Work holding device

Abstract

To have a high degree of freedom of a conveyance attitude, suppress reduction in a conveyance speed and charge workpiece to a narrow workpiece charging port when thin plate-like workpiece is conveyed.SOLUTION: A workpiece holding device 6 includes: a base 2; a holding mechanism 3 for holding the workpiece W on its rear end side; a movement mechanism 4 for moving the holding mechanism 3 in a forward / backward direction of the base 2; and at least one adsorption pads 51 and 52 that are provided on the front end of the base 2 and adsorb the workpiece W held by the holding mechanism 3 on its front end side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a robot hand, a workpiece holding device, and a transport device. [Background technology]

[0002] In manufacturing lines, robot devices are widely used as devices for transporting workpieces. Robot devices are equipped with hands according to the workpieces to be transported. For example, as a hand for transporting a plate-shaped workpiece, a hand that transports the plate-shaped workpiece by placing it on two finger-like parts is known (for example, Patent Document 1). However, since the hand disclosed in Patent Document 1 places the workpiece on the finger-like parts, it cannot be used when the workpiece insertion opening is narrow and the finger-like parts cannot be inserted. On the other hand, when a hand that grasps the base end of a plate-shaped workpiece and transports it is used, since the workpiece is held at one end, the tip of the workpiece is deflected due to air resistance or its own weight, and a problem occurs in that the insertion position into the narrow workpiece insertion opening cannot be determined. Therefore, in order to suppress the deflection of the tip of the workpiece due to air resistance or its own weight, the transport speed and transport posture of the workpiece are inevitably limited. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-168719 A Summary of the Invention [Problem to be solved by the invention]

[0004] In particular, when transporting thin, plate-like workpieces, it is desirable to have a high degree of freedom in the transport posture, to suppress any decrease in transport speed, and to be able to feed the workpieces into a narrow work feed opening. [Means for solving the problem]

[0005] A work holding device according to one aspect of the present disclosure comprises a base plate, a gripping mechanism for gripping a workpiece at its rear end, a moving mechanism for moving the gripping mechanism along the fore-and-aft direction of the base plate, and at least one suction pad provided at the front end of the base plate for adsorbing the gripped workpiece at its front end. Effect of the Invention

[0006] There is a high degree of freedom in the conveying posture, the decrease in conveying speed is suppressed, and workpieces can be inserted into a narrow workpiece insertion opening. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a side view showing a robot device equipped with a workpiece holding device according to this embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of the robot hand of FIG. [Diagram 3] FIG. 3 is a plan view of the robot hand of FIG. [Figure 4] FIG. 4 is a side view of the robot hand of FIG. [Diagram 5] FIG. 5 is a side view showing an example of a procedure for gripping a workpiece by the robot hand in the reference posture. [Figure 6] FIG. 6 is a side view showing another example of the procedure for gripping a workpiece by the robot hand in the inverted posture. [Figure 7] FIG. 7 is a side view showing the air exhaust operation by the suction pad. [Figure 8] FIG. 8 is a perspective view showing the robot hand together with the rack immediately before the operation of storing the workpiece. [Figure 9] FIG. 9 is a side view showing the robot hand together with the rack immediately before the operation of storing the workpiece. [Figure 10] FIG. 10 is a side view showing the robot hand together with the rack during the operation of storing the workpiece. [Figure 11] FIG. 11 is a side view showing a robot device equipped with a workpiece holding device according to a modified example of this embodiment. [Figure 12] FIG. 12 is a perspective view showing an example of the robot hand of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the workpiece holding device according to the present embodiment will be described with reference to the drawings. In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals, and repeated description will be given only when necessary.

[0009] As shown in Fig. 1, the work holding device 6 according to this embodiment is a device suitable for picking up a thin rectangular plate-shaped workpiece W. The work holding device 6 has a robot hand 1 attached to a moving device such as a robot arm mechanism 7, a pressurizing / depressurizing device 8 for pressurizing and depressurizing the inside of the suction pad of the robot hand 1, and a hand control device for controlling the operation of the robot hand 1. In this embodiment, the robot control device 9 that controls the robot arm mechanism 7 will be described as having the function of a hand control device. Note that the hand control device may be separate from the robot control device 9.

[0010] The robot control device 9 includes a storage device such as an HDD that stores a task program describing a series of operations to be performed by the robot arm mechanism 7 and the robot hand 1, and a calculation processing device such as a CPU that executes the program stored in the storage device. By executing the task program by the calculation processing device, the robot arm mechanism 7 and the robot hand 1 operate according to a sequence defined by the task program, and can pick up a workpiece W transported to a predetermined position by the belt conveyor 100, transport it from the belt conveyor 100 to the rack 200, and release it to the predetermined position on the rack 200.

[0011] 2, the robot hand 1 has a base 2, a gripping mechanism 3 that grips a workpiece W at its rear end, a moving mechanism 4 that moves the gripping mechanism 3 along the front-rear direction of the base 2, and an adsorption unit 5 that adsorbs the workpiece W gripped by the gripping mechanism 3 at its front end. In this embodiment, since the workpiece W is a rectangular plate, the gripping mechanism 3 is configured to be able to grip the workpiece W at two points as close as possible to each of the two corners on the rear end side, and the adsorption unit 5 is configured to be able to adsorb the workpiece W at two points as close as possible to each of the two corners on the front end side.

[0012] Typically, the base 2 has a rectangular base plate 21 that is longer than the workpiece W and has the same width as the workpiece W, and a rectangular connection plate 23 that is connected perpendicularly to the rear end of the base plate 21. An adapter 25 is attached to the outer surface of the connection plate 23. The robot hand 1 is attached to the hand attachment portion 71 of the robot arm mechanism 7 via the adapter 25. The three orthogonal axes used in the description of this embodiment are defined as follows. That is, the axis perpendicular to the outer surface of the connection plate 23 is defined as the X-axis, the axis perpendicular to the inner surface of the base plate 21 is defined as the Z-axis, and the axis perpendicular to the X-axis and Z-axis is defined as the Y-axis. The X-axis direction corresponds to the front-rear direction (length direction) of the robot hand 1, the Z-axis direction corresponds to the up-down direction (thickness direction) of the robot hand 1, and the Y-axis direction corresponds to the left-right direction (width direction) of the robot hand 1. In addition, a straight line that passes through the center of the width of the base plate 21 and is parallel to the X-axis is defined as the base center line.

[0013] The moving mechanism 4 is composed of a support mechanism that supports the gripping mechanism 3 movably along the front-rear direction of the base plate 21, and a drive unit (not shown) that drives the movement of the gripping mechanism 3. The support mechanism is composed of a rail 41 that is installed on the base plate 21 parallel to the front-rear direction, and a rectangular plate-shaped slider block 43 that is movably engaged with the rail 41. The drive unit is composed of, for example, a ball screw mechanism consisting of a ball screw and a nut, and a servo motor for rotating the ball screw. The gripping mechanism 3 is installed on the slider block 43, and the nut is connected to the slider block 43, and the gripping mechanism 3 moves along the front-rear direction of the base plate 21 as the ball screw rotates. The ball screw mechanism may also serve as the support mechanism.

[0014] The gripping mechanism 3 has a pair of chuck mechanisms 31, 32 and a chuck drive mechanism (not shown) that drives the pair of chuck mechanisms 31, 32 to open and close. The pair of chuck mechanisms 31, 32 are fixed to a slider block 43 so as to be disposed at positions equidistant from the base center line on both the left and right sides of the base center line. One chuck mechanism 31 has a pair of fingers 311, 312 that can move toward and away from each other, and is attached to the slider block 43 so that the opening and closing direction of the fingers 311, 312 is parallel to the vertical direction and the tips of the fingers 311, 312 face forward. Similarly, the other chuck mechanism 32 has a pair of fingers 321, 322 that can move toward and away from each other, and is attached to the slider block 43 so that the opening and closing direction of the pair of fingers 321, 322 is parallel to the vertical direction and the tips of the fingers 321, 322 face forward.

[0015] The suction unit 5 has a pair of suction pads 51, 52. The pair of suction pads 51, 52 are arranged at the front end of the base plate 21. The suction pads 51, 52 each have a cone-shaped suction cup 51a, 52a made of elastic resin. The suction cups 51a, 52a are connected to cylindrical bodies 51b, 52b, respectively, and are typically molded as one piece. A hole is formed at the bottom of the suction cup 51a, 52a, and the inside of the suction cup 51a, 52a is connected to the inside of the cylindrical body 51b, 52b. The cylindrical body 51b, 52b is made of elastic resin like the suction cups 51a, 52a, and deforms appropriately when the suction cups 51a, 52a suction the workpiece W, absorbing excessive pressure applied to the workpiece W.

[0016] Poles 53 and 54 are erected on both sides of the front end of the base plate 21. Suction pads 51 and 52 are installed on the tips of the poles 53 and 54, respectively. The lengths of the poles 53 and 54 are set so that the height of the contact surface of the suction pads 51 and 52 coincides with the height of the opening and closing center of the fingers 311 and 312 (321 and 322) with respect to the base plate 21. As a result, when the rear end side of the workpiece W is gripped by the gripping mechanism 3 and the front end side of the workpiece W is sucked by the suction pads 51 and 52, the workpiece W can be maintained in a flat state, and deformation of the workpiece W and creases in the workpiece W can be prevented. The XY plane that coincides with the contact surfaces of the pair of suction pads 51 and 52 is defined as the workpiece holding surface of the robot hand 1.

[0017] The poles 53 and 54 are formed with piping that penetrates vertically. The tips of the piping of the poles 53 and 54 are connected to the cylindrical bodies 51b and 52b, respectively. The piping of the poles 53 and 54 passes through the base plate 21 and their rear ends protrude slightly from the lower surface of the base plate 21, and an air tube extending from the pressurizing and depressurizing device 8 is connected to the rear end of the piping of the base plate 21. An air flow path is formed from the pressurizing and depressurizing device 8 to the suction pads 51 and 52 by the air tube and the piping of the poles 53 and 54.

[0018] The pressurizing / depressurizing device 8 comprises a pump, an air tube connecting the pump to the suction unit 5, and a solenoid valve that switches between the suction port and exhaust port of the pump to the air tube. The solenoid valve is driven and controlled to switch between suction and supply of air to the suction pads 51, 52. When the suction port of the pump is connected to the air tube, the inside of the suction pads 51, 52 is depressurized, and the suction pads 51, 52 adsorb the workpiece W. When the exhaust port of the pump is connected to the air tube, the inside of the suction pads 51, 52 is pressurized, and the suction pads 51, 52 do not adsorb the workpiece W. When air is supplied to the suction pads 51, 52, the workpiece W floats slightly and can move smoothly. When air is not supplied (air is supplied) to the suction pads 51, 52 and no suction (reduced pressure) is applied, the inside of the suction pads 51, 52 is equivalent to atmospheric pressure. However, even in this state, it is preferable that the suction pads 51, 52 be made of a self-lubricating resin so that the workpiece W can move smoothly while sliding on the suction pads 51, 52.

[0019] Note that the piping configuration is not limited to this embodiment as long as the inside of the suction pads 51, 52 can be put into a pressurized state, a depressurized state, or an atmospheric pressure state. In addition, in this embodiment, the workpiece holding device 6 is configured to have a single pressurizing / depressurizing device 8, but it may be configured to have two independent devices, such as a suction pump having a function of sucking in air, and a compressor having a function of discharging air.

[0020] The pick-up operation of a thin rectangular plate-shaped workpiece W using the workpiece holding device 6 according to this embodiment will be described. First, the pick-up operation of the workpiece W by the robot hand 1 in the reference posture will be described with reference to Fig. 5. Note that the reference posture refers to the posture in which the gripping mechanism 3 is placed on the rail 41 (the posture in which the inner surface of the base plate 21 faces upward).

[0021] 5(a), the robot arm mechanism 7 moves the robot hand 1 so that the height of the workpiece holding surface of the robot hand 1 matches the height of the center of the thickness of the workpiece W transported to a predetermined position by the belt conveyor 100. In the robot hand 1, the movement mechanism 4 moves the gripping mechanism 3 from a standby position on the rear end side of the base 2 to a gripping position on the front end side.

[0022] As shown in Fig. 5(b), the robot arm mechanism 7 moves the robot hand 1 forward. As a result, the workpiece W is inserted between the pair of fingers 311, 312 (321, 322). After that, the pair of fingers 311, 312 (321, 322) of the robot hand 1 are closed. As a result, the rear end side of the workpiece W is gripped by the pair of fingers 311, 312 (321, 322).

[0023] As shown in FIG. 5(c), the gripping mechanism 3 gripping the workpiece W at its rear end is moved by the moving mechanism 4 from a gripping position at the front end of the base 2 to a standby position at the rear end. During this time, the pressurizing and depressurizing device 8 is controlled so that the inside of the suction pads 51, 52 is pressurized. As a result, as shown in FIG. 7, air can be discharged from the suction pads 51, 52 toward the workpiece W, and the workpiece W can be slightly raised from the leading edges of the suction pads 51, 52, or even if the workpiece W comes into contact with the leading edges of the suction pads 51, 52, the frictional force generated between the leading edges of the suction pads 51, 52 and the workpiece W can be suppressed, and a situation in which the workpiece W moves while pressing the leading edges of the suction pads 51, 52 due to its own weight can be prevented. In any case, by discharging air from the suction pads 51, 52 toward the workpiece W, it is possible to prevent the leading edges of the suction pads 51, 52 from being rubbed and worn by the workpiece W, and to prevent the workpiece W from being scratched. After the gripping mechanism 3 gripping the workpiece W is moved to the standby position by the moving mechanism 4, the pressurizing / depressurizing device 8 is controlled so that the inside of the suction pads 51, 52 is changed from a pressurized state to a depressurized state. This enables the suction pads 51, 52 to suction the workpiece W at their front ends.

[0024] The gripping operation of the workpiece W by the robot hand 1 in the inverted posture will be described with reference to Fig. 6. Note that the inverted posture refers to a posture in which the robot hand 1 in the standard posture is rotated 180 degrees around the X-axis and the gripping mechanism 3 is suspended below the rail 41 (a posture in which the inner surface of the base plate 21 faces downward).

[0025] 6(a), the robot arm mechanism 7 moves the robot hand 1 so that the height of the workpiece holding surface of the robot hand 1 matches the height of the center of the thickness of the workpiece W transported to a predetermined position by the belt conveyor 100. In the robot hand 1, the movement mechanism 4 moves the gripping mechanism 3 from a standby position on the rear end side of the base 2 to a gripping position on the front end side.

[0026] As shown in Fig. 6(b), the robot arm mechanism 7 moves the robot hand 1 forward. As a result, the workpiece W is inserted between the pair of fingers 311, 312 (321, 322). After that, the pair of fingers 311, 312 (321, 322) of the robot hand 1 are closed. As a result, the rear end side of the workpiece W is gripped by the pair of fingers 311, 312 (321, 322).

[0027] As shown in FIG. 6(c), the robot arm mechanism 7 moves the robot hand 1 forward so that the position of the workpiece W on the belt conveyor does not change, and at the same time, the moving mechanism 4 moves the gripping mechanism 3 that grips the workpiece W from the gripping position on the front end side of the base 2 to the standby position on the rear end side. During this time, the pressurizing and depressurizing device 8 may be controlled so that the inside of the suction pads 51, 52 is pressurized. This allows air to be discharged from the suction pads 51, 52 toward the workpiece W, and the front end side of the workpiece W can be pressed against the placement surface of the belt conveyor 100, so that it is possible to prevent the front end side of the workpiece W from moving for some reason. In addition, dust attached to the suction portion of the workpiece W can be blown away by the air. These contribute to reducing the risk of the suction pads 51, 52 being damaged by the workpiece W contacting the suction pads 51, 52, and also contribute to improving the reliability of the suction operation of the suction pads 51, 52 to suction the workpiece W. After that, the pressurizing and depressurizing device 8 is controlled so that the inside of the suction pads 51, 52 is depressurized. This allows the suction pads 51 and 52 to suction the workpiece W at its front end side.

[0028] The standby position of the gripping mechanism 3 is determined so that when the gripping mechanism 3 gripping the workpiece W is moved to the standby position, the front end of the workpiece W protrudes slightly forward from the front end of the base 2. As a result, in the operation of storing the workpiece W in the rack 200 described later, the front end portion of the workpiece W protruding from the front end of the base 2 can be inserted into the workpiece insertion port of the rack 200 in a state in which the suction pads 51 and 52 are adsorbing the workpiece W. This contributes to improving the reliability of the operation of storing the workpiece W. In addition, the gripping position of the gripping mechanism 3 is determined so that when the gripping mechanism 3 is moved to the gripping position, the tips of the pair of fingers 311, 312 (321, 322) protrude forward from the front end of the base 2. As a result, the risk of the base 2 colliding with surrounding devices and members such as the belt conveyor 100 during the operation of moving the pair of fingers 311, 312 (321, 322) closer to the workpiece W can be reduced.

[0029] Next, referring to Figs. 8 to 10, the operation of storing the workpiece W in the rack 200 by the workpiece holding device 6 according to this embodiment will be described. As shown in Figs. 8 and 9, the robot arm mechanism 7 moves the robot hand 1, and the front end portion of the workpiece W held by the robot hand 1 is inserted into the workpiece insertion port. Thereafter, the pressurizing and depressurizing device 8 is controlled so that the inside of the suction pads 51, 52 transitions from a reduced pressure state to an atmospheric pressure state. As a result, the front end side of the workpiece W becomes free. Next, as shown in Fig. 10, the moving mechanism 4 moves the gripping mechanism 3 from a standby position on the rear end side of the base 2 to a front end position. During this time, the pressurizing and depressurizing device 8 is controlled so that the inside of the suction pads 51, 52 transitions from an atmospheric pressure state to a pressurized state. 7, air can be discharged from the suction pads 51, 52 toward the workpiece W, suppressing frictional force generated between the leading edges of the suction pads 51, 52 and the workpiece W, suppressing wear on the leading edges of the suction pads 51, 52 caused by the workpiece W moving while contacting the leading edges of the suction pads 51, 52 due to its own weight, and preventing the workpiece W from being scratched by contacting the leading edges of the suction pads 51, 52. Thereafter, the pair of fingers 311, 312 (321, 322) of the gripping mechanism 3 is opened, and the workpiece W is accommodated in the rack 200.

[0030] According to the workpiece holding device 6 according to the present embodiment described above, the gripping mechanism 3 can grip the workpiece W at two points near both left and right edges on the rear end side, and the suction pads 51, 52 can also suction the workpiece W at two points near both left and right edges on the front end side. As a result, the workpiece holding device 6 can hold the four corners of the rectangular plate-shaped workpiece W. This makes it possible to avoid a situation in which the workpiece W is bent due to its own weight or the workpiece W is bent due to air resistance during transportation, and a decrease in the transportation speed can be suppressed. In addition, since the workpiece W can be temporarily fixed to the base 2 by the workpiece holding device 6, the degree of freedom of the posture of the robot hand 1 during transportation and storage can be increased. As a result, when picking up the workpiece W from the belt conveyor 100, not only can the posture of the robot hand 1 be selected from the standard posture and the inverted posture according to the surrounding environment, but also the orientation of the workpiece input port of the rack 200 can be flexibly accommodated, such as when the orientation of the workpiece input port is upward or slightly inclined from the upward orientation. In addition, the decrease in the transport speed can be suppressed, and the posture of the robot hand 1 during transport is free, so that the overall task time can be shortened.

[0031] 10, the operation of storing the workpiece W in the rack 200 by the work holding device 6 can be performed by simply moving the moving mechanism 4 of the robot hand 1 forward after the robot arm mechanism 7 has moved the robot hand 1 to the outside of the workpiece insertion opening. Since there is no need to insert the robot hand 1 into the rack 200 from the workpiece insertion opening, even if the workpiece insertion opening of the rack 200 is narrow and has a height approximately equal to the thickness of the workpiece W, the workpiece W can be stored in the rack 200 using the work holding device 6.

[0032] In this embodiment, since the workpiece W is a rectangular thin plate, the pair of suction pads 51, 52 and the pair of chuck mechanisms 31, 32 are provided to hold the four corners of the workpiece W. However, the number of suction pads and the number of chuck mechanisms can be changed as desired depending on the shape, size, weight, etc. of the workpiece W. In addition, multiple chuck mechanisms may be provided on the slider block 43, shifted not only in the left-right direction but also in the front-back direction. In addition, multiple suction pads may be provided at positions shifted not only in the left-right direction but also in the front-back direction. In addition, instead of a configuration in which the pair of chuck mechanisms 31, 32 are moved by a single moving mechanism 4, each chuck mechanism may be configured to move independently. In addition, a single chuck mechanism may be configured to have two pairs of fingers that can be opened and closed.

[0033] As long as the workpiece W can be attracted, the attraction structure is not limited to that of this embodiment. For example, if the workpiece W is made of a magnetic material, an electromagnet capable of attracting the workpiece W by magnetic force can be used. Hereinafter, a workpiece holding device 60 according to a modified example in which the suction pads 51, 52 in the workpiece holding device 6 according to this embodiment are replaced with electromagnets 55, 56 will be described. As shown in FIG. 11, the workpiece holding device 60 according to the modified example has an electromagnet driving unit 80. The electromagnet driving unit 80 supplies current to the electromagnets 55, 56 and stops the current supply according to the control of the robot control device 90.

[0034] 12, the pair of electromagnets 55, 56 are provided at the same positions as the pair of suction pads 51, 52 in this embodiment. That is, poles 57, 58 are provided upright on both sides of the front end of the base plate 21. The pair of electromagnets 55, 56 are installed at the tips of the poles 57, 58, respectively. Pads may be attached to the tips of the electromagnets 55, 56 to prevent the workpiece W from being scratched by the electromagnets 55, 56. The length of the poles 57, 58 is set so as to match the height of the contact surface of the electromagnets 55, 56 or the height of the contact surface of the pads provided at the tips of the electromagnets 55, 56 with respect to the base plate 21, which is the height of the opening and closing centers of the fingers 311, 312 (321, 322).

[0035] For example, the pick-up operation of the workpiece W by the workpiece holding device 60 according to the modified example can be described with reference to FIG. 5(c). After the gripping mechanism 3 that grips the workpiece W is moved by the moving mechanism 4 from a gripping position on the front end side of the base 2 to a standby position on the rear end side, the electromagnets 55, 56 are magnetized by the electromagnet driving unit 80. This allows the electromagnets 55, 56 to attract and adsorb the workpiece W. The storage operation of the workpiece W by the workpiece holding device 60 according to the modified example can be described with reference to FIG. 10. After the gripping mechanism 3 is moved by the moving mechanism 4 from a standby position on the rear end side of the base 2 to a front end position, the electromagnets 55, 56 are demagnetized by the electromagnet driving unit 80, and the workpiece W is stored in the rack 200.

[0036] In this way, according to the work holding device 60 of the modified example that employs electromagnets 55, 56 as the suction portion 5, the work holding device 6 can perform pick-up operations, transport operations, and storage operations for the work W in the same manner as the work holding device 6 of the present embodiment that employs suction pads 51, 52 as the suction portion 5, and can achieve the same effects.

[0037] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0038] 1...robot hand, 2...base, 21...base plate, 23...connection plate, 25...adapter, 3...gripping mechanism, 31, 32...chuck mechanism, 311, 312, 321, 322...fingers, 4...movement mechanism, 41...rail, 43...slider block, 5...suction portion, 51, 52...suction pad, 53, 54...pole.

Claims

1. A robot hand having a base plate, a gripping mechanism for gripping a plate-shaped workpiece at its rear end, a moving mechanism provided on the base plate for moving the gripping mechanism along the front-to-rear direction of the base plate, and at least one suction pad provided at the front end of the base plate and having a suction cup for adsorbing the gripped workpiece at its front end; A pressure increasing / decreasing unit that increases / decreases the pressure inside the suction cup; a control unit that controls the pressurization / depressurization unit to adsorb the gripped workpiece to the suction cup by reducing the pressure inside the suction cup, and controls the pressurization / depressurization unit and the moving mechanism to move the gripped workpiece back and forth while lifting the workpiece by ejecting air from the suction cup toward the workpiece by applying pressure inside the suction cup.

2. The workpiece holding device according to claim 1 , wherein the suction pad has a cylindrical body communicating with the suction cup.

3. 3. The workpiece holding device according to claim 1, wherein the suction pad is supported by a pole erected on the base plate so that the height of the suction pad relative to the base plate is the same as the height of the gripping center of the gripping mechanism.

4. The workpiece holding device according to claim 1 , wherein the suction pads are a pair and spaced apart from each other in the left-right direction of the base plate.

5. A work holding device as described in any one of claims 1 to 4, wherein the suction pad is made of a self-lubricating resin.

6. A work holding device as described in claim 1, further comprising a moving device for moving the robot hand.

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