A magnetic core 2 is inserted into a hollow part of the fixing film 1 in the generative direction of the fixing film 1. An excitation coil 3 is wound around the outer circumference of its magnetic core 2. 2-2. Magnetic Core
[0079] Figure 1 is a perspective view of the cylindrical rotating element 1a (electroconductive layer), magnetic core 2, and excitation coil 3. The magnetic core 2 has a cylindrical shape, and is disposed substantially in the center of the fixing film. 1 for a fastening unit not shown. The magnetic core 2 has a function configured to induce lines of magnetic force (magnetic flux) from an alternating magnetic field generated in the excitation coil 3 to the cylindrical rotating element 1a (region between the cylindrical rotating element 1a and the magnetic core 2) and to form a path (magnetic path) for the magnetic line of force. It is desirable that the material of this magnetic core 2 be ferromagnetic made up of oxide or alloy having low hysteresis loss and high magnetic permeability, for example, such as baking ferrite, ferrite resin, amorphous alloy, permalig and so on. In particular, in the case of applying a high frequency alternating current of a band from 21 kHz to 100 kHz to the excitation coil, baking ferrite having small loss in a high frequency alternating current is desirable. It is desirable to maximize the cross-sectional area of the magnetic core 2 within a range storable in the hollow part of the cylindrical rotating element 1a. With the present embodiment, the diameter of the magnetic core is said to be 5 to 40 mm, and the length in the longitudinal direction is 230 to 300 mm. Note that the shape of the magnetic core 2 is not restricted to a cylindrical shape, and may be a prismatic shape. Also, an arrangement can be made where the magnetic core is divided into more than one in the longitudinal direction, and a space is provided between the cores, but in such a case, it is desirable that a space between the divided magnetic cores be configured as small as possible according to the last reason described. 2-3. excitation coil
[0080] Excitation coil 3 is formed by winding a copper wire material (single wire cable) whose diameter is 1 to 2 mm covered with heat resistant polyamide imide around magnetic core 2 in a spiral shape with approximately 10 turns to 100 turns. With the present embodiment, the number of turns of the excitation coil 3 is said to be 18 turns. The excitation coil 3 is wound around the magnetic core 2 in a direction orthogonal to the generative direction of the fixation film 1, and consequently, in the case of applying a high frequency current to the excitation coil, an alternating magnetic field can be generated. in a direction parallel to the generative direction of the fixation film 1.
[0081] Note that the excitation coil 3 does not necessarily have to be wound around the magnetic core 2. It is desirable that the excitation coil 3 has a spiral-shaped part, the spiral-shaped part is arranged inside of the cylindrical rotating element so that the spiral axis of its spiral-shaped part is parallel with the generative direction of the cylindrical rotating element, and the magnetic core is arranged in the spiral-shaped part. For example, an arrangement can be made where a coil in which the excitation coil 3 is wound in a spiral fashion is provided on the cylindrical rotating element, and the magnetic core 2 is arranged inside its coil.
[0082] Also, from the perspective of heat generation, when the spiral axis and the generating direction of the cylindrical rotating element are parallel, the thermal efficiency becomes the highest. However, in the case where the parallelism of the spiral axis against the generative direction of the cylindrical rotating element is shifted, “the amount of magnetic flux penetrating a parallel circuit” decreases slightly, and its thermal efficiency decreases, but in the case where the displacement amount is slope of several degrees, there is no practical problem. 2-4. Temperature Control Unit
[0083] Temperature sensing element 4 in Figure 1 is provided to detect the surface temperature of fixing film 1. With the present embodiment, a non-contact type thermistor is employed as the temperature sensing element 4. A high frequency converter 5 supplies a high frequency current to the excitation coil 3 via the electrical supply contact parts 3A and 3B. Note that the frequency of use of electromagnetic induction heating has been determined to be in the range of 20.05 kHz to 100 kHz by radio law enforcement regulations within the country of Japan. Furthermore, the frequency is preferably low for the cost component of the power supply, and consequently, with the first embodiment, the frequency modulation control is performed in a region from 21 kHz to 40 kHz around the lower limit of an available frequency band. A control circuit 6 controls the high-frequency converter 5 based on the temperature detected by the temperature sensing element 4. Thus, the control is carried out in such a way that the fixing film 1 is subjected to heating by electromagnetic induction, and the surface temperature becomes the predetermined target temperature (around 150 degrees centigrade to 200 degrees centigrade). (3) Principle of Heat Generation 3-1. Line shape of magnetic force and Induced Electromotive Force
[0084] First, the shape of a line of magnetic force will be described. Note that, first of all, the description will be made using a form of magnetic field in a solenoid coil with a common air core. Figure 4A is a schematic view of the air core solenoid coil 3 which serves as an excitation coil (in order to improve visibility, in Figures 4A and 4B the number of turns is decreased, the shape is simplified) , and a magnetic field. Solenoid coil 3 has a shape with limited length and also a gap Dd, and a high frequency current is applied to this coil. The direction of the magnetic force line is a moment when the current increases in the direction of the arrow I. With the magnetic force line, the larger parts pass through the center of solenoid coil 3, and are connected to the outer circumference while leaking from the space Dd. Figure 4B illustrates a magnetic flux density distribution on the central axis of solenoid X. As illustrated in a curve B1 of the graph, the magnetic flux density is highest at a central part 0, and is low at the end parts. of the solenoid. As a reason for the same, this is because there are leakages L1 and L2 of a line of magnetic force from the space Dd of the coil. The circumference magnetic field L2 near the coil is formed so as to surround the excitation coil 3. This circumference magnetic field L2 near the coil is said to pass through a path not suitable for effectively heating the element. cylindrical swivel.
[0085] Figure 5A is a diagram of correspondence between the shape of the coil and a magnetic field, in the case where a magnetic path is formed by inserting the magnetic core 2 in the center of the solenoid coil 3 with the same shape. As in Figures 4A and 4B, this is the moment when the current increases in the direction of arrow I. Magnetic core 2 serves as an internally configured element to induce a line of magnetic force generated in solenoid coil 3 to form a magnetic path. The magnetic core 2 according to the first embodiment has no roundness, but has an end part each in the longitudinal direction. Therefore, of the lines of magnetic force, most become an open magnetic path in a way that passes through the magnetic path at the center of the solenoid coil in a concentrated way, and the diffusion of the end parts in the longitudinal direction of the core. 2. As compared to Figure 4A, the leakage of lines of magnetic force in the spaces Dd of the coil decrease significantly, the lines of magnetic force emitted from both polarities become open magnetic paths in such a way that they are connected apart on the outer circumference (disconnected at the ends in the drawing). Figure 5B illustrates a magnetic flux density distribution on a central axis of solenoid X. With the magnetic flux density, as illustrated in a B2 curve in the graph, the attenuation of the magnetic flux density decreases at the end parts of the solenoid coil 3 compared to B1, and B2 and has an approximate shape of a trapezoid. 3-2. Induced Electromotive Force
[0086] The principle of heat generation follows Faraday's law. Faraday's law is "When changing a magnetic field inside a circuit, the induced electromotive force trying to apply current to the circuit occurs, and the induced electromotive force is proportional to the temporal change of a magnetic flux penetrating vertically in the circuit". Consider a case where a circuit S whose diameter is larger than the coil and the magnetic core is placed near an end part of the magnetic core 2 of the solenoid core 3 illustrated in Figure 6A, and a high-voltage alternating current frequency is applied to coil 3. In case a high frequency alternating current has been applied to it, an alternating magnetic field (magnetic field whose size and direction changes repeatedly over time) is formed around the solenoid coil. At that moment, the induced electromotive force generated in the circuit S is, according to the following Expression (1), proportional to the temporal change of a magnetic flux vertically penetrating the interior of the circuit S according to Faraday's law. Mathematical Formula 1
V: induced electromotive force N: number of coil turns ∆Ф /∆t: charge in a vertical magnetic flux entering the circuit in time ∆t
[0087] Specifically, in a state where a direct current is applied to the excitation coil to form a static magnetic field, in the case where many more vertical components of the magnetic force lines pass through the S circuit, the temporal change in the components vertical lines of magnetic force at the time of applying a high frequency alternating current to generate an alternating magnetic field also increases. As a result of this, the induced electromotive force to be generated also increases, and a current flows in a direction where the change in the magnetic flux of the same is cancelled. That is, as a result of having generated an alternating magnetic field, upon a flowing current, the change in a magnetic flux is cancelled, and forming a different magnetic force line shape at the time of formation of a static magnetic field. Furthermore, the higher the frequency of the alternating current (ie, the lower the Dt), this induced electromotive force V is apt to increase. Consequently, the electromotive force that can be generated with a predetermined amount of magnetic fluxes differs significantly between a case where an alternating current with a low frequency of 50 to 60 Hz is applied to the excitation coil, and a case where an alternating current with a low frequency of 50 to 60 Hz is applied to the excitation coil. alternating current with a high frequency of 21 of 100 kHz is applied to the excitation coil. By changing the frequency of an alternating current to a high frequency, high electromotive force can be generated even with some magnetic fluxes. Thus, by changing the frequency of alternating current to a high frequency, the large amount of heat can be generated with a magnetic core whose cross-sectional area is small, and consequently, this is advantageous in case of trying to generate the large amount of heat. amount of load in a small fixture. This is similar to a case where a transformer can be reduced in size by increasing the frequency of an alternating current. For example, with a transformer to be used for a low frequency band (50 to 60 Hz), a magnetic flux F has to be increased by an equivalent increase for Dt, and the cross-sectional area of the magnetic core has to be increased. On the other hand, with a transformer being used for a high frequency band (kHz), the magnetic flux F can be decreased by an equivalent decrease to Dt, and the cross-sectional area of the magnetic core can be projected small.
[0088] As a conclusion of the above description, a high frequency band from 21 to 100 kHz is used as the frequency of an alternating current, and, consequently, the reduction in the size of an imaging apparatus can be realized. by reducing the cross-sectional area of the magnetic core.
[0089] In order to generate electromotive force induced in circuit S with high efficiency by an alternating magnetic field, a state has to be designed in which many more vertical components of lines of magnetic force pass through circuit S. However, with a alternating magnetic field, the influence of a demagnetizing field at the time of the induced electromotive force being generated in the coil, and so on, has to be taken into account, a phenomenon becomes complicated. The fixture according to the present embodiment will be described later, but in order to design the fixture according to the present embodiment, an argument is advanced with the shape of lines of magnetic force in a state of a static magnetic field. where no induced electromotive force was generated, and consequently the design can be advanced with a simpler physical model. This means that the shape of the lines of magnetic force in a static magnetic field is optimized, and a clamping device can be designed where the induced electromotive force is generated with high efficiency in an alternating magnetic field.
[0090] Figure 6B illustrates a distribution of magnetic flux density on the central axis of solenoid X. In the case of considering a case where a direct current was applied to the coil in order to form a static magnetic field (magnetic field without fluctuations in time), compared to a magnetic flux when arranging the circuit S in a position X1, when the circuit S is arranged in a position X2, a magnetic flux that penetrates vertically in the circuit S increases as illustrated in B2. At position X2, almost all of the lines of magnetic force contained by magnetic core 2 are housed in circuit S, and with a stable M region in a more positive direction on the X axis than at position X2, a magnetic flux that vertically penetrates in the circuit is saturated to constantly become the maximum. The same can be applied to the end part on the opposite side, as illustrated in a magnetic flux distribution in Figure 7B, with a stable M region from position X2 to X3 in the end part on the opposite side, the flux density that penetrates vertically into the circuit S is saturated and stabilized. As illustrated in Figure 7A, this stable M region exists within a region including magnetic core 2.
[0091] As illustrated in Figure 8A, with respect to the configuration of lines of magnetic force (magnetic flux) in the present embodiment, in case a static magnetic field has formed, the cylindrical rotating element 1a is covered with a region from X2 to X3 . Then the shape of the magnetic force lines is designed in which the magnetic force lines pass over the outside of the cylindrical rotating element from one end (NP magnetic polarity) to the other end (SP magnetic polarity) of the magnetic core 2. In then an image on a recording material is heated using the stable region M. Consequently, with the first embodiment, at least the length in the longitudinal direction of the magnetic core 2 to form a magnetic path has to be configured so to be greater than the maximum image heating region ZL of the recording material P. As an even more preferred configuration, it is desirable that the lengths in the longitudinal directions of both the magnetic core 2 and the excitation coil 3 are configured so that so as to be greater than the ZL image maximum heating region. Thus, the toner image on the recording material P can be heated evenly to the end parts. Furthermore, the length in the longitudinal direction of the cylindrical rotating element 1a has to be set to be greater than the maximum image heating region ZL. With the present embodiment, in case you have formed a solenoid magnetic field illustrated in Figure 8A, it is important that the two magnetic polarities NP and SP project on an outer side than the maximum image heating region ZL . Thus, regular heat can be generated in a range of the ZL.
[0092] Note that the maximum transport region of a recording material can be used instead of the maximum image heating region.
[0093] With the present embodiment, both end parts in the longitudinal direction of the magnetic core 2 can project outwards from an end face in the generative direction of the fixing film 1. Thus, the amount of heat in the region whole in the generative direction of the fixation film 1 can be stabilized.
[0094] An electromagnetic induction heating fixture according to the related technique was designed with technical thought in such a way that a line of magnetic force is injected into the material of a cylindrical rotating element. On the other hand, the electromagnetic induction heating system according to the first embodiment heats the entire region of the cylindrical rotating element, in a state in which a magnetic flux that penetrates vertically into the circuit S becomes the maximum, i.e., it has been designed with techniques such that the lines of magnetic force pass the outside of the cylindrical rotating element.
[0095] Next, three examples of a form of magnetic force line unsuitable for a purpose of the present embodiment will be illustrated. Figure 9A illustrates an example where the lines of magnetic force pass through the interior of the rotating cylindrical element (region between the rotating cylindrical element and the magnetic core). In this case, with the lines of magnetic force passing through the inner side of the cylindrical rotating element, the lines of magnetic force going to the left and the lines of magnetic force going to the right in the drawing are mixed, and consequently, they cancel, and according to Fara-day's law, the value of integration of F decreases, the heat efficiency decreases, and consequently that is undesirable. Such a magnetic force line shape is caused in the case where the cross-sectional area of the magnetic core is small, in the case where the relative permeability of the magnetic core is small, in the case where the magnetic core is split in the longitudinal direction to form a large space, and in the case where the diameter of the cylindrical rotating element is large. Figure 9B illustrates an example where lines of magnetic force pass through the interior of the cylindrical rotating member material. This state is readily caused in the case where the material of the cylindrical rotating element is a material with high relative permeability, such as nickel, iron, or the like.
[0096] As a conclusion of the above description, a form of magnetic force line unsuitable for a purpose of the present embodiment is formed in the following cases from (I) to (V), and that is a fixture according to the technique related in which heat is generated with Joule heat due to eddy current loss, which occurs in the material of the cylindrical rotating element. (I) The relative permeability of the material of the cylindrical rotating element is large. (II) The cross-sectional area of the cylindrical rotating element is large. (III) The cross-sectional area of the magnetic core is small. (IV) The relative permeability of the magnetic core is small. (V) The magnetic core is split in the longitudinal direction to form a large space.
[0097] Figure 9C is a case where the magnetic core is split into a plurality in the longitudinal direction, and a magnetic polarity is formed at a location MP other than both the NP and SP end parts of the magnetic core. In order to achieve a purpose of the present embodiment, it is desirable to form a magnetic path so as to take only two of NP and SP as magnetic polarities, and it is not desirable to split the magnetic core into two or more in the longitudinal direction to form a magnetic polarity. PM According to a ratio described later in 3-3, there may be a case where the magnetic resistance of the entire magnetic core is increased to prevent a magnetic path from being formed, and a case where the amount of heat in the vicinity of the MP magnetic polarity decreases to prevent an image from being evenly heated. In the case of splitting the magnetic core, a range (will be described later in 3-6) is restricted where the magnetic resistance is reduced and the permeance is kept large so that the magnetic core sufficiently serves as a magnetic path. 3-3. Magnetic Circuit and Permeance
[0098] Next, description will be made regarding a specific design guide to achieve the principle of heat generation described in 3-2 which is an essential feature of the present embodiment. For this purpose, the ease of passage of magnetism in the generative direction of the cylindrical rotating element of the fixture components has to be expressed as a form factor. The form factor of the same uses the “permeance” of “a model of magnetic circuit in a static magnetic field”. Firstly, the description will be made in relation to the way of thinking for a common magnetic circuit. A closed circuit of a magnetic path where the lines of magnetic force mainly pass through will be called a magnetic circuit versus an electrical circuit. At the time of calculating a magnetic flux in a magnetic circuit, this can be performed according to the calculation of a current in an electrical circuit. The basic formula of a magnetic circuit is the same as with electrical circuits related to Ohm's law, and all lines of magnetic force are said to be F, the electromotive force is V, and the magnetic resistance is R, these three elements have a ratio of All lines of magnetic force Ф = electromotive force V / magnetic resistance R ... (2)
[0099] (Consequently, a current in an electrical circuit corresponds to all the lines of magnetic force F in a magnetic circuit, the electromotive force in an electrical circuit corresponds to the electromotive force V in a magnetic circuit, and the electrical resistance in a circuit electrical resistance corresponds to the magnetic resistance in a magnetic circuit). However, in order to comprehensively describe the principle, the description will be made using the permeance P, which is an inverse number of the magnetic resistance R. Consequently, Expression (2) above is replaced with All lines of magnetic force Ф = electromotive force V x permeance P ... (3)
[0100] When assuming that the length of a magnetic path is B, the cross-sectional area of the magnetic path is S, and the permeability of the magnetic path is m, this permeance P is represented with Permeance P = permeability µ x area transverse of magnetic path S / length of magnetic path B... (4)
[0101] The permeance P indicates that the shorter the length of the magnetic path B, and the greater the cross-sectional area of the magnetic path S and the permeability m, the greater the permeance P, and many more lines of magnetic force F are formed in a part where the permeance P is large.
[0102] As illustrated in Figures 8A, the design is made so that most lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core in a static magnetic field pass over the outside of the rotating cylindrical element. to go back to the other end of the magnetic core. At the time of its design, it is desirable that the fixture is considered as a magnetic circuit, and the permeance of the magnetic core 2 is set sufficiently large, and also, the permeance of the cylindrical rotating element and the inner side of the cylindrical rotating element is configured small enough.
[0103] In Figures 10A and 10B, the cylindrical rotating element (electro-conductive layer) will be called a cylindrical body. Figure 10A is a structure in which the magnetic core 2, where the radius is a1 m and the length is B m and the relative permeability is m1, and a solenoid of limited length where the excitation coil 3 whose number of turns is N times are arranged inside of the cylindrical body 1a. Here, the cylindrical body is a conductor whose length is B m, the inner radius of the cylindrical body is a2 m, and the outer radius of the cylindrical body is a3 m, and the relative permeability is m2. The vacuum permeability on the inside and outside of the cylindrical body is said to be m0 H/m. By applying a current I A to the solenoid coil, a magnetic flux 8 to be generated per unit length of an optional position of the magnetic core is jc(x).
[0104] Figure 10B is an enlarged view of a cross section perpendicular to the longitudinal direction of magnetic core 2. The arrows in the drawing represent, when applying a current I to the solenoid coil, the air inside the magnetic core, the air inside and outside of the cylindrical body, and the lines of magnetic force parallel to the longitudinal direction of the magnetic core passing through the cylindrical body. A magnetic flux that passes through the magnetic core is jc (= jc(x)), a magnetic flux that passes through the air on the inside of the cylindrical body is ja_in, a magnetic flux that passes through the cylindrical body is jcy , and a magnetic flux passing through the air on the outside of the cylindrical body is ja_out.
[0105] Figure 11A illustrates a magnetic equivalent circuit in space including the core, coil, and cylindrical body per unit length illustrated in Figure 10B. The electromotive force to be generated by the magnetic flux jc of the magnetic core is Vm, the permeance of the magnetic core is Pc, the permeance inside the air on the inner side of the cylindrical body is Pa_in, the permeance inside the cylindrical body is Pcy, and the permeance of the air on the outside of the cylindrical body is Pa_out. When the permeance Pc of the magnetic core is sufficiently large, compared to the permeance Pa_in inside the cylindrical body or the permeance Pcy of the cylindrical body, the following relationship holds.

[0106] That is, it means that a magnetic flux that passes through the interior of the magnetic core necessarily passes through one of ja_in, jcy, and ja_out and returns to the magnetic core.

[0107] Consequently, when replacing (6) to (9) with (5), Expression (5) becomes as follows.

[0108] According to Figure 10B, if the cross-sectional area of the magnetic coil is said to be Sc, the cross-sectional area of the air inside this cylindrical body is Sa_in, and the cross-sectional area of the cylindrical body is Scy, the permeance per unit length of each region can be represented with “permeability x cross-sectional area” as follows, and its unit is Hm.

[0109] Furthermore, Pc - Pa_in - Pcy - Pa_out = 0, and consequently, the permeance inside the air outside the cylindrical body can be represented as follows.

[0110] A magnetic flux passing through each region is, as illustrated in Expression (5) to Expression (10), proportional to the permeance of each region. When employing Expressions (5) to (10), a ratio of a magnetic flux passing through each region can be calculated as with Table 1 described later. Note that in the case where a material other than air exists in the hollow part of the cylindrical body as well, the permeance can be obtained from a cross-sectional area and the permeability of that in the same method as with the air inside the cylindrical body . The description will be made later regarding how to calculate the permeance in this case.
[0111] With the present embodiment, as "a coefficient of shape to express the ease of passage of magnetism to the longitudinal direction of the cylindrical rotating element", "permeance per unit length" is used. Table 1 calculates, with the configuration of the present embodiment, the permeance per unit length from the cross-sectional area and the permeability of the magnetic core, film guide (narrowing part forming element), the air inside the cylindrical body , and the cylindrical body using Expressions (5) to (10). Finally, the air permeance outside the cylindrical body is calculated using Expression (14). With the present calculation, all “elements that can be included in the cylindrical body and serve as a magnetic path” are taken into account. The present calculation indicates what percentage a permeance ratio of each part is with the magnetic core permeance value as 100%. Accordingly, with respect to which part a magnetic path is readily formed, and through which part a magnetic flux passes, digitization can be done using a magnetic circuit.
[0112] Magnetic resistance R (inverse permeance number P) can be used instead of permeance. Note that in the case of arguing using magnetic resistance, the magnetic resistance is simply an inverse number of permeance, and consequently, the magnetic resistance R per unit length can be represented with “1/(permeability x cross-sectional area)”, and its unit is “1/(Hm)”.
[0113] Then details (material and numerical values) of setting the first modality to be used for scanning will be listed.
[0114] Magnetic core 2: ferrite (relative permeability 1800), diameter 14 mm (cross-sectional area 1.5 x 10-4 m2)
[0115] Film guide: PPS (relative permeability 1), cross-sectional area 1.0 x 10-4 m2
[0116] Cylindrical rotating element (electroconductive layer) 1a: aluminum (relative permeability 1), diameter 24 mm, thickness 20 mm (cross-sectional area 1.5 x 10-6 m2)
[0117] The elastic layer 1b of the fixing film, and the surface layer 1c of the fixing film are on an outer side than the cylindrical rotating element (electroconductive layer) 1a which is an exothermic layer, and also do not contribute for heat generation. Consequently, the permeance (or magnetic resistance) does not have to be calculated, and with the present magnetic circuit model, the elastic layer 1b of the fixing film, and the surface layer 1c of the fixing film can be manipulated by being included in the “air outside the cylindrical body”.
[0118] The "permeance and magnetic resistance per unit length" of the fixture components calculated from the dimensions above and the relative permeability will be summarized in the following Table 1. Table 1 Magnetic Permeance in the First Mode

[0119] Regarding the "permeance per unit of length", the description will be made with respect to the correspondence relationships between a magnetic equivalent circuit diagram in Figure 11A and actual numerical values. The permeance Pc per unit length of the magnetic core is represented as follows (Table 1). Pc = 3.5 x 10-7 H-m
[0120] The Pa_in permeance per unit length of a region between the electroconductive layer and the magnetic core is composition with permeance per unit length of the film guide and the permeance per unit length of the air inside the cylindrical body, and consequently, represented as follows (Table 1).

[0121] The Pcy permeance per unit length of the electroconductive layer is a cylindrical body described in Table 1, and is represented as follows.

[0122] Pa_out is the air outside the cylindrical body described in Table 1, and is represented as follows.

[0123] Next, the description will be made with respect to a case in which the magnetic resistance is an inverse number of the permeance. The magnetic resistance per unit length of the magnetic core is as follows.

[0124] The magnetic resistance of a region between the electroconductive layer and the magnetic core is as follows.

[0125] Note that, in the case of directly calculating the magnetic resistance from the reluctance Rf of the film guide = 8.0 x 109 1/(Hm) and the reluctance Ra of the air inside the cylindrical body = 4.0 x 109 1/(Hm), the combined reluctance expressions of parallel circuits have to be used.

[0126] It is the cylindrical body described in Table 1 that corresponds to Rcy, and Rcy = 5.3 x 1011 H-m. Also, the cross-sectional area of air in a region between the cylindrical body and the magnetic core is calculated by subtracting the cross-sectional area of the magnetic core and the cross-sectional area of the film guide from the cross-sectional area of the hollow part whose diameter is 24 mm. . In general, a pattern of a permeance value at the time of using the present embodiment as a fixture is substantially as follows.
[0127] Regarding the magnetic core, in the case of using sintered ferrite, the relative permeability is substantially around 500 to 10000, and the cross section becomes approximately 5 mm to 20 mm. Consequently, the permeance per unit length of the magnetic core becomes 1.2 x 10-8 to 3.9 x 10-6 km. In case of employing another ferromagnetic, the relative permeability can be selected substantially around 100 to 10000.
[0128] In the case of employing a resin as the film guide material, the relative permeability is substantially 1.0, and the cross-sectional area becomes approximately 10 mm2 to 200 mm2. Consequently, the permeance per unit length becomes 1.3 x 10-11 to 2.5 x 10-10 km.
[0129] With respect to the air inside the cylindrical body, the relative air permeability is substantially 1, and an approximate cross-sectional area becomes the difference between the cross-sectional area of the cylindrical rotating element and the cross-sectional area of the core, and consequently becomes a cross-sectional area equivalent to 10 mm to 50 mm. Consequently, the permeance per unit length becomes 1.0 x 10-11 to 1.0 x 10-10 km. The air inside the cylindrical body mentioned here is a region between the cylindrical rotating element (electromagnetic layer) and the magnetic core.
[0130] Regarding the cylindrical rotating element (electromagnetic layer), in order to reduce the heating time, it is desirable that the thermal capacity is lower. Consequently, it is desirable for the thickness to be 1 to 50 mm, and the diameter to be approximately 10 to 100 mm. The permeance per unit length in case of employing nickel (relative permeability 600) which is a magnetic material as measured becomes 4.7 x 10-12 to 1.2 x 10-9 Km. The permeance per unit length in case of employing a non-magnetic material as the material becomes 8.0 x 10-15 to 2.0 x 10-12 km. Above is an approximate "permeance per unit length" range of the fixture in accordance with the present embodiment.
[0131] Here, in the case of replacing the above permeance values with a magnetic resistance value, the results of this become as follows. The magnetic resistance range of each of the magnetic core, the film guide, and the air inside the cylindrical body is 2.5 x 105 to 8.1 x 107 1/(H^m), 4.0 x 109 at 8.0 x 10 10 1/(Hm), and 1.0 x 10 8 at 1.0 x 10 10 1/(Hm).
[0132] With respect to the cylindrical rotating element, the magnetic resistance per unit length in case of employing nickel (relative permeability 600) which is a magnetic material as the material becomes 8.3 x 108 to 2.1 x 1011 1/ (Km), and the magnetic resistance per unit length in case of employing a non-magnetic material as the material becomes 5.0 x 1011 to 1.3 x 1014 1/(Hm).
[0133] Above is an approximate "magnetic resistance per unit length" range of the fixture in accordance with the present embodiment.
[0134] Next, the magnetic equivalent circuit will be described with respect to the “magnetic flux ratio” in Table 1 and Figure 11B. With the present embodiment, in a magnetic circuit model in a static magnetic field, a path where 100% lines of magnetic force emitted from one end of the magnetic core passing through the interior of the magnetic core has the following content. Of 100% of the lines of magnetic force emitted from one end of the magnetic core passing through the magnetic core, 0.0% passes through the film guide, 0.1% passes through the air inside the cylindrical body, 0.0 % passes through the barrel, and 99.9% passes through the air outside the barrel. Then this state will be represented as “ratio of magnetic flux outside the cylindrical body: 99.9%”. Note that, although a ratio is described later, in order to achieve a purpose of the present embodiment, it is desirable that the value of “a ratio of lines of magnetic force passing over the exterior of the cylindrical element, in a circuit model magnetic field in a static magnetic field” approaches the maximum of 100%.
[0135] “A ratio of lines of magnetic force passing over the outside of the cylindrical element” is, at the time of applying a direct current to the excitation coil to form a static magnetic field, of lines of magnetic force passing through the interior of the magnetic core in the generative direction of the film and emitted from one end in the longitudinal direction of the magnetic core, a relationship of lines of magnetic force passing over the outside of the rotating cylindrical element and returning to the other end of the magnetic core.
[0136] When representing with parameters described in Expressions (5) to (10), “a ratio of lines of magnetic force passing over the outside of the cylindrical element” is a ratio of Pa_out against Pc (= Pa_out / Pc).
[0137] In order to create a configuration having a high “ratio of lines of magnetic force outside the cylindrical body”, specifically, the following design techniques are desirable.
[0138] Technique 1: Increase in magnetic core permeance (increase in the cross-sectional area of the magnetic core, increase in the relative permeability of the material).
[0139] Technique 2: Reduction of permeance within the cylindrical body (decreased cross-sectional area of the air part).
[0140] Technique 3: Prevent an element having high permeance from being disposed within the cylindrical body, such as iron or similar.
[0141] Technique 4: Reduce the permeance of the cylindrical body (reduce the cross-sectional area of the cylindrical body, reduce the relative permeability of the material to be used for the cylindrical body).
[0142] According to technique 4, it is desirable that the material of the cylindrical body has low relative permeability m. At the time of employing a material having high relative permeability m as the cylindrical body, the cross-sectional area of the cylindrical body has to be reduced as much as possible. This is the opposite of a fixture according to the related technique where the greater the cross-sectional area of the cylindrical body, the more the number of lines of magnetic force penetrating the cylindrical body increases, and the higher the thermal efficiency becomes. Also, although it is desirable to prevent an element having great permeability from being disposed within the cylindrical body, in the case where iron or the like has no choice but to be disposed, "a ratio of lines of magnetic force passing over the exterior of the cylindrical element” has to be controlled by reducing the cross-sectional area, or similar.
[0143] Note that there may also be a case where the magnetic core is split into two or more in the longitudinal direction, and a space is provided between the split magnetic cores. In such a case, in the case where that space is filled with air or a medium having less magnetic permeability than the relative permeability of the magnetic core such as a medium whose relative permeability is considered to be 1.0, the magnetic resistance of the entire magnetic core increases to decrease capacity forming magnetic path. Consequently, in order to achieve the present embodiment, the magnetic core spaces have to be severely managed. A method to calculate the magnetic core permeance becomes complicated. Next, the description will be made with respect to a method for calculating the permeance of the entire magnetic core in the case of dividing the magnetic core into two or more and arranging these with an equal interval by placing a space or non-magnetic sheet-shaped material between they. In this case, it is necessary to derive the magnetic resistance from the totality in the longitudinal direction, to obtain the magnetic resistance per unit of length by dividing the magnetic resistance derived by the unit of length, and to obtain the permeance per unit of length by taking an inverse number of that number. .
[0144] First, a longitudinal configuration diagram of the magnetic core is illustrated in Figure 12. With magnetic cores c1 to c10, the cross-sectional area is Sc, the permeability is mc, and the longitudinal dimension by a divided magnetic core is Lc, and with spaces g1 to g9, the cross-sectional area is Sg, the permeability is mg, and the longitudinal dimension through a space is Lg. At that moment, the magnetic resistance Rm_all of the longitudinal totality is given by the following expressions.

[0145] In the case of the present configuration, the shape and material of the magnetic core and the width of the space are regular, and consequently, a sum of the addition of Rm_c is said to be SRm_c, and a sum of the addition of Rm_g is SRm_g , Expression (15) is represented as follows.

[0146] It is said that the longitudinal dimension of the magnetic core is Lc, the permeability is mc, the cross-sectional area is Sc, the longitudinal dimension of space is Lg, the permeability is mg, and the cross-sectional area is Sg,

[0147] These are replaced by Expression (16), and consequently, the magnetic resistance Rm_all of the entire longitudinal dimension becomes

[0148] If an addition total of Lc is said to be SLc, and a total addition of Lg is said to be SLg, the magnetic resistance Rm per unit length becomes

[0149] Permeance Pm per unit length is obtained as follows.
ƩLc: total lengths of magnetic cores divided µc: permeability of magnetic core Sc: cross-sectional area of magnetic core ƩLg: total lengths of spaces µg: permeability of space Sg: cross-sectional area of space
[0150] According to Expression (21), increasing the space Lg leads to an increase in the magnetic resistance of the magnetic core (deterioration in permeance). In order to configure the fixture according to the present embodiment, the design is desirable in order to reduce the magnetic resistance of the magnetic core (so as to increase the permeance) from the perspective of heat generation, and consequently , it is therefore not desirable to provide spaces. However, there may be a case where in order to prevent the magnetic core from being readily broken, the magnetic core is split into two or more to provide spaces. In this case, the design is carried out in such a way as to reduce the Lg gaps as much as possible (preferably approximately 50 mm or less), and as well as not to deviate from the design conditions for permeance and magnetic resistance described later, being a purpose of the present invention can be achieved.
[0151] 3-4. Current in the direction of the circumference inside the cylindrical rotating element
[0152] In Figure 8A, the magnetic core 2, the excitation coil 3, and the rotating cylindrical element (electroconductive layer) 1a are arranged concentrically from the center, and when a current increases in the direction of the arrow I inside the excitation 3, eight lines of magnetic force pass through magnetic core 2 in a conceptual diagram.
[0153] Figure 13A illustrates a conceptual diagram of a transverse configuration at position 0 in Figure 8A. Lines of magnetic force Bin passing through the magnetic path are illustrated with arrows (eight x marks) towards the depth direction in the drawing. The Bout arrows (eight dot marks) towards the front side in the drawing represent the lines of magnetic force returning out of the magnetic path at the time of forming a static magnetic field. Accordingly, the number of lines of magnetic force Bin in the depth direction in the drawing inside the cylindrical rotating element 1a is eight, and the number of lines of magnetic force Bout returning to the front side of the drawing outside the rotating cylindrical element 1a is also eight. At a time when a current increases in the direction of the arrow I inside the excitation coil 3, the lines of magnetic force are formed as an arrow (an x mark inside a circle) in the direction of depth in the drawing within the magnetic path. In case an alternating magnetic field has actually been formed, the induced electromotive force is applied to the entire region in the direction of the circumference of the cylindrical rotating element 1a in order to cancel a line of magnetic force to be formed in this way, and a current flows. in a direction of arrow J. When a current flows into the rotating cylindrical element 1a, the rotating cylindrical element 1a is metal, and consequently, Joule heating is caused due to electrical resistance.
[0154] It is an important feature of the present embodiment that this current J flows in the direction of circulation of the cylindrical rotating element 1a. With the configuration of the present embodiment, the lines of magnetic force Bin passing through the interior of the magnetic core in a static magnetic field pass through the hollow part of the rotating cylindrical element 1a, and the lines of magnetic force Bout emitted from one end of the magnetic core and returning to the other end of the magnetic core pass over the outside of the cylindrical rotating element 1a. This is because, in an alternating magnetic field, the current in the direction of the circumference becomes dominant within the cylindrical rotating element 1a, an eddy current E// where the lines of magnetic force as illustrated in Figure 31 are generated penetrating the interior of the material. of the electroconductive layer is prevented from being generated. Note that then, in order to distinguish from “eddy current” (later described in comparative examples 3 and 4) substantially used for description of induction heating, a current to flow regularly to the cylindrical rotating element in the direction of the arrow J (or its inverse direction) in the configuration of the present embodiment will be called “current in the direction of the circumference”. The induced electromotive force according to Faraday's law was generated in the direction of circulation of the rotating cylindrical element 1a, and consequently, this current in the direction of the circumference J regularly flows to the rotating cylindrical element 1a. The magnetic field lines repeat the generation/elimination and change of direction in sync with the high frequency current, and the Joule heating is caused according to the reluctance value of the entire region in the direction of the thickness of the material. cylindrical rotating element. Figure 13B is a longitudinal perspective view illustrating the lines of magnetic force Bin to pass through the magnetic path of the magnetic core, the magnetic field lines Bout to return from outside the magnetic path, and the direction of current towards the circumference J flowing into the cylindrical rotating element 1a.
[0155] It is another advantage that there are some restrictions regarding the gap in the radial direction of the rotating cylindrical element between the rotating cylindrical element and the excitation coil 3. Here, Figure 34 illustrates the longitudinal cross section of the clamping device where no coil magnet is provided, and the excitation coil 3 is provided having a spiral part whose spiral axis is parallel with the generating direction of the cylindrical body 1d to the hollow part of the cylindrical body 1a. With such a fixture, when the magnetic flux L2 generated in the vicinity of the excitation coil 3 penetrates the rotating cylindrical element 1a, an eddy current is generated in the rotating cylindrical element 1a, and heat is generated. Consequently, in order to have L2 contribute to the heating, the design has to be executed so as to reduce a gap Ddc between the excitation coil 3 and the rotating cylindrical element 1d.
[0156] However, in the case where flexibility was given to the cylindrical rotating element by reducing the thickness of the cylindrical rotating element 1d, the fixing film 1 is deformed, and consequently, it is difficult to maintain the Ddc gap between the excitation coil 3 and the 1d cylindrical rotating element over the entire circumference with high precision.
[0157] On the other hand, with the clamping device according to the present embodiment, the current in the direction of the circumference is proportional to the temporal change of lines of magnetic force penetrating the hollow part of the cylindrical rotating element 1a in the generative direction of the rotating element cylindrical 1a. In that case, even when the positional relationships of the excitation coil, magnetic core, and cylindrical rotating element 1a are shifted several millimeters to tens of millimeters, the electromotive force acting on the rotating cylindrical element 1a does not readily fluctuate. Then, the fastening device according to the present embodiment features in an application to heat the cylindrical rotating element having flexibility such as a film. Consequently, as illustrated in Figure 3, even when the rotating cylindrical element 1a is defined elliptically, the current in the circumferential direction can be effectively applied to the rotating cylindrical element 1a. Furthermore, the transverse shapes of the magnetic core 2 and the excitation coil 3 can be any shape (square, pentagon, etc.), and consequently, the design flexibility is also high. 3-5. Energy Conversion Efficiency
[0158] At the time of heating the cylindrical rotating element (electro-conductive layer) of the fixing film, a high frequency alternating current is applied to the excitation coil to form an alternating magnetic field. This alternating magnetic field induces current into the rotating cylindrical element. As a physical model, this is very similar to the magnetic coupling of a transformer. So, when considering energy conversion efficiency, a transformer magnetic coupling equivalent circuit can be employed. According to its alternating magnetic field, the excitation coil and the rotating cylindrical element are magnetically coupled, the energy applied to the excitation coil is propagated to the rotating cylindrical element. The "energy conversion efficiency" mentioned here is a ratio between the energy to be supplied to the excitation coil serving as a magnetic field generator, and the energy to be consumed by the cylindrical rotating element, and in the case of the present embodiment, is a ratio between the energy to be supplied to a high frequency converter 5 to the excitation coil 3 illustrated in Figure 1, and the energy to be consumed as the heat generated in the cylindrical rotating element 1a. This energy conversion efficiency can be represented with the following expression.
[0159] Energy conversion efficiency = energy to be consumed as heat in the cylindrical rotating element / energy to be supplied to the excitation coil
[0160] Examples of the energy being consumed by other than the cylindrical rotating element after supplying the excitation coil include loss due to the reluctance of the excitation coil, and loss due to the magnetic properties of the magnetic core material.
[0161] Figures 14A and 14B illustrate explanatory diagrams regarding circuit efficiency. In Figure 14A, 1a denotes a rotating cylindrical element, 2 denotes a magnetic core, and 3 denotes an excitation coil, and current in the circumferential direction J flows into the rotating cylindrical element 1a. Figure 14B is an equivalent circuit of the fastener illustrated in Figure 14A.
[0162] R1 denotes the amount of loss of the excitation coil and the magnetic core, L1 denotes the inductance of the excitation coil circulated around the magnetic core, M denotes the mutual inductance between the winding wire and the cylindrical rotating element, L2 denotes the inductance of the rotating cylindrical element, and R2 denotes the resistance of the rotating cylindrical element. An equivalent circuit when removing the cylindrical rotating element is illustrated in Figure 15A. When measuring the resistance R1 from both ends of the excitation coil, and the equivalent inductance L1 using a device such as an impedance analyzer or LCR meter, the impedance ZA as seen from both ends of the excitation coil excitation is represented as

[0163] A current flowing into this circuit is lost by R1. That is, R1 represents the loss due to the magnetic coil and core.
[0164] An equivalent circuit when loading the cylindrical rotating element is illustrated in Figure i5B. In the case of resistance Rx and Lx currently being measured, the following relational expression can be obtained by performing the equivalent conversion as illustrated in Figure i5C. Mathematical Formula 2
Mathematical Formula 3
Mathematical Formula 4

[0165] where M represents the mutual inductance between the excitation coil and the cylindrical rotating element.
[0166] As illustrated in Figure 15C, when a current flowing into R1 is I1, and a current flowing into R2 is I2, Mathematical Formula 5

[0167] remains, and consequently, Mathematical Formula 6
remains.
[0168] Efficiency is represented with the energy consumption of resistor R2 / (energy consumption of resistor R1 + energy consumption of resistor R2), and consequently, Mathematical Formula 7

[0169] If the resistance R1 is measured before charging the cylindrical rotating element, and the resistance Rx after charging the cylindrical rotating element, the energy conversion efficiency can be obtained which indicates the energy supplied to the excitation coil , how much energy is consumed as heat to be generated in the cylindrical rotating element. Note that with the configuration of the first modality, the 4294A Impedance Analyzer manufactured by Agilent Technologies Inc. was used to measure the efficiency of energy conversion. First, in a state in which there is no rotating cylindrical element, resistance R1 was measured from both ends of a winding wire, then, in a state in which the magnetic core was inserted into the rotating cylindrical element, resistance Rx was measured from both ends of the winding wire. Consequently, R1 = 103 mW and Rx = 2.2W hold, the energy conversion efficiency at this time can be obtained as 95.3% by Expression (27). Then, the performance of the fixture with electromagnetic induction heating system will be evaluated using this energy conversion efficiency. 3-6. Conditions for the “Magnetic Flux Ratio outside the Cylindrical Body”
[0170] With the fixture according to the present embodiment, there is a correlation between a ratio of lines of magnetic force passing through the outside of the cylindrical rotating element in a static magnetic field, and the energy conversion efficiency supplied to the coil. existing to be propagated to the rotating cylindrical element in an alternating magnetic field (energy conversion efficiency). The more the ratio of lines of magnetic force passing over the outside of the cylindrical body increases, the greater the efficiency of energy conversion. One reason for this depends on the same principle as in the case of a transform where when the number of leakage lines of magnetic force is sufficiently small, and the number of lines of magnetic force passing through the primary turns and the number of lines of magnetic force passing through of the secondary turns are equal, the energy conversion efficiency becomes high. That is, the closer the number of lines of magnetic force passing through the interior of the magnetic core, and the number of lines of magnetic force passing over the exterior of the cylindrical rotating element, the higher the efficiency of converting energy into a current in the circle direction becomes. This means that a relationship to the lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core and returning to the other end (lines of magnetic force having the reverse direction of the lines of magnetic force passing through the interior of the core magnetic) canceling the lines of magnetic force passing through the hollow part of the cylindrical rotating element and passing through the interior of the magnetic core is small. That is, as illustrated in a magnetic equivalent circuit in Figure 11B, the lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core and returning to the other end pass over the outside of the cylindrical rotating element (air outside the cylindrical body). Accordingly, the essential feature of the present embodiment is to effectively induce a high frequency current applied to the excitation coil as a current in the circumferential direction within the cylindrical rotating element increasing a ratio of lines of magnetic force outside the cylindrical body. Specific examples are included to decrease the lines of magnetic force passing through the film guide, the air within the barrel, and the barrel.
[0171] Figure 16 is a diagram of an experimental apparatus to be used for energy conversion efficiency measurement experiments. A 1S metal sheet is an aluminum sheet where the area is 230 mm x 600 mm, and the thickness is 20 mm, which forms the same electroconductive path as the cylindrical rotating element being rounded into a cylindrical shape so as to encircle the magnetic core. 2 and the excitation coil 3 and being electrically driven on a part of thick line 1ST. Magnetic core 2 is e ferrite where the relative permeability is 1800, and the saturation magnetic flux density is 500 mT, and has a cylindrical shape where the cross-sectional area is 26 mm2, and the length B is 230 mm. The magnetic core 2 is disposed substantially in the center of the aluminum foil cylinder 1S using a clamping unit which is not illustrated, a magnetic path is formed inside the cylinder penetrating the hollow part of the cylinder with length B = 230 mm. The excitation coil 3 is formed by winding the magnetic core 2 with 250 turns in a spiral shape in the hollow part of the cylinder.
[0172] Here, when the end part of the sheet metal 1S is taken out in a direction of the arrow 1SZ, the diameter 1SD of the cylinder can be reduced. The energy conversion efficiency was measured using this experimental apparatus, while changing the cylinder diameter 1SD from 191 mm to 18 mm. Note that the results of calculating a ratio of lines of magnetic force outside the cylindrical body at the moment of 1SD = 191 mm are illustrated in the following Table 2, and the results of calculating a ratio of lines of force outside the cylindrical body at the moment of 1SD = 18 mm are illustrated in the following Table 3. Table 2 Relation of Lines of Magnetic Force Outside the Cylindrical Body when the Diameter of Cylinder 1SD is 191 mm
Table 3 Relation of Lines of Magnetic Force Outside the Cylinder Body when the Diameter of Cylinder 1SD is 18 mm


[0173] With energy conversion efficiency measurement, first, the resistance R1 of both ends of a winding wire is measured in a state in which there is no cylindrical rotating element. Then, the resistance Rx of both ends of a winding wire is measured in a state in which the magnetic core is inserted into the hollow part of the cylindrical rotating element, and the energy conversion efficiency is measured according to Expression ( 27). In Figure 17, a ratio (%) of lines of magnetic force outside the cylindrical body corresponding to the diameter of the cylinder is taken as the lateral axis, and the energy conversion efficiency at a frequency of 21 kHz is taken as the vertical axis. With a graph, the energy conversion efficiency greatly increases at P1 and onwards within the graph and exceeds 70%, and the energy conversion efficiency is maintained at 70% or more in a range of an R1 region illustrated with an arrow . The energy conversion efficiency greatly increases again around P3, and reaches 80% or more in an R2 region. The energy conversion efficiency maintains a high value of 94% or more in an R3 region at P4 and onwards. It depends on the current in the direction of the circumference starting to flow effectively into the cylindrical body that this energy conversion efficiency starts to go up a lot.
[0174] This energy conversion efficiency is an extremely important parameter for designing a fixture with an electromagnetic induction heating system. For example, in the case where the energy conversion efficiency was 80%, the remaining 20% of energy is generated as thermal energy at a location other than the cylindrical rotating element. With respect to a location for generating the energy, in the case where an element such as a magnetic material or the like is arranged inside the cylindrical rotating element, energy is generated in its element. That is, when the energy conversion efficiency is low, there must be measures for the heat to be generated in the excitation coil and magnetic core. The degree of measurements changes a lot with 70% and 80% energy conversion efficiency as the limits according to the study by the inventor and others. Consequently, with the configuration of regions R1, R2, and R3, the configuration serving as the fixture differs greatly. The description will be made with respect to three types of design conditions R1, R2 and R3, and the configuration of the fixture not belonging to any of these. Next, the energy conversion efficiency suitable for designing a fixture will be described in detail.
[0175] The following Table 4 shows results where the configurations corresponding to P1 to P4 in Figure 18 were actually designed as fixtures and evaluated. Table 4 Assessment Results of Fasteners P1 to P4
P1 Fixation Device
[0176] The present configuration is a case where the cross-sectional area of the magnetic core is 5.75 mm x 4.5 mm, and the diameter of the cylindrical body (electroconductive layer) is 143.2 mm. The energy conversion efficiency obtained by the impedance analyzer at that time was 54.4%. The energy conversion efficiency is, from energy to be supplied to the clamping device, a parameter that indicates the contribution to the heating of the cylinder (electroconductive layer). Consequently, even in the case of having designed as a fixture that can emit a maximum of 1000 W, approximately 450 W becomes loss, and its loss becomes heating in the coil and magnetic core. In the case of the present configuration, even when supplying 1000 W for several seconds at power-up, the coil temperature can exceed 200 degrees Centigrade. When considering that the heat resistant temperature in a coil insulator is over 200 degrees Celsius, and the Curie point of the ferrite magnetic core is generally around 200 to 250 degrees Celsius, it is difficult with 45% loss keeping elements such as excitation coil and so on or less than heat resistant temperature. Also, when the temperature of the magnetic core exceeds the Curie point, the inductance of the coil suddenly deteriorates, resulting in load fluctuation.
[0177] Approximately 45% of power supplied to the fixture is spent, and consequently, in order to supply power of 500 W to the cylindrical body (estimating 90% of 1000 W), power of approximately 1636 W has to be supplied to this. This means that the power source is consumed at 16.36 A at the time of 100 V input. In the event that there is a limitation that a permissible current that can be supplied from a coupling plug for commercial AC is 15 A, a current to be supplied may exceed the permissible current. Consequently, with the fixture P1 where the ratio of the lines of magnetic force outside the cylindrical body is 64%, and the energy conversion efficiency is 54.4%, the power to be supplied to the fixture may be insufficient. P2 Fixing Device
[0178] The present configuration is a case where the cross-sectional area of the magnetic core is 5.75 mm x 4.5 mm, and the diameter of the cylindrical body is 127.3 mm. The energy conversion efficiency obtained by the impedance analyzer at that time was 70.8%. At that time, depending on the printing operation of the clamping device, large inert amount of heat is generated in the excitation coil and so on, and the temperature rise of an excitation coil unit, in particular, of the magnetic core can cause a problem. When employing a high specification device where the printing operation of 60 sheets per minute can be performed, such as the clamping device according to the present embodiment, the rotational speed of the cylindrical rotating element becomes 330 mm/s. Consequently, there may be a case where the surface temperature of the cylindrical rotating element is maintained at 180 degrees Centigrade. In such a case, it can be conceivable that the temperature of the magnetic core can exceed 240 degrees Centigrade for 20 seconds, and exceed the temperature of the cylindrical body (electroconductive layer). The Curie temperature of the ferrite to be used as the magnetic core is generally 200 to 250 degrees Centigrade, and in the event that the ferrite exceeds the Curie temperature, the permeability suddenly decreases. When the permeability suddenly decreases, it prevents a magnetic path from forming within the magnetic core. When a magnetic path is prevented from being formed, with the present embodiment, there may be a case where a current in the circumferential direction is induced to make it difficult to generate heat.
[0179] Consequently, when employing the above-mentioned high specification device as the clamping device according to the design condition R1, in order to lower the temperature of the ferrite core, it is desirable to provide a cooling unit. As a cooling unit, an air cooling fan, water cooling fan, heat sink, radiation fin, heat pipe, Bell Choi element, or similar may be employed. Not to mention that a cooling unit does not have to be provided in the event that high specification is not demanded in the present configuration. P3 Fixation Device
[0180] The present configuration is a case where the cross-sectional area of the magnetic core is 5.75 mm x 4.5 mm and the diameter of the cylindrical body is 63.7 mm. The energy conversion efficiency obtained by the impedance analyzer at that time was 83.9%. At that time, the inert amount of heat generated in the excitation coil and so on, but did not exceed the amount of heat that can be heated by heat transfer and natural cooling. When employing a high specification device where the printing operation of 60 sheets per minute can be performed, such as the clamping device according to the present configuration, the rotational speed of the cylindrical body becomes 330 mm/s. Consequently, even with a case where the surface temperature of the cylindrical body is maintained at 180 degrees Celsius, the temperature of the magnetic ferrite core does not rise by 220 degrees Celsius or more. So, with the present configuration, in case of employing a high specification fixture, it is desirable to employ ferrite whose Curie temperature is equal to or greater than 220 degrees Centigrade. In case of employing the fixture according to the design condition R2 as a high specification fixture, it is desirable to optimize the heat resistant design such as ferrite and so on. With the present configuration, in the event that the above high specification is not demanded, the heat resistant design is such that a tier does not have to be performed. P4 Fixation Device
[0181] The present configuration is a case in which the cross-sectional area of the magnetic core is 5.75mm x 4.5mm and the diameter of the cylindrical body is 47.7mm. The energy conversion efficiency obtained by the impedance analyzer at that time was 94.7%. When using a high specification device through which the printing operation of 60 sheets per minute can be performed, such as the clamping device according to the present configuration, the rotation speed of the cylindrical body becomes becomes 330 mm/s, and in a case where the surface temperature of the cylindrical body is kept at 180 degrees Centigrade, that of the excitation coil and so on does not rise equal to or more than 180 degrees Centigrade. This indicates that the excitation coil hardly generates heat. In the case where the ratio of the magnetic force lines outside the cylindrical body is 94.7%, and the energy conversion efficiency is 94.7% (design condition R3), the energy conversion efficiency is sufficiently high and consequently, even when using the P4 fixture as another high specification fixture, a cooling unit does not have to be provided.
[0182] Also, with this region where the energy conversion efficiency is stabilized at a high value, even when a positional relationship between the cylindrical rotating element and the magnetic core fluctuates, the energy conversion efficiency does not fluctuate. In the case where the energy conversion efficiency does not fluctuate, stable amount of heat can be supplied from the cylindrical rotating element. Thus, with a fixture with a fixture film having flexibility, employing that R3 region where the energy conversion efficiency does not fluctuate provides a great advantage.
[0183] As described above, with a fixture configured to have the cylindrical rotating element generating a magnetic field in the axial direction of the same, and for the rotating cylindrical element to perform heating by electromagnetic induction, the design conditions obtained with a The relationship of lines of magnetic force outside the cylindrical body can be classified into regions with permissions R1, R2, and R3 in Fig. 17.
[0184] R1: The ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 70%, but less than 90%.
[0185] R2: The ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 90%, but less than 94%.
[0186] R3: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 94%. 3-7. Heating Characteristics According to “Current in Circumference Direction”
[0187] The "current in the direction of the circumference" described in 3-4 is caused due to the induced electromotive force generated within the circuit S in Figure 6. So, the current in the direction of the circumference depends on the lines of magnetic force housed in the circuit S , and the value of the resistance of the circuit S. Unlike the “Eddy current E//” described later, the current in the circumferential direction has no relation to the magnetic flux density within the material. Therefore, even a cylindrical rotating element made of a thin magnetic metal that does not serve as a thin magnetic path, or even a rotating cylindrical element made of non-magnetic metal, can generate heat with high efficiency. Furthermore, with a range in which a resistance value does not change much, the current in the direction of the circumference does not depend on the thickness of the material either. Figure 18A illustrates the frequency dependence of the energy conversion efficiency of a 20 mm thick aluminum cylindrical rotating element. With a frequency band from 20 to 100 kHz, the energy conversion efficiency remains at or above 90%. As with the first mode, in the case of using a frequency band of 21 to 40 kHz for heating, high energy conversion efficiency is maintained. Next, Figure 18B illustrates, with a cylindrical rotating element having the same shape, the thickness dependence of energy conversion efficiency at a frequency of 21 kHz. A black circle with a solid line indicates experimental results for nickel, a white circle with a dotted line indicates experimental results for aluminum. Both maintain, with a region of 20 to 300 mm in thickness, equal or more than 90% efficiency in energy conversion, and both do not depend on thickness, and can be employed as a heating material for a fixture.
[0188] Consequently, with “heating by a current in the direction of the circumference”, compared to heating by eddy current loss according to the related technique, the design flexibility for the material and thickness of the cylindrical rotating element and the frequency of an alternating current can be extended.
[0189] It is noted that it is a feature of the fixture of R1 according to the present embodiment of the lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core, a ratio of lines of magnetic force passing over the outside of the cylindrical rotating element and the return to the other end of the magnetic core is equal to or greater than 70%. That lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core, a ratio of lines of magnetic force passing over the outside of the rotating cylindrical element and returning to the other end of the magnetic core, is equivalent to or greater at 70% which is equivalent to the sum of the permeance of the cylindrical body and the permeance of the interior of the cylindrical body is equal to or less than 30% of the permeance of the cylindrical body. Consequently, one of the characteristic configurations of the present embodiment is a configuration in which, if the permeance of the magnetic core is said to be Pc, the permeance of the interior of the cylindrical body is Pa, and the permeance of the cylindrical body is Ps , a relationship of 0.30 x Pc > Ps + Pa is satisfied.
[0190] Also, in the case of expressing the relational expression of permeance by replacing it with a magnetic resistance, the relational expression of permeance is as follows.
Where the combined magnetic resistance Rsa of Rs and Ra is calculated as follows.
Rc: magnetic resistance of the magnetic core Rs: magnetic resistance of the electroconductive layer Ra: magnetic resistance of the region between the electroconductive layer and the magnetic core Rsa: combined magnetic resistance of Rs and Ra
[0191] It is desirable that the above relational expression be satisfied in a cross section in a direction orthogonal to the generatrix direction of the cylindrical rotating element throughout the region of maximum transport of a recording material from the fixture.
[0192] Similarly, the R2 fixture of the present embodiment satisfies the following expressions.
The R3 fixture of the present embodiment satisfies the following expressions.
3-8. Advantage over the Closed Magnetic Path
[0193] Here, in order to design so that the lines of magnetic force pass over the outside of the cylindrical rotating element, there is also a method to form a closed magnetic path. The closed magnetic path mentioned here is, as illustrated in Figure 35, the magnetic core 2 which forms an external loop to the cylindrical rotating element, and has a form that the fastening film 1 is covered on a part of the turn. However, when a loop is formed using the magnetic core 2c, this causes a problem that leads to an increase in the size of the device. On the other hand, with the present embodiment, the design can be executed with the configuration of an open magnetic path, in which the magnetic core does not form a loop outside the cylindrical rotating element and, consequently, the reduction in the size of the device can be realized. .
[0194] Furthermore, in the case of using a band from 21 to 100 kHz as the frequency of alternating current, the configuration of the open magnetic path, in which the magnetic core does not form a loop outside the cylindrical rotating element according to the present embodiment , has an advantage other than device size reduction. Next, this advantage will be described.
[0195] With the closed magnetic circuit configuration, where the magnetic core does not form a loop outside the cylindrical rotating element, a low frequency of a band of 50 to 60 Hz is employed as the frequency of the alternating current. This is because when the frequency of the magnetic field is increased, the design of the fixture becomes difficult according to the following reasons. In order to have the cylindrical rotating element generating heat with high efficiency, in the case of employing a high frequency of a band from 21 to 100 kHz as the frequency of alternating current, when employing a magnetic core made of metal, such as -mo silicon steel sheet as the magnetic core, the loss in the core increases. Therefore, baking ferrite which has low loss at a high frequency is suitable as the magnetic core material. However, baking ferrite is a sintering material and therefore it is a weak material. When forming a magnetic core (closed magnetic path) having at least four-letter L configurations made up of this weakly baked ferrite, the device size is increased to deteriorate the mounting properties, and also to increase the risk that the device is damaged in the event of an impact applied externally to the device due to the device being dropped or similar. In the event that the magnetic core has been damaged, and yet a part of it has been disrupted, the ability to orient the lines of magnetic force is significantly deteriorated, and a function for the rotating cylindrical element 1 to generate heat is lost. This is physically equivalent to a closed magnetic path transformer, when a part of the magnetic path is interrupted, the original performance is not maintained. Furthermore, in the case of a closed magnetic path where the magnetic core is wound outside the cylindrical rotating element, there may be a case in which, in order to improve the assembly and convertibility properties, the magnetic core has to be divided into several parts. Although the description has been made, where it is desirable to suppress an aperture gap between the split magnetic cores to 50 mm or less, when the magnetic core is split, a design problem such as space management or the like is provoked. Also, risk is included where a foreign object such as dust or the like is placed in a junction part between the split magnetic cores, and the performance deteriorates.
[0196] On the other hand, in the case of employing a high frequency of a band from 21 to 100 kHz as the frequency of alternating current, the clamping device, which is configured in an open magnetic path where the magnetic core does not form a loop outside the cylindrical rotating element, provides the following advantages.
[0197] 1. The shape of the magnetic core can be configured into a rod shape, and consequently, the impact resistance performance is easily improved. In particular, this is advantageous when using baking ferrite.
[0198] 2. The magnetic core does not necessarily have to include a letter L configuration or division configuration, and consequently, space management is facilitated.
[0199] 3. The cross-sectional area of the core can be reduced when changing a magnetic field to a high frequency, and consequently, the entire device can be reduced in size. (4) Results of Comparative Experiments
[0200] Next, the description will be made in relation to the results of comparative experiments between an image forming apparatus with the configuration of the present modality and an image forming apparatus according to the related technique. Comparative Example 1
[0201] The present comparative example has, with respect to the first embodiment, a configuration in which the permeance of the magnetic core is reduced (magnetic resistance is increased) by dividing the magnetic core into two or more magnetic cores in the longitudinal direction, and providing a space between the divided magnetic cores.
[0202] Fig. 19 is a perspective view of the magnetic core and coil in comparative example 1. A magnetic core 13 is of ferrite where the relative permeability is 1800, and the magnetic flux density is 500 mT saturated, and has a cylindrical shape in which the diameter is 5.75 mm2, the cross-sectional area is 26 mm2, and the length is 22 mm. Ten magnetic cores 13 are arranged at equal intervals by placing a sheet of mylar with a thickness G = 0.7 mm between them in dotted parts in Figure 19, and the entire length B is 226.3 mm. Regarding the cylindrical rotating element (electroconductive layer), aluminum having a relative permeability of 1.0 was used with the first modality. With the cylindrical rotating element, the thickness was 20 mm, and the diameter was 24 mm. The permeance per unit length of the magnetic core was calculated by replacing the parameters indicated in Table 5 with expressions (15) to (21).
[0203] Also, when calculating a ratio of the lines of magnetic force passing through each region assuming the permeance per unit length of the magnetic core is 1.1 x 10-9 Hm according to the above calculation, the results thereof are as in the following Table 6. Table 5 Magnetic Permeance in Comparative Example 1
Table 6 Magnetic Permeance in Comparative Example 1


[0204] Many spaces are provided between the split cores, and consequently, the magnetic core permeance is lower compared to the first modality. So the ratio of lines of magnetic force outside the cylindrical body is 63.8%, and this is a configuration that does not satisfy a design requirement of “R1: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than than 70%”. With the shapes of lines of magnetic force, the magnetic poles are formed for each of the magnetic cores from 3a to 3j as illustrated in a dotted line in Figure 20, a part of these returns to the air inside the cylindrical body as with the line of magnetic force L, and also, with a part of these, a magnetic flux vertically penetrates the material of a clamp cylinder in a black circle part as with L1.
[0205] Also, the permeance of each component of the fixture according to comparative example 1 is as follows. The magnetic core permeance Pc = 1.1 x 10-9 H.m. The permeance Pa inside the cylindrical body = 1.3 x 10-10 + 4.0 x 10-10 H.m. The permeance Ps of the cylindrical body = 1.9 x 10-12 H.m.
[0206] Consequently, comparative example 1 does not satisfy the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0207] When replacing this with the magnetic resistance, the magnetic resistance Rc of the magnetic core = 9.1 x 108 1/ (H.m) is maintained.
[0208] The magnetic resistance inside the cylindrical body is the combined reluctance of the film guide Rf and air inside the cylindrical body Rair, and consequently, when calculating this using the following expression, Ra = 1.9 x 109 1/(Km) remains.

[0209] The magnetic resistance Rs of the cylindrical body = 5.3 X 1011 1/(Hm), and consequently, the combined magnetic resistance Rsa of Rs and Ra is obtained as follows,
Rsa = 1.9 x 109 1/(Hm)
[0210] Consequently, the fixture according to comparative example 1 does not satisfy the following magnetic resistance expression. 0.30 x Rsa ≥ Rc
[0211] In this case, it can be conceived that a current in the direction of the circumference and an eddy current El in a direction illustrated in Figure 32 partially flow into the cylindrical rotating element made of aluminum, and both contribute to the heating. This eddy current El will be described. Eddy current El has a characteristic that the closer to the surface of the material, the greater the El, and closer to the interior of the material, the smaller the El exponentially becomes. Its depth will be called the penetration depth d, and it is represented with the following expression. δ = 503 x (ρ/fµ)A1^2 ... (28) δ: penetration depth m f: excitation circuit frequency Hz µ: permeability H/m ρ: reluctance Ωm
[0212] The penetration depth d indicates the depth of absorption of electromagnetic waves, and the intensity of electromagnetic waves becomes equal to or less than 1/e at a location deeper than that. Its depth depends on a frequency, permeability, and reluctance. Comparative Experiment Results
[0213] Fig. 21 illustrates the frequency dependence of energy conversion efficiency on a 20 mm thick aluminum cylindrical rotating element. black circles indicate a frequency and energy conversion efficiency result in the first embodiment, and white circles indicate a frequency and energy conversion efficiency result in comparative example 1. The first embodiment maintains, with a frequency band from 20 to 100 kHz, the power conversion efficiency equal to or greater than 90%. Comparative example 1 is the same as the first modality at 90 kHz or higher, 85% at 50 kHz, 75 kHz at 30%, 60% at 20 kHz, so the lower the frequency, the lower the energy conversion efficiency .
[0214] The cause of this will be described below. With the configuration of comparative example 1, it can be conceived that a current in the direction of the circumference and an eddy current El in a direction illustrated in Fig. 32 partially flow and contribute to warming.
[0215] This eddy current El is frequency dependent as illustrated in Expression (28). That is, the higher the frequency, the more electromagnetic waves are easily absorbed in the aluminum, and consequently, the energy conversion efficiency increases.
[0216] With the first modality, in the case of employing a frequency from 21 kHz to 40 kHz as well, the amount of heat generated in the excitation coil is sufficiently small, compared to the amount of heat that can be radiated by heat transfer and natural cooling. In this case, the temperature of the excitation coil is the lower temperature than that of the cylindrical rotating element, and consequently, heat resistant design does not have to be realized with respect to the coil and magnetic core.
[0217] On the other hand, according to comparative example 1, a frequency band of 25 kHz or less whose energy conversion efficiency is equal to or less than 70% is not available. In this case, steps must be taken to increase the coil temperature, or a location where the energy conversion efficiency is about 90% has been employed by upgrading the energy source to increase the frequency band to 90 kHz or higher.
[0218] As described above, according to the configuration of the first embodiment, even when employing aluminum, which is a non-magnetic metal, as the material of the electroconductive layer, the electroconductive layer can be heated with high efficiency without increasing the thickness of the layer. electroconductive layer. Furthermore, even in the case of employing a frequency band from 21 to 100 kHz, heat can be generated with low loss, the magnetic core does not have to be formed as a closed magnetic path, and consequently, the magnetic core design is facilitated. Consequently, even when the output is high, the entire device can be designed in a compatible manner.
[0219] Now, a fixture that satisfies the following two conditions is considered.
[0220] Condition 1. All material of the rotating cylindrical element, and the material of an element in a region between the magnetic core and the rotating cylindrical element are non-magnetic materials having the same relative air permeability.
[0221] Condition 2. The configuration is made where 94% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the magnetic core which passes over the outside of the cylindrical rotating element (clamping device R3).
[0222] If the magnetic resistance of the magnetic core is said to be Rc, and the combined magnetic resistance of the magnetic resistance of the rotating cylindrical element, and the magnetic resistance of a region between the rotating cylindrical element and the magnetic core is Rsa, a condition can be represented as follows where 94.7% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the magnetic core which passes over the exterior of the cylindrical rotating element. 0.06 x Rsa ≥ Rc The magnetic resistance Rc of the magnetic core is represented as follows.
µc: core permeability Sc: core cross-sectional area
[0223] The combined magnetic resistance Rsa of the magnetic resistance of the cylindrical rotating element, and the magnetic resistance of a region between the magnetic core and the cylindrical rotating element are represented as follows.
msa: permeability of the rotating element and a region between the magnetic core and the rotating element Ssa: cross-sectional area of the cylindrical rotating element and a region between the magnetic core and the cylindrical rotating element
[0224] In accordance with the above, an expression is expressed as follows that satisfies the condition that 94% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the passing magnetic core on the outside of the cylindrical rotating element.
0.06 x mcSc ≥ µsaSsa
[0225] Now, the vacuum permeability is said to be mm0, and the relative permeability of the magnetic core is mc0, the air permeability is 1.0, and consequently, from Condition 1, msa = 1 ,0 x m0, and mc = mc0 x m0, and hence an expression satisfying Condition 2 is as follows. 0.06 x 100 x □coSc ≥ Ssa 0.06 x µc0 x Sc ≥ Ssa
[0226] In accordance with the above, it was concluded that, with respect to the fixture that satisfies Condition 1 and Condition 2, the sum of the cross-sectional area of the cylindrical rotating element and the cross-sectional area of a region between the core magnetic and the cylindrical rotating element is equal to or less than (0.06 x mc0) times the cross-sectional area of the core. Note that Condition 1 does not have to be the same as the 1.0 relative air permeability. In the case where the permeability is less than 1.1, the relational expressions mentioned above can be applied.
[0227] It is noted that, even with the configuration of a closed magnetic path having a shape in which the magnetic core forms a loop outside the cylindrical rotating element (electroconductive layer) as illustrated in Fig. 35, when the permeability of the magnetic core is small, the present embodiment takes effect. That is, there may be a case where the permeability of the magnetic core is too low to induce the lines of magnetic force to the outside of the rotating cylindrical element. In such a case, when the magnetic resistance of the magnetic core satisfies a condition that is 30% or less of the combined magnetic resistance of the magnetic resistance of the cylindrical rotating element and the magnetic resistance of a region between the rotating cylindrical component and the core, 70% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the magnetic core by passing over the outside of the rotating cylindrical element.
[0228] Similarly, when the magnetic resistance of the magnetic core satisfies a condition that is 10% or less of the combined magnetic resistance of the magnetic resistance of the cylindrical rotating element and the magnetic resistance of a region between the cylindrical rotating element and the core, 90% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the magnetic core by passing over the outside of the rotating cylindrical element. Similarly, when the magnetic resistance of the magnetic core satisfies a condition that is 6% or less of the combined magnetic resistance of the magnetic resistance of the cylindrical rotating element and the magnetic resistance of a region between the rotating cylindrical component and the core, 94% or more of the lines of magnetic force emitted from one end of the magnetic core return to the other end of the magnetic core by passing over the outside of the rotating cylindrical element. Second Mode
[0229] The present modality is another example with respect to the first modality described above, and differs from the first modality by the fact that austenitic stainless steel (SUS304) is used as the cylindrical rotating element (electroconductive layer). The following are, as a reference, the results summarizing the resistivity and relative permeability in various types of metal, and calculating the penetration depth at 21 kHz, 40 kHz and 100 kHz, according to expression (28). Table 7 Cylindrical Rotating Element Penetration Depth

[0230] According to Table 7, SUS304 has high resistivity, and low relative permeability, and consequently, penetration depth d is large. That is, SUS304 readily penetrates electromagnetic waves, and consequently, SUS304 is hardly employed as an induction heating heating element. Consequently, with an electromagnetic induction heating fixture according to the related technique, it was difficult to achieve high energy conversion efficiency. However, Table 7 indicates, with the present embodiment, that it is possible to achieve high energy conversion efficiency.
[0231] Note that the configuration of the second mode is the same as the configuration of the first mode, except that SUS304 is used as the material of the cylindrical rotating element. The lateral transverse shape of the fixture is also the same as in the first embodiment. Regarding the heating layer, SUS304 whose relative permeability is 1.0 is used, and the film thickness is 30 mm, and the diameter is 24 mm. The elastic layer and the surface layer are the same as in the first embodiment. The magnetic core, excitation coil, temperature sensing element, and temperature control are the same as in the first embodiment.
[0232] The permeance and magnetic resistance of each component of the fixture according to the present modality will be illustrated in the following Table 8. Table 8 Magnetic Permeance in the Second Modality

[0233] With the present configuration, the ratio of magnetic flux outside the cylindrical body is 99.3%, and satisfies the condition of “R3: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 94%”.
[0234] Also, the permeance of each component of the second embodiment is as follows from Table 8. The permeance Pc of the core = 5.9 x 10-8 H.m. The permeance Pa inside the cylindrical body = 1.3 x 10-10 + 4.0 x 10-10 H.m. The permeance Ps of the cylindrical body = 2.9 x 10-12 H.m.
[0235] Consequently, the second modality satisfies the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0236] When replacing this with the magnetic resistance, the magnetic resistance Rc of the magnetic core = 1.7 x 107 1/ (H.m).
[0237] The magnetic resistance inside the cylindrical body is a combined reluctance of the magnetic resistance of the film guide Rf and air inside the cylindrical body Rair, and consequently, when calculating this using the following expression, Ra = 1.9 x 109 1 / (Hm) holds.

[0238] The magnetic resistance Rs of the cylindrical body = 3.5 x 1011 1/ (Hm), and consequently, the combined magnetic resistance Rsa of Rs and Ra is obtained as follows,
Rsa = 1.9 x 109 1/(Km) is maintained.
[0239] Consequently, the fixture according to the second embodiment satisfies the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc
[0240] In accordance with the above, the fixture according to the second embodiment satisfies the relational expression of permeance (magnetic resistance), and consequently can be employed as the fixture. Comparative Example 2
[0241] A comparative example 2 has, against the second embodiment, a configuration where the magnetic core permeance is reduced by dividing the magnetic core into two or more cores in the longitudinal direction, and providing many spaces between the divided magnetic cores. . The magnetic core is, in the same way with comparative example 1, of ferrite having a cylindrical shape where the diameter is 5.4 mm, the cross-sectional area 23 mm2, and the length B is 22 mm, and ten magnetic cores are arranged with an equal gap by placing between them a sheet of mylar having thickness G = 0.7. Regarding the cylindrical rotating element (electroconductive layer) of the fixing film, in the same way as in the second modality, SUS304 whose relative permeability is 1.02 was used, and the thickness of the film was 30 mm, and the diameter was 24 mm The permeance per unit length of the magnetic core can be calculated in the same way as in comparative example 1, the permeance per unit length is 1.1 x 10-9 Hm A ratio of the lines of magnetic force passing through each region it is like in the following table. Table 9

[0242] The magnetic core permeance is lower compared to the second modality, and consequently, the ratio of lines of magnetic force outside the cylindrical body is 64.1%, and this does not satisfy the condition of “R1: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 70%.
[0243] Also, the permeance of each component of the comparative example is as follows. The magnetic core permeance Pc = 1.1 x 10-9 H.m. The permeance Pa inside the cylindrical body = 1.3 x 10-10 + 4.0 x 10-10 H.m The permeance Ps of the cylindrical body = 2.9 x 10-12 H.m.
[0244] Consequently, the fixture according to comparative example 2 does not satisfy the following related permeance expression. Ps + Pa ≤ 0.30 x Pc
[0245] When replacing this with the magnetic resistance, the magnetic resistance Rc of the magnetic core = 9.1 x 108 1/ (H.m)
[0246] The magnetic resistance inside the cylindrical body (region between the cylindrical body and the magnetic core): Ra = 1.9 x 109 1/(H•m) The magnetic resistance of the cylindrical body: Rs = 3.5 x 1011 1/(H•m) The combined magnetic resistance Rsa of Rs and Ra: Rsa = 1.9 x 109 1/(H•m)
[0247] Consequently, comparative example 2 does not satisfy the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc
[0248] In this case, it can be conceivable that current in the direction of the circumference and an eddy current El in a direction illustrated in Figure 32 partially flow into the cylindrical rotating element made of SUS304, and both contribute to the heating. Comparative Experiment Results
[0249] Figure 22 illustrates the frequency dependence of energy conversion efficiency in the cylindrical rotating element of SUS304 with a thickness of 30 mm. The black circles indicate a frequency and an energy conversion efficiency result in the second modality, and the white circles indicate a frequency and an energy conversion efficiency result in comparative example 2. The second modality maintains, with a band frequency range from 20 to 100 kHz, the energy conversion efficiency equal to or greater than 90%. Comparative example 2 is the same as in the second mode at 100 kHz or more, 80% at 50 kHz, 70% at 30 kHz, 50% at 20 kHz, so the lower the frequency, the lower the efficiency of the conversion of energy.
[0250] With the second modality, in the case of employing a frequency from 22 kHz to 40 kHz, the energy conversion efficiency is at most 94%, and consequently, the amount of heat generated in the excitation coil is sufficiently less compared to the amount of heat that can be radiated by heat transfer and natural cooling. In this case, the temperature of the excitation coil was constantly lower than that of the rotating cylindrical element, and consequently, the heat resistance design did not have to be carried out with respect to the coil and magnetic core.
[0251] On the other hand, with comparative example 2, the frequency band of 35 kHz or less whose energy conversion efficiency is equal to or less than 70% is unavailable. In this case, measurements for rising coil temperature had to be taken, or a location where the energy conversion efficiency is approximately 90% had to be employed by upgrading the power source to increase the frequency band to 90 kHz or higher.
[0252] As described above, according to the configuration of the second embodiment, the fixing device can be provided where even when employing SUS304 which has low relative permeability as the material of the electro-conductive layer, the electro-conductive layer can be heated with high efficiency without increasing the thickness of the electroconductive layer. Third Mode
[0253] With the present embodiment, the description will be made with respect to a configuration employing metal having high relative permeability as the cylindrical rotating element.
[0254] As with the present embodiment, with a configuration where the rotating cylindrical element is caused to generate heat primarily by a current in the direction of the circumference, the metal having low relative permeability does not necessarily have to be employed as the element. cylindrical swivel, and even metal having high relative permeability can be used.
[0255] With a clamping device with an electromagnetic induction heating system according to the related technique, there was a problem in that even when employing nickel having high relative permeability or similar as the cylindrical rotating element, in the case of reducing the thickness of the cylindrical rotating element, the energy conversion efficiency is reduced. So, the present embodiment illustrates that even in the case where the nickel thickness is small, the cylindrical rotating element can be made to generate heat with high efficiency. Reducing the thickness of the cylindrical rotating element provides advantages such as improved durability against repetitive bending, and improved quick start properties due to reduced heat capacity, and so on.
[0256] The configuration of the imaging apparatus is the same as in the first embodiment, except that nickel is employed as the cylindrical rotating element. With the third embodiment, nickel whose relative permeability is 600 of the cylindrical rotating element. With the cylindrical rotating element, the thickness was 75 mm, and the diameter was 24 mm. The elastic layer and the surface layer are the same as in the first embodiment, and therefore their description will be omitted. Also, the excitation coil, temperature sensing element, and temperature control are the same as in the first embodiment. This magnetic core 2 is ferrite where the relative permeability is 1800, the saturated magnetic flux density is 500 mT, the diameter is 14 mm, and the length B is 230 mm.
[0257] The permeance ratio of each component of the fixation device of the present modality will be illustrated in the following Table 10. Table 10 Magnetic Permeance in the Third Modality


[0258] With the present embodiment, the ratio of lines of magnetic force outside the cylindrical body is 98.7%, and satisfies the condition of “R3: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than the than 90%”. Nickel partially serves as the magnetic path, and consequently, the magnetic flux ratio outside the cylindrical body is reduced by approximately 1%, but sufficiently high thermal efficiency is obtained. Also, the permeance of each component of the third embodiment is as follows from Table 10. The magnetic core permeance: Pc = 3.5 x 10-7 Km. The permeance inside the cylindrical body: Pa = 1.3 x 10-10 + 2.4 x 10-10 km. The permeance of the cylindrical body: Ps = 4.2 x 10-9 km. Consequently, the fastening device according to the third embodiment satisfies the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0259] Now, when replacing the relational expressions of permeance mentioned above with relational expressions of magnetic resistance, the following expressions are obtained. The magnetic resistance of the magnetic core: Rc = 2.9 x 106 1/(Km). The magnetic resistance of a region between the cylindrical body and the magnetic core: Ra = 2.7 x 109 1/(Km). The magnetic resistance of the cylindrical body: Rs = 2.4 x 108 1/(Km). The combined magnetic resistance of Rs and Ra: Rsa = 2.2 x 108 1 / (H.m).
[0260] Consequently, the third embodiment satisfies the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc
[0261] In accordance with the above, the fixture according to the third embodiment satisfies the relational expressions of permeance (relational expressions of magnetic resistance), and consequently can be employed as the fixture. Comparative Example 3
[0262] As a comparative example 3, a configuration will be described here, the cross-sectional areas of the magnetic core 2 and the cylindrical rotating element differ from that of the fixture according to the third embodiment, which does not satisfy “configuring the magnetic flux ratio outside the cylindrical body equal to or greater than 90%”. In particular, the description will be made with respect to a configuration in which the cylindrical rotating element serves as the main magnetic path. Figure 23 is a cross-sectional view of the clamping device according to comparative example 3, a clamping cylinder 11 is employed as a rotating electromagnetic induction heating element instead of the clamping film. This is a configuration where the nip N is formed by pressing force of clamping roller 11 and pressing roller 7, an image carrier P and a toner image T are set to rotate in the direction of the arrow.
[0263] As the cylindrical body (cylindrical rotating element) 11a of the clamping cylinder 11, nickel (Ni) whose relative permeability is 600, the thickness is 0.5 mm, and the diameter is 60 mm is used. Note that the material of the cylindrical body is not restricted to nickel, and may be magnetic metal having high relative permeability such as iron (Fe), cobalt (Co) or the like.
[0264] Magnetic core 2 has a cylindrical shape consisting of an integrated component that is not split. The magnetic core 2 is disposed within the clamping cylinder 11 using a clamping unit not illustrated, and serves as an element configured to induce the lines of magnetic force in accordance with an alternating magnetic field generated by the excitation coil 3 to the magnetic cylinder. fixture 11 to form a path (magnetic path) for lines of magnetic forces. This magnetic core 2 is ferrite whose relative permeability is 1800, the saturated magnetic flux density is 500 mT, the diameter is 6 mm, and the length B is 230 mm. The results of the permeance calculation of each fixture component according to comparative example 3 will be summarized in Table 11.

[0265] The permeance of each component of comparative example 3 is as follows from Table 11. The magnetic core permeance: Pc = 4.4 x 10-8 Km.
[0266] The permeance inside the cylindrical body (region between the cylindrical body and the magnetic core): Pa = 1.3 x 10-10 + 3.3 x 10-9 Km The permeance of the cylindrical body: Ps = 7.0 x 10-8 km
[0267] Consequently, the following relational expression of permeance is not satisfied. Ps + Pa £ 0.30 x Pc
[0268] When substituting the expressions mentioned above for the magnetic resistance, the following expressions are obtained. The magnetic resistance of the magnetic core: Rc = 2.3 x 107 1/(Km)
[0269] The magnetic resistance inside the cylindrical body (a region between the cylindrical body and the magnetic core): Ra = 2.9 x 108 1/(Km) The magnetic resistance of the cylindrical body: Rs = 1.4 x 107 1 /(Km) The combined magnetic resistance of Rs and Ra: Rsa = 1.4 x 107 1/(Km)
[0270] Consequently, comparative example 3 does not satisfy the following relational expression of magnetic resistance. 0.30 x Rsa > Rc
[0271] The fixture according to comparative example 3 has a configuration in which the permeance of the cylindrical body is greater than the permeance of the magnetic core by 1.5 times. Consequently, the outside of the cylindrical body does not serve as the magnetic path, and the ratio of the lines of magnetic force outside the cylindrical body is 0%. Consequently, when generating magnetic field lines using the configuration of comparative example 3, the main magnetic path is the cylindrical body (cylindrical rotating element) 11a, and the magnetic path is not formed outside the cylindrical body. With respect to the shapes of the magnetic force line in this case, as illustrated in dotted lines in Figure 24, the magnetic force lines from the magnetic core 2 enter the cylindrical rotating element 11a itself, and return to the magnetic core 2. Also, the leakage magnetic fields LB are generated in some spaces of the coil 3, and enter the cylindrical rotating element 11a itself. A cross-sectional view at center position D will be illustrated in Figure 25A. This is a schematic view of lines of magnetic force at a time when the current in coil 3 increases in the direction of arrow I.
[0272] The lines of magnetic force Bin passing through the magnetic path will be illustrated with arrows (eight x marks circled with a circle) for the direction of depth in space in the drawing. The arrows (eight black circles) towards the front side in the space in the drawing represent lines of magnetic force Bout to return to the interior of the cylindrical rotating element 11a. Within the rotating cylindrical element 11a, and particularly a part indicated with XXVB, as illustrated in Figure 25B, a large number of eddy currents E// occur so as to form a magnetic field to prevent change in a magnetic field indicated with a black circle. With eddy current E//, in a precise sense, there are parts that are mutually canceling and parts that are mutually accentuated, and finally, the sum E1 and E2 of eddy currents indicated by a dotted line arrow becomes dominant. Here, then, E1 and E2 will be called surface currents. When surface currents E1 and E2 occur in the direction of the circumference, Joule heat is generated in proportion to the surface resistance of the heating layer of the clamping cylinder 11a. Such current also repeats generation/elimination and change of direction in sync with the high frequency current. Also, the loss of hysteresis at the time of generation/elimination of a magnetic field also contributes to the generation of heat.
[0273] The generation of heat according to the eddy current E//, or generation of heat according to the surface currents E1 and E2, is physically equivalent to that illustrated in Figure 31, and the generation of heat according to the current E// parasite in this direction will substantially be called loss of excitation, and it is a physical phenomenon equivalent to that represented with the following expression.
[0274] Now the “Loss of Excitation” will be described. "Loss of excitation" is a case where the direction of a magnetic field B// within the material 200a of a rotating electromagnetic induction heat generating element 200 illustrated in Figure 31 is parallel with the X axis of the rotating element, while the magnetic lines of force in the direction of the arrow B// are increasing, an eddy current is generated in one direction canceling its increase. This eddy current will be called E//. On the other hand, in a case where the direction of the magnetic field B// within the material 200a of the rotating electromagnetic induction heat generating element 200 illustrated in Figure 32 is perpendicular to the X axis of the rotating element, while the magnetic flux in the direction of the arrow Bl is increasing, an eddy current is generated in one direction canceling its increase. This eddy current will be called El.
[0275] As with comparative example 3, with a configuration in which most of the lines of magnetic force emitted from one end of the magnetic core 2 pass through the interior of the cylindrical rotating element material and return to the other end of the magnetic core, heat is generated in the cylindrical rotating element mainly by Joule heat according to eddy current E//. The heat generation according to this eddy current E// is substantially called “excitation loss”, and the amount of heat generated Pe by the eddy current is represented by the following expression.
Pe: the amount of generated heat caused due to eddy current loss t: thickness of the clamping cylinder f: frequency Bm: maximum magnetic flux density ρ: resistivity Ke: proportional constant
[0276] As illustrated in the expression above, the amount of heat generated Pe is proportional to the square of “Bm: maximum magnetic flux density within the material”, and consequently, it is desirable to select a ferromagnetic material such as iron, cobalt, nickel, or alloy thereof, as a constituent. On the contrary, when employing a weak magnetic material or non-magnetic material, the thermal efficiency is deteriorated. The amount of heat generated Pe is proportional to the square of the thickness t, and consequently, when reducing the thickness equal to or less than 200 mm, this causes a problem in that the thermal efficiency is deteriorated, and a material having high resistivity is also disadvantageous. That is, the clamping device according to comparative example 3 is highly dependent on the thickness of the cylindrical rotating element. Comparative Experiment
[0277] The description will be made with respect to the results of a comparative experiment being performed with respect to the dependence of the thickness of the cylindrical rotating element of comparative example 3 and the third modality. As a cylindrical rotating element made of nickel for the comparative experiment, an e-element whose diameter is 60 mm, and the length is 230 mm was employed, and three types of thickness (75 mm, 100 mm, 150 mm, and 200 mm ) were prepared. With the magnetic core, with the third embodiment, a material with a diameter of 14 mm, and with comparative example 3, a material with a diameter of 6 mm, were used. One reason why the diameters of the magnetic cores differ between the third embodiment and comparative example 3 is for differentiation, where comparative example 3 has a configuration that does not satisfy: “R1: the ratio of lines of magnetic force outside the cylindrical body is equal or greater than 70%”, and the third modality has a configuration that satisfies: “R2: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 90%”. The following Table 12 illustrates the “ratio of lines of magnetic force outside the cylindrical body” for each thickness of cylindrical rotating elements according to the third embodiment and comparative example 3. It was concluded from Table 12 that the ratio of lines of Magnetic force outside the cylindrical body of the cylindrical rotating element of Comparative Example 3 is highly sensitive to the thickness of the rotating cylindrical element and has a high dependence on the thickness, and the third embodiment is insensitive to the thickness of the rotating cylindrical element and has a low dependence on the thickness. Table 12 Dependence on the Thickness of the Cylindrical Rotating Element

[0278] Next, the description will be made regarding the results where the magnetic core was disposed inside the cylindrical body, and the energy conversion efficiency at a frequency of 21 kHz was measured. First, the resistance R1 and equivalent inductance L1 of both ends of a winding wire in a state in which there is no cylindrical body are measured. Then the resistance Rx and Lx are measured from both ends of a winding wire in a state in which the magnetic core has been inserted into the cylindrical body. Then the energy conversion efficiency is measured according to Expression (27), and the measured results are illustrated in Figure 26. Efficiency = (Rx - R1) / Rx ... (27)
[0279] Accordingly, with comparative example 3, the decrease in energy conversion efficiency was initiated when the thickness of the cylindrical rotating element reached size equal to or less than 150 mm, and the conversion efficiency of energy reached 81% at 75 mm. As compared to a case in which a non-magnetic metal was employed as the cylindrical rotating element, the energy conversion efficiency is apt to increase particularly when the thickness of the cylindrical rotating element is greater. This is attributed to the fact that the “loss of excitation” that is actually caused is a heat generation phenomenon illustrated with the above-mentioned expression of the amount of heat generated Pe. However, the “loss of excitation” is able to decrease in proportion to the square of the thickness, and consequently, the energy conversion efficiency has decreased to 81% at 75 mm. In general, in order to provide flexibility to the cylindrical body in the fixture, the thickness of the cylindrical rotating element (electroconductive layer) is preferably equal to or less than 50 mm. When exceeding this thickness, the cylindrical rotating element may have poor durability against repetitive bending, or may impart rapid start-up properties due to increased heat capacity.
[0280] With the configuration of comparative example 3, when reducing the thickness of the cylindrical rotating element to equal to or less than 50 mm, the efficiency of electromagnetic induction heating energy conversion becomes equal to or less than 80%. Consequently, as described in 3-6, the excitation coil and so on generate heat, and greatly exceed the amount of heat that can be radiated by heat transfer and natural cooling. In this case, the temperature of the excitation coil becomes extremely high compared to the rotating cylindrical element, and consequently, the value-resistant design of the excitation coil, and cooling measures such as air cooling, water cooling, or the like , are required. Also, in the case of employing baking ferrite as the magnetic core, getting the Curie point at approximately 240 degrees Centigrade can prevent a magnetic path from being formed, and consequently, a material having even higher thermal resistance has to be selected. This leads to increased costs and increased component size. When the excitation coil unit increases in size, the rotating element into which this unit is inserted also increases in size, the terminating capacity increases, and fast start-up properties can be conferred.
[0281] On the other hand, with the configuration of the third mode, the energy conversion efficiency exceeds 95%, and consequently, the heat generation can be performed with high efficiency. Furthermore, the cylindrical rotating element can be configured equal to or smaller than 50 mm, and consequently, it can be employed as a fixing film having flexibility. With the cylindrical rotating element according to the third mode, the heat capacity can be reduced, the heat-resistant design and the radiating design do not have to be implemented in the excitation coil, and therefore, the whole fixture can be be reduced in size, and also highlights the fast startup properties.
[0282] As described above, according to the configuration of the third embodiment, even when forming the electroconductive layer with a material having high relative permeability such as nickel, heat generation can be performed in the electroconductive layer with high efficiency without increasing the thickness. of the electroconductive layer. Fourth Mode
[0283] The present embodiment is a modification of the third embodiment, and differs from the third embodiment configuration only in that the magnetic core is split into two or more cores in the longitudinal direction, and a space is provided between the split cores. Splitting the magnetic core has an advantage that split magnetic cores are less readily damaged due to external impact compared to the magnetic core being configured from an integrated component without splitting the magnetic core.
[0284] For example, when impact is given to the magnetic core in a direction orthogonal to the longitudinal direction of the magnetic core, the configured magnetic core of an integrated component is readily broken, but the split magnetic cores are not readily broken. Other settings are the same as in the third modality, and consequently, the description will be omitted.
[0285] From the fixture configuration according to the fourth embodiment, a configuration where the cylindrical rotating element 1a, magnetic core 3, and coil 2 are provided, and magnetic core 3 has been divided into 10 cores is the same configuration of the configuration of comparative example 1 illustrated in Figure 19. A major difference between the magnetic core 3 according to the fourth embodiment and the magnetic core according to comparative example 1 is the length of a space between the divided cores . While the length of a space in comparative example 1 is 700 mm, the length of a gap is 20 mm in the fourth embodiment. With the fourth embodiment, an insulating sheet where the relative permeability is 1, and the thickness G is 20 mm, such as polyimide or the like, is fitted in the spaces. In this way, a thin insulating sheet is fitted between its magnetic cores, where the spaces of the divided magnetic cores can be guaranteed. With the fourth embodiment, in order to maximally suppress the increase in magnetic resistance of the entire magnetic core, a space between the split cores was designed as small as possible. With the configuration of the fourth embodiment, when obtaining the permeance per unit length of the magnetic core 3 in the same method as in the comparative example 1, the results are as in the following Table 13.
[0286] In addition, the calculated values of permeance per unit of length and magnetic resistance of each component will be illustrated in Table 14. Table 13 Magnetic Permeance in the Fourth Mode

Table 14 Magnetic Permeance in the Fourth Mode

[0287] With the configuration of the fourth mode, the ratio of lines of magnetic force outside the cylindrical body is 97.7%, and satisfies the condition of “R2: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 90%”.
[0288] Also, the permeance of each component of the fourth embodiment is as follows from Table 14. The magnetic core permeance: Pc = 1.9 x 10-7 Km The permeance inside the cylindrical body: Pa = 1.3 x 10-10 + 1.8 x 10-10 Km The permeance of the cylindrical body: Ps = 4.3 x 10-9 Km
[0289] Consequently, the fourth modality satisfies the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0290] When replacing the expressions mentioned above with magnetic resistance, the following expressions are obtained. The magnetic resistance of the magnetic core: Rc = 5.2 x 106 1/(Km) The magnetic resistance inside the cylindrical body: Ra = 3.2 x 109 1/(Hm) The magnetic resistance of the cylindrical body: Rs = 2, 4 x 108 1/(Km) The combined magnetic resistance of Rs and Ra: Rsa = 2.2 x 108 1/(Hm)
[0291] Consequently, the fourth embodiment satisfies the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc
[0292] In accordance with the above, the fixture according to the fourth embodiment satisfies the relational expressions of permeance (relational expressions of magnetic resistance), and consequently can be employed as the fixture. Comparative Example 4
[0293] The present comparative example differs from the fourth embodiment with respect to the length of a space between the split cores and the cylindrical body. With comparative example 4, a clamping cylinder serving as the cylindrical body is employed (Figure 27). The split magnetic cores 22a to 22k are ferrite, whose relative permeability is 1800, and the saturated magnetic flux density is 500 mT, and it has a cylindrical shape whose diameter is 11 mm, and the lengths of the split cores are 22 mm, and these eleven cores are arranged with an equal gap of G = 0.5 mm. With the clamp cylinder serving as the cylindrical body, as a heat generating layer 21a, a layer formed of nickel (relative permeability is 600) whose diameter is 40 mm, and the thickness is 0.5 mm is employed. The permeance and magnetic resistance per unit length of the magnetic core 33 can be calculated in the same way as in the fourth embodiment, and the calculation results are in the following Table 15.
[0294] Also, the magnetic resistance of each space has a value several times greater than the magnetic resistance of the magnetic core. Also, Table 16 illustrates the results of magnetic permeance and magnetic resistance per unit length of each fixture component. Table 15 Magnetic Permeance in Comparative Example 4
Table 16 Magnetic Permeance in Comparative Example 4

[0295] With the permeance ratios in the fixture according to the fourth embodiment, the permeance of the cylindrical body is eight times greater than the permeance of the magnetic core. Consequently, the outside of the cylindrical body does not serve as the magnetic path, and the ratio of lines of magnetic force outside the cylindrical body is 0%. Consequently, the lines of magnetic force do not pass over the outside of the cylindrical body, and are induced into the cylindrical body itself. Also, the magnetic resistance in a part of space is large, and consequently, as with a line shape of magnetic force illustrated in Figure 28, a magnetic pole occurs in each part of space.
[0296] The permeance of each component of comparative example 4 is as follows from Table 16.
[0297] Permeance per unit length of the magnetic core: Pc = 5.8 X 10-9 H-m
[0298] The permeance per unit length inside the cylindrical body (region between the cylindrical body and the magnetic core): Pa = 1.3 X 10-10 + 1.3 X 10-9 HLm
[0299] Permeance per unit length of the cylindrical body: Ps = 4.7 X 10-8 H-m
[0300] Consequently, comparative example 4 does not satisfy the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0301] When replacing the expressions mentioned above with magnetic resistance, the following expressions are obtained.
[0302] The magnetic resistance per unit length of the magnetic core: Rc = 1.7 x 108 1/(H-m)
[0303] The magnetic resistance per unit length inside the cylindrical body (the region between the cylindrical body and the magnetic core): Ra = 7.2 x 108 1/(H-m)
[0304] The magnetic resistance per unit length of the cylindrical body: Rs = 2.1 X 107 1/(H-m) The combined magnetic resistance of Rs and Ra: Rsa = 2.1 X 107 1/(H-m)
[0305] Consequently, comparative example 4 does not satisfy the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc
[0306] The heat generation principle of the configuration of comparative example 4 will be described. First, with a part of space D1 of the magnetic core 22 illustrated in Figure 28, an eddy current E1 is generated in the same way as in comparative example 1 by a magnetic field affecting the cylindrical body. Figure 29A illustrates a cross-sectional view around D1. This is a schematic view of the magnetic field line at a time when the current in coil 23 increases in the direction of arrow I. The lines of magnetic force Bin passing through the magnetic path of the magnetic core will be illustrated with arrows (eight black circles) towards the front direction in the drawing. The arrows (eight x marks) for the depth direction in the drawing represent lines of magnetic force Bni returning into the cylindrical rotating member 21a. Within the material of the cylindrical rotating element 21a, and particularly a part indicated with XXIXB, as illustrated in Figure 29B, a large number of eddy currents E// occur so as to form a magnetic field to prevent the change in the indicated magnetic field Bni with an x mark inside a white circle. With eddy current E//, in a precise sense, there are parts that are mutually canceled and parts that are mutually intensified, and finally, the sum E1 (solid line) and E2 (dotted line) of eddy currents becomes dominant. When indicating this using a perspective view in Figure 29C, an eddy current (surface current) occurs to cancel a line of magnetic force in the direction of the arrow of the affected magnetic force line Bni within the material of the cylindrical rotating element, a current E1 flows to the outer surface, and a current E2 flows to the inner side. When surface currents E1 and E2 occur in the direction of the circumference, with the heat generating layer 21a of the clamping cylinder, the current flows to a surface part in a concentrated manner, and consequently, Joule heat is generated in proportion to the surface resistance. Such current also repeats generation/elimination and change of direction in sync with the current at high frequency. Also, the hysteresis loss at the time of generation/elimination of a magnetic field also contributes to the generation of heat. The heat generation according to the eddy current E//, or the heat generation according to the surface currents E1 and E2 is represented by Expression (1) in the same way as in comparative example 3, and decreases with the square of the thickness t.
[0307] Then, at D2 in Figure 28, a magnetic flux vertically penetrates the material of the clamping cylinder. An eddy current in this case occurs in an El direction illustrated in Figure 32. With comparative example 4, it can be seen that the occurrence of an eddy current in this direction also contributes to the generation of heat.
[0308] Eddy current El has a characteristic where the closer to the surface of the material, the greater the El, and closer to the interior of the material, the smaller the El exponentially becomes. Its depth will be called the penetration depth d, and it is represented with the following expression. δ = 503 x (ρ/fµ)A1/2 ... (28) Penetration depth δ m Excitation circuit frequency f Hz Permeability µ H/m Reluctance ρ Ωm
[0309] The penetration depth d indicates the depth of absorption of electromagnetic waves, and the intensity of electromagnetic waves becomes equal to or less than 1/e at a location deeper than that. On the contrary, most of the energy is absorbed to this depth. Its depth depends on a frequency, permeability, and reluctance. The reluctance r (Wm) and the relative permeability m, and the penetration depth dm at each nickel frequency are illustrated as the following Table. Table 17

[0310] With nickel, the penetration depth is 37 mm at a frequency of 21 kHz, and when the nickel thickness is less than this thickness, electromagnetic waves penetrate the nickel, and the amount of heat generated according to a eddy current is greatly reduced. That is, even when an eddy current El occurs, the heat generation efficiency is influenced by the material thickness of approximately 40 mm. Consequently, in the case of employing magnetic metal as a heat generating layer, it is desirable that its thickness be greater than the penetration depth. Comparative Experiment
[0311] The description will be made with respect to the results of the experiment comparing the thickness dependence of the cylindrical rotating element between the fourth modality and the comparative example 4. As a cylindrical rotating element made of nickel according to the comparative example 4, a element whose diameter is 60 mm, and the length is 230 mm was used, and four types of thickness (75 mm, 100 mm, 150 mm, and 200 mm) were prepared. The fourth embodiment has a configuration where the magnetic core is split in the longitudinal direction, so as to ensure a space between the split magnetic cores, a polyimide sheet whose thickness G = 20 mm is fitted into a space between the split magnetic cores . The following Table 18 illustrates, with the fixtures according to the fourth embodiment and comparative example 4, a relationship between the thickness of the cylindrical rotating element and the relationship of lines of magnetic force outside the cylindrical body. The fourth modality satisfies the condition of “R2: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 90%” regardless of the thickness of the cylindrical rotating element. Comparative example 4 is “the ratio of lines of magnetic force outside the cylindrical body” in the event of employing the same cylindrical rotating element in the core with a gap of 0.5 mm according to the fourth embodiment, and does not satisfy “R1: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 70%” in all situations. Table 18


[0312] “The ratio of lines of magnetic force outside the cylindrical body” of comparative example 4 is 0% in all situations. Consequently, the lines of magnetic force do not readily pass over the outside of the cylindrical body, and pass partially through the cylinder. Figure 30 shows the results where the magnetic core was disposed in the hollow part of the cylindrical rotating element, and efficiently the energy conversion at a frequency of 21 kHz was measured.
[0313] Accordingly, with the fixture according to comparative example 4, the reduction in energy conversion efficiency started from 150mm thickness of nickel, and reached 80% at 75mm, and exhibited the same trend as in comparative example 3. With the configuration of comparative example 4, in the case where the thickness of the cylindrical rotating element was set to 75 mm or less, the efficiency of electromagnetic induction heating energy conversion decreased to 80% or less, and has a disadvantageous configuration for fast startup properties with comparative example 3. On the other hand, with the configuration of the fourth mode, the energy conversion efficiency exceeded 95%, and consequently, the fourth mode is advantageous in terms of properties quick start-up according to the same ratio as in the third mode.
[0314] As described above, according to the configuration of the fourth embodiment, with the cylindrical body formed of nickel having high relative permeability, even when decreasing its thickness, the heat generation can be effectively performed in the cylindrical body, and the device of fastening that excels in quick boot properties can be provided.
[0315] Note that, as illustrated in Figures 33A and 33B, in the case where a part protruding from an end face of the cylindrical rotating element of magnetic core 2 is configured not to protrude to a region outside of a virtual face extended from the inner circumferential face of the cylindrical swivel element, in the radial direction of the cylindrical swivel element, this contributes to improved assembly properties. Fifth Mode
[0316] With item “3-3. Magnetic Circuit and Permeance” In the first embodiment, the description has been made so that when iron or the like has to be supplied inside the cylindrical body, the ratio of lines of magnetic force passing over the outside of the cylindrical body has to be controlled. Now the description will be made with respect to a specific example for controlling the ratio of lines of magnetic force passing over the outside of the cylindrical body.
[0317] The present embodiment is a modification of the second embodiment, and differs from the configuration of the second embodiment only in that an iron reinforcing support has been arranged as a reinforcing element. An iron support configured with the minimum cross-sectional area is arranged, and accordingly, the clamping film and pressing cylinder can be suppressed with the highest pressure, and it has an advantage that clamping ability can be improved. The cross-sectional area mentioned here is a cross-section in a direction perpendicular to the generative direction of the cylindrical rotating element.
[0318] Figure 36 is a schematic cross-sectional view of the fixture according to the fifth embodiment. A fastening device A includes a fastening film 1 serving as a rotating cylindrical heating element, a film guide 9 serving as a nip forming element which is in contact with the inner face of the fastening film 1, a metal support 23 configured to suppress the nip part forming element, and a pressing cylinder 7 serving as a pressing member. The metal support 23 is iron with a relative permeability of 500, and a cross-sectional area of 1 mm x 30 mm = 30 mm 2 . The press cylinder 7 forms a nip part N together with the film guide 9 via the fixing film 1. While driving an embossing material P that carries a toner image T using the nip part N, the embossing material P is heated to fix the toner image T onto the recording material P. Press cylinder 7 is pressed against film guide 9 by pressing force at full pressure of around 10 N to 300 N (around 10 to 300 N). 30 kgf) using a bearing unit not shown and pressing unit. Press cylinder 7 is driven by rotation in an arrow direction using a drive source not shown, torque acts on clamping film 1 by frictional force on the nip portion N, and clamping film 1 is driven and rotated. The film guide 9 also has a function serving as a film guide configured to guide the inner face of the fixing film 1, and is configured from polyphenylene sulfide (PPS) which is a heat resistant resin or similar. The materials and cross-sectional areas of the magnetic core and cylindrical body are the same as in the second embodiment, and consequently, when calculating a ratio of lines of magnetic force passing through each region, the results are obtained as in the following Table 19. Table 19 Relation of Lines of Magnetic Force in the Fifth Mode

[0319] With the fifth mode configuration, the ratio of lines of magnetic force outside the cylindrical body is 91.6%, and satisfies the condition of “R1: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 70%”.
[0320] The permeance of each component of the fifth modality is as follows from Table 19. The magnetic core permeance: Pc = 4.5 x 10-7 Km
[0321] The permeance inside the cylindrical body (region between the cylindrical body and magnetic core): Pa = 3.8 x 10-8 + 1.3 x 10-10 + 3.1 x 10-10 Km The permeance of the body cylindrical: Ps = 1.4 x 10-12 Km
[0322] Consequently, the fifth modality satisfies the following relational expression of permeance. Ps + Pa ≤ 0.30 x Pc
[0323] When replacing the expressions mentioned above with magnetic resistance, the following expressions are obtained. The magnetic resistance of the magnetic core: Rc = 2.2 x 106 1/(Km)
[0324] The magnetic resistance inside the cylindrical body is the combined reluctance Ra of the magnetic resistance of the iron support Rt, film guide Rf, and air inside the cylindrical body Rair, and when using the following expression,
Ra = 2.3 x 109 1/(Km) is maintained.
[0325] The magnetic resistance of the cylindrical body Rs is Rs = 3.2 x 109 1/(Hm), and consequently, the combined magnetic resistance Rsa of Rs and Ra is Rsa = 2.3 x 109 1/(Km) if keeps.
[0326] Consequently, the fifth modality configuration satisfies the following relational expression of magnetic resistance. 0.30 x Rsa > Rc
[0327] In accordance with the above, the fixture according to the fifth embodiment satisfies relational expressions of permeance (magnetic resistance), and consequently can be employed as the fixture.
[0328] Figure 37 illustrates a space magnetic equivalent circuit including the magnetic core, coil, cylindrical body, and metal support per unit length. The way of looking at it is the same as in Figure 11B, and consequently, the detailed description of the magnetic equivalent circuit will be omitted. When the lines of magnetic force emitted from one end in the longitudinal direction of the magnetic core are taken to be 100%, 8.3% of these passing through the interior of the metal support and returning to the other end of the core magnetic field, and consequently the lines of magnetic force passing over the outside of the cylindrical body decrease that much. This ratio will be described using the directions of lines of magnetic force and Faraday's law with respect to Figure 38.
[0329] Faraday's Law is “When changing a magnetic field inside a circuit, the induced electromotive force trying to apply current to the circuit occurs, and the induced electromotive force is proportional to the time change of a magnetic flux penetrating vertically in the circuit ”. In the case where the circuit S is arranged near an end part of the magnetic core 2 of the solenoid coil 3 illustrated in Fig. 38, and a high frequency alternating current is applied to the coil 3, the induced electromotive force generated in the circuit S is, according to Expression (2), proportional to the temporal change of lines of magnetic force that penetrate vertically into the interior of the circuit S according to Faraday's Law. That is, when many more vertical components Bfor of lines of magnetic force pass through the circuit S, the induced electromotive force to be generated also increases. However, the lines of magnetic force passing through the interior of the metal support become Bopp components of lines of magnetic force in the opposite direction of the vertical components B of the lines of magnetic force inside the magnetic core. When there are Bopp components of lines of magnetic force from that opposite direction, the "lines of magnetic force penetrating vertically into the circuit" become the difference between Bfor and Bopp, and consequently decrease. As a result of this, there may be a case where the electromotive force decreases, and the efficiency of the conversion decreases.
[0330] Consequently, in the case of arranging a metal element such as a metal support in a region between the cylindrical body and the magnetic core, the permeance within the cylindrical body is reduced by selecting a material having low relative permeability such as stainless steel. austenitic or similar in order to satisfy the following relational expressions of permeance. In the case of arranging an element having high relative permeability in a region between the cylindrical body and the magnetic core of need, the permeance inside the cylindrical body is reduced to the maximum (magnetic resistance inside the cylindrical body is increased) decreasing the area transversal of its element in order to satisfy the following relational expressions of permeance. Comparative Example 5
[0331] The present comparative example differs from the fifth embodiment described above with respect to the cross-sectional area of the metal support. In the case where the cross-sectional area is greater than that of the fifth modality, and is 2.4 x 10-4 m2 which is the quadruple of the fifth modality, when calculating the ratio of lines of magnetic force passing through each region, the calculation results are as in the following Table 20. Table 20 Relation of Lines of Magnetic Force in Comparative Example 5

[0332] With the configuration of comparative example 5, the ratio of lines of magnetic force outside the cylindrical body is 66.8%, and satisfies the condition of “R1: the ratio of lines of magnetic force outside the cylindrical body is equal to or greater than 70%”. At that time, the energy conversion efficiency obtained by the impedance analyzer was 60%.
[0333] Also, the permeance per unit length of each component of comparative example 5 is as follows from Table 20.
[0334] Permeance per unit length of the magnetic core: Pc = 4.5 X 10-7 H-m
[0335] The permeance per unit length inside the cylindrical body (region between the cylindrical body and magnetic core): Pa = 1.5 X 10-7 + 1.3 X 10-10 + 3.1 X 10-10 H-m
[0336] Permeance per unit length of the cylindrical body: Ps = 1.4 X 10-12 H-m
[0337] Consequently, comparative example 5 does not satisfy the following permeance relational expression. Ps + Pa ≤ 0.30 X Pc
[0338] When replacing the expressions mentioned above with magnetic resistance, the following expressions are obtained. The magnetic resistance of the magnetic core: Rc = 2.2 X 106 1/(H-m)
[0339] The magnetic resistance Ra inside the cylindrical body (combined reluctance of the magnetic resistance of the iron support Rt, film guide Rf, and air inside the cylindrical body Rair) is, when that from the following expression, Ra = 6, 6 X 106 1/ (Hm).

[0340] The magnetic resistance Rs of the cylindrical body is Rs = 7.0 X 1011 1/(H-m), and consequently, the combined magnetic resistance Rsa of Rs and Ra is Rsa = 6.6 x 106 1/(H-m).
[0341] Consequently, comparative example 5 does not satisfy the following relational expression of magnetic resistance. 0.30 x Rsa ≥ Rc Sixth Mode
[0342] With cases from the first to the fifth embodiment, the fixture was handled whereby elements and so on within the maximum image region have a transverse configuration in the generatrix direction of the cylindrical rotating element. With a sixth embodiment, the description will be made with respect to a fastening device having an irregular transverse configuration in the generative direction of a cylindrical rotating element. Figure 39 is a fixture described in the sixth embodiment. As a different point from the configurations of the first to the fifth embodiment, a temperature sensing element 24 is provided within (region between the magnetic core and the cylindrical rotating element) of the rotating cylindrical element. Other configurations are the same as in the second embodiment, the fixture includes a fixture film 1 having an electroconductive layer (cylindrical rotating element), magnetic core 2, and nip forming element (film guide) 9.
[0343] If the longitudinal direction of the magnetic core 2 is said to be taken as the X axis direction, the maximum imaging region is a range from 0 to Lp on the X axis. For example, in the case of an apparatus For imaging where the maximum transport region of a recording material is taken as the LTR size of 215.9 mm, Lp has to be set to Lp = 215.9 mm. The temperature sensing element 24 is configured from a non-magnetic material with a relative permeability of 1, the cross-sectional area in a direction perpendicular to the X axis is 5 mm x 5 mm, the length in a direction parallel to the X axis is 10 mm. The temperature sensing element 24 is arranged at a position from L1 (102.95 mm) to L2 (112.95 mm) on the X axis. Now, 0 to L1 in the X coordinate will be called region 1, L1 to L2 where the temperature sensing element 24 exists will be called region 2, and L2 to LP will be called region 3. The transverse configuration in region 1 is illustrated in Figure 40A, and the transverse configuration in region 2 is illustrated in Figure 40B. As illustrated in Figure 40B, the temperature sensing element 24 is housed in the fixing film 1, and consequently becomes an object for calculating magnetic resistance. In order to strictly perform the magnetic resistance calculation, “magnetic resistance per unit length” is individually obtained for region 1, region 2, and region 3, the integration calculation is performed according to the length of each region, and the combined magnetic resistance is obtained by adding these. First, the magnetic resistance per unit length of each component in region 1 or region 3 is illustrated in the following Table 21. Table 21 Transverse Configuration of Region 1 or 3

[0344] The magnetic resistance rc1 per unit length of the magnetic core in region 1 is as follows. rc1 = 2.9 x 106 1/ (H.m)
[0345] Now the magnetic resistance ra per unit length of a region between the cylindrical body and the magnetic core is the combined magnetic resistance of the magnetic resistance per unit length of the rf film guide, and the magnetic resistance per unit length of air inside the rair cylinder. Consequently, this can be calculated using the following expression.

[0346] As calculation results, the magnetic resistance ra1 in region 1, and the magnetic resistance rs1 in region 1 are as follows. ra1 = 2.7 X 109 1/(H•m) rs1 = 5.3 x 1011 1/(H•m)
[0347] Also, region 3 is the same as region 1, and consequently, three types of magnetic resistance with respect to region 3 are as follows. rc3 = 2.9 x 106 1/(H•m) ra3 = 2.7 x 109 1/(H•m) rs3 = 5.3 x 1011 1/(H•m)
[0348] Next, the magnetic resistance per unit length of each component in region 2 is illustrated in the following Table 22. Table 22 Transverse configuration of Region 2

[0349] The magnetic resistance rc2 per unit length of each component in region 2 is as follows. rc2 = 2.9 x 106 1/ (H.m)
[0350] The magnetic resistance ra per unit length of a region between the cylindrical body and the magnetic core is the combined magnetic resistance of the magnetic resistance per unit length of the film guide rf, the magnetic resistance per unit length of the thermistor rt , and the magnetic resistance per unit length of air inside the rair cylinder. Consequently, this can be calculated using the following expression.

[0351] As calculation results, the magnetic resistance ra2 per unit length in region 2, and the magnetic resistance rc2 per unit length in region 2 are as follows. ra2 = 2.7 x 109 1/(H•m) rs2 = 5.3 x 1011 1/(H•m)
[0352] Region 3 is completely the same as region 1. Note that with the magnetic resistance ra per unit length of a region between the cylindrical body and the magnetic core, a reason why ra1 = ra2 = ra3 will be described . With the calculation of the magnetic resistance in region 2, the cross-sectional area of the thermistor 24 increases, and the cross-sectional area of the air inside the cylindrical body decreases. However, with both, the relative permeability is 1, and consequently, the magnetic resistance is the same regardless of the presence or absence of thermistor 24. That is, in the case where a non-magnetic material alone is disposed in the region between the body cylindrical and magnetic core, even when the magnetic resistance calculation is treated as the same as the air, this is sufficient as the accuracy in the calculation. This is because in the case of a non-magnetic material, the relative permeability becomes a value close to 1. On the contrary, in the case of a magnetic material (nickel, iron, stainless steel, or similar), it is desirable to calculate a region where there is a magnetic material and other regions separately.
[0353] The integration of magnetic resistance R[A/Wb/(1/H)] serving as combined magnetic resistance in the generating direction of the cylindrical body can be calculated for the magnetic resistance r1, r2, and r3 1/ (Hm) of each region as follows.

[0354] Consequently, the magnetic resistance Rc[H] of the core in a section from one end of the maximum transport region of the recording material to the other end can be calculated as follows.

[0355] Also, the combined magnetic resistance Ra[H] of a region between the cylindrical body and the magnetic core in a section from one end of the maximum transport region of the recording material to the other end can be calculated as follows .

[0356] The combined magnetic resistance Rs[H] of the cylindrical body in a section from one end of the maximum transport region of the recording material to the other end can be calculated as follows.

[0357] The results of the above calculations performed in each region will be illustrated in the following Table 23. Table 23 Results of the Permeance Integration Calculation in each Region

Rc, Ra and Rs are as follows from Table 23 above. Rc = 6.2 x 108 [1/H] Ra = 5.8 x 1011 [1/H] Rs = 1.1 x 1014 [1/H]
[0358] The combined magnetic resistance Rsa of Rs and Ra can be calculated with the following expression.

[0359] According to the above calculations, Rsa = 5.8 x 1011 [1/H] is obtained, and consequently, the following relational expression is satisfied. 0.30 x Rsa ≥ Rc
[0360] In this way, in case the fixture has an irregular transverse shape in the generative direction of the cylindrical rotating element, it is desirable that the magnetic core is divided into multiple regions in the generative direction of the cylindrical rotating element, the magnetic resistance is calculated to each region thereof, and finally, the combined magnetic permeance or resistance is calculated. However, in the case where an element to be processed is a non-magnetic material, the permeability is substantially the same as the permeability of air, and consequently, this can be calculated by considering it as air. Next, the components that have to be calculated will be described. With respect to a component disposed inside the rotating cylindrical element (electroconductive layer, i.e. a region between the rotating cylindrical element and the magnetic core), and at least a part is included in the maximum transport regions (0 to Lp) of the recording material, the magnetic permeance or resistance has to be calculated. In contrast, with respect to an element arranged outside the cylindrical rotating element, the permeance or magnetic resistance does not have to be calculated. This is because as described above, the induced electromotive force is proportional to the temporal-change of magnetic force lines that penetrate vertically into the circuit according to Faraday's Law, and has no relation to the magnetic force lines outside the circuit. Also, an element arranged outside the maximum transport region of the recording material in the generative direction of the cylindrical rotating element does not affect the heat generation of the cylindrical rotating element (electroconductive layer), it does not have to be calculated.
[0361] While the present invention has been described with respect to the exemplified embodiments, it is understood that the invention is not limited to the exemplified embodiments described. The scope of the following claims accords with the broadest interpretation to encompass all such modifications and equivalent structures and functions.
[0362] This application claims the benefit of Japanese Patent Applications No. 2012-137892 filed June 19, 2012 and No. 2013-122216 filed June 10, 2013, which are incorporated herein by reference.

权利要求:
Claims (9)
[0001]
1. Fixture device configured to fix an image to a recording material by heating the recording material on which the image is formed, comprising: a cylindrical rotating element including an electroconductive layer; a coil configured to form an alternating magnetic field that subjects the electroconductive layer to heating by electromagnetic induction, the coil having a spiral-shaped portion which is arranged on the rotating element such that a spiral axis of the spiral-shaped portion extending along a generative direction of the rotating element; and a core configured to induce lines of magnetic force from the alternating magnetic field, the core being arranged in the spiral portion; wherein the core has a shape that does not loop out of the electroconductive layer, the device being characterized by the fact that a magnetic resistance of the core is, with an area from one end to the other end of the maximum pass region of the image in a recording material in the generative direction, equal to or less than 30% of the combined magnetic resistance consisting of the magnetic resistance of the electroconductive layer and the magnetic resistance of a region between the electroconductive layer and the core, and the electroconductive layer generates heat primarily by a current , which is induced by the magnetic field, flowing in the electroconductive layer in a direction around the circumference of the electroconductive layer.
[0002]
2. Fixing device, according to claim 1, characterized in that the electroconductive layer is formed from at least one of silver, aluminum, austenitic stainless steel, and copper.
[0003]
3. Fixing device, according to claim 1, characterized in that the core projects an external side of the rotating element than an end face of the rotating element in the generatrix direction.
[0004]
4. Fixing device according to claim 3, characterized in that a part of the core which projects an outer side of the swivel element than the end face of the swivel element is, with a radial direction of the swivel element, in an inner side region than a virtual face that extends the inner face of the rotating element in the generating direction.
[0005]
5. Fixing device, according to claim 1, characterized in that an alternating current frequency flowing to the coil is equal to or greater than 21 kHz, but equal to or less than 100 kHz.
[0006]
6. Fixing device, according to claim 1, characterized by the fact that the region of maximum passage of the image is included in a region where the electroconductive layer and the core are superimposed in the generatrix direction.
[0007]
7. Fixing device, according to claim 1, characterized in that the rotating element is a cylindrical film; and wherein the fastening device has a counter member configured to form a nip portion, in which a recording material is conveyed, between the film and itself.
[0008]
8. Fixing device according to claim 7, characterized in that the fixing device includes a nip part forming element configured to form the nip part, which is in contact with the inner face of the film, along with the counter element via the movie.
[0009]
9. Fixing device according to claim 8, characterized in that the fixing device includes a reinforcing element configured to reinforce the nip forming element, which is long in the generative direction, within the film, and a reinforcing element material is austenitic stainless steel.

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法律状态:
2018-12-04| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-12-17| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-07-06| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|

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2021-11-30| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2022-02-01| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 13/06/2013, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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JP2012137892|2012-06-19|

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JP2012-137892|2012-06-19|

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JP2013122216A|JP6223003B2|2012-06-19|2013-06-10|Fixing device|

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JP2013-122216|2013-06-10|

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PCT/JP2013/066901|WO2013191229A1|2012-06-19|2013-06-13|Fixing device|

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