JP2010201552A - Method of controlling fastening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a fastening device which reduces poorly fastened portions of a fastening member. <P>SOLUTION: In the method of controlling the fastening device, the switching step of placing one selected from a plurality of fastening parts at a predetermined position by driving a switching mechanism; the connection step of connecting a driving source to a rotary portion of the selected fastening part by driving an advance-retract mechanism; and the fastening step of fastening a screw of the selected fastening part by driving the driving source to rotate the rotary portion are carried out sequentially with respect to each of these fastening parts. The time limit of the fastening step for each of these fastening parts is set at a predetermined initial value T<SB>0</SB>. In the fastening step, an elapsed time from the start of fastening is measured. When the fastening of the screw is completed before the elapsed time reaches the time limit of the fastening step, a difference T<SB>1</SB>between the time limit of the fastening step and the elapsed time is obtained, and the difference T<SB>1</SB>is transferred and added to the time limit T<SB>0</SB>of the next fastening step, thereby terminating the fastening step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for controlling a tightening device. Specifically, the present invention relates to a method for controlling a tightening device that tightens a screw at a predetermined position of a workpiece.

2. Description of the Related Art Conventionally, in a manufacturing process of an automobile, a part is fixed to a work with a screw at a plurality of locations using a screw tightening device. For example, the screw tightening device can tighten up to six screws in a series of operations, has six tightening sockets, and selectively selects one of these tightening sockets. A socket switching mechanism positioned at a position; a tightening nut runner that is rotationally driven; and a feed mechanism that moves the tightening nut runner forward and backward relative to the tightening socket positioned at a predetermined position. Each clamping socket holds one screw.
According to this screw tightening device, first, the socket switching mechanism is driven to position one selected from the six tightening sockets at a predetermined position. Next, the feed mechanism is driven to connect the tightening nut runner to the selected tightening socket. Next, the tightening nut runner is driven to rotate the tightening socket, and the screw held in the tightening socket is tightened. This operation is sequentially performed for each of the six screws.

  However, in the above screw tightening device, when the screw is inserted into the tightening portion, the screw may be caught by the female screw portion of the tightening portion, and it may take time to tighten the screw. In this case, if it takes time to tighten the screw, there is a problem that the cycle time of the screw tightening device is prolonged.

Therefore, for each of the tightening processes of the six screws, the maximum time allocated to execute the tightening process is set as the time limit. This time limit is the same for all fastening parts. When tightening a screw, the elapsed time from the start of tightening is measured, and if the elapsed time reaches the time limit even if the tightening of the tightening member is not completed, the tightening of this screw is stopped. This tightening process is finished, and the next screw tightening is started. And about this poor fastening location, a screw is manually tightened by a post process.
According to this method, it is possible to prevent the time required for tightening one screw from being excessively long, and therefore it is possible to prevent the cycle time of the screw tightening device from being prolonged.

JP 2008-142824 A

  However, in this method, since the screw is manually tightened in a post-process at a tightening failure portion, work efficiency is lowered. For this reason, it is desirable to reduce the tightening defects as much as possible.

  An object of this invention is to provide the control method of the clamping device which can reduce the fastening defect location of a clamping member.

According to the control method of the tightening device (for example, a tightening device 1 described later) according to the present invention, the tightening device includes a plurality of tightening portions (for example, a tightening portion 30 described later) and the tightening is performed. A switching mechanism (for example, a switching mechanism 10 to be described later) that selectively positions one of the units at a predetermined position, a drive source for rotational driving (for example, a drive source 40 to be described later), and the drive source to the predetermined position An advancing / retreating mechanism (for example, an advancing / retreating mechanism 50 described later) that moves forward and backward with respect to the tightening portion positioned at a position, and each of the plurality of tightening portions is configured by the tightening member (for example, an after-mentioned A rotating portion (for example, a rotating portion 32 described later) that holds the screw S) and a holding portion (for example, a holding portion 31 described later) that rotatably holds the rotating portion. A cutting mechanism that drives the mechanism to position a selected one of the plurality of tightening portions at a predetermined position. A connecting step of driving the advance / retreat mechanism to connect the drive source to the rotating portion of the selected tightening portion, and driving the drive source to rotate the rotating portion to select the selected tightening portion. A tightening step of tightening the tightening members in order for each of the plurality of tightening portions, and for each of the plurality of tightening portions, a time limit for the tightening step is set to a predetermined initial value ( For example, it is set at T ₀ ) described later, and in the tightening process, the elapsed time from the start of tightening is measured, and the tightening member is tightened without the elapsed time reaching the time limit for the tightening process. When completed, a difference (for example, T ₁ and T ₂ described later) between the time limit of the tightening process and the elapsed time is obtained, and the difference is carried forward and added to the time limit of the next tightening process. The tightening step is completed, while the tightening member Without clamping is completed, when the elapsed time reaches the time limit step with the tightening, stop tightening of said fastening member, characterized in that it terminates with the clamping step.

According to the present invention, in the tightening step, the elapsed time from the start of tightening is measured, and when the tightening of the tightening member is completed without reaching the limit time, the time limit and the elapsed time are The difference is obtained, and this difference is carried over and added to the next time limit to complete the tightening process.
In this way, when the elapsed time has not reached the time limit when the tightening of the tightening member is completed, there is time, so this extra time is carried forward and added to the next time limit. As a result, in the next tightening step, the extended time limit is used, so that the tightening operation of the tightening member can be performed for a long time.

Therefore, tightening could not be completed before the elapsed time reached the initial value of the time limit, but tightening may be completed by continuing the tightening operation as it is. Therefore, it is possible to reduce the tightening failure location of the tightening member.
Even in this case, since the total time allocated for executing the tightening process of the tightening portion does not change, it is possible to prevent the cycle time from prolonging.

  According to the present invention, the tightening could not be completed until the elapsed time reached the initial value of the time limit, but the tightening may be completed by continuing the tightening operation as it is. Therefore, it is possible to reduce the tightening failure location of the tightening member. Even in this case, since the total time allocated for executing the tightening process of the tightening portion does not change, the cycle time can be prevented from being prolonged.

It is a perspective view showing the outline of the clamping device concerning one embodiment of the present invention. It is sectional drawing of the clamping apparatus which concerns on the said embodiment. It is a flowchart of operation | movement of the clamping apparatus which concerns on the said embodiment. It is a figure for demonstrating operation | movement of the clamping apparatus which concerns on the said embodiment. It is a timing chart of the clamping device concerning the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing an outline of a fastening device 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the tightening device 1.
The tightening device 1 is a device for tightening a screw S as a tightening member, and is provided at the tip of the robot arm 2. The tightening device 1 includes six tightening portions 30, a switching mechanism 10 that arranges one of the tightening portions 30 at a predetermined position, a drive source 40 that rotates, and a drive source 40. An advancing / retreating mechanism 50 that is connected to the tightening portion 30 at a predetermined position, and a control device 60 that controls these mechanisms are provided.

  The robot arm 2 is controlled by the control device 60 and changes the position and posture of the tightening device 1 in the three-dimensional space.

The switching mechanism 10 is supported on the tip flange surface of the robot arm 2 via the mounting bracket 20.
The switching mechanism 10 includes a cylindrical holder 11, six fastening portions 30 disposed on the outer peripheral surface of the holder 11, one sensing unit 12 disposed on the outer peripheral surface of the holder 11, and the holder 11. And a holder driving unit 13 that rotates the holder.

The holder driving unit 13 is fixed to the mounting bracket 20 and is driven by the control device 60.
The holder 11 is attached to the drive shaft of the holder drive unit 13. By driving the holder driving unit 13, the holder 11 rotates in the arrow A direction or the arrow B direction with the central axis as the rotation center, and moves the tightening unit 30 and the sensing unit 12.

  The sensing unit 12 includes a CCD camera and is connected to the control device 60. The sensing unit 12 transmits an image captured by the CCD camera to the control device 60.

  The tightening portion 30 is rotatably supported by the holder 11 with the rotation axis Z as a rotation center. The tightening portion 30 includes a holding portion 31 fixed to the holder 11, a rod-like rotating portion 32 that is rotatably held by the holding portion 31 and holds the screw S, and the holding portion 31 and the rotating portion 32. And a spring 33 interposed therebetween.

The holding portion 31 has a cylindrical shape, and a ball spline 311 is provided inside the holding portion 31. The rotating portion 32 is inserted through the holding portion 31 and supported by the ball spline 311 so as to be rotatable and advanceable / retreatable.
The spring 33 is interposed between the proximal end surface of the holding portion 31 and the proximal end side of the rotating portion 32, and the rotating portion 32 is urged in the backward direction by the spring 33.

  The drive source 40 is disposed behind the holder 11 (right direction in FIG. 1) and includes a rotation drive unit 41. The distal end of the rotation drive unit 41 has a shape that can be fitted to the proximal end side of the rotation unit 32. The rotation axis X of the rotation drive unit 41 is substantially parallel to the rotation axis of the holder 11.

  The advance / retreat mechanism 50 is provided on the mounting bracket 20, and is controlled by the control device 60 to advance or retract the drive source 40 along the rotation axis X. The advance / retreat mechanism 50 includes a pair of cylinder mechanisms 51 and a pair of slide guides 52.

  The pair of cylinder mechanisms 51 includes a piston rod 511 attached to the drive source 40 and a cylinder 512 provided on the attachment bracket 20 to advance and retract the piston rod 511.

  The pair of slide guides 52 includes a slide beam 521 attached to the drive source 40 and a slide guide 522 provided on the attachment bracket 20 and through which the slide beam 521 is inserted. The pair of slide guides 52 guide the forward / backward movement of the drive source 40 as the slide beam 521 slides in the slide guide 522.

  According to the advance / retreat mechanism 50, the drive source 40 advances and retracts along the rotation axis X of the rotation drive unit 41 by driving the pair of cylinder mechanisms 51.

Therefore, when the advance / retreat mechanism 50 is driven to advance the drive source 40, the drive source 40 is connected to the proximal end side of the rotating portion 32. When the drive source 40 is further advanced, the rotating portion 32 moves forward while resisting the urging force of the spring 33.
Next, when the drive source 40 is driven to rotate, the rotating unit 32 rotates, and the screw S is tightened.
Thereafter, when the advance / retreat mechanism 50 is driven to retract the drive source 40, the rotating portion 32 is retracted by the restoring force of the spring 33 and returns to the original position. When the drive source 40 is further retracted, the connection between the drive source 40 and the rotating unit 32 is released.

The rotating part 32 includes a shaft part 34, a guide part 35, a bit part 36, and a spring 37.
A joint portion 341 is provided on the proximal end side of the shaft portion 34. The above-described drive source 40 can be connected to the joint portion 341.

  The guide portion 35 has a cylindrical shape, and the distal end side of the shaft portion 34 is connected to the proximal end side of the guide portion 35. Thereby, the rotational force of the shaft portion 34 is transmitted to the guide portion 35.

The proximal end side of the bit portion 36 is inserted into the distal end side of the guide portion 35. The outer peripheral surface of the base end side of the bit portion 36 and the inner peripheral surface of the guide portion 35 are similar to each other, and further, between the outer peripheral surface of the base end side of the bit portion 36 and the inner peripheral surface of the guide portion 35. A slight gap is formed.
Thereby, the bit part 36 is loosely fitted to the guide part 35 and can float. When the guide part 35 rotates, the bit part 36 rotates in accordance with the rotation of the guide part 35.
A shaft portion 34 is inserted on the base end side of the bit portion 36.

  A socket 361 for holding the screw S is formed on the distal end side of the bit portion 36. The bottom surface of the socket 361 is a magnet, and the screw S is held by the magnetic force of the magnet.

  The spring 37 is built in the guide portion 35 and is disposed along the shaft portion 34. The distal end side of the spring 37 is housed on the proximal end side of the bit portion 36 and urges the bit portion 36 in the forward direction.

  In the rotating portion 32, even if an axial pressing force acts on the socket 361, the bit portion 36 moves backward while resisting the urging force of the spring 37, thereby reducing the pressing force. When the pressing force is released, the bit portion 36 returns to the original position by the restoring force of the spring 37.

Next, operation | movement of the above-mentioned clamping apparatus 1 is demonstrated, referring the flowchart of FIG.
In the following description, numbers are assigned to the six tightening portions 30, and the six tightening portions 30 are constituted by the first to sixth tightening portions 30. Further, for each of the first to sixth tightening portions 30, a time limit for tightening the screw S is set with a predetermined initial value.
In ST1, a variable n representing the number of the tightening portion 30 is set to 1 as an initial setting.

In ST2, the robot arm 2 is controlled by the control device 60, the obstacle 1 is avoided, and the tightening device 1 is moved to the vicinity of the attachment position of the screw S.
In ST3, as shown in FIG. 1, the holder driving unit 13 is driven to rotate the holder 11, and the sensing unit 12 is arranged on the rotation axis X of the driving source 40.
In ST 4, the sensing position is sensed by the sensing unit 12 and output to the control device 60.

In ST5, the control device 60 controls the robot arm 2 based on the detection result of the sensing unit 12, and corrects the position of the tightening device 1.
Specifically, the correction value is obtained by comparing the position data of the attachment position detected by the sensing unit 12 with the position data of the rotation axis X, and the screw S is attached on the rotation axis X based on the correction value. The robot arm 2 is controlled so that the position is located.

  In ST6, simultaneously with this position correction, the holder driving unit 13 is driven to rotate the holder 11, and the n-th tightening unit 30 is positioned on the rotation axis X of the driving source 40 in the sensing unit 12.

  In ST7, as shown in FIG. 4, the advance / retreat mechanism 50 is driven to advance the drive source 40, and the rotation drive unit 41 of the drive source 40 is connected to the rotation unit 32 of the n-th tightening unit 30. To do.

  In ST8, the drive source 40 is further advanced by resisting the urging force of the spring 33, the screw S held by the tightening portion 30 is protruded from the front surface of the tightening device 1, and the screw S is attached to the mounting position. And the rotation drive unit 41 of the drive source 40 starts to be driven. Then, due to the rotational force of the rotation drive unit 41, the rotation unit 32 of the n-th tightening unit 30 starts to rotate.

  In ST9, it is determined whether or not the tightening of the screw S has been completed. Specifically, it is determined whether or not the tightening torque of the screw S is greater than or equal to a predetermined value. If this determination is NO, the process moves to ST10, and if it is YES, the process moves to ST11.

In ST10, the elapsed time from the start of tightening the screw S is measured, and it is determined whether or not this elapsed time has reached the time limit.
If this determination is NO, since the tightening of the screw S has not been completed and the elapsed time has not reached the time limit, the tightening of the screw S is continued, and the process returns to ST9. On the other hand, when this determination is YES, since the elapsed time has reached the time limit without completing the tightening of the screw S, the process proceeds to ST12.

  In ST11, since the tightening of the screw S is completed without the elapsed time reaching the time limit, the difference between the time limit and the elapsed time is obtained, and this difference is carried forward to the next (n + 1) th tightening portion 30. Add to the time limit for the tightening process. That is, the time remaining due to the tightening of the screw S is added to the time limit for the next tightening process.

  In ST12, the drive of the rotation drive unit 41 of the drive source 40 is stopped, and the rotation of the rotation unit 32 is stopped.

  In ST13, the advance / retreat mechanism 50 is driven, and the rotation drive unit 41 of the drive source 40 is moved backward. Then, due to the restoring force of the spring 33, the rotating part 32 moves backward and the tightening part 30 returns to the original position. Subsequently, the drive source 40 is further retracted, and the connection between the rotation drive unit 41 of the drive source 40 and the rotation unit 32 of the tightening unit 30 is released.

In ST14, it is determined whether n is 6. That is, it is determined whether or not the sixth tightening portion 30 has been tightened. If this determination is YES, the process ends. If NO, the process proceeds to ST15.
In ST15, the value of n is incremented by 1, and the process returns to ST2.
In this way, the operations of ST2 to ST13 are performed for all the fastening portions 30.

FIG. 5 is a timing chart of the tightening device 1. Here, the initial value of the time limit, and all T _0.
Period from time _{t 0} to time _{t 1} corresponds to the above-mentioned ST1 to ST3. During this period, the fastening device 1 is moved to the vicinity of the attachment position and switched to the sensing unit 12.
Period from time _{t 1} to time _{t 2} corresponds to ST4 described above. During this period, the attachment position is sensed by the sensing unit 12.

Period from time _{t 2} to time _{t 3} corresponds to the above ST5, ST6. In this period, the first tightening unit 30 is switched.
Period from time _{t 3} to time _{t 4} corresponds to ST7 above. In this period, the drive source 40 is connected to the rotating part 32 of the first fastening part 30.

Period from time _{t 4} to time _{t 5} corresponds to the above-described ST8～ST15. In this period, the drive source 40 is driven and the screw S is tightened. While tightening the time limit screw S is T _0, since the completion of the tightening of the screw S in a shorter time than the time limit T _0, the difference T ₁ of the elapsed time and the limit time T _0, the second-order It adds the time limit _{T 0} of the tightening portion 30, the next time limit and _(T 0 + T _1).

During the period from time t ₅ to time t ₁₀ , the same operation as the period from time t ₀ to time t ₅ is performed on the second tightening unit 30.
Here, in the period from time t ₉ to the time t _10, by driving the drive source 40, performs fastening screws S. Since the time limit for tightening the screw S is longer than T ₀ (T ₀ + T ₁ ), the tightening of the screw S is continued even after the elapsed time T ₀ and the tightening of the screw S is completed. At this time, the difference T ₂ between the time limit (T ₀ + T ₁ ) and the elapsed time is added to the next time limit T ₀ .

According to this embodiment, there are the following effects.
(1) In the tightening process, the elapsed time from the start of tightening is measured, and when the tightening of the screw S is completed without the elapsed time reaching the limit time, the difference between the limit time and the elapsed time is obtained. The difference is carried forward and added to the next time limit to complete the tightening process.
Thus, when the elapsed time has not reached the time limit when the tightening of the screw S is completed, there is time, so this extra time is carried forward and added to the next time limit. Thus, in the next tightening process, the extended time limit is used, so that the screw S can be tightened for a long time.

Therefore, although the tightening could not be completed before the elapsed time reached the initial value of the time limit, the tightening may be completed by continuing the tightening operation as it is. .
Even in this case, since the total time allocated for executing the tightening process of the tightening unit 30 does not change, it is possible to prevent the cycle time from prolonging.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in this embodiment, since the fastening member held by the fastening part 30 is of a single type, the initial values of the time limits are all set to the same value T ₀ , but the present invention is not limited to this. That is, when a plurality of types of tightening members are held by the tightening unit 30, the initial value of the time limit may be varied depending on the type of tightening member.

S screw (clamping member)
DESCRIPTION OF SYMBOLS 1 Tightening apparatus 10 Switching mechanism 30 Tightening part 31 Holding part 32 Rotating part 40 Drive source 50 Advance / retreat mechanism

Claims (1)

A method of controlling a tightening device for tightening a tightening member,
The tightening device includes a switching mechanism having a plurality of tightening portions and selectively positioning one of the tightening portions at a predetermined position, a drive source for rotational drive, and the drive source An advancing and retreating mechanism configured to advance and retreat with respect to the tightening portion located at a predetermined position,
Each of the plurality of tightening portions includes a rotating portion that holds the tightening member, and a holding portion that rotatably holds the rotating portion;
A switching step of driving the switching mechanism to position the selected one of the plurality of tightening portions at a predetermined position;
A connecting step of driving the advance / retreat mechanism to connect the drive source to the rotating part of the selected tightening part;
A tightening step of driving the drive source to rotate the rotating portion to tighten the tightening member of the selected tightening portion;
In turn for each of the plurality of tightening portions,
For each of the plurality of tightening portions, a time limit for the tightening process is set at a predetermined initial value,
In the tightening process, the elapsed time from the start of tightening is measured, and when the tightening of the tightening member is completed without the elapsed time reaching the time limit for the tightening process, Find the difference between the time limit and the elapsed time, carry over the difference and add it to the time limit of the next tightening process, and end the tightening process,
On the other hand, when the elapsed time reaches the time limit for the tightening process without completing the tightening of the tightening member, the tightening of the tightening member is stopped and the tightening process is completed. A method for controlling a tightening device.

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