JPH0368629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive device for a movable body.

Configuration of conventional example and its problems When driving a movable body having a guide means by a drive means that has its own drive direction guide means and thrust generation function like a conventional linear pulse motor, the movable part of the linear pulse motor and The movable body is rigidly coupled, and the deflection of the movable unit in a direction perpendicular to the feeding direction, that is, the radial deflection, is faithfully transmitted to the movable body. In a combination of only a movable body and its guide means, the straight movement accuracy of the movable body is good, but
By combining a linear pulse motor (hereinafter abbreviated as L/P), the linear movement accuracy of the movable body deteriorates due to the above-mentioned reasons. In recent years, air bearing-type linear guides have been used in places where high linear accuracy is required for movable objects, but while air bearings provide higher linear accuracy than rolling guides or sliding guides, they have low rigidity. Even a slight radial deflection of L and P can greatly deteriorate the straight-line accuracy of the movable body.
The value of using air bearings was often halved.

In order to solve these problems, the following two methods have been considered in the past. The first method is L.
The second method is to connect the movable bodies of P and the movable bodies with an elastic body, and the second method is to connect them with a wire to which initial tension is applied in the driving direction. However, although both the first and second methods can lower the stiffness in the radial runout direction compared to the stiffness in the drive direction, it is difficult to make the difference between the two stiffnesses very large.
They had the fundamental drawback that if one side had an advantage, the other would be at a disadvantage.

The first method implemented using, for example, an air bearing type guide will be described with reference to FIGS. 1 and 2. 1 is a known linear air bearing; 2 is a guide body having a rectangular cross section; 3 is a movable body configured to surround the guide body 2; Although not shown, high-pressure air is pumped between the movable body 3 and the guide body 2, and the movable body 3 floats from the guide body 2 without contacting it, and is movable only in the direction of arrow A. 4 is a leaf spring having an arcuate portion 5, and a screw 7 at the flat portion 6;
It is fixed to the movable body 3 by. Further, the leaf spring 4 has a screw 9 at a bent part 8 formed at the tip of the circular arc part 5.
Movable part 11 of L・P10 (driving body) known by
is fixed. L/P10 has a linear structure of a known rotary pulse motor, and is composed of a movable part 11 having teeth 12 around which a coil is wound (not shown) and a fixed part 14 having teeth 13 formed thereon. . Due to the magnetic attraction force generated between the teeth 12 and 13 by energizing the coil,
Thrust in the direction of arrow A is generated. At this time, the magnetic attraction force generated about 10 times the thrust forces the teeth 12 and 1.
4 is implanted in the movable part 11 so that 3 does not come into contact with it.
Four wheels 1 rotatably supported on a book shaft 15
6 is provided. Further, since the wheel 16 is vertically restricted in position by the stepped portion 17 provided on the fixed portion 14, the movable portion 11 has a degree of freedom of movement only in the direction of arrow A. The leaf spring 4 has relatively high rigidity in the feeding direction, that is, the direction of arrow A, and has a relatively large rigidity in the direction perpendicular to arrow A, that is, in the direction of arrows D and E.
Since the circular arc portion 5 provided on the leaf spring 4 is easily bent, the rigidity is relatively low. Therefore, even if the movable part 11 radially swings in the direction of arrow B and swings in the directions of arrows C, D, and E due to warping, bending, twisting, etc. of the fixed part 14 of L/P 10, the movable part The forces applied to 3 in the directions of arrows B, C, D, and E are reduced. However, in order to ensure that the deflection in the directions of arrows B, C, D, and E has almost no effect on the straight-line accuracy of the movable body 3, the rigidity in the directions of arrows B, C, D, and E must be extremely low. However, this has the basic drawback that the rigidity in the direction of arrow A also decreases, making it difficult to faithfully transmit the motion of the movable portion 11 to the movable body.

Next, the second method will be explained based on FIG. The difference between this method and the first method is that pins 18a, 18 are attached to the movable body 3 instead of the leaf spring 4.
b is implanted, a wire 19 is stretched by applying initial tension between the pins 18a and 18b, and a pin 18c implanted in the movable portion 11 is fixed to this wire 19. Even in such a configuration, the lower the initial tension of the wire 19, the more the arrows B, C, D, and E
This method has the same basic drawback as the first method in that the stiffness in the direction of arrow A is reduced, but the stiffness in the direction of arrow A is also reduced.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks, and the present invention is directed to solving the above-mentioned drawbacks of the conventional art.When the drive body has runout in the direction perpendicular to the feeding direction, the runout is transmitted to the movable body and deteriorates the linear accuracy or rotational accuracy of the movable body. It is an object of the present invention to provide a drive device that can faithfully transmit the movement of the drive body in the feeding direction to the movable body.

Composition of the Invention In order to achieve the above object, a movable body driving device of the present invention includes a movable body guided by a first guide means that allows movement only in a predetermined direction, and a movable body guided by a first guide means that allows movement only in a predetermined direction, and a movable body guided by a first guide means that allows movement only in a predetermined direction. a housing that is guided by a second guide means that allows movement only in the direction of the movable body, and a drive body that drives the movable body; and a hole that is fixed to the movable body and has two opposing surfaces perpendicular to the predetermined direction. and a shaft portion that is fixed to the driving body and has a plane facing parallel to the vertical opposing surface, and a spherical body is provided between the vertical opposing surface and the plane parallel to the opposing surface. It is configured to hold the following.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings. Incidentally, the same parts as in the conventional example are indicated by the same reference numerals, and detailed explanation thereof will be omitted. First, a first embodiment in which an air bearing is used to guide a movable body will be described with reference to FIGS. 4 to 8. In FIGS. 4 to 6, 20 is a square shaft installed perpendicularly to the movable part 11 of L/P 10, and 21 is fixed to the movable body 3 of the linear air bearing 1 at right angles by screw 3 and screw 22. This housing 21 is a roughly U-shaped housing.
A plate 23 is fixed to an opening on one side of the housing with screws 24. Reference numeral 25 denotes a steel ball loosely fitted into a pair of opposing side plates of the prismatic cylindrical retainer 27;
The square shaft 20 is held in contact with the square shaft 20 which is loosely fitted into the square hole 26 formed by the plate 23 and the retainer 27.
28 is a coil spring, one end of which is inserted into the blind hole 29a on the inner surface of the retainer 27, and the other end is inserted into the blind hole 29 on the outer surface of the square shaft 20.
b, and the retainer 27 is supported by this coil spring 28 while maintaining an appropriate distance between the square shaft 20 and the square hole 26. Therefore, the cage 27 has a square shaft 20 formed by steel balls 25.
The steel ball 25 can easily and flexibly follow rolling motion in all directions between the square hole 26 and the spring 2.
8 and the retainer 27 at a predetermined position between the square shaft 20 and the square hole 26. Also, the square shaft 20 and the square hole 26
The dimensions of each element are set so that there is a negative clearance between the steel ball 25 and the steel ball 25.

These can be easily assembled by attaching the retainer 27 holding the steel balls 25 to the square shaft 20 via the spring 28, fitting the square shaft 20 into the substantially U-shaped housing 21, and then attaching the plate 23. be. Note that the spring 28 can be assembled so that the retainer 27 is located in the center of the gap between the square shaft 20 and the square hole 26.
can be omitted. In addition, the retainer 27
The purpose of the spring 28 is to hold the steel ball 25 in place during assembly. Therefore, the movable part 11
The movable part 3 includes a square shaft 20, a steel ball 25, and a housing 2.
1 through the plate 23. As can be seen from the above structure, in the moving direction of the movable part 11, that is, in the direction of arrow A in FIG. 4, a force is applied in a direction that compresses the steel ball 25, so that it has a large rigidity. To put it bluntly, the factors that reduce the rigidity are the steel balls 25 and the square shaft 2.
0 and the square hole 26, the rigidity can be easily increased if the fitting of the former three is made to have a negative clearance, that is, by increasing the pressurization. On the other hand, the steel ball 25 is displaced in the directions of arrows B and C in the figure by the square shaft 20.
outer planes 20a, 20b and inner plane 2 of the square hole 26
By rolling 1a and 23a, it can be displaced without resistance. Furthermore, for the displacement in the directions of arrows D and E in the figure, for example, in the D direction, the displacement can be made with almost no resistance as shown in FIG. For example, the width W of the square shaft 20 is 10 mm, the diameter of the steel ball 25 is 3 mm,
When the pressurization amount is 3 to 5 μm per steel ball, the ball can be displaced with almost no resistance if the angular axis θ is in the range of ±4 to 6 degrees in FIG. The same applies to the E direction. Therefore, according to this configuration, the movable part 11 can be faithfully connected to the movable body 3.
Moreover, since the radial deflection of the movable part 11 in the direction of arrow B and the deflection in the directions of arrows C, D, and E are hardly transmitted to the movable body 3, the original linear accuracy of the movable body 3 is not affected in any way. A drive device with extremely high precision without any damage can be realized with a very simple configuration.

As is clear from the first embodiment described above,
The object of the present invention is achieved by the square shaft 20, the square hole 26, and the steel balls 25 inserted between the two sets of opposing planes that they constitute, and the square shaft is used as a movable body.
It goes without saying that the object of the present invention can be achieved even if a square hole is provided in the movable part. Furthermore, this object can also be achieved by the configuration of the second embodiment shown in FIGS. 8 and 9. The second embodiment will be described below based on FIGS. 8 and 9. That is, in this embodiment, four steel balls 25 are provided between each of the two opposing planes constituted by the square shaft 20 and the square hole 26, a total of eight steel balls 25. This configuration increases the rigidity in the direction of the arrow A and is suitable for highly accurate motion transmission. However, the rigidity against displacement in the directions of arrows D and E also increases, but the displacement components in the directions of arrows D and E are
Since it is small compared to the displacement component in the direction, there is often no practical problem. If the displacement in the direction of arrow D is relatively large, a plurality of steel balls 25 should be arranged only in the direction of arrow F in FIG. 9, and if the displacement in the direction of arrow E is comparatively large, a plurality of steel balls 25 should be arranged only in the direction of arrow I. Good. Further, the driving means need not be a linear pulse motor, but may be one that is allowed to move only in the driving direction and generates a thrust, or one that can be given a thrust from the outside.

Although the case has been described above in which both the movable part 11 and the movable body 3 move in a straight line, they may also move in rotation. An example of this will be explained in FIG. Although not shown, a driven shaft 30 is rotatably supported by, for example, an air bearing and rotates with high precision. At the end of this shaft 30, two square shafts 31 and 32 similar to the square shaft 20 are provided. It is planted. 33
Although not shown, is a driving shaft that is rotationally driven by a motor or the like. Reference numerals 34 and 35 designate cages similar to the cage 27, and are supported by the square shafts 31 and 32 by coil springs similar to the coil spring 28, although not shown. However, the steel balls 25 are attached only to the cage 34 side. 36 and 37 are housings having substantially U-shaped structural parts 38 and 39, respectively. The plates 40 and 41 are fixed to the housings 36 and 37 by screws 42 and 43, respectively, and are combined with the U-shaped structures 38 and 39 to form square holes 44 and 45 similar to the square hole 26. There is. The housings 36, 37 are fixed to the shaft 33 by screws 46, 47. Further, the retainers 34 and 35 are fixed to a plate 49 by screws 48 and connected to each other. With the above configuration, the rotational power is transferred to the housing 3.
6 is transmitted only to the square shaft 31 via the steel ball 25. The square shaft 32, cage 35, housing 37, etc. are provided only to maintain suspension during rotation, and the cage 34 is also connected to the cage 35 through a plate 49.
Since the retainer 34 is connected to the retainer 34, the suspension of the retainer 34 is maintained, and even if the shaft 33 rotates at high speed, there is no problem in its operation. Therefore, even if the driving shaft 33 is bent in the directions of arrows H (radial direction) and arrow 1 (thrust direction) in FIG. Rotational motion can be reliably transmitted via the ball 25.

Effects of the Invention As described above, the present invention has a housing part that is fixed to a movable body and has a hole having two opposing surfaces perpendicular to a predetermined direction, and a housing part that is fixed to a movable body and has two opposing surfaces that are perpendicular to a predetermined direction. and a shaft portion having planes facing parallel to each other, and configured to hold a sphere between the perpendicular opposing surface and a plane facing parallel to the opposing surface, the driving body is movable. We have created an extremely high-precision drive device that faithfully transmits motion to the body, and since almost no radial runout of the drive body is transmitted to the movable body, it does not impair the original guiding accuracy of the movable body. This can be realized with a simple configuration. Therefore, even if a guide with low rigidity, such as an air bearing, is used, the originally high guiding accuracy is not impaired in any way. A similar effect is also achieved in the transmission of rotational motion. Furthermore, in conventional configurations, it was necessary to assemble the movable body and the driving body so that the directions of motion of the movable body and the driving body were precisely parallel for linear motion, and that the two axes aligned accurately for rotary motion. However, this configuration can easily absorb these assembly errors, and therefore can be easily assembled in a short time without requiring any skill.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a first conventional example, FIG. 2 is a side view of the same, and FIG. 3 is an exploded perspective view of a second conventional example.
FIG. 4 is an exploded perspective view of the first embodiment of the present invention;
The figure is a partially cutaway side view of the same part, and Figure 6 is X-X of Figure 5.
7 is an explanatory diagram of the same operation, FIG. 8 is a supplementary explanatory diagram, FIG. 9 is a side view of the main part of the second embodiment of the present invention, and FIG. 9 is a YY sectional view of FIG. 8. , FIG. 10 is an exploded perspective view of essential parts of a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Straight air bearing, 2... Guide body, 3... Movable body, 10... L/P, 11... Movable part, 14...
... Fixed part, 20 ... Square shaft, 21 ... Housing,
23...Plate, 25...Steel ball, 26...Square hole, 27
... Cage, 28 ... Coil spring, 30 ... Driven shaft, 31, 32 ... Square shaft, 33 ... Driving shaft, 3
4, 35... Cage, 36, 37... Housing, 40, 41... Plate, 44, 45... Square hole.

Claims (1)

[Scope of Claims] 1. A movable body guided in a predetermined direction by a guide means, a driving body guided in substantially the same direction as the predetermined direction, and a connecting means for connecting the movable body and the driving body. A driving device for a movable body, the connecting means comprising: a rectangular cylindrical housing portion having parallel opposing surfaces on its inner wall surface; a shaft portion inserted into the housing portion; and an inner portion of the housing portion. It is composed of a holder interposed between a wall surface and the shaft, and a sphere disposed in a hole in a surface of the holder that is in contact with the opposing surface, and a ball inserted into the housing part is inserted into the shaft. a flat surface facing the opposing surface of the housing portion is formed; the sphere is disposed in pressure contact between the opposing surface of the housing portion and the flat surface of the shaft portion; and the housing The part is fixed to one of the driving body or the movable body so that the opposing surface thereof is perpendicular to the predetermined direction, and the shaft part is fixed to the other of the driving body or the movable body. A drive device for movable bodies.