JPH05141486A - Flat type wave motion gear device having low speed reduction ratio - Google Patents

Abstract

PURPOSE:To obtain structure which can achieve the reduction ratio lower than before in a flat-type wave motion gear device CONSTITUTION:A reduction gear 1 is composed of a rigid internal gear 2, a second flexible internal gear, a flexible external gear 3, and a wave motion generator 4. The rigid cam plate 4a of the wave motion generator 4 is equipped with a large elliptic part 41 and two small elliptic parts 42, and by these the flexible internal gear 2 and the external gear 3 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 22 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 flat type wave gear device, and more particularly to a flat type wave gear device having a structure capable of realizing a reduction ratio lower than that of a conventional type.

[0002]

2. Description of the Related Art Flat wave gears are generally
It is basically composed of first and second rigid internal gears having an annular shape, an annular flexible external gear arranged inside thereof, and a wave generator mounted inside thereof.
The flexible external gear is bent into an elliptical shape by the wave generator, and the positions of both ends of the long axis mesh with the two rigid internal gears. The number of teeth of the first rigid internal gear is set to be the same as that of the flexible internal gear, and the number of teeth of the second rigid internal gear is usually set to be two more than that.

When the wave generator is rotated, these meshing positions move in the circumferential direction. First with the same number of teeth
Relative rotation does not occur between the rigid internal gear and the flexible external gear, but there is a difference in the number of teeth between the second rigid internal gear and the flexible external gear having different numbers of teeth. Corresponding relative rotation occurs.

When the first rigid internal gear is fixed here and the wave generator is rotated at a high speed, decelerated rotation can be taken out from the second rigid internal gear. Reduction ratio i in this case
Is calculated by the following equation.

I = -1 / R =-(Zd-Zc) / Zf where R: speed ratio Zf: number of teeth of flexible external gear Zc: number of teeth of first rigid internal gear (= Zf) Zd : Number of teeth of the second rigid internal gear

Here, usually, the number of teeth Zd of the second rigid internal gear is set to be two more than the number of teeth Zf of the external gear (Zd = 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 flexible external gear and the second rigid internal gear may be increased.
(In this specification, "to reduce the reduction ratio i" means to reduce the value of the speed ratio R.)

[0007]

However, the amount of bending of the external gear has an upper limit, and due to this restriction, the external gear and the second gear are
The upper limit of the difference in the number of teeth from the rigid internal gear is usually four. For this reason, the limiting speed ratio of this type of harmonic reducer is R = 5.
It is about 0, and it is difficult to reduce it further.

In view of this point, an object of the present invention is to propose a flat type wave gear device which can realize a lower reduction ratio.

[0009]

In order to solve the above-mentioned problems, in a flat type wave gear device of the present invention, a first type internal gear and a second internal gear having a larger number of teeth than an external gear. The internal gear No. 2 is a flexible gear, the external gear is also a flexible gear, and these are flexed in a radial direction by a wave generator and meshed with each other.

In the type in which the external gear and the second 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 second internal gear have a phase of 90 degrees. It may be bent in an offset elliptical shape so that the positions of both ends of the long axis of the external gear mesh with the positions of both ends of the short axis of the internal gear.

[0011]

In the flat type wave gear device of the present invention,
Both the second internal gear and the external gear are deflected by the wave generator. By bending both gears in this way, the relative amount of bending can be increased as compared with the related art, and the difference in the number of teeth between the second internal gear and the external gear can be increased accordingly. That is, the reduction ratio can be lowered.

[0012]

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 flat type speed reducer. The basic structure of the flat type speed reducer 1 of this example is the same as the conventional one, and is composed of first and second internal gears 21 and 22, an external gear 3, and an elliptical wave generator 4. ..

In this example, the first internal gear 21 is a ring-shaped rigid gear having internal teeth 21d having the same number of teeth as the external gear 3. On the other hand, the second internal gear 22 is a flexible gear having the internal teeth 22d whose number of teeth is larger than that of the external gear 3 by an even number. The second internal gear 22 is made up of a rigid annular portion 22a and a thin-walled flexible cylindrical portion 22b extending from the outer end surface thereof.
Inner teeth 22d are formed in the middle part of the inner peripheral surface 22c of b in the circumferential direction.

The external gear 3 has a thin-walled cylindrical shape as a whole, and the outer peripheral surface 3a is formed with first external teeth 31d and second external teeth 32d having the same number of teeth. The first outer tooth 31d is in a position facing the inner tooth 21d of the first inner gear 21, and the second outer tooth 32d is in a position facing the inner tooth 22d of the second inner gear 22.

On the other hand, the wave generator 4 is composed of a rigid cam plate 4a having an elliptical contour and three ball bearings 4b, 4c and 4d fitted on the outer peripheral surface thereof. The rigid cam plate 4a includes a large elliptical portion 41 arranged at intervals in the direction of the axis 1a, and two small elliptical portions 42 and 43 having the same size.

As can be seen from FIG. 3, the large elliptical portion 41
And the small ellipse portions 42 and 43 are out of phase with each other by 90 degrees.
The size is set so that it will be inscribed exactly at 1. 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 portions 42, 43, and the cross section shown in FIG. 2 is a cross section orthogonal thereto. Ball bearings 4b, 4c, and 4d are fitted on the outer peripheries of the large elliptical portion 41 and the small elliptical portions 42 and 43, respectively.

As shown in FIGS. 1 and 2, the large elliptical portion 41 of the wave generator 4 having this structure has the inner peripheral surface 22c of the tip end side of the second internal gear 22 via the ball bearing 4b.
, One small elliptical portion 42 is fitted to the back surface side of the second outer tooth 32d via the ball bearing 4c, and the other small elliptical portion 43 is fitted to the first outer tooth 31d via the ball bearing 4d. It is fitted on the back side.

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 axes of the small elliptical portions 42, 43 of the wave generator 4 are located, The second internal gear 22 is bent inward in the radial direction,
A portion of the second external tooth 32d of the external gear 3 is flexed outward in the radial direction, whereby the internal tooth 22 located at this portion is formed.
Only the portion d and the portion of the outer teeth 32d are in mesh with each other. In other parts, as can be seen from FIG. 2 showing a cross section orthogonal to the cross section shown in FIG. 1, the inner teeth 22d and the outer teeth 32d of the second internal gear 22 are in a separated state.

On the other hand, as shown in FIG. 4, the first internal gear 2
Since 1 is a rigid annular gear, its inner teeth 21d remain in a perfect circle, whereas the flexible first outer teeth 3
The portion 1d is bent by the small elliptical portion 43 of the cam plate, and both teeth are in mesh with each other at both ends of the major axis thereof.

In use, for example, a rigid first internal gear 21 is attached to a fixed member such as a case, a flexible second internal gear 22 is rotatably supported, and the wave generator 4 is used.
Enter high speed rotation into. By doing so, the large elliptical portion 41 and the small elliptical portions 42 and 43 of the wave generator 4 rotate at high speed while maintaining the phase shift of 90 degrees. Along with this high speed rotation, the first and second internal gears 21 and 22 and the external gear 3
The meshing position of also moves in the circumferential direction. As a result, the rotation reduced by the reduction ratio corresponding to the tooth number difference between the second internal gear 22 and the external gear 3 is output from the second internal gear 22.

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

[0023]

As described above, in the wave gear device of the present invention, both the external gear and the internal gear having a larger number of teeth are flexible gears, and both of them are radially moved by the wave generator. It is designed to be partially meshed by being bent to. Therefore, according to the present invention, the relative amount of bending can be increased as compared with the case where only the external gear is bent. Therefore, since 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 made lower than in the conventional case.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a speed reducer which is an embodiment of the present invention.

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

FIG. 3 is an explanatory diagram showing a meshing state of second internal gears and second external teeth in the speed reducer of FIG. 1.

FIG. 4 is an explanatory diagram showing a meshing state of first internal gears and first external teeth in the speed reducer of FIG. 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reduction gear 1a ... Axis 21 ... Rigid 1st internal gear 22 ... Flexible 2nd internal gear 22b ... Flexible cylindrical part 21d ... 1st Inner tooth 22d ... second inner tooth 3 ... flexible outer gear 31d ... first outer tooth 32d ... second outer tooth 4 ... wave generator 4a ... Rigid cam plate 41 ... Large oval part 42,43 ... Small oval part

Claims (2)

[Claims] 1. A flexible internal gear and a rigid internal gear that are arranged in parallel in the device axial direction, a flexible external gear that is arranged inside these internal gears, and the flexible internal gear and the flexible internal gear. A wave generator that bends a flexible external gear in the radial direction, partially meshes the flexible external gear with the flexible internal gear and the rigid internal gear, and moves the meshing positions of these in the circumferential direction. Wherein the rigid internal gear and the flexible external gear have the same number of teeth, and the flexible internal gear has more teeth than the flexible external gear. Flat type wave gear device having a reduced speed ratio. 2. The wave generator according to claim 1,
The phases of the flexible internal gear and the flexible external gear are set so that the internal teeth of the flexible internal gear at both short axis ends mesh with the external teeth of the flexible external gear at both long axis ends. A flat-type wave gear device having a reduced speed ratio, which is configured to be bent into an elliptical shape that is deviated by 90 degrees.