• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    PISTON FOR INTERNAL COMBUSTION ENGINE. The present invention relates to an aluminum alloy piston (64) for an internal combustion engine. In the internal combustion engine, the piston (64) moves back and forth within a sleeve (62) made of gray cast iron or an aluminum alloy. In addition, the piston (64), which is made of silver, silver alloy, copper, or copper alloy, is fitted with a film (72) that covers the scratches (68) that is formed in the piston jacket (66) and there are undulations on the surface of the film (66), formed by protrusions (80) and depressions (78). There is a difference of 8-15 (micro) m between the lowest point of the depressions (78) and the highest point of the protuberances (80). The pitch of the adjacent protuberances corresponds to the pitch of the projections on the scratches (68). In addition, the arithmetic mean roughness (Ra) of the protrusion peaks does not exceed 60 nm.
    公开号:BR112012023574B1
    申请号:R112012023574-5
    申请日:2011-03-16
    公开日:2021-02-17
    发明作者:Ryotaro Takada；Mayumi Saruyama；Yositaka Tsujii
    申请人:Honda Motor Co., Ltd.；
    IPC主号:
    专利说明:

    [0001] [0001] The present invention relates to a piston for an internal combustion engine that experiences an alternating movement inside an internal combustion engine sleeve. Background of the Technique
    [0002] [0002] Cars are driven by tires, which are rotated by the rotating drive power converted from the drive power by an internal combustion engine fueled with fuel. Recently, several attempts have been made to increase the fuel consumption rate (mileage) of internal combustion engines in cars, since a reduction in the volume of fuel consumed makes the engine energy efficient and contributes to the protection of the terrestrial environment.
    [0003] [0003] One of these attempts involves reducing the resistance to sliding between sleeves in an internal combustion engine and the pistons that are alternately moved inside the sleeves. This reduced slip resistance facilitates reciprocating forward and backward movement of the piston. Therefore, the actuation force required for the piston to experience an alternating movement is reduced, resulting in a reduction in the volume of fuel consumed.
    [0004] [0004] The slip resistance can be lowered by depositing a layer containing a highly lubricating substance on a piston sleeve or jacket in order to increase the lubrication capacity of the piston sleeve or jacket. For example, Japan's Public Inspection Patent Publication No. 2009-068584 suggests providing a layer of resin bonding agent with MoS2, C, or the like dispersed above it.
    [0005] [0005] The applicant further suggested, in the Public Patent Open to Japan Public Inspection No. 2003-013802, to form thread marks on a piston shirt, and to develop on the surface of the thread marks a coating of anodic oxide, which is impregnated with a lubricant and a molybdenum disulfide based coating successively in that order. Summary of the Invention
    [0006] [0006] Internal combustion engines contain lubricating oil, which is present in the piston sleeve and jacket. It is required, therefore, that the internal combustion engines not only reduce the slip resistance, but also that they have an excellent capacity to retain this lubricating oil. If the lubricating oil's holding capacity is low, then the internal combustion engines will be subject to blockage.
    [0007] [0007] The general objective of the present invention is to provide a piston for an internal combustion engine of simple structure and that, even so, is able to reduce the resistance to sliding between a piston and a sleeve.
    [0008] [0008] The main objective of the present invention is to provide a piston for an internal combustion engine that is capable of sufficiently retaining lubricating oil.
    [0009] [0009] Another objective of the present invention is to provide a piston for an internal combustion engine that contributes to increase the mileage while avoiding the blocking of the internal combustion engine.
    [0010] [00010] In accordance with an embodiment of the present invention, a piston is provided for an internal combustion engine that is made of aluminum alloy and that moves alternately in a sleeve made of gray cast iron or an aluminum alloy comprising: a coating made of silver, a silver alloy, copper, or a copper alloy, the coating covering line marks (68) on a piston jacket, where: the coating includes a surface that has a corrugation comprising the recesses and the grooves; a difference in height between the lower valleys of the recesses and the higher ridges of the grooves varies from 8 to 15 μm; and a step between the adjacent grooves corresponds to a step between the grooves of the line marks and the ridges of the grooves have a roughness with an arithmetic mean Ra equal to or less than 60 nm.
    [0011] [00011] Until then, a conventional lubricating layer of MoS2 included tiny irregularities on the surface of the ridges of the aforementioned ripples. According to the present invention, the ridges of the corrugation grooves provide a smooth and flat surface as a whole.
    [0012] [00012] When the piston jacket is kept in sliding contact with the sleeve, the ridges of the grooves work with an effective sliding surface. With a lubricating layer of MoS2, with irregularities on the surface of the ridges, therefore, the effective sliding area is small. On the other hand, according to the present invention, the smooth surface mentioned above operates as an effective sliding surface and, thus, the sliding surface area is expressive. According to the present invention, therefore, the stresses acting on the sliding surface are correctly distributed. Consequently, the resistance to friction between the piston jacket and the sleeve is reduced.
    [0013] [00013] As described above, the resistance to friction between the piston liner and the sleeve is reduced by the fact that the ridges of the ripple grooves on the liner of the piston liner provide a smooth and flat surface as a result of exhibiting a roughness with an arithmetic mean Ra equal to or less than 60 nm.
    [0014] [00014] The sum of the thermal conductivity of a sleeve interface and the thermal conductivity of a piston jacket interface is equal to or greater than 350 W / m.K. Therefore, the heat from the friction generated between the sleeve and the piston is quickly diffused or transferred. Thus, the region between the sleeve and the piston is prevented from being heated to a high temperature. Since silver, silver alloy, copper or copper alloy, which can form the coating, have high melting points, the coating can easily be maintained in a solid phase state, even in the presence of frictional heat. For the reasons set out above, the piston liner is prevented from adhering.
    [0015] [00015] The force required to make the piston slide against the sleeve is reduced by the fact that, since the absolute value of the difference between the respective Young modules of the piston and the sleeve is equal to or greater than 10 GPa, the The sliding interface of the piston jacket will be subject to elastic deformation, allowing minuscule surface irregularities to be displaced and smoothed when the loads are applied. Therefore, when the piston slides against the sleeve, the shear force generated along the direction of such a sliding movement or, in other words, the sliding resistance, is reduced.
    [0016] [00016] In addition, as the lubricating oil is retained in the recesses of the corrugation, the piston has an excellent lubricating oil retention capacity.
    [0017] [00017] Slip resistance is therefore prevented from increasing. In addition, as the piston liner is prevented from adhering, the piston liner develops a smooth friction surface, resulting in reduced surface pressure. As the slip resistance between the piston and the sleeve is reduced, the slip region is prevented from being damaged, such as scratches and scrapes.
    [0018] [00018] The smooth friction surface, which is produced as described above, increases the load (hereinafter referred to as a border transition load) required to establish contact between the piston jacket and the sleeve. This implies that the piston sleeve and shirt will not be in direct contact with each other unless an expressive load is applied.
    [0019] [00019] Therefore, it is easy to retain the lubricant between the sleeve and the piston sleeve. This also facilitates the block between the sleeve and the piston sleeve.
    [0020] [00020] The coating may comprise a metallic layer made of silver or copper. However, the coating may also comprise a layer in the form of a sintered body made up of silver particles, or an alloy layer containing silver. Suitable examples of such a silver alloy include an alloy of silver and brass, an alloy of silver and copper, etc.
    [0021] [00021] In any proportion, if the coating is made of a silver alloy, then the purity of the silver in the coating is preferably equal to or greater than 60%. The purity of the silver thus selected is effective in reducing friction loss. More preferably, the purity of the silver in the coating is equal to or greater than 80%.
    [0022] [00022] The coating preferably has a thickness ranging from 0.5 to 100 μm. If the coating is excessively reduced in thickness, as the coating is worn in a relatively short period of time, it is difficult to transform the friction surface of the crests of the line marks (the ripple streaks) into a smooth surface that exhibits a roughness of surface equal to or less than 60 nm. On the other hand, if the liner is excessively expressive, as the liner weight is increased, a great driving force is required to alternately move the piston.
    [0023] [00023] The line marks, preferably, have a height ranging from 0.001 to 0.1 mm, and the pitch between adjacent grooves of the line marks, preferably, varies from 0.1 to 0.5 mm. With this way of dimensioning the line marks, the contact area between the piston sleeve and the sleeve is in a suitable range. Therefore, the slip resistance is prevented from increasing, and the occurrence of blockages is avoided. Brief Description of Drawings
    [0024] [00024] Figure 1 is a schematic side longitudinal view of a slip friction tester;
    [0025] [00025] figure 2 is a graph showing a relationship between friction coefficients determined with the use of discs and test pieces, and the values produced by subtracting the Young modules from the test modules of the Young modules from the disks;
    [0026] [00026] figure 3 is a fragmented and enlarged cross-sectional view of the sliding surfaces of a first member and a second member, which exhibit low thermal conductivity;
    [0027] [00027] figure 4 is a fragmentary and enlarged cross-sectional view of the sliding surfaces of a first member and a second member, which exhibit good thermal conductivity;
    [0028] [00028] figure 5 is an enlarged view of a ridge of the convexities of the first member and the second member shown in figure 3;
    [0029] [00029] figure 6 is an enlarged view of a ridge of the convexities of the first and second members shown in figure 4;
    [0030] [00030] figure 7 is a graph showing a relationship between the sums of the thermal conductivities of the discs and test pieces, and the boundary transition loads of the discs and test pieces;
    [0031] [00031] figure 8 is a vertical and fragmentary cross-sectional view of an internal combustion engine, including a sleeve and a piston according to an embodiment of the present invention;
    [0032] [00032] figure 9 is an enlarged cross-sectional view of a region of the surface layer of a piston jacket of a piston;
    [0033] [00033] figure 10 is an enlarged cross-sectional view of a region of the surface layer of a piston jacket that includes a lubricating layer made of metal;
    [0034] [00034] figure 11 is an enlarged cross-sectional view of a region of the surface layer of a piston jacket that includes a lubricating layer made of sintered Ag particles;
    [0035] [00035] figure 12 is a graph showing a relationship between the purities of silver, the thermal conductivities of silver coatings (lubricant layers), and friction losses in an internal combustion engine;
    [0036] [00036] figure 13 is a graph showing how the wear depth of a liner is modified when an internal combustion engine operates at 6800 rpm;
    [0037] [00037] figure 14 is a diagram showing a roughness curve of the ripple of a silver coating (lubricant layer) before its alternating movement (sliding movement);
    [0038] [00038] figure 15 is a diagram showing a roughness curve of the ripple of a silver coating (lubricant layer) after its alternating movement (sliding movement);
    [0039] [00039] figure 16 is a diagram showing a roughness curve of the ripple of a MoS2 coating (lubricant layer according to the previous technique) after its alternating movement (sliding movement);
    [0040] [00040] Figure 17 is a graph showing a relationship between rotation friction and friction loss in an internal combustion engine, for cases where pistons with multiple lubricant layers in the piston liners are moved alternately;
    [0041] [00041] Figure 18 is a graph showing, by way of comparison, the areas of the regions, which operate as effective sliding surfaces, of the silver coatings, after pistons with various silver coatings (lubricating layers) on the piston liners are alternately moved;
    [0042] [00042] figure 19 is a graph showing a relationship between rotation speeds and the reasons for reducing friction losses in an internal combustion engine, for cases where pistons that have several lubricating layers in the piston liners are alternately moved; and
    [0043] [00043] figure 20 shows the rotation speeds and the reasons for reducing friction losses in an internal combustion engine, for the cases in which the pistons that have several lubricating layers in the piston liners are moved alternately under test conditions , which differ from those in figure 19. Description of Modalities
    [0044] [00044] A piston for an internal combustion engine according to a preferred embodiment of the present invention will be described in detail below with reference to the attached drawings.
    [0045] [00045] First, a relationship between the respective Young modules and a friction coefficient between two objects will be described below.
    [0046] [00046] As shown in figure 1, when two objects slide against each other, their friction coefficient can be measured by means of a slip friction tester 10. The slip friction tester 10 will be briefly described below. The slip friction tester 10 includes a base 12, along with an arm 14 and a support 16 that are mounted on the base 12.
    [0047] [00047] The support 16 has a recess for the housing 12 defined in its upper end surface on which a turntable 20 is accommodated. The turntable 20 is rotated by an illustrated rotary drive mechanism (for example, a motor). A support axis 22 projects centrally from an upper end surface of the turntable 20.
    [0048] [00048] The arm 14 has a vertical member 24, which is erected substantially vertically from the base 12, and a support 26, which is curved from the vertical member 24 towards the base 12 and extends above the base 12 .
    [0049] [00049] A compression shaft 28 is vertically movably supported on the support 26. The compression shaft 28 has an apical end with a compression member 30 fitted over it, the compression member 30 having a slightly larger diameter than the axis compression ratio 28.
    [0050] [00050] The loads applied from a test piece 32 (which will be described later) on the compression shaft 28 are detected by a load cell 34. An indicator to indicate the detected load is placed on the top of the load cell 34 .
    [0051] [00051] The support shaft 22 supports a disc 38. More specifically, the disc 38 has an insertion orifice for penetration 40 defined centrally to the disc. The support axis 22 on the rotary table 20 is inserted into the insertion hole 40. The disc 38 is positioned on the rotary table 20. With the rotation of the rotary table 20, the disc 38 rotates in unison with the rotary table 20.
    [0052] [00052] The test piece 32 is interposed between the disc 38 and the compression member 30. The slip friction tester 10 serves to determine the friction coefficient between the test piece 32 and the disc 38.
    [0053] [00053] More specifically, after the disc 38 has been placed on the rotary table 20, with the support shaft 22 on the rotary table 20 being inserted into the insertion hole 40 in the disc 38, the test piece 32 is positioned on the disc 38. The compression shaft 28 is then lowered, causing the compression member 30 to be compressed against the test piece 32 under a prescribed pressure.
    [0054] [00054] The rotary table 20 is then rotated by a rotary drive mechanism, rotating the disc 38. As a result, the disc 38 begins to slide against the test piece 32.
    [0055] [00055] At that moment, the load, which is transmitted from the test piece 32 to the compression shaft 28 and to the compression member 30 is detected by the load cell 34, and the load is indicated by the indicator 36.
    [0056] [00056] The friction coefficient is calculated based on the determined load and the rotating actuation force of the rotating actuation mechanism at the moment when the disc 38 starts to rotate.
    [0057] [00057] Figure 2 is a graph showing a relationship between friction coefficients determined using discs 38, which are made of AC2B (JIS indicative of aluminum alloy) or SKD11 (JIS indicative of a stainless steel), and parts tests of various materials, and the values produced by subtracting the Young modules from the test pieces of the Young modules of the 38 disks. In figure 2, the marks in the form of squares (■) represent the results of the 38 disks made of AC2B, while the diamond-shaped marks (♦) represent the results of the 38 discs made of SKD11. The materials of the test pieces 32 are shown in figure 2. Figure 2 also shows the individual results obtained when the respective test pieces 32 of the same material are measured a plurality of times. Figure 7 also shows these individual results.
    [0058] [00058] It can be seen from figure 2 that the friction coefficient decreases as the absolute value of the difference between Young's modules increases. The reason for this phenomenon seems to be that, as the difference between Young's modules increases, the sliding surfaces are elastically deformed relatively easily, resulting in the reduction of the shear force through the sliding movement, so that their resistance to sliding is reduced. This implies that, since the difference between Young's modules is greater, the force required to cause the relative sliding between two objects is less.
    [0059] [00059] On the other hand, if the two objects exhibit good thermal conductivity, the frictional heat generated when the objects slide against each other is transferred quickly. Therefore, the two objects that slide against each other are less likely to adhere to each other. Other details concerning this phenomenon will be described later.
    [0060] [00060] Figure 3 shows schematically two objects, that is, a first member 50 and a second member 52, with their respective sliding surfaces (sliding regions). Before the first member 50 and the second member 52 are slid against each other, the sliding surfaces of these members observed under a microscope are not smooth, but irregular, as they contain a series of concavities 54a, 54b and convexities 56a, 56b. When the second member 52 slides against the first member 50, local portions of the convexities 56a on the sliding surface of the first member 50 and the convexities 56b of the sliding surfaces of the second member 52 are brought into contact.
    [0061] [00061] When the local portions of convexities 56a, 56b are brought into contact, these portions generate heat locally. If the thermal conductivity of the first member 50 and the second member 52 is very low, then the heat generated tends to remain in the first member 50 and the second member 52, rather than being diffused. Therefore, the local portions of convexities 56a, 56b that are brought into contact, start to exhibit elevated temperature. If the first member 50 and the second member 52 have a low melting point, then the local portions of convexities 56a, 56b, which are brought into contact, will be melted.
    [0062] [00062] When the local portions solidify again, the local portions will be fully unified, or will adhere to each other, resulting in the adhered region 58, as shown in figure 3. This phenomenon tends to occur as the thermal conductivity of the first and second limb 50, 52 is lower, or as the melting point of the first member 50 and the second member 52 is lower.
    [0063] [00063] If adhesion occurs between convexities 56a, 56b, a force is required to separate them from each other. When the convexities 56a, 56b, which have been moved away from each other by sliding the second member 52 against the first member 50, are brought into contact with each other again, the convexities 56a, 56b will again tend to adhere to each other, and then they will be away from each other. Therefore, considerable force is required to cause the second member 52 to slide against the first member 50. As the adhered region 58 is repeatedly corrupted to separate the convexities 56a, 56b, the sliding surface of the first member 50 or the sliding surface of the second member 52 is damaged and thus no smoothly worn surfaces are formed on the first member 50 and the second member 52. In other words, the convexities 56a, 56b, exhibit a sliding structure where an incoming load is supported by the bulges.
    [0064] [00064] If the thermal conductivity of the first member 50 and the second member 52 is considerable, then the heat generated by the adhered region 58 is diffused to the first member 50 or to the second member 52. Thus, the adhered region 58 is prevented from having its temperature increased, and the convexities 56a, 56b, placed in contact with each other, are ground up without adhering to each other, as shown in figure 4.
    [0065] [00065] As the first member 50 and the second member 52 are easily worn, relatively smooth sliding surfaces are produced. The sliding surface areas of the first member 50 and the second member 52 are enlarged, resulting in reduced slip resistance. As the regions adhered to each other are not repeatedly corrupted, scratches and scratches are prevented from occurring on the sliding surface of the first member 50 and the sliding surface of the second member 52, that is, the sliding surfaces are prevented from being damaged .
    [0066] [00066] As the absolute value of the value produced by subtracting the Young's modulus from the second member 52 from the Young's modulus from the first member 50 increases, the convexities 56a, 56b are likely to be elastically deformed, making the sliding surfaces of the first member smoother. 50 and the second member 52, that is, resulting in a greater reduction in slip resistance.
    [0067] [00067] From the above description it is possible to understand that, in conventional sliding surfaces, after the first member 50 and the second member 52 have been slid against each other, the convexity ridges 56a, 56b are not flat, they contain small irregularities in their surfaces, as shown in figure 5 in microscopic view.
    [0068] [00068] On the other hand, if the sum of the thermal conductivities of the first member 50 and the second member 52 is considerable, and assuming that the first member 50 and the second member 52 have high melting points, then the heat generated when the first member 50 and second member 52 are eroded is rapidly diffused and transferred, and first member 50 and second member 52 are maintained in a solid phase state. As their sliding surfaces are less likely to adhere to each other, flat, worn surfaces are produced on the first member 50 and the second member 52. As a result, the load required to bring the first member 50 and the second member 52 into direct contact, i.e. that is, the borderline transition load is considerable.
    [0069] [00069] As the sliding surfaces are smoother, the load applied to the sliding surfaces is likely to be spread substantially uniformly. Thus, if there is a lubricant between the first member 50 and the second member 52, the forces that tend to shear the lubricant are reduced. Therefore, the lubricant is suitably retained between the first member 50 and the second member 52.
    [0070] [00070] In addition to providing smooth and flat sliding surfaces, the first member 50 and the second member 52 must be produced from selected materials that provide smaller original undulations and a smaller difference in Young's modulus, so that the crests of the convexities 56a, 56b are smoother after the first member 50 and the second member 52 have been slid against each other, as shown in figure 6.
    [0071] [00071] Figure 7 is a graph showing a relationship between the sums of thermal conductivities of the loads of the boundary transition of the two objects, that is, the disks (first members) produced in AC2B or SKD11, and the test pieces 32 (seconds members) produced in different materials. The graph includes a horizontal geometric axis that represents the sums of the thermal conductivities of the discs 38 and the test pieces 32, and a vertical geometric axis that represents the loads of the boundary transition of the discs 38 and the test pieces 32. In figure 7, the marks in the form of squares (■) represent the results of the 38 discs made of AC2B, while the diamond-shaped marks (♦) represent the results of the 38 discs made of SKD11. The materials of the test pieces 32 are shown in figure 7.
    [0072] [00072] From figure 7 we can understand that, as the sum of the thermal conductivities increases, the load of the border transition also increases, that is, a considerable load is necessary to place the disc 38 (first member) and the test piece 32 (second member) in direct contact with each other.
    [0073] [00073] In other words, if the sum of the thermal conductivities of the first member 50 and the second member 52 is regulated to a value equal to or greater than 350 / mK, and the first member 50 and the second member 52 are produced in metals with high melting points, it will be easy to maintain a predicted gap between the first member 50 and the second member 52, and a lubricant can be retained within that gap.
    [0074] [00074] For the above reasons, the lubricant is suitably retained between the first member 50 and the second member 52 in order to provide a lubricating capacity between the first member 50 and the second member 52.
    [0075] [00075] According to the present invention, based on the above results, it is possible to provide an internal combustion engine, which is shown in a fragmented way in figure 8, in which the sum of the thermal conductivities of the sliding regions of the members that slide between itself is set to be equal to or greater than 350 W / mK, and in which the absolute value of the difference between the respective Young modules of the sliding regions is adjusted to be equal to or greater than 10 GPa. The details of the internal combustion engine, shown fragmentarily in figure 8, will be described below.
    [0076] [00076] Figure 8 is a vertical and fragmentary cross-sectional view of an internal combustion engine. The internal combustion engine includes a cylinder block 59 which, in general, contains a plurality of holes 60 acting as cylinders, and a plurality of sleeves 62 inserted in the respective holes 60. An internal combustion engine piston (hereinafter simply “Piston”) 64 is subjected to an alternating movement in each of the sleeves 62.
    [0077] [00077] Piston 64 has a piston jacket 66, which is maintained in sliding contact with a surface of the inner wall of the sleeve 62. The sleeve 62 and the piston jacket 66 together form a sliding structure.
    [0078] [00078] Sleeve 62 in general is produced in gray cast iron (called sleeve FC). However, sleeve 62 can be made of an aluminum alloy (called an Al sleeve). The inner wall surface of the sleeve 62 can be a surface treated with a Ni-SiC deposition coating, or a diamond-like carbon coating (DLC).
    [0079] [00079] The piston 64 is produced in AC2A, AC2B, AC4B, AC4C, AC4D, AC8H or Al100 (an aluminum alloy defined by JIS), or an aluminum alloy, for example, an Al-Copper alloy or similar. As shown in Figure 9, piston liner 66 has line marks 68 extended along its circumferential direction. Line marks 68 include splines 70 which have a height H in the range of 0.001 to 0.1 mm. The gap between adjacent grooves 70, i.e., step P, is in the range of 0.1 to 0.5 mm. Height H is preferably in the range of 0.008 to 0.012 mm, and step P is preferably in the range of 0.25 to 0.3 mm.
    [0080] [00080] The piston jacket 66 constructed in this way is coated with a lubricating layer (silver coating) 72. The lubricating layer 72 has a thickness that is not limited to any particular value. However, if the thickness of the lubricating layer 72 is excessively reduced, then the lubricating layer 72 will wear out in a relatively short period of time, tending to expose the piston jacket 66 as a base. On the other hand, if the thickness of the lubricating layer 72 is excessively wide, then the lubricating layer 72 becomes so heavy as to require considerable driving force to cause the piston 64 to be moved alternately. To avoid the above difficulties, the thickness of the lubricating layer 72 is preferably in the range of 0.5 to 100 μm.
    [0081] [00081] According to the present modality, the lubricating layer 72 contains silver (Ag). The lubricating layer 72 can be provided as a metallic layer of Ag, as shown in figure 10, which illustrates a region of the surface layer of the piston jacket 66 on an enlarged scale. The lubricating layer 72 can be formed by processing the piston before it is mounted on an internal combustion engine, according to a caustication process that uses an alkaline solution, a cleaning process that uses an oxide, two zinc replacement processes , followed by a deposition process. The deposition process may employ a bath with deposition of silver cyanide.
    [0082] [00082] Alternatively, as shown in figure 11, the lubricating layer 72 may be in the form of a sintered body produced from fine silver particles as the starting material. In figure 11, the lubricating layer 72 is illustrated as a fine particle agglomerate, indicating the fine particles as starting material. However, in reality, the lubricating layer 72 comprises a three-dimensional structure formed by the melting of fine particles.
    [0083] [00083] The fine particles preferably comprise so-called nanoparticles that have an average diameter ranging from 1 to 80 nm. A lubricating layer 72 formed by nanoparticles is strongly attached to the piston jacket 66 to prevent removal of the lubricating layer 72 from the piston jacket 66.
    [0084] [00084] The nanoparticles are dispersed in a suitable solvent (preferably a polar solvent), such as, for example, terpineol, nonanol, ethylene glycol, propylene glycol, monomethyl ether acetate, methyl ethyl ketone, or the like, in order to prepare a slurry with a viscosity of less than 10 cp.
    [0085] [00085] Then, the piston jacket 66 is coated with a semi-fluid paste using a known coating process, such as printing on canvas or the like.
    [0086] [00086] Piston 64, which has been coated with the slurry, is heated to a temperature ranging from 160 to 240 ° C. When the slurry is heated, the solvent contained in that slurry is volatilized and the nanoparticles are fused together. In other words, the slurry is sintered to result in a sintered body of silver particle that acts as the lubricating layer 72.
    [0087] [00087] The use of nanoparticles makes it possible to form a coating by sintering nanoparticles at a relatively low temperature in the range of 160 to 240 ° C. Therefore, the piston jacket 66, which is made of aluminum alloy, is prevented from being heated to a high temperature, therefore, its mechanical resistance is prevented from being adversely affected.
    [0088] [00088] To increase the bond strength between the lubricating layer 72 and the piston liner 66, an intermediate layer can be intercalated between the lubricating layer 72 and the piston liner 66. The intermediate layer can be produced in a material such as resin polyimide, polyamideimide resin, epoxy resin, nylon 6 resin, nylon 6.6 resin, or the like.
    [0089] [00089] To form the silver particle lubricating layer 72 as a starting material, a material is preferably selected as a solvent that is capable of expanding the resin of the intermediate layer, for example, N-methylpyrrolidone, polyvinyl pyrrolidone, trichlorethylene, carbon tetrachloride , or the like, to produce the slurry. When the intermediate layer is coated with the slurry to form the lubricating layer 72, an expansion of the intermediate layer due to the solvent occurs, forming a mixed layer where the silver particles are dispersed at an interface between the intermediate layer and the slurry. The mixed layer develops and produces an anchoring effect between the intermediate layer and the lubricating layer 72 in order to firmly attach the lubricating layer 72 to the intermediate layer.
    [0090] [00090] The lubricating layer 72 may comprise a silver alloy deposition layer or fine silver alloy particles may be used in place of the fine silver particles. In that case, the suitable silver alloy includes an Ag-Sn alloy and an AgCobre alloy.
    [0091] [00091] The sum of the thermal conductivities of the lubricating layer 72 and the FC sleeve or the Ag sleeve is equal to or greater than 350 W / m.K. The absolute value of the difference between the Young modulus of the lubricating layer 72 and the Young modulus of the FC sleeve or the Ag sleeve is equal to or greater than 10 GPa.
    [0092] [00092] In any of the lubricating layers 72 above, the silver contained preferably has a purity represented by a value equal to or greater than 60% by weight. If the purity of the silver is less than 60% by weight, the thermal conductivity of the lubricating layer 72 is slightly lower, making it difficult to form a smooth worn surface, with a tendency for the lubricating layer 72 to be less effective in reducing friction loss ( Psf) in the internal combustion engine.
    [0093] [00093] As seen in figure 12, if the purity of the silver is equal to or greater than 80%, the rate of reduction of thermal conductivity and the rate of reduction of friction loss are constant. Therefore, it is particularly preferred that the purity of the silver is adjusted to match or be above 80% by weight.
    [0094] [00094] The purity of silver is defined as "the weight percentage of silver contained in lubricant layer 72". If the lubricating layer 72 is formed by a deposition process (see figure 10), then the component contained in the lubricating layer 72 is practically pure silver, and therefore the purity of the silver is about 100%. If the lubricating layer 72 is formed by a silver alloy, then the purity of the silver is determined as the weight percentage of the silver contained in the lubricating layer 72. If the lubricating layer 72 (see figure 11) is formed as a sintered body after the piston jacket 66 has been coated with silver particles (nanoparticles), then the purity of the silver is defined as the proportion of particle in the slurry.
    [0095] [00095] The lubricating layer 72 may comprise a copper deposition coating, a coating in the form of a sintered body of fine copper particles, a deposition coating of a copper alloy, or a coating in the form of a sintered body of particles thin copper alloy. At any rate, the sum of the thermal conductivities of the lubricating layer 72 and the FC sleeve or Al sleeve is equal to or greater than 350 W / mK, and the absolute value of the difference between the Young modulus of the lubricating layer 72 and the modulus of Young of sleeve FC or sleeve Al is equal to or greater than 10 GPa. The purity of copper in the copper alloy is preferably equal to or greater than 70%, more preferably, greater than or equal to 80%. Similar to the definition for silver purity, copper purity is defined as “the percentage by weight of copper contained in lubricant layer 72”.
    [0096] [00096] The shape corresponding to the shape of the line marks 68 (see figure 9) on the piston jacket 66 is transferred to the upper terminal surface of the lubricating layer 72. More specifically, a corrugation 82 containing the recesses 78 and the grooves 80 aligned to the recesses and grooves of the line marks 68 is formed on the lubricating layer 72. The difference in height between the lower valleys of the recesses 78 and the highest ridges of the 80pf grooves is in the range of 0.001 to 0.1 mm, and more preferably, it is in the range of 0.008 to 0.012 mm. In addition, the gap between adjacent grooves 80, i.e., a step P, is preferably in the range of 0.1 to 0.5 mm, and more preferably, in the range of 0.25 to 0.3 mm.
    [0097] [00097] Lubricating oil (not shown) is present between piston liner 66 or lubricant layer 72, which are formed as described above, and sleeve 62. When the internal combustion engine is in operation, piston 64 is it moves alternately and vertically inside the sleeve 62, as shown in figure 8. The expression “the internal combustion engine is in operation” implies that the fuel is ignited in the combustion chamber.
    [0098] [00098] While the piston 64 is subjected to reciprocating movement, the corrugation 82 (not shown) of the lubricating layer 72 is maintained in sliding contact with the inner wall surface of the sleeve 62. Thus, the ridges of the grooves 80 of the corrugation 82 are worn out evenly.
    [0099] [00099] When the internal combustion engine operates in a predicted period of time, the ridges are flattened to the point where this is no longer possible. More specifically, as shown in figure 13, the wear depth remains unchanged over time. In other words, the wear depth reaches a saturated volume. Figure 13 shows how the wear depth is modified when the internal combustion engine operates at 6800 rpm. Figure 13 shows that the wear depth reaches a saturated value in about 20 minutes. Then, the ‘” operation until the wear depth reaches a saturated volume ”can be expressed as an“ initial operation ”.
    [0100] [000100] The roughness curve of the undulation 82 before its initial operation, and the roughness curve of the undulation 82 after the initial operation are respectively shown in figures 14 and 15. From the comparison between figures 14 and 15, it will be understood whereas, while the ridges of the ridges 80 of the undulation 82 before the sliding movement are sharp, the ridges of the ridges 80 of the undulation 82 after the initial operation, and when the wear depth is saturated, have a flat and smooth surface. After its sliding movement, the flat surface of the ridges of the grooves 80 of the lubricating layer 72 acts as an effective sliding surface.
    [0101] [000101] When the arithmetic mean roughness Ra is measured with respect to the ridges, which have been worn to form a flat surface, it is confirmed that the lubricating layer 72, which is in the form of a copper deposition coating, has an arithmetic mean roughness Ra equal to about 55 nm, while lubricant layer 72, which is in the form of a silver deposition coating, has an arithmetic mean roughness Ra equal to about 38 nm, each less than 60 nm. The difference in height between the lower valleys of the recesses 78 and the higher ridges of the grooves 80 is in the range of 8 to 15 μm.
    [0102] [000102] Figure 16 shows a roughness curve of the ripple 82 of a conventional lubricant layer in a piston jacket, after the piston has been alternately moved by the operation of an internal combustion engine. The lubricating layer is 6 μm thick, with MoS2 particles dispersed in a polyamideimide binder resin. The internal combustion engine operates for a period of time that is identical to the time period of the initial operation of the internal combustion engine that incorporates the piston 64.
    [0103] [000103] As shown in figure 16, a conventional lubricating layer is recognized as having tiny surface irregularities in the ridges of the ripple grooves. More specifically, the ridges of the grooves are not worn to form a flat surface after their sliding movement. The arithmetic mean roughness Ra of the ridges is at least 130 nm at most 140 nm, which is significantly greater than 60 nm. Only the smooth regions of the ridges of the grooves operate as an effective sliding surface.
    [0104] [000104] As readily understood by comparing the roughness curves above, according to the present modality, which exhibits the lubricating layer 72 and in which the ridges of the grooves 80 are worn to form a smooth surface as a whole, the area of the region (hereinafter also called an effective sliding surface) that functions as an effective sliding surface is greater than in the case of the conventional lubricant layer. When the internal combustion engine is operated again after its initial operation, that is, when the ridges of the grooves slide again against the sleeve 62, the tension per unit area, which acts locally on the effective sliding surface, is already reduced that the stresses are properly distributed due to the large area of the effective sliding surface.
    [0105] [000105] According to the present modality, depending on the appropriate distribution of stresses, the friction between the piston jacket 66 and the sleeve 62 is further reduced. This reduced friction also contributes to the reduction of friction loss.
    [0106] [000106] Furthermore, as the step P of the line marks 68 and, therefore, that of the ripple 82 is preferably in the range of 0.1 to 0.5 mm, and more preferably in the range of 0.25 to 0.3 mm, and the height H of the splines 70 is preferably in the range of 0.001 to 0.1 mm, and more preferably in the range of 0.008 to 0.012 mm, the contact area between the piston liner 66 and the sleeve 62 is in a range proper. Consequently, slip resistance is easily prevented from increasing and blocking is easily prevented from occurring.
    [0107] [000107] Figure 17 shows the friction loss (Psf) of an internal combustion engine, at the moment when the piston 64 is moved alternately, the piston jacket 66 including a lubricating layer 72 comprising a deposition layer an Ag-Cu alloy (80% silver purity) with a thickness of 6 μm, a lubricating layer 72 comprising an Ag-Cu alloy deposition layer (60% silver purity) with a thickness of 6 μm, or a lubricating layer 72 comprising a Cu deposition layer (100% copper purity) with a thickness of 6 μm. The piston jacket 66 also displays line marks 68 which include grooves 70 with a height H of 0.01 mm and a pitch P of 0.3 mm. In addition, figure 17 shows the friction loss of an internal combustion engine when the piston is moved alternately, the piston jacket including a conventional lubricant layer that has a thickness of 6 μm with dispersed MoS2 particle in a polyamideimide binder resin. It is clear from figure 17 that, at rotational speed, the friction loss of piston 64 is less than the friction loss of the piston with the lubricating layer containing MoS2.
    [0108] [000108] Figure 18 is a graph showing, by way of comparison, the effective sliding surfaces after piston 64 has been alternately moved, for the case where piston liner 66 has a lubricating layer 72 that comprises a deposition layer an Ag-Cu alloy (80% silver purity) and 6 μm thick, or a lubricating layer 72 comprising an Ag-Cu alloy deposition layer (60% silver purity) and with a thickness of 6 μm, and where the piston 64 has line marks 68 as described above. Also shown is the effective sliding surface after the piston has been moved alternately, for the case where the piston jacket includes a lubricating layer that is 6 µm thick with MoS2 particles dispersed in the polyamideimide. The effective sliding surface of the MoS2 lubricating layer is assumed to be equal to 1, and the ratios of the effective sliding surfaces are illustrated accordingly.
    [0109] [000109] From figure 18 it is possible to observe that the effective sliding surface of the lubricating layer 72 containing Ag is larger than the effective sliding surface of the Mo lubricating layer. The surface pressure of the lubricating layer 72, which has a silver purity of 80%, can be reduced by 64% of the surface pressure of the Mo lubricating layer. In addition, the surface pressure of the lubricating layer 72 which has a silver purity of 60% can be reduced by 19% of the surface pressure of the Mo lubricating layer.
    [0110] [000110] With the above results, we can evidence that the piston 64 which has a lubricant layer 72 containing Ag can be easily moved alternately when subjected to relatively small forces, in other words, the piston 64 has a low slip resistance. That is, the structure above makes it possible to reduce the slip resistance between piston 64 and sleeve 62. As a result, the driving force required to alternately move piston 64 can be reduced.
    [0111] [000111] Figure 19 shows the reasons for the reduction of friction losses in relation to the rotation speeds of an internal combustion engine, against the reference data concerning a piston with a lubricating layer containing MoS2.
    [0112] [000112] Figure 20 shows the reasons for the reduction of friction losses in relation to the rotation speeds of an internal combustion engine in the test conditions, which differ from the conditions of figure 19. In figure 20, the reduction ratios are also shown against the piston reference data for the case where the lubricant layer contains MoS2.
    [0113] [000113] In figures 19 and 20 it is understood that, at any speed of rotation, the reasons for reducing the frictional losses of the pistons 64, in cases where the lubricating layer 72 contains Ag or where the lubricating layer 72 contains Cu, are greater than the ratio of reduced piston friction loss in the case where the lubricant layer contains MoS2. It is clearly observed that the structure above is capable of increasing the mileage, regardless of the rotation speed of the internal combustion engine.
    [0114] [000114] It was also found that a lubricating layer 72 in the form of a sintered body, which is produced from an initial material of the silver particles that have a diameter of 30 nm (88% purity), produces results indicating that the surface pressure is lower and the friction loss reduction ratio is greater than in the case of a lubricating layer containing MoS2.
    [0115] [000115] The present invention is not restricted to the above modality, and several changes can be practiced in the modality without deviating from the scope of the invention.
    权利要求:
    Claims (5)
    [0001]
    Piston (64) for an internal combustion engine that is made of an aluminum alloy and is reciprocally movable within a sleeve (62) made of gray cast iron or an aluminum alloy comprising: a coating (72) made of silver or a silver alloy with silver having a value equal to or greater than 60% by weight, the coating (72) covering thread marks (68) on a piston shirt (66) , characterized by the fact that: the coating (72) includes a surface that has a corrugation comprising the recesses (78) and the grooves (80); a difference in height between the lower valleys of the recesses (78) and the higher ridges of the grooves (80) varies from 8 to 15 μm; and a pitch between the adjacent grooves (80) corresponds to a pitch between the grooves of the line marks (68) and the ridges of the grooves (80) have a roughness with an arithmetic mean Ra equal to or less than 60 nm.
    [0002]
    Piston (64) according to claim 1, characterized in that the coating (72) comprises a sintered body of silver particles.
    [0003]
    Piston (64) according to claim 1 or 2, characterized in that the silver purity of the coating (72) is equal to or greater than 80% by weight.
    [0004]
    Piston (64) according to any one of claims 1 to 3, characterized in that the coating (72) has a thickness ranging from 0.5 to 100 μm.
    [0005]
    Piston (64) according to any one of claims 1 to 4, characterized in that the line marks (68) have a height ranging from 0.001 to 0.1 mm, and the pitch between the adjacent grooves of the marks line (68) range from 0.1 to 0.5 mm.
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    同族专利:
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    JPWO2011115152A1|2013-07-04|
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    CN102803694A|2012-11-28|
    CN102803694B|2014-12-31|
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    法律状态:
    2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|
    2019-10-29| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|
    2020-12-08| B09A| Decision: intention to grant|
    2021-02-17| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 16/03/2011, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    JP2010-064115|2010-03-19|
    JP2010-064106|2010-03-19|
    JP2010064115|2010-03-19|
    JP2010-064109|2010-03-19|
    JP2010064106|2010-03-19|
    JP2010064109|2010-03-19|
    JP2011-039660|2011-02-25|
    JP2011039660|2011-02-25|
    PCT/JP2011/056164|WO2011115152A1|2010-03-19|2011-03-16|Piston for internal combustion engine|
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