Workpiece holding mechanism

Abstract

The workpiece holding mechanism comprises: a first holding portion having a pair of holding pins parallel to each other; and a second holding portion having a pair of holding pins parallel to each other. The first holding portion and the second holding portion are arranged to be relatively displaceable on a common axis. The workpiece holding mechanism holds the workpiece using the pair of holding pins of the first holding portion and the pair of holding pins of the second holding portion.

Description

Technical Field

[0001] The invention relates to a workpiece holding mechanism. Background Art

[0002] JP2003-211384A discloses a robot hand for use in screw tightening operations.

[0003] The robot hand of JP2003-211384A has a socket fitted on the head of a screw, and rotates the socket fitted on the head of the screw around the central axis of the screw to rotate the socket and the screw together, thereby screwing the screw into and fastening it to a counterpart component.

[0004] The socket of JP2003-211384A has a fitting hole formed at a portion facing the screw, and the socket is fitted onto the head of the screw by inserting the head of the screw into the fitting hole.

[0005] When viewed from the central axis of the screw, the general outer shape of the head of the screw is a polygon such as a hexagon. Therefore, the cross-sectional shape of the fitting hole viewed from the central axis of the screw is formed in the same shape as the outer shape of the head of the screw.

[0006] Here, when the socket is fitted onto the head of the screw, the socket and the screw need to be aligned in phase in the circumferential direction around the central axis.

[0007] If the time required for phase matching can be shortened or omitted, the screw tightening operation can be performed more efficiently, which is preferred. Summary of the invention

[0008] According to one embodiment of the present invention, there is provided a workpiece holding mechanism, the workpiece holding mechanism comprising:

[0009] A first holding portion having a pair of holding pins parallel to each other;

[0010] The second holding portion has a pair of holding pins parallel to each other,

[0011] The first holding portion and the second holding portion are arranged to be relatively displaceable on a common axis, wherein:

[0012] 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.

[0013] According to the above aspect, the time required for phase matching can be omitted, so the screw tightening work can be performed more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram illustrating a robot arm.

[0015] Figure 2A It is a figure explaining the bolt which is a grasping target object.

[0016] Figure 2B It is a figure explaining the bolt which is a grasping target object.

[0017] Figure 3A This is a diagram illustrating the hands.

[0018] Figure 3B This is a diagram illustrating the hands.

[0019] Figure 4A This is a diagram illustrating the hands.

[0020] Figure 4B This is a diagram illustrating the hands.

[0021] Figure 5A This is a diagram for explaining a grip portion.

[0022] Figure 5B This is a diagram for explaining a grip portion.

[0023] Figure 5C This is a diagram for explaining a grip portion.

[0024] Figure 5D This is a diagram for explaining a grip portion.

[0025] Fig. 6A This is a diagram for explaining a grip portion.

[0026] Figure 6B This is a diagram for explaining a grip portion.

[0027] Fig. 7A This is a diagram for explaining the process of holding the bolt by hand.

[0028] Figure 7B This is a diagram for explaining the process of holding the bolt by hand.

[0029] Figure 7C This is a diagram for explaining the process of holding the bolt by hand.

[0030] Fig.7D This is a diagram for explaining the process of holding the bolt by hand.

[0031] Figure 8 This is a diagram for explaining the process of holding the bolt by hand.

[0032] Fig. 9A This is a diagram for explaining the process of holding the bolt by hand.

[0033] Fig. 9B This is a diagram for explaining the process of holding the bolt by hand.

[0034] Fig. 9CThis is a diagram for explaining the process of holding the bolt by hand.

[0035] Fig. 10A It is a diagram for explaining a gripping portion according to a modified example.

[0036] Fig. 10B It is a diagram for explaining a gripping portion according to a modified example. DETAILED DESCRIPTION

[0037] Hereinafter, a case where the embodiment of the present invention is applied to a robot 2 that performs a tightening operation of a bolt 3 will be described as an example.

[0038] Figure 1 It is a diagram for explaining the robot arm 21.

[0039] Figure 2A This is a side view of bolt 3. Figure 2B is along Figure 2A A cross-sectional view of the head portion 31 of the bolt 3 taken along line IIb-IIb in FIG.

[0040] like Figure 1 As shown, the robot 2 includes a conventionally known multi-joint robot arm 21. The robot arm 21 is formed by connecting a plurality of arm members so as to be rotatable around eight rotation axes X1 to X8.

[0041] The base end portion of the robot arm 21 is rotatably provided on the base 20 about the rotation axis X1. The connection portion 25 connected to the hand 4 is rotatably provided on the front end portion of the robot arm 21 about the rotation axis X8.

[0042] The hand 4 is rotatable integrally with the connection portion 25 about the rotation axis X8.

[0043] In the present embodiment, the object (work) gripped by the hand 4 is a headed bolt 3 .

[0044] The robot arm 21 is driven by a control device (not shown) to place the bolt 3 held by the hand 4 at a desired position (coordinates) and then rotate the hand 4 around the rotation axis X8, thereby screwing the bolt 3 held by the hand 4 into and tightening it on the other side component.

[0045] like Figure 2A As shown, the bolt 3 has a head 31 with a larger diameter than the shaft 32 at one end of the shaft 32 .

[0046] like Figure 2B As shown, the head 31 of the bolt 3 has a regular polygonal shape in a cross section perpendicular to the central axis C of the bolt 3 .

[0047] In the present embodiment, the head 31 of the bolt 3 has a regular hexagonal cross section formed by continuously connecting a plurality of linear outer peripheral edges 311 in the circumferential direction around the central axis C. The lengths of the outer peripheral edges 311 of the head 31 are all the same length L3.

[0048] When viewed from the direction of the central axis C, the head 31 has three sets of outer peripheral edges 311 , 311 that are parallel to each other with the central axis C interposed therebetween. The head 31 of the bolt 3 is grasped by the hand 4 .

[0049] Figure 3A This is a front view of the hand 4 when the hand 4 is arranged in the orientation when grasping the bolt 3, and is a view showing a cross section with a part cut away. Figure 3B yes Figure 3A The IIIb-IIIb cross-sectional view in FIG. 1 is a view for explaining the arrangement of the holding pin 64 and the positioning pin 66 .

[0050] In the following description, when describing the positional relationship of the components of the hand 4, the Figure 3A The upper and lower sides of the configuration, one side and the other side based on the reference line Cz, Figure 3B The description will be made using terms such as one side and the other side based on the axis Cy.

[0051] like Figure 3A , Figure 3B As shown, the hand 4 has a workpiece holding mechanism 1 composed of a fixed portion 40 connected to the connecting portion 25, a pair of movable portions 45 (45A, 45B), and a holding portion 6 (6A, 6B) provided on the movable portion 45 (45A, 45B).

[0052] The fixing portion 40 has a columnar base member 41. The connection portion 25 of the robot arm 21 is connected to the base member 41 at a substantially central portion in the longitudinal direction of the base member 41.

[0053] Support wall portions 42 , 42 for supporting the movable portion 45 ( 45A, 45B) are provided at one end 41 a and the other end 41 b in the longitudinal direction of the base member 41 .

[0054] The support walls 42, 42 extend from the lower side surface 41d of the base member 41 in a direction away from the connection portion 25 ( Figure 3A The lower side of the middle portion extends.

[0055] The lower side surface 41 d is a side surface on the opposite side to the side surface 41 c to which the connection portion 25 is connected in the reference line Cz direction.

[0056] The supporting walls 42, 42 are arranged in a direction perpendicular to the base member 41. The supporting walls 42, 42 are arranged symmetrically on one side and the other side of the reference line Cz across the reference line Cz. The reference line Cz is a straight line passing through the center of the length direction of the base member 41 and perpendicular to the length direction of the base member 41, and is concentric with the rotation axis X8 of the above-mentioned connection part 25. The hand 4 rotates around the reference line Cz (rotation axis X8) in conjunction with the rotation of the connection part 25 of the robot arm 21.

[0057] 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 (axis Cx direction).

[0058] The through holes 420, 420 are located in the center of the width direction (axis Cy direction) of the support wall portion 42. The through holes 420, 420 are located in the length direction (axis Cy direction) of the support wall portion 42. Figure 3A They are arranged parallel to each other with a gap therebetween (in the up-down direction).

[0059] Here, the axis Cx is a straight line that is orthogonal to the reference line Cz and along the displacement direction of the movable part 45 (45A, 45B). The axis Cy is orthogonal to the reference line Cz and along the width direction ( Figure 3B A straight line in the up and down directions.

[0060] The reference line Cz and the axes Cx and Cy are orthogonal to each other.

[0061] The guide pins 46 , 46 of the movable portion 45 ( 45A, 45B) penetrate through the through holes 420 , 420 of the support wall portions 42 , 42 .

[0062] The movable portion 45 ( 45A, 45B) is provided on the support wall portions 42 , 42 so as to be movable in the axis Cx direction via guide pins 46 , 46 penetrating through the through holes 420 , 420 .

[0063] The movable portions 45A and 45B are provided at intervals on a common axis Cx along the longitudinal direction of the base member 41 .

[0064] In the front view, the movable portion 45A and the movable portion 45B are arranged on one side and the other side of the reference line Cz in a state where the distances from the reference line Cz are the same (see Figure 3A ). The movable part 45A and the movable part 45B can be relatively displaced in the direction of the axis Cx by a driving mechanism (not shown) while being at the same distance from the reference line Cz. Figure 3BAs shown, the movable portion 45A and the movable portion 45B are relatively displaceable in the direction of the axis Cx while the distances between them and the axis Cy perpendicular to the reference line Cz are the same.

[0065] The movable parts 45A and 45B include a plate-shaped base part 47 to which a pair of guide pins 46 and 46 are connected.

[0066] The base 47 is provided outside the support wall 42 in the axis Cx direction and parallel to the support wall 42. The base ends 46b, 46b of the pair of guide pins 46, 46 are inserted into support holes 471, 471 provided in the base 47.

[0067] The guide pins 46, 46 extend toward the reference line Cz from the side surface 47c on the support wall portion 42 side of the base portion 47. The front ends 46a, 46a of the guide pins 46, 46 reach above the gripping portions 6A, 6B.

[0068] The base 47 has a predetermined length L47 in the direction of the reference line Cz. Figure 3A The end portion 47a (lower side) is arranged at a position farther away from the base member 41 than the support wall portion 42.

[0069] Connecting beams 48, 48 extending toward the reference line Cz are fixed to the end 47a side of the base 47. The connecting beams 48, 48 are provided on both sides of the width direction (axis Cy direction) of the base 47 and are provided in parallel with each other in a symmetrical positional relationship with the axis Cx interposed therebetween (see Figure 3B ).

[0070] like Figure 3A As shown, the connecting beams 48, 48 extending from the base 47 are parallel to the guide pins 46, 46. The connecting beams 48, 48 extend toward the reference line Cz side at a position to avoid interference with the support wall 42. The gripping parts 6A, 6B for gripping the bolt 3 are fixed to the front ends 48a, 48a of the connecting beams 48, 48 by bolts B1, B3 with hexagonal holes.

[0071] Figure 4A It is a perspective view of the movable portion 45 (45A, 45B), and is a view showing the movable portion 45A on one side and the movable portion 45B on the other side separately. Figure 4B It is an exploded perspective view of the grip portion 6A attached to the movable portion 45A.

[0072] Figure 5A It is a front view of the grip portion 6. Figure 5B is along Figure 5A A cross-sectional view of the gripping portion 6 taken along the line Vb-Vb in FIG. Figure 5C It is along Figure 5A A cross-sectional view of the gripping portion 6 taken along the line Vc-Vc in FIG. Figure 5DIt is along Figure 5A The cross-sectional view of the holding portion 6 is cut along the Vd-Vd line in FIG. In addition, the holding portions 6A and 6B have the same structure, so Figure 5A The mark in the middle is the gripping portion 6.

[0073] like Figure 4A , Figure 4B As shown, the gripping parts 6A and 6B are composed of a gripping block 61 having a pair of gripping pins 64 and 64 and positioning blocks 65 and 65 having positioning pins 66 .

[0074] like Figure 5A , Figure 5B As shown, the holding block 61 is provided with a support portion 611 for supporting the holding pins 64 , 64 at the center of a plate-shaped base portion 610 .

[0075] The length direction of the side surface 610a of the base 610 in the thickness direction ( Figure 5B The areas on both end sides (in the left-right direction) of the base 610 become the bonding surfaces with the connecting beams 48, 48. Furthermore, the areas on both end sides in the length direction of the other side surface 610b in the thickness direction of the base 610 become the bonding surfaces with the positioning blocks 65, 65. The bonding surfaces with the connecting beams 48, 48 and the bonding surfaces with the positioning blocks 65, 65 are flat surfaces parallel to each other.

[0076] The positioning blocks 65 , 65 are press-fitted to the side surface 610 b of the base 610 by the fastening force of the bolts B3 , B3 penetrating the positioning blocks 65 , 65 and the base 610 .

[0077] The base portion 610 of the gripping block 61 is fixed to the front ends 48 a and 48 a of the connecting beams 48 and 48 by bolts B1 and B3 penetrating through the regions on both end sides in the longitudinal direction.

[0078] like Figure 5D As shown, the positioning block 65 is formed in a rectangular parallelepiped shape, and one side edge 65c in the reference line Cz direction is provided flush with the side edge 61c of the gripping 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 gripping block 61 to allow the bolt B1 to be disposed.

[0079] A cylindrical positioning pin 66 is fixed to the side edge 65c of the positioning block 65. The positioning pin 66 protrudes downward from the side edge 65c of the positioning block 65.

[0080] like Figure 5B As shown, the support portion 611 extends between the positioning blocks 65 , 65 in a direction away from the connecting beam 48 .

[0081] like Figure 5CAs shown in FIG. 1 , the end surface 65 a of the positioning block 65 is disposed at a position away from the connection beam 48 by a predetermined distance L1 compared to the end surface 61 a of the holding block 61 .

[0082] A support hole 612 for inserting a cylindrical holding pin 64 is provided on the lower side edge 61c of the support portion 611. A bolt B2 penetrating the support portion 611 is screwed into the upper end of the holding pin 64, and the holding pin 64 is prevented from falling off from the support portion 611 by the bolt B2.

[0083] like Figure 5A As shown, in the support portion 611 , the holding pins 64 are symmetrically arranged with respect to the reference line Cz.

[0084] The protruding height h1 of the holding pin 64 protruding from the lower side edge 61 c of the holding block 61 is the same as the protruding height h1 of the positioning pin 66 protruding from the lower side edge 65 c of the positioning block 65 .

[0085] The holding pin 64 and the positioning pin 66 are provided parallel to each other in the direction along the reference line Cz.

[0086] Fig. 6A yes Figure 3B The enlarged view of the region B in FIG. 1 is a view showing the gripping state of the head portion 31 of the bolt 3 . Figure 6B 3 is a diagram showing another holding mode of the head 31 of the bolt 3. Fig. 6A , Figure 6B , the position of the outer peripheral edge 311 of the head 31 of the bolt 3 is indicated by an imaginary line.

[0087] like Fig. 6A , Figure 6B As shown, the holding pins 64, 64 are located on an axis Cy1 parallel to the axis Cy orthogonal to the reference line Cz.

[0088] The holding pins 64 , 64 have a circular cross section, and the centers of the holding pins 64 , 64 are located on the axis Cy1 .

[0089] The gripping pins 64 , 64 are provided in a symmetrical positional relationship with respect to the axis line Cx that is orthogonal to the reference line Cz and the axis line Cy.

[0090] The center-to-center distance L64 of the holding pins 64 and 64 in the axis Cy direction is set to be shorter than the length L3 of one side of the linear outer peripheral edge 311 of the head 31 of the bolt 3 (L3>L64).

[0091] Thus, when the head 31 of the bolt 3 is Fig. 6A When held between the holding portions 6A, 6B in the orientation shown, the pair of holding pins 64, 64 are pressed against the same outer periphery 311 of the head portion 31.

[0092] Here, the holding pins 64, 64 of the holding portion 6A on one side of the reference line Cz and the holding pins 64, 64 of the holding portion 6B on the other side are respectively pressed against the outer peripheries 311, 311 which are parallel to each other across the axis Cy. As described above, the center-to-center distance L64 of the holding 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 held between the holding pins 64, 64 of the holding portion 6A on one side and the holding pins 64, 64 of the holding portion 6B on the other side.

[0093] In addition, the head 31 of the bolt 3 is Figure 6B When the bolt 3 is held between the holding portions 6A and 6B in the direction shown, the holding pins 64, 64 of the holding portion 6A on one side and the holding pins 64, 64 of the holding portion 6B on the other side are respectively pressed against the outer peripheral edges 311, 311 adjacent to each other across the corner portion 31a of the head portion 31, thereby restricting the movement of the bolt 3 in the direction of the axis Cx. Therefore, the head portion 31 of the bolt 3 is reliably held between the holding pins 64, 64 of the holding portion 6A on one side and the holding pins 64, 64 of the holding portion 6B on the other side.

[0094] The positioning pins 66 , 66 are located on an axis Cy2 parallel to the axis Cy orthogonal to the reference line Cz.

[0095] The positioning pins 66 , 66 have a circular cross-section, and the centers of the positioning pins 66 , 66 are located on the axis Cy2 .

[0096] The axis line Cy2 is located on the axis line Cy side relative to the axis line Cy1.

[0097] The positioning pins 66 , 66 are provided in a symmetrical positional relationship with respect to the axis line Cx perpendicular to the reference line Cz and the axis line Cy.

[0098] The spacing distance L66 between the positioning pins 66 and 66 in the axis Cy direction is set to be longer than the length L3 of one side of the linear outer peripheral edge 311 of the head 31 of the bolt 3 (L66>L3).

[0099] In this embodiment, the spacing distance L66 is set to be such that when the head 31 of the bolt 3 is Fig. 6A When held between the holding parts 6A and 6B in the direction shown, the positioning pins 66 and 66 abut against the outer periphery 311 adjacent to the outer periphery 311 pressed against the holding pins 64 and 64. This is to restrict the positional deviation of the head 31 of the bolt 3 in the axis Cy direction.

[0100] Furthermore, the center distance D1 between the positioning pin 66 and the holding pin 64 in the axis Cx direction is set so that the head 31 of the bolt 3 is Figure 6BWhen held between the holding portions 6A, 6B in the orientation shown, the positioning pins 66, 66 do not contact the outer periphery 311 of the holding pins 64, 64 which are pressed against each other.

[0101] When the positioning pins 66, 66 contact the outer periphery 311 of the holding pins 64, 64, the displacement of the holding portion 6A on one side and the holding portion 6B on the other side in the direction of approaching each other is restricted. As a result, the holding pins 64, 64 of the holding portion 6A on one side and the holding pins 64, 64 of the holding portion 6B on the other side are blocked from holding the head 31 of the bolt 3 by the positioning pins 66, 66. In order to prevent such a situation from occurring, the center-to-center distance D1 is set.

[0102] Next, the gripping of the bolt 3 by the hand 4 will be described.

[0103] Figures 7A to 7D and Figure 8 This is a diagram for explaining a process of gripping the bolt 3 with the hand 4 .

[0104] Fig. 7A This is a diagram showing a state in which the gripping parts 6A and 6B of the hand 4 are displaced in a direction approaching the reference line Cz in order to grip the bolt 3 . Figure 7B yes Fig. 7A The VIIb-VIIb cross-sectional view in FIG. 1 is a view for explaining the positional relationship between the head 31 of the bolt 3 , the holding pin 64 , and the positioning pin 66 .

[0105] Figure 7C This is a diagram showing a state where the gripping parts 6A, 6B have reached a position where the gripping pins 64, 64 are in contact with the head 31 of the bolt 3. Fig.7D This means that the gripping parts 6A and 6B have reached Figure 7C FIG. 2 is a diagram showing the positional relationship between the head 31 of the bolt 3 , the holding pin 64 , and the positioning pin 66 in the position shown.

[0106] First, the movable portions 45A and 45B are spaced apart (separated) in the direction of the axis Cx to leave a gap that can accommodate the head portion 31 of the bolt 3, and the gripping portions 6A and 6B are arranged.

[0107] 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 arranged between the gripping parts 6A and 6B, and then the gripping parts 6A and 6B are displaced in a direction toward each other (see Fig. 7A , Figure 7B ).

[0108] Then, by the movement of the holding parts 6A and 6B, the holding pins 64 and 64 of the holding parts 6A and 6B approach and contact the head 31 of the bolt 3 (see Figure 7C , Fig.7D ).

[0109] Here, depending on the phase of the bolt 3 around the reference line Cz, the components on the gripping portions 6A and 6B side (gripping pins 64 and 64 and positioning pins 66 and 66 ) that first come into contact with the head 31 of the bolt 3 differ.

[0110] Below, with Fig.7D The positional relationship shown in the figure is described by taking as an example the case where the holding pins 64 , 64 of the holding parts 6A, 6B are in contact with the corner portion 31 a of the head portion 31 of the bolt 3 .

[0111] like Figure 8 As shown in (a), when the holding pins 64, 64 of the holding parts 6A, 6B contact the corner 31a of the bolt 3 from the axis Cx direction, the bolt 3 rotates around the reference line Cz due to the pressing force acting on the head 31 from the holding pins 64, 64 on one side and the holding pins 64, 64 on the other side.

[0112] According to the angular position of bolt 3 around the reference line Cz, the rotation direction of bolt 3 is Figure 8 (a) in the clockwise or counterclockwise direction.

[0113] When the bolt 3 is rotated clockwise (refer to Figure 8 (b)), the bolt 3 rotates one outer periphery 311 and the other outer periphery 311 across the reference line Cz to an angular position orthogonal to the axis Cx (refer to Figure 8 (c)).

[0114] Thus, the mutually parallel outer peripheral edges 311 , 311 of the bolt 3 are gripped between the pair of gripping pins 64 , 64 of the gripping portion 6A on one side and the pair of gripping pins 64 , 64 of the gripping portion 6B on the other side.

[0115] As described above, the center distance L64 of the holding pins 64, 64 in the axis Cy direction is set to be shorter than the length L3 of one side of the linear outer peripheral edge 311 of the head 31 of the bolt 3 (L3>L64: see Fig. 6A )

[0116] Thus, when the head 31 of the bolt 3 is Fig. 6A and Figure 8 When the head 31 is held between the holding portions 6A and 6B in the orientation shown in (c), the pair of holding pins 64 and 64 are pressed against the same outer peripheral edge 311 of the head 31 .

[0117] Here, the holding pins 64, 64 of the holding portion 6A on one side of the reference line Cz and the holding pins 64, 64 of the holding portion 6B on the other side are pressed against the outer peripheries 311, 311 arranged parallel to each other across the axis Cy. As described above, in the holding portion 6 (6A, 6B), the center-to-center distance L64 of the holding 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 held between the holding pins 64, 64 of the holding portion 6A on one side and the holding pins 64, 64 of the holding portion 6B on the other side.

[0118] As described above, in the gripping portion 6 (6A, 6B), the spacing (distance) L66 between the positioning pins 66, 66 in the axis Cy direction 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: refer to Fig. 6A )

[0119] Therefore, the head 31 of the bolt 3 is Figure 6B and Figure 8 When the bolt 3 is held between the holding portions 6A and 6B in the orientation shown in (c), the positioning pins 66 and 66 abut against the outer periphery 311 adjacent to the outer periphery 311 pressed against the holding pins 64 and 64. Thus, the positional deviation of the head 31 of the bolt 3 in the direction of the axis Cy is restricted.

[0120] Therefore, the bolt 3 is held between the holding portion 6A on one side and the holding portion 6B on the other side in a state where the central axis C is aligned with the reference line Cz.

[0121] In addition, when bolt 3 is Figure 8 (a) When the state shown is rotated counterclockwise (refer to Figure 8 (d) As the gripping parts 6A and 6B move toward each other, the bolt 3 rotates to an angular position where one corner 31a and the other corner 31a are arranged on the axis Cx across the reference line Cz (see Figure 8 (e)).

[0122] Thus, the outer peripheral edges 311, 311 adjacent to each other across the corner 31a of the bolt 3 are pressed between the pair of holding pins 64, 64 of the holding portion 6A on one side and the pair of holding pins 64, 64 of the holding portion 6B on the other side across the reference line Cz.

[0123] As described above, the holding pins 64 , 64 are provided in a symmetrical positional relationship with respect to the axis Cx.

[0124] Therefore, when the head 31 of the bolt 3 becomes Figure 8In the orientation shown in (e), the bolt 3 is securely held between the pair of holding pins 64, 64 of the holding portion 6A on one side and the pair of holding pins 64, 64 of the holding portion 6B on the other side, with rotation about the reference line Cz being restricted.

[0125] As described above, the pair of holding pins 64, 64 of the holding portion 6 (6A, 6B) have a circular cross section. Therefore, regardless of the holding form of the bolt 3 held by the holding portion 6 (6A, 6B) Figure 8 In either of the modes shown in (c) and (e), the pair of holding pins 64 , 64 of the holding portion 6 ( 6A, 6B) are in line contact with the outer peripheral edge 311 of the head 31 of the bolt 3 .

[0126] Therefore, as long as the outer periphery has a line contactable outer periphery, the workpiece to be gripped is not limited to a bolt with a head. In addition, in the case of bolts with different sizes of the head 31, since only the contact position of the gripping pins 64, 64 is changed, even bolts with different sizes of the head 31 can be gripped using the same gripping portion 6 (6A, 6B).

[0127] Here, in Figure 8 In the description, the case where the reference line Cz of the hand 4 coincides with the center axis C of the bolt 3 is taken as an example. When the bolt 3 is grasped by the hand 4, the reference line Cz of the hand 4 may not coincide with the center axis C of the bolt 3 (slightly deviate).

[0128] Therefore, the process of holding the bolt 3 with the hand 4 in this case will be described below.

[0129] Figures 9A to 9C This is a diagram 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 .

[0130] like Fig. 9A As shown, when the center axis C of the bolt 3 is radially offset along the axis Cx and the center axis C is inconsistent with the reference line Cz, the positioning pin 66 of the holding portion 6A on one side and the positioning pin 66 of the holding portion 6B on the other side contact the head 31 of the bolt 3 before the holding pins 64, 64.

[0131] exist Fig. 9A In the case of the above, as the gripping parts 6A and 6B move toward each other, the positioning pins 66 and 66 come into contact with the outer peripheries 311 and 311 of the bolt 3 and then slide. Then, due to the pressing force from the positioning pins 66 and 66 acting on the outer peripheries 311 and 311, the bolt 3 is displaced in the direction (in the figure, downward direction) in which the central axis C of the bolt 3 approaches the reference line Cz (see FIG. Fig. 9B ).

[0132] Then, the bolt 3 is finally displaced to a position where the central axis C of the bolt 3 coincides with the reference line Cz, and is then held between a pair of holding pins 64, 64 of the holding portions 6A, 6B (see Fig. 9C ).

[0133] Therefore, in the control when the robot arm 21 moves the hand 4 to the target coordinates, strict control such as to reliably make the central axis C of the bolt 3 coincide with the reference line Cz is not required.

[0134] The load on the control of the robot arm 21 and the cost required for the control can be reduced.

[0135] Fig. 10A , Fig. 10B 2 is a diagram for explaining a modified example of the gripping portion. Fig. 10A It is a diagram for explaining gripping parts 6A' and 6B' according to a modified example. Fig. 10B It is a diagram for explaining gripping parts 6A" and 6B" according to a modified example.

[0136] In the above-described embodiment, the case where the gripping portion 6 ( 6A, 6B) includes a pair of gripping pins 64 , 64 and a pair of positioning pins 66 , 66 , respectively, has been described as an example.

[0137] The pair of positioning pins 66 , 66 does not necessarily need to be provided on both holding portions 6A, 6B, and may be provided on at least one of the holding portions 6A, 6B.

[0138] exist Fig. 10A In the case of, the holding portion 6A' and the holding portion 6B' each have one positioning pin 66. And the positioning pin 66 of one holding portion 6A' and the positioning pin 66 of the other holding portion 6B' are on one side of the axis Cx ( Fig. 10A The upper side of the Fig. 10A The lower side in the figure) is arranged with a positional relationship in which the phase is shifted by 180° in the circumferential direction around the reference line Cz.

[0139] Even in the case of the holding portion 6A' and the holding portion 6B', when the head 31 of the bolt 3 is held between the pair of holding pins 64, 64 of the holding portion 6A' and the pair of holding pins 64, 64 of the holding portion 6B', the positioning pins 66, 66 can be used to reliably limit the movement of the bolt 3 in the direction of the axis Cy.

[0140] exist Fig. 10B In the case of , only one holding portion 6A′ has a pair of positioning pins 66 , 66 .

[0141] Even in the case of the holding portion 6A" side and the holding portion 6B" side, when the head 31 of the bolt 3 is held between a pair of holding pins 64, 64 of the holding portion 6A" and a pair of holding pins 64, 64 of the holding portion 6B", the positioning pins 66, 66 can be used to limit the movement of the bolt 3 in the direction of the axis Cy.

[0142] In the above-described embodiment, an example is given in which the gripping portion 6A and the gripping portion 6B disposed at a distance in the axis Cx direction relatively move while the distance from the reference line Cz (axis Cy) is the same.

[0143] As long as the bolt 3 can be held 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 holding portion 6A and the holding portion 6B in the direction of the axis Cx.

[0144] As described above, the workpiece holding mechanism of the present embodiment has the following structure.

[0145] (1) The workpiece holding mechanism 1 has:

[0146] A holding portion 6A (first holding portion) having a pair of holding pins 64, 64 parallel to each other;

[0147] The gripping portion 6B (second gripping portion) includes a pair of gripping pins 64, 64 parallel to each other (see FIG. 3).

[0148] The grip portion 6A and the grip portion 6B are provided so as to be relatively displaceable on a common axis Cx.

[0149] 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 axis Cy direction orthogonal to the axis Cx.

[0150] The bolt 3 (workpiece) is gripped by a pair of gripping pins 64 , 64 of the gripping portion 6A and a pair of gripping pins 64 , 64 of the gripping portion 6B.

[0151] With this structure, since the bolt 3 is held by the pressing force of the pair of holding pins 64, 64 of the holding portion 6A and the pair of holding pins 64, 64 of the holding portion 6B, it is not necessary to match the phases of the bolt 3 and the holding pins 64, 64 when holding the bolt 3. Therefore, the bolt 3 can be held more easily.

[0152] The workpiece holding mechanism of this embodiment has the following structure.

[0153] (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 respectively provided parallel to the reference line Cz perpendicular to the axis Cx and the axis Cy.

[0154] 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.

[0155] With this configuration, the pair of gripping pins 64 , 64 of the gripping portion 6A are provided in a symmetrical positional relationship with respect to the axis Cx, and the pair of gripping pins 64 , 64 of the gripping portion 6B are provided in a symmetrical positional relationship with respect to the axis Cx.

[0156] Therefore, the bolt 3 is held by the pair of holding pins 64 , 64 on one side that is in line contact with the bolt 3 and the pair of holding pins 64 , 64 on the other side.

[0157] Therefore, as long as the shape can ensure the area where the holding pins 64 and 64 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.

[0158] The workpiece holding mechanism of this embodiment has the following structure.

[0159] (3) The bolt 3 has the head 31 as the abutment portion, and the pair of holding pins 64 , 64 abuts against the outer periphery of the head 31 .

[0160] When viewed from the center axis C direction of the bolt 3 , the head 31 has a regular polygonal shape in which a plurality of linear outer peripheral edges 311 are continuously connected in the circumferential direction around the center axis C.

[0161] When viewed from the center axis C of the bolt 3 , the head 31 has a regular hexagonal shape having three sets of outer peripheral edges 311 , 311 that are parallel to each other with the center axis C interposed therebetween.

[0162] The pair of holding pins 64, 64 are arranged at a distance from each other in the direction of the axis Cy orthogonal to the axis Cx.

[0163] The distance between the pair of holding pins 64 and 64 (center-to-center distance L64 ) is set to be shorter than the length L3 of the outer peripheral edge 311 as viewed in the direction of the center axis C of the bolt 3 .

[0164] According to this structure, the outer peripheral edges 311 , 311 of the head 31 of the bolt 3 that 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.

[0165] The workpiece holding mechanism of this embodiment has the following structure.

[0166] (4) When viewed from the axial direction of the reference line Cz, the positioning pins 66, 66 that restrict the movement of the bolt 3 in the direction perpendicular to the axis Cx (axis Cy direction) are located on one side and the other side of the axis Cx (see FIG. 3).

[0167] According to this structure, when the bolt 3 is gripped by the pair of gripping pins 64 , 64 , it is possible to prevent the bolt 3 from being displaced in the direction of the axis Cy.

[0168] The workpiece holding mechanism of this embodiment has the following structure.

[0169] (5) The positioning pin 66 on one side and the positioning pin 66 on the other side are provided at the same interval from the axis Cx.

[0170] The positioning pin 66 on one side and the positioning pin 66 on the other side are arranged to be spaced apart by a length (space distance L66) that is longer than one side (outer periphery 311) of the regular hexagonal head 31 viewed from the center axis C direction of the bolt 3 in the direction orthogonal to the axis Cx (axis Cy direction).

[0171] According to this structure, when the bolt 3 is gripped by the pair of gripping pins 64 , 64 , positional deviation of the bolt 3 in the direction of the axis Cy can be reliably prevented.

[0172] The workpiece holding mechanism of this embodiment has the following structure.

[0173] (6) The positioning pin 66 on one side is provided on the gripping portion 6A' (first gripping portion).

[0174] The other positioning pin 66 is provided on the gripping portion 6B' (second gripping portion).

[0175] According to this structure, the bolt 3 can be prevented from being displaced in the direction of the axis Cy by the minimum number of positioning pins 66 .

[0176] The workpiece holding mechanism of this embodiment has the following structure.

[0177] (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 gripping portion 6A (first gripping portion) and the gripping portion 6B (second gripping portion).

[0178] Regardless of whether the positioning pin 66 on one side and the positioning pin 66 on the other side are provided on the same holding portion 6A or holding portion 6B, or provided on both the holding portion 6A and the holding portion 6B, the positional deviation of the bolt 3 in the direction of the axis Cy can be prevented.

[0179] The workpiece holding mechanism of this embodiment has the following structure.

[0180] (8) When viewed from the axial direction of the reference line Cz, the positioning pin 66 of the holding portion 6A on one side and the positioning pin 66 of the holding portion 6B on the other side are respectively located closer to the reference line Cz than the pair of holding pins 64, 64 of the holding portion 6A and the pair of holding pins 64, 64 of the holding portion 6B.

[0181] According to this structure, even when the positions of the central axis C of the bolt 3 and the reference line Cz are offset, the offset can be corrected by the positioning pin 66 .

[0182] Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and can be appropriately modified within the scope of the technical concept of the invention.

[0183] The present invention claims priority based on Japanese Patent Application No. 2020-32367 filed with the Japan Patent Office on February 27, 2020, the entire contents of which are incorporated herein by reference.

Claims

1. A workpiece holding mechanism, comprising: A first holding portion having a pair of holding pins parallel to each other; The second holding portion has a pair of holding pins parallel to each other, The first holding portion and the second holding portion are arranged to be relatively displaceable on a common axis, wherein: The workpiece is gripped using the pair of gripping pins of the first gripping portion and the pair of gripping pins of the second gripping portion, When viewed from the axial direction of a reference line perpendicular to the axis, positioning pins for limiting the movement of the workpiece in a direction perpendicular to the axis are located on one side and the other side of the axis.

2. The workpiece holding mechanism according to claim 1, wherein: The pair of holding pins of the first holding portion and the pair of holding pins of the second holding portion are arranged parallel to the reference line. The pair of holding pins of the first holding portion and the pair of holding pins of the second holding portion are provided at the same interval from the axis when viewed in the axial direction of the reference line.

3. The workpiece holding mechanism according to claim 2, wherein: The workpiece has an abutment portion where the pair of holding pins abut against the outer periphery, When viewed from the center axis direction of the workpiece, the abutment portion is formed into a regular polygonal shape having outer circumferences parallel to each other with the center axis interposed therebetween. The pair of holding pins are arranged at intervals in a direction orthogonal to the axis. The spacing distance between the pair of holding pins is set to a length shorter than the length of the outer periphery viewed from the central axis direction of the workpiece.

4. The workpiece holding mechanism according to claim 3, wherein: The positioning pins on one side and the positioning pins on the other side are arranged at the same interval from the axis, and are arranged at an interval in a direction perpendicular to the axis by a length longer than one side of the regular polygonal abutment portion viewed from the center axis direction of the workpiece.

5. The workpiece holding mechanism according to claim 4, wherein: The positioning pin on one side is arranged on the first holding portion, The positioning pin on the other side is provided on the second holding portion.

6. The workpiece holding mechanism according to claim 4, wherein: The one side positioning pin and the other side positioning pin are provided in one or both of the first holding portion and the second holding portion.

7. The workpiece holding mechanism according to any one of claims 1 and 4 to 6, wherein: When viewed from the axial direction of the reference line, the positioning pin on one side and the positioning pin on the other side are located closer to the axis (Cy) in the direction orthogonal to the axis (Cx) at the reference line position than the pair of holding pins.

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