Patent Description:
Conventionally, a compliance unit has been used in order to provide a workpiece held by a robot hand with flexibility against an external action thereon.

For example, <CIT> discloses a compliance unit in which a sliding member is disposed in a cylindrical body via a sliding element, and a table is slidably disposed inside the sliding member via a planar sliding 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. <CIT> discloses a component holding device formed by a slide block, a movable block, and a ball bearing portion.

According to the compliance unit above, positioning errors in the XY plane and positioning errors in the Z direction can be absorbed. However, since the table cannot be pivoted about the X-axis and the Y-axis, the table cannot absorb errors concerning an inclination.

The present invention has the object of solving the aforementioned problems.

A compliance unit including a body portion, a slide portion and a table portion, wherein a retainer that holds a plurality of first balls is arranged between the slide body constituting the slide portion and a base plate constituting the table portion, and the plurality of first balls are arranged around an axis of the slide portion that coincides with the Z axis. A single second ball is arranged on the axis line of the slide portion between a first ball receiving plate constituting the slide portion and a second ball receiving plate constituting the table portion. The table portion is movable in the XY plane with respect to the slide portion, and the table portion is tiltable with respect to the slide portion.

According to the compliance unit of the present invention, the table portion can be tilted with respect to the slide portion, and an error concerning the inclination can be absorbed. Further, a configuration in which the table portion can be moved relative to the slide portion in the XY plane and the table portion can be tilted relative to the slide portion can be achieved in a compact manner.

As shown in <FIG>, a compliance unit <NUM> according to an embodiment of the present invention includes a body portion <NUM>, a slide portion <NUM> supported by the body portion <NUM>, and a table portion <NUM> supported by the slide portion <NUM>. The body portion <NUM> is attached to a robot hand (not shown). An axis C1 of the body portion <NUM> and the slide portion <NUM> coincides with the Z-axis. The slide portion <NUM> is movable in the Z direction with respect to the body portion <NUM>.

The table portion <NUM> is movable in an X direction and a Y direction (a direction perpendicular to the paper surface) with respect to the slide portion <NUM>, and is rotatable about an axis C1 (Z axis) of the slide portion <NUM>. In other words, the table portion <NUM> is movable in the XY plane with respect to the slide portion <NUM>. The table portion <NUM> is tiltable with respect to the slide portion <NUM>. In other words, the table portion <NUM> can pivot about the X-axis and the Y-axis. Hereinafter, when the words relating to the up and down (vertical) directions are used, it means the direction parallel to the Z-axis. Further, when the words relating to the right and left directions are used, it means the direction parallel to the X-axis.

The body portion <NUM> includes a cylindrical housing <NUM>, a rectangular cover plate <NUM>, a disc-shaped pressure plate <NUM>, and an annular end plate <NUM>. The cover plate <NUM> is fixed to an upper portion of the housing <NUM>. The pressure plate <NUM> is fixed to a lower central portion of the cover plate <NUM>. The end plate <NUM> is fixed to a lower portion of the housing <NUM>. The cover plate <NUM> has an annular recess 16a on a lower surface thereof, and the pressure plate <NUM> has an annular fitting portion 22a at an upper portion thereof. The fitting portion 22a of the pressure plate <NUM> is fitted into the inner periphery of the recess 16a of the cover plate <NUM>.

The slide portion <NUM> is accommodated in the body portion <NUM>. The slide portion <NUM> includes a bottomed cylindrical cylinder body <NUM>, a cylindrical slide body <NUM>, and a circular ball receiving plate <NUM>. The upper surface of the cylinder body <NUM> can abut on the bottom surface of the recess 16a of the cover plate <NUM>. The slide body <NUM> has a thick portion 38a, a fitting portion 38b extending upward from the upper surface of the thick portion 38a, and a flange portion 38c projecting radially inward from a lower portion of the thick portion 38a. The fitting portion 38b of the slide body <NUM> is press-fitted and fitted to the outer side of the cylinder body <NUM>. The ball receiving plate <NUM> is sandwiched between the lower surface of the cylinder body <NUM> and the upper surface of the thick portion 38a of the slide body <NUM>.

A cylindrical first retainer <NUM> is disposed between the inner peripheral surface of the housing <NUM> and the outer peripheral surface of the slide body <NUM>. The first retainer <NUM> has upper ball receiving holes 44a arranged in the circumferential direction and lower ball receiving holes 44b arranged in the circumferential direction. The upper ball receiving hole 44a and the lower ball receiving hole 44b penetrate the wall surface of the first retainer <NUM> in the radial direction. Guide balls <NUM> are arranged in the upper ball receiving hole 44a and the lower ball receiving hole 44b, and the first retainer <NUM> holds the multiple guide balls <NUM>. The diameter of the guide ball <NUM> is slightly larger than the wall thickness of the first retainer <NUM>.

The guide balls <NUM> come into contact with the inner peripheral surface of the housing <NUM> and also come into contact with the outer peripheral surface of the slide body <NUM>. First springs <NUM> for urging the first retainer <NUM> downward are disposed between the first retainer <NUM> and the cover plate <NUM>. Second springs <NUM> for urging the first retainer <NUM> upward are disposed between the first retainer <NUM> and the end plate <NUM>. The first retainer <NUM> is held at a position separated from the cover plate <NUM> and the end plate <NUM> by the urging forces of the first spring <NUM> and the second spring <NUM>.

The guide balls <NUM> roll on the inner peripheral surface of the housing <NUM> and the outer peripheral surface of the slide body <NUM>, whereby the slide portion <NUM> can move smoothly in the Z direction with respect to the body portion <NUM>. When the slide portion <NUM> moves relative to the body portion <NUM> while the guide balls <NUM> roll on the inner peripheral surface of the housing <NUM> and the outer peripheral surface of the slide body <NUM>, the first retainer <NUM> also moves in the same direction.

The distance from the upper surface of the cylinder body <NUM> to the lower surface of the slide body <NUM> (the height of the slide portion <NUM>) is shorter by L1 than the distance from the bottom surface of the recess 16a of the cover plate <NUM> to the upper surface of the end plate <NUM> (the height of the internal space of the body portion <NUM>). The maximum movement amount of the table portion <NUM> in the Z direction with respect to the slide portion <NUM> is equal to L1. Between the end plate <NUM> and the slide body <NUM>, a slide portion urging spring <NUM> for urging the slide portion <NUM> upward with respect to the body portion <NUM> is disposed (see <FIG>).

The pressure plate <NUM> enters into the inner side of the cylinder body <NUM>. A cylindrical packing <NUM> is mounted on the outer periphery of the pressure plate <NUM>. The upper surface of the packing <NUM> is in close contact with the lower surface of the cover plate <NUM>, and the outer peripheral surface of the packing <NUM> is in sliding contact with the inner peripheral surface of the cylinder body <NUM>. A pressure chamber <NUM> that is kept airtight from the outside is formed between the pressure plate <NUM> and the cylinder body <NUM>.

The cover plate <NUM> has an air supply and discharge port <NUM> connected to an air supply source (not shown) and an air passage <NUM> extending from the air supply and discharge port <NUM>. An end portion of the air passage <NUM> of the cover plate <NUM> opens at the lower surface of the cover plate <NUM>. The pressure plate <NUM> has at a central portion thereof an air passage <NUM> penetrating in the vertical direction. The air passage <NUM> of the pressure plate <NUM> is connected at an upper end thereof to the air passage <NUM> of the cover plate <NUM> and at a lower end thereof to the pressure chamber <NUM>.

When air is supplied to the pressure chamber <NUM> through the supply and discharge port <NUM> of the cover plate <NUM>, the slide portion <NUM> is urged downward. This urging force not only opposes the urging force of the slide portion urging spring <NUM> but also opposes an external force acting on the table portion <NUM>. By adjusting the air pressure supplied to the pressure chamber <NUM>, it is possible to control the pressing force of the table portion <NUM>, whereby a desired buffering action can be obtained.

The slide body <NUM> includes a regulating pin <NUM> projecting downward from the lower surface of the slide body <NUM>. The end plate <NUM> has a regulating hole 26a at a position corresponding to the regulating pin <NUM> of the slide body <NUM>. The regulating pin <NUM> of the slide body <NUM> engages with the regulating hole 26a of the end plate <NUM>. Thus, the pivoting of the slide portion <NUM> relative to the body portion <NUM> is restricted.

The table portion <NUM> includes a disc-shaped table body <NUM>, a circular ball receiving plate <NUM>, and a cylindrical base plate <NUM>. The ball receiving plate <NUM> is disposed at an upper central portion of the table body <NUM>, and the base plate <NUM> is disposed on the upper side of the ball receiving plate <NUM>. The table body <NUM>, the ball receiving plate <NUM>, and the base plate <NUM> are integrally connected with a bolt <NUM>. The base plate <NUM> is disposed on an inner side of the slide body <NUM>. The base plate <NUM> includes a large-diameter portion 62a, a small-diameter portion 62b extending downward from the large-diameter portion 62a, and a flange portion 62c projecting radially outward from an upper portion of the large-diameter portion 62a.

The outer diameter of the flange portion 62c of the base plate <NUM> is smaller by L2 than the inner diameter of the thick portion 38a of the slide body <NUM>. A gap is formed between the outer periphery of the flange portion 62c of the base plate <NUM> and the inner periphery of the thick portion 38a of the slide body <NUM>. The outer diameter of the small-diameter portion 62b of the base plate <NUM> is smaller by L2 than the inner diameter of the flange portion 38c of the slide body <NUM>. A gap is formed between the outer periphery of the small-diameter portion 62b of the base plate <NUM> and the inner periphery of the flange portion 38c of the slide body <NUM>. The maximum movement amount of the table portion <NUM> in the X direction and the Y direction relative to the slide portion <NUM> is equal to L2.

The flange portion 62c of the base plate <NUM> is positioned above the flange portion 38c of the slide body <NUM>. An annular second retainer <NUM> is disposed between the flange portion 62c of the base plate <NUM> and the flange portion 38c of the slide body <NUM>. The second retainer <NUM> has multiple ball receiving holes 68a arranged in the circumferential direction. A first ball <NUM> is arranged in each ball receiving hole 68a of the second retainer (<NUM>), whereby multiple first balls <NUM> are held by the second retainer <NUM>. The first balls <NUM> are arranged around the axis C1 of the slide portion <NUM>.

The first ball <NUM> comes into contact with the upper surface of the flange portion 38c of the slide body <NUM>. The first ball <NUM> can be brought into contact with the lower surface of the flange portion 62c of the base plate <NUM>. The first ball <NUM> rolls on the upper surface of the flange portion 38c of the slide body <NUM> and the lower surface of the flange portion 62c of the base plate <NUM>, whereby the table portion <NUM> can move smoothly in the XY plane with respect to the slide portion <NUM>.

The base plate <NUM> has at a central portion thereof a first hole 62d penetrating in the vertical direction. A second ball <NUM> is accommodated in the first hole 62d of the base plate <NUM>. That is, between the ball receiving plate <NUM> of the table portion <NUM> and the ball receiving plate <NUM> of the slide portion <NUM>, the single second ball <NUM> is disposed on the axis C1 of the slide portion <NUM>. The diameter of the second ball <NUM> is several times larger than the diameter of the first ball <NUM>. The second ball <NUM> comes into contact with the upper surface of the ball receiving plate <NUM> of the table portion <NUM>. Further, the second ball <NUM> protrudes upward from the first hole 62d of the base plate <NUM> and can abut on the lower surface of the ball receiving plate <NUM> of the slide portion <NUM>.

The posture of the table portion <NUM> can be changed so that the axis C2 of the table portion <NUM> intersects the axis C1 of the slide portion <NUM>. That is, the table portion <NUM> can be tilted with respect to the slide portion <NUM>. When the table portion <NUM> is tilted with respect to the slide portion <NUM> in a state in which an external force is applied to the table portion <NUM>, the second ball <NUM> comes into contact with the ball receiving plate <NUM> of the table portion <NUM> and the ball receiving plate <NUM> of the slide portion <NUM>. In this case, only part of the plurality of first balls <NUM> comes into contact with the flange portion 62c of the base plate <NUM>, and the first balls <NUM> are sandwiched between the flange portion 62c of the base plate <NUM> and the flange portion 38c of the slide body <NUM> (see <FIG>).

The body portion <NUM> is provided with a regulating pin <NUM> projecting downward from the lower surface of the end plate <NUM>. The table body <NUM> has a notch groove 56a at a position corresponding to the regulating pin <NUM> of the body portion <NUM>. The regulating pin <NUM> of the body portion <NUM> is inserted into the notch groove 56a of the table body <NUM>, and a predetermined gap is formed around the outer periphery of the regulating pin <NUM> (see <FIG>). Therefore, the table portion <NUM> can be rotated by a predetermined angle around the axis C1 (Z axis) of the body portion <NUM> and the slide portion <NUM>.

The compliance unit <NUM> is provided with a return mechanism that returns the table portion <NUM> to the origin position with respect to the slide portion <NUM> and returns the table portion <NUM> to the original posture with respect to the slide portion <NUM>. The return mechanism includes a return ball <NUM>, a ball receiving body <NUM>, and a return spring <NUM>.

The base plate <NUM> has multiple (e.g., three) second holes 62e penetrating in the vertical direction around the first hole 62d. The ball receiving plate <NUM> of the table portion <NUM> has holes 60a at positions corresponding to the second holes 62e of the base plate <NUM>. The table body <NUM> has holes 56b at positions corresponding to the second holes 62e of the base plate <NUM>. A spring insertion sleeve <NUM> is mounted through both the second hole 62e of the base plate <NUM> and the hole 60a of the ball receiving plate <NUM>.

A lower end of the return spring <NUM> inserted into the sleeve <NUM> engages with a plug <NUM> attached to a lower portion of the hole 56b of the table body <NUM>. The upper end of the return spring <NUM> comes into contact with the return ball <NUM> accommodated in an upper portion of the second hole 62e of the base plate <NUM>. The ball receiving body <NUM> includes a tapered ball receiving surface 78a spreading downward, and is attached to the ball receiving plate <NUM> of the slide portion <NUM>. The return ball <NUM> urged upward by the return spring <NUM> comes into contact with the ball receiving surface 78a of the ball receiving plate <NUM>.

A plurality of return balls <NUM> urged in a direction parallel to the axis C1 of the slide portion <NUM> come into contact with a tapered ball receiving surface 78a of the ball receiving body <NUM>. Therefore, when no external force acts on the table body <NUM>, the axis C2 of the table portion <NUM> coincides with the axis C1 of the slide portion <NUM>. That is, the table portion <NUM> is held at the origin on the XY plane with respect to the slide portion <NUM>, and the table portion <NUM> is held in a posture that is not tilted with respect to the slide portion <NUM>.

The table portion <NUM> is held at the origin on the XY plane with respect to the slide portion <NUM> because the return ball <NUM> tends to come into contact with the apex (center) of the tapered ball receiving surface 78a. The reason why the table portion <NUM> is maintained in a posture that is not tilted with respect to the slide portion <NUM> is that if the table portion <NUM> stays tilted with respect to the slide portion <NUM>, repulsive forces of multiple return springs <NUM> are different from each other, and a moment for correcting the inclination acts.

The return spring <NUM> serves to urge the table body <NUM> downward via the plug <NUM>. In a state where no external force acts on the table body <NUM>, the first balls <NUM> are held between the flange portion 38c of the slide body <NUM> and the flange portion 62c of the base plate <NUM> integrated with the table body <NUM> by the urging force of the return spring <NUM>. Reference numeral <NUM> denotes a positioning pin for attaching the cover plate <NUM> to the housing <NUM>. Reference numeral <NUM> denotes a positioning pin for attaching the ball receiving plate <NUM> of the slide portion <NUM> to the slide body <NUM>.

The compliance unit <NUM> according to the embodiment of the present invention is basically configured as described above, and the operation thereof will be described below. A state in which no air is supplied to the pressure chamber <NUM> and no external force acts on the table portion <NUM> is set as an initial state (see <FIG>).

In the initial state, the cylinder body <NUM> is brought into contact with the bottom surface of the recess 16a of the cover plate <NUM> by the urging force of the slide portion urging spring <NUM>. That is, the slide portion <NUM> has been moved to the upper end with respect to the body portion <NUM>. Further, the axis C2 of the table portion <NUM> coincides with the axis C1 of the slide portion <NUM> because of the function of the return mechanism. The plurality of first balls <NUM> are held between the flange portion 62c of the base plate <NUM> and the flange portion 38c of the slide body <NUM> by the urging force of the return spring <NUM>. At this time, the second ball <NUM> is not in contact with the ball receiving plate <NUM> of the slide portion <NUM>.

When air is supplied to the pressure chamber <NUM> at the initial state, the slide portion <NUM> is urged downward. As shown in <FIG>, the slide portion <NUM> moves to the lower end against the slide portion urging spring <NUM>, and the slide body <NUM> comes into contact with the end plate <NUM>. When the slide portion <NUM> moves downward, the guide ball <NUM> rolls on the inner peripheral surface of the housing <NUM> and the outer peripheral surface of the slide body <NUM>.

In this state, when the table body <NUM> is pressed against a workpiece (not shown), an external force acting as a reaction force of the pressing force acts on the table body <NUM>. Therefore, as shown in <FIG>, the table portion <NUM> moves upward with respect to the slide portion <NUM>, and together therewith, the slide portion <NUM> moves upward with respect to the body portion <NUM>. Movement of the table portion <NUM> relative to the slide portion <NUM> is accompanied by compression of the return spring <NUM>. The second ball <NUM> abuts against the ball receiving plate <NUM> of the slide portion <NUM>. The flange portion 62c of the base plate <NUM> moves apart from the first balls <NUM>.

An external force acting on the table body <NUM> is applied to the slide portion <NUM> via the return ball <NUM> and the second ball <NUM>, whereby the slide portion <NUM> moves upward with respect to the body portion <NUM>. At this time, the combined force of the external force acting on the table body <NUM> and the force by which the slide portion urging spring <NUM> urges the table portion <NUM> upward is balanced with the force by which the air pressure in the pressure chamber <NUM> urges the table portion <NUM> downward. That is, a pressing force commensurate with the air pressure supplied to the pressure chamber <NUM> is applied to the table portion <NUM>. When the slide portion <NUM> moves upward relative to the body portion <NUM>, the guide balls <NUM> roll on the inner peripheral surface of the housing <NUM> and the outer peripheral surface of the slide body <NUM>.

The compliance unit <NUM> can absorb an error in the XY plane in a state in which a pressing force is applied to the table portion <NUM>. <FIG> shows a state in which the table portion <NUM> has moved to the right end and has absorbed the error in the X direction to the maximum. As shown in the figure, the outer periphery of the flange portion 62c of the base plate <NUM> abuts against the inner periphery of the thick portion 38a of the slide body <NUM>, and the outer periphery of the small diameter portion 62b of the base plate <NUM> abuts against the inner periphery of the flange portion 38c of the slide body <NUM>. Further, the return ball <NUM> is in contact with the ball receiving surface 78a at a position away from the apex of the ball receiving surface 78a.

When the table portion <NUM> moves rightward in a state in which a pressing force is applied to the table portion <NUM>, the second ball <NUM> rolls on the upper surface of the ball receiving plate <NUM> of the table portion <NUM> and the lower surface of the ball receiving plate <NUM> of the slide portion <NUM>. Because the second ball <NUM> has a sufficient diameter, only one ball <NUM> can support the pressing load.

The compliance unit <NUM> can absorb an error concerning the inclination of the table portion <NUM> (inclination of the table portion <NUM> with respect to the workpiece) in a state in which a pressing force is applied to the table portion <NUM>. <FIG> shows a state in which the table portion <NUM> pivots about the Y-axis, the axis C2 of the table portion <NUM> intersects the axis C1 of the slide portion <NUM> at an angle α, and an error concerning the inclination is absorbed.

As shown in <FIG>, the second ball <NUM> is in contact with the ball receiving plate <NUM> of the table portion <NUM> and the ball receiving plate <NUM> of the slide portion <NUM>. Among the plurality of first balls <NUM>, only the first ball <NUM> positioned at the left end abuts on the flange portion 62c of the base plate <NUM> and is sandwiched between the flange portion 62c of the base plate <NUM> and the flange portion 38c of the slide body <NUM>. The other first balls <NUM> are separated from the flange portion 62c of the base plate <NUM>. The return ball <NUM> is in contact with the ball receiving surface 78a at a position slightly deviated from the apex of the ball receiving surface 78a.

The compliance unit <NUM> can also absorb an error in the Z direction, making use of the sum of the movement amount of the slide portion <NUM> with respect to the body portion <NUM> and the movement amount of the table portion <NUM> with respect to the slide portion <NUM>. Further, in a state in which a pressing force is applied to the table portion <NUM>, the compliance unit <NUM> can absorb an error in the XY plane and also absorb an error concerning the inclination of the table portion <NUM>.

Claim 1:
A compliance unit (<NUM>) comprising a body portion (<NUM>), a slide portion (<NUM>), and a table portion (<NUM>),
wherein
a retainer (<NUM>) that holds a plurality of first balls (<NUM>) is arranged between a slide body (<NUM>) constituting the slide portion and a base plate (<NUM>) constituting the table portion,
the plurality of first balls are arranged around an axis of the slide portion that coincides with a Z-axis,
a single second ball (<NUM>) is arranged on the axis of the slide portion between a first ball receiving plate (<NUM>) constituting the slide portion and a second ball receiving plate (<NUM>) constituting the table portion,
the table portion is movable in a XY plane with respect to the slide portion, and
the table portion is tiltable with respect to the slide portion.