JP5857948B2 - Nut runner - Google Patents

Description

  The present invention relates to a nut runner that tightens screw members such as bolts and nuts.

  Conventionally, as this type of nut runner, after the screw member is rotated forward from the snag torque to a predetermined torque (Mmax) for completion of tightening to complete the tightening, the screw member is rotated backward to reach the snag torque again. Then, by subtracting the rotation angle W1 when the normal rotation is reached and the snag torque is reached from the rotation angle W3 when the rotation is reversed and the snag torque is reached again, the twist angle of the output shaft of the nut runner is obtained. A technique is known in which the actual tightening angle of the screw member from which the above error has been removed is measured (see, for example, Patent Document 1).

JP 09-021712 A

  However, in the technique described in Patent Document 1, since the screw member is reversely rotated when obtaining the rotation angle W3 when the snag torque is reached again, a gap (play) between the head of the screw member and the socket is obtained. Therefore, there is a problem in that the actual tightening angle of the screw member (hereinafter referred to as the actual tightening angle) cannot be measured with high accuracy.

  On the other hand, the rotational position of the head of the screw member when the snag torque is reached and the rotational position of the head of the screw member when tightening is completed are measured from an image taken using an image sensor, and these rotational positions are measured. It is also conceivable to obtain the actual tightening angle of the screw member by calculating the difference between the two.

  In this case, there is a problem that not only the cost of the image sensor is generated, but also that the tightening is interrupted when the snag torque is reached and shooting is performed, so that it takes time to measure the actual tightening angle. It was.

  The present invention has been made in view of the above-described problems of the prior art, and is capable of measuring an accurate actual tightening angle in a short time from which a shift of the tightening angle due to bending of a screw member or an internal mechanism is separated. A nut runner that can be used.

  In order to solve the above problems, the nut runner according to the present invention has (1) a rotational drive means for rotating the drive shaft, and a socket connected to the drive shaft at one end and engageable with a screw member at the other end. The mounted output shaft, a torque sensor for detecting the rotational torque of the output shaft, an encoder for detecting the rotational angle of the rotational drive means, the rotational torque detected by the torque sensor and the rotational angle detected by the encoder Based on the rotation angle when the rotational torque reaches the snag torque, the rotation means being a base point angle. After rotating the rotation driving means in the tightening direction until the angle reaches a predetermined tightening completion angle, the rotation driving means is brought into a freely rotatable state. The rotational driving means is rotated in the tightening direction until the rotational torque reaches the snag torque again, and the rotational angle when the rotational torque reaches the snag torque again is measured as the actual tightening angle of the screw member. It consists of what to do.

  With this configuration, after the control means completes the angle tightening at the tightening completion angle, the rotation driving means is brought into a freely rotatable state, and when the rotation driving means is rotated forward again to reach the snag torque, the rotation angle is actually tightened. Since this is measured as an angle, this actual tightening angle is the rotational angle in the state where the snag torque has been reached again, so that the deflection generated in the screw member and internal mechanism when the angle tightening is completed is separated from the angle Become.

  In addition, the actual tightening angle is a rotation angle measured in a state in which the snag torque is reached again by the forward rotation of the screw member and the gap between the socket and the screw member is filled. The error due to the gap between them is the separated angle.

  Also, in order to measure the actual tightening angle, after the angle tightening is completed, the rotational driving means can be freely rotated and then the rotational driving means only needs to be rotated forward again. Can be measured.

  Furthermore, since the actual tightening angle can be measured without adding or changing components, it is possible to prevent an increase in cost.

  Therefore, it is possible to measure in a short time an accurate actual tightening angle from which the displacement of the tightening angle due to the bending of the screw member or the internal mechanism is separated.

  In the nut runner described in the above (1), (2) the rotation driving means is connected to a motor as a driving source having a rotating shaft and the rotation shaft connected to one end side of the rotating shaft and inputted from the rotating shaft. And a speed reducer to which the output shaft is connected, and the encoder is preferably provided on the other end side of the rotary shaft.

  With this configuration, in the nut runner having the configuration in which the motor and the speed reducer that decelerates the rotation input from one end side of the rotating shaft of the drive motor are provided, and the encoder is provided on the other end side of the rotating shaft of the motor. Since the tightening angle can be measured, the actual tightening angle can be measured without reducing the convenience or cost increase of the nut runner due to the configuration change or arrangement change of the motor, the speed reducer, and the encoder.

  In the nut runner described in the above (1) or (2), (3) the control means makes the rotation drive means in a freely rotatable state by setting the drive voltage of the rotation drive means to 0. Is preferred.

  With this configuration, in order to make the rotation drive means freely rotatable, it is only necessary to set the drive voltage of the rotation drive means to 0. Can be measured.

  ADVANTAGE OF THE INVENTION According to this invention, the nut runner which can measure the exact actual fastening angle from which the shift | offset | difference of the fastening angle by the bending etc. of a screw member or an internal mechanism was isolate | separated can be provided in a short time.

It is a block diagram which shows the structure of the nut runner which concerns on one embodiment of this invention. It is a figure which shows the relationship between the rotational torque at the time of measuring the bolt fastening and the actual fastening angle in the nut runner which concerns on one embodiment of this invention, and a rotational angle. (A), (b) is a figure which shows the positional relationship of the socket and bolt of a nut runner which concerns on one embodiment of this invention. It is a flowchart which shows operation | movement of the nut runner which concerns on one embodiment of this invention. It is a figure which shows the measurement precision of the nut runner which concerns on one embodiment of this invention.

  Hereinafter, embodiments of a nut runner according to the present invention will be described with reference to the drawings.

  1 to 5 are views showing an embodiment of a nut runner according to the present invention. FIG. 1 is a block diagram showing a configuration of a nut runner according to an embodiment of the present invention.

  First, the configuration will be described.

  In FIG. 1, a nut runner 10 is for rotating a bolt 21 as a screw member to be fastened to a non-fastened object 23, and includes a motor 11, a speed reducer 12, a torque sensor 13, a socket 14, an output shaft 18, An encoder 15 and a controller 16 are provided.

  In this embodiment, the nut runner 10 is attached to an assembly facility 30 such as an industrial robot or an air cylinder, and the bolt 21 is tightened in an automobile assembly process. Specifically, the nut runner 10 is used in an assembly process that requires high accuracy, such as valve fastening of a high-pressure fuel pump of an automobile.

  The motor 11 is a torque generation source for rotating the bolt 21 and is composed of a servo motor capable of phase control. The motor 11 has a rotating shaft 11a, and is configured to be able to rotate in the forward rotation direction (also referred to as a tightening direction) and the reverse rotation direction (also referred to as a slack direction).

  The speed reducer 12 is connected to one end side of the rotating shaft 11a of the motor 11, and decelerates the rotation input from the rotating shaft 11a and outputs it from the drive shaft 12a. The drive shaft 12 a of the speed reducer 12 is connected to the output shaft 18. The motor 11 and the speed reducer 12 constitute a rotational drive means 17 for driving the drive shaft 12a.

  A socket 14 that engages with the head 22 of the bolt 21 is detachably fixed to the output shaft 18. The socket 14 can be changed to a size corresponding to the two-surface width of the head 22 of the bolt 21 to be fastened.

  A bracket 19 for mounting the nut runner 10 to the assembly facility 30 is provided between the output shaft 18 and the socket 14, and the bracket 19 is fixed to a housing (not shown) of the nut runner 10.

  The torque sensor 13 is provided on the output shaft 18, detects the rotational torque (tightening torque) of the output shaft 18, and transmits a detected rotational torque detection signal (hereinafter simply referred to as rotational torque) to the controller 16. It is like that.

  The encoder 15 is attached to the end of the motor 11 at the other end of the nut runner 10, detects the rotation angle of the rotation shaft 11a of the motor 11, and detects the detected rotation angle detection signal (hereinafter simply referred to as rotation angle). The data is transmitted to the controller 16. The encoder 15 detects the rotation speed in addition to the rotation angle of the motor 11.

  Although it is possible to omit the speed reducer 12, configure the speed reducer 12 integrally in the motor 11, or change the installation position of the encoder 15, as described above, the nut runner 10 includes a motor 11 and a speed reducer 12 that decelerates rotation input from one end side of the rotating shaft 11a of the motor 11, and an encoder 15 is provided on the other end side of the rotating shaft 11a of the motor 11. By doing so, there is no inconvenience in mounting the nut runner 10 to the assembly facility 30 and tightening the bolt 21 by the nut runner 10.

  The controller 16 is electrically connected to the motor 11, the torque sensor 13, and the encoder 15, and receives the torque detected by the torque sensor 13 and the rotation angle detected by the encoder 15, and based on these torque and rotation angle. Thus, the drive of the motor 11 is controlled.

  The controller 16 includes a ROM (Random Access Memory), a RAM (Read Only Memory), and a CPU (Central Processing Unit) (not shown). Is used as a work area for calculation.

  Moreover, in this Embodiment, although the controller 16 is demonstrated as a component which comprises the nut runner 10, you may comprise so that the controller 16 may be provided in the assembly equipment 30 side.

  Here, in general, as a tightening management method for a screw member such as the bolt 21, there is a method called angle tightening (rotation angle method) in addition to torque tightening (also referred to as torque method).

  Angle tightening is a method for managing the rotation angle of a screw member as a substitute for axial force, and can obtain a higher axial force accurately compared to torque tightening for managing the tightening torque of a screw member as a substitute for axial force. This is a possible tightening management method.

  Specifically, when tightening the screw member using angle tightening, the screw member is rotated from the base point to a predetermined tightening angle based on the angle at which the screw member is rotated to reach the snag torque. By doing so, the conclusion is completed.

  Here, the snag torque is a torque that becomes a base point (angle 0) when the screw member is seated and fastening is started.

  This angle tightening is used, for example, for fastening a valve of a high-pressure fuel pump of an automobile. In fastening a valve of a high-pressure fuel pump, it is required to satisfy both a required sealing surface pressure and a reduction in cylinder distortion.

  Therefore, in tightening the screw member for valve fastening, it is necessary to perform high-precision angle tightening so that the angle error with respect to the specified tightening angle is within ± 1 degree. In order to guarantee accuracy, it is necessary to accurately measure the tightening angle (hereinafter referred to as the actual tightening angle).

  Therefore, in the present embodiment, as shown in FIG. 2, the nut runner 10 (specifically, the motor 11) is free (freely rotatable) after completing the angle tightening at the point C as shown in FIG. ) And reversely rotated by free rotation by the amount of bending or the like generated in the bolt 21 and the internal mechanism of the nut runner 10 (point D), and the nut runner 10 was rotated forward again to reach the snag torque again. The rotation angle at time (point F) is measured as the actual tightening angle.

  Specifically, in FIG. 2, the bolt 21 starts to rotate forward at point A, reaches snag torque at point B, and completes the angle tightening at point C. 11) is set free (a state in which free rotation is possible).

  When the nut runner 10 is made free, the bolt 21 and the socket 14, the output shaft 18, the speed reducer 12, the motor 11 and the like which are internal mechanisms of the nut runner 10 are generated by the tightening force generated by the motor 11. The nut runner 10 (specifically, each rotating part such as the socket 14) rotates backward by free rotation and reaches point D by the amount of bending or the like.

  Then, by rotating the nut runner 10 forward again to reach the snag torque again at the F point via the E point, the rotation angle of the nut runner 10 (specifically, the motor 11) at the F point is set. The actual tightening angle is measured.

  Here, at the point C, since the angle tightening is completed and the forward rotation torque is applied to the bolt 21, the clearance (play) between the socket 14 and the bolt 21 (specifically, the head 22). ) Is packed in the forward rotation direction of the socket 14 as shown in FIG.

  In FIGS. 3A and 3B, the clockwise direction is the forward rotation direction, and the counterclockwise direction is the reverse rotation direction.

  Further, at the point D, the clearance between the socket 14 and the bolt 21 (specifically, the head 22) is caused by a tightening reaction force when the nut runner 10 is freed and the bending of each part is eliminated. As shown in FIG. 3B, the socket 14 is packed in the reverse rotation direction.

  Further, at the point E, the nut runner 10 is rotated forward again, so that the gap between the socket 14 and the bolt 21 (specifically, the head 22) becomes a socket as shown in FIG. 14 is packed in the forward rotation direction.

  The bending of the internal mechanism of the nut runner 10 includes torsion of the rotating shaft 11a of the motor 11, backlash of the speed reducer 12 and torsion of the drive shaft 12a, torsion of the output shaft, torsion of the socket 14, and the like.

  In the present embodiment, the controller 16 uses the rotation angle detected by the encoder 15 when the rotation torque detected by the torque sensor 13 has reached the snag torque as a base point angle, and the rotation angle detected by the encoder 15 has completed predetermined tightening. The motor 11 is allowed to freely rotate after the motor 11 is rotated forward until the angle is reached.

  The controller 16 rotates the motor 11 forward until the rotational torque detected by the torque sensor 13 reaches the snag torque again, and the encoder 15 detects when the rotational torque detected by the torque sensor 13 reaches the snag torque again. The measured rotation angle is measured as the actual tightening angle of the bolt 21.

  Moreover, the controller 16 makes the motor 11 free by setting the drive voltage of the motor 11 to zero.

  Next, operation | movement of the nut runner 10 comprised as mentioned above is demonstrated.

  As shown in FIG. 4, when the bolt 21 is tightened, the controller 16 rotates the motor 11 in the forward direction with the bolt 21 engaged with the socket 14. Thereby, a rotational torque and a rotational angle increase from the A point of FIG. 2 (step S11).

  Next, the controller 16 determines whether or not the rotational torque detected by the torque sensor 13 has reached the snag torque (point B in FIG. 2) while continuing the normal rotation of the motor 11 (step S12). Is “NO” (no snag torque reached), the motor 11 continues to rotate forward.

  Next, when the determination in step S12 is “YES” (snag torque reached), the controller 16 sets the base point, that is, the rotation angle detected by the encoder 15 when the snag torque is reached (step 0). S13).

  Next, the controller 16 determines whether or not the angle tightening has been completed, that is, whether or not the rotation angle detected by the encoder 15 has reached a predetermined angle (point C in FIG. 2) based on reaching the snag torque (point B). (Step S14) When this determination is “NO” (angle tightening is not completed), the motor 11 continues to rotate normally.

  Next, when the determination in step S14 is “YES” (angle tightening complete), the controller 16 frees the motor 11 (step S15). As a result, due to the tightening force generated by the motor 11, internal mechanisms such as the socket 14, the output shaft 18, the speed reducer 12, and the motor 11 and the bending generated in the bolt 21 are released. ) To reach point D from point C in FIG.

  Next, the controller 16 rotates the motor 11 forward (step S16), determines whether or not the snag torque has been reached (step S17), and when the determination in step S17 is "NO (snag torque not reached)" Continues normal rotation of the motor 11.

  As the forward rotation continues, the gap between the socket 14 and the head portion 22 of the bolt 21 is closed in the reverse rotation direction of the socket 14 as shown in FIG. As shown in FIG. 2, the socket 14 changes to a state of being packed in the forward rotation direction, and reaches the point E from the point D in FIG.

  Further, as the forward rotation further continues, the rotational torque increases toward the snag torque, and reaches the point F from the point E in FIG.

  Next, when the determination in step S17 is “YES” (snag torque reached), the controller 16 detects the rotation angle detected by the encoder 15 when the base point set in step S13 is 0 degree, and this rotation angle. Is measured as the actual tightening angle (step S18).

  As described above, the controller 16 completes the angle tightening in step S14 by the forward rotation of the motor 11, and then temporarily frees the motor 11 in step S15, and again rotates the motor 11 again to reach the snag torque. The rotation angle detected by 15 is measured as an actual tightening angle in step S18.

  For this reason, since the actual tightening angle measured in step S18 is the rotation angle of the output shaft 18 detected in the state where the snag torque has been reached again, the socket 14 and the output shaft when the angle tightening is completed in step S14. 18, the internal mechanism such as the speed reducer 12 and the motor 11 and the twist generated in the bolt 21 are separated.

  In addition, the actual tightening angle measured in step S18 is detected when the snug torque is reached again by the normal rotation of the bolt 21 and the gap between the socket 14 and the bolt 21 is packed in the positive rotation direction of the socket 14. Since this is the rotation angle of the output shaft 18, the error due to the gap between the socket 14 and the bolt 21 is separated.

  Therefore, as shown in FIG. 5, the actual tightening angle in step S18 is measured with the same high accuracy as in the case of using a method of photographing the head 22 of the bolt 21 with an image sensor and measuring the actual tightening angle. .

  Specifically, in FIG. 5, the actual tightening angle measured by the nut runner 10 of the present embodiment (described as the present invention in FIG. 5) and the actual tightening angle measured by photographing with an image sensor (FIG. 5). In FIG. 5, the difference in angle was 0.1 degrees or less under all tightening conditions (torque in FIG. 5).

  Note that the actual tightening angle measured using the image sensor is the difference between the bolt head measured by the conventional nutrunner when the snag torque is reached and the bolt head angle measured from the image. It is obtained by calculating.

  As described above, in the present embodiment, the controller 16 tightens the rotation drive unit 17 until the rotation angle reaches a predetermined tightening completion angle, with the rotation angle when the rotation torque reaches the snag torque as the base point angle. After rotating in the direction, the rotational driving means 17 is brought into a freely rotatable state, the rotational driving means 17 is rotated in the tightening direction until the rotational torque reaches the snag torque again, and the rotational torque reaches the snag torque again. The rotation angle is measured as the actual tightening angle of the bolt 21.

  With this configuration, after the controller 16 completes the angle tightening at the tightening completion angle, the rotation driving means 17 is brought into a freely rotatable state, and the rotation driving means 17 is rotated forward again to reach the snag torque. Is measured as an actual tightening angle, and this actual tightening angle is a rotation angle in a state where the snag torque has been reached again. Therefore, when the angle tightening was completed, the actual tightening angle occurred in the internal mechanism of the bolt 21 and the nut runner 10 The angle at which the deflection or the like is separated.

  In addition, the actual tightening angle is the rotation angle measured when the snug torque is reached again by the normal rotation of the bolt 21 and the gap between the socket 14 and the bolt 21 is closed. The error due to the gap between 21 is the separated angle.

  Further, in order to measure the actual tightening angle, after the angle tightening is completed, it is only necessary to rotate the rotation driving unit 17 in a freely rotatable state and then rotate the rotation driving unit 17 forward again. It can be measured in a short time.

  Furthermore, since the actual tightening angle can be measured without adding a component member, an increase in cost can be prevented.

  Therefore, it is possible to measure the accurate actual tightening angle in which the displacement of the tightening angle due to the bending of the internal mechanism of the bolt 21 and the nut runner 10 is separated in a short time.

  In the present embodiment, the rotation drive unit 17 is connected to the motor 11 as a drive source having the rotation shaft 11a and one end side of the rotation shaft 11a and decelerates the rotation input from the rotation shaft 11a. The speed reducer 12 is connected to the output shaft 18, and the encoder 15 is provided on the other end side of the rotary shaft 11a.

  With this configuration, the motor 11 and the speed reducer 12 that decelerates the rotation input from one end side of the rotating shaft 11 a of the motor 11 are provided, and the encoder 15 is provided on the other end side of the rotating shaft 11 a of the motor 11. In the nut runner 10, the actual tightening angle can be measured, so that the convenience as a nut runner is not reduced or the cost is increased due to the configuration change or arrangement change of the motor 11, the speed reducer 12, and the encoder 15. The actual tightening angle can be measured.

  Further, in the present embodiment, the controller 16 is configured to make the rotational driving means 17 freely rotatable by setting the driving voltage of the rotational driving means 17 to zero.

  With this configuration, in order to make the rotation drive unit 17 in a freely rotatable state, it is only necessary to set the drive voltage of the rotation drive unit 17 to 0. The tightening angle can be measured.

  As described above, the nut runner according to the present invention has an effect that it is possible to measure an accurate actual tightening angle in which the displacement of the tightening angle due to the bending of the screw member or the internal mechanism is separated in a short time, It is useful as a nut runner for tightening screw members such as bolts and nuts.

  DESCRIPTION OF SYMBOLS 10 ... Nutrunner, 11 ... Motor, 11a ... Rotary shaft, 12 ... Reduction gear, 12a ... Drive shaft, 13 ... Torque sensor, 14 ... Socket, 15 ... Encoder, 16 ... Controller (control means), 17 ... Rotation drive means , 18 ... output shaft, 19 ... bracket, 21 ... bolt (screw member), 22 ... head, 23 ... non-fastened

Claims (3)

Rotational drive means for rotating the drive shaft;
An output shaft having one end connected to the drive shaft and a socket engageable with a screw member attached to the other end;
A torque sensor for detecting rotational torque of the output shaft;
An encoder for detecting a rotation angle of the rotation drive means;
A control unit for driving and controlling the rotation drive unit based on the rotation torque detected by the torque sensor and the rotation angle detected by the encoder,
The control means includes
The rotation drive means is rotated in the tightening direction until the rotation angle reaches a predetermined tightening completion angle with the rotation angle when the rotation torque reaches the snag torque as a base angle, and then the rotation drive means is Make it freely rotatable,
The rotational driving means is rotated in the tightening direction until the rotational torque reaches the snag torque again, and the rotational angle when the rotational torque reaches the snag torque again is measured as the actual tightening angle of the screw member. A nut runner characterized by that. The rotation driving means;
A motor as a drive source having a rotating shaft;
A speed reducer connected to one end of the rotating shaft to decelerate rotation input from the rotating shaft and to which the output shaft is connected;
The nut runner according to claim 1, wherein the encoder is provided on the other end side of the rotating shaft.   3. The nut runner according to claim 1, wherein the control unit sets the rotation driving unit to a freely rotatable state by setting a driving voltage of the rotation driving unit to 0. 4.

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