JP7632387B2 - Robot Hand and Transport System - Google Patents

Description

This disclosure relates to a robot hand and a transport system.

Patent document 1 describes a robot hand that grasps an object with two claws.

Japanese Utility Model Application Publication No. 05-074790

In robotic hands that use claws to grasp objects, depending on the shape and size of the object, the posture of the grasped object may become unstable, causing the object to fall off the robotic hand. For this reason, further ingenuity is required to grasp objects with claws in a way that prevents them from falling off the robotic hand.

This disclosure can be realized in the following forms:

(1) According to a first aspect of the present disclosure, there is provided a robot hand. The robot hand includes a power cylinder having a cylindrical cylinder portion and a rod portion moving along a first direction parallel to a central axis of the cylinder portion, a first claw portion fixed to one of the cylinder portion and the rod portion and provided along a second direction perpendicular to the first direction, a connecting portion rotatably connected to the other of the cylinder portion and the rod portion about a rotation axis parallel to the second direction and provided along a third direction perpendicular to the first direction and the second direction, a second claw portion fixed to one end of the connecting portion and provided along the second direction, and a third claw portion fixed to the other end of the connecting portion and provided along the second direction. Each of the first claw portion, the second claw portion, and the third claw portion has a base end fixed to the cylinder portion or the connecting portion and a tip end provided on the opposite side to the base end, and has a truncated cone-shaped outer shape whose diameter increases from the base end to the tip end.
According to the robot hand of this form, since the connecting portion to which the second and third claws are fixed is rotatably connected to the power cylinder, when one of the second and third claws and the first claw are in contact with an object, a gap is generated between the other of the second and third claws and the object, which causes the posture of the object to become unstable. Furthermore, since each claw has a truncated cone-shaped outer shape whose diameter increases from the base end to the tip end, it is possible to prevent the object from slipping off each claw.
(2) In the robot hand of the above-described form, the first claw portion, the second claw portion, and the third claw portion may have a gripping surface on a side portion of the truncated cone shape that contacts an object, and the friction coefficient of the contact interface between the gripping surface and the object may be greater than the friction coefficient of the contact interface between the connecting portion and the object when the connecting portion contacts the object.
According to this form of robot hand, it is possible to prevent an object from slipping off each claw portion.
(3) In the robot hand of the above aspect, the gripping surface may be provided with an uneven structure.
According to this form of robot hand, the uneven structure can increase the coefficient of friction at the contact interface between each claw and an object.
(4) In the robot hand of the above aspect, the uneven structure may have a plurality of grooves provided along the circumferential direction of the truncated cone shape.
According to the robot hand of this form, it is possible to prevent an object from slipping off each claw portion with a simple configuration.
(5) In the robot hand of the above aspect, the power cylinder may be an electric cylinder.
According to a robot hand of this configuration, the configuration of the robot hand can be simplified compared to a configuration in which the power cylinder is a hydraulic cylinder or an air cylinder.
(6) According to a second aspect of the present disclosure, there is provided a transport system including a robot hand according to the above aspect. The transport system includes a stage having a mounting surface on which an object is placed by the robot hand, a guide pin provided on the mounting surface and inserted into a first positioning hole provided in the object, an elevator device for raising and lowering the stage, and a knock pin that is inserted into a second positioning hole provided in the object by lowering the stage with the object placed on the mounting surface. A maximum distance that the object can move in a direction parallel to the mounting surface when the guide pin is inserted into the first positioning hole is longer than a maximum distance that the object can move in a direction parallel to the mounting surface when the knock pin is inserted into the second positioning hole.
According to this type of transfer system, the object is roughly positioned by the guide pins, and then the stage is lowered to finely position the object by the knock pins. Therefore, the positioning accuracy required when the object is placed on the stage by the robot hand can be relaxed.
The present disclosure may be realized in various forms other than a robot hand or a transport system, for example, in the form of a transport robot.

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a transport system. FIG. 2 is a perspective view showing the configuration of a robot hand. FIG. FIG. FIG. 2 is an explanatory diagram illustrating a state in which a workpiece is gripped by a robot hand. FIG.

A. First embodiment:
1 is a front view showing a schematic configuration of a transfer system 10 according to a first embodiment. The transfer system 10 of this embodiment includes a transfer robot 20 and a processing machine 30. The transfer system 10 transfers a workpiece WK to the processing machine 30 by the transfer robot 20. In this embodiment, the workpiece WK is a die-cast product that is processed by the processing machine 30. More specifically, the workpiece WK is a housing for an automobile transmission.

The transport robot 20 includes a robot hand 200, a robot arm 21, and a robot control device 25. The robot hand 200 is attached to the robot arm 21 and is moved by the robot arm 21. In this embodiment, the robot arm 21 is a vertical multi-joint robot. The robot arm 21 does not have to be a vertical multi-joint robot, and may be, for example, a horizontal multi-joint robot or an orthogonal robot. The robot control device 25 controls the robot hand 200 and the robot arm 21. The robot control device 25 is composed of a computer including a CPU, a memory, an input/output interface, and an internal bus that interconnects these.

The processing machine 30 is equipped with a fixing jig 300 that fixes the workpiece WK. In this embodiment, the processing machine 30 is a cutting machine that performs cutting processing on the workpiece WK fixed to the fixing jig 300, more specifically, a machining center. Note that in other embodiments, the processing machine 30 is not a cutting machine, and may be, for example, a grinding machine that performs grinding processing on the workpiece WK, or a welding machine that performs welding processing on the workpiece WK.

Figure 2 is a perspective view showing the configuration of the robot hand 200 of this embodiment. The robot hand 200 includes a fixed plate 210, two support columns 213, a support plate 215, a power cylinder 220, a rotation mechanism 230, a connecting portion 240, a first claw portion 250A, a second claw portion 250B, and a third claw portion 250C. Note that arrows representing the D1, D2, and D3 axes, which are three mutually orthogonal coordinate axes, are shown in Figure 2. The arrows representing the D1, D2, and D3 axes are also shown in Figures 3 and 4 as appropriate so that the directions indicated by the arrows correspond to those in Figure 2.

The support plate 215 is configured in a flat plate shape. The power cylinder 220 is fixed to the upper surface of the support plate 215. The first claw portion 250A is fixed to the bottom surface of the support plate 215 via a connecting member 218 configured in a rod shape. The fixed plate 210 is arranged above the support plate 215 so as to cross the power cylinder 220. The fixed plate 210 is configured in a flat plate shape and arranged parallel to the support plate 215. The fixed plate 210 is fixed to the support plate 215 via two pillars 213 arranged on either side of the power cylinder 220. The fixed portion 211 that is fixed to the robot arm 21 is provided on the upper surface of the fixed plate 210.

The power cylinder 220 includes a cylinder portion 221, a rod portion 222, and a drive portion 225. The cylinder portion 221 is fixed to the upper surface of the support plate 215. The cylinder portion 221 is configured in a cylindrical shape and is arranged so that the central axis of the cylinder portion 221 is parallel to the upper surface of the support plate 215. The rod portion 222 is configured in a rod shape. The base end of the rod portion 222 is stored in the cylinder portion 221, and the tip end of the rod portion 222 protrudes from one end of the cylinder portion 221. The drive portion 225 moves the rod portion 222 along the central axis of the cylinder portion 221. The drive portion 225 is driven under the control of the robot control device 25. In this embodiment, the power cylinder 220 is an electric cylinder, and the drive portion 225 is configured by a motor, a ball screw for converting the rotational motion of the motor into the linear motion of the rod portion 222, and the like. In other embodiments, the power cylinder 220 may be a hydraulic cylinder driven by hydraulic pressure or an air cylinder driven by air pressure, rather than an electric cylinder.

A rotation mechanism 230 is fixed to the tip of the rod portion 222. The rotation mechanism 230 rotatably supports the connecting portion 240. The rotation axis RX of the connecting portion 240 is perpendicular to the direction parallel to the central axis of the cylinder portion 221 and parallel to the direction from the top surface to the bottom surface of the support plate 215. The connecting portion 240 includes a beam portion 241 and two protrusions 242. The beam portion 241 is a rod-shaped portion provided along a direction perpendicular to the direction parallel to the central axis of the cylinder portion 221 and the direction parallel to the rotation axis RX of the connecting portion 240, and the two protrusions 242 are rod-shaped portions protruding downward from both ends of the beam portion 241. The connecting portion 240 has a U-shaped external shape as a whole due to the beam portion 241 and the two protrusions 242. A second claw 250B is fixed to the tip of one of the two protrusions 242, and a third claw 250C is fixed to the tip of the other of the two protrusions 242.

The rod portion 222 of the power cylinder 220 extends and retracts, and thereby the rotation mechanism 230, the connecting portion 240, the second claw portion 250B, and the third claw portion 250C move. When the rod portion 222 retracts with the workpiece WK disposed between the first claw portion 250A, the second claw portion 250B, and the third claw portion 250C, the workpiece WK is sandwiched between the first claw portion 250A, the second claw portion 250B, and the third claw portion 250C, and the workpiece WK is gripped by the robot hand 200. When the rod portion 222 extends with the workpiece WK being gripped by the first claw portion 250A, the second claw portion 250B, and the third claw portion 250C, the grip of the workpiece WK by the robot hand 200 is released. In the following description, when the first claw portion 250A, the second claw portion 250B, and the third claw portion 250C are not particularly distinguished from each other, the first claw portion 250A, the second claw portion 250B, and the third claw portion 250C are simply referred to as claw portions 250. Note that the direction parallel to the central axis of the cylinder portion 221 is sometimes referred to as the first direction, the direction parallel to the rotation axis RX of the connecting portion 240 is sometimes referred to as the second direction, and the direction parallel to the extension direction of the beam portion 241 is sometimes referred to as the third direction.

Figure 3 is a perspective view showing the configuration of the claw portion 250 of the robot hand 200. The claw portion 250 has a base end portion 251 and a tip end portion 252. In the first claw portion 250A, the base end portion 251 is the end portion on the cylinder portion 221 side, and in the second claw portion 250B and the third claw portion 250C, the base end portion 251 is the end portion on the connecting portion 240 side. The tip end portion 252 is the end portion on the opposite side to the base end portion 251.

The claw portion 250 has a truncated cone-shaped outer shape whose diameter increases from the base end 251 to the tip end 252. The claw portion 250 has a gripping surface 255 that comes into contact with the workpiece WK. The gripping surface 255 is provided on the side portion of the truncated cone shape. It is preferable that the angle θ between the central axis CL of the claw portion 250 and the gripping surface 255 is greater than 1 degree. It is preferable that the angle θ between the central axis CL of the claw portion 250 and the gripping surface 255 is 45 degrees or less, and more preferably 5 degrees or less.

The static friction coefficient of the contact interface between the gripping surface 255 and the workpiece WK is greater than the static friction coefficient of the contact interface between the connecting portion 240 and the workpiece WK when the connecting portion 240 and the workpiece WK are in contact with each other. In this embodiment, the gripping surface 255 is provided with an uneven structure 256, thereby increasing the static friction coefficient of the contact interface between the gripping surface 255 and the workpiece WK. The uneven structure 256 is composed of a plurality of grooves 257. Each groove 257 is provided along the circumferential direction of the claw portion 250, that is, along the circumferential direction of the truncated cone shape. Each groove 257 is provided parallel to each other. The claw portion 250 is formed of steel that has been subjected to a hardening treatment. The surface of the connecting portion 240 is configured to be smooth. The material of the connecting portion 240 may be the same as the material of the claw portion 250, or may be different from the material of the claw portion 250. In another embodiment, the uneven structure 256 may be formed by a single groove that is spirally arranged around the central axis CL of the claw portion 250. The uneven structure 256 may be formed by fine unevenness formed by blasting.

Figure 4 is a cross-sectional view showing the configuration of the rotation mechanism 230. In this embodiment, the rotation mechanism 230 includes a flange portion 231, an upper surface portion 232, a side wall portion 233, a bottom surface portion 234, a shaft portion 235, a set screw 237, and a coil spring 239.

The flange portion 231 is a flat portion that is provided perpendicular to the central axis of the cylinder portion 221. The flange portion 231 is fixed to the tip of the rod portion 222 by a fixing device 228. The upper surface portion 232 is connected to the lower end of the flange portion 231. The upper surface portion 232 is a rectangular flat portion that is provided perpendicular to the flange portion 231. The bottom surface portion 234 is disposed below the upper surface portion 232. The bottom surface portion 234 is a rectangular flat portion that is provided parallel to the upper surface portion 232. The end of the bottom surface portion 234 opposite the cylinder portion 221 is connected to the end of the upper surface portion 232 opposite the cylinder portion 221 by the side wall portion 233. The side wall portion 233 is a rectangular flat portion that is provided perpendicular to the upper surface portion 232 and the bottom surface portion 234. The shaft portion 235 is a rod-shaped member disposed perpendicular to the top surface portion 232 and the bottom surface portion 234. The upper end portion of the shaft portion 235 is fixed to the center portion of the top surface portion 232, and the lower end portion of the shaft portion 235 is fixed to the center portion of the bottom surface portion 234.

Between the top surface portion 232 and the bottom surface portion 234, the beam portion 241 of the connecting portion 240 is disposed. The shaft portion 235 penetrates the center of the beam portion 241, and the connecting portion 240 rotates around the shaft portion 235. The side wall portion 233 has two screw holes aligned along the direction in which the beam portion 241 extends, and a set screw 237 is inserted into each screw hole. The rotation of the connecting portion 240 is restricted by the beam portion 241 contacting the set screw 237. The rotatable range of the connecting portion 240 can be adjusted by adjusting the position of the set screw 237. A coil spring 239 is wound around one of the two set screws 237. One end of the coil spring 239 is in contact with the side wall portion 233, and the other end of the coil spring 239 is in contact with the connecting portion 240. When the grip of the workpiece WK by the robot hand 200 is released, the connecting part 240 biased by the coil spring 239 comes into contact with the other of the two set screws 237. The provision of the coil spring 239 prevents the connecting part 240 from swinging when the grip of the workpiece WK is released.

Figure 5 is an explanatory diagram that shows a schematic diagram of how the workpiece WK is gripped by the robot hand 200. In this embodiment, when one of the second claw portion 250B and the third claw portion 250C comes into contact with the workpiece WK while the rod portion 222 is being retracted, the connecting portion 240 rotates due to the reaction force that the one of the second claw portion 250B and the third claw portion 250C receives from the workpiece WK, and the other of the second claw portion 250B and the third claw portion 250C also comes into contact with the workpiece WK. Therefore, by retracting the rod portion 222 while the first claw portion 250A is in contact with the workpiece WK, the three claw portions 250A to 250C can be brought into close contact with the workpiece WK.

Figure 6 is an explanatory diagram showing a schematic configuration of the fixing jig 300. The fixing jig 300 includes a first base plate 310A and a second base plate 310B. A stage 320 is provided on the first base plate 310A. The stage 320 has a mounting surface PL on which the workpiece WK is placed. The mounting surface PL is directed upward. Two guide pins 321, 322 protrude upward from the mounting surface PL. The transport robot 20 places the workpiece WK on the mounting surface PL so that the two guide pins 321, 322 are inserted into the two first positioning holes provided in the workpiece WK. By inserting the guide pins 321, 322 into the first positioning holes, the workpiece WK is positioned with relatively rough accuracy in a direction parallel to the mounting surface PL. Relatively coarse accuracy means that the accuracy is coarse compared to the accuracy of positioning the workpiece WK by the knock pins 341 and 342 described later. In other words, the maximum distance that the workpiece WK can move in a direction parallel to the placement surface PL when the workpiece WK is positioned by the guide pins 321 and 322 is longer than the maximum distance that the workpiece WK can move in a direction parallel to the placement surface PL when the workpiece WK is positioned by the knock pins 341 and 342. In this embodiment, since the connecting portion 240 of the robot hand 200 rotates, it may be difficult for the transfer robot 20 to place the workpiece WK on the placement surface PL with good positional accuracy. Therefore, in this embodiment, the workpiece WK is first positioned with relatively rough accuracy by the guide pins 321 and 322, and then the workpiece WK is positioned with good accuracy by the knock pins 341 and 342.

The stage 320 is moved in a direction perpendicular to the placement surface PL by the lifting device 325. When the stage 320 is lowered with the workpiece WK positioned by the guide pins 321 and 322, two knock pins 341 and 342 provided on the first base plate 310A are inserted into two second positioning holes provided in the workpiece WK. The knock pins 341 and 342 have a conical outer shape with a central axis perpendicular to the upper surface of the first base plate 310A, and the diameter becomes smaller as they move away from the upper surface of the first base plate 310A. Therefore, even when the workpiece WK is positioned with relatively rough accuracy by the guide pins 321 and 322, the knock pins 341 and 342 are easily inserted into the second positioning holes. By inserting the knock pins 341 and 342 into the second positioning holes, the workpiece WK is positioned in a direction parallel to the placement surface PL.

After the knock pins 341, 342 are inserted into the second positioning holes, the stage 320 further descends, causing the workpiece WK to come into contact with the three support pins 331-333 provided on the first base plate 310A. The mounting surface PL of the stage 320 descends to a position lower than the tips of the support pins 331-333, so the workpiece WK moves away from the mounting surface PL and is supported by the support pins 331-333. The workpiece WK is positioned in a direction perpendicular to the mounting surface PL by being supported by the support pins 331-333. The workpiece WK is then fixed onto the first base plate 310A by the three clamp devices 351-353 provided on the first base plate 310A.

In the fixing jig 300, the second base plate 310B is arranged on the back side of the first base plate 310A. The first base plate 310A and the second base plate 310B can be inverted by the tilt mechanism 315 shown in FIG. 1. In this embodiment, the tilt mechanism 315, the lifting device 325, and the clamp devices 351 to 353 are driven under the control of the control device 35 of the processing machine 30 shown in FIG. 1. The configuration of the second base plate 310B is the same as that of the first base plate 310A. However, the workpiece WK fixed to the second base plate 310B has a different shape and size from the workpiece WK fixed to the first base plate 310A. Guide pins 321, 322 and knock pins 341, 342 are arranged according to the shape and size of the workpiece WK, so the arrangement of guide pins 321, 322 and knock pins 341, 342 is different between first base plate 310A and second base plate 310B. By using first base plate 310A and second base plate 310B appropriately, multiple types of workpieces WK can be fixed with one fixing jig 300.

According to the robot hand 200 in the present embodiment described above, the connecting portion 240 to which the second claw portion 250B and the third claw portion 250C are fixed is rotatably connected to the rod portion 222 by the rotation mechanism 230, so that when one of the second claw portion 250B and the third claw portion 250C and the first claw portion 250A are in contact with the workpiece WK, it is possible to prevent a gap from being generated between the other of the second claw portion 250B and the third claw portion 250C and the workpiece WK. In other words, the three claw portions 250A to 250C can be brought into close contact with the workpiece WK. Therefore, it is possible to prevent the posture of the workpiece WK gripped by the three claw portions 250A to 250C from becoming unstable. Furthermore, each of the claws 250A-250C has a truncated cone shape with a diameter that increases from the base end 251 to the tip end 252, which prevents the workpiece WK from slipping off each of the claws 250A-250C. This reduces the gripping force applied to the workpiece WK by each of the claws 250A-250C, allowing the power cylinder 220 used to generate the gripping force to be made smaller.

In addition, in this embodiment, the friction coefficient of the contact interface between the gripping surface 255 of each of the claws 250A to 250C and the workpiece WK is greater than the friction coefficient of the contact interface between the connecting portion 240 and the workpiece WK when the connecting portion 240 and the workpiece WK come into contact with each other. Therefore, the workpiece WK can be effectively prevented from slipping off each of the claws 250A to 250C.

In addition, in this embodiment, the gripping surface 255 of each of the claws 250A to 250C is provided with an uneven structure 256. This increases the coefficient of friction at the contact interface between the gripping surface 255 of each of the claws 250A to 250C and the workpiece WK.

In addition, in this embodiment, the uneven structure 256 is composed of multiple grooves 257 arranged along the circumferential direction of the truncated cone shape. Therefore, with a simple configuration, it is possible to prevent the workpiece WK from slipping off each of the claws 250A to 250C.

In addition, in this embodiment, the power cylinder 220 is configured as an electric cylinder. Therefore, the structure of the robot hand 200 can be simplified compared to an embodiment in which the power cylinder 220 is configured as a hydraulic cylinder or an air cylinder.

In addition, in this embodiment, the fixing jig 300 is configured so that the workpiece WK is roughly positioned by the guide pins 321, 322, and then the stage 320 is lowered so that the workpiece WK can be finely positioned by the knock pins 341, 342. Therefore, the positioning accuracy required when the workpiece WK is placed on the stage 320 by the robot hand 200 can be relaxed.

B. Other embodiments:
(B1) In the robot hand 200 of the first embodiment described above, the first claw portion 250A is fixed to the cylinder portion 221, and the second claw portion 250B and the third claw portion 250C are fixed to the rod portion 222 via the rotation mechanism 230 and the connecting portion 240. Alternatively, the first claw portion 250A may be fixed to the rod portion 222, and the second claw portion 250B and the third claw portion 250C may be fixed to the cylinder portion 221 via the rotation mechanism 230 and the connecting portion 240.

(B2) In the robot hand 200 of the first embodiment described above, the gripping surface 255 of each of the claws 250A to 250C is provided with an uneven structure 256. In contrast, the gripping surface 255 of each of the claws 250A to 250C does not have to be provided with an uneven structure 256. In this case, it is preferable that each of the claws 250A to 250C is formed from a material that has a high coefficient of static friction with the workpiece WK.

(B3) In the robot hand 200 of the first embodiment described above, the static friction coefficient of the contact interface between the gripping surface 255 of each claw portion 250A to 250C and the workpiece WK is greater than the static friction coefficient of the contact interface between the connecting portion 240 and the workpiece WK when the connecting portion 240 and the workpiece WK come into contact. In contrast, the static friction coefficient of the contact interface between the gripping surface 255 of each claw portion 250A to 250C and the workpiece WK may be less than the static friction coefficient of the contact interface between the connecting portion 240 and the workpiece WK when the connecting portion 240 and the workpiece WK come into contact. However, it is preferable that the static friction coefficient of the contact interface between the gripping surface 255 of each claw portion 250A to 250C and the workpiece WK is high enough to prevent the workpiece WK from slipping off each claw portion 250A to 250C.

(B4) In the transport system 10 of the first embodiment described above, the transport robot 20 transports the workpiece WK to be processed by the processing machine 30. In contrast, the transport robot 20 may be used to transport objects other than the workpiece WK, such as boxes. In this case, the transport robot 20 may place the object to be transported on, for example, a conveyor, instead of on the fixed jig 300.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

10...Transport system, 20...Transport robot, 21...Robot arm, 25...Robot control device, 30...Processing machine, 35...Control device, 200...Robot hand, 210...Fixed plate, 211...Fixed part, 213...Support column, 215...Support plate, 218...Connecting member, 220...Power cylinder, 221...Cylinder part, 222...Rod part, 225...Drive part, 228...Fixing tool, 230...Rotation mechanism, 231...Flange part, 232...Top part, 233...Side wall part, 234...Bottom part, 235...Shaft part, 237...Set screw, 239...Coil spring, 240...connecting part, 241...beam part, 242...protruding part, 250A...first claw part, 250B...second claw part, 250C...third claw part, 251...base end part, 252...tip part, 255...gripping surface, 256...uneven structure, 257...groove, 300...fixing jig, 310A...first base plate, 310B...second base plate, 315...tilt mechanism, 320...stage, 321, 322...guide pin, 325...lifting device, 331-333...support pin, 341, 342...knock pin, 351-353...clamping device, PL...mounting surface, WK...workpiece

Claims (5)

A robotic hand,
a power cylinder having a cylindrical cylinder portion and a rod portion that moves along a first direction parallel to a central axis of the cylinder portion;
a first claw portion fixed to one of the cylinder portion and the rod portion and provided along a second direction perpendicular to the first direction;
a connecting portion that is connected to the other of the cylinder portion and the rod portion so as to be rotatable about a rotation axis parallel to the second direction and is provided along a third direction perpendicular to the first direction and the second direction;
A second claw portion fixed to one end of the connecting portion and provided along the second direction;
A third claw portion is fixed to the other end of the connecting portion and is provided along the second direction;
Equipped with
Each of the first claw portion, the second claw portion, and the third claw portion has a base end portion fixed to the cylinder portion or the connecting portion, and a tip end portion provided on the opposite side to the base end portion, and has an outer shape of a truncated cone shape whose diameter increases from the base end portion to the tip end portion,
The first claw portion, the second claw portion, and the third claw portion each have a gripping surface that contacts an object on a side surface portion of the truncated cone shape,
a friction coefficient of a contact interface between the gripping surface and the object is greater than a friction coefficient of a contact interface between the connecting portion and the object when the connecting portion comes into contact with the object;
Robot hand. The robot hand according to claim 1 ,
The robot hand has a gripping surface provided with an uneven structure. The robot hand according to claim 2 ,
The robot hand, wherein the uneven structure has a plurality of grooves provided along the circumferential direction of the truncated cone shape. The robot hand according to claim 1 ,
The robot hand, wherein the power cylinder is an electric cylinder. 1. A conveying system comprising:
A robot hand and
a stage having a mounting surface on which an object is placed by the robot hand;
A guide pin provided on the placement surface and inserted into a first positioning hole provided in the object;
A lifting device that lifts and lowers the stage;
a knock pin that is inserted into a second positioning hole provided in the object by lowering the stage while the object is placed on the placement surface; and
Equipped with
The robot hand includes:
a power cylinder having a cylindrical cylinder portion and a rod portion that moves along a first direction parallel to a central axis of the cylinder portion;
a first claw portion fixed to one of the cylinder portion and the rod portion and provided along a second direction perpendicular to the first direction;
a connecting portion that is connected to the other of the cylinder portion and the rod portion so as to be rotatable about a rotation axis parallel to the second direction and is provided along a third direction perpendicular to the first direction and the second direction;
A second claw portion fixed to one end of the connecting portion and provided along the second direction;
A third claw portion is fixed to the other end of the connecting portion and is provided along the second direction;
Equipped with
Each of the first claw portion, the second claw portion, and the third claw portion has a base end portion fixed to the cylinder portion or the connecting portion, and a tip end portion provided on the opposite side to the base end portion, and has an outer shape of a truncated cone shape whose diameter increases from the base end portion to the tip end portion,
a maximum distance that the object can move in a direction parallel to the placement surface when the guide pin is inserted into the first positioning hole is longer than a maximum distance that the object can move in a direction parallel to the placement surface when the knock pin is inserted into the second positioning hole.
Conveying system.

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