JP2006341323A - Workpiece holding device and holding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a workpiece holding device having a simple configuration, requiring no complex control and generating no distortion even if a workpiece has comparatively low rigidity. <P>SOLUTION: The holding device 20 for holding and fixing the workpiece 10 to a holding base 21 is equipped with: at least three arms 31, 31, 31 pressing the workpiece 10 to the holding base side, a power cylinder 33 moving respective arms 31 to the forward and backward direction with respect to the workpiece 10; a means for detecting the contact of the arm 31 to the workpiece 10; and a control device 40 for controlling the operation of the cylinders 33. When it is detected that any of the arms 31 approaches and abuts on the workpiece 10, the movement of the arms 31 is stopped. When it is detected that all of the arms 31, 31, 31 abut on the workpiece 10, all of the arms 31, 31, 31 are approximately synchronized and moved at approximately the same speed by approximately the same width, and a pressing force relative to the workpiece 10 is increased at approximately the same time and with approximately the same degree. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a holding method suitable for holding a workpiece having a relatively low rigidity and a long length, such as a connecting rod, and a holding device that realizes the holding method.

  As shown in FIG. 1, the connecting rod 10, which is a constituent member of an automobile internal combustion engine, includes a first end portion 11 in which a small through hole 12 is formed, a second end portion 13 in which a large through hole 14 is formed, It is a long object having a body portion 15 that connects the first end portion 11 and the second end portion 13. A pin for connecting the connecting rod 10 to the piston is inserted into the small through hole 12 of the first end 11, and a crankshaft is inserted into the large through hole 14 of the second end 13.

  In the production of the connecting rod, a crushing process for crushing and expanding the end part of the workpiece (molded product to be a connecting rod), a drilling process for drilling a through hole in the expanded end part, etc. Applied. The crushing work stage and the drilling stage are connected by a belt conveyor, and the workpiece conveyed to the drilling stage by the belt conveyor is gripped by a robot and drilled from the belt conveyor. It is transferred to.

  In the above transport process, in general, the workpiece is directly placed on the belt conveyor at random, but in Patent Document 1, the molded product is not placed directly on the belt conveyor, but held in a standing posture on the jig. A transport vehicle for placing and transporting in a state has been proposed.

The transport vehicle described in Patent Document 1 includes a pocket portion that accommodates and holds one side end portion of the lower side of the workpiece to be transported, and a gripping mechanism that grips the trunk portion of the workpiece. The workpiece is conveyed in a standing posture. As a result, the workpiece can be conveyed by the belt conveyor without damaging the workpiece, and the workpiece is held in an upright posture, so that the robot reliably holds a predetermined portion of the workpiece in the next process after being conveyed. It is possible to increase the accuracy of the through hole formed by the drilling process.
JP 2004-196541 A

  When the workpiece is gripped by a jig that holds a workpiece with low rigidity such as a connecting rod, the workpiece may be deformed if the workpiece receives a biased load. Therefore, the mechanism for gripping the work needs to be devised for uniformly applying a load to the work.

  In the technique described in Patent Document 1, a pair of clamp claws for gripping a workpiece are configured to open and close in conjunction with each other, and when the workpiece is gripped by the clamp claws, a biasing force is applied to the clamp claws. A coil spring is adopted as a member for providing the resistance. Thus, when the workpiece is held in contact with two points, the load is less likely to be biased and the configuration is simple.

  However, when contacting the workpiece at multiple points, the load applied to the workpiece is likely to be biased, and the workpiece will be distorted unless the gripping timing is synchronized or the gripping force balance is adjusted. Causes inaccuracy.

  For example, it is conceivable to employ a hydraulic cylinder as a drive source for a gripping mechanism that grips a workpiece at multiple points. In addition, complicated control such as flow rate adjustment control and pressure reduction control is required. For this reason, the work for adjusting the degree of control is complicated, resulting in inconveniences such as a long working time and a complicated hydraulic circuit.

  Therefore, the present invention is a device for holding and fixing a workpiece with relatively low rigidity without causing distortion, such as two-stage pressure control of a hydraulic circuit, flow rate adjustment control, pressure reduction control, etc. We propose a simple configuration that does not require complicated control.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, according to the first aspect of the present invention, in the holding device for holding and fixing the workpiece to the holding table, at least three arms capable of pressing the workpiece to the holding table side, and the arms in a direction to advance and retreat with respect to the workpiece. An electric cylinder to be moved; a means for detecting that the arm is in contact with a work; and a control means for controlling the operation of the electric cylinder based on the operating state of the arm. If it is detected that the arm is in contact with the workpiece, the movement of the arm is stopped, and after it is detected that all the arms included in the holding device are in contact with the workpiece, all the arms are synchronized. The electric cylinder is operated so as to move to the holding table side.

  According to a second aspect of the present invention, the control means holds the pressing force of the arms against the workpieces at a predetermined size substantially constant until the arms contact the workpieces. After contacting the workpiece, the limit value of the thrust of the electric cylinder is changed so that the pressing force of all the arms against the workpiece is increased substantially simultaneously and approximately the same.

  According to a third aspect of the present invention, the control means sets in advance a pressing force with such a magnitude that the workpiece is not deformed by the contact of the arm as a limit value of the thrust after the electric cylinder is lifted according to the workpiece. is there.

  According to a fourth aspect of the present invention, there is provided a holding table, at least three arms capable of pressing the workpiece toward the holding table, an electric cylinder for moving the arms in a direction to advance and retreat with respect to the workpiece, and the arms as the workpiece. A method of holding a workpiece by a holding device having means for detecting contact and control means for controlling the operation of the electric cylinder based on the operating state of the arm, wherein all the arms are held The process of moving in a direction approaching the work placed at a predetermined position, the process of stopping the movement of each arm when the arm touches the work, and all the arms touching the work Then, the process of moving all the arms in the direction of pressing the workpiece by substantially the same width at substantially the same speed in a substantially synchronized manner is included.

  As effects of the present invention, the following effects can be obtained.

According to the first aspect of the present invention, the workpieces are pressed from the respective arms toward the holding table with substantially the same load, and the workpiece is generated by fixing the workpiece to the holding table because the load is not biased to the workpiece. Distortion can be reduced. Since distortion does not occur in the workpiece, the positional accuracy can be increased in the machining performed on the workpiece held by the holding device, which can contribute to the improvement of the machining accuracy.
In addition, since the means for driving the arm is an electric cylinder, the configuration of the apparatus can be simplified as compared with the case of using a hydraulic cylinder, and there is no need to consider the time lag of hydraulic operation of the cylinder. Thus, the control configuration can be simplified.

  In claim 2, since it is confirmed that all the arms are in contact with the workpiece, the pressing force of all the arms against the workpiece is increased substantially at the same time. It is possible to prevent the workpiece from being distorted.

  According to the third aspect of the present invention, the maximum value of the pressing force of the arm against the workpiece becomes a value that does not deform the workpiece, and the workpiece can be held by the holding device without being deformed.

  According to the fourth aspect of the present invention, the workpieces are pressed from the respective arms to the holding table with substantially the same load, and the workpiece is generated by fixing the workpiece to the holding table because the load is not biased and applied to the workpiece. Distortion can be reduced. Since distortion does not occur in the workpiece, the positional accuracy can be increased in the machining performed on the workpiece held by the holding device, which can contribute to the improvement of the machining accuracy.

Next, embodiments of the invention will be described.
FIG. 1 is a view showing a connecting rod as an example of a work held by a holding device.
2 is a front view of the holding device according to the embodiment of the present invention, FIG. 3 is a side view of the holding device, and FIG. 4 is an enlarged view of the holding tool.
FIG. 5 is a block diagram showing the control configuration of the holding device, FIG. 6 is a diagram showing the flow of control in the holding device, and FIG. 7 is a diagram for explaining the relationship between the movement width of the rod and time.

The holding device 20 according to the embodiment of the present invention will be described.
The holding device 20 is a device that holds a lightweight work 10 with relatively low rigidity such as a connecting rod, and a force required to support the work 10 is relatively small (for example, 1000 N or less per support point). This is suitable for the case where the force of the magnitude that can be generated by the electric cylinder) and the positional accuracy of the processed part in the workpiece 10 are required. In this embodiment, the work 10 held by the holding device 20 is a connecting rod, but the work 10 is not limited to the connecting rod.

  As shown in FIG. 1, a workpiece 10 that is a holding object of a holding device 20 in this embodiment is a molded product that becomes a connecting rod that is a constituent member of an internal combustion engine of an automobile, and the molded product is a first end portion 11. And a second end portion 13, and a body 15 that is thinner than these end portions is formed between the first end portion 11 and the second end portion 13. A small through-hole 12 is formed in the first end 11 of the molded product, and a large through-hole 14 is formed in the second end 13 to serve as a member that functions as a connecting rod.

  As shown in FIGS. 2 and 3, the holding device 20 is provided with a work piece for making a small through hole 12 in the first end portion 11 and a large through hole 14 in the second end portion 13 of the work 10. 10 functions as a jig for holding 10 in a relatively unmovable manner with respect to the holding device 20.

  However, the holding device 20 is not only used as a jig for drilling, but also, for example, as a conveying jig for holding the posture when the workpiece 10 is conveyed by a belt conveyor or the like. Further, it can be used as a processing jig for use in processing such as cutting, and further as an assembly jig for holding the workpiece 10 in a predetermined position at the time of assembly with other parts.

The holding device 20 mainly includes a holding table 21 that serves as a base of the holding device 20 and holds the workpiece 10, and a plurality of holding tools 22 provided on the holding table 21.
In the present embodiment, since the holding device 20 supports and supports the workpiece 10 at three points, three sets of holding tools 22 are provided. The work 10 is pressed and supported at one point by the holding tool 22 (22A) at the first end 11 and is pressed and supported at two points by the holding tool 22 (22B and 22C) at the second end 13. As a result, it is held immovable relative to the holding table 21.

The holding table 21 is provided with a plurality of contact seats 26, 26,. The contact seats 26 are configured to be detachable from the holding base 21, and the number and arrangement of the corresponding contact seats 26 are appropriately adjusted according to the shape of the workpiece 10. Further, it is preferable that at least the contact portion of the contact seat 26 is made of a material (for example, resin or rubber) that can be somewhat elastically deformed.
One side surface of the work 10 comes into contact with the contact seat 26, and the work 10 is pressed from the other side surface to the contact seat 26 side by the holding tool 22, so that between the contact seat 26 and the holding tool 22, The workpiece 10 is clamped.
The abutment seat 26 may be a movable knock that can be moved back and forth with respect to the workpiece 10 from the holding table 21.

  Further, the holding base 21 is provided with detachable regulating bodies 28 and 28 arranged at positions where the second end 13 of the workpiece 10 is sandwiched from the side. When the side portion of the work 10 abuts against these regulating bodies 28 and 28, the shake of the work 10 on the holding base 21 is restricted, and the position in the left-right direction on the holding base 21 is determined.

  The holder 22 mainly includes an arm 31, a rod 32, and a cylinder 33. The arm 31 contacts the workpiece 10 and pressurizes the workpiece 10 toward the contact seat 26 provided on the holding table 21. A rod 32 is inserted into the cylinder 33 such that the rod 32 can expand and contract and can rotate by a predetermined angle, and the arm 31 is fixed to the rod 32. As a result, the arm 31 can move in a direction to advance and retreat with respect to the workpiece 10 and can rotate about the rod 32.

  As shown in FIG. 4, the holding base 21 is provided with a long hole 27, in which the rod 32 can be rotated and slidable in the extending and contracting direction of the rod 32. The inserted cylinder 34 is inserted. The cylindrical body 34 can freely move in the long hole 27.

  The cylinder 33 is provided on the opposite side of the arm 31 via the holding table 21, and is supported by the holding device 20 provided on the holding table 21 via the slide mechanism 35. The slide mechanism 35 is composed of, for example, a slider and a rail. The cylinder 33 can be moved in the longitudinal direction of the long hole 27 provided in the holding table 21 by the slide mechanism 35.

  The position of the arm 31 can be changed in accordance with the shape of the workpiece 10 by the long hole 27 formed in the holding table 21 and the slide mechanism 35 that allows the cylinder 33 to move.

  As shown in FIG. 5, the cylinders 33, 33, and 33 that rotate and extend / contract the rods 32, 32, and 32 are electrically connected to a single control device 40, respectively. To work. An amplifier 39 is provided between each cylinder 33 and the control device 40, and when the cylinder 33 is operated to drive the rod 32 to extend and contract, the load applied to the cylinder 33 is expanded by the amplifier 39 and the control device. 40 is detected.

A load value applied to the cylinder 33 is preset in the control device 40 when the arm 31 comes into contact with the workpiece 10 by the expansion / contraction operation of the rod 32, and is detected by the control device 40 during the expansion / contraction operation of the rod 32. If the load value becomes the set load value, the control device 40 determines that the arm 31 is in contact with the workpiece 10.
Therefore, the amplifier 39 and the control device 40 constitute means for detecting that the arm 31 has come into contact with the workpiece 10.

  The cylinder 33 is an electric cylinder. That is, in response to an electrical signal from the control device 40, a servo motor (not shown) operates to expand and contract the rod 32 and rotate the rod 32. Since the cylinder 33 is an electric cylinder, the configuration of the apparatus can be simplified compared to the case of using a hydraulic cylinder, and it is not necessary to consider the time lag of the hydraulic operation of the cylinder. It can be.

  Next, the control of the holding tool 22 by the control device 40 of the holding device 20 will be described with reference to the flowchart of FIG. 6 and FIG. FIG. 7 shows the relationship between the movement width of the rod 32 expanded and contracted by the cylinder 33 and time.

In the holding device 20 in the standby state, each holding tool 22 is adjusted in advance by the slide mechanism 35 so as to be in an appropriate position with respect to the work 10, and the arm 31 of each holding tool 22 is not engaged with the work 10 (rod) It is in a standby phase (rotation phase indicated by a two-dot chain line in FIG. 2) that does not overlap when viewed from the direction of expansion and contraction of 32. Each rod 32 is in an extended state.
While positioning the left and right positions of the workpiece 10 with the left and right regulating bodies 28 and 28 on the holding device 20 in the standby state, the workpiece 10 is set so that one surface thereof is in contact with the contact seat 26. The position where the workpiece 10 is set becomes the holding position of the workpiece 10.

  As described above, in the state where the workpiece 10 is set at the holding position, first, the control device 40 keeps the extended state without causing the rod 32 to expand and contract (points a to b shown in FIG. 7). Each cylinder 33 is controlled to rotate so that each rod 32 is rotated by a predetermined angle until the arm 31 of each holder 22 reaches a holding phase applied to the workpiece 10 (rotation phase indicated by a solid line in FIG. 2). (S10). The rotation angle of each rod 32 at this time is preset, and is approximately 45 degrees in this embodiment.

As described above, each arm 31 rotated to the holding phase is separated from the workpiece 10. Subsequently, each cylinder 33 is controlled by the control device 40 so as to shorten each rod 32 (S11), and each rod 32 moves at a substantially constant speed (points b to c shown in FIG. 7). ).
At this time (until the arm 31 comes into contact with the workpiece 10), the limit value of the thrust of the cylinder 33 is set to a value that does not distort the workpiece so that the pressing force of the arm 31 against the workpiece 10 is substantially constant. 10 is held substantially constant at a predetermined value set in the control device 40 in advance.

When each rod 32 is shortened and each arm 31 approaches the workpiece 10 and eventually the arm 31 comes into contact with the workpiece 10, a load is applied to the cylinder 33, and this load is detected by the control device 40 via the amplifier 39. (S12). The operation of the cylinder 33 is controlled by the control device 40 so as to stop the drive of the rod 32 of the arm 31 that has been detected to be in contact with the workpiece 10 (S13).
As described above, in this case, the control device 40 has a preset load value applied to the cylinder 33 when the arm 31 comes into contact with the workpiece 10 due to the expansion and contraction of the rod 32, and is detected by the control device 40. When the set load value becomes the set load value, the control device 40 determines that the arm 31 has come into contact with the workpiece 10, and stops the driving of the rod 32.

  The time until each arm 31, 31, 31 abuts against the workpiece 10 is usually different, and the operation of the arm 31 that abuts against the workpiece 10 stops until all the arms 31, 31, 31 abut against the workpiece 10. (Points c to d shown in FIG. 7).

  Then, when it is detected that all the arms 31, 31 and 31 have contacted the workpiece 10 (S14), all the arms 31 are then contacted in synchronism with substantially the same width at approximately the same speed. In order to shorten the rod 32 so as to move to the seat 26 side, the operation of the cylinder 33 is controlled by the controller 40 (S15), and each rod 32 moves by a substantially constant width Lα at a substantially constant speed (see FIG. D point to e point shown in FIG.

The moving speed and the moving width Lα of the rod 32 at this time are set in the control device 40 in advance. However, the moving width of the rod 32 is not set, and the shortening drive of the rod 32 can be controlled to stop when the load received by the arm 31 reaches a predetermined value.
Since the holding device 20 employs an electric cylinder as the driving means for the arm 31, it is possible to reduce a relative delay in the operation of each arm 31, 31, 31.

  In addition, after confirming that all the arms 31, 31 and 31 are in contact with the workpiece 10, the pressing force of all the arms 31, 31, and 31 against the workpiece 10 is substantially synchronized and rises to approximately the same level. In addition, the driving of the cylinders 33, 33, 33 is controlled so that the thrust limit values of all the cylinders 33, 33, 33 are increased and changed substantially at the same time and approximately the same.

  The limit value of the thrust after the cylinder 33 is raised is a value that does not cause deformation of the work due to the contact of the arm, and is set in advance in the control device 40 in accordance with the work 10. In the case where the workpiece 10 is a connecting rod as in this embodiment, if the limit value of thrust after ascending for each cylinder 33 is about 800 N, the connecting rod 20 can be held without causing distortion. .

  As described above, the workpiece 10 is held between the abutment seats 26, 26,... And the arms 31, 31,. The device 20 holds it. In the process until the workpiece 10 is held by the holding device 20, the workpiece 10 is pressed from the arms 31, 31, 31 to the holding table 21 side with substantially the same load, and is biased toward the workpiece 10. Since no load is applied, distortion caused by gripping the workpiece can be reduced.

  Since the workpiece 10 held by the holding device 20 is not distorted, the positional accuracy of the machining performed on the workpiece 10 held by the holding device 20 can be increased, which contributes to the improvement of the machining accuracy. it can.

The figure which shows the connecting rod as an example of the workpiece | work hold | maintained at a holding | maintenance apparatus. The front view of the holding | maintenance apparatus which concerns on the Example of this invention. The side view of a holding device similarly. The enlarged view of a holder. The block diagram which shows the control structure of a holding | maintenance apparatus. The figure which shows the flow of control in a holding | maintenance apparatus. The figure explaining the relationship between the movement width of a rod, and time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Work 20 Holding device 21 Holding stand 22 Holder 26 Contact seat 27 Elongate hole 28 Restrictor 31 Arm 32 Rod 33 Cylinder 35 Slide mechanism

Claims (4)

In a holding device that holds and fixes a workpiece on a holding table,
At least three arms capable of pressing the workpiece toward the holding table;
An electric cylinder for moving each arm in a direction to advance and retreat with respect to the workpiece;
Means for detecting that the arm is in contact with the workpiece;
Control means for controlling the operation of the electric cylinder based on the operating state of the arm,
The control means includes
If it is detected that any of the arms is in contact with the workpiece, the movement of the arm is stopped,
After it is detected that all the arms included in the holding device are in contact with the workpiece, all the arms are moved to the holding table side in synchronization.
Operate the electric cylinder,
A workpiece holding device. The control means includes
Until the arm comes into contact with the workpiece, the pressing force of each arm against the workpiece is held substantially constant at a predetermined magnitude,
After all the arms included in the holding device have come into contact with the workpiece, the pressing force of all the arms against the workpiece is increased substantially simultaneously and approximately the same.
Change the limit value of the thrust of the electric cylinder,
The workpiece holding device according to claim 1. In the control means, a pressing force having a magnitude that does not cause deformation of the work due to the contact of the arm is set in advance according to the work as a limit value of the thrust after the electric cylinder is raised,
The workpiece holding device according to claim 2. A holding table, at least three arms that can press the workpiece toward the holding table, an electric cylinder that moves each arm in a direction to move forward and backward with respect to the workpiece, and detecting that the arm is in contact with the workpiece And a holding device comprising a control unit that controls the operation of the electric cylinder based on the operating state of the arm,
A process of moving all the arms in a direction approaching a work placed at a predetermined position of the holding table;
In each arm, the process of stopping the movement of the arm if the arm comes into contact with the workpiece,
After all the arms are in contact with the workpiece, the process of moving all the arms in the direction of pressing the workpiece by substantially the same width at substantially the same speed by substantially synchronizing,
A method for holding a workpiece, comprising:

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