JP2018115693A - Wave gear device - Google Patents

Abstract

In a wave gear device, stress is suppressed from being concentrated on a flexible external gear by receiving pressure from a ball of a bearing through an outer ring. A wave gear device (1) includes a wave generator (4) that moves a meshing position in a circumferential direction by bending a flexible external gear (3) into an elliptical shape and partially meshing with a rigid internal gear (2). . The wave generator 4 includes an elliptical cam 60 and a flexible bearing 50. The flexible bearing 50 includes a flexible inner ring 51 disposed on the outer peripheral surface 60 a of the elliptical cam 60, a flexible outer ring 52 disposed on the radially inner side of the flexible outer gear 3, and the inner ring 51. Of the inner ring side raceway groove 85 and the ball 53 interposed between the outer ring side raceway groove 80 of the outer ring 52. An inner peripheral groove 70 (concave portion) disposed at a position corresponding to the outer ring side raceway groove 80 is formed on the inner peripheral surface 31 b of the body portion 31 of the flexible external gear 3. [Selection] Figure 3

Description

  The present invention relates to a wave gear device.

  At least one of the inner peripheral surface of the external gear (flexible external gear) of the meshing gear device (wave gear device) and the outer peripheral surface of the outer ring of the bearing provided on the outer periphery of the vibration generator (wave generator) There has been proposed a technique in which a groove portion is provided and an elastic body held in the groove portion is provided (see, for example, Patent Document 1).

JP 2012-57674 A

By the way, the flexible external gear receives a strong pressing force from the ball of the bearing through the flexible outer ring and is deformed into an elliptical shape, and the external teeth of the elliptical long diameter portion correspond to the corresponding internal gear of the rigid internal gear. Engage with teeth. For this reason, there exists a problem that stress concentrates on the tooth bottom part which receives pressing force from a ball via an outer ring in a flexible external gear.
The objective of this invention is providing the wave gear apparatus which can suppress that a stress concentrates on a flexible external gear by receiving a press via the outer ring | wheel from the ball | bowl of a bearing.

  The invention of claim 1 is a cylindrical rigid internal gear (2) having a plurality of internal teeth (21) on the inner peripheral surface (2a) and a cylinder having a plurality of external teeth (33) on the outer peripheral surface (31a). -Shaped flexible external gear (3) and the flexible external gear, which is disposed inside the flexible external gear, bends the flexible external gear in an elliptical shape, and external teeth of the long diameter portion are internal teeth of the rigid internal gear. And a wave generator (4; 4P) that moves the meshing position in the circumferential direction. The wave generator includes an elliptical cam (60) and a flexible bearing (50; 50P). The flexible bearing includes a flexible inner ring (51) disposed on the outer peripheral surface (60a) of the elliptical cam, and a flexibility disposed radially inward of the flexible external gear. Outer ring (52; 52P), an inner ring-side raceway groove (85) formed on the outer peripheral surface (51a) of the inner ring and the inner peripheral surface (52b; 2Pb) having a ball (53) interposed between the outer ring side raceway grooves (80), and the inner peripheral surface (31b) of the flexible external gear corresponds to the outer ring side raceway grooves. The wave gear device (1; 1P) is formed with a recess (70; 70Q) disposed at a position where a space (S) is formed between the flexible outer gear and the outer ring. provide.

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.
According to a second aspect of the present invention, the concave portion may be formed at a position corresponding to a tooth bottom (33a) of an external tooth included in the flexible external gear.

According to a third aspect of the present invention, the recess may be an inner peripheral groove that extends around the entire inner peripheral surface of the flexible external gear.
According to a fourth aspect of the present invention, an outer peripheral groove (90) extending around the entire outer periphery (52Pa) of the outer ring (52P) may be formed on the back side of the outer ring.

  According to the first aspect of the invention, the flexible external gear is pressed radially outward by the ball of the flexible bearing through the flexible outer ring at the meshing position of the internal teeth and the external teeth. A concave portion is formed on the inner peripheral surface of the flexible external gear at a position corresponding to the outer ring raceway groove, and a space is formed between the outer ring and the flexible external gear at the meshing position of the internal teeth and the external teeth. . This space reduces the pressing force applied to the flexible external gear from the outer ring, and stress is concentrated on the flexible external gear by receiving the pressure from the ball of the flexible bearing through the outer ring. Can be suppressed.

In the invention of claim 2, the concave portion formed on the inner peripheral surface of the flexible external gear is disposed at a position corresponding to the tooth bottom of the external tooth where stress tends to concentrate. For this reason, it can suppress effectively that stress concentrates on a flexible external gear.
In the invention of claim 3, since the inner peripheral groove extending around the entire inner peripheral surface of the flexible external gear is used as the recess, the flexible external gear can be easily manufactured.

  In the invention of claim 4, since the concave portion of the inner peripheral surface of the flexible external gear and the outer peripheral groove of the outer ring are used in combination, the depth of the concave portion of the inner peripheral surface of the flexible outer gear and the depth of the outer peripheral groove of the outer ring. Even if the depth is not deepened, it is possible to sufficiently suppress the stress concentration on the flexible external gear. For this reason, the strength reduction of a flexible external gear or an outer ring can be suppressed.

It is a schematic sectional drawing of the wave gear apparatus of 1st Embodiment of this invention. It is a schematic diagram of the principal part of the wave gear apparatus of 1st Embodiment. (A) is an expanded sectional view of the flexible external gear and wave generator of 1st Embodiment, (b) is an expanded sectional view of the principal part of the flexible external gear of 1st Embodiment. (A) is an expanded sectional view of the flexible external gear and wave generator in 2nd Embodiment of this invention, (b) is an expanded sectional view of the principal part of the outer ring | wheel in 2nd Embodiment. It is sectional drawing of the principal part of the flexible external gear in the modification of 1st Embodiment thru | or 2nd Embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic cross-sectional view of a wave gear device 1 according to a first embodiment of the present invention. As shown in FIG. 1, the wave gear 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 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 device 1 is used for a speed reducer or a speed increaser.

The first end member 6 and the second end member 7 are annular members having an opening at the center, and the input shaft 5 extends so as to penetrate the respective openings of the first end member 6 and the second end member 7. . The central axes of the first end member 6 and the second end member 7 coincide with the axis 1 a of the input shaft 5. The first end member 6 and the second end member 7 are spaced apart from each other in the axial direction of the input shaft 5.
The input shaft 5 is rotatably supported by the inner peripheral surfaces 6 a and 7 a of the first end member 6 and the second end member 7 via the first bearing 8 and the second bearing 9. 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 disposed between the first end member 6 and the second end member 7 with respect to the axial direction of the input shaft 5. It is sandwiched. 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 axial direction of the input shaft 5. The second end member 7, the rigid internal gear 2, and the inner ring 12 are connected and fixed 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. A plurality of internal teeth 21 are formed on the inner peripheral surface 2 a of the rigid internal gear 2.

The flexible external gear 3 includes a flexible body 31 and a connecting wall 32. The body part 31 has a thin cylindrical shape. The trunk portion 31 is disposed so that the axial direction of the trunk portion 31 coincides with the axial direction of the input shaft 5, and is opposed to the first end portion 311 facing the first end member 6 and the second end member 7. And a second end 312.
The second end portion 312 is disposed inside the rigid internal gear 2 and has external teeth that can mesh with the internal teeth 21 of the rigid internal gear 2 on the outer peripheral surface 31a (corresponding to the outer peripheral surface of the flexible external gear 3). 33 is formed. The connecting wall 32 is an annular flange that extends radially outward from the first end 311 of the body portion 31.

FIG. 2 is a schematic view of a main part of the wave gear device 1. As shown in FIGS. 1 and 2, the wave generator 4 includes a flexible bearing 50 and an elliptical cam 60. The flexible bearing 50 has flexibility. The elliptic cam 60 is disposed on the radially inner side of the flexible bearing 50. The elliptical cam 60 elastically deforms the flexible bearing 50 into an elliptical shape.
The flexible bearing 50 includes an inner ring 51 disposed on the outer peripheral surface 60a of the elliptical cam 60, an outer ring 52 disposed on the radially inner side of the flexible external gear 3, a ball 53, and a retainer (not shown). Including. The inner ring 51 and the outer ring 52 are flexible. An inner ring side raceway groove 85 is formed on the outer peripheral surface 51 a of the inner ring 51. The outer ring 52 has an outer peripheral surface 52a and an inner peripheral surface 52b. An outer ring side raceway groove 80 is formed on the inner peripheral surface 52 b of the outer ring 52. The ball 53 is interposed between the inner ring side raceway groove 85 and the outer ring side raceway groove 80. The balls 53 are sandwiched between the inner ring 51 and the outer ring 52 so as to be able to rotate and revolve while being separated from each other by a retainer.

The flexible bearing 50 has a perfect circle shape when not fitted to the elliptical cam 60. The elliptic cam 60 is formed integrally with the input shaft 5. The elliptic cam 60 may be fixed to the input shaft 5 by screwing or press fitting.
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 side in the radial direction of the inner ring 51, thereby pressing the inner ring 51 outward in the radial direction at two places of the long diameter portion (upper and lower two places in FIG. 2). The inner ring 51 is elastically deformed into an elliptical shape. Accordingly, the outer ring 52 is also elastically deformed into an elliptical shape. In the elastically deformed inner ring 51 and outer ring 52, the location of the long diameter portion changes as the elliptical cam 60 rotates.

  FIG. 3A is an enlarged schematic cross-sectional view of the flexible external gear 3 and the wave generator 4. FIG. 3B is an enlarged view of the flexible external gear 3. As shown in FIG. 3A, the flexible outer gear 3 is disposed on the inner peripheral surface (specifically, the inner peripheral surface 31 b of the body portion 31) at a position corresponding to the outer ring side raceway groove 80. An inner circumferential groove 70 extending around the entire circumference is formed as a recess. The inner peripheral groove 70 is disposed on the back side of the outer ring side raceway groove 80 on the inner peripheral surface 52b of the outer ring 52 (outer side in the radial direction of the outer ring 52 with respect to the outer ring side raceway groove 80). The inner circumferential groove 70 passes through a position corresponding to the bottom of all the outer teeth 33 of the flexible external gear 3 on the inner circumferential surface 31b.

A space S is formed between the flexible outer gear 3 and the outer ring 52 by the inner circumferential groove 70 as a recess. The space S functions as a grease reservoir.
As shown in FIG. 3B, the inner circumferential groove 70 has a bottom 71 and a pair of inner wall surfaces 72. The pair of inner wall surfaces 72 oppose each other with respect to the axial direction X of the body portion 31. A chamfer 73 is formed at a corner portion formed between each inner wall surface 72 and the inner peripheral surface 31 b of the body portion 31. The chamfer 73 may be an R chamfer as illustrated or a C chamfer.

The center position of the groove width W of the inner circumferential groove 70 with respect to the axial direction X of the body portion 31 coincides with the center position of the outer ring side raceway groove 80 with respect to the axial direction X.
The inner ring 51 is bent into an oval shape by an elliptic cam 60, and the outer ring 52 is bent into an oval shape by the inner ring 51 via a ball 53. As a result, the wave generator 4 bends the second end 312 of the body 31 of the flexible external gear 3 into a substantially elliptical shape, and the external teeth of the flexible external gear 3 at two locations of the long diameter portion. 33 is meshed with the internal teeth 21 of the rigid internal gear 2.

  In other words, the wave generator 4 presses two locations that are 180 degrees out of phase in the circumferential direction of the flexible external gear 3 toward the outer peripheral surface side, and elastically deforms the outer teeth 33 of the long diameter portion into an elliptical shape. Engage with the inner teeth 21. As the wave generator 4 rotates, the meshing position of the flexible external gear 3 and the rigid internal gear 2 moves in the circumferential direction, so that the flexible external gear 3 and the rigid internal gear 2 are moved. Differential.

  When an input shaft 5 connected to a rotation source (not shown) such as an output shaft of a motor rotates at a high speed, the wave generator 4 is bent into an elliptical shape, and the internal shaft 2 of the rigid internal gear 2 is bent in two circumferential directions. The meshing position of the external teeth 33 of the flexible external gear 3 meshing with the teeth 21 moves in the circumferential direction. Since the numbers 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 flexible external gear 3 and the rigid internal gear 2. 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 flexible external gear 3 is pressed to the outer peripheral surface side via the outer ring 52 of the flexible bearing 50 by the ball 53 of the flexible bearing 50 at the meshing position of the internal teeth 21 and the external teeth 33. [See the white arrows in FIG. 3 (a)]. Since the inner peripheral groove 70 is provided in the flexible external gear 3, the pressing force applied from the ball 53 to the flexible external gear 3 through the outer ring 52 is weakened. For this reason, the stress concentration of the flexible external gear 3 due to the pressing from the ball 53 via the outer ring 52 can be suppressed.

The inner circumferential groove 70 passes through a position corresponding to the root of each outer tooth 33 on the inner circumferential surface 31b of the body 31 of the flexible external gear 3 where stress tends to concentrate. For this reason, it is possible to effectively suppress the concentration of stress on the flexible external gear 3.
Further, since the inner circumferential groove 70 functions as a grease reservoir, the grease is supplied from the inner circumferential groove 70 to the sliding portion, so that material deterioration such as wear of the sliding portion can be suppressed. The durability of the gear device 1 can be improved.

Further, a chamfer 73 is formed at a corner portion between each inner wall surface 72 of the inner circumferential groove 70 and the inner circumferential surface 31 b of the body portion 31 of the flexible external gear 3. If the corner portion is not chamfered and formed in an edge shape, the surface pressure when pressing the flexible external gear 3 through the edge-shaped corner portion may increase. On the other hand, in this embodiment, the formation of the chamfer 73 can suppress an increase in surface pressure due to the corner portion, and the stress concentration can also be suppressed from this point.
(Second Embodiment)
FIG. 4A is an enlarged schematic cross-sectional view of the flexible external gear 3 and the wave generator 4P of the wave gear device 1P according to the second embodiment of the present invention. FIG. 4B is an enlarged view of the outer ring 52P of the second embodiment.

  The difference between the wave gear device 1P of the second embodiment shown in FIG. 4 (a) and the wave gear device 1 of the first embodiment is that the outer peripheral surface 52Pa of the outer ring 52P constituting the flexible bearing 50P extends all around. The outer peripheral groove 90 is formed. The outer peripheral groove 90 is disposed on the back side of the outer ring side raceway groove 80 on the inner peripheral surface 52Pb of the outer ring 52P (the outer side in the radial direction of the outer ring 52P with respect to the outer ring side raceway groove 80).

As shown in FIG. 4B, the outer peripheral groove 90 has a bottom portion 91 and a pair of inner wall surfaces 92. The pair of inner wall surfaces 92 are opposed to the axial direction of the outer ring 52P. A chamfer 93 is formed at a corner portion formed between each inner wall surface 92 and the outer peripheral surface 52Pa of the outer ring 52P. The chamfer 93 may be an R chamfer as illustrated or a C chamfer.
As shown in FIG. 4A, the inner peripheral groove 70 of the body 31 of the flexible external gear 3 and the outer peripheral groove 90 of the outer ring 52P are arranged at the same position with the same groove width in the axial direction of the outer ring 52P. Yes. However, the groove widths of the outer peripheral groove 90 and the inner peripheral groove 70 may be different.

With respect to the axial direction of the outer ring 52P (corresponding to the axial direction X of the body 31), the center position of the groove width WP of the outer circumferential groove 90 and the center position of the outer ring-side raceway groove 80 coincide.
In the components of the second embodiment of FIG. 4A, the same components as those of the first embodiment of FIG. 3A are referred to the components of the first embodiment of FIG. The same reference numerals as those in FIG.

In the present embodiment, since the inner peripheral groove 70 of the body portion 31 of the flexible external gear 3 and the outer peripheral groove 90 of the outer ring 52P are used in combination, the respective depths h and k of the inner peripheral groove 70 and the outer peripheral groove 90 are set. Even if it is not deepened, the stress concentration of the flexible external gear 3 can be sufficiently relaxed. For this reason, strength reduction of the flexible external gear 3 and the outer ring 52P can be suppressed.
Further, by using the inner peripheral groove 70 and the outer peripheral groove 90 as a grease reservoir, the amount of grease stored as a whole of both grooves 70 and 90 can be increased. For this reason, grease can be supplied over a long period to the sliding portion between the inner peripheral surface 31b of the body portion 31 of the flexible external gear 3 and the outer peripheral surface 52Pa of the outer ring 52P. Therefore, the durability of the wave gear device 1P can be improved.

  The following can be illustrated as a modification of 1st Embodiment and 2nd Embodiment. That is, as shown in FIG. 5, the inner peripheral surface 31b of the body 31 of the flexible external gear 3 (corresponding to the inner peripheral surface of the flexible external gear 3) is disposed at a position corresponding to the outer ring side raceway groove. A plurality of recesses 70 </ b> Q that are disposed at positions corresponding to the tooth bottoms 33 a of the external teeth 33 of the flexible external gear 3 may be formed. The plurality of recesses 70Q are spaced apart from each other in the circumferential direction of the inner peripheral surface 31b. In this case, each recessed part 70Q is each arrange | positioned in the position corresponding to the tooth bottom 33a of each external tooth 33 which tends to concentrate stress. For this reason, it is possible to effectively suppress the concentration of stress on the flexible external gear 3.

  DESCRIPTION OF SYMBOLS 1; 1P ... Wave gear apparatus, 2 ... Rigid internal gear, 2a ... Inner peripheral surface, 3 ... Flexible external gear, 4; 4P ... Wave generator, 21 ... Internal tooth, 31 ... Body part, 31a ... Outer peripheral surface 31b ... inner peripheral surface, 33 ... outer teeth, 33a ... tooth bottom, 50; 50P ... flexible bearing, 51 ... inner ring, 51a ... outer peripheral surface, 52; 52P ... outer ring, 52a; 52Pa ... outer peripheral surface, 52b; 52Pb ... Inner peripheral surface, 53 ... Ball, 70 ... Inner peripheral groove (recess), 70Q ... Recess, 71 ... Bottom, 72 ... Inner wall surface, 73 ... Chamfer, 80 ... Outer ring side raceway groove, 85 ... Inner ring side raceway groove, 90 ... outer peripheral groove, S ... space, X ... axial direction

Claims (4)

A cylindrical rigid internal gear having a plurality of internal teeth on the inner peripheral surface;
A cylindrical flexible external gear having a plurality of external teeth on the outer peripheral surface;
It is disposed inside the flexible external gear, and the flexible external gear is bent in an elliptical shape so that the external teeth of the long diameter portion mesh with the internal teeth of the rigid internal gear, and the meshing position is set in the circumferential direction. A wave generator to be moved,
The wave generator includes an elliptical cam and a flexible bearing,
The flexible bearing includes a flexible inner ring disposed on an outer circumferential surface of the elliptical cam, a flexible outer ring disposed radially inward of the flexible outer gear, and an outer circumferential surface of the inner ring. An inner ring-side raceway groove formed on the outer ring and a ball interposed between the outer ring-side raceway grooves formed on the inner peripheral surface of the outer ring, and the inner peripheral surface of the flexible outer gear includes the outer ring side A recess is formed at a position corresponding to the raceway groove,
A wave gear device in which a space is formed between the flexible outer gear and the outer ring by the recess.   2. The wave gear device according to claim 1, wherein the concave portion is formed at a position corresponding to a tooth bottom of an external tooth of the flexible external gear.   2. The wave gear device according to claim 1, wherein the concave portion is an inner circumferential groove extending along an entire circumference of an inner circumferential surface of the flexible external gear.   The wave gear device according to any one of claims 1 to 3, wherein an outer peripheral groove extending on an entire outer periphery of the outer ring is formed on a back side of the outer ring.

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