CN115190833A

CN115190833A - Workpiece holding mechanism

Info

Publication number: CN115190833A
Application number: CN202080097641.7A
Authority: CN
Inventors: 筑地夏生; 川本典弘; 石津雄平; 杉浦泰彦
Original assignee: JATCO Ltd
Current assignee: JATCO Ltd
Priority date: 2020-02-27
Filing date: 2020-12-18
Publication date: 2022-10-14
Also published as: JP7165284B2; JPWO2021171752A1; WO2021171752A1

Abstract

The workpiece holding mechanism includes: a first gripping section having a pair of gripping pins parallel to each other; and a second holding part having a pair of holding pins parallel to each other. The first gripping portion and the second gripping portion are provided so as to be relatively displaceable on a common axis. The workpiece gripping mechanism grips the workpiece by the pair of gripping pins of the first gripping portion and the pair of gripping pins of the second gripping portion.

Description

Workpiece holding mechanism

Technical Field

The present invention relates to a workpiece holding mechanism.

Background

JP2003-211384A discloses a robot hand for a screw tightening operation.

The robot hand of JP2003-211384A has a socket externally fitted to the head of the screw. The robot hand rotates the socket externally fitted to the head of the screw around the central axis of the screw, thereby integrally rotating the socket and the screw, and screwing and fastening the screw to the counterpart member.

In the socket of JP2003-211384A, a fitting hole is opened in a portion facing the screw, and the head of the screw is inserted into the fitting hole, whereby the socket is fitted to the head of the screw.

The head of the screw has a polygonal shape such as a hexagon in general outer shape as viewed from the central axis direction of the screw. Therefore, the cross-sectional shape of the fitting hole as viewed from the central axis direction of the screw is formed to be the same as the outer shape of the head of the screw.

Here, when the socket is fitted to the head of the screw, it is necessary to match the phase of the socket and the phase of the screw in the circumferential direction around the central axis.

It is preferable to shorten or omit the time required for phase alignment, since the screw fastening operation can be performed more efficiently.

Disclosure of Invention

According to one embodiment of the present invention, there is provided a workpiece holding mechanism including:

a first gripping section having a pair of gripping pins parallel to each other;

a second holding part having a pair of holding pins parallel to each other,

the first gripping portion and the second gripping portion are arranged to be relatively displaceable on a common axis, wherein,

the workpiece is gripped by the pair of gripping pins of the first gripping portion and the pair of gripping pins of the second gripping portion.

According to the above aspect, since the time required for phase alignment can be omitted, the screw fastening operation can be performed more efficiently.

Drawings

Fig. 1 is a diagram illustrating a robot arm.

Fig. 2A is a diagram illustrating a bolt as a holding object.

Fig. 2B is a diagram illustrating a bolt as an object to be gripped.

Fig. 3A is a diagram illustrating a hand.

Fig. 3B is a diagram illustrating a hand.

Fig. 4A is a diagram illustrating a hand.

Fig. 4B is a diagram illustrating a hand.

Fig. 5A is a diagram illustrating the grip portion.

Fig. 5B is a diagram illustrating the grip portion.

Fig. 5C is a diagram illustrating the grip portion.

Fig. 5D is a diagram illustrating the grip portion.

Fig. 6A is a diagram illustrating the grip portion.

Fig. 6B is a diagram illustrating the grip portion.

Fig. 7A is a diagram illustrating a process of holding a bolt with a hand.

Fig. 7B is a diagram illustrating a process of holding a bolt by a hand.

Fig. 7C is a diagram illustrating a process of holding the bolt with a hand.

Fig. 7D is a diagram illustrating a process of holding the bolt with a hand.

Fig. 8 is a diagram illustrating a process of holding a bolt with a hand.

Fig. 9A is a diagram illustrating a process of holding a bolt with a hand.

Fig. 9B is a diagram illustrating a process of holding the bolt with a hand.

Fig. 9C is a diagram illustrating a process of holding the bolt by hand.

Fig. 10A is a diagram illustrating a grip portion according to a modification.

Fig. 10B is a diagram illustrating a modified example of the grip portion.

Detailed Description

Hereinafter, a case in which an embodiment of the present invention is applied to a robot 2 that performs a fastening operation of a bolt 3 will be described as an example.

Fig. 1 is a diagram illustrating a robot arm 21.

Fig. 2A is a side view of the bolt 3, and fig. 2B is a sectional view of the head 31 of the bolt 3 taken along line IIb-IIb in fig. 2A.

As shown in fig. 1, the robot 2 includes a conventionally known articulated robot arm 21. The robot arm 21 is configured by connecting a plurality of arm members so as to be rotatable about 8 rotation axes X1 to X8.

A base end of the robot arm 21 is provided on the base 20 so as to be rotatable about a rotation axis X1. A connection portion 25 connected to the hand 4 is provided at the distal end portion of the robot arm 21 so as to be rotatable about the rotation axis X8.

The hand 4 is rotatable around the rotation axis X8 integrally with the connection portion 25.

In the present embodiment, the object (workpiece) to be held by the hand 4 is the headed bolt 3.

The robot arm 21 is driven by a control device (not shown), and after the bolt 3 held by the hand 4 is arranged at a desired position (coordinate), the hand 4 is rotated about the rotation axis X8, whereby the bolt 3 held by the hand 4 is screwed and fastened to the counterpart member.

As shown in fig. 2A, the bolt 3 has a head portion 31 having a larger diameter than the shaft portion 32 at one end of the shaft portion 32.

As shown in fig. 2B, the head 31 of the bolt 3 has a regular polygonal shape in a cross section orthogonal to the central axis C of the bolt 3.

In the present embodiment, the head 31 of the bolt 3 has a cross section in the shape of a regular hexagon in which a plurality of straight outer peripheries 311 are continuously connected in the circumferential direction around the center axis C. The length of each outer periphery 311 of the head 31 is the same length L3.

The head 31 has 3 sets of

outer peripheries

311, 311 parallel to each other with the center axis C therebetween as viewed from the center axis C. The head 31 of the bolt 3 is gripped by the hand 4.

Fig. 3A is a front view of the hand 4 when the hand 4 is disposed in an orientation in which the bolt 3 is held, and is a partially cut-away view in cross section. Fig. 3B is a sectional view taken along line IIIb-IIIb in fig. 3A, and illustrates the arrangement of the holding pin 64 and the positioning pin 66.

In the following description, when describing the positional relationship of the components of the hand 4, terms such as the upper side and the lower side in the arrangement of fig. 3A, the one side and the other side with reference to the reference line Cz, and the one side and the other side with reference to the axis Cy in fig. 3B are used as necessary.

As shown in fig. 3A and 3B, the hand 4 includes a workpiece gripping mechanism 1, and the workpiece gripping mechanism 1 includes a fixed portion 40 connected to the connection portion 25, a pair of movable portions 45 (45A and 45B), and gripping portions 6 (6A and 6B) provided on the movable portions 45 (45A and 45B).

The fixing portion 40 has a columnar base member 41. The base member 41 has a coupling portion 25 of the robot arm 21 coupled to a substantially central portion of the base member 41 in the longitudinal direction.

Support wall portions

42, 42 for supporting the movable portion 45 (45A, 45B) are provided at one end 41a and the other end 41B of the base member 41 in the longitudinal direction.

The

support wall portions

42 and 42 extend from the lower side surface 41d of the base member 41 in a direction away from the connection portion 25 (lower side in fig. 3A).

The lower side surface 41d is a side surface opposite to the side surface 41c to which the coupling portion 25 is coupled in the direction of the reference line Cz.

The

support wall portions

42, 42 are disposed in an orthogonal orientation with respect to the base member 41. The

support wall portions

42, 42 are symmetrically disposed on one side and the other side of the reference line Cz with the reference line Cz interposed therebetween. The reference line Cz is a straight line passing through the center of the base member 41 in the longitudinal direction and orthogonal to the base member 41 in the longitudinal direction, and is concentric with the rotation axis X8 of the connection portion 25. The hand 4 rotates around the reference line Cz (rotation axis X8) in conjunction with the rotation of the connection portion 25 of the robot arm 21.

Through

holes

420, 420 are provided on the

lower end portions

42a, 42a of the

support wall portions

42, 42. The through

holes

420, 420 penetrate the

support wall portions

42, 42 in the thickness direction (the axis Cx direction).

The through

holes

420, 420 are located at the center in the width direction (the direction of the axis Cy) of the support wall 42. The through

holes

420 and 420 are arranged in parallel with each other at intervals in the longitudinal direction (vertical direction in fig. 3A) of the support wall 42.

Here, the axis Cx is a straight line orthogonal to the reference line Cz and extending in the displacement direction of the movable portion 45 (45A, 45B). The axis Cy is perpendicular to the reference line Cz and is a straight line along the width direction (vertical direction in fig. 3B) of the movable portion 45 (45A, 45B).

The base line Cz and the axes Cx and Cy are orthogonal to each other.

The guide pins 46, 46 of the movable portion 45 (45A, 45B) pass through the through

holes

420, 420 of the

support wall portions

42, 42.

The movable portions 45 (45A, 45B) are provided on the

support wall portions

42, 42 so as to be movable in the axis Cx direction by the guide pins 46, 46 penetrating the through

holes

420, 420.

The

movable portions

45A and 45B are provided at intervals on a common axis Cx along the longitudinal direction of the base member 41.

In the front view, the movable portion 45A and the movable portion 45B are provided on one side and the other side of the reference line Cz in a state where the distances from the reference line Cz are matched (see fig. 3A). The

movable portions

45A and 45B can be relatively displaced in the axis Cx direction by a drive mechanism, not shown, in a state where the distance from the reference line Cz is matched. Further, as shown in fig. 3B, the movable portion 45A and the movable portion 45B can be relatively displaced in the direction of the axis Cx in a state where the distances from the axis Cy orthogonal to the reference line Cz are matched.

The

movable portions

45A and 45B have a plate-shaped base portion 47 to which a pair of guide pins 46 and 46 are coupled.

The base portion 47 is provided in parallel with the support wall portion 42 on the outer side of the support wall portion 42 in the direction of the axis Cx.

Base end portions

46b, 46b of the pair of guide pins 46, 46 are inserted into support holes 471, 471 provided in the base portion 47.

The guide pins 46, 46 extend from a side surface 47c of the base portion 47 on the support wall portion 42 side toward the reference line Cz. The leading ends 46A, 46A of the guide pins 46, 46 reach above the

grips

6A, 6B.

The base 47 has a predetermined length L47 in the direction of the reference line Cz. An end 47a of the base 47 on the side opposite to the base member 41 (lower side in fig. 3A) is disposed at a position farther from the base member 41 than the support wall portion 42.

Connecting

beams

48, 48 extending toward the reference line Cz side are fixed to the end 47a side of the base 47. The coupling beams 48, 48 are provided on both sides of the base portion 47 in the width direction (the direction of the axis Cy) and are arranged in parallel to each other in a symmetrical positional relationship with the axis Cx (see fig. 3B).

As shown in fig. 3A, the connection beams 48, 48 extending from the base 47 are parallel to the guide pins 46, 46. The coupling beams 48, 48 extend toward the reference line Cz side at positions avoiding interference with the support wall portion 42. The

grip portions

6A, 6B for gripping the bolt 3 are fixed to the

distal ends

48a, 48a of the coupling beams 48, 48 by hexagonal-hole-equipped bolts B1, B3.

Fig. 4A is a perspective view of the movable portion 45 (45A, 45B), and shows one movable portion 45A and the other movable portion 45B separately. Fig. 4B is an exploded perspective view of the grip portion 6A attached to the movable portion 45A.

Fig. 5A is a front view of the grip portion 6. Fig. 5B is a cross-sectional view of the grip portion 6 taken along line Vb-Vb in fig. 5A. Fig. 5C is a cross-sectional view of the grip portion 6 taken along the line Vc-Vc in fig. 5A. Fig. 5D is a sectional view of the grip portion 6 taken along line Vd-Vd in fig. 5A. Since the gripping

portions

6A and 6B have the same configuration, they are denoted as gripping portions 6 in fig. 5A.

As shown in fig. 4A and 4B, the gripping

portions

6A and 6B are composed of a gripping block 61 having a pair of gripping pins 64 and positioning blocks 65 and 65 having a positioning pin 66.

As shown in fig. 5A and 5B, the grip block 61 is provided with a support portion 611 for supporting the grip pins 64, 64 at the center of the plate-shaped base 610.

Regions on both ends in the longitudinal direction (the left-right direction in fig. 5B) of one side surface 610a in the thickness direction of the base 610 serve as joint surfaces with the coupling beams 48, 48. Further, regions on both longitudinal end sides of the other side surface 610b in the thickness direction of the base 610 serve as joint surfaces of the positioning blocks 65, 65. The joint surfaces with the coupling beams 48, 48 and the joint surfaces with the positioning blocks 65, 65 are flat surfaces parallel to each other.

The positioning blocks 65, 65 are pressed against the side surface 610B of the base 610 by the fastening force of bolts B3, B3 penetrating the positioning blocks 65, 65 and the base 610.

The base 610 of the holding block 61 is fixed to the

distal ends

48a, 48a of the coupling beams 48, 48 by bolts B1, B3 penetrating through regions on both ends in the longitudinal direction.

As shown in fig. 5D, the positioning block 65 is formed in a rectangular parallelepiped shape, and one side edge 65c in the direction of the reference line Cz is provided at a position flush with the side edge 61c of the grip block 61. The other side edge 65d of the positioning block 65 is provided at a distance from the other side edge 61d of the grip block 61 at which the bolt B1 can be disposed.

A positioning pin 66 having a cylindrical shape is fixed to a side edge 65c of the positioning block 65. The positioning pin 66 protrudes downward from the side edge 65c of the positioning block 65.

As shown in fig. 5B, the support portion 611 extends between the positioning blocks 65, 65 in a direction away from the connecting beam 48.

As shown in fig. 5C, the end face 65a of the positioning block 65 is disposed at a position separated from the coupling beam 48 by a predetermined distance L1, compared to the end face 61a of the holding block 61.

A support hole 612 into which the cylindrical holding pin 64 is inserted is opened in the lower side edge 61c of the support portion 611. A bolt B2 penetrating the support portion 611 is screwed into the upper end portion of the holding pin 64, and the holding pin 64 is prevented from falling off from the support portion 611 by the bolt B2.

As shown in fig. 5A, in the support portion 611, the gripping pins 64 are provided symmetrically with respect to the reference line Cz.

The projection height h1 of the holding pin 64 projecting from the lower side edge 61c of the holding block 61 is the same as the projection height h1 of the positioning pin 66 projecting from the lower side edge 65c of the positioning block 65.

The grip pin 64 and the positioning pin 66 are provided in parallel with each other in a direction along the reference line Cz.

Fig. 6A is an enlarged view of a region B in fig. 3B, and is a view showing a state in which the head 31 of the bolt 3 is gripped. Fig. 6B is a view showing another holding form of the head 31 of the bolt 3. In fig. 6A and 6B, the position of the outer periphery 311 of the head 31 of the bolt 3 is shown by a phantom line.

As shown in fig. 6A and 6B, the gripping

pins

64 and 64 are positioned on an axis Cy1 parallel to an axis Cy orthogonal to the reference line Cz.

The gripping pins 64, 64 have a circular cross section, and the centers of the

gripping pins

64, 64 are located on the axis Cy 1.

The gripping pins 64, 64 are provided in a symmetrical positional relationship with respect to an axis Cx perpendicular to the reference line Cz and the axis Cy.

The center-to-center distance L64 between the

gripping pins

64 and 64 in the direction of the axis Cy is set to a length shorter than the length L3 of one side of the straight outer periphery 311 of the head 31 of the bolt 3 (L3 > L64).

Thus, when the head 31 of the bolt 3 is gripped between the

grips

6A, 6B in the orientation shown in fig. 6A, the pair of grip pins 64, 64 are pressure-contacted to the same outer periphery 311 of the head 31.

Here, the gripping

pins

64, 64 of the one gripping part 6A and the

gripping pins

64, 64 of the other gripping part 6B of the reference line Cz are respectively pressed against

outer peripheries

311, 311 parallel to each other with the axis Cy therebetween. As described above, the center-to-center distance L64 between the

gripping pins

64, 64 is set to a length shorter than the length L3 of the outer periphery 311 of the head 31 of the bolt 3. Therefore, the head 31 of the bolt 3 is reliably gripped between the

gripping pins

64, 64 of the one gripping part 6A and the

gripping pins

64, 64 of the other gripping part 6B.

When the head 31 of the bolt 3 is gripped between the

gripping portions

6A and 6B in the direction shown in fig. 6B, the gripping

pins

64 and 64 of one gripping portion 6A and the

gripping pins

64 and 64 of the other gripping portion 6B are pressed against the

outer peripheries

311 and 311 adjacent to each other with the corner 31a of the head 31 interposed therebetween, respectively, thereby restricting the movement of the bolt 3 in the direction of the axis Cx. Therefore, the head 31 of the bolt 3 is reliably gripped between the

gripping pins

64, 64 of the one gripping part 6A and the

gripping pins

64, 64 of the other gripping part 6B.

The alignment pins 66, 66 are located on an axis Cy2 parallel to the axis Cy orthogonal to the reference line Cz.

The positioning pins 66, 66 have a circular cross section, and the centers of the positioning pins 66, 66 are located on the axis Cy 2.

The axis Cy2 is located closer to the axis Cy than the axis Cy 1.

The positioning pins 66, 66 are provided in a symmetrical positional relationship with each other across an axis Cx orthogonal to the reference line Cz and the axis Cy.

The distance L66 between positioning pins 66, 66 in the direction of axis Cy is set to be longer than the length L3 of one side of the straight outer periphery 311 of head 31 of bolt 3 (L66 > L3).

In the present embodiment, the spacing distance L66 is set such that when the head 31 of the bolt 3 is gripped between the

grips

6A, 6B in the orientation shown in fig. 6A, the positioning pins 66, 66 abut against the outer periphery 311 adjacent to the outer periphery 311 with which the grip pins 64, 64 are in pressure contact. This is to restrict the positional displacement of the head 31 of the bolt 3 in the direction of the axis Cy.

Further, the center-to-center distance D1 in the direction of the axis Cx between the positioning pin 66 and the grip pin 64 is set so that the positioning pins 66, 66 do not contact the outer periphery 311 of the grip pins 64, 64 in pressure contact when the head 31 of the bolt 3 is gripped between the

grip portions

6A, 6B in the direction shown in fig. 6B.

When the positioning pins 66, 66 come into contact with the outer peripheral edge 311 to which the

gripping pins

64, 64 are pressure-contacted, the displacement of the one gripping part 6A and the other gripping part 6B in the direction approaching each other is restricted. Then, the holding of the head 31 of the bolt 3 by the holding pins 64, 64 of the one holding part 6A and the holding pins 64, 64 of the other holding part 6B is hindered by the positioning pins 66, 66. To prevent such a situation from occurring, the center-to-center distance D1 is set.

Next, the holding of the bolt 3 by the hand 4 will be described.

Fig. 7A to 7D and fig. 8 are views for explaining a process of holding the bolt 3 with the hand 4.

Fig. 7A is a diagram showing a state in which the

grip portions

6A and 6B of the hand 4 are displaced in a direction approaching the reference line Cz in order to grip the bolt 3. Fig. 7B is a cross-sectional view taken along VIIb-VIIb in fig. 7A, and is a view illustrating a positional relationship between the head 31 of the bolt 3, the holding pin 64, and the positioning pin 66.

Fig. 7C is a diagram showing a state in which the

grip portions

6A and 6B reach positions at which the grip pins 64 and 64 contact the head 31 of the bolt 3. Fig. 7D is a diagram illustrating the positional relationship among the head 31 of the bolt 3, the gripping pin 64, and the positioning pin 66 when the gripping

portions

6A and 6B reach the positions shown in fig. 7C.

First, the

movable portions

45A and 45B are spaced (separated) in the direction of the axis Cx, and the

grip portions

6A and 6B are disposed at a distance that can accommodate the head 31 of the bolt 3.

In this state, the robot arm 21 is operated to move the hand 4 to a position where the head 31 of the bolt 3 is disposed between the

grip portions

6A and 6B, and then the

grip portions

6A and 6B are displaced in a direction to approach each other (see fig. 7A and 7B).

Then, the movement of the

gripping portions

6A and 6B causes the gripping

pins

64 and 64 of the

gripping portions

6A and 6B to approach and contact the head 31 of the bolt 3 (see fig. 7C and 7D).

Here, the members on the side of the

gripping portions

6A, 6B (gripping pins 64, positioning pins 66, 66) that first come into contact with the head 31 of the bolt 3 differ according to the phase of the bolt 3 around the reference line Cz.

Hereinafter, a case will be described, as an example, where the grip pins 64, 64 of the

grips

6A, 6B contact the corner 31a of the head 31 of the bolt 3, with the positional relationship shown in fig. 7D.

As shown in fig. 8 (a), when the holding pins 64, 64 of the holding

portions

6A, 6B contact the corner portion 31a of the bolt 3 from the axis Cx direction, the bolt 3 rotates about the reference line Cz by the pressing force applied to the head 31 from one of the holding pins 64, 64 and the other of the holding pins 64, 64.

The rotation direction of the bolt 3 is either clockwise or counterclockwise in fig. 8 (a) depending on the angular position of the bolt 3 about the reference line Cz.

When the bolt 3 is rotated in the clockwise direction (see fig. 8 b), the bolt 3 rotates the one outer periphery 311 and the other outer periphery 311 across the reference line Cz to angular positions orthogonal to the axis Cx (see fig. 8 c).

Thereby, the

outer peripheries

311, 311 of the bolt 3, which are parallel to each other, are gripped between the pair of

gripping pins

64, 64 of the one gripping part 6A and the pair of

gripping pins

64, 64 of the other gripping part 6B.

As described above, the center-to-center distance L64 between the

gripping pins

64, 64 in the direction of the axis Cy is set to a length shorter than the length L3 of one side of the linear outer periphery 311 of the head 31 of the bolt 3 (L3 > L64: see FIG. 6A)

Thus, when the head 31 of the bolt 3 is gripped between the

grip portions

6A, 6B in the orientation shown in fig. 6A and 8 (c), the pair of grip pins 64, 64 are pressed against the same outer periphery 311 of the head 31.

Here, the gripping

pins

64, 64 of the one gripping part 6A and the

gripping pins

64, 64 of the other gripping part 6B of the reference line Cz are pressed against the

outer peripheries

311, 311 arranged in parallel with each other with the axis Cy therebetween. As described above, in the grip portion 6 (6A, 6B), the center-to-center distance L64 of the grip pins 64, 64 is set to a length shorter than the length L3 of the outer periphery 311 of the head 31 of the bolt 3. Therefore, the head 31 of the bolt 3 is reliably gripped between the

gripping pins

64, 64 of the one gripping part 6A and the

gripping pins

64, 64 of the other gripping part 6B.

As described above, in the grip portion 6 (6A, 6B), the distance L66 between the positioning pins 66, 66 in the direction of the axis Cy is set to be longer than the length L3 of one side of the linear outer periphery 311 of the head 31 of the bolt 3 (L66 > L3: see FIG. 6A)

Therefore, when the head 31 of the bolt 3 is gripped between the

grip portions

6A, 6B in the orientation shown in fig. 6B and fig. 8 (c), the positioning pins 66, 66 abut on the outer periphery 311 adjacent to the outer periphery 311 pressed against the grip pins 64, 64. This regulates the displacement of the head 31 of the bolt 3 in the direction of the axis Cy.

Therefore, the bolt 3 is gripped between the one grip portion 6A and the other grip portion 6B in a state where the center axis C coincides with the reference line Cz.

When the bolt 3 is rotated counterclockwise from the state shown in fig. 8a (see fig. 8 d), the bolt 3 is rotated to an angular position on the axis Cx with the one corner portion 31a and the other corner portion 31a of the reference line Cz interposed therebetween, in accordance with the displacement of the

grip portions

6A and 6B in the direction of approaching each other (see fig. 8 e).

Thereby, the

outer peripheries

311, 311 adjacent to each other with the corner 31a of the bolt 3 interposed therebetween are pressed between the pair of

gripping pins

64, 64 of the one gripping part 6A and the pair of

gripping pins

64, 64 of the other gripping part 6B with the reference line Cz interposed therebetween.

As described above, the gripping

pins

64, 64 are provided in a symmetrical positional relationship with respect to the axis Cx.

Therefore, when the head 31 of the bolt 3 is oriented as shown in fig. 8 (e), the bolt 3 is reliably gripped between the pair of

gripping pins

64, 64 of the one gripping part 6A and the pair of

gripping pins

64, 64 of the other gripping part 6B in a state in which the rotation around the reference line Cz is restricted.

As described above, the pair of

gripping pins

64, 64 of the gripping portion 6 (6A, 6B) has a circular cross section. Therefore, regardless of the gripping form of the bolt 3 gripped by the gripping portion 6 (6A, 6B) as shown in fig. 8 (c) and (e), the pair of

gripping pins

64, 64 of the gripping portion 6 (6A, 6B) are in line contact with the outer periphery 311 of the head 31 of the bolt 3.

Therefore, the workpiece as the gripping target is not limited to the headed bolt as long as it has an outer periphery capable of line contact. In the case of bolts having different sizes of the head 31, since only the positions at which the

gripping pins

64, 64 contact are changed, even bolts having different sizes of the head 31 can be gripped by the same gripping portion 6 (6A, 6B).

Here, in fig. 8, a case where the reference line Cz of the hand 4 coincides with the central axis C of the bolt 3 is described as an example. When the bolt 3 is gripped by the hand 4, the reference line Cz of the hand 4 may not coincide with (slightly deviate from) the central axis C of the bolt 3.

Then, a process of holding the bolt 3 with the hand 4 in this case will be described below.

Fig. 9A to 9C are views for explaining a process of holding the bolt 3 with the hand 4 when the reference line Cz of the hand 4 does not coincide with the central axis C of the bolt 3.

As shown in fig. 9A, when the center axis C of the bolt 3 is offset in the radial direction of the axis Cx and does not coincide with the reference line Cz, the positioning pin 66 of the one grip 6A and the positioning pin 66 of the other grip 6B come into contact with the head 31 of the bolt 3 before the grip pins 64, 64.

In the case of fig. 9A, as the

grip portions

6A and 6B move in the direction approaching each other, the positioning pins 66 and 66 slide after contacting the outer

peripheral edges

311 and 311 of the bolt 3. Then, the bolt 3 is displaced in a direction (downward direction in the figure) in which the center axis C of the bolt 3 approaches the reference line Cz by the pressing force applied to the outer

peripheral edges

311, 311 from the positioning pins 66, 66 (see fig. 9B).

Then, the bolt 3 is finally displaced to a position where the center axis C of the bolt 3 coincides with the reference line Cz, and thereafter, is gripped between the pair of

gripping pins

64, 64 of the

gripping portions

6A, 6B (see fig. 9C).

Therefore, in the control when the hand 4 is moved to the target coordinates by the robot arm 21, strict control to the extent that the center axis C of the bolt 3 reliably coincides with the reference line Cz is not necessary.

The load in the control of the robot arm 21 and the cost required for the control can be reduced.

Fig. 10A and 10B are diagrams illustrating modifications of the grip portion, and fig. 10A is a diagram illustrating grip portions 6A 'and 6B' according to the modifications. Fig. 10B is a diagram illustrating the grip portions 6A ″ and 6B ″ according to a modification.

In the above embodiment, the case where the grip portion 6 (6A, 6B) includes the pair of grip pins 64, 64 and the pair of positioning pins 66, 66 has been described as an example.

The pair of positioning pins 66, 66 need not be provided on both the

grip portions

6A, 6B, and may be provided on at least one

grip portion

6A, 6B.

In the case of fig. 10A, the grip portion 6A 'and the grip portion 6B' each have one positioning pin 66. The positioning pin 66 of the first grip portion 6A 'and the positioning pin 66 of the second grip portion 6B' are provided in a positional relationship shifted by 180 ° in phase in the circumferential direction around the reference line Cz on one side (upper side in fig. 10A) and the other side (lower side in fig. 10A) of the axis Cx.

Even in the case of the grip portion 6A 'and the grip portion 6B', when the head 31 of the bolt 3 is gripped between the pair of grip pins 64, 64 of the grip portion 6A 'and the pair of grip pins 64, 64 of the grip portion 6B', the movement of the bolt 3 in the direction of the axis Cy can be reliably restricted by the positioning pins 66, 66.

In the case of fig. 10B, only one of the grip portions 6A' has a pair of positioning pins 66, 66.

Even in the case of the side portion of the grip portion 6A ″ and the side portion of the grip portion 6B ″, when the head 31 of the bolt 3 is gripped between the pair of grip pins 64, 64 of the grip portion 6A ″ and the pair of grip pins 64, 64 of the grip portion 6B ″, the movement of the bolt 3 in the direction of the axis Cy can be regulated by the positioning pins 66, 66.

In the above-described embodiment, the case where the grip part 6A and the grip part 6B arranged at intervals in the direction of the axis Cx are moved relative to each other at the same distance from the reference line Cz (axis Cy) has been exemplified.

As long as the bolt 3 can be gripped with the center axis C of the bolt 3 aligned with the reference line Cz, the positioning mechanism may be configured to displace only one of the grip portion 6A and the grip portion 6B in the direction of the axis Cx.

As described above, the workpiece gripping mechanism of the present embodiment has the following configuration.

(1) The workpiece holding mechanism 1 includes:

a grip portion 6A (first grip portion) having a pair of grip pins 64, 64 parallel to each other;

the grip portion 6B (second grip portion) has a pair of grip pins 64 and 64 (see fig. 3) parallel to each other.

The grip portion 6A and the grip portion 6B are provided so as to be relatively displaceable on the common axis Cx.

The pair of

gripping pins

64, 64 of the gripping portion 6A and the pair of

gripping pins

64, 64 of the gripping portion 6B are arranged at intervals in the direction of the axis Cy orthogonal to the axis Cx.

The bolt 3 (workpiece) is gripped by the pair of

gripping pins

64, 64 of the gripping portion 6A and the pair of

gripping pins

64, 64 of the gripping portion 6B.

With this configuration, since the bolt 3 is gripped by the pressure contact force of the pair of

gripping pins

64 and 64 of the gripping portion 6A and the pair of

gripping pins

64 and 64 of the gripping portion 6B, it is not necessary to align the phases of the bolt 3 and the

gripping pins

64 and 64 when gripping the bolt 3. Therefore, the bolt 3 can be gripped more easily.

The workpiece holding mechanism of the present embodiment has the following configuration.

(2) The pair of

gripping pins

64, 64 of the gripping portion 6A and the pair of

gripping pins

64, 64 of the gripping portion 6B are provided in parallel with a reference line Cz orthogonal to the axis Cx and the axis Cy, respectively.

The pair of

gripping pins

64, 64 of the gripping portion 6A and the pair of

gripping pins

64, 64 of the gripping portion 6B are provided at the same interval from the axis Cx when viewed in the axial direction of the reference line Cz.

With this configuration, the pair of

gripping pins

64, 64 of the gripping portion 6A are provided in a symmetrical positional relationship with the axis Cx therebetween, and the pair of

gripping pins

64, 64 of the gripping portion 6B are provided in a symmetrical positional relationship with the axis Cx therebetween.

Therefore, the bolt 3 is gripped by the pair of

gripping pins

64, 64 on the one side and the pair of

gripping pins

64, 64 on the other side, which are in line contact with the bolt 3.

Therefore, if the holding pins 64 and 64 have a shape that can secure a region in which they are in line contact, the bolt 3 can be easily held without being affected by the difference in the overall shape of the bolt 3.

The workpiece gripping mechanism of the present embodiment has the following configuration.

(3) The bolt 3 has a head 31 as an abutment portion, and a pair of holding

pins

64, 64 abut on the outer periphery of the head 31.

The head 31 has a regular polygonal shape that continuously connects a plurality of linear outer peripheries 311 in a circumferential direction around the central axis C, as viewed from the central axis C direction of the bolt 3.

The head 31 has a regular hexagonal shape having three sets of

outer peripheries

311, 311 parallel to each other with the center axis C therebetween, as viewed from the direction of the center axis C of the bolt 3.

The pair of

gripping pins

64, 64 are arranged at intervals in the direction of the axis Cy orthogonal to the axis Cx,

the distance between the pair of gripping pins 64 and 64 (center-to-center distance L64) is set to be shorter than the length L3 of the outer periphery 311 viewed from the center axis C direction of the bolt 3.

With this configuration, the

outer peripheries

311, 311 of the head 31 of the bolt 3, which are parallel to each other, can be appropriately gripped by the pair of

gripping pins

64, 64 of the gripping portion 6A and the pair of

gripping pins

64, 64 of the gripping portion 6B.

(4) The positioning pins 66, 66 that regulate movement of the bolt 3 in the direction orthogonal to the axis Cx (the direction of the axis Cy) are positioned on one side and the other side of the axis Cx when viewed in the axial direction of the reference line Cz (see fig. 3).

With this configuration, when the bolt 3 is gripped by the pair of gripping pins 64, the bolt 3 can be prevented from being displaced in the direction of the axis Cy.

(5) Positioning pin 66 on one side and positioning pin 66 on the other side are provided at the same interval from axis Cx.

One positioning pin 66 and the other positioning pin 66 are arranged at an interval in a direction (direction of axis Cy) orthogonal to axis Cx, which is longer than a length (interval distance L66) of one side (outer periphery 311) of regular hexagonal head 31 as viewed from direction of central axis C of bolt 3.

With this configuration, when the bolt 3 is gripped by the pair of gripping pins 64, the positional displacement of the bolt 3 in the direction of the axis Cy can be reliably prevented.

(6) One positioning pin 66 is provided on the grip portion 6A' (first grip portion),

the positioning pin 66 on the other side is provided on the grip portion 6B' (second grip portion).

With this configuration, the positional displacement of bolt 3 in the direction of axis Cy can be prevented by the minimum number of positioning pins 66.

(7) The positioning pin 66 on one side and the positioning pin 66 on the other side are provided on one or both of the grip portion 6A (first grip portion) and the grip portion 6B (second grip portion).

Even if one positioning pin 66 and the other positioning pin 66 are provided on the same grip portion 6A or grip portion 6B, or both

grip portions

6A and 6B, it is possible to prevent the bolt 3 from being displaced in the direction of the axis Cy.

(8) The positioning pin 66 of the one grip portion 6A and the positioning pin 66 of the other grip portion 6B are positioned closer to the reference line Cz than the pair of grip pins 64 and 64 of the grip portion 6A and the pair of grip pins 64 and 64 of the grip portion 6B, respectively, when viewed in the axial direction of the reference line Cz.

With this configuration, even when the position of the center axis C of the bolt 3 and the reference line Cz is displaced, the displacement can be corrected by the positioning pin 66.

The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above. The present invention can be modified as appropriate within the scope of the technical idea of the present invention.

The present invention is claimed to be based on the priority of Japanese patent application No. 2020-32367, filed on the sun in the office on 2/27/2020, the entire content of which is incorporated by reference in the present specification.

Claims

1. A workpiece holding mechanism includes:

a first gripping section having a pair of gripping pins parallel to each other;

a second holding part having a pair of holding pins parallel to each other,

2. The workpiece holding mechanism of claim 1,

the pair of gripping pins of the first gripping part and the pair of gripping pins of the second gripping part are provided in parallel with respect to a reference line orthogonal to the axis,

the pair of gripping pins of the first gripping section and the pair of gripping pins of the second gripping section are provided at the same interval from the axis line when viewed in the axial direction of the reference line.

3. The workpiece holding mechanism of claim 2,

the workpiece has an abutting portion at which the pair of gripping pins abuts against the outer periphery,

the contact portion is formed in a regular polygon shape having outer peripheries parallel to each other with the central axis therebetween when viewed in the direction of the central axis of the workpiece,

the pair of holding pins are arranged at an interval in a direction orthogonal to the axis,

the distance between the pair of gripping pins is set to be shorter than the length of the outer periphery as viewed from the central axis direction of the workpiece.

4. The workpiece holding mechanism of claim 3,

positioning pins that restrict movement of the workpiece in a direction orthogonal to the axis are located on one side and the other side of the axis, as viewed in the axial direction of the reference line.

5. The workpiece holding mechanism of claim 4,

the positioning pin on the one side and the positioning pin on the other side are provided at the same interval from the axis, and are arranged at an interval longer than one side of the regular polygonal shaped contact portion viewed from the central axis direction of the workpiece in a direction orthogonal to the axis.

6. The workpiece holding mechanism of claim 5,

the positioning pin on one side is arranged on the first holding part,

the positioning pin on the other side is arranged on the second holding part.

7. The workpiece holding mechanism of claim 5,

the positioning pin on one side and the positioning pin on the other side are provided in one or both of the first holding portion and the second holding portion.

8. The workpiece holding mechanism according to any one of claims 4 to 7,

the positioning pin on the one side and the positioning pin on the other side are located on the reference line side than the pair of gripping pins as viewed in the axial direction of the reference line.