Compliance unit

Abstract

Between the sliding body (38) constituting the sliding part (30) and the base plate (62) constituting the platform part (54), a retaining ring (68) for holding a plurality of first balls (70) is disposed; the plurality of first balls are arranged side by side around the axis (C1) of the sliding part that is aligned with the Z-axis, and a single second ball (72) is disposed between the ball support plate (42) constituting the sliding part and the ball support plate (60) constituting the platform part and on the axis of the sliding part.

Description

Technical Field

[0001] The present invention relates to a compliant unit that flexibly holds a workpiece and absorbs positioning errors in the automatic assembly of a robot arm. Prior Art

[0002] Conventionally, a compliance unit has been used to provide flexibility to a workpiece held by a robot arm against external forces. [Prior Art Literature]

[0003] For example, Japanese Patent Application Laid-Open No. 2000-153489 describes a compliant unit comprising a sliding member disposed within a cylindrical body via a sliding element, and a table slidably disposed within the sliding member via a planar sliding element. The sliding member is movable in the Z direction relative to the body, and the table is movable within the XY plane relative to the sliding member. Summary of the Invention

[0004] [Problems to be solved by the invention]

[0005] The aforementioned compliance unit can absorb positioning errors within the XY plane and in the Z direction. However, the stage cannot rotate around the X and Y axes, so it cannot absorb errors related to tilt.

[0006] An object of the present invention is to solve the above-mentioned problems. [Methods for solving the problem]

[0007] The present invention provides a compliant unit comprising a main body, a sliding portion, and a table. A retainer for retaining a plurality of first balls is disposed between the sliding body constituting the sliding portion and a base plate constituting the table. The plurality of first balls are arranged side by side around the axis of the sliding portion, which is aligned with the Z axis. A single second ball is disposed on the axis of the sliding portion between a ball support plate constituting the sliding portion and a ball support plate constituting the table. The table is movable relative to the sliding portion within the XY plane and can tilt relative to the sliding portion.

[0008] The compliant unit of the present invention allows the table to tilt relative to the slide, absorbing any errors in the tilt. Furthermore, a compact structure is achieved that allows the table to move relative to the slide within the XY plane and tilt relative to the slide.

[0009] The above-mentioned objects, features, and advantages can be easily understood from the following embodiments described with reference to the accompanying drawings. Simple diagram description

[0010] FIG1 is a cross-sectional view of a compliant unit according to an embodiment of the present invention, taken along a plane including the X-axis and the Z-axis.

[0011] FIG2 is a cross-sectional view of the compliance unit in FIG1 when air is supplied.

[0012] FIG3 is a cross-sectional view when a pressing force is applied to the table portion of the compliance unit in FIG1 .

[0013] FIG4 is a cross-sectional view of the compliant unit in FIG1 when absorbing an error in the X direction.

[0014] FIG5 is a cross-sectional view of the compliance unit in FIG1 when absorbing an error due to tilt.

[0015] [Fig. 6] is an external view of the compliance unit in Fig. 1.

[0016] FIG7 is a partial cross-sectional view when the compliant unit of FIG1 is cut along a plane including the Z axis but not including the X axis.

[0017] FIG8 is a diagram showing the relationship between the restriction pin of the main body and the notch groove of the table body. Implementation Method

[0018] As shown in FIG1 , a compliant unit 10 according to an embodiment of the present invention includes a main body 12, a sliding portion 30 supported by the main body 12, and a stage 54 supported by the sliding portion 30. The main body 12 is mounted on a robot arm (not shown). The axis C1 between the main body 12 and the sliding portion 30 coincides with the Z axis. The sliding portion 30 is movable in the Z direction relative to the main body 12.

[0019] The stage 54 is movable relative to the slide 30 in the X and Y directions (perpendicular to the drawing) and is rotatable about the axis C1 (Z-axis) of the slide 30. In other words, the stage 54 is movable relative to the slide 30 within the XY plane. Furthermore, the stage 54 is tiltable relative to the slide 30. In other words, the stage 54 is rotatable about the X and Y axes. Hereinafter, when terms are used referring to the vertical direction, they refer to directions parallel to the Z axis. When terms are used referring to the horizontal direction, they refer to directions parallel to the X axis.

[0020] The main body 12 is composed of a cylindrical shell 14, a rectangular outer shell plate 16, a disc-shaped pressure plate 22, and an annular end plate 26. The outer shell plate 16 is fixed to the upper portion of the shell 14. The pressure plate 22 is fixed to the lower center of the outer shell plate 16. The end plate 26 is fixed to the lower portion of the shell 14. The outer shell plate 16 has an annular recess 16a on its lower portion, and the pressure plate 22 has an annular fitting portion 22a on its upper portion. The fitting portion 22a of the pressure plate 22 fits within the inner circumference of the recess 16a of the outer shell plate 16.

[0021] The sliding portion 30 is housed within the main body 12. The sliding portion 30 is composed of a bottomed cylindrical cylinder 32, a cylindrical sliding body 38, and a circular ball bearing plate 42. The upper portion of the cylinder 32 is capable of abutting against the bottom surface of the recess 16a of the outer shell plate 16. The sliding body 38 has a thick-walled portion 38a, a fitting portion 38b extending upward from the upper portion of the thick-walled portion 38a, and a flange portion 38c protruding radially inward from the lower portion of the thick-walled portion 38a. The fitting portion 38b of the sliding body 38 is press-fitted into the outer side of the cylinder 32. The ball bearing plate 42 is clamped between the lower portion of the cylinder 32 and the upper portion of the thick-walled portion 38a of the sliding body 38.

[0022] A cylindrical first retainer 44 is disposed between the inner circumferential surface of the housing 14 and the outer circumferential surface of the sliding body 38. The first retainer 44 has a plurality of upper ball-receiving holes 44a and a plurality of lower ball-receiving holes 44b arranged circumferentially. The upper and lower ball-receiving holes 44a and 44b extend radially through the wall of the first retainer 44. Guide balls 46 are disposed in the upper and lower ball-receiving holes 44a and 44b, and the first retainer 44 retains the plurality of guide balls 46. The diameter of the guide balls 46 is slightly larger than the wall thickness of the first retainer 44.

[0023] The guide balls 46 abut against the inner circumference of the housing 14 and the outer circumference of the sliding body 38. A plurality of first springs 48 are disposed between the first retainer 44 and the outer shell plate 16 to bias the first retainer 44 downward. A plurality of second springs 50 are disposed between the first retainer 44 and the end plate 26 to bias the first retainer 44 upward. The first retainer 44 is held at a position spaced apart from the outer shell plate 16 and the end plate 26 by the biasing forces of the first springs 48 and the second springs 50.

[0024] By allowing the guide balls 46 to roll on the inner circumference of the housing 14 and the outer circumference of the sliding body 38, the sliding portion 30 can move smoothly in the Z direction relative to the main body 12. When the guide balls 46 roll on the inner circumference of the housing 14 and the outer circumference of the sliding body 38 and the sliding portion 30 moves relative to the main body 12, the first retainer 44 also moves in the same direction.

[0025] The distance from the top of the cylinder 32 to the bottom of the sliding body 38 (the height of the sliding portion 30) is shorter by L1 than the distance from the bottom of the recess 16a of the outer shell plate 16 to the top of the end plate 26 (the height of the interior space of the main body 12). The maximum Z-direction movement of the stage 54 relative to the sliding portion 30 is equal to L1. A sliding portion biasing spring 52 (see Figure 7) is located between the end plate 26 and the sliding body 38 to bias the sliding portion 30 upward relative to the main body 12.

[0026] The pressure plate 22 extends into the interior of the cylinder 32. A cylindrical gasket 36 is attached to the outer periphery of the pressure plate 22. The upper surface of the gasket 36 is in close contact with the lower surface of the outer shell plate 16, and the outer circumference of the gasket 36 is in sliding contact with the inner circumference of the cylinder 32. A pressure chamber 34 is formed between the pressure plate 22 and the cylinder 32, which is airtight from the outside.

[0027] The outer shell plate 16 has an air supply and exhaust port 18 connected to an air supply source (not shown), and an air passage 20 extending from the air supply and exhaust port 18. The end of the air passage 20 of the outer shell plate 16 opens at the lower surface of the outer shell plate 16. The pressure plate 22 has an air passage 24 extending vertically through the center. The air passage 24 of the pressure plate 22 is connected to the air passage 20 of the outer shell plate 16 at its upper end and to the pressure chamber 34 at its lower end.

[0028] When air is supplied to the pressure chamber 34 through the supply and exhaust ports 18 of the outer shell 16, the sliding portion 30 is biased from below. This biasing force is used to overcome the biasing force of the sliding portion biasing spring 52 and the external force acting on the table 54. By adjusting the air pressure supplied to the pressure chamber 34, the pressing force of the table 54 can be controlled to achieve the desired cushioning effect.

[0029] The sliding body 38 includes a restriction pin 28 that protrudes downward from its lower surface. The end plate 26 has a restriction hole 26a at a position corresponding to the restriction pin 28 of the sliding body 38. The restriction pin 28 of the sliding body 38 engages with the restriction hole 26a of the end plate 26. This restricts the rotation of the sliding portion 30 relative to the main body 12.

[0030] The platform 54 is composed of a disc-shaped platform body 56, a circular ball bearing plate 60, and a cylindrical base plate 62. The ball bearing plate 60 is positioned at the center of the upper portion of the platform body 56, and the base plate 62 is positioned above the ball bearing plate 60. The platform 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 sliding body 38. The base plate 62 has a large diameter portion 62a, a small diameter portion 62b extending downward from the large diameter portion 62a, and a flange portion 62c protruding radially outward from the upper portion of the large diameter portion 62a.

[0031] The outer diameter of the flange portion 62c of the base plate 62 is smaller by L2 than the inner diameter of the thick portion 38a of the sliding body 38. A gap is formed between the outer periphery of the flange portion 62c of the base plate 62 and the inner periphery of the thick portion 38a of the sliding body 38. The outer diameter of the small-diameter portion 62b of the base plate 62 is smaller by L2 than the inner diameter of the flange portion 38c of the sliding body 38. A gap is formed between the outer periphery of the small-diameter portion 62b of the base plate 62 and the inner periphery of the flange portion 38c of the sliding body 38. The maximum movement of the stage 54 in the X and Y directions relative to the sliding portion 30 is equal to L2.

[0032] The flange portion 62c of the base plate 62 is positioned above the flange portion 38c of the sliding body 38. An annular second retainer 68 is disposed between the flange portion 62c of the base plate 62 and the flange portion 38c of the sliding body 38. The second retainer 68 has a plurality of ball-receiving holes 68a arranged side by side in the circumferential direction. A first ball 70 is disposed in each ball-receiving hole 68a of the second retainer 68, and the plurality of first balls 70 are retained by the second retainer 68. The plurality of first balls 70 are arranged around the axis C1 of the sliding portion 30.

[0033] The first balls 70 abut against the upper surface of the flange 38c of the sliding body 38. The first balls 70 can also abut against the lower surface of the flange 62c of the base plate 62. By rolling the first balls 70 against the upper surface of the flange 38c of the sliding body 38 and the lower surface of the flange 62c of the base plate 62, the stage 54 can move smoothly relative to the sliding portion 30 within the XY plane.

[0034] The base plate 62 has a first hole 62d extending vertically through the center. A second ball 72 is housed in the first hole 62d of the base plate 62. Specifically, a single second ball 72 is positioned between the ball support plate 60 of the table 54 and the ball support plate 42 of the sliding portion 30, on the axis C1 of the sliding portion 30. The diameter of the second ball 72 is several times larger than that of the first ball 70. The second ball 72 abuts the upper surface of the ball support plate 60 of the table 54. Furthermore, the second ball 72 protrudes upward from the first hole 62d of the base plate 62 and can abut the lower surface of the ball support plate 42 of the sliding portion 30.

[0035] The table 54 can change its position so that the axis C2 of the table 54 intersects the axis C1 of the sliding portion 30. In other words, the table 54 can tilt relative to the sliding portion 30. When an external force is applied to the table 54 and the table 54 tilts relative to the sliding portion 30, the second balls 72 abut against the ball support plate 60 of the table 54 and the ball support plate 42 of the sliding portion 30. In this case, only a portion of the plurality of first balls 70 abuts against the flange 62c of the base plate 62, and the first balls 70 are sandwiched between the flange 62c of the base plate 62 and the flange 38c of the sliding body 38 (see Figure 5).

[0036] The main body 12 includes a restriction pin 40 that protrudes downward from the lower surface of the end plate 26. The platform body 56 has a notch 56a at a position corresponding to the restriction pin 40 of the main body 12. The restriction pin 40 of the main body 12 is inserted into the notch 56a of the platform body 56, with a predetermined gap formed around the outer periphery of the restriction pin 40 (see Figure 8). Therefore, the platform 54 can rotate a predetermined angle about the axis C1 (Z-axis) of the main body 12 and the sliding portion 30.

[0037] The compliant unit 10 includes a return mechanism that returns the table 54 to its original position relative to the sliding portion 30 and returns the table 54 to its original position relative to the sliding portion 30. The return mechanism includes a return ball 76, a ball support 78, and a return spring 80.

[0038] The base plate 62 has a plurality (e.g., three) of second holes 62e extending vertically around the first hole 62d. The ball support plate 60 of the platform 54 has a hole 60a at a position corresponding to the second hole 62e of the base plate 62. The platform body 56 has a hole 56b at a position corresponding to the second hole 62e of the base plate 62. A sleeve 64 for inserting a spring is mounted between the second hole 62e of the base plate 62 and the hole 60a of the ball support plate 60.

[0039] The lower end of the return spring 80, inserted into the sleeve 64, is engaged with the plug 58 mounted below the hole 56b of the platform body 56. The upper end of the return spring 80 abuts against the return ball 76 housed in the upper portion of the second hole 62e of the base plate 62. The ball support body 78 has a tapered ball support surface 78a that expands downward and is mounted on the ball support plate 42 of the sliding portion 30. The return ball 76, biased upward by the return spring 80, abuts against the ball support surface 78a of the ball support plate 42.

[0040] The plurality of return balls 76, biased in a direction parallel to the axis C1 of the sliding portion 30, abut against the tapered ball bearing surface 78a of the ball bearing body 78. Therefore, when no external force is applied to the table body 56, the axis C2 of the table 54 is aligned with the axis C1 of the sliding portion 30. In other words, the table 54 is maintained at its origin relative to the sliding portion 30 within the XY plane and is maintained in a posture that does not tilt relative to the sliding portion 30.

[0041] The platform 54 is held at its origin relative to the slide 30 in the XY plane because the return ball 76 abuts the apex (center) of the tapered ball bearing surface 78a. The platform 54 is held in a non-tilted position relative to the slide 30 because if the platform 54 tilts relative to the slide 30, the inertial force correcting the tilt is generated by the different repulsive forces of the multiple return springs 80.

[0042] The return spring 80 serves to bias the platform body 56 downward via the plunger 58. When no external force is acting on the platform body 56, the plurality of first balls 70 are held between the flange 62c of the base plate 62, which is integral with the platform body 56, and the flange 38c of the sliding body 38 by the biasing force of the return spring 80. Reference numeral 82 denotes a positioning pin for attaching the outer shell plate 16 to the housing 14. Reference numeral 84 denotes a positioning pin for attaching the ball support plate 42 of the sliding unit 30 to the sliding body 38.

[0043] The compliant unit 10 according to the embodiment of the present invention is basically constructed as described above. The following describes its operation. The state in which air is not supplied to the pressure chamber 34 and no external force is applied to the stage 54 is referred to as the initial state (see FIG1 ).

[0044] In the initial state described above, the cylinder 32, biased by the sliding portion biasing spring 52, abuts the bottom surface of the recess 16a of the outer shell plate 16. In other words, the sliding portion 30 can move to the upper end relative to the main body 12. The return mechanism aligns the axis C2 of the platform 54 with the axis C1 of the sliding portion 30. The plurality of first balls 70, biased by the return spring 80, are clamped between the flange 62c of the base plate 62 and the flange 38c of the sliding body 38. At this point, the second balls 72 are not abutting the ball support plate 42 of the sliding portion 30.

[0045] When air is supplied to the pressure chamber 34 from the initial state, the slider 30 is biased downward. As shown in FIG2 , the slider 30 overcomes the slider biasing spring 52 and moves to the lower end, causing the slider body 38 to abut against the end plate 26. As the slider 30 moves downward, the guide balls 46 roll on the inner circumferential surface of the housing 14 and the outer circumferential surface of the slider body 38.

[0046] In this state, when the table body 56 is pressed against a workpiece (not shown), an external force acting as a reaction to the pressing force acts on the table body 56. Consequently, as shown in FIG3 , the table 54 moves upward relative to the sliding portion 30, and the sliding portion 30 moves upward relative to the main body 12. The movement of the table 54 relative to the sliding portion 30 is accompanied by compression of the return spring 80. The second balls 72 abut against the ball support plate 42 of the sliding portion 30. The flange portion 62c of the base plate 62 separates from the plurality of first balls 70.

[0047] When the external force acting on the table body 56 is applied to the sliding portion 30 via the return balls 76 and the second balls 72, the sliding portion 30 moves upward relative to the main body 12. At this time, the combined force of the external force acting on the table body 56 and the upward biasing force of the sliding portion biasing spring 52 balances the downward biasing force of the table 54 caused by the air pressure in the pressure chamber 34. In other words, a pressing force corresponding to the air pressure supplied to the pressure chamber 34 is applied to the table 54. As the sliding portion 30 moves upward relative to the main body 12, the guide balls 46 roll on the inner circumferential surface of the housing 14 and the outer circumferential surface of the sliding body 38.

[0048] The compliant unit 10 can absorb errors in the XY plane while applying pressure to the stage 54. Figure 4 shows the stage 54 moved to the right end, maximizing the absorption of errors in the X direction. As shown in Figure 4, the outer periphery of the flange 62c of the base plate 62 abuts the inner periphery of the thick-walled portion 38a of the sliding body 38, and the outer periphery of the small-diameter portion 62b of the base plate 62 abuts the inner periphery of the flange 38c of the sliding body 38. Furthermore, the return ball 76 abuts the ball support surface 78a at a position offset from the apex of the ball support surface 78a.

[0049] When the table 54 moves rightward while a pressing force is applied to it, the second balls 72 roll on the upper surface of the ball support plate 60 of the table 54 and the lower surface of the ball support plate 42 of the sliding portion 30. Since the second balls 72 have a sufficiently large diameter, only one can support the pressing load.

[0050] The compliant unit 10 absorbs errors in the tilt of the table 54 (the tilt of the table 54 relative to the workpiece) while applying a pressing force to the table 54. Figure 5 shows the table 54 rotating about the Y-axis, with the axis C2 of the table 54 intersecting the axis C1 of the slide 30 at an angle α. This absorbs errors in the tilt.

[0051] As shown in Figure 5, the second balls 72 abut the ball support plate 60 of the platform 54 and the ball support plate 42 of the sliding portion 30. Of the plurality of first balls 70, only the leftmost first ball 70 abuts the flange 62c of the base plate 62, and this first ball 70 is sandwiched between the flange 62c of the base plate 62 and the flange 38c of the sliding body 38. The other first balls 70 are separated from the flange 62c of the base plate 62. The return ball 76 abuts the ball support surface 78a at a position slightly offset from the apex of the ball support surface 78a.

[0052] The compliant unit 10 can absorb errors in the Z direction using the sum of the movement of the slide 30 relative to the main body 12 and the movement of the stage 54 relative to the slide 30. Furthermore, the compliant unit 10 absorbs errors in the XY plane while applying a pressing force to the stage 54, and can also absorb errors caused by the tilt of the stage 54.

[0053] The compliant unit 10 of this embodiment allows the table 54 to tilt relative to the slide 30, absorbing any tilting errors. Furthermore, a compact structure is achieved that allows the table 54 to move relative to the slide 30 within the XY plane and tilt relative to the slide 30.

[0054] The compliance unit of the present invention is not limited to the above-described embodiment, and may adopt various structures without departing from the gist of the present invention.

[0055] 10: Adaptive unit 12: Main body 18: Supply and discharge port 30: Sliding part 34: Pressure Chamber 38: Sliding body 42,60: ball bearing plate 44: 1st retaining ring (retaining ring) 46: Guide ball 54: Taiwan Department 62:Substrate 68: Second guard ring (guard ring) 70: 1st ball 72: 2nd ball 76:Reply Ball 78: Ball bearing 78a: Ball bearing surface 80:Return spring

Claims

1. A conforming unit (10) comprising: a main body (12), a sliding part (30), and a platform (54); a retaining ring (68) for holding a plurality of first balls (70) is disposed between the sliding main body (38) constituting the sliding part and the substrate (62) constituting the platform; the plurality of the first balls are arranged side by side around the axis of the sliding part, which is aligned with the Z-axis; a single second ball (72) is disposed between the ball support plate (42) constituting the sliding part and the ball support plate (60) constituting the platform, and on the axis of the sliding part; the platform is movable relative to the sliding part in the XY plane and is tiltable relative to the sliding part; when the platform is tilted relative to the sliding part, the second ball abuts against the ball support plate constituting the platform and the ball support plate constituting the sliding part, and only a portion of the plurality of the first balls is held between the substrate and the sliding main body.

2. As in the compliance unit of request item 1, where, The sliding part can move in the Z direction relative to the main body, and a retaining ring (44) for holding a plurality of guide balls (46) is disposed between the main body and the sliding body.

3. As in the compliance unit of request item 2, wherein, A pressure chamber (34) is formed between the main body and the sliding part. The main body has a supply or exhaust port (18) for supplying or discharging air into or out of the pressure chamber.

4. As in the compliance unit of request item 1, wherein, It is equipped with a return mechanism that returns the platform to its original position relative to the sliding part and restores the platform to its original posture relative to the sliding part.

5. As in the compliance unit of request item 4, wherein, The aforementioned return mechanism includes: a ball support body (78) having a conical ball support surface (78a), a return ball (76) abutting against the ball support surface, and a return spring (80) that presses the return ball toward the ball support surface.

6. As in the compliance unit of request item 5, wherein, The ball bearing is mounted on the ball bearing plate of the sliding part, and the return spring is mounted on the platform.

Images