JP2004106095A - Work positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device giving less impact in the operation of clamping by simultaneously providing buffer effects, when claws of a positioning device clamp a work, to a plurality of claws to a same extent in a simple constitution and accurately positioning it. <P>SOLUTION: Fingers 22 disposed opposite to each other are deformed by a cam plate 14 having a cam groove 19, and a torsion spring 20 engaged with the cam plate only when a motor head 9 rotates in the closing direction and transmitting a power to the cam plate 14 is interposed between the motor head 9 driving the cam plate 14 and the cam plate. A motor 6 rotates the cam plate 14 through the torsion spring 20, even if the rotation of the cam plate 14 is obstructed, deforms the torsion spring 20 to continue the rotation, and attains a prescribed amount of the rotation. When the claws 28 attached to the fingers 22 clamp the work for the positioning, the cam plate 14 stops, however, the motor 6 rotates by a predetermined amount and applies a predetermined pushing pressure to the work without stepping out. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for positioning a workpiece such as a semiconductor chip in a correct posture at a set position. This device is a kind of chuck mechanism, and the invention disclosed herein can also be used as a chuck for gripping a workpiece for conveyance or the like by increasing power or strengthening the structure.
[0002]
[Prior art]
For example, in an assembly machine in a semiconductor manufacturing process, a semiconductor chip as a part is attached to a tape and used. In a taping machine that makes such a component placement tape, a semiconductor chip is placed in a correct position and posture with respect to the tape in advance using a workpiece positioning device (alignment unit). Alternatively, in a semiconductor chip inspection machine, it is necessary to always place the semiconductor in the correct position, and therefore, before the actual inspection stage, the semiconductor chip is placed in the correct position and posture using the workpiece positioning device.
[0003]
In this case, the workpiece is attracted to the suction cup or the like of the transfer device at a substantially correct position and posture and is carried to the workpiece positioning device, where it is positioned more accurately. At this time, in order to move the workpiece, that is, to correct the position and orientation, it is necessary to overcome the force attracting the workpiece and move it. For positioning, there are many mechanisms for positioning by moving the claws arranged opposite to each other in a colliding direction and pinching the workpiece. In this case, the claw is attached to the finger, and the movement of the claw is to move the finger, but as the mechanism, displacement by an air pressure or actuator using a solenoid as a power source or a cam using a motor as a power source is used. Has been.
[0004]
Actuators that move the fingers directly by air pressure or solenoid actuators are difficult to reduce the shock at the start and stop because of the simple operation. For the movement of the fingers, a cam plate with cam grooves is used for the motor. Many mechanisms are used to drive. With this mechanism, if the amount of rotation of the cam plate by the motor is normally constant and the size of the workpiece to be handled changes, the size of the nail that sandwiches the workpiece and the initial interval of the nail are changed so that excessive force is not applied to the workpiece. I have to.
[0005]
However, even for the same type of work, there is a work that is larger than the set dimension between the claws due to dimensional errors and burrs attached during the manufacturing process. May end up. Further, if the positioning device is precise, the positioning function itself may be out of order.
In order to prevent this situation, there is a buffer mechanism in which a compression spring or a tension spring is attached between a claw that sandwiches a workpiece and a finger (for example, see Patent Documents 1 to 4).
[0006]
Among these, the positioning devices disclosed in Patent Documents 1 to 3 utilize the elasticity by adding a tension spring, a compression spring, or a so-called spring as a buffer mechanism to each claw. However, if each claw is provided with a buffer function by a spring, accurate positioning cannot be performed without damaging the workpiece. That is, even if the fingers are simultaneously moved opposite to each other by the cam, the claw that has reached the workpiece first may escape by itself due to the influence of the force attracting the workpiece. In addition, the arrangement of the compression springs and tension springs individually complicates the apparatus, and the work of changing the springs to change the spring strength (to adjust the pressing force on the workpiece) also takes time.
[0007]
On the other hand, the gripping device of Patent Document 4 is fixed to the output shaft 2 to drive the second rotating member 5 (cam plate) that moves the gripping portion 7 (claw) to face the ultrasonic motor 1. A compression spring (biasing means) is disposed between the first rotating member 3 and the second rotating member 5 via a metal ball, and the power of the first rotating member 3 is supplied to the second rotating member via the compression spring. A structure for transmitting to the rotating member 5 is disclosed.
In this structure, the compression spring exhibits a buffer function, and there is no single buffer mechanism for each of the gripping portions 7 that move oppositely. Therefore, if one gripping part comes into contact with the workpiece first and further movement becomes impossible, this means that the second rotating member 5 that is a cam plate stops, and the movement of the other gripping part also stops. The work is not pinched and the work is not damaged by excessive pressure.
[0008]
In addition, since the elasticity of the compression spring should naturally be stronger than the suction force of the suction cup that conveys the workpiece, in the normal case, the gripping part 7 that reaches the workpiece first pushes the workpiece and moves it, It can be positioned by being sandwiched between the opposed gripping portions 7.
Further, during the positioning, the compression spring always presses the gripping portion 7 toward the workpiece, so that it is considered that a gap is hardly generated between the workpiece and the gripping portion in the positioned state.
[0009]
However, the structure disclosed in Patent Document 4 employs a compression spring for the biasing means 13 disposed as a buffer mechanism between the first and second rotating members 3 and 5, and therefore has the following drawbacks. is there.
Since the compression spring basically expands and contracts in the linear direction, it is difficult to obtain a sufficient buffer effect if it is arranged in a limited space. In the thing of patent document 4, it is thought that it is only about 10 degrees-20 degrees in the rotation angle of the 1st rotation member 3. FIG. Further, the compression spring is preferably arranged with its axis line aligned with the tangential direction in which the first rotating member 3 rotates, but in this case as well, it is often difficult to achieve a satisfactory arrangement in a limited space. .
[0010]
In the thing of patent document 4, since the compression spring is directly provided in the 2nd rotation member 5, a special process is required for the 2nd rotation member, and also it compresses by the press of the 1st rotation member 3. In order to smoothly expand and contract the spring, it is considered that a fine mechanism for smoothly transmitting the pressing force to the spring side, such as using a metal ball between the first rotating member 3 and the compression spring, is necessary, which increases costs. become. In order to arrange the compression spring without processing the second rotating member, it is necessary to use a plurality of parts. In any case, when a compression spring is arranged on the second rotating member, this does not obstruct the four-direction positioning structure in which claws facing each of the X direction and the Y direction are arranged.
After all, the positioning device of Patent Document 4 cannot be said to have a versatile structure.
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 1-133327 (FIG. 2)
[Patent Document 2]
JP-A-60-172438 (FIG. 1)
[Patent Document 3]
Japanese Examined Patent Publication No. 61-42420 (Fig. 3)
[Patent Document 4]
Japanese Patent Laid-Open No. 09-109081
[Problems to be solved by the invention]
According to the present invention, a buffer effect (an effect of absorbing the influence of the subsequent rotation of the motor) when the claw of the positioning device pinches the workpiece is simultaneously given to a plurality of claws at the same level with a simple configuration, and accurate positioning can be performed. Another object of the present invention is to provide a device having a large adjustment range and less impact on operation. This device is also intended to be used as a chuck.
[0013]
[Means for Solving the Problems]
A motor and a motor head for driving the cam plate and the cam follower, the fingers and the claws, and the cam plate are arranged on the body.
The cam plate is usually a disc cam having a plurality of cam grooves, but the form is not limited to a disc. A cam follower is guided in each cam groove, and a finger is fixed to each cam follower. The fingers are guided linearly toward one point in the fuselage. Linear guides are often used as parts for linear guidance. Claws are attached to the fingers so that they can be replaced.
[0014]
The cam groove is shaped to move the cam follower in the radial direction of rotation by the rotation of the cam plate. For example, the cam plate has a shape that appears radially as a whole extending radially from the vicinity of the rotation center of the cam plate toward the periphery of the rotation trajectory of the cam plate, and the plurality of cam grooves are curved in the same direction. The actual cam groove has a so-called cam curve area at the initial stage and period of claw movement, and the middle part is a constant pitch feed area. By adjusting the number of pulses in the pitch feed area, it is possible to easily determine the amount of rotation of the motor according to the length of the cam groove.
[0015]
A torsion spring is disposed between the cam plate and the motor head of the motor that drives the cam plate. A torsion spring is a spring in which a spring material is spirally wound and a load is applied to one end of the spring material in the winding direction (tangential direction of the winding). The cam plate and the motor head are usually arranged with their centers aligned with the axis of the output shaft of the motor, and the torsion spring is also arranged coaxially with the axis of the output shaft. A torsion spring is disposed between the cam plate and the motor head, and a first pin that protrudes downward from the cam plate is engaged with one end of the torsion spring and is protruded upward from the motor head. A pin is engaged with the other end of the torsion spring.
[0016]
In these engagement modes, when the torsion spring is pressed from the motor head side, the engagement state between the pin and the torsion spring is maintained at one end and the other end, but the motor head is driven and rotated in the opposite direction. Is disengaged on the motor head side, and the pin side is engaged with the spring on the cam plate side. That is, only when the motor drives and rotates the cam plate in the direction to close the fingers, a torsion spring is interposed between the cam plate and the motor to transmit power.
[0017]
In the return rotation of the cam plate, the pin of the motor head driven and rotated in the opposite direction is engaged with the engagement surface formed on the lower surface of the cam plate, and the cam plate is directly rotated back to the original position.
Thus, the structure which arrange | positions the spring as a buffer mechanism between a motor head and a cam board does not require a special process to a cam board and a motor head.
[0018]
The motor can detect the position of the finger or the like by a non-contact type position sensor and stop the rotation in the forward or reverse direction, or an expensive servo motor can be used, but a step motor is preferably used. . When using a stepping motor, if the movement of the finger is inhibited while leaving a pulse amount, the rotation becomes difficult and causes a step-out. However, in this positioning device, even if the rotation of the cam plate is prevented, the stepping Since the motor can continue to rotate until the torsion spring is deformed to a predetermined pulse amount, the motor does not cause step-out immediately. Rather, after the workpiece is positioned, the step motor is further rotated, so that reliable positioning utilizing the elasticity of the torsion spring can be performed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the positioning device 1 (FIG. 1), a base body 2, a main body block 3, and a finger cover block 4 constitute an airframe 5, to which a stepping motor 6 is attached. The base block 2 has a cylindrical shape with a flange 7. A stepping motor 6 is attached to the lower portion of the base block 2, and an output shaft 8 projects inside. A motor head 9 is attached to the output shaft 8 and is rotatably supported in the base block 2 by a bearing 10. A first pin 11 is fixed upward at the periphery of the motor head 9 (FIG. 2D), and a cylindrical wall 12 is formed at the center. Reference numeral 13 denotes a screw hole for mounting a screw for fixing the motor head 9 to the output shaft 8.
[0020]
The main body block 3 has a shallow cylindrical shape, and a disc-shaped cam plate 14 is disposed in the center of the axis P of the output shaft 8 of the stepping motor 6 and is supported by bearings 15 and 16 so as to be rotatable. . The upper bearing 15 is disposed between the main body block 3 and the cam plate 14, and the lower bearing 16 is disposed between the cylindrical wall 12 of the motor head 9 and the cam plate 14.
[0021]
The cam plate 14 (FIG. 2A) has a second pin 17 projecting downward at the peripheral edge thereof, and a radial vertical surface at a position approximately 180 ° apart to form an engagement surface. It is as 18. The cam plate 14 has four cam grooves 19 at equal intervals in the circumferential direction (FIG. 3). The shape of the cam groove 19 is substantially arc-shaped. Specifically, both end portions are cam curve regions and the intermediate portion is a constant pitch region, and these are smoothly connected. These cam grooves 19 are formed radially such that one end is close to the rotation center of the cam plate 14 and the other end is close to the periphery, and the direction of the arc is aligned.
[0022]
The cam plate 14 is assembled so as to be stacked on top of the motor head 9 (FIG. 1). At that time, a torsion spring 20 (FIG. 2B, C) is fitted on the outer peripheral side of the cylindrical wall 12 above the motor head 9 to be twisted. Both ends of the spring 20 are engaged with the first pin 11 and the second pin 17. The direction of engagement is such that when the first pin 11 pushes the engagement portion with the torsion spring 20, the second pin 17 is pushed by the engagement portion of the torsion spring 20.
[0023]
A finger cover block 4 is attached above the main body block 3. The finger cover block 4 has a shallow cylindrical shape, and the linear guide 21 and the finger 22 are paired inside to oppose each other, and the moving directions of each set are orthogonal to each other as the X direction and the Y direction. (FIG. 4). The intersection of the orthogonal axes is above the axis P. 4 and 5, the finger 22 is arranged in a form attached to the rail 23 of the linear guide 21, the upper surface is a claw mounting portion 24, and the cam follower 25 is mounted on the lower portion (FIG. 5).
[0024]
The cam follower 25 is a roller having a diameter corresponding to the width of the cam groove 19 and is attached to the finger 22 so as to be rotatable by a longitudinal shaft pin 26. The fingers 22 are located inside the finger cover block 4, but the linear guides 21 are fixed to the main body block 3, and are arranged so that the moving directions are orthogonal to each other in the X and Y directions. Yes. At the same time, the lower cam follower 25 is fitted and guided in the cam groove 19 of the cam plate 14.
[0025]
The claw mounting portion 24 protrudes slightly upward from four windows (FIG. 6) provided on the cover plate 27 that covers the upper surface of the finger cover block 4. In each window, a margin S for the stroke of the finger 22 is formed in the radial direction. The figure shows an open end position, and reference numeral 28 denotes a claw, which is an example.
[0026]
In the above configuration, when the stepping motor 6 is driven with a predetermined pulse amount from the state where the pawl 28 is open (open end), the motor head 9 is driven to rotate, and the first pin 11 is shown in FIG. Rotate right in 2C. The first pin 11 is sandwiched between one end of the torsion spring 20 and the engagement surface 18 (FIG. 2A) on the lower surface of the cam plate 14 and engages with one end of the torsion spring 20. The cam plate 14 is rotated via the pin 17. At this time, since the force is transmitted directly from the first pin 11 to the torsion spring 20 in the tangential direction, the transmission is smooth and smooth, and a special member is required for smooth transmission. do not do.
[0027]
As the cam plate 14 rotates, the cam followers 25 of the cam grooves 19 move in the center direction, the fingers 22 move linearly in the radial direction via the linear guides 21, and the workpiece is sandwiched between the opposing claws 28. Position. In this embodiment, the claw 28 moves from the four directions to the center at the same time to pinch the workpiece. The stepping motor 6 rotates for a while so that the torsion spring 20 is tightened even after the claw 28 comes into contact with the workpiece and the cam plate 14 cannot rotate. During that time, the reaction force presses the workpiece with the torsion spring 20. Continue. Therefore, no gap remains between the workpiece and the claw 28. The torsion spring 20 can be tightened by 50 ° to 90 ° according to the rotation angle of the motor head 9 and has a sufficient margin.
[0028]
Then, the stepping motor consumes a predetermined amount of pulse and stops (closed end), and the claw 28 is kept closed.
The force for sandwiching the workpiece is within the range of elasticity of the torsion spring 20 and is almost constant. Further, when the workpiece accurately corresponds to the set claw interval, the pressing force on each side of the workpiece is substantially constant.
[0029]
A pair of pawls 28 that move in opposition to each other because the burrs are attached to one side of the workpiece or the dimension in that direction is larger than the setting. 14 rotation may be prevented. In this case as well, the stepping motor 6 continues to rotate by the remaining amount pulse after the cam plate 14 stops rotating. However, the rotation for the remaining amount pulse acts to tighten the torsion spring 20 and is excessive for the workpiece. Prevent force from acting. Then, the elastic force accumulated in the torsion spring 20 helps to position the workpiece reliably as a pressing force.
[0030]
At this time, if the set of claws sandwiching the workpiece is in the X-axis direction, the cam plate 14 is prevented from rotating by the X-axis direction claws 28 coming into contact with the workpiece. In some cases, a gap may be formed while 28 cannot contact the workpiece. However, positioning is accurately performed at least in the X-axis direction. When this situation is inconvenient, it is possible to take a means for generating an alarm when no pressing force is detected in the Y-axis direction.
[0031]
That is, since there is only one torsion spring 20, its elasticity acts simultaneously on the plurality of claws 28 through the cam plate 14 to the same extent, and any side of the workpiece having a dimensional abnormality can be handled in the same manner as described above. be able to. Further, as described above, since the rotation of the cam plate 14 is stopped, other claws 28 including the claw 28 that has been in contact with the cam plate 14 stay in place, and the workpiece is not damaged.
[0032]
When the positioning is completed, the stepping motor 6 rotates in the reverse direction by the same pulse amount as described above according to the external signal. However, even if the first pin 11 of the motor head 9 starts to reversely rotate, the cam plate 14 does not rotate due to the elastic force of the torsion spring 20 with the first pin 11 as a base point. 28 does not open. The torsion spring 20 continues to press the workpiece with its elasticity until the first pin 11 of the motor head 9 comes into contact with the engagement surface 18 on the lower surface of the cam plate 14. Next, when the first pin 11 comes into contact with the engagement surface 18, the cam plate 14 is forcibly rotated in the reverse direction as the motor head 9 rotates. With the reverse rotation of the cam plate 14, the cam follower 25 of each cam groove 19 moves away from the center of rotation, and the pawl 28 opens. Then, it is forcibly moved in the opening direction as it is, and stops at the original opening end position.
[0033]
Although the above description has been given of the case where the four fingers 22 are provided, there may be only two fingers 22 facing each other. Although a stepping motor is preferable as a power source, other types of motors and actuators can be used by providing an appropriate rotation stop mechanism.
[0034]
【The invention's effect】
Since it is a mechanism in which a plurality of claws escape to the same extent at the same time, the workpiece can be accurately positioned.
The buffer mechanism has a simple configuration using one torsion spring, and the product does not increase in size. Moreover, it can be achieved simply by fitting the torsion spring into the rotating shaft of the cam plate, and since it is not a special structure, it is highly versatile.
[0035]
When adjusting the pressing force for sandwiching the workpiece, it is possible to rearrange one torsion spring, and the adjustment work is simple.
When the positioning operation (the cam plate closing operation) starts, the cam curve starts up shocklessly, and the impact applied to the fingers can be suppressed, so that the mechanical durability of the positioning device can be increased.
[0036]
After a smooth start by the cam curve, the cam follower can be placed in the constant pitch feed region of the cam groove, so the pulse amount is adjusted in a period where the finger movement amount corresponding to one pulse rotation of the stepping motor is constant. Thus, it is possible to easily set the pulse amount necessary for positioning the target workpiece.
If a stepping motor is used, the spring load after the work is sandwiched by adjusting the pulse feed amount can be adjusted. For this reason, it is possible to make adjustments such as sandwiching a small workpiece with a small force and a large workpiece with a large force.
[0037]
Since the stepping motor can be used without being stepped out, the product cost can be reduced as compared with an apparatus using an expensive servo motor.
[Brief description of the drawings]
FIG. 1 is a front view for explaining a mechanism.
2A is a cross-sectional view of a cam plate, FIG. 2B is a front view of a torsion spring, C is a plan view of a torsion spring portion, and 2 is a cross-sectional view of a motor head.
FIG. 3 is a plan view of a cam plate portion.
FIG. 4 is a plan view with the cover plate removed.
FIG. 5 is a front view of the fingers and the linear guide when viewed from the direction of movement of the fingers.
FIG. 6 is a plan view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positioning device 2 Base block 3 Main body block 4 Finger cover block 5 Airframe 6 Stepping motor 7 Flange 8 Output shaft 9 Motor head 10 Bearing 11 First pin 12 Cylindrical wall 13 Screw hole 14 Cam plate 15 Bearing 16 Bearing 17 Second Pin 18 engagement surface 19 cam groove 20 torsion spring 21 linear guide 22 finger 23 rail 24 claw mounting portion 25 cam follower 26 shaft pin 27 cover plate 28 claw

Claims (3)

The airframe is provided with a cam plate having a plurality of cam grooves, a cam follower guided in each cam groove, and a finger that moves integrally with each cam follower. The cam groove rotates the cam follower in the radial direction of rotation. This is a moving shape, and power is transmitted between the cam plate and the motor only when the cam plate is driven and rotated in the direction to close the fingers between the cam plate and the motor head of the motor that drives the cam plate. A workpiece positioning device in which a torsion spring is inserted into a rotating shaft of a cam plate. The center of rotation of the cam plate and the motor head is arranged on the same axis, and a torsion spring is placed between the first pin protruding from the lower surface of the cam plate and the second pin protruding from the upper surface of the motor head, and one end is The other end of the pin is engaged with the second pin and coaxial with the axis, and the motor head is engaged with the second pin when the motor head is rotated in the opening direction on the lower surface of the cam plate. The workpiece positioning apparatus according to claim 1, further comprising an engagement surface. The motor is a stepping motor, and the pulse feed amount to the stepping motor is set slightly larger than the amount required for the finger to move from the open end to the closed end by forward and reverse rotation. The workpiece positioning apparatus according to claim 1 or 2.

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