JP4985595B2 - Bolt tightening device - Google Patents

Description

  The present invention relates to a bolt tightening device that tightens a bolt using a nut runner. More specifically, the present invention relates to a bolt fastening device that can reduce vibration of a nut runner (a robot that supports the nut runner).

  As a device for tightening a bolt, an articulated robot with a nut runner attached to the tip of an arm is known. Here, the nutrunner includes a drive motor and a bit portion provided on the drive shaft. And a bolt is tightened by rotating a drive motor in the state which attached the bolt to the bit part.

  In such a tightening device, the robot to which the nut runner is attached receives a reaction force (tightening reaction force) against the bolt tightening via the nut runner. In order to reduce this tightening reaction force, pulse tightening is performed. Has been implemented. In pulse tightening, the tightening torque is not increased linearly over time as in normal tightening, but is changed in a pulse shape as shown in FIG. (Product of tightening torque) can be reduced.

  However, when the robot moves due to the tightening reaction force, it tries to return to the original position. This is because the robot is controlled to maintain the tightening posture. In the pulse tightening, torque fluctuation occurs in a very short time, so that the reaction force from the nut runner and the origin return force that tries to return to the original position work alternately. As a result, the vibration of the robot was large. When the vibration of the robot is large, the variation in the tightening torque of the tightening device cannot be suppressed within a certain range (decrease in tightening process capability), or the durability of the robot is decreased. Thus, the tightening reaction force from the nutrunner had an adverse effect on the robot.

  For this reason, in order to reduce the vibration of the robot due to the tightening reaction force from the nut runner, mechanical measures are taken in the tightening device. As one of the devices in which such measures are taken, there is a tightening device provided with a support mechanism that supports the nut runner in a displaceable manner. In this tightening device, by supporting the tightening reaction force in the support mechanism, the robot is less affected by the tightening reaction force, and the vibration of the robot is reduced (Patent Document 1).

  As another tightening device, there is one in which a pair of nut runners are attached on both sides of a pivotable joint. In this tightening device, when tightening the bolt, before the final tightening, there is a backlash between the socket and the bolt. Since the bolt tightening portion moves freely in the turning direction, the reaction force is not transmitted to the robot. Furthermore, in this final tightening, a large torque is generated in each nut runner. However, since the bolt tightening portion has a pair of nut runners, the pair of nut runners receives a tightening reaction force and the reaction force is applied to the robot. It is designed not to be transmitted to. In this tightening device, the vibration of the robot is reduced in this way (Patent Document 2).

JP 2003-31555 A JP-A-9-66425

  However, in the above-described tightening apparatus, mechanical measures are taken so that the robot does not receive the tightening reaction force, and therefore, it is necessary to attach new parts such as a support mechanism and a joint portion. Therefore, there is a problem that the apparatus configuration becomes complicated and the cost is increased.

  Therefore, the present invention has been made to solve the above-described problems, and reduces vibration of the robot to which the nut runner is attached when the bolt is tightened by pulse tightening with the nut runner without mechanical measures. It is an object of the present invention to provide a bolt fastening device that can be used.

A bolt tightening device according to the present invention made to solve the above-mentioned problems is a bolt tightening device for tightening a bolt by pulse tightening with a nut runner attached to a robot, a robot controller for controlling the operation of the robot, A nut runner controller for controlling the operation of the nut runner, wherein the nut runner controller transmits bolt tightening control information by the nut runner to the robot controller, and the robot controller is generated at the time of pulse tightening of the bolt. so as to reduce the vibration of the robot, raw form on the basis of a control signal for controlling the operation of the robot to the tightening control information, and sends the control signal to the robot, said control signal, The robot is returned to its original position against the bolting reaction force. Is a signal for returning the robot by a correction return displacement amount smaller than the return displacement amount for causing the correction return displacement amount to be equal to the return displacement amount calculated from the position information of the robot. It is calculated by multiplying by a coefficient α (0 <α <1) determined from the tightening control information .

  In this bolt tightening device, the robot controller controls the operation of the robot, and the nut runner controller controls the operation of the nut runner so that the bolt is tightened at a predetermined position by pulse tightening. Here, the bolt run control information by the nut runner is transmitted from the nut runner controller to the robot controller. The tightening information includes a tightening torque, a tightening direction, a tightening speed, and the like.

Then, the robot controller Hazuki based on tightening information received from the nut runner controller, so as to reduce vibration of the robot generated when dated pulses tightening of the bolt, generates a control signal for controlling the operation of the robot The control signal is transmitted to the robot. Thereby, since the robot is controlled based on the control signal, the vibration of the robot can be reduced.

In the bolt tightening device according to the present invention, the control signal is the correction return displacement amount smaller than the return displacement amount for returning the robot to the original position with respect to the bolt tightening reaction force. It is a signal for returning the robot.

  When the robot controller generates such a control signal, the return position of the robot moved by the bolting reaction force is shifted, that is, the return position is closer to the front side than the original position. In other words, the return force of the robot is reduced. Thereby, it is possible to reliably prevent the robot from exceeding the original position during the return operation. Therefore, the vibration of the robot can be surely reduced.

Here, the modified return displacement amount, relative to the return displacement amount calculated from the position information of the robot, you calculated by multiplying a coefficient determined from the control information tightening α (0 <α <1) Is .

  In this way, an appropriate correction return displacement can be calculated according to the magnitude of the tightening torque (tightening reaction force), so that the robot does not exceed the original position during the return operation. The robot can be returned as close to the original position as possible.

  According to the bolt tightening device of the present invention, as described above, the vibration of the robot to which the nutrunner is attached can be reduced when the bolt is tightened by pulse tightening without taking mechanical measures. .

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a most preferred embodiment embodying a bolt fastening device of the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, a bolt tightening device according to a first embodiment will be described with reference to FIGS. FIG. 1 is a side view showing a schematic configuration of a bolt fastening device according to the first embodiment. FIG. 2 is a view showing the vicinity of a nut runner mounting portion in the bolt tightening device, (a) is a top view of the vicinity of the nut runner mounting portion, and (b) is a view showing the relationship between the tightening torque and the tightening reaction force. is there. FIG. 3 is a control block diagram of the bolt tightening device.

  As shown in FIG. 1, the bolt tightening device 10 according to the present embodiment includes a nut runner 20 that tightens bolts and a robot 30 that moves the nut runner 20 to a predetermined position. As shown in FIG. 2A, the nut runner 20 is attached to the arm tip of the robot 30 via the plate-like attachment frame 11. As shown in FIG. 2 (b), the attachment frame 11 is formed with a through long hole 12 for allowing a part (tip portion) of the nut runner 20 to pass therethrough. A plurality of screw holes 13 for fixing the nut runner 20 to the mounting plate 11 are provided around the through long hole 12. Thereby, the mounting position of the nut runner 20 in the mounting frame 11 can be adjusted.

  The tip of the nut runner 20 is capable of gripping the bolt and rotating in the tightening direction. The nut runner 20 is provided with a nut runner controller 21 (see FIG. 3). As shown in FIG. 3, the operation of the nut runner 20 is controlled by the nut runner controller 21. That is, the nut runner controller 21 controls the tightening operation of the nut runner 20 by an operation command based on bolt tightening information (including tightening torque, tightening direction, tightening speed, etc.) input from the outside. It is supposed to be.

  As shown in FIG. 1, the robot 30 for moving the nutrunner 20 to a predetermined position is a vertical articulated robot having a plurality of arms 31, 32, 33, and has x, y, and z axes. It can move in each axial direction. 2A, the attachment frame 11 is attached to the tip of the arm 33, and the nut runner 20 fixed to the attachment frame 11 moves in conjunction with the operation of the robot 30. Yes. The robot 30 is provided with a robot controller 35 (see FIG. 3).

  Then, as shown in FIG. 3, the operation of the robot 30 is controlled by the robot controller 35. That is, the robot controller 35 generates a control signal for the robot 30 based on a control command input from the outside, and transmits the control signal to the robot 30 so that the nutrunner 20 is positioned at a predetermined position. It is designed to control the operation. On the other hand, the robot 30 transmits information regarding the current position to the robot controller 35.

  In the bolt tightening device 10, the nut runner controller 21 and the robot controller 35 are connected. The nutrunner controller 21 transmits bolt tightening information input from the outside to the robot controller 35. The robot controller 35 issues an operation command to the robot 30 in consideration of the tightening information.

Here, when pulse tightening is performed by the bolt tightening device 10, if the bolt tightening direction is clockwise as shown in FIG. 2B, the reaction force is downward with respect to the robot 30 in the figure. Act on. This reaction force, will move the robot 30 is downward, since the position of the robot 30 will be without the robot 30 to return to the original position. If the bolt tightening device 10 does not take vibration suppression measures, which will be described later, in pulse tightening, the origin return force of the robot 30 and the tightening reaction force acting on the robot 30 work alternately. The robot 30 vibrates greatly like an attaching device.

  However, the bolt tightening device 10 controls the robot 30 so as to reduce the vibration of the robot 30 as described above. In other words, the bolt tightening device 10 does not take mechanical measures as in the prior art, but suppresses vibrations of the robot through control. Therefore, bolt tightening control in the bolt tightening device 10 will be described with reference to FIG. FIG. 4 is a flowchart showing the contents of bolt tightening control.

  In the bolt tightening device 10, first, the robot controller 35 grasps the current position of the robot 30 based on information from the robot 30 (step (hereinafter also referred to as “S”) 1). Then, the nut runner controller 21 controls the operation of the nut runner 20 based on the tightening information to start bolt tightening (pulse tightening) (step 2). Again, the robot controller 35 grasps the current position of the robot 30 based on information from the robot 30 (step 3). The current position of the robot 30 grasped in this step 3 is a position when the robot 30 is displaced due to a bolting reaction force.

  Next, the robot controller 35 calculates the amount of change (displacement) “A (x, y, z)” by which the robot 30 has moved due to the bolt tightening reaction force from the position information of the robot acquired in step 1 and step 3. (Step 4). Then, the robot controller 35 controls the robot 30 so as to return it to “A (x, y, z) × α”.

  Here, α is a coefficient of 0 <α <1 determined by bolt tightening information. Note that the value of α is determined such that the distance (the amount of positional deviation of the robot 30) that the robot 30 moves before reaching the final torque (predetermined tightening torque) is minimized. By returning the robot 30 by the amount of displacement “A (x, y, z) × α” multiplied by the coefficient α, the return force of the robot 30 moved by the bolting reaction force is reduced. . As described above, in the bolt tightening device 10, the operation of the robot 30 is controlled by the robot controller 35 so that the return force of the robot 30 is reduced. Here, after the robot 30 is moved by the bolting reaction force, when the return operation is performed to return to the original position, the robot 30 exceeds the original position, and thus the robot 30 is vibrated. End up. For this reason, since the return force of the robot 30 is reduced, it is possible to reliably prevent the robot 30 from exceeding the original position during the return operation. As a result, the vibration of the robot 30 can be reliably reduced.

  Furthermore, since the value of α is determined (changes) according to the magnitude of the tightening torque (tightening reaction force), the return displacement amount (corrected return displacement amount) of the robot 30 can be appropriately calculated. . As a result, the robot 30 can be returned as close to the original position as possible while preventing the robot 30 from exceeding the original position during the return operation.

  Thereafter, it is determined whether or not the bolt tightening torque is equal to or greater than the target torque (step 6). At this time, if the tightening torque is equal to or higher than the target torque (S6: YES), the tightening of the bolt is completed. On the other hand, if the tightening torque is less than the target torque (S6: NO), the process returns to step 1 and the above-described processes of S1 to S6 are repeated.

  As described above in detail, according to the bolt tightening device 10 according to the first embodiment, after the robot 30 moves due to bolt tightening, the origin return force that tries to return to the original position is small. Thus, the robot 30 returns to the original amount by a displacement “A (x, y, z) × α” that is smaller than the displacement “A (x, y, z)” moved by the tightening reaction force. As a result, the robot 30 does not exceed the original position during the return operation, so that the vibration of the robot 30 is reliably reduced.

(Second Embodiment)
Next, a second embodiment will be described. The bolt fastening device according to the second embodiment has the same device configuration as that of the first embodiment, but the bolt fastening control is different. Therefore, this point will be described below with reference to FIG. FIG. 5 is a flowchart showing the contents of bolt tightening control in the second embodiment.

  In the bolt tightening device according to the second embodiment, first, the nut runner controller 21 controls the operation of the nut runner 20 based on the tightening information to start bolt tightening (pulse tightening) (step 10). . Next, the robot controller 35 acquires bolt tightening information (step 11). The acquisition of the tightening information is performed when the robot controller 35 receives the tightening information transmitted from the nutrunner controller 21 to the robot controller 35.

  The robot controller 35 controls the operation of the robot 30 based on the acquired tightening information so that the robot 30 is driven in the direction opposite to the bolt tightening reaction force. As a result, as shown in FIG. 6, a driving force of the robot 30 is generated in the direction opposite to the tightening reaction force in synchronization with the generation of the bolt tightening reaction force. In this embodiment, considering the durability of the robot 30, the robot 30 is caused to generate a driving force of about 70% of the tightening reaction force. It should be noted that the driving force of the robot 30 generated in the direction opposite to the tightening reaction force may be within a range of about 60% to about 80% of the tightening reaction force. Since the driving force of the robot 30 cancels the bolting reaction force acting on the robot 30, the amount of movement (distance) of the robot 30 can be reduced and the robot 30 hardly moves. Thereby, the vibration of the robot 30 can be reliably reduced.

  Thereafter, it is determined whether or not the bolt tightening torque is equal to or greater than the target torque (step 13). At this time, if the tightening torque is equal to or higher than the target torque (S13: YES), the tightening of the bolt is completed. On the other hand, if the tightening torque is less than the target torque (S13: NO), the process returns to step 1 and the above-described processes of S10 to S13 are repeated.

  As described above, according to the bolt tightening device according to the second embodiment, when the bolt tightening reaction force acts on the robot 30, the tightening reaction is synchronized with the tightening reaction force. The operation of the robot 30 is controlled by the robot controller 35 based on the tightening information acquired from the nut runner controller 21 so that a driving force is generated in the direction opposite to the tightening reaction force to cancel the force. As a result, the amount (distance) of movement of the robot 30 by the tightening reaction force of the bolt can be reduced. Therefore, even if the tightening reaction force acts on the robot 30, the robot 30 hardly moves. Is reliably reduced.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.

It is a side view which shows schematic structure of the bolt fastening apparatus which concerns on 1st Embodiment. It is a figure which shows the nut runner attachment part vicinity in a bolt fastening apparatus, (a) is a top view of nut runner attachment part vicinity, (b) is a figure which shows the relationship between a fastening torque and a fastening reaction force. It is a control block diagram of a bolt fastening device. It is a flowchart which shows the content of bolt tightening control. It is a flowchart which shows the content of the bolt tightening control in 2nd Embodiment. It is a figure which shows the relationship between the clamping reaction force which acts on a robot, and the driving force of a robot. It is a figure which shows the relationship between time and torque in pulse fastening.

Explanation of symbols

10 bolt tightening device 11 mounting frame 20 nut runner 21 nut runner controller 30 robot 35 robot controller

Claims (2)

In the bolt tightening device that tightens the bolt by pulse tightening with the nut runner attached to the robot,
A robot controller for controlling the operation of the robot;
A nutrunner controller for controlling the operation of the nutrunner;
Have
The nutrunner controller transmits bolt tightening control information by the nutrunner to the robot controller,
The robot controller generates a control signal for controlling the operation of the robot based on the tightening control information so as to reduce vibration of the robot that occurs during pulse tightening of a bolt, and the control Send a signal to the robot ,
The control signal is a signal for returning the robot by a correction return displacement amount smaller than a return displacement amount for returning the robot to the original position with respect to a bolt tightening reaction force,
The corrected return displacement amount is relative to the return displacement amount calculated from the position information of the robot.
The bolt tightening device is calculated by multiplying by a coefficient α (0 <α <1) determined from the tightening control information . In the bolt fastening device according to claim 1,
The bolt tightening apparatus is characterized in that the coefficient α is determined so that the distance that the robot moves before reaching a predetermined bolt tightening torque is minimized .

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