JPH05141485A - Cup type wave motion gear device having low speed reduction ratio - Google Patents

Abstract

PURPOSE:To provide structure which can achieve the reduction ratio lower than before in a cup-type wave motion gear device. CONSTITUTION:A gear type cup-type reduction gear 1 is composed of a flexible internal gear 2, a similarly flexible cup-type external gear 3, and a wave motion generator 4. The rigid cam plate 4a is equipped with a large elliptic part 41 and a small elliptic part 42, and by these the internal gear 2 and the external gear 30 gear with each other in the positions of both ends in radial direction, being caught in radial direction in the state of phase shift of 90 deg.. Since the quantity of relative flexure between the internal gear 2 and the external gear 3 can be enlarged, the difference between the numbers of these teeth can be enlarged by that amount. Therefore, the reduction ratio can be lowered as compared with before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cup-type wave gear device, and more particularly to a cup-type wave gear device having a structure capable of realizing a reduction ratio lower than that of a conventional one.

[0002]

2. Description of the Related Art As a cup type wave gear device, a gear type cup type wave gear device is generally known. This cup-type wave gear device is basically composed of an annular rigid internal gear, a flexible cup-type external gear arranged inside this, and a wave generator attached inside this. .. The cup-shaped external gear is bent into an elliptical shape by the wave generator, and the positions of both ends of the major axis mesh with the rigid internal gear. When the wave generator is rotated, these meshing positions move in the circumferential direction, so that relative rotation is generated between the rigid internal gear and the cup-shaped external gear according to their tooth number difference. Normally, since the rigid internal gear is fixed, the decelerated rotation is output from the cup-shaped external gear.

The speed reduction ratio i in this cup type wave gear device is obtained by the following equation. i = 1 / R = (Zf−Zc) / Zf where R: speed ratio Zf: number of teeth of cup type external gear Zc: number of teeth of rigid internal gear

Here, normally, the number of teeth Zc of the internal gear is set to be two more than the number of teeth Zf of the external gear (Zc = Zf + 2). Therefore, the reduction ratio i is expressed as i = −2 / Zf. Therefore, in order to reduce the reduction ratio i, the difference in the number of teeth between the external gear and the internal gear may be increased. (In this specification, "to reduce the reduction ratio i" means to reduce the value of the speed ratio R.)

[0005]

However, the bending amount of the cup-type external gear has an upper limit, and due to this restriction, the difference in the number of teeth between the external gear and the internal gear is usually four. For this reason, the limiting speed ratio of this type of wave gear device is R = 50.
However, it is difficult to make it smaller than this.

In view of this point, an object of the present invention is to propose a cup type wave gear device capable of realizing a lower reduction ratio.

[0007]

In order to solve the above-mentioned problems, in the cup type wave gear device of the present invention, both the cup type external gear and the internal gear are flexible gears, and these are provided by a wave generator. The structure that bends in the radial direction is used.

In the case of the type in which the external gear and the internal gear are bent into an elliptical shape by the wave generator so that the two are engaged with each other at two points, the external gear and the internal gear are bent into an elliptical shape with a phase difference of 90 degrees. Then, the both ends of the long axis of the external gear may be meshed with the both ends of the short axis of the internal gear.

The present invention can be similarly applied to a friction engagement type cup type wave gear device.

[0010]

In the cup type wave gear device of the present invention, both the internal gear and the external gear are bent by the wave generator. By bending both gears in this way, the relative amount of bending can be increased compared to the conventional one, and the difference in the number of teeth between the internal gear and the external gear can be increased by that amount,
The reduction ratio can be lowered.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 3.

The example shown in the drawing is an example in which the present invention is applied to a general gear type cup type wave gear reducer. The basic structure of the cup-type wave gear reducer 1 of this example is the same as the conventional one, and is composed of an internal gear 2, a cup-type external gear 3, and an elliptical wave generator 4.

In the present embodiment, the internal gear 2 is composed of a rigid annular portion 2a and a thin-walled flexible cylindrical portion 2b extending from this end face. This flexible cylindrical portion 2b
In the portion of the inner peripheral surface 2c closer to the tip side than the center,
Inner teeth 2d are formed in the circumferential direction. The cup-shaped external gear 3 is composed of a thick boss portion 3a forming a cup-shaped bottom surface and a thin-walled flexible cylindrical portion 3b forming a peripheral surface portion from the cup-shaped bottom surface. ing. External teeth 3d are formed in the circumferential direction on the outer peripheral surface 3c on the tip side of the flexible cylindrical portion 3b. The cup-shaped external gear 3 is configured so that the external teeth 3d face the internal teeth 2d.
Is positioned inside.

On the other hand, the wave generator 4 is composed of a rigid cam plate 4a having an elliptical contour and two ball bearings 4b and 4c fitted on the outer peripheral surface thereof. The rigid cam plate 4a includes a large elliptical portion 41 and a small elliptical portion 42 which are arranged at intervals in the direction of the axis 1a.

As can be seen from FIG. 3, the phases of the large elliptical portion 41 and the small elliptical portion 42 are 90 degrees out of phase,
Moreover, the small ellipse portion 42 is set to have a size that is inscribed in the large ellipse portion 41. Here, the cross section shown in FIG. 1 is the minor axis position of the large elliptical portion 41 and the major axis position of the small elliptical portion 42, and the cross section shown in FIG. 2 is a cross section orthogonal thereto. Ball bearings 4b and 4c are fitted on the outer peripheries of the large elliptical portion 41 and the small elliptical portion 42, respectively.

As shown in FIGS. 1 and 2, in the wave generator 4 having this structure, the large elliptical portion 41 is fitted into the inner peripheral surface 2c on the tip side of the internal gear 2, and the small elliptical portion 42 is the external gear. It is fitted on the back surface of the outer tooth 3 of FIG.

In the speed reducer 1 having this structure, as shown in FIG. 1, at the cross-sectional position where the short axis of the large elliptical portion 41 and the long axis of the small elliptical portion 42 of the wave generator 4 are located,
The external gear 2 is flexed inward in the radial direction, and the internal gear 3 is flexed outward in the radial direction, whereby only the portion of the internal teeth 2d and the portion of the external teeth 3d located at this portion mesh with each other. Is set In other portions, as can be seen from FIG. 2 showing a cross section orthogonal to the cross section shown in FIG. 1, the inner teeth 2d and the outer teeth 3d are in a separated state.

In use, for example, the annular portion 2a of the internal gear 2 is attached to a stationary member such as a case, and high speed rotation is input to the wave generator 4. In this way, the large elliptical portion 41 and the small elliptical portion 42 of the wave generator 4 are separated by 9
It rotates at high speed while maintaining the phase shift of 0 degree. Along with this high speed rotation, the meshing position of the inner teeth 2d and the outer teeth 3d also moves in the circumferential direction. As a result, the rotation reduced by the reduction ratio according to the tooth number difference between the internal gear and the external gear is obtained from the cup-type external gear 3.

In the gear type cup-type speed reducer 1 of the present embodiment constructed as described above, both the internal gear and the external gear are made flexible, and both are flexed so as to partially mesh with each other. There is. Therefore, the relative amount of bending can be increased as compared with the case where only the cup-shaped external gear is bent as in the conventional case. For this reason, the difference in the number of teeth between the two gears can be made large, and the reduction ratio can be made smaller than in the conventional case. For example, this difference in the number of teeth is 4,
It is possible to realize a harmonic reducer with a low reduction ratio by using about 6 or 8 sheets.

[0020]

As described above, in the wave gear device of the present invention, both the outer annular member and the cup-shaped member, which are the constituent elements, are made flexible, and both of them are radially moved by the wave generator. It is adapted to be partially engaged by bending. Therefore, according to the present invention, the relative amount of bending can be increased as compared with the case where only one annular member is bent. Therefore, the difference in the circumferential length between the outer annular member and the cup-shaped member, and the difference in the number of teeth between the internal gear and the external gear in the case of a gear device can be increased by that amount, and the reduction ratio can be made lower than in the conventional case. ..

[Brief description of drawings]

FIG. 1 is a half cross-sectional view showing a gear type cup-type speed reducer according to an embodiment of the present invention.

FIG. 2 is a half cross-sectional view showing a cross section of the gear type speed reducer at a position orthogonal to the cross section of FIG.

FIG. 3 is an explanatory view showing a bending state of an internal gear and an external gear in the speed reducer of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cup type speed reducer 2 ... Internal gear 2b ... Flexible cylindrical portion 2d ... Internal teeth 3 ... Cup type external gear 3b ... Flexible cylindrical portion 3d ... External tooth 4 ... Wave generator 41 ... Large elliptical portion 42 ... Small elliptical portion

Claims (3)

[Claims] 1. A flexible outer annular member, a flexible cup-shaped inner member disposed inside the flexible outer annular member, and the outer annular member and the cup-shaped inner member which are bent in the radial direction to form the cup. Between the outer annular member and the cup inner member by partially engaging the outer peripheral surface of the mold inner member with the inner peripheral surface of the outer annular member and moving the engaging position in the circumferential direction. And a wave generator for generating relative rotational motion in the cup type wave gear device having a reduced speed ratio. 2. The outer ring member according to claim 1, which is an internal gear, and the cup-shaped inner member, which is an external gear,
A cup-type wave gear device having a reduced speed ratio, wherein the meshing position of the internal gear and the external gear is moved in the circumferential direction by the wave generator. 3. The wave generator according to claim 2,
The internal gear and the external gear are bent in an elliptical shape with a phase difference of 90 degrees so that the internal teeth at both ends of the minor axis of the internal gear mesh with the external teeth at both ends of the major axis of the external gear. A cup-type wave gear device having a reduced speed ratio.