JP2003170383A - Compliance unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compliance unit capable of surely and accurately storing the displacement of the position of a body relative to a table. <P>SOLUTION: A compliance mechanism 3 having a compliance function with respect to X and Y axis directions and θ rotating direction is installed between the body 1 and the table 2. A plurality of cylinders 12A and 12B are installed in the body 1, and the tips of pistons 14A and 14B therefor are opposed to a swing plate 5 connected to the table 2 housed in the body 1. Concave moving arresting parts 19A and 19B coming into contact with the swing plate 5 on the center axis of the pistons are installed at the tips of the pistons 14A and 14B. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compliance unit which is attached to a product assembling robot or the like and absorbs positional deviations and dimensional tolerances between works to be joined.

[0002]

2. Description of the Related Art For example, in the automatic assembly work of products by an industrial robot, etc., when a compliance unit is used to absorb a positional error between works,
With respect to the body attached to the robot arm (or the work chuck means), the table attached to the work chuck means (or the robot arm) is orthogonal to the center axis of the body and the table and is also orthogonal to each other.
It is often required to have three degrees of freedom in the axial direction, the Y-axis direction, and the θ rotation direction around the central axis. In the compliance unit, the type that absorbs the error every time the work is performed has been the mainstream until now, but in recent years, the type that stores the positional error in the first work and uses it in the next work needs the market. Is adapted to.

In the type of storing such positional error, one cylinder is provided in the body,
By pressing the central portion of the table by the piston of this cylinder, the relative position between the body and the table can be fixed, and by this,
It is usual to store the mutual positional deviation between the body and the table caused by absorption of the positional error. However, in this type of compliance unit, since it is generally assumed that the piston and the table are brought into contact with each other between flat surfaces, the contact surfaces of the piston and the table are highly accurately surface-contacted. If the contact is not made, the contact may be made at one point A ₀ on the peripheral edge of the tip of the piston P, as hypothetically shown in FIG. In FIG. 6, b is a steel ball, g is a guide for holding it, and t is a table. In this case, the piston P is rotatable and the contact point A ₀ of the tip of the piston P with the table t is away from the central axis of the piston P, so that the external force acting on the table t causes the piston P to move. It is conceivable that the table t rotates easily and the table t cannot be reliably and stably fixed. This is also the case when there are a plurality of pistons, and in any case, the relative position between the body and the table cannot be accurately stored.

[0004]

SUMMARY OF THE INVENTION The technical problem of the present invention is to provide a compliance unit having a three-degree-of-freedom compliance function in the X-axis, Y-axis, and θ directions, in which relative displacement between the body and the table is caused. The object is to provide a device capable of surely and accurately storing.

[0005]

In order to solve the above-mentioned problems, the compliance unit of the present invention includes a body and a table, which are joined to each other, having X and X orthogonal to their central axes and orthogonal to each other. A compliance mechanism that exerts a compliance function in the Y-axis direction and in the θ rotation direction around the central axis is interposed,
The body is provided with a plurality of cylinders, and the tips of the pistons are opposed to a swing plate that is integrally coupled to the table and moves in the body by the compliance mechanism. It is characterized in that a convex curved movement restraint portion which is in contact with the swing plate on the central axis of the piston is provided.

In the compliance unit having the above construction, the body is provided with a plurality of cylinders, and the movement restraining portions having a convex curved surface are provided at the tips of the pistons of the cylinders to restrain the table at a plurality of points. Therefore, the table can be securely fixed without any adverse effect when the piston and the table are brought into surface contact with each other as in the conventional case, and thereby the relative position between the body and the table can be stabilized. It can be fixed and the positional relationship can be accurately stored.

In the present invention, an annular base plate whose front and back surfaces are parallel to each other is fixed to the table side of the body, and both front and back surfaces of the base plate are retained by retainers holding steel balls. The compliance mechanism can be configured by being sandwiched by the table and the swing plate integrally connected to the table. Further, the periphery of both ends of each piston may be supported by a large number of steel balls held by guides to prevent tilting of the piston axis. In this case, the movement restraint portion is arranged in a ring shape around the tip end side of the outer peripheral surface of each piston, and the steel ball rollingly brought into contact with the piston and the piston at the height of the contact point between the piston and the steel ball. It is desirable to form a spherical surface centered on a point on the central axis.

Further, according to the present invention, an origin returning mechanism may be provided between the body and the table for returning the mutual positional deviation caused by the compliance mechanism to the origin position. In this case, , The origin return mechanism is a steel ball provided on either the body or the table, a ball receiver provided so as to be displaced together with the other, and the steel ball is press-fitted onto the ball receiver. It may be composed of a plurality of pairs with elastic means, or it is provided so as to be displaced together with the body and the table, and the body and the table are placed at the origin position by magnetically attracting each other. The suction member may be configured to be pulled back to.

[0009]

1 to 3 show a first embodiment of a compliance unit of the present invention, which is a robot arm or a work chuck means such as an air chuck. A body 1 for mounting on one side and a table 2 for mounting on the other side are joined to each other. Then, between the body 1 and the table 2, X and Y axis directions orthogonal to the central axis L of the body 1 and the table 2 and orthogonal to each other, and a θ rotation direction around the central axis L. A compliance mechanism 3 that exerts a compliance function for and is interposed.

The table 2 has a disk-shaped table body 4 for mounting on a work chuck or the like, a disk-shaped oscillating plate 5 having a diameter smaller than that of the table body 4, and the table body 4 and the oscillating plate 5. And a spacer 6 interposed in the central part of the. In this embodiment, the table body 4 and the oscillating plate 5 are mutually positioned by a pin 2a penetrating the central axis of the spacer 6, and they are integrally connected by a bolt 2b. .

The body 1 has a cylindrical first body portion 7 for attaching to a robot arm and the like, and a cylindrical first body portion 7 provided on the table 2 side (the lower end side of the first body portion 7) of the body 1. It has two body parts 8. The second body portion 8 has a cylinder 12 (described later) in which the upper surface side of the swing plate 5 of the table 2 is built in the first body 7.
The oscillating plate 5 and the spacer 6 are movably accommodated in the hollow portion of the A and 12B pistons 14 </ b> A and 14 </ b> B while being held at positions facing the tips of the pistons 14 </ b> A and 14 </ b> B.

The compliance mechanism 3 includes the second
Both front and back surfaces fixedly attached to the body portion 8 and arranged so as to be located between the table body 4 and the swing plate 5 accommodated in the second body portion 8, that is, in the middle portion of the spacer 6. An annular base plate 9 forming a parallel plane, and a plurality of steel balls 10 respectively arranged on the front and back sides of the base plate 9,
And an annular retainer 11 that rotatably holds the steel balls 10. The base plate 9 has an inner diameter smaller than the outer diameter of the swing plate 5,
It is a mode in which it is sandwiched between the rocking plate 5 and the table body 4 via the steel ball 10 and the retainer 11. The steel balls 10 are in rolling contact with the front and back surfaces of the base plate 9, the lower surface side of the rocking plate 5 and the upper surface side of the table body 4, respectively. 9 and the rocking plate 5 and the table body 4 are X and Y.
The shaft and the body 1 and the table 2 can be relatively displaced in the θ rotation direction around the central axis L. As a result, the positional error of the work or the like is absorbed.

Further, the compliance mechanism 3 has an origin returning mechanism for returning the positional displacement between the body 1 and the table 2 caused by the compliance function to the origin position. As shown in FIG. 2, the origin returning mechanism includes a pair of returning steel balls 22, 22 provided on the lower end side of the first body portion 7 and an upper surface side of the swing plate 5 of the table 2. A pair of ball receivers 23, 23 provided so as to be displaced integrally with the swing plate 5, and a first body portion 7.
, A pair of springs 24, 24 as elastic means for individually pressing the steel balls 22, 22 against the ball receivers 23, 23. The steel balls 22, 22 and the springs 24, 24 are arranged in the first body portion 7 so as not to interfere with the cylinders 12A, 12B, and
The steel balls 22, 22 are provided so as to be able to project from the end surface of the first body portion 7 so as to face the swing plate 5.
On the other hand, the ball receivers 23, 23 are provided on the upper surface of the rocking plate 5 at positions corresponding to the steel balls 22, 22, and the ball receivers 23, 23 have a conical receiving surface 23a,
23a, respectively, and the steel balls 22, 22 are press-fitted to the centers of the receiving surfaces 23a, 23a so that the positional displacement between the body 1 and the table 2 is returned to the origin.

Two cylinders 12, 12 are provided inside the first body portion 7 of the body 1, and when the body 1 and the table 2 are relatively displaced by the compliance mechanism 3, It is used to fix the table 2 in its displaced position and store the positional error of the work. The cylinders 12A and 12B are cylinder holes 13A and 1A provided in the first body portion, respectively.
3B, pistons 14A and 14B slidably fitted in the cylinder holes 13A and 13B, and the cylinder hole 1
Head cover 1 for hermetically closing the upper ends of 3A and 13B
5A, 15B and pressure chambers 16A, 1 between the head covers 15A, 15B and the pistons 14A, 14B.
6B is provided with a supply / exhaust port 17 for supplying compressed fluid, and by supplying the compressed fluid from the supply / exhaust port 17 into the pressure chambers 16A, 16B, the tips of the pistons 14A, 14B are shaken. It is adapted to be driven in the direction of the moving plate 5. The pressure chambers 16A and 16B of the cylinders 12A and 12B communicate with each other through a flow passage 18, and one cylinder 12B is configured to supply and discharge the compressed fluid through the flow passage 18. .

The pistons 14A, 14B are provided with, on their tip ends, movement restraining portions 19A, 19B in the shape of a convex curved surface that are tapered toward a point on the center axis,
When the pistons 14A and 14B move forward, the movement restraint portions 19A and 19B are mounted on the table 2 at the tops thereof.
The upper surface side of the rocking plate 5 is pressed against the base plate 9 to restrain the movement of the rocking plate 5.

Further, the outer peripheral surfaces of the pistons 14A and 14B are formed such that the upper and lower ends thereof have a smaller diameter than the other portions, and a plurality of steel balls 2 arranged in an annular shape in the smaller diameter portion.
0A, 20B and annular guides 21A, 2 for keeping the steel balls 20A, 20B in contact with the outer peripheral surfaces of the small diameter portions of the pistons 14A, 14B so as to be freely rotatable.
1B and 1B, respectively. Steel balls 20A, 2 above
0B is constantly in rolling contact with the outer peripheral surfaces of the small diameter portions of the pistons 14A, 14B and the inner peripheral surfaces of the guide members 21A, 21B.
The respective axes of B are prevented from tilting to prevent the movement restraining portions 19A and 19B at the tips of the pistons 14A and 14B from moving to prevent the swing plate 5 from being fixed at a fixed position.

Here, the movement restraining portion 19A of the piston 14A, as shown in FIG. 4, is a steel ball 20A arranged around the tip side of the piston 14A, and the piston 14A.
It is desirable to form a spherical surface having a radius R ₁ whose tip is in contact with the oscillating plate 5 with a point O ₁ on the central axis of the piston at the height of the contact point with the outer peripheral surface of A as the center. Normally, the rotational force (moment) T ₁ of the piston 14A when an external force in the horizontal direction acts from the oscillating plate 5 is the point O ₁
Occurs when a deviation width s ₁ occurs between the contact point A ₁ and the contact point A ₁ ,
When the external force F ₁ is applied to the table 2, it is expressed as T ₁ = F ₁ s ₁ , but in the case of FIG. 4, the point O ₁ is the contact point A between the oscillating plate 5 and the movement restraining portion 19A. Always located in the vertical direction of ₁ ,
Since the shift width s ₁ between the point O ₁ and the contact point A ₁ becomes 0, the rotational force T ₁ becomes 0. Therefore, even if the piston 14A
Even when the central axis of the contacting member is in contact with the vertical line on the oscillating plate 5 by α ₁ and the external force F ₁ is applied to the oscillating plate 5, the piston 14A receives a moment in the rotational direction. Since this does not occur, the piston 14A is prevented from rotating in the cylinder hole 13A, so that the rocking plate 5 can be reliably and stably fixed and its position can be correctly stored. Further, the movement restraining portion 19B of the piston 14B has the same structure as the movement restraining portion 19A and exhibits the same action and effect, and therefore the description thereof will be omitted. In the case of the one shown in FIG. 6, the rotational force T
₀ is a deviation width s ₀ between the point O ₀ and the contact point A _0, and when the external force F ₀ acts on the table t, the diameter of the piston P is d and the point O ₀ and the table t are distance h, when the inclination with respect to the table t of the piston P and alpha _0, the width _{s 0} misalignment between the point _{O 0} and the contact _{a 0} is _s 0 = (1 /
2 d-htan α), it is expressed by the formula T ₀ = F ₀ {(1/2) d-htan α}. In this case, since the possibility that s ₀ becomes 0 is extremely poor in design, the rotational force T ₀ acts on the piston P.

In the compliance unit having the above configuration, when the positional error between the workpieces is absorbed, the compliance mechanism 3 causes relative displacement between the body 1 and the table 2. At this time, Compressed fluid is supplied to the cylinders 12A and 12B to provide the piston 14
The displacement of the position is memorized by driving A and 14B to restrain the movement of the oscillating plate 5. In this case, body 1
The pair of cylinders 12A, 12
B is provided, the tilting of the central axis of each piston 14A, 14B of the cylinders 12A, 12B is suppressed, and convex curved movement restraining portions 19A, 19B are provided at the tips of the pistons 14A, 14B. 14A, 1
Since the oscillating plate 5 is pressed against the oscillating plate 5 on the central axis of 4B, a force is applied from the oscillating plate 5 to the movement restraining portions 19A and 19B of the pistons 14A and 14B in any of the XY directions. But not only does the piston not tilt,
Since the pistons 14A and 14B do not rotate around their central axes and the swing plate 5 of the table 2 can be pressed at a plurality of points to restrain the movement of the table 2, it is possible to prevent the movement of the table 2 from the conventional one. The table 2 can be securely fixed without any adverse effect in the case where the piston and the table are brought into surface contact with each other, whereby the relative positions of the body 1 and the table 2 are stably fixed, and The positional relationship can be accurately stored.

Although two cylinders are provided in the above embodiment, the number of cylinders is not limited to two and may be three or more. Also, in this embodiment, the pistons 14A, 14A
Steel balls 20A, 20B are provided on both upper and lower ends of the outer peripheral surface of B,
And a guide 21 for holding these steel balls 20A, 20B
A and 21B are arranged to prevent the axial lines of the pistons 14A and 14B from tilting. However, in these steel balls 20A and 20B and guides 21A and 21B, the pistons tilt within the cylinder holes. It is not always necessary to provide it when it can slide without performing.

In the above embodiment, the steel ball 22 is press-fitted onto the ball receiving surface 23 by the elastic force of the spring 24 in the origin returning mechanism.
As a means for press-fitting to, various elastic means other than springs,
Alternatively, various means such as an acting force of a compressed fluid can be used.

Further, the origin returning mechanism is not limited to the structure of the above-mentioned embodiment, but may be a structure utilizing the magnetic attraction force of the magnet as in the second embodiment shown in FIG. That is, instead of the steel ball 22, the ball receiver 23, and the spring 24 of the first embodiment, a pair of body side magnets 25A,
25B are arranged so that their magnetisms are opposite to each other, and holders 27A and 27B made of magnetic materials, respectively.
Via the fixing pins 28A and 28B made of a non-magnetic material, and at the positions facing the body side magnets 25A and 25B on the upper surface side of the swing plate 5 of the table 2, the tips of the body side magnets 25A and 25B. Table-side magnets 26A, 26 having magnetic poles of opposite polarities to the magnetic poles on the side
Similarly, B is a holder 30 made of a magnetic material.
Fixing pin 31 made of a non-magnetic material through A and 30B
It is attached by A and 31B. Therefore, the table-side magnets 26A and 26B are displaced together with the table 2. In this case, the cover 32 on which the upper plate of the first body portion 7 is formed and the fixing pins 28A and 28B are erected, and the swing plate 5 of the table 2 on which the fixing pins 31A and 31B are erected are , Each formed of a magnetic material. In the origin return mechanism of the second embodiment having the above configuration, the magnetic force lines are closed through the pair of magnets 25A and 26A facing each other, the other pair of magnets 25B and 26B, and the cover 32 and the oscillating plate 5 made of a magnetic material. Then, the opposing magnets are strongly attracted to each other magnetically, and the swing plate 5 returns to the original position. As a result, when the restraint of the swing plate 5 by the piston is released, the body 1 and the table 2 are The mutual positional deviation of is returned to the origin position. In the return-to-origin mechanism of the second embodiment described above, the lines of magnetic force passing through the plurality of pairs of magnets 26A, 26B and 26A, 26B form one closed loop. It is possible to use an attracting member such as a magnet that pulls back the body and the table to the original position by suction. Note that, in the second embodiment of FIG. 5, except for the configuration related to the origin return mechanism, it is basically the same as the first embodiment, so the same reference numerals are given to the main parts,
Descriptions thereof are omitted.

[0022]

According to the compliance unit of the present invention described in detail above, a plurality of cylinders are provided in the body, and a concave curved movement restraining portion is provided at the tip of each piston of the cylinders. Since the table can be restrained at multiple points, the table can be securely fixed without the adverse effects of the conventional surface contact between the piston and table, and the relative position of the body and table Can be stably fixed, and its positional relationship can be accurately stored.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the compliance unit of the present invention (position AA in FIG. 3).

FIG. 2 is a cross-sectional view of the compliance unit of the present invention at a position different from that in FIG. 1 (position BB in FIG. 3).

FIG. 3 is a bottom view of the first body portion of the compliance unit of the present invention.

FIG. 4 is an explanatory view of a movement restraint portion in the piston of the compliance unit of the present invention.

FIG. 5 is a cross-sectional view showing a second embodiment having an origin returning mechanism different from that of FIG.

FIG. 6 is an explanatory diagram when the tip of the piston is flat.

[Explanation of symbols]

1 body 2 tables 3 Compliance Organization 4 table body 5 rocking plate 9 base plate 10 steel balls 11 retainer 12A, 12B cylinder 14A, 14B piston 19A, 19B Movement restraint part 20A, 20B steel balls 21A, 21B guide 22 steel balls 23 ball receiver 25A, 25B Body side magnet 26A, 25B Table side magnet

Claims (7)

[Claims] 1. A compliance between a body and a table joined to each other with respect to X and Y axis directions that are orthogonal to their central axes and orthogonal to each other, and a θ rotation direction around the central axes. A plurality of cylinders are provided on the body with a compliance mechanism intervening, and the tips of the pistons are opposed to a swing plate that is integrally connected to the table and moves in the body by the compliance mechanism. The compliance unit is characterized in that a convex curved movement restraint portion that is in contact with the oscillating plate on the central axis of each piston is provided at the tip of each piston. 2. An annular base plate having front and back surfaces parallel to each other is fixed to the table side of the body, and the front and back surfaces of the base plate are connected to the table and the table through retainers respectively holding steel balls. The compliance unit according to claim 1, wherein the compliance mechanism is configured by being sandwiched by rocking plates that are integrally coupled. 3. A plurality of steel balls held by guides around the both ends of each piston to prevent tilting of the axis of the piston.
Compliance unit described in. 4. A steel ball placed in rolling contact with the movement restraint portion around the tip end side of the outer peripheral surface of each piston, and at the height of the contact point between the piston and the steel ball. The compliance unit according to claim 3, wherein the compliance unit is formed in a spherical shape centered on a point on the central axis of the piston. 5. An origin returning mechanism is provided between the body and the table for returning the mutual positional deviation caused by the compliance mechanism to the origin position. Compliance unit described in. 6. The origin return mechanism, a steel ball provided on either the body or the table, a ball receiver provided so as to be displaced together with the other, and the steel ball The compliance unit according to claim 5, wherein the compliance unit comprises a plurality of pairs of elastic means to be press-fitted to the. 7. The origin returning mechanism is provided so as to be displaced together with the body and the table, and is constituted by a suction member for returning the body and the table to the origin position by magnetically attracting each other. The compliance unit according to claim 5, wherein