• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    11 Abstract An electric pulse tool (lO) for performing tightening operations wheretorque is delivered in pulses to tighten screw joints, (ll), the pulse toolcomprising a bidirectional electric motor (12), (l4,l5,25) an output shafta sensor for monitoring a parameter reflecting a delivered(16) (l4,l5,25) is torque pulse, and a control unit (ll), for controlling the electric motor wherein the sensor arranged to provide information to the control unit (l6). The regarding the monitored parameter control unit (16) is arranged to, during a tightening operation performed by the electric pulse tool (10) in a first direction, control the motor to provide at least one torque pulse in a second direction that is opposite to the first direction. (Elected for publication: Fig. l)
    公开号:SE1551333A1
    申请号:SE1551333
    申请日:2015-10-15
    公开日:2017-04-16
    发明作者:Per Erik Asplund Daniel
    申请人:Atlas Copco Ind Technique Ab；
    IPC主号:
    专利说明:

    Pulse tool The invention relates to an electric pulse tool for performingtightening operations where torque is delivered in pulses to tightenand/or loosen screw joints. Specifically, the invention relates to anelectric pulse tool including a sensor for monitoring a parameterreflecting a delivered torque pulse and a control unit for controllingthe electric motor during the tightening operation based on said monitored parameter.Background During a tightening operation, in which a pulse tool is used for tightening a joint, torque is applied to the joint in pulses by amotor housed inside the pulse tool. Often it is desired to control thetightening such that a specific torque or clamp force is installedinto the joint. The applied torque may be monitored by a torquesensor, but it may also be monitored by an angle meter, anaccelerometer or a gyro that monitors the retardation of the output shaft so as to indirectly monitor the applied torque.
    In a normal tightening operation only a part of the applied torquecontributes to the torque or clamp force that is actually installedinto the joint. The major part of the applied torque is lost in friction. The friction depends on temperature, humidity and type and condition of the thread. It is difficult, if not impossible, to foresee the friction with certitude in any given tightening operation.
    Hence, there is always an uncertainty in how much of the appliedtorque that is installed into the joint and how much that is lost infriction. Under certain conditions the installed torque may be as lowas l0 per cent of the applied torque. The uncertainty with respect tothe installed torque may lead to that for a tightening operation where the dynamically measured torque is within a predetermined interval that is considered as valid the clamp force or the statically installed torque may be too low or too high.
    In the prior art there exists methods of monitoring the clamp forceinstead of the dynamical torque. Such methods are however cumbersomeand time consuming as they involve the use of ultra sound sensors orthe like, which are arranged to monitor the elongation of the screw or bolt in order to evaluate the clamp force.
    Other methods exist for deducing the clamp force indirectly from thetorque measured in opposite directions. From US 5 l05 5l9 it is knownto, during a tightening operation of an otherwise continuoustightening operation, stopping and reversing the rotation of the motorso as to monitor the torque both in tightening and loosening of ajoint. By comparing the torque to angle dependency during bothtightening and loosening it is possible to determine the friction inthe joint and to proceed the tightening towards a target value thatcorresponds to a torque installed in the joint rather than an appliedtorque. The method disclosed in US 5 l05 5l9 is however adapted to afixed tool where there is no limitation in how much reaction torquethe structure may withstand and where the time of concluding a specific tightening operation is not of uttermost importance.
    For hand held power tools it is however important both that thereaction force that is subjected to the operator is as low as possibleand that the time of concluding a specific tightening operation is aslow as possible. An operator may conduct many hundreds of tighteningoperations during a working cycle and it is therefore important thatthey are both ergonomic for the well-being of the operator and rapidfor the productivity at the work station. An ergonomic tighteningoperation typically implies that the reaction torque is as low as possible.
    Hence, there is a need for a pulse tool that is adapted to deliver atorque in which the installed torque may be controlled and in which a tightening operation may be performed rapidly with a high reliability.
    Summary of the invention An object of the invention is to provide a torque delivering pulsetool with which the installed torque may be controlled and by means ofwhich a tightening operation may be performed rapidly with a highreliability.
    This object is achieved in accordance with a first aspect of theinvention by an electric pulse tool for performing tightening operations where torque is delivered in pulses to tighten screwjoints, the pulse tool comprising a bidirectional electric motor, anoutput shaft, a sensor for monitoring a parameter reflecting adelivered torque pulse, and a control unit for controlling theelectric motor, wherein the sensor is arranged to provide informationregarding the monitored parameter to the control unit. The controlunit is arranged to, during a tightening operation performed by theelectric pulse tool in a first direction, control the motor to provideat least one torque pulse in a second direction that is opposite to the first direction.
    In accordance with a second aspect the invention relates to a methodof tightening a screw joint with an electric pulse tool, the methodcomprising: - pulsing an output shaft of the pulse tool in a first direction soas to tighten a joint, - monitoring a parameter reflecting a delivered torque pulse in thefirst direction. The method further comprises pulsing the output shaftin a second direction that is opposite to the first direction, andmonitoring a parameter reflecting a delivered torque pulse in said second direction.
    With the invention according to the first and the second aspect anincreased reliability may be achieved by an operation step that iseasy to implement and that does not slow down the tightening operation.
    In fact, the tightening operation will be more rapid compared to a common pulse method in which the torque increments are often decreased as the torque approaches the target torque. The torquepulse or pulses that in accordance with the invention is/are providedin the second direction provides information regarding the torque thatis actually installed into the joint and thereby the torque incrementsmay be adjusted so as to bring the torque as close as possible to a target torque, without the need of decreasing the torque increment.Also, the clamp force may be estimated such that the torque incrementsmay be adapted to a specific target clamp force, instead of a target torque.
    Other features and advantages of the invention will be apparent fromthe dependent claims, the drawings and from the detailed description of the shown embodiment.
    Short description of the drawings In the following detailed description reference is made to the accompanying drawings, of which: Fig. 1 is a schematic representation of a pulse tool according toa specific embodiment of the invention; Fig. 2 is a schematic representation of the delivered torque as afunction of operation time; and Fig. 3 is a schematic representation of the clamp force installed in a joint as a function of operation time.
    Detailed description of the shown embodiment of the invention In fig. l an electric pulse tool l0 in accordance with a specific embodiment of the invention is schematically shown. The pulse tool l0is configured to perform tightening operations where torque isdelivered in pulses to tighten screw joints. For this purpose thepulse tool comprises a bidirectional electric motor ll which isarranged to deliver torque in two opposite rotational directions, i.e. clockwise and counter clockwise.
    The electric pulse tool l0 further comprises a handle 22, which is of a pistol type in the shown embodiment. The invention is howeverintended to cover any type of handheld pulse tools. A power supply 24,such as a battery, is arranged in the lower part of the handle and a trigger 23 is arranged for manipulation of the operator so as to powerthe electric motor ll. The power supply may also be a connection to an electric cable.
    Further, the pulse tool comprises an output shaft l2 and a sensorl4,l5,25 for monitoring a parameter reflecting a delivered torquepulse.
    The sensor may be a torque sensor, an angle sensor, an accelerometer, a gyro, or the like. In the shown embodiment there is afirst sensor l4,l5 that consists of an angle sensor that monitors therotation of an input shaft l7 by means of a rotational sensor part l4and a static sensor part l5. A second sensor 25 in the form of atorque sensor is arranged on the output shaft l2. For the inventioneither an angle sensor or a torque sensor is needed, not both.However, both sensors may be provided to offer increased accuracy or redundancy.
    The shown embodiment further comprises a pulse unit l3 comprising an inertia body l8 that houses a piston activated rotator l9. The inertiabody l8 is rigidly connected to the input shaft l7 and driven by arotor 20 of the motor ll. The rotor 20 is in the shown embodimentarranged coaxially inside a stator 2l of the motor ll. A pulse is generated as cam surfaces (not shown) on the inside of the inertiabody l8 interacts with the pistons so as to force the rotator l9 to rotate in a conventional manner well known in the art.
    The invention is however not limited to pulse tools with a pulse unit.Pulses may also be produced in pulse tools with a direct connectionbetween the motor and the output shaft by pulsing the output of themotor of the pulse tool. The invention also covers such pulse tools and striking pulse tools often known as impact wrenches.
    For a pulse tool including a pulse unit the angle sensor l4,l5 may bearranged to monitor both the rotation of the inertia body l9 and theretardation of the same. The retardation may be used to calculate thetorque that is installed into the joint. The torque sensor 25 isarranged to measure the torque directly. The torque meter is arrangedon the output shaft l2 as close as possible to the joint in order to monitor the delivered torque.
    A control unit l6 is arranged to control the electric motor ll. Thesensor l4,l5,25 is arranged to provide information regarding the monitored parameter to the control unit l6. This is conventional incontrolled tightening operations where the tightening is governedtowards a specific target value, such as target torque, angle or clamp force.
    In the inventive pulse tool l0 the control unit l6 is arranged to,during a tightening operation performed by the electric pulse tool l0in a first direction, control the motor ll to provide at least onetorque pulse in a second direction that is opposite to the firstdirection. This is illustrated in figures 2 and 3. In figure 2 thedelivered torque T is illustrated as a function of time t during atightening operation and in figure 3 the installed clamp force F isillustrated as a function of time t during the same tightening operation.
    The tightening operation is illustrated as comprising 4 phases A-D.Typically, the illustrated tightening operation is a tightening of afastener such as a screw into a joint. In the first phase A torquepulses of a constant torque are delivered so as to screw the fastenerinto a thread without imparting any clamp force into the joint. Atthis point the torque is only needed to overcome the friction in thethreads. Torque that is delivered in addition to the torque needed to overcome the friction will accelerate the fastener.
    In phase B the head of the screw has reached the joint and for every delivered torque pulse additional clamp force is stepwise installed into the joint as the strain in the fastener is increased. During thisphase the torque increases substantially linearly with the anglerotation of the fastener and, since the torque is delivered in pulses,in steps with respect to the time t. For each pulse during phase B,which lasts for a very short period of time, i.e couple ofmilliseconds, a substantially constant clamp force increase is achieved.
    In phase C one or more torque pulses are provided in a directionopposite to the rotational direction of the pulses in phase B. As isknown in the prior art a loosening torque over specific angularinterval may be utilised to determine the friction in the joint and todeduce the torque that has been installed into the joint. Thisinformation may be instantly processed by the control unit l6 so as toincrease the accuracy of the tightening. As an example it will bepossible to deduce the clamp force that has been installed into thejoint. As is visible in the respective diagrams of figures 2 and 3,the delivered torque T in phase C is negative, and hence, the clamp force F installed in the joint decreases in phase C.
    In phase D the tightening operation is concluded towards a specific target value, such as a target torque, target angle or target clamp force. A target may be either higher or lower than the torqueaccomplished during phases A-C, but under most circumstances thetarget will be higher such that the joint will need to be tightenedfurther. The difference with respect to a normal tightening operationis that the control unit has more information about nature and stateof the joint at this point, as a consequence of the pulse in theopposite direction during phase C. This additional information may be concluded from one single pulse in the opposite direction.
    Preferably, the sensor l4,l5 that is arranged to monitor a parameterthat reflects a delivered torque pulse in the first direction may alsomonitor a parameter that reflects a delivered torque pulse in the second direction. This is readily achievable with an angle meter as illustrated in figure 1. Such an angle meter 14,15 may be configuredto monitor the rotation in both directions and to deduce theretardation of the pulse unit 13 or of the output shaft 12 in both directions.
    Of course, in the embodiment where the sensor is a torque meter, thetorque meter may also be configured to monitor the torque in bothdirections. A torque is typically arranged to monitor the absolutetorque, i.e. without information in which direction the torque acts.The control unit 16 will however register the torque as negative orpositive as a function of in which direction it has controlled the motor 11 to rotate.
    Above, the invention has been described with reference to a specific embodiment. The invention is however not limited to this embodiment.It is obvious to a person skilled in the art that the inventioncomprises further embodiments within its scope of protection, which is defined by the following claims.
    权利要求:
    Claims (6)
    [1] 1. l. An electric pulse tool (l0) for performing tightening operations where torque is delivered in pulses to tighten screw joints, the pulsetool comprising: - a bidirectional electric motor (ll),- an output shaft (l2),(l4,l5,25) - a sensor for monitoring a parameter reflecting a delivered torque pulse, and(16) (l4,l5,25) - a control unit for controlling the electric motor (ll), wherein the sensor is arranged to provide information regarding the monitored parameter to the control unit (l6), characterised in that the control unit (l6) is arranged to, (10) during atightening operation performed by the electric pulse tool in afirst direction, control the motor to provide at least one torque pulse in a second direction that is opposite to the first direction.
    [2] 2. The electric pulse tool (l0) wherein the (l4,l5,25) according to claim l,sensor is arranged to also monitor a parameter reflecting a delivered torque pulse in the second direction.
    [3] 3. The electric pulse tool (l0) wherein (25) according to claim l or 2, the sensor is a torque sensor.
    [4] 4. The electric pulse tool (l0) wherein (10) according to claim l or 2,(13)(12). the pulse tool includes a pulse unit (ll) that intermittently connects the motor to the output shaft
    [5] 5. The electric pulse tool (l0) wherein the (l4,l5) according to claim 4,sensor is an angle meter monitoring the rotation and retardation of an inertia body (l8) of the pulse unit (l3).
    [6] 6. A method of tightening a screw joint with an electric pulse tool,the method comprising: - pulsing an output shaft of the pulse tool in a first direction soas to tighten a joint, - monitoring a parameter reflecting a delivered torque pulse in the first direction, characterised by pulsing the output shaft in a second direction that is opposite to the first direction, and monitoring a parameter reflecting a delivered torque pulse in said second direction.
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    法律状态:
    优先权:
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    JP2018518953A| JP6837061B2|2015-10-15|2016-09-23|Pulse tool|
    US15/766,260| US10882166B2|2015-10-15|2016-09-23|Pulse tool|
    PCT/EP2016/072712| WO2017063851A1|2015-10-15|2016-09-23|Pulse tool|
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    KR1020187013070A| KR20180069840A|2015-10-15|2016-09-23|Pulse tool|
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