JP2796109B2 - Wave gear wave generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wave gear, and more particularly, to a wave generator for a wave gear.

2. Description of the Related Art Wave gears are well known.
38-9157. Such a conventionally well-known wave gear has a circular spline formed of a rigid cylindrical member and having internal teeth formed therein, and an external tooth formed on a thin ring portion formed of a flexible material provided inside the spline. And a flexspline provided inside the flexspline, and flexing the flexspline into an elliptical shape so that the outer teeth of the flexspline partially mesh with the inner teeth of the circular spline, and the elliptical shape is reduced. A rotating wave generator. In this wave gear,
Since the number of teeth of the circular spline and the number of teeth of the flexspline are different, the elliptical rotation by the wave generator can be greatly reduced at a ratio corresponding to the difference in the number of teeth between the two splines. Therefore, there is an advantage that a large reduction ratio can be obtained with a small number of mechanical elements, and it is widely used for robots, precision machines, and the like.

In a gear device including this wave gear, it is desirable that the backlash be as small as possible from the viewpoint of power transmission. At this point, the wave gear uses a small number of gears, so that the backlash can be considerably reduced as compared with the conventional speed reducer. However, there is still room for improvement in this backlash in current wave gears.

Generally, wave gears can be divided into two types according to their shapes. One is a cup-type wave gear in which a flexspline is axially extended from a portion where the flexspline meshes with the circular spline and is formed in a cup shape, and the entire wave gear is formed in a cylindrical shape. The other one is
At least two thin circular splines formed short in the axial direction are juxtaposed, one of the splines has the same number of teeth as the inner flexspline and the other has a different number of teeth, and a ring shape is formed inside both circular splines. The flat wave gear is provided with the formed flexspline and formed in a thin flat shape as a whole.

Although cup-shaped wave gears have the disadvantage of having larger dimensions, they have the advantage of having a smaller number of parts.In addition, the outer teeth of the flexspline face the inner teeth of the circular spline outward from the bottom of the cup. There is also an advantage in that the meshing portion spreads in a slanting manner and is inclined and meshes, so that a preload is applied to the meshing portion to reduce backlash.

On the other hand, in the case of a flat type wave gear, since the flexspline is cylindrical, a preload like a cup type wave gear cannot be expected. Therefore, from the viewpoint of backlash, a cup-shaped wave gear is more desirable. However, even with a cup-type wave gear, the preload is not so large as expected, and if there is further wear or the like, the preload decreases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a wave gear capable of providing a sufficient preload at a portion where a flex spline meshes with a circular spline to greatly reduce backlash.

Means for Solving the Problems To achieve such an object, according to the present invention, an elliptical forming member of a wave generator for bending a flexspline of a wave gear into an ellipse is provided by a four-point support system. An ellipse to be added to the flexspline is defined, and the ellipse is characterized by a greater ellipticity than a case where the flexspline is bent outward at two points on the long axis.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the principle of the wave gear 1.
The wave gear 1 has a circular spline 2 formed of a rigid material and formed in a cylindrical shape and formed with internal teeth, and external teeth are provided inside the circular spline 2 and formed on a thin ring portion made of a flexible material. Flex Spline 3
And a wave generator 4 fitted inside the flexspline and bent into an elliptical shape. The wave generator 4 includes an inner elliptical cam plate 5 as an elliptical forming member, and a ball bearing 6 fitted on the outer periphery of the cam plate 5 and bent into an elliptical shape. Outer ring 7 of bearing 4
Are fitted to the flexspline 3.

Since the flexspline 3 is bent into an elliptical shape by the wave generator 4, the flexspline 3 meshes with the circular spline 2 at two points diametrically opposite each other at a part thereof on both sides thereof. In FIG. 1, two points in the directions of arrows A and B are engagement points. Further, since the wave generator 4 has the ball bearing 6, when the cam plate 5 of the wave generator 4 rotates, the flexspline 3 is rotated only by its elliptical shape, and is not directly rotated by the cam plate. . The number of teeth of the flexspline 3 is 2n (n is a positive integer) less than the number of teeth of the circular spline (first
In the figure, the number is four less than the circular spline).

The operation of the wave gear 1 will be described with reference to FIGS.
This will be described with reference to FIG. When the cam plate 5 of the wave generator 4 is at the position shown in FIG. 2 (a), the tooth groove 8 of the circular spline 2 is located on the long axis of the ellipse of the flexspline 3.
Are in mesh with the teeth 9 of the flexspline 3. When the cam plate 5 is rotated 90 degrees as shown in FIG. 2B, the ellipse of the flexspline 3 rotates, and the meshing point of the flexspline 3 moves according to the movement of the long axis of the ellipse, and the tooth space is increased. 8 leaves tooth 9. As shown in FIG. 2 (c), when the cam plate 5 rotates by 180 degrees, the tooth grooves 8 and the teeth 9 re-engage, but the position is the difference in the number of teeth (four in the example shown, ie, n = 2). , That is, n sheets (two sheets in the illustrated example). Then, as shown in FIG. 2 (d), when the cam plate 5 rotates 360 degrees, the tooth gap 8 and the teeth 9 are shifted by the difference in the number of teeth (four in the illustrated example). Thus, a large reduction ratio can be obtained by extracting the movement in which the meshing position is sequentially shifted as an output.

There is a flex-spline 3 formed in a cup shape extending in a direction perpendicular to the plane of the paper of FIG. 1 and on one side. This is a so-called cup-type flexible meshing gear device, which has the advantage of a simple structure. However, since the flexspline is formed in the shape of a cup, there is a drawback that the entire apparatus is inevitably large in size and occupies a large space.

In order to eliminate such disadvantages, as shown in FIG.
A first circular spline 11 and a second circular spline 12, which is coaxially juxtaposed with the spline and has a different number of teeth, coaxially inside the two circular splines and partially meshing with the two splines. A ring-shaped flexspline 13 having the same number of teeth as the arranged first circular spline, and flexing and flexing the flexspline 13, partially meshing with each internal tooth of both circular splines and deforming into an elliptical shape A wave gear 10 including a wave generator 14 for rotating an elliptical shape of a flexspline is known. The wave gear 10 has two circular splines 11 and 12 arranged side by side as shown in the figure, and the flex spline 13 is also formed in a ring shape instead of a cup shape, and the entire device is formed flat and thin. Therefore, it is called a flat type wave gear.

Also in this flat type wave gear, as shown in FIG. 1, the wave generator 14 deforms the flexspline 13 to rotate its shape, and the rotation causes the wave spline 13 to rotate as shown in FIG.
As shown in (d), the point of engagement between the flexspline 13 and the first and second circular splines 11, 12 rotates. As described above, the first circular spline 11 has the same number of teeth as the flex spline 13 and the flex spline 13
Although there is no relative rotation between the two, the second circular spline 12 and the flex spline 13
As shown in FIGS. 2A to 2D, both splines rotate relatively. Accordingly, the first circular spline 11 and the second circular spline 12 rotate relative to each other via the flex spline 13. Utilizing this, the wave generator 14
Provided with an input shaft, one of the circular splines is fixed, and the other of the circular splines is provided with an output shaft, a large reduction ratio can be obtained between the input shaft and the output shaft.

In both the so-called cup-type wave gear and the flat-type flexible meshing gear device, it is desirable that the backlash in meshing between the circular spline and the flexspline be small. In this respect, the cup-shaped wave gear has the disadvantage of being large, but since the flexspline extends in a cone shape from the bottom of the cup, the outer teeth of the flexspline are inclined and mesh with the inner teeth of the circular spline. This has the advantage that the preload is applied to the meshing portion and the backlash is reduced as much as possible.

On the other hand, in a flat type wave gear, since a flexspline is cylindrical, a preload like a cup type wave gear cannot be expected. Therefore, from the viewpoint of backlash, a cup-shaped wave gear is more desirable. However, even with a cup-type wave gear, the preload is not so large as expected, and if there is wear or the like, the preload decreases.

In the present invention, as shown in FIG. 4, the cam plate 5 as the elliptical forming member of the wave generator 4 (14)
The degree of the ellipse is increased by the point support method, and the ellipse is shaped to give a superellipse to the flexspline. here,
The "four-point support system" used in this document refers to an ellipse formed by applying a pulling force outward at two points on the long axis as seen in the wave generator 4 in FIG. This "four-point support system" is used to refer to the formed ellipse.
Mainly refers to a method of forming an ellipse by four balls. In particular, in the present invention, an ellipse of a flexspline is formed by the four-point support method, and a shape with an increased degree of the ellipse is given to a ring-shaped flexspline portion. This will be described with reference to FIG.

In FIG. 4, the outline shown by the solid line shows the shape of the wave generator 4 (14) of the present invention as an elliptical forming member at the time of production. This wave generator is formed by combining the cam plate 5 and the ball bearing 6 as described above. Using this wave generator 4 (14), flex spline 3 (1
When 3) is deflected, the four balls 16 to 19 serving as a reference to form an ellipse are deformed so as to pull the flexspline portion at that position radially outward. In this case, it is to be understood that the balls 16 to 19 schematically show elements for deriving an elliptical shape, and do not show balls forming an actual wave generator.

When the flexspline is given an elliptical shape as described above, the flexspline can be engaged with the circular spline by increasing the degree of the ellipse as indicated by the broken line. Thereby, for example, in a small arc portion between the balls 16 and 17, the tooth surfaces of the outer teeth of the flexspline are respectively opposed to the tooth surfaces of the inner teeth of the circular spline on both sides of the long axis of the wave generator. Engage and preload at that point. The same applies to a small arc portion between the ball 18 and the ball 19.

Effect of the Invention According to the present invention, as described above, a member that forms a wave generator and forms a flexspline in an elliptical shape has its ellipse formed by a four-point support method. By engaging the circular spline with increasing ellipticity, a preload is applied to the tooth surfaces of the flexspline and the circular spline, thereby providing a wave gear capable of eliminating backlash.

In addition, since a four-point support system is used to deform the flexspline, the force required to deform the flexspline into an elliptical shape is smaller than that of a conventional two-point support type wave gear that pulls on the long axis with two forces. It is dispersed so that the load on the ball of the bearing can be reduced.

The member for forming the flexspline into an elliptical shape is 4
Any wave generator may be used as long as the degree of the ellipse can be enhanced by the point support method, and if it consists of a cam plate and a ball bearing like a general wave generator, it is a cam plate. Or a ball bearing.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a wave gear, and FIGS. 2 (a) to 2 (d).
Is an explanatory view showing the operation of the wave gear, FIG. 3 is a sectional view of the flat wave gear, and FIG. 4 is a front view of the wave generator according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Wave gear 2 ... Circular spline 3 ... Flex spline 4 ... Wave generator 5 ... Cam plate 6 ... Ball bearing 10 ... Flat type wave gear 11 ... First circular spline 12 … Second circular spline 13… Flex spline 14… Wave generator 16-19… Ball for supporting four points

Claims (1)

(57) [Claims] 1. A circular spline made of a rigid cylindrical member and having internal teeth formed therein, and a flexspline provided inside the circular spline and formed of a flexible material and having external teeth on a thin ring portion. A wave generator that is provided inside the flexspline and that flexes the outer teeth of the flexspline into an elliptical shape of the flexspline so as to partially mesh with the inner teeth of the circular spline, and rotates the elliptical shape. In the wave gear, the number of teeth of the circular spline and the number of teeth of the flexspline are different, and the elliptical rotation by the wave generator can be greatly reduced corresponding to the difference in the number of teeth of the two splines. The elliptical forming member of the vessel defines the ellipse to be given to the flex line by a four-point support system,
A wave generator for a wave gear, wherein the ellipse has an increased ellipticity as compared with a case where the flexspline is bent outward at two points on a long axis.