Compliance Unit

Abstract

To provide a compliance unit capable of tilting at a table with respect to a slide part and absorbing a tilt error.SOLUTION: A retainer 68 for holding a plurality of first balls is disposed between a slide body 38 constituting a slide part 30 and a base plate 62 constituting a table 54. The first balls are arrayed around an axis C1 of the slide part coincident with a Z axis. A single second ball 72 is disposed on the axis of the slide part between a ball support plate 42 constituting the slide part and a ball support plate 60 constituting the table.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a compliance unit that can hold a workpiece flexibly and absorb positioning errors in automatic assembly by a robot hand.

Background Art

[0002] Conventionally, a compliance unit has been used to impart flexibility to a workpiece held by a robot hand against an external action.

[0003] For example, Patent Document 1 describes a compliance unit in which a sliding member is disposed in a cylindrical body via a slide element, and a table is slidably disposed inside the sliding member via a planar slide element. The sliding member is movable in the Z direction with respect to the body, and the table is movable in the XY plane with respect to the sliding member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the above compliance unit, positioning errors in the XY plane and positioning errors in the Z direction can be absorbed. However, since the table cannot rotate about the X-axis and the Y-axis, errors due to inclination cannot be absorbed.

[0006] An object of the present invention is to solve the above-described problems.

Means for Solving the Problems

[0007] The present invention relates to a compliance unit comprising a body, a slide, and a table, wherein a retainer holding a plurality of first balls is disposed between the slide body constituting the slide and the base plate constituting the table, and the plurality of first balls are arranged around the axis of the slide, which coincides with the Z axis. A single second ball is disposed on the axis of the slide between the ball receiving plate constituting the slide and the ball receiving plate constituting the table. The table is movable in the XY plane relative to the slide, and the table is tiltable relative to the slide. [Effects of the Invention]

[0008] According to the compliance unit of the present invention, the table portion can be tilted relative to the slide portion, and errors in tilting can be absorbed. Furthermore, a compact configuration can be realized in which the table portion can move in the XY plane relative to the slide portion and the table portion can be tilted relative to the slide portion. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view of a compliance unit according to an embodiment of the present invention, when cut along a plane including the X and Z axes. [Figure 2] Figure 2 is a cross-sectional view of the compliance unit in Figure 1 when air is supplied to it. [Figure 3] Figure 3 is a cross-sectional view of the compliance unit in Figure 1 when a pressing force is applied to the table portion. [Figure 4] Figure 4 is a cross-sectional view of the compliance unit in Figure 1 when it absorbs errors in the X direction. [Figure 5] Figure 5 is a cross-sectional view of the compliance unit in Figure 1 when it absorbs errors with respect to the slope. [Figure 6] Figure 6 is an external view of the compliance unit shown in Figure 1. [Figure 7]Figure 7 is a partial cross-sectional view of the compliance unit in Figure 1, obtained by cutting it in a plane that includes the Z-axis but does not include the X-axis. [Figure 8] Figure 8 shows the relationship between the regulating pin on the body and the notched groove on the table body. [Modes for carrying out the invention]

[0010] As shown in Figure 1, a compliance unit 10 according to an embodiment of the present invention includes a body portion 12, a slide portion 30 supported by the body portion 12, and a table portion 54 supported by the slide portion 30. The body portion 12 is attached to a robot hand (not shown). The axis C1 of the body portion 12 and the slide portion 30 coincides with the Z-axis. The slide portion 30 is movable in the Z-direction relative to the body portion 12.

[0011] The table section 54 is movable relative to the slide section 30 in the X and Y directions (directions perpendicular to the plane of the paper), and is rotatable around the axis C1 (Z-axis) of the slide section 30. In other words, the table section 54 is movable relative to the slide section 30 in the XY plane. Furthermore, the table section 54 is tiltable relative to the slide section 30. In other words, the table section 54 is rotatable around the X-axis and the Y-axis. Hereafter, when terms relating to the up and down directions are used, they refer to the direction parallel to the Z-axis. Similarly, when terms relating to the left and right directions are used, they refer to the direction parallel to the X-axis.

[0012] The body portion 12 consists of a cylindrical housing 14, a rectangular cover plate 16, a disc-shaped pressure plate 22, and an annular end plate 26. The cover plate 16 is fixed to the upper part of the housing 14. The pressure plate 22 is fixed to the lower center of the cover plate 16. The end plate 26 is fixed to the lower part of the housing 14. The cover plate 16 has an annular recess 16a on its lower surface, and the pressure plate 22 has an annular fitting portion 22a on its upper surface. The fitting portion 22a of the pressure plate 22 fits into the inner circumference of the recess 16a of the cover plate 16.

[0013] The slide portion 30 is housed inside the body portion 12. The slide portion 30 consists of a bottomed cylindrical cylinder body 32, a cylindrical slide body 38, and a circular ball bearing plate 42. The upper surface of the cylinder body 32 can abut against the bottom surface of the recess 16a of the cover plate 16. The slide body 38 has a thickened portion 38a, a fitting portion 38b extending upward from the upper surface of the thickened portion 38a, and a flange portion 38c protruding radially inward from the lower part of the thickened portion 38a. The fitting portion 38b of the slide body 38 is press-fitted to the outside of the cylinder body 32. The ball bearing plate 42 is sandwiched between the lower surface of the cylinder body 32 and the upper surface of the thickened portion 38a of the slide body 38.

[0014] A cylindrical first retainer 44 is positioned between the inner surface of the housing 14 and the outer surface of the slide body 38. The first retainer 44 has a plurality of upper ball housing holes 44a and a plurality of lower ball housing holes 44b arranged in the circumferential direction. The upper ball housing holes 44a and the lower ball housing holes 44b penetrate radially through the wall surface of the first retainer 44. Guide balls 46 are positioned in the upper ball housing holes 44a and the lower ball housing holes 44b, and the first retainer 44 holds a plurality of guide balls 46. The diameter of the guide balls 46 is slightly larger than the wall thickness of the first retainer 44.

[0015] The guide ball 46 contacts the inner circumferential surface of the housing 14 and the outer circumferential surface of the slide body 38. Multiple first springs 48 that bias the first retainer 44 downward are arranged between the first retainer 44 and the cover plate 16. Multiple second springs 50 that bias the first retainer 44 upward are arranged between the first retainer 44 and the end plate 26. The first retainer 44 is held in a position separated from the cover plate 16 and the end plate 26, respectively, by the biasing forces of the first springs 48 and the second springs 50.

[0016] As the guide ball 46 rolls on the inner peripheral surface of the housing 14 and the outer peripheral surface of the slide body 38, the slide portion 30 can smoothly move in the Z direction with respect to the body portion 12. When the slide portion 30 moves with respect to the body portion 12 while the guide ball 46 rolls on the inner peripheral surface of the housing 14 and the outer peripheral surface of the slide body 38, the first retainer 44 also moves in the same direction.

[0017] The distance from the upper surface of the cylinder body 32 to the lower surface of the slide body 38 (the height of the slide portion 30) is shorter by L1 than the distance from the bottom surface of the recess 16a of the cover plate 16 to the upper surface of the end plate 26 (the height of the internal space of the body portion 12). The maximum movement amount in the Z direction of the table portion 54 with respect to the slide portion 30 is equal to L1. A slide portion biasing spring 52 that biases the slide portion 30 upward with respect to the body portion 12 is disposed between the end plate 26 and the slide body 38 (see FIG. 7).

[0018] The pressure plate 22 enters inside the cylinder body 32. A cylindrical packing 36 is attached to the outer periphery of the pressure plate 22. The upper surface of the packing 36 is in close contact with the lower surface of the cover plate 16, and the outer peripheral surface of the packing 36 is in sliding contact with the inner peripheral surface of the cylinder body 32. A pressure chamber 34 that is hermetically held from the outside is formed between the pressure plate 22 and the cylinder body 32.

[0019] The cover plate 16 has a supply / discharge port 18 connected to an air supply source (not shown) and an air passage 20 extending from the supply / discharge port 18. The end of the air passage 20 of the cover plate 16 opens to the lower surface of the cover plate 16. The pressure plate 22 has an air passage 24 penetrating in the vertical direction at the center. The air passage 24 of the pressure plate 22 is connected to the air passage 20 of the cover plate 16 at the upper end and is connected to the pressure chamber 34 at the lower end.

[0020] When air is supplied to the pressure chamber 34 through the supply and discharge port 18 of the cover plate 16, the slide portion 30 is biased downward. This biasing force counteracts the biasing force of the slide portion biasing spring 52, as well as the external force acting on the table portion 54. By adjusting the air pressure supplied to the pressure chamber 34, the pressing force of the table portion 54 can be controlled, and the desired buffering effect can be obtained.

[0021] The slide body 38 is provided with a regulating pin 28 that protrudes downward from the lower surface of the slide body 38. The end plate 26 has a regulating hole 26a at a position corresponding to the regulating pin 28 of the slide body 38. The regulating pin 28 of the slide body 38 engages with the regulating hole 26a of the end plate 26. This restricts the rotation of the slide portion 30 relative to the body portion 12.

[0022] The table section 54 consists of a disc-shaped table body 56, a circular ball bearing plate 60, and a cylindrical base plate 62. The ball bearing plate 60 is positioned in the upper center of the table body 56, and the base plate 62 is positioned above the ball bearing plate 60. The table body 56, the ball bearing plate 60, and the base plate 62 are integrally connected by bolts 66. The base plate 62 is positioned inside the slide body 38. The base plate 62 has a large diameter section 62a, a small diameter section 62b extending downward from the large diameter section 62a, and a flange section 62c projecting radially outward from the upper part of the large diameter section 62a.

[0023] The outer diameter of the flange portion 62c of the base plate 62 is L2 smaller than the inner diameter of the thick-walled portion 38a of the slide body 38. A gap is formed between the outer circumference of the flange portion 62c of the base plate 62 and the inner circumference of the thick-walled portion 38a of the slide body 38. The outer diameter of the small-diameter portion 62b of the base plate 62 is L2 smaller than the inner diameter of the flange portion 38c of the slide body 38. A gap is formed between the outer circumference of the small-diameter portion 62b of the base plate 62 and the inner circumference of the flange portion 38c of the slide body 38. The maximum amount of movement of the table portion 54 in the X and Y directions relative to the slide portion 30 is equal to L2.

[0024] The flange portion 62c of the base plate 62 is located above the flange portion 38c of the slide body 38. An annular second retainer 68 is positioned between the flange portion 62c of the base plate 62 and the flange portion 38c of the slide body 38. The second retainer 68 has a plurality of ball housing holes 68a arranged in the circumferential direction. A first ball 70 is placed in each ball housing hole 68a of the second retainer 68, and a plurality of first balls 70 are held by the second retainer 68. The plurality of first balls 70 are arranged around the axis C1 of the slide portion 30.

[0025] The first ball 70 contacts the upper surface of the flange portion 38c of the slide body 38. The first ball 70 can also contact the lower surface of the flange portion 62c of the base plate 62. By the rolling of the first ball 70 on the upper surface of the flange portion 38c of the slide body 38 and the lower surface of the flange portion 62c of the base plate 62, the table portion 54 can move smoothly in the XY plane relative to the slide portion 30.

[0026] The center of the base plate 62 has a first hole 62d that penetrates vertically. The second ball 72 is housed in the first hole 62d of the base plate 62. That is, a single second ball 72 is positioned on the axis C1 of the slide portion 30 between the ball receiving plate 60 of the table portion 54 and the ball receiving plate 42 of the slide portion 30. The diameter of the second ball 72 is several times larger than the diameter of the first ball 70. The second ball 72 contacts the upper surface of the ball receiving plate 60 of the table portion 54. The second ball 72 also protrudes upward from the first hole 62d of the base plate 62 and can contact the lower surface of the ball receiving plate 42 of the slide portion 30.

[0027] The table portion 54 can change its orientation so that its axis C2 intersects with the axis C1 of the slide portion 30. In other words, the table portion 54 can be tilted relative to the slide portion 30. When an external force is applied to the table portion 54 and the table portion 54 is tilted relative to the slide portion 30, the second ball 72 comes into contact with the ball receiving plate 60 of the table portion 54 and the ball receiving plate 42 of the slide portion 30. In this case, only a portion of the multiple first balls 70 come into contact with the flange portion 62c of the base plate 62, and these first balls 70 are sandwiched between the flange portion 62c of the base plate 62 and the flange portion 38c of the slide body 38 (see Figure 5).

[0028] The body portion 12 is equipped with a regulating pin 40 that protrudes downward from the lower surface of the end plate 26. The table body 56 has a notched groove 56a at a position corresponding to the regulating pin 40 of the body portion 12. The regulating pin 40 of the body portion 12 is inserted into the notched groove 56a of the table body 56, and a predetermined gap is formed around the outer circumference of the regulating pin 40 (see Figure 8). As a result, the table portion 54 can rotate by a predetermined angle around the axis C1 (Z axis) of the body portion 12 and the slide portion 30.

[0029] The compliance unit 10 includes a return mechanism that returns the table portion 54 to its origin position relative to the slide portion 30 and also returns the table portion 54 to its original position relative to the slide portion 30. The return mechanism includes a return ball 76, a ball bearing 78, and a return spring 80.

[0030] The base plate 62 has a plurality (e.g., three) of second holes 62e that penetrate vertically around the first hole 62d. The ball receiving plate 60 of the table portion 54 has a hole 60a at a position corresponding to the second hole 62e of the base plate 62. The table body 56 has a hole 56b at a position corresponding to the second hole 62e of the base plate 62. A spring insertion sleeve 64 is fitted across the second hole 62e of the base plate 62 and the hole 60a of the ball receiving plate 60.

[0031] The lower end of the return spring 80, which is inserted into the sleeve 64, is locked to a plug 58 attached to the lower part of the hole 56b of the table body 56. The upper end of the return spring 80 abuts against the return ball 76, which is housed in the upper part of the second hole 62e of the base plate 62. The ball receiving body 78 has a tapered ball receiving surface 78a that widens downward and is attached to the ball receiving plate 42 of the slide portion 30. The return ball 76, which is biased upward by the return spring 80, abuts against the ball receiving surface 78a of the ball receiving plate 42.

[0032] Multiple return balls 76, biased in a direction parallel to the axis C1 of the slide portion 30, contact the tapered ball receiving surface 78a of the ball receiving body 78. Therefore, when no external force acts on the table body 56, the axis C2 of the table portion 54 coincides with the axis C1 of the slide portion 30. That is, the table portion 54 is held at the origin position in the XY plane relative to the slide portion 30, and the table portion 54 is held in a position that is not tilted relative to the slide portion 30.

[0033] The table portion 54 is held at the origin position in the XY plane relative to the slide portion 30 because the return ball 76 attempts to contact the apex (center) of the tapered ball receiving surface 78a. The table portion 54 is held in a position that is not tilted relative to the slide portion 30 because if the table portion 54 were tilted relative to the slide portion 30, the repulsive forces of the multiple return springs 80 would differ from each other, and a moment would act to correct the tilt.

[0034] The return spring 80 acts to bias the table body 56 downward via the plug 58. When no external force is acting on the table body 56, the multiple first balls 70 are held between the flange portion 62c of the base plate 62, which is integrated with the table body 56, and the flange portion 38c of the slide body 38 by the biasing force of the return spring 80. Reference numeral 82 indicates a positioning pin used when attaching the cover plate 16 to the housing 14. Reference numeral 84 indicates a positioning pin used when attaching the ball receiving plate 42 of the slide portion 30 to the slide body 38.

[0035] The compliance unit 10 according to an embodiment of the present invention is basically configured as described above, and its operation will be explained below. The initial state is when no air is supplied to the pressure chamber 34 and no external force is acting on the table portion 54 (see Figure 1).

[0036] In the initial state described above, the cylinder body 32 is in contact with the bottom surface of the recess 16a of the cover plate 16 due to the biasing force of the slide biasing spring 52. That is, the slide portion 30 has moved to its upper end relative to the body portion 12. Also, due to the action of the return mechanism, the axis C2 of the table portion 54 coincides with the axis C1 of the slide portion 30. Furthermore, the multiple first balls 70 are held between the flange portion 62c of the base plate 62 and the flange portion 38c of the slide body 38 due to the biasing force of the return spring 80. At this time, the second ball 72 is not in contact with the ball receiving plate 42 of the slide portion 30.

[0037] From the initial state described above, when air is supplied to the pressure chamber 34, the slide portion 30 is biased downward. As shown in Figure 2, the slide portion 30 moves to its lower end against the slide portion biasing spring 52, and the slide body 38 comes into contact with the end plate 26. As the slide portion 30 moves downward, the guide ball 46 rolls on the inner circumferential surface of the housing 14 and the outer circumferential surface of the slide body 38.

[0038] In this state, when the table body 56 is pressed against a workpiece (not shown), an external force acts on the table body 56 as a reaction force to the pressing force. As a result, as shown in Figure 3, the table portion 54 moves upward relative to the slide portion 30, and the slide portion 30 moves upward relative to the body portion 12. The movement of the table portion 54 relative to the slide portion 30 is accompanied by compression of the return spring 80. The second ball 72 comes into contact with the ball receiving plate 42 of the slide portion 30. The flange portion 62c of the base plate 62 is spaced apart from the multiple first balls 70.

[0039] An external force acting on the table body 56 is applied to the slide portion 30 via the return ball 76 and the second ball 72, causing the slide portion 30 to move upward relative to the body portion 12. At this time, the combined force of the external force acting on the table body 56 and the force of the slide portion biasing spring 52 biasing the table portion 54 upward balances the force of the air pressure in the pressure chamber 34 biasing the table portion 54 downward. In other words, a pressing force corresponding to the air pressure supplied to the pressure chamber 34 is applied to the table portion 54. When the slide portion 30 moves upward relative to the body portion 12, the guide ball 46 rolls on the inner circumferential surface of the housing 14 and the outer circumferential surface of the slide body 38.

[0040] The compliance unit 10 can absorb errors in the XY plane when a pressing force is applied to the table portion 54. Figure 4 shows the state in which the table portion 54 has moved to the right end, maximizing the absorption of errors in the X direction. As shown in the figure, the outer circumference of the flange portion 62c of the base plate 62 abuts against the inner circumference of the thick portion 38a of the slide body 38, and the outer circumference of the small diameter portion 62b of the base plate 62 abuts against the inner circumference of the flange portion 38c of the slide body 38. In addition, the return ball 76 abuts against the ball receiving surface 78a at a position away from the apex of the ball receiving surface 78a.

[0041] When a pressing force is applied to the table portion 54, and the table portion 54 moves to the right, the second ball 72 rolls on the upper surface of the ball receiving plate 60 of the table portion 54 and the lower surface of the ball receiving plate 42 of the slide portion 30. Since the second ball 72 has a sufficiently large diameter, it can support the pressing load with just one ball.

[0042] The compliance unit 10 can absorb errors regarding the inclination of the table portion 54 (the inclination of the table portion 54 relative to the workpiece) when a pressing force is applied to the table portion 54. Figure 5 shows the state in which the table portion 54 rotates around the Y axis, the axis C2 of the table portion 54 intersects the axis C1 of the slide portion 30 at an angle α, and the inclination error is absorbed.

[0043] As shown in Figure 5, the second ball 72 is in contact with the ball receiving plate 60 of the table portion 54 and the ball receiving plate 42 of the slide portion 30. Of the multiple first balls 70, only the first ball 70 located at the leftmost end is in contact with the flange portion 62c of the base plate 62 and is sandwiched between the flange portion 62c of the base plate 62 and the flange portion 38c of the slide body 38. The other first balls 70 are spaced apart from the flange portion 62c of the base plate 62. The return ball 76 is in contact with the ball receiving surface 78a at a position slightly off-center from the apex of the ball receiving surface 78a.

[0044] The compliance unit 10 can also absorb errors in the Z direction by combining the amount of movement of the slide portion 30 relative to the body portion 12 and the amount of movement of the table portion 54 relative to the slide portion 30. Furthermore, the compliance unit 10 can absorb errors in the XY plane and also absorb errors related to the inclination of the table portion 54 when a pressing force is applied to the table portion 54.

[0045] According to the compliance unit 10 of this embodiment, the table portion 54 can be tilted relative to the slide portion 30, and errors in tilting can be absorbed. Furthermore, a compact configuration can be realized in which the table portion 54 can move in the XY plane relative to the slide portion 30 and the table portion 54 can be tilted relative to the slide portion 30.

[0046] The compliance unit according to the present invention is not limited to the embodiments described above, and can take various configurations without departing from the spirit of the present invention. [Explanation of Symbols]

[0047] 10... Compliance Unit 12... Body Section 18...Intake / exhaust port 30...Slide section 34...Pressure chamber 38...Slide body 42, 60... Ball bearing plate; 44... First retainer (retainer) 46... Guide ball 54... Table section 62...Base plate 68...Second retainer (retainer) 70...First ball 72...Second ball 76... Return ball 78... Ball receiving body 78a...Ball receiving surface 80...Return spring

Claims

1. A compliance unit comprising a body section, a sliding section, and a table section, A compliance unit comprising a slide body constituting the slide portion and a base plate constituting the table portion, wherein a retainer for holding a plurality of first balls is disposed between the slide body constituting the slide portion and the base plate constituting the table portion, the plurality of first balls are arranged around the axis of the slide portion which coincides with the Z axis, a single second ball is disposed on the axis of the slide portion between the ball receiving plate constituting the slide portion and the ball receiving plate constituting the table portion, the table portion is movable in the XY plane relative to the slide portion, the table portion is tiltable relative to the slide portion, and when the table portion is tilted relative to the slide portion, the second ball comes into contact with the ball receiving plate constituting the table portion and the ball receiving plate constituting the slide portion, and only a portion of the plurality of first balls is sandwiched between the base plate and the slide body.

2. In the compliance unit according to claim 1, The slide portion is movable in the Z direction relative to the body portion, and a compliance unit is provided between the body portion and the slide body, wherein a retainer holding a plurality of guide balls is positioned between the body portion and the slide body.

3. In the compliance unit according to claim 2, A compliance unit in which a pressure chamber is formed between the body portion and the slide portion, and the body portion has supply and discharge ports for supplying and discharging air to and from the pressure chamber.

4. In the compliance unit according to claim 1, A compliance unit comprising a return mechanism that returns the table portion to the origin position relative to the slide portion and returns the table portion to its original position relative to the slide portion.

5. In the compliance unit according to claim 4, The return mechanism is a compliance unit that includes a ball receiving body having a tapered ball receiving surface, a return ball that contacts the ball receiving surface, and a return spring that biases the return ball toward the ball receiving surface.

6. In the compliance unit according to claim 5, The ball bearing is attached to the ball bearing plate of the slide portion, and the return spring is a compliance unit mounted on the table portion.

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