JP4392305B2 - Part fastening driver unit - Google Patents

Description

  The present invention relates to a component fastening driver unit that fastens a component such as a screw to a workpiece.

  Conventionally, in order to fasten a screw to a work, the screw fastening device indicated by patent documents 1 is used. This screw tightening device connects a motor drive shaft and an output shaft rotatably provided on a coaxial line of the drive shaft with a coil spring, and detects rotation of both the drive shaft and the output shaft. Each encoder is provided, and a driver bit that rotates integrally with the output shaft is connected. When a screw is tightened on a workpiece using this screw tightening device, a screwdriver bit is engaged with a screw head, and this is rotated by driving a motor to impart rotation to the screw. At this time, as the screw is tightened, a corresponding tightening torque acts on the driver bit, and this becomes a rotational load of the driver bit, and the coil spring is twisted. As a result, there is a difference between the rotation angle of the driver bit detected by the two encoders and the rotation angle of the motor drive shaft, so that the tightening torque can be determined from this rotation angle difference.

Japanese Patent Laid-Open No. 2003-166887

  In the above conventional screw tightening device, the tightening torque accuracy greatly depends on the characteristics of the coil spring and the friction between the rotating parts such as the output shaft and the surroundings. For example, when the coil spring undergoes aging (sagging), the torque transmission performance and the like change, whereby the tightening torque determined from the rotation angle difference between both encoders and the torque actually transmitted to the screw There is a risk of errors in between. The same applies when the rotational load on the output shaft increases due to seizure due to deterioration of the bearing. In addition, the coil spring may even break when the distortion in the torsional direction due to aging exceeds a limit. For these reasons, it is indispensable for the efficient operation of the screw tightening device to grasp the distortion of the coil spring and the frictional state of the rotating parts, and to determine the appropriate part replacement time based on that. In the screw tightening device, the state of the coil spring or the like cannot be known, which causes problems such as unstable tightening torque accuracy. Particularly, recently, tightening torque management in a low region corresponding to a small screw such as a very small precision screw has been desired. However, the above-described problem becomes remarkable in such low region tightening torque management.

  The present invention has been created in view of the above problems, and an object of the present invention is to provide a component fastening driver unit that can stably detect torque based on a difference in rotation angle. In order to achieve this object, the present invention provides a component fastening driver unit having a rotation drive means and a drive tool connected to the drive shaft of the rotation drive means via an elastic member, First rotation angle detection means capable of outputting a signal indicating the absolute rotation angle of the drive shaft, second rotation angle detection means capable of outputting a signal indicating the absolute rotation angle of the drive tool, and these first rotation angle detection means And the second rotation angle detection means determine the specific rotation angle difference between the drive shaft and the drive tool from each signal output when the rotation drive means is not driven. Control for confirming whether or not the rotation angle difference obtained from the signals respectively output from the first rotation angle detection means and the second rotation angle detection means is lower than the use area when the driving tool is rotated by driving. Characterized in that it comprises a knit. Preferably, the first and second rotation angle detecting means are both resolvers, and the elastic member is a torsion coil spring. Moreover, it is preferable that the said control unit is a thing which confirms a natural rotation angle difference for every fastening operation of components.

  The component fastening driver unit of the present invention confirms whether or not the inherent rotational angle difference between the drive shaft of the rotational drive means and the drive tool is in a region lower than the region of the rotational angle actually used for detecting the tightening torque. To do. Therefore, it is possible to grasp the distortion due to aging of the elastic member between the drive shaft of the rotary drive means and the drive tool, the frictional state of the rotating parts, etc., and appropriately inspect and repair / replace the parts based on the results. be able to. Therefore, there is an advantage that torque detection based on the rotation angle difference can always be performed accurately and stably. Against the backdrop of these effects, this component fastening driver unit adopts a resolver with high resolution as the first and second rotation angle detection means, and selects a torsion coil spring having a characteristic of being twisted in a low torque region as an elastic member. This makes it possible to always detect the tightening torque in the low region accurately and stably. As a result, there are advantages such as facilitating torque management fastening of a micro screw of M2 or less, which has been extremely difficult in the past.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a component fastening driver unit, which includes a tool unit 2 and a control unit 3 that controls the tool unit 2.

  The tool unit 2 includes an AC servomotor 20 (hereinafter simply referred to as a motor 20) as an example of a rotation driving unit. The motor 20 is assembled with a resolver 21 which is an example of first rotation angle detection means. One end of a torsion coil spring 22 (hereinafter referred to as a coil spring 22), which is an example of an elastic member, is connected to the drive shaft 20a of the motor 20, and the other end of the coil spring 22 is connected to the transmission shaft 23. Has been. The transmission shaft 23 is rotatably supported by a bearing, and the transmission shaft 23 is connected to a resolver 24 which is an example of a second rotation angle detection unit. Further, a drive tool 25 having a tip shape that can be engaged with the cross-shaped drive hole of the screw is connected to the resolver 24 so as to rotate integrally with the transmission shaft 23. As described above, the drive shaft 20a or the drive tool 25 of the motor 20 rotates integrally. When a rotational load torque acts on the drive tool 25, the coil spring 22 is twisted accordingly, and the drive shaft 20a A rotational angle difference from the drive tool 25 is generated. The coil spring 22 is supported so as to be movable in the axial direction with respect to the drive shaft 20 a and the transmission shaft 23, thereby allowing expansion and contraction accompanying torsion of the coil spring 22.

  The resolvers 21 and 24 have the same structure and have a known structure. The resolver 24 having a cross section shown in the drawing will be described as an example. The resolver 24 is configured by a rotor 24b having a rotary transformer portion rotatably disposed in a stator 24a having an excitation coil and a position detection coil. When an excitation voltage is applied from the excitation coil to the rotary transformer, an output voltage having a voltage waveform having a phase corresponding to the rotation phase of the rotor 24b is output to the position detection coil. From the phase difference between the excitation voltage and the output voltage, the absolute rotation angle of the rotor 24b rotating with respect to the fixedly arranged stator 24a can be known. A drive shaft 20a is integrally connected to the rotor (not shown) of the resolver 21, and a transmission shaft 23 and a drive tool 25 are integrally connected to the rotor 24b of the resolver 24, respectively. Therefore, the resolver 21 outputs an output voltage indicating the absolute rotation angle of the drive shaft 20a, and the resolver 24 outputs an output voltage indicating the absolute rotation angle of the drive tool 25.

  The control unit 3 applies excitation voltages to the control unit 30, a motor drive unit 31 that drives and controls the motor 20 in response to a command from the control unit 30, and resolvers 21 and 24, and outputs the respective outputs. Various data such as a tightening torque and a target tightening torque according to the difference in the rotation angle determined by the resolver driving units 32 and 33 that calculate the rotation angle from the voltage, and the resolver driving units 32 and 33, and driving of the tool unit 2 A storage unit 34 that stores various programs and parameters necessary for control, an operation unit 35 that inputs various types of information and signals, a display unit 36 that displays various types of information, a robot in which the driver unit 1 is mounted ( And an input / output unit 37 for controlling signal transmission / reception to / from (not shown).

When the power is turned on, the control unit 30 is as shown in FIG.
S01: An excitation command signal is given to the resolver drive units 32 and 33.
S02: The rotation angle is read from the resolver drive units 32 and 33.
S03: A rotation angle difference (hereinafter referred to as a specific rotation angle difference) is calculated.
S04: Check whether the inherent rotation angle difference exceeds the threshold value. If the threshold is not exceeded, jump to S06.
S05: A component replacement display command signal is given to the display unit 36.
S06: An excitation stop command signal is given to the resolver drive units 32 and 33.
S07: End.
Perform the startup check process.

In addition, as shown in FIG.
S11: Waiting for input of a start command signal.
S12: A drive command signal is given to the motor drive unit 31.
S13: An excitation command signal is given to the resolver drive units 32 and 33.
S14: The rotation angle is read from the resolver drive units 32 and 33.
S15: The rotation angle difference is calculated.
S16: The tightening torque corresponding to the rotation angle difference is read from the storage unit 34.
S17: The tightening torque is compared with the target tightening torque. If the target tightening torque is not reached, the process jumps to S14.
S18: A stop command signal is given to the motor drive unit 31.
S19: A completion display command signal is given to the display unit 36.
S20: Wait for the robot standby position return signal.
S21: The rotation angle is read from the resolver drive units 32 and 33.
S22: The intrinsic rotation angle difference is calculated.
S23: Check whether the inherent rotation angle difference exceeds the threshold value. If the threshold is not exceeded, jump to S25.
S24: A component replacement display command signal is given to the display unit 36.
S25: An excitation stop command signal is transmitted to the resolver drive units 32 and 33.
S26: An end screw tightening process is executed.

  Next, the operation of the component fastening driver unit 1 according to the present invention will be described. Here, the driver unit 1 is mounted on a robot (not shown), and a chuck unit (not shown) for holding a screw is provided in front of the moving path of the driving tool 25. The operation of is described.

  First, when the power is turned on, the activation check process is performed in the driver unit 1. In this process, an excitation voltage is applied to the resolvers 21 and 24, a rotation angle is obtained from each output voltage, and a rotation angle difference (specific rotation angle difference) is obtained. In the manufacturing process of the driver unit 1, the resolvers 21 and 24 are adjusted and assembled to the tool unit 2 so that their absolute origins coincide. However, when the secular change (sagging) of the coil spring, the wear of the bearing, or the like occurs, the absolute origin shifts. For example, in the case of the coil spring 22, the width at which the original shape cannot be restored due to secular change gradually increases, and when the bearing is consumed, the frictional resistance of the transmission shaft and the output shaft increases, and the rotation returns to the original position. I can't do that. In this way, an inherent rotation angle difference is generated between the drive shaft 20a and the drive tool 25, and the magnitude thereof is grasped by the start check process when the power is turned on.

  Normally, after the coil spring 22 is twisted, it cannot be considered that it completely returns to its original shape. Further, some frictional resistance acts on the rotating parts such as the output shaft even if the bearing is not consumed. Therefore, the natural rotation angle difference occurs even when each component of the tool unit 2 is in a normal state. As shown in FIG. 4, the region where the normal rotation angle difference in the normal state appears is an insensitive region where the relationship between the tightening torque and the rotation angle difference is not constant every time. It is not used for attached torque control. Therefore, there is no problem even if a natural rotation angle difference occurs in a normal state. Normally, it is assumed that the relationship between the rotation angle difference and the tightening torque is stable in the use region (see FIG. 4). Therefore, the rotation angle difference in the region lower than the lower limit value is determined as the intrinsic rotation angle difference. The activation check process is performed with the threshold value set as the threshold. Thereby, when the detected natural rotation angle difference exceeds the threshold value, LED lighting for notifying parts replacement on the display unit 36 or display by a digital display is performed.

  When the start check process is completed and then a start switch (not shown) of the operation unit 35 is pressed, a screw is supplied to the chuck unit, and the driver unit 1 is moved immediately above the female screw of the workpiece by the operation of the robot. . At the same time, the motor 20 of the driver unit 1 is driven by the control unit 3, and the driving tool 25 starts to rotate. Further, excitation voltages are applied to the resolvers 21 and 24, and detection of the rotation angle is started from the respective output voltages. Subsequently, when the tool unit 2 moves to the workpiece side by the operation of the robot, the driving tool 25 engages with a screw driving hole held by the chuck unit, and this screw is pushed out of the chuck unit to be a female screw of the workpiece. Tighten to. At this time, since the tightening torque (rotational load torque) when the screw is tightened acts on the drive tool 25, the coil spring 23 is twisted in the winding direction accordingly, and is obtained from the output voltages of the resolvers 21 and 24. A difference occurs in the rotation angle. In the control unit 3, a tightening torque corresponding to the rotation angle difference is determined, and it is determined whether or not the tightening torque has reached the target tightening torque. If not, the comparison between the tightening torque corresponding to the new rotation angle difference and the target tightening torque is repeated. When the tightening torque reaches the target tightening torque, the driving of the motor 20 is stopped, and then the driver unit 1 is returned to a predetermined standby position by the operation of the robot. At this time, the natural rotation angle difference is obtained from the output voltages of the resolvers 21 and 24 in the same manner as the start check process, and it is confirmed whether or not this exceeds the threshold value. When the threshold value is exceeded, LED lighting for notifying parts replacement on the display unit or display by a digital display is performed. After the confirmation process of the natural rotation angle difference is completed, the application of the excitation voltage to the resolvers 21 and 24 is stopped, and the screw tightening process is completed. In addition, although it is a timing which calculates | requires a natural rotation angle difference after completion | finish of the above-mentioned screw fastening operation | work, this is after the drive tool 25 leaves | separates from a screw by the action | operation of a robot, and the reaction accompanying the original shape return of the coil spring 23 is settled, ie Is effective after the load around the axis of the drive tool 25 is released.

  As described above, by obtaining and checking the specific rotation angle difference at power-on and every time work is completed, the state of the coil spring and rotating parts is always grasped, and when an abnormality occurs in these, repair and replacement are performed immediately. can do. Therefore, for example, it is possible to prevent erroneous tightening torque detection due to problems such as changes in rotation transmission performance due to aging of coil springs, seizure due to bearing deterioration and wear, etc., and accurate tightening torque detection is always possible. It becomes possible to maintain the screw tightening accuracy with high accuracy.

  In the above description, the control example in which the tightening torque is determined from the true rotation angle difference and compared with the target tightening torque has been introduced. However, the rotation angle difference may be directly compared. Further, although the specific rotation angle difference is obtained and confirmed every time the screw tightening operation is completed, the natural rotation angle difference may be obtained and confirmed before the robot operates before starting the screw tightening operation.

Block explanatory drawing of the component fastening driver unit which concerns on this invention. The flowchart of the starting check process of the component fastening driver unit which concerns on this invention. The flowchart of the screw fastening process of the component fastening driver unit which concerns on this invention. The graph which shows the characteristic of the resolver which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Component fastening driver unit 2 Tool unit 3 Control unit 20 AC servomotor 20a Drive shaft 21 Resolver 22 Torsion coil spring 24 Resolver 25 Drive tool

Claims (3)

A component fastening driver unit having a rotation drive means, and a drive tool connected to the drive shaft of the rotation drive means via an elastic member,
First rotation angle detection means capable of outputting a signal indicating the absolute rotation angle of the drive shaft of the rotation drive means, second rotation angle detection means capable of outputting a signal indicating the absolute rotation angle of the drive tool, and The natural rotation angle difference between the drive shaft and the drive tool is calculated from each signal output when the rotation drive means is not driven from the one rotation angle detection means and the second rotation angle detection means. It is determined whether or not the rotation tool is in a lower area than the use area of the rotation angle difference obtained from the signals respectively generated from the first rotation angle detection means and the second rotation angle detection means when the driving tool is rotated by the rotation drive means. A component fastening driver unit comprising a control unit for checking.   2. The component fastening driver unit according to claim 1, wherein the first and second rotation angle detecting means are both resolvers, and the elastic member is a torsion coil spring.   The component fastening driver unit according to claim 1, wherein the control unit is configured to confirm a difference in natural rotation angle for each fastening operation of the component.

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