JP2017110705A - Wave gear transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wave gear transmission device configured to suppress stress concentration at a flexible external gear due to pressing force of an outer ring.SOLUTION: A wave gear transmission device 1 includes a wave generator 4 configured to make a flexible external gear 3 bent into an elliptical manner and partially engage the external gear with a rigid internal gear 2 to move an engagement position in a circumferential direction. The wave generator 4 includes a flexible nearing 50 arranged on an inner peripheral side of the flexible external gear 3, and an elliptical cam 60 arranged on an inner peripheral side of the bearing 50. The bearing 50 includes an inner ring 51, an outer ring 52 and a ball 53. On an outer periphery 52a of the outer ring 52, formed is an outer peripheral groove 70 arranged on a rear side of a raceway groove 80 of an inner periphery 52b of the outer ring 52 and extending on a whole circumference.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wave gear transmission device.

In a cup-shaped or top-hat-shaped flexible external gear of an intermeshing gear device, a technique has been proposed in which a thin-walled portion is formed in a body portion adjacent to a tooth portion so that the tooth portion can be easily bent in the radial direction ( For example, see Patent Document 1).
In a mesh hat type flexible external gear of a meshing gear device, a technique for suppressing stress concentration in the diaphragm portion by setting a change in thickness of the diaphragm portion connected to the body portion has been proposed (for example, Patent Documents). 2).

JP-A-10-159917 Japanese Patent Laid-Open No. 8-166052

  By the way, a wave generator for bending the flexible external gear into an ellipse is arranged inside the flexible external gear. The wave generator includes a flexible bearing and an elliptical cam. The flexible external gear receives a strong pressing force from the ball of the bearing through the outer ring and is deformed into an elliptical shape, and the external teeth of the elliptical long diameter portion are engaged with the corresponding internal teeth of the rigid internal gear. For this reason, there exists a problem that stress concentrates on the tooth bottom part which receives pressing force from an outer ring in a flexible external gear.

In Patent Documents 1 and 2, such stress concentration cannot be suppressed.
An object of the present invention is to provide a wave gear transmission device capable of suppressing stress concentration of a flexible external gear due to pressing of an outer ring.

  The invention of claim 1 includes a rigid internal gear (2) having a plurality of internal teeth (21) on the inner periphery (2a) and a flexible external gear having a plurality of external teeth (33) on the outer periphery (31a). 3) and arranged inside the flexible external gear, the flexible external gear is bent into an elliptical shape and partially meshed with the rigid internal gear to move the meshing position in the circumferential direction. A wave generator (4), the wave generator having an inner ring (51), an outer ring (52), and a ball (53) interposed between the inner ring and the outer ring ( 50) and an elliptical cam (60) that is disposed on the inner peripheral side of the bearing and elastically deforms the bearing toward the outer peripheral side, and in the outer periphery (52a) of the outer ring, the inner periphery (52b) of the outer ring An outer circumferential groove (70) disposed on the back side of the raceway groove (80) and extending around the entire circumference is formed. Providing the wave gear transmission device (1) which are.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
As in claim 2, the groove width w of the outer peripheral groove in the axial direction (X) of the outer ring and the diameter D of the ball may satisfy the following relational expression (1).

w ≧ D / 10 (1)
As in claim 3, the groove depth d of the outer circumferential groove and the minimum thickness t at the bottom of the raceway groove of the outer ring may satisfy the following relational expression (2).
d ≦ t / 2 (2)

According to the first aspect of the present invention, the bottom portion of the outer teeth is pressed to the outer peripheral side via the outer ring of the bearing by the ball of the bearing in the meshing region of the inner teeth and the outer teeth. Since the outer ring is provided with the outer peripheral groove, the pressing force applied from the outer ring to the tooth bottom portion is weakened. For this reason, the stress concentration of the flexible external gear due to the pressing of the outer ring can be suppressed.
In invention of Claim 2, it can contribute to suppression of stress concentration by making groove width w of an outer periphery groove | channel into 1/10 or more of the diameter D of a ball | bowl.

  In the invention of claim 3, the strength of the outer ring can be ensured by setting the groove depth d of the outer circumferential groove to be 1/2 or less of the minimum thickness t at the bottom of the raceway groove of the outer ring.

It is a schematic sectional drawing of the wave gear transmission device of one Embodiment of this invention. It is a schematic diagram of the principal part of a wave gear transmission apparatus. (A) is an expanded sectional view of the structure around a wave generator, (b) is an enlarged sectional view of the principal part of an outer ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the wave gear transmission device 1 includes a rigid internal gear 2, a flexible external gear 3, a wave generator 4, an input shaft 5, a first end member 6, and a second end member. 7, a first bearing 8, a second bearing 9, and a cross roller bearing 10.
The input shaft 5 is connected and fixed to a rotation source such as an output shaft of the motor. The first end member 6 is connected and fixed to a first load member (not shown) that provides a rotational load to the first end member 6. The first end member 6 constitutes an output member of the wave gear transmission device 1. The second end member 7 is connected and fixed to a second load member (not shown) that provides a fixed load to the second end member 7. The second load member restrains the second end member 7 from rotating. The wave gear transmission device 1 is used for a speed reducer or a speed increaser.

The first end member 6 and the second end member 7 are spaced apart in the direction of the device axis 1a. The first end member 6 and the second end member 7 are annular members, and the central axes of the first end member 6 and the second end member 7 coincide with the device axis 1a.
The input shaft 5 extends through the centers of the first end member 6 and the second end member 7 in the direction of the device axis 1a. The input shaft 5 is rotatably supported by the inner peripheral surfaces 6a and 7a of the first end member 6 and the second end member 7 via the first bearing 8 and the second bearing 9, respectively. The first bearing 8 and the second bearing 9 are, for example, ball bearings.

The rigid internal gear 2, the flexible external gear 3, the wave generator 4, and the cross roller bearing 10 are sandwiched between the first end member 6 and the second end member 7 with respect to the direction of the apparatus axis 1a. It is. The cross roller bearing 10 includes an outer ring 11, an inner ring 12, and a roller 13.
The rigid internal gear 2 is disposed between the second end member 7 and the inner ring 12 of the cross roller bearing 10 with respect to the direction of the device axis 1a. The second end member 7, the rigid internal gear 2, and the inner ring 12 are connected by a fixing screw 14 so as to be integrally rotatable. A plurality of fixing screws 14 are provided at regular intervals in the circumferential direction of the second end member 7. The rigid internal gear 2 has a plurality of internal teeth 21 on the inner peripheral surface 2a.

The flexible external gear 3 includes a body portion 31 and a connecting wall 32. The body portion 31 has a thin cylindrical shape, and has a first end portion 311 and a second end portion 312 with respect to the direction of the apparatus axis 1a. The first end portion 311 faces the first end member 6. The second end portion 312 faces the second end member 7.
On the outer periphery 31 a of the body portion 31 (corresponding to the outer periphery of the flexible external gear 3), external teeth 33 are formed which are arranged inside the rigid internal gear 2 and can mesh with the internal teeth 21 of the rigid internal gear 2. ing.

The connecting wall 32 extends radially outward from the first end 311 of the body portion 31. That is, the flexible external gear 3 has a so-called top hat shape.
In the present embodiment, the wave gear transmission device 1 will be described based on an example of a so-called top hat type, but the present invention is a so-called cup type wave gear transmission in which the flexible external gear 3 has a cup shape. The present invention can be applied to a device or a so-called flat (pancake type) wave gear transmission device in which the flexible external gear 3 is formed in a flat shape.

FIG. 2 is a schematic view of a main part of the wave gear transmission device 1. As shown in FIGS. 1 and 2, the wave generator 4 includes a bearing 50 and an elliptical cam 60. The bearing 50 has flexibility. The elliptical cam 60 is disposed on the inner peripheral side of the bearing 50. The elliptic cam 60 elastically deforms the bearing 50 to the outer peripheral side.
Bearing 50 includes an inner ring 51, an outer ring 52, a ball 53, and a retainer (not shown). The inner ring 51 and the outer ring 52 are flexible. The ball 53 is sandwiched between the inner ring 51 and the outer ring 52 so as to be able to rotate and revolve.

The retainer is configured to hold the balls 53 apart from each other. The bearing 50 has a perfect circle shape when not fitted to the elliptical cam 60.
The elliptic cam 60 is formed integrally with the outer peripheral surface 5 a of the input shaft 5. The elliptic cam 60 may be fixed to the outer peripheral surface 5a of the input shaft 5 by screwing or the like.
The major axis of the elliptical cam 60 is set to be larger than the inner diameter of the inner ring 51 in a perfect circle, and the minor axis of the elliptical cam 60 is set to be smaller than the inner diameter of the inner ring 51 in a perfect circle. For this reason, as shown in FIG. 2, the elliptical cam 60 is arranged on the inner peripheral side of the inner ring 51 so that the inner ring 51 is pressed toward the outer peripheral side at two positions of the long diameter portion (upper and lower two positions in FIG. 2). The inner ring 51 is elastically deformed into an elliptical shape. As the elliptic cam 60 rotates, the major axis portion rotates, and the elastically deformed inner ring 51 rotates integrally with the elliptic cam 60.

FIG. 3A is an enlarged schematic cross-sectional view of the structure around the wave generator 4. FIG. 3B is an enlarged view of the outer periphery 52 a of the outer ring 52.
As shown in FIG. 3A, an outer peripheral groove 70 extending along the entire periphery of the outer ring 52 is formed on the outer periphery 52 a of the outer ring 52. The outer circumferential groove 70 is disposed on the back side of the raceway groove 80 on the inner circumference 52 b of the outer ring 52.

As shown in FIG. 3B, the outer peripheral groove 70 has a bottom 71 and a pair of inner wall surfaces 72. The pair of inner wall surfaces 72 are opposed to the axial direction X of the outer ring 52. A chamfer 90 is formed at a corner portion formed between each inner wall surface 72 and the outer periphery 52 a of the outer ring 52. The chamfer 90 may be an R chamfer as illustrated or a C chamfer.
With reference to FIG. 3A, the groove width w of the outer circumferential groove 70 in the axial direction X of the outer ring 52 and the diameter D of the ball 53 satisfy the following relational expression (1).

w ≧ D / 10 (1)
The center position of the groove width w of the outer circumferential groove 70 with respect to the axial direction X coincides with the center position of the track groove 80 with respect to the axial direction X.
Further, the groove depth d of the outer circumferential groove 70 and the minimum thickness t of the outer ring 52 at the bottom of the raceway groove 80 may satisfy the following relational expression (2).

d ≦ t / 2 (2)
Since the inner ring 51 and the outer ring 52 can rotate independently, the inner ring 51 rotates integrally with the elliptical cam 60, and the outer ring 52 is bent into an oval shape by the inner ring 51. As a result, the wave generator 4 bends the flexible external gear 3 into a substantially elliptical shape, and partially engages the rigid internal gear 2 and the flexible external gear 3 at two locations of the long diameter portion thereof. .

That is, the wave generator 4 presses the two radial opposite sides of the flexible external gear 3 toward the outer peripheral side and elastically deforms the outer teeth 33 of the long diameter portion into the internal teeth 21. Engage. And the wave generator 4 makes the flexible external gear 3 and the rigid internal gear 2 differential by moving the meshing position of the flexible external gear 3 and the rigid internal gear 2 in the circumferential direction.
When an input shaft 5 connected to a rotation source (not shown) such as an output shaft of a motor rotates at high speed, it is bent into an elliptic shape by an elliptical wave generator 4 and has internal teeth at two locations in the circumferential direction. The meshing portion of the external teeth 33 meshing with 21 moves in the circumferential direction. Since the number of teeth of the external teeth 33 and the internal teeth 21 are different, relative rotation corresponding to the difference in the number of teeth occurs between the external teeth 33 and the internal teeth 21. This rotation is greatly decelerated compared to the input rotation speed. The decelerated rotation is output from the first end member 6 (output member) connected to the load member and transmitted to the load member (not shown).

  In the present embodiment, the bottom portion of the external tooth 33 in the meshing region of the internal tooth 21 and the external tooth 33 is pressed to the outer peripheral side by the ball 53 of the bearing 50 via the outer ring 52 of the bearing 50 [FIG. ) (See white arrows)]. Since the outer peripheral groove 70 is provided in the outer ring 52, the pressing force applied from the outer ring 52 to the tooth bottom portion of the external tooth 33 is weakened. For this reason, the stress concentration of the flexible external gear 3 due to the pressing of the outer ring 52 can be suppressed.

Further, material deterioration such as wear of the sliding portion between the inner periphery of the flexible external gear 3 and the outer periphery 52a of the outer ring 52 can be suppressed.
Further, if the groove width w is less than 1/10 of the diameter D of the ball 53 (w <D / 10), there is a possibility that a required effect cannot be obtained as an effect of suppressing stress concentration. On the other hand, in the present embodiment, by setting the groove width w of the outer circumferential groove 70 in the axial direction X to be 1/10 or more of the diameter D of the ball 53 (w ≧ D / 10), the root of the external teeth 33 A necessary effect can be exhibited in suppressing the stress concentration in the portion.

In order to suppress the stress concentration of the flexible external gear 3 (that is, to set the maximum stress of the flexible external gear 3 to a required value or less), the groove depth d is preferably set to 10 μm or more, for example.
Further, if the groove depth d of the outer circumferential groove 70 exceeds 1/2 of the minimum thickness t at the bottom of the raceway groove 80 of the outer ring 52 (when d> t / 2), the strength of the outer ring 52 will be described. There is a risk that the required strength cannot be obtained as (tensile strength). On the other hand, in the present embodiment, the outer ring 70 has a groove depth d of 1/2 or less of the minimum thickness t at the bottom of the raceway groove 80 of the outer ring 52 (d ≦ t / 2). The required strength can be ensured in 52. From this viewpoint, the groove depth d is, for example, 100 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less.

  Further, a chamfer 90 is formed at a corner portion between each inner wall surface 72 of the outer peripheral groove 70 and the outer periphery 52 a of the outer ring 52. If the corner portion is not chamfered and is formed in an edge shape, the surface pressure when the tooth bottom portion of the external tooth 33 is pressed by the edge-shaped corner portion may increase. On the other hand, in this embodiment, the formation of the chamfer 90 can suppress an increase in surface pressure due to the corner portion, and the stress concentration can also be suppressed from this point.

The present invention is not limited to the above-described embodiment. For example, grease may be accommodated in the outer circumferential groove 70. In that case, material deterioration such as wear of a sliding portion between the inner periphery of the flexible external gear 3 and the outer periphery 52a of the outer ring 52 can be further suppressed.
In addition, the present invention can be variously modified within the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 ... Wave gear transmission device, 2 ... Rigid internal gear, 2a ... Outer periphery, 3 ... Flexible external gear, 4 ... Wave generator, 21 ... Internal tooth, 31 ... Body part, 31a ... Outer periphery, 33 ... External tooth, DESCRIPTION OF SYMBOLS 50 ... Bearing, 51 ... Inner ring, 52 ... Outer ring, 52a ... Outer periphery, 52b ... Inner periphery, 53 ... Ball, 70 ... Outer peripheral groove, 71 ... Bottom part, 72 ... Inner wall surface, 80 ... Track groove, 90 ... Chamfering, D ... Diameter (of ball), d ... groove depth, t ... minimum wall thickness, w ... groove width

Claims (3)

A rigid internal gear having a plurality of internal teeth on the inner circumference;
A flexible external gear having a plurality of external teeth on the outer periphery;
A wave generator disposed inside the flexible external gear and flexing the flexible external gear in an elliptical shape to partially mesh with the rigid internal gear to move the meshing position in the circumferential direction; With
The wave generator includes a flexible bearing having an inner ring, an outer ring, and a ball interposed between the inner ring and the outer ring, and is disposed on the inner peripheral side of the bearing to elastically deform the bearing toward the outer peripheral side. An elliptical cam, and
A wave gear transmitting device in which an outer peripheral groove is formed on the outer periphery of the outer ring and disposed on the back side of the raceway groove on the inner periphery of the outer ring and extending all around. 2. The wave gear transmission device according to claim 1, wherein a groove width w of the outer circumferential groove in the axial direction of the outer ring and a diameter D of the ball satisfy the following relational expression (1).
w ≧ D / 10 (1) 3. The wave gear transmission device according to claim 1, wherein the groove depth d of the outer circumferential groove and the minimum thickness t at the bottom of the raceway groove of the outer ring satisfy the following relational expression (2).
d ≦ t / 2 (2)

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