CN106949196B

CN106949196B - Eccentric oscillating type reduction gear

Info

Publication number: CN106949196B
Application number: CN201610905479.2A
Authority: CN
Inventors: 白水健次; 山本章
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2015-11-06
Filing date: 2016-10-18
Publication date: 2020-04-03
Anticipated expiration: 2036-10-18
Also published as: KR102548182B1; KR20170053566A; CN106949196A; JP2017089712A; JP6563784B2

Abstract

The invention provides an eccentric oscillating type speed reducer capable of further reducing damage to the tooth surface of an external gear. An eccentric oscillation type reduction gear (G1) is provided with: an external gear (10); an internal gear (30) that meshes with the external gear; and a crankshaft (32) for eccentrically oscillating the external gear, the external gear having: a tooth portion (11) in which external teeth are formed; a through-hole (12) provided at a position offset from the axial center (C10) of the external gear; and circumferential grooves (13, 13) provided between the through-holes and the teeth on both axial end surfaces (19, 19) of the external gear.

Description

Eccentric oscillating type reduction gear

The present application claims priority based on japanese patent application No. 2015-218313, which was filed on day 6 of 11/2015. The entire contents of this Japanese application are incorporated by reference into this specification.

Technical Field

The present invention relates to an eccentric oscillating type reduction gear.

Background

Patent document 1 discloses an eccentric oscillating type reduction gear. The reduction gear includes an external gear, an internal gear that meshes with the external gear, and a crankshaft that eccentrically oscillates the external gear, and outputs, as an output, a relative rotation generated between the external gear and the internal gear. The internal gear is composed of an internal gear main body integrated with the housing, and internal gear pins that constitute internal teeth of the internal gear and are rotatably supported by pin grooves of the internal gear main body.

In this reduction gear, an annular groove portion is provided on an axial end surface of the external gear corresponding to an axial end portion of the internal gear pin.

Patent document 1: japanese patent laid-open No. 2010-249262

However, there are problems as follows: the above-mentioned countermeasure is not sufficient for the tooth surfaces of the outer gear to be damaged.

Disclosure of Invention

The present invention has been made in view of such a problem, and an object thereof is to further reduce damage to the tooth surface of the external gear.

The present invention solves the above problems by a configuration in which an eccentric oscillating type reduction gear device of the present invention includes: an outer gear; an internal gear internally meshed with the external gear; and a crankshaft that eccentrically oscillates the external gear, the external gear including: a tooth portion formed with external teeth; a through hole provided at a position offset from the axis center of the external gear; and a circumferential groove provided between the tooth portion and the through hole in both end surfaces in the axial direction of the external gear.

In the eccentric rocking type reduction gear, the output shaft may tilt due to a radial load from the load side. If the output shaft is inclined, the axis of the external gear and the axis of the internal gear cannot be maintained in a parallel state, and a specific axial end portion of the external gear strongly abuts against the internal gear, resulting in a strong meshing load being generated at the axial end portion of the external gear. When the output shaft is inclined toward the opposite side, the axial end face of the external gear on the opposite side strongly abuts against the internal gear.

Therefore, in the present invention, a circumferential groove is formed between the through-hole and the tooth portion in both end surfaces in the axial direction of the external gear.

In the present invention, since the circumferential groove is formed between the through-hole and the tooth portion in both end surfaces in the axial direction of the external gear, even when the external gear is inclined, the tooth portion of the external gear can be flexibly inclined, and damage to the tooth surface of the external gear can be more effectively reduced.

According to the present invention, damage to the tooth surface of the external gear can be further reduced.

Drawings

Fig. 1 is a sectional view of an eccentric oscillating type reduction gear according to an example of the embodiment of the present invention.

Fig. 2 is an enlarged sectional view of a main portion of the reduction gear transmission of fig. 1.

Fig. 3 is a front view showing an external gear unit of the reduction gear transmission of fig. 1.

Fig. 4 is an enlarged sectional view taken along the line IV-IV of fig. 3.

Fig. 5 is a graph showing the relationship between various shapes of the circumferential groove and the surface pressure.

In the figure: g1-eccentric oscillating type reduction gear, 10-external gear, 11-tooth, 12-through hole, 13-circumferential groove, 19-axial end face, 30-internal gear, 32-input shaft (crank shaft), C10-axis of external gear.

Detailed Description

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a sectional view of an eccentric oscillating type reduction gear G1 according to an example of the embodiment of the present invention, and fig. 2 is an enlarged sectional view of a main part thereof.

The eccentric oscillating type reduction gear G1 includes: a 2-piece external gear 10 provided side by side on a load side and a side opposite to the load side; an internal gear 30 internally meshing with the external gear 10; and an input shaft 32 for eccentrically oscillating the external gear 10. That is, in the present reduction gear G1, the input shaft 32 also serves as a crank shaft that eccentrically oscillates the external gear 10.

The input shaft 32 is formed of a solid shaft member, and is disposed at the radial center of the reduction gear G1 (on the axial center C30 of the ring gear 30). A cooling fan 36 covered with a fan cover 34 is attached to the input shaft 32.

An eccentric body 40, which is a member different from the input shaft 32, is fitted to the input shaft 32 via a key 38. The eccentric body 40 has a non-load side eccentric portion 41 and a load side eccentric portion 42. The outer peripheries of the non-load-side eccentric portion 41 and the load-side eccentric portion 42 are eccentric by an amount e with respect to the axial center C32 of the input shaft 32 (i.e., the axial center C30 of the ring gear 30). In this example, the non-load-side eccentric portion 41 and the load-side eccentric portion 42 are eccentric in directions separated from each other with an eccentric phase difference of 180 degrees.

The 2-piece external gear 10 is swingably assembled to the outer peripheries of the non-load side eccentric portion 41 and the load side eccentric portion 42 via an eccentric body bearing 51 constituted by a roller. Therefore, the eccentric phase difference of each external gear 10 is also 180 degrees.

Fig. 3 is a front view of the outer gear 10 alone. The 2-piece external gear 10 is simply different in eccentric phase when assembled, and is the same component as a single component. Each of the external gears 10 has: a tooth portion 11 formed with external teeth; a through-hole 12 provided at a position offset from the axial center C10 of the external gear 10; and a circumferential groove 13 provided between the tooth portion 11 and the through-hole 12 in both

axial end surfaces

19, 19 of the external gear 10. The structure of the external gear 10 will be described in detail later.

The external gear 10 internally meshes with the internal gear 30. The internal gear 30 includes: an internal gear body 30A integrated with (a 1 st outer case 61 described later on) the case 60; and a cylindrical internal gear pin 30B constituting "internal teeth" of the internal gear 30. The internal gear pin 30B is rotatably assembled to a pin groove 30C formed in the internal gear body 30A. The number of internal teeth of the internal gear 30 (the number of internal tooth pins 30B) is slightly larger than the number of external teeth (1 in this example) formed on the tooth portions 11 of the external gear 10.

The casing 60 of the reduction gear G1 is mainly composed of a 1 st casing 61, a 2 nd casing 62, and a 3 rd casing 63. The 1 st outer case 61, the 2 nd outer case 62, and the 3 rd outer case 63 are fastened together by a case bolt 64.

The 1 st outer case 61 is integrated with the internal gear body 30A of the internal gear 30, and houses the speed reduction mechanism 55. The 2 nd outer case 62 is coupled to the 1 st outer case 61 on the load side in the axial direction. The 2 nd outer housing 62 supports the output shaft 80 via a pair of

tapered roller bearings

82, 83. A cover 66 is attached to the load side of the No. 2 outer case 62. An output side oil seal 84 is disposed between the cover 66 and the output shaft 80. A mounting leg portion 62A is integrally formed on the 2 nd outer case 62. The reduction gear G1 is fixed to an unillustrated external member via the mounting leg portion 62A. The 3 rd outer case 63 is coupled to the 1 st outer case 61 on the opposite side to the load. The 3 rd outer housing 63 supports the input shaft 32 via a ball bearing 86. An input side oil seal 88 is disposed between the inner periphery of the 3 rd outer housing 63 and the input shaft 32.

A disc-shaped carrier 70 is disposed on the load side of the load side outer gear 10. The carrier 70 is a member for outputting relative rotation of the external gear 10 with respect to the internal gear 30, and is integrated with the output shaft 80. The input shaft 32 (crank shaft) is supported on the inner periphery of the 3 rd outer housing 63 via a ball bearing 86, and is supported on the inner periphery of the carrier 70 via a roller bearing 90.

The structure of the external gear 10 and its vicinity will be described in further detail below with reference to fig. 1 to 4.

The external gear 10 is configured such that the load side and the non-load side thereof are symmetrical to each other with the axial center P10 as a plane of symmetry. That is, the load-side circumferential groove 13 and the non-load-side circumferential groove 13 have mirror image structures with respect to the axial center P10. Therefore, the same reference numerals are used in the drawings and the description is given below. The external gear 10 may be configured asymmetrically with respect to the axial center P10. The left and right circumferential grooves 13 may have different shapes.

The external gear 10 has a tooth portion 11 at the outermost periphery, and the tooth portion 11 has an external tooth of trochoid tooth form.

The external gear 10 has a plurality of (10 in this example: see fig. 3) through-holes 12 at positions offset from the axis C10 by R12. An inner pin 72 is inserted through the through hole 12. Since the inner pin 72 penetrates the external gear 10, the inner pin 72 operates in synchronization with the rotation of the external gear 10. The inner pin 72 is press-fitted into the wheel carrier 70 and is integrated with the wheel carrier 70. An inner roller 74 as a sliding promoting member is slidably fitted to the outer surface of the inner pin 72. A part of the inner roller 74 abuts against the through-hole 12 of the outer gear 10. The outer diameter of the inner roller 74 is smaller than the inner diameter of the through-hole 12, and a gap corresponding to 2 times the eccentric amount (e) of the non-load-side eccentric portion 41 and the load-side eccentric portion 42 is secured between the inner roller 74 and the through-hole 12.

The external gear 10 has a circumferential groove 13 on each of both axial end surfaces 19, 19 (a load-side axial end surface 19 and an opposite-load axial end surface 19). More specifically, the circumferential groove 13 is provided between the through-hole 12 and the tooth portion 11 in the axial end surface 19 of the external gear 10.

For convenience, an axial end surface between the circumferential groove 13 and the tooth portion 11 in the axial end surface 19 of the external gear 10 is hereinafter referred to as an outer axial end surface 17, and an axial end surface between the circumferential groove 13 and the through-hole 12 is hereinafter referred to as an inner axial end surface 18. In the external gear 10, the outer axial end surface 17 and the inner axial end surface 18 are flush with each other. That is, the thickness W17 of the external gear 10 between the outer axial both end surfaces 17, 17 is the same as the thickness W18 of the external gear 10 between the inner axial both end surfaces 18, 18 (W17 is equal to W18). However, the outer axial end surface 17 and the inner axial end surface 18 do not necessarily have to be flush. For example, the thickness of the external gear between the outer axial end surfaces may be thicker than the thickness of the external gear between the inner axial end surfaces, with the circumferential groove as a boundary. For convenience, the "axial end surface" may be simply referred to as "axial end surface" hereinafter.

Here, the above "between the tooth portion 11 and the through-hole 12 in the both axial end surfaces 19, 19 of the external gear 10" means that "the external gear 10 is configured such that the outer axial end surface 17 having the thickness W17 larger than the thickness (axial width) W15 at the deepest portion Md of the circumferential groove 13 is formed over the entire circumference between the circumferential groove 13 and the tooth portion 11, and the inner axial end surface 18 having the thickness W18 larger than the thickness W15 at the deepest portion Md of the circumferential groove 13 is formed over the entire circumference also between the circumferential groove 13 and the through-hole 12". In other words, the circumferential groove 13 of the external gear 10 does not merge with the tooth portion 11 or the through-hole 12 of the external gear 10 over the entire circumference.

In other words, between the circumferential groove 13 and the tooth 11, there is an outer shaft end face 17 at least with a radial dimension L17 ensured. Further, an inner shaft end surface 18 having at least a radial dimension L18 is provided between the circumferential groove 13 and the through hole 12.

In this example, the width of the circumferential groove 13 has a single radial dimension L13, and is formed in a ring shape that continuously circles one turn in the circumferential direction.

The circumferential groove 13 has: an outer wall surface 14, an inner wall surface 16, and a bottom surface 15 (deepest portion Md) located between the outer wall surface 14 and the inner wall surface 16.

The "outer side wall surface 14" of the circumferential groove 13 is a surface located radially outward of the circumferential groove 13 and extending from the outer side axial end surface 17 of the external gear 10 to the deepest portion Md. The "deepest portion" is a portion closest to the axial center of the external gear in the circumferential groove (a portion where the thickness of the external gear is the thinnest in the circumferential groove), and in this example, the bottom surface 15 described later corresponds to the deepest portion Md. The outer side wall surface 14 of the circumferential groove 13 of the external gear 10 is inclined with respect to the axial direction so as to approach the axial center C10 of the external gear 10 toward the axial center P10 of the external gear 10. Specifically, the angle θ 14(22.5 degrees in this example) is inclined with respect to the axial direction so as to be close to the axial center C10 of the external gear 10.

The "inner side wall surface 16" of the circumferential groove 13 is a surface located radially inward of the circumferential groove 13 and extending from the inner axial end surface 18 of the external gear 10 to the deepest portion Md. The inner side wall surface 16 of the circumferential groove 13 of the external gear 10 is inclined with respect to the axial direction so as to be away from the axial center C10 of the external gear 10 toward the axial center P10 of the external gear 10. Specifically, the angle θ 16(50 degrees in this example) is inclined with respect to the axial direction so as to be away from the axial center C10 of the external gear 10. That is, the angle θ 16(50 degrees) at which the inner wall surface 16 is inclined with respect to the axial direction is larger than the angle θ 14(22.5 degrees) at which the outer wall surface 14 is inclined with respect to the axial direction.

On the other hand, the "bottom surface 15" of the circumferential groove 13 is a surface located between the outer wall surface 14 and the inner wall surface 16. Further, according to this definition, for example, when the outer wall surface and the inner wall surface are in direct contact, there is no surface corresponding to the bottom surface, as will be described later. In the external gear 10, the outer wall surface 14 and the inner wall surface 16 do not directly abut on each other, and therefore, a bottom surface 15 is present. The radial dimension of the bottom surface 15 is L15. The bottom surfaces 15 are each formed by a plane perpendicular to the axial direction. In other words, the circumferential groove 13 of the external gear 10 has the deepest portion Md of the radial dimension L15 formed by the bottom surface 15 perpendicular to the axial direction.

In this example, the thickness (axial width) W15 of the bottom surface 15 (deepest portion Md) in the circumferential groove 13 of the external gear 10 is set to be 2 times (W15 is 2 · D17 is 2 · D18) the axial depth D17 from the outer axial end surface 17 to the bottom surface 15 (i.e., the axial depth D18 from the inner axial end surface 18 to the bottom surface 15).

The thickness (axial width) W17 of the external gear 10 between the outer axial end surfaces 17, 17 is the same as the thickness W18 of the external gear 10 between the inner axial end surfaces 18, 18 (W17 is W18). The axial depth D17 of the circumferential groove 13 from the outer axial end surface 17 to the bottom surface 15 (deepest portion Md) is the same as the axial depth D18 from the inner axial end surface 18 to the bottom surface 15 (deepest portion Md) (D17 is D18).

The axial depth D17 (D18) of the circumferential groove 13 from the outer shaft end surface 17 to the bottom surface 15 (deepest portion Md) is set to 1/4(D17 ═ D18 ═ W17 ═ 1/4 · W18) of the thickness (axial width) W17 of the external gear 10 between the outer shaft end surfaces 17, 17 (thickness W18 of the external gear 10 between the inner shaft end surfaces 18, 18).

However, the formation of the circumferential groove 13 is not necessarily limited by these dimensional examples.

Referring to fig. 2 and 3, the reduction gear G1 includes external gears 10 (a plurality of) in the axial direction, and an annular insert ring 76 that regulates the axial position of the external gears 10 is provided between the external gears 10. That is, the external gear 10 is positioned in the axial direction by being disposed between the load-opposing-side end surface 70A of the carrier 70 and the load-side projection surface 63A of the 3 rd outer housing 63 with the insert ring 76 interposed therebetween.

The insert ring 76 circumscribes the inner roller 74 so as to be positioned radially. The outer diameter (the radial dimension from the axial center C32 of the input shaft 32) of the insert ring 76 is R76. The radial dimension between the end 16a of the inner sidewall surface 16 of the circumferential groove 13 of the external gear 10 and the axial center C10 of the external gear 10 is R16 a. However, the radial dimension from the axial center C32 of the input shaft 32 when the end 16a of the inner wall surface 16 is closest to the axial center C32 of the input shaft 32 is R16min, and the radial dimension from the axial center C32 of the input shaft 32 when the end is farthest from the axial center C32 of the input shaft 32 is R16 max. The radial dimension R16min closest to the axial center C32 of the input shaft 32 is greater than R76. That is, when the external gear 10 swings, the radial dimension of the end portion 16a of the inner wall surface 16 of the circumferential groove 13 from the axial center C32 of the input shaft 32 varies from R16min to R16max, but in any swinging state, (the end portion 16a of the inner wall surface 16 of) the circumferential groove 13 does not overlap with the insert ring 76 when viewed from the axial direction (R16max > R16min > R76).

Next, the operation of the present reduction gear G1 will be described. First, the operation of the power transmission system will be explained.

When the input shaft 32 (crankshaft) is rotated by rotation of a motor (not shown), the eccentric body 40 coupled to the input shaft 32 via the key 38 is rotated. When the eccentric body 40 rotates, the external gear 10 eccentrically swings via the non-load side eccentric portion 41 and the load side eccentric portion 42 formed on the outer periphery of the eccentric body 40. The external gear 10 internally meshes with the internal gear 30 while maintaining an eccentric phase difference of 180 degrees. Therefore, the following phenomenon occurs: the meshing positions of the external gears 10 and the internal gears 30 on the opposite load side and the meshing positions of the external gears 10 and the internal gears 30 on the load side (in a state of being 180 degrees apart from each other) are sequentially shifted for each 1 rotation of the input shaft 32.

At this time, the internal gear body 30A of the internal gear 30 is integrated with the 1 st outer case 61, and the external gear 10 is internally meshed with the internal gear pins 30B constituting the internal teeth. Therefore, the external gears 10 receive the meshing reaction force from the 1 st outer housing 61 side via the internal gear pins 30B, and rotate in the direction opposite to the rotation of the input shaft 32.

As a result, every 1 rotation of the input shaft 32, the external gear 10 rotates (rotates) with respect to the internal gear 30 fixed to the 1 st outer housing 61 by an amount corresponding to the difference in the number of teeth of the internal gear 30, that is, by "1 tooth amount". The rotation component is transmitted to the carrier 70 disposed on the axial load side of the external gear 10 via the inner rollers 74 and the inner pins 72, and the output shaft 80 integrated with the carrier 70 is rotated. This enables driving of the driven shaft of the target machine connected to the output shaft 80.

In the reduction gear G1, since the difference in the number of teeth between the external gear 10 and the internal gear 30 is "1", it is possible to finally achieve reduction and increase in torque at a reduction ratio of 1/(the number of teeth of the external gear 10).

In this way, in the present reduction gear G1, the transmission of power is performed by the engagement between the respective external gears 10 and the internal gear pins 30B of the internal gear 30. Here, when the output shaft 80 is tilted by a radial load from the load side, the carrier 70 integrated with the output shaft 80 is also tilted, and as a result, the inner pins 72 (and the inner rollers 74) are tilted, and therefore the external gear 10 is tilted in accordance with the tilt of the inner pins 72 (and the inner rollers 74). That is, the tooth portions 11 of the respective external gears 10 are inclined with respect to the internal tooth pins 30B of the internal gear 30 (the tooth portions 11 of the respective external gears 10 are not parallel to the internal tooth pins 30B).

In addition, when the reduction gear G1 includes a plurality of external gears 10 and the eccentric phases of the respective external gears 10 are different from each other, the internal pins 30B of the internal gear 30 do not necessarily rotate while simply oscillating around the intermediate portion in the axial direction (as described in patent document 1). Qualitatively, the internal gear pin 30B is deformed as follows: the axial portion of the circumferential position of the internal gear pin 30B, at which each external gear 10 is currently in contact, is pushed out radially outward most.

When the outer member itself to which the mounting leg portion 62A of the 2 nd outer case 62 is fixed rotates, a radial load may be applied to the inner pin 30B via the 2 nd outer case 62 and the 1 st outer case 61.

In short, the deformation of the internal gear pin 30B varies in both the axial direction and the circumferential direction, and a strong meshing load is not necessarily generated only at the end portion of the internal gear pin 30B.

That is, when the state of contact (meshing) of the external gear 10 with the internal tooth pins 30B is changed from the parallel state to the inclined state, the meshing load at the axial end portion of the external gear 10 on the side closer to the internal tooth pins 30B at a specific circumferential position at a specific moment becomes large, and the tooth surface of the tooth portion 11 of the external gear 10 is more easily damaged.

Therefore, in the present reduction gear G1, all the external gears 10 have the circumferential grooves 13 formed in the shaft end surfaces 19, 19 on both sides of the external gear 10.

Therefore, even if any one of the external gears 10 meshes in a state of being inclined with respect to the internal tooth pins 30B of the internal gear 30 due to some cause, the tooth portions 11 of the external gear 10 can be inclined with the centers of the circumferential grooves 13 formed in the two shaft end surfaces 19, 19 as fulcrums. Therefore, substantially the entire surface of each external gear 10 in the axial direction of the tooth portion 11 can be more uniformly brought into contact with (meshed with) the internal tooth pin 30B, and damage to the tooth surface of the tooth portion 11 of the external gear 10 can be further suppressed.

In the present reduction gear G1, the circumferential grooves 13 are formed "between the teeth 11 and the through-holes 12 in the two axial end surfaces 19, 19 of the external gear 10". That is, the external gear 10 has an axially-perpendicular outer axial end face 17(19) having a thickness W17 larger than the thickness W15 at the deepest portion Md of the circumferential groove 13 formed around the entire circumference between the circumferential groove 13 and the tooth portion 11, and has an axially-perpendicular inner axial end face 18(19) having a thickness larger than the thickness W15 at the deepest portion Md of the circumferential groove 13 formed around the entire circumference between the circumferential groove 13 and the through-hole 12.

In other words, the circumferential groove 13 of the external gear 10 is not merged with any one of the tooth portion 11 and the through-hole 12 of the external gear 10 over the entire circumference. Therefore, such inclination of the tooth portions 11 can be tolerated, and the strength drop of the external gear 10 can be effectively suppressed.

The specific shape or formation of the circumferential groove of the reduction gear of the present invention is not limited to the above example. Fig. 5 (a) to (F) are graphs showing relationships between various forming examples of the circumferential groove and the surface pressure of the axial end portion of the external gear.

Fig. 5 (a) corresponds to the circumferential groove 13 employed in the above embodiment.

As described above, the circumferential groove 13 of (a) has the outer side wall surface 14, and the outer side wall surface 14 is inclined at the angle θ 14 with respect to the axial direction so as to approach the axial center C10 of the external gear 10 toward the axial center P10 of the external gear 10. Therefore, the occurrence of concentration of internal stress in the external gear 10 can be effectively suppressed.

The circumferential groove 13 of (a) has an inner wall surface 16, and the inner wall surface 16 is inclined at an angle θ 16 with respect to the axial direction so as to be away from the axial center C10 of the external gear 10 toward the axial center P10 of the external gear 10. Therefore, the concentration of internal stress generated in the external gear 10 can be suppressed in cooperation with the outer wall surface 16.

In the circumferential groove 13 of (a), the inner wall surface 16 is inclined at an angle θ 16 larger than the angle θ 14 at which the outer wall surface 14 is inclined with respect to the axial direction, and the circumferential groove 13 of (a) has a bottom surface 15 perpendicular to the axial direction. Therefore, when the same tilting load is applied to the external gear 10, the tooth portions 11 can be more effectively tilted.

From the chart it can be confirmed that: the edge face pressure (meshing face pressure at the axial end portion) of the external gear 10 formed with the circumferential groove 13 of (a) is reduced by approximately 10% or so as compared with the external gear 10X of (X) (not formed with the circumferential groove). Therefore, it can be said that the circumferential groove 13 of (a) is a circumferential groove that is balanced in terms of both reduction of the edge surface pressure and reduction of the internal stress concentration. Further, for example, the shape is easier to process than the shape (E) described later.

Here, the circumferential grooves 13B to 13F of the other (B) to (F) will be briefly described. Circumferential grooves 13B to 13F are symmetrically formed on the load side and the opposite load side of each of the external gears 10B to 10F.

In the circumferential groove 13B of (B), the outer side wall surface 14B is inclined with respect to the axial direction so as to approach the axial center of the external gear 10B as it goes toward the axial center of the external gear 10B. The inclination angle of the outer wall surface 14B is 45 degrees, which is larger than the inclination angle θ 14(22.5 degrees) of the outer wall surface 14 of the circumferential groove 13 of (a). (B) Has a bottom surface 15B, and the bottom surface 15B is formed longer in the radial direction than the bottom surface 15 of the circumferential groove 13 of (a). The inner wall surface 16B of the circumferential groove 13B of (B) is formed parallel to the axis. The effect of reducing the edge face pressure of the circumferential groove 13B of (B) is slightly inferior (7% to 8% reduction from the external gear 10X) to that of the circumferential groove 13 of (a). However, although not shown in the graph, it is confirmed that the concentration of the internal stress when the tooth portion 11B of the external gear 10B is inclined tends to be smaller than that of the circumferential groove 13 of (a).

In the circumferential groove 13C of (C), the relationship between the outer side wall surface 14C and the inner side wall surface 16C is opposite to (B). That is, the outer wall surface 14C is parallel to the axis, and the inner wall surface 16C is inclined at 45 degrees with respect to the axial direction so as to be away from the axial center of the external gear 10C toward the axial center of the external gear 10. The effect of reducing the edge face pressure of the circumferential groove 13C of (C) is greater than that of the

circumferential grooves

13, 13B of (a), (B) (reduction by about 15% compared to the external gear 10X). However, it is confirmed that the concentration of internal stress when the tooth portion 11C of the external gear 10C is inclined is more likely to increase than the

circumferential grooves

13, 13B of (a), (B).

In the circumferential groove 13D of (D), the outer side wall surface 14D is inclined at 45 degrees with respect to the axial direction so as to approach the axial center of the external gear 10D as it goes toward the axial center of the external gear 10D. The inner wall surface 16D of the circumferential groove 13D in (D) is inclined at 45 degrees with respect to the axial direction so as to be away from the axial center of the external gear 10D toward the axial center of the external gear 10D. The outer wall surface 14D and the inner wall surface 16D meet at a deepest portion 15 DMd. That is, the circumferential groove 13D of (D) has no bottom surface. The effect of reducing the edge face pressure of the circumferential groove 13D in this step (D) is small (reduced by about 5% compared to the external gear 10X). However, since the bottom surface is not provided, the processing can be performed more easily.

In the circumferential groove 13E of (E), the outer wall surface 14E and the inner wall surface 16E are formed in an arc shape having a cross section parallel to the axis of 4-1 of the circumference. Specifically, the outer wall surface 14E of the circumferential groove 13E in (E) is formed by a circular arc cross section inclined with respect to the axial direction so as to approach the axial center of the external gear 10E toward the axial center of the external gear 10E. The inner side wall surface 16E is formed of a circular arc cross section inclined with respect to the axial direction so as to be away from the axial center of the external gear 10E toward the axial center of the external gear 10E. The circumferential groove 13E of (E) also has no bottom surface. It was confirmed that the effect of reducing the edge surface pressure and the effect of reducing the internal stress concentration of the circumferential groove 13E of (E) were improved as compared with the circumferential groove 13D of (D).

In the circumferential groove 13F of (F), the outer wall surface 14F and the inner wall surface 16F are both formed by surfaces parallel to the axis. The bottom surface 15F is formed of a surface perpendicular to the axis. Of the

circumferential grooves

13, 13B to 13F of (a) to (F), the effect of reducing the edge surface pressure of the circumferential groove 13F of (F) is the greatest. However, it was confirmed that the concentration of the internal stress was lower than that of the circumferential groove 13 of (a).

If these are comprehensively judged (from the viewpoint of reduction of the edge contact pressure, avoidance of concentration of internal stress, and easiness of machining, etc.), it is considered that the circumferential groove 13 of (a) is the most preferable shape among the

circumferential grooves

13, 13B to 13F of (a) to (F), and therefore the circumferential groove 13 of (a) is adopted in the reduction gear G1.

However, as described above, the shape of the circumferential groove of the present invention is not particularly limited (only the shape of (a) is not recommended). For example, in addition to the shapes (a) to (C) or (F), a small arc portion (a boundary formed by a small curved surface) may be formed at least at one of the boundary between the outer wall surface and the bottom surface and the boundary between the inner wall surface and the bottom surface. This can reduce the concentration of internal stress more greatly.

When the inventors' examinations of the shapes of the circumferential grooves (a) to (F) and the shapes of the circumferential grooves other than the circumferential grooves (a) to (F) are summarized, the following tendency can be qualitatively pointed out.

The effect of reducing the edge face pressure increases as the radial dimension of the outer axial end face of the external gear (L17: the radial dimension from the tooth root of the tooth of the external gear to the axial end of the outer wall face of the circumferential groove) decreases. However, if the radial dimension of the outer axial end surface of the external gear is short, the strength of the tooth portion of the external gear tends to decrease. Therefore, the radial dimension of the outer axial end surface is preferably about 10% to 30%, more preferably about 15% to 25%, of the tooth width (axial width) of the tooth portion of the external gear.

The smaller the inclination angle (θ 14) of the outer wall surface of the circumferential groove, the greater the effect of reducing the edge pressure. However, if the inclination angle of the outer wall surface of the circumferential groove is small, the concentration of the internal stress tends to increase. Therefore, the inclination angle of the outer wall surface is preferably about 10 to 45 degrees, and more preferably about 15 to 30 degrees.

The effect of reducing stress concentration increases as the inclination angle (θ 16) of the inner wall surface of the circumferential groove increases. However, the inclination angle of the inner side wall surface of the circumferential groove has little influence on the reduction of the edge face pressure. Therefore, the internal stress concentration, the strength, and the like of the entire external gear can be appropriately set in consideration of the overall internal stress.

The deeper the depth (D17, D18) of the deepest part of the circumferential groove, the greater the effect of reducing the edge surface pressure. However, if the depth of the deepest portion of the circumferential groove becomes deeper, the strength of the external gear (particularly, the bending strength of the tooth portion) tends to decrease. Therefore, the depth of the deepest portion is preferably 15% to 40%, more preferably 20% to 30%, of the tooth width of the external gear.

In addition, in the above embodiment, the circumferential groove is formed in a ring shape continuously circling one turn in the circumferential direction. However, a part of the circumferential groove in the circumferential direction may be broken (a part where the circumferential groove is not formed may be present in a part in the circumferential direction). In this case, it is preferable that no circumferential groove is formed at a position corresponding to a circumferential position where the through-hole exists. This allows the portion where the circumferential groove is not formed to function as a rib, thereby suppressing a decrease in strength in the vicinity of the through-hole.

In the above embodiment, the external gear has the through-hole through which the inner pin and the inner roller pass. However, in the eccentric oscillating type reduction gear device having the carriers on both sides in the axial direction of the external gear, for example, the through-hole formed in the external gear may be a through-hole through which the carrier pin connected to the carriers provided on both sides in the axial direction of the external gear passes. The through-hole according to the present invention also includes such a through-hole.

In the above embodiment, the reduction gear is of a type in which only one crank shaft is provided on the axial center of the internal gear, and the external gear is oscillated via the eccentric portion of the eccentric body provided on the one crank shaft. However, in an eccentric oscillating type reduction gear, there is also known a reduction gear including a plurality of crankshafts provided at positions offset from the axis of the internal gear, the plurality of crankshafts rotating synchronously to oscillate the external gear. The present invention can be applied to such an eccentric oscillation type reduction gear (having a plurality of crankshafts), and can obtain the same operational effects.

Further, an eccentric oscillating type reduction gear is known in which the axis of the external gear is fixed and the axis of the internal gear oscillates. The present invention can be applied to such an eccentric oscillating type reduction gear device in which the internal gear oscillates, and can obtain the same operational effects.

Claims

1. An eccentric oscillating type reduction gear device, comprising: an outer gear; an internal gear internally meshed with the external gear; and a crankshaft for eccentrically oscillating the external gear, characterized in that,

the outer gear has: a tooth portion formed with external teeth; a through hole provided at a position offset from the axis center of the external gear; and a circumferential groove provided between the tooth portion and the through hole in both axial end surfaces of the external gear,

the circumferential grooves of the two end surfaces of the external gear overlap with each other when viewed in the axial direction, and the circumferential grooves of the two end surfaces of the external gear do not overlap with each other when viewed in the radial direction,

the circumferential groove has an inner sidewall surface and an outer sidewall surface,

the inner side wall surface is inclined with respect to the axial direction so as to be away from the axial center of the external gear toward the axial center of the external gear,

the inner side wall surface is inclined at a larger angle with respect to the axial direction than the outer side wall surface.

2. The eccentric oscillating type reduction gear according to claim 1,

the outer side wall surface is inclined with respect to the axial direction so as to approach the axial center of the external gear toward the axial center of the external gear.

3. The eccentric oscillating type reduction gear according to claim 1 or 2,

the circumferential groove has a bottom surface perpendicular to the axial direction.

4. An eccentric oscillating type reduction gear device, comprising: an outer gear; an internal gear internally meshed with the external gear; and a crankshaft for eccentrically oscillating the external gear, characterized in that,

the circumferential groove has an outer side wall surface,

the outer side wall surface is inclined with respect to the axial direction so as to approach the axial center of the external gear toward the axial center of the external gear,

the eccentric oscillating type reduction gear device includes a plurality of the external gears in an axial direction, and

an insert ring for limiting the axial position of each external gear is provided between the external gears,

the circumferential groove does not overlap with the insert ring when viewed axially.