CN118293188A - Internally engaged planetary gear device and joint device for robot - Google Patents

Abstract

The invention provides an internal joint planetary gear device and a joint device for a robot, which are unlikely to reduce reliability. The ring gear planetary gear device (1A) includes an internal gear (2), a planetary gear (3), and a bearing member (6). The bearing member (6) has an inner ring (61) and an outer ring (62). In the ring gear device (1A), the planetary gear (3) is caused to oscillate, so that the planetary gear (3) rotates relative to the internal gear (2), and the outer ring (62) rotates relative to the inner ring (61) about the rotation axis (Ax 1). A gap is provided between the inner ring (61) and the outer ring (62) in the axial direction along the rotation axis (Ax 1), and a pre-compression force is applied between the inner ring (61) and the outer ring (62) by an elastic portion (8) so as to fill the gap.

Description

Internally engaged planetary gear device and joint device for robot

Technical Field

The present invention relates generally to a ring gear device and a joint device for a robot, and more particularly to a ring gear device and a joint device for a robot each having a planetary gear with external teeth disposed on the inner side of a internally toothed gear with internal teeth.

Background

As a related art, an eccentric oscillating type ring gear device called a split type is known (for example, refer to patent document 1). In the ring gear planetary gear device of the related art, a plurality of (for example, 3) crankshafts are provided at positions offset from the axial center of the internal gear, and each crankshaft is synchronously driven by a crank gear, whereby the planetary gear (external gear) is ring-meshed with the internal gear while swinging.

The planetary gears include a first planetary gear and a second planetary gear. A pair of carriers are disposed on both axial sides of the first planetary gear and the second planetary gear. Each crankshaft is supported by a pair of brackets through a pair of tapered roller bearings. When the input gear rotates, 3 crank gears simultaneously engaged with the input gear rotate in the same direction and at the same rotational speed. Since the crankshafts are spline-connected to the respective crankshaft gears, the 3 crankshafts rotate in the same direction and at the same rotational speed in a state where the number of teeth is reduced with respect to the number of teeth of the input gear and the crankshaft gear. As a result, the 3 first eccentric portions formed at the same position in the axial direction of the 3 crankshafts oscillate the first planetary gears in synchronization with rotation, and the 3 second eccentric portions formed at the same position in the axial direction of the 3 crankshafts oscillate the second planetary gears in synchronization with rotation.

The first planetary gear and the second planetary gear are respectively in internal engagement with the internal gear. The internal gear has: a gear body; and a pin (pin member) rotatably incorporated into the gear body and constituting the internal teeth of the internal gear. Here, the number of teeth (the number of pins) of the internal gear is slightly larger than the number of teeth of each planetary gear. Therefore, each time each planetary gear oscillates, the first planetary gear and the second planetary gear generate a circumferential phase shift (rotation) of the difference in number of teeth with respect to the internal gear, and the rotation is transmitted to the pair of carriers as revolution about the rotation axis of the internal gear of each crankshaft. This enables the pair of brackets to rotate relative to the gear body (the case integrated therewith) about the rotation axis.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication 2016-75354

Disclosure of Invention

Technical problem to be solved by the invention

In the structure of the related art described above, there is a possibility that the pre-compression falls off due to wear or the like of the components in operation of the ring gear apparatus, and the reliability is lowered.

The purpose of the present disclosure is to provide an internal joint planetary gear device and a joint device for a robot, which are unlikely to be degraded in reliability.

Solution for solving the technical problems

An internally meshed planetary gear device of an aspect of the present disclosure includes an internally toothed gear, a planetary gear, and a bearing member. The internal gear has internal teeth. The planetary gear has external teeth that mesh with the internal teeth locally. The bearing member has an inner race and an outer race. In the ring gear device, the planetary gears are rotated relative to the internal gear by swinging the planetary gears, and the outer ring is rotated relative to the inner ring around a rotation axis. A gap is provided between the inner ring and the outer ring in an axial direction along the rotary shaft, and a pre-compression force is applied between the inner ring and the outer ring by an elastic portion so as to fill the gap.

The robot joint device according to one embodiment of the present disclosure includes: the inner gearing planetary gear device; a first member fixed to the internal gear; and a second member that rotates relative to the first member in association with the relative rotation of the planetary gear to the internal gear.

Effects of the invention

According to the present disclosure, an internal joint planetary gear device and a robot joint device, which are less likely to be degraded in reliability, can be provided.

Drawings

Fig. 1 is a perspective view showing a schematic structure of an actuator including a basic structure of an internal gear planetary gear device.

Fig. 2 is a schematic exploded perspective view of the ring gear device as described above, as seen from the input side of the rotary shaft.

Fig. 3 is a schematic exploded perspective view of the ring gear device as described above, as seen from the output side of the rotary shaft.

Fig. 4 is a schematic cross-sectional view of the ring gear device.

Fig. 5 is a sectional view taken along line A1-A1 of fig. 4 showing the ring gear apparatus described above.

Fig. 6 is a sectional view taken along line B1-B1 of fig. 4 showing the ring gear apparatus described above.

Fig. 7 is a schematic cross-sectional view of the ring gear device according to the first embodiment.

Fig. 8 is a schematic enlarged view of a region Z1 in fig. 7, showing a main portion of the ring gear device.

The main part of the ring gear planetary gear device of the comparative example shown in fig. 9 is a schematic enlarged view corresponding to the region Z1 of fig. 7.

Fig. 10 is a schematic view showing a joint device for a robot using the ring gear device.

Fig. 11 is a schematic enlarged view of a region Z1 corresponding to fig. 7, showing a main part of the ring gear device according to the second embodiment.

Detailed Description

(Basic structure)

(1) Summary of the inventionsummary

Hereinafter, an outline of the ring gear planetary gear device 1 of the present basic structure will be described with reference to fig. 1 to 4. The drawings to which the present invention refers are schematic drawings, and the ratios of the sizes and thicknesses of the respective constituent elements in the drawings do not necessarily reflect actual dimensional ratios. For example, the tooth shapes, sizes, and the number of teeth of the internal teeth 21 and the external teeth 31 in fig. 1 to 4 are shown schematically for the sake of illustration, and the gist thereof is not limited to the illustrated shape.

The ring gear planetary gear device 1 (hereinafter, also simply referred to as "gear device 1") of the present basic structure is a gear device including an internal gear 2 and a planetary gear 3. In the gear device 1, the planetary gear 3 is arranged inside the annular internal gear 2, and the planetary gear 3 is oscillated, whereby the planetary gear 3 is rotated relative to the internal gear 2. The ring gear device 1 further includes a bearing member 6, and the bearing member 6 has an outer ring 62 and an inner ring 61. The inner race 61 is disposed inside the outer race 62 and is supported so as to be rotatable relative to the outer race 62. In particular, the gear device 1 of the present basic structure is an eccentric oscillating type ring gear device called a split type.

As shown in fig. 1 to 4, the gear device 1 of the present basic structure includes a plurality of (3 in the basic structure) crankshafts (eccentric shafts) 7A, 7B, 7C disposed at positions offset from the axial center (rotation axis Ax 1) of the internal gear 2. Further, the gear device 1 includes an input shaft 500 disposed on the shaft center (rotation axis Ax 1) of the internal gear 2 and centered on the rotation axis Ax1, and an input gear 501 integrally formed with the input shaft 500. The crank gears 502A, 502B, 502C are respectively spline-coupled to the plurality of crankshafts 7A, 7B, 7C. These plurality (3 in basic structure) of crank gears 502A, 502B, 502C are arranged so as to mesh with the input gear 501. Therefore, when the input shaft 500 is driven, the gear device 1 swings the planetary gears 3 by synchronously driving the crankshafts 7A, 7B, 7C with the input gear 501.

The internally toothed gear 2 has internal teeth 21 and is fixed to the outer ring 62. In particular, in the present basic structure, the internal gear 2 has an annular gear body 22 and a plurality of pins 23. The plurality of pins 23 are rotatably held by the inner peripheral surface 221 of the gear body 22 to constitute the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. That is, the planetary gear 3 is inscribed in the internal gear 2 inside the internal gear 2, and a part of the external teeth 31 meshes with a part of the internal teeth 21. In this state, when the plurality of crankshafts 7A, 7B, and 7C are driven, the planetary gear 3 swings, the meshing positions of the internal teeth 21 and the external teeth 31 move in the circumferential direction of the internal gear 2, and relative rotation corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2 occurs between the two gears (the internal gear 2 and the planetary gear 3). Here, if the internal gear 2 is fixed, the planetary gear 3 rotates (rotates) with the relative rotation of the two gears. As a result, a rotational output can be obtained from the planetary gear 3, which is decelerated at a relatively high reduction ratio according to the difference in the number of teeth between the two gears.

This gear device 1 is used in the following manner: the rotation of the planetary gear 3 corresponding to the rotation component is taken out as the rotation of the pair of brackets 18, 19 integrated with the inner ring 61 of the bearing member 6. Thus, the gear device 1 functions as a gear device having a relatively high reduction ratio with the input shaft 500 as an input side and the pair of brackets 18 and 19 as an output side. Therefore, in the gear device 1 of the present basic structure, the plurality of crankshafts 7A, 7B, 7C are supported by the pair of brackets 18, 19 in order to transmit the rotation corresponding to the rotation component of the planetary gear 3 to the pair of brackets 18, 19. The pair of brackets 18, 19 are disposed on both sides in the axial direction (direction along the rotation axis Ax 1) of the planetary gear 3, and rotatably support the respective crankshafts 7A, 7B, 7C.

Here, the plurality of crankshafts 7A, 7B, 7C are inserted into the plurality of openings 33 formed in the planetary gear 3, respectively, and rotate relative to the internal gear 2 in accordance with the rotation of the planetary gear 3. Each of the crankshafts 7A, 7B, and 7C has a shaft portion 71 and an eccentric portion 72 eccentric to the shaft portion 71. The pair of brackets 18, 19 rotatably support the shaft center portion 71 of each of the crankshafts 7A, 7B, 7C, and the eccentric portion 72 of each of the crankshafts 7A, 7B, 7C is inserted into the opening portion 33 of the planetary gear 3. Therefore, the oscillation component of the planetary gear 3, that is, the revolution component of the planetary gear 3 is absorbed by the revolution component of the eccentric portion 72 with respect to the shaft portion 71. In other words, the eccentric portions 72 of the shaft center portions 71 of the crankshafts 7A, 7B, and 7C rotate so as to revolve around the shaft center portions 71, respectively, to absorb the oscillation component of the planetary gear 3. Therefore, the rotation (rotation component) of the planetary gear 3, in addition to the oscillation component (revolution component) of the planetary gear 3, is transmitted to the pair of carriers 18, 19 by the plurality of crankshafts 7A, 7B, 7C.

As shown in fig. 1, the gear device 1 of the present basic structure forms an actuator 100 together with a drive source 101. In other words, the actuator 100 of the present basic structure includes the gear device 1 and the drive source 101. The drive source 101 generates a drive force for swinging the planetary gear 3. Specifically, the driving source 101 rotates the input shaft 500 about the rotation axis Ax1, thereby swinging the planetary gear 3.

(2) Definition of the definition

The "annular shape" in the present disclosure means a shape such as a ring (loop) forming a space (region) surrounded on the inside at least in a plan view, and is not limited to a circular shape (annular shape) which is a perfect circle in a plan view, and may be, for example, an elliptical shape, a polygonal shape, or the like. Further, for example, even if the cup-like shape has a bottom, the ring-like shape is included in the "ring-like shape" as long as the peripheral wall thereof is annular.

The term "revolution" as used herein means a rotation of an object around a rotation axis other than a center axis passing through the center (center of gravity) of the object, and when the object revolves, the center of the object moves along a revolution orbit centered on the rotation axis. Therefore, for example, when a certain object rotates around an eccentric shaft parallel to a central axis passing through the center (center of gravity) of the object, the object revolves around the eccentric shaft as a rotation axis. As an example, the planetary gear 3 revolves around the rotation shaft Ax1 in the ring gear 2 by swinging.

In the disclosure, one side (left side in fig. 4) of the rotation shaft Ax1 is referred to as an "output side", and the other side (right side in fig. 4) of the rotation shaft Ax1 is referred to as an "input side". In the example of fig. 4, rotation is imparted to the input shaft 500 from the "input side" of the rotation shaft Ax1, and rotation of the pair of brackets 18, 19 is extracted from the "output side" of the rotation shaft Ax 1. However, the "input side" and the "output side" are labels given for the sake of explanation, and the gist of the present invention is not limited to the positional relationship between input and output as viewed from the gear device 1.

The term "rotation axis" as used herein refers to an axis (straight line) which becomes a virtual center of the rotational motion of the rotating body. That is, the rotation axis Ax1 is a virtual axis not accompanied with an entity. The input shaft 500 rotates about the rotation axis Ax 1.

The terms "internal teeth" and "external teeth" as used in this disclosure refer to a collection (set) of a plurality of "teeth" rather than individual "teeth", respectively. That is, the internal teeth 21 of the internal gear 2 are formed of a collection of a plurality of teeth arranged on the inner peripheral surface 221 of the internal gear 2 (the gear body 22). Similarly, the external teeth 31 of the planetary gear 3 are formed by a plurality of teeth arranged on the outer peripheral surface of the planetary gear 3.

(3) Structure of the

The following describes a detailed configuration of the ring gear planetary gear device 1 according to the present basic configuration with reference to fig. 1 to 6.

Fig. 1 is a perspective view showing a schematic configuration of an actuator 100 including a gear device 1. In fig. 1, a driving source 101 is schematically shown. Fig. 2 is a schematic exploded perspective view of the gear device 1 as seen from the input side of the rotation shaft Ax 1. Fig. 3 is a schematic exploded perspective view of the gear device 1 as seen from the output side of the rotation shaft Ax 1. Fig. 4 is a schematic cross-sectional view of the gear device 1. Fig. 5 is a sectional view taken along line A1-A1 of fig. 4. Fig. 6 is a sectional view taken along line B1-B1 of fig. 4. In fig. 5 and 6, the members other than the crankshafts 7A, 7B, and 7C are also cross-sectioned, but cross-hatching is omitted.

(3.1) Integral Structure

As shown in fig. 1 to 4, the gear device 1 of the present basic structure includes an internal gear 2, a planetary gear 3, a bearing member 6, a plurality of crankshafts 7A, 7B, 7C, a pair of brackets 18, 19, and an input shaft 500. In addition, in the present basic structure, the gear device 1 further includes an input gear 501, a plurality of crank gears 502A, 502B, 502C, a pair of rolling bearings 41, 42, an eccentric body bearing 5, and a housing 10. In the present basic structure, the internal gear 2, the planetary gear 3, the plurality of crankshafts 7A, 7B, 7C, the pair of brackets 18, 19, and the like, which are constituent elements of the gear device 1, are made of stainless steel, cast iron, carbon steel for mechanical structure, chromium molybdenum steel, phosphor bronze, aluminum bronze, or other metal, or aluminum, titanium, or other light metal. The metal herein includes a metal subjected to a surface treatment such as nitriding treatment.

In the present basic configuration, an internally tangent planetary gear reducer using cycloid tooth profiles is exemplified as an example of the gear device 1. That is, the gear device 1 of the present basic structure includes the inscribed planetary gear 3 having the cycloid-like curve tooth form.

In the present basic configuration, the gear device 1 is used in a state where the gear body 22 of the ring gear 2 is fixed to a fixing member such as the housing 10 together with the outer ring 62 of the bearing member 6, for example. As a result, the planetary gear 3 rotates relative to the fixed member (the case 10, etc.) with the relative rotation of the internal gear 2 and the planetary gear 3.

Further, in the present basic structure, when the gear device 1 is used for the actuator 100, the rotational force as an input is applied to the input shaft 500, whereby the rotational force as an output is taken out from the pair of brackets 18, 19 integrated with the inner race 61 of the bearing member 6. That is, the gear device 1 operates with the rotation of the input shaft 500 as an input rotation and the rotation of the pair of brackets 18 and 19 integrated with the inner race 61 as an output rotation. Thus, in the gear device 1, an output rotation that is decelerated at a relatively high reduction ratio with respect to an input rotation can be obtained.

The drive source 101 is a power generation source such as an electric motor (motor). The power generated by the drive source 101 is transmitted to the input shaft 500 in the gear device 1. Specifically, the drive source 101 is connected to the input shaft 500, and power generated by the drive source 101 is transmitted to the input shaft 500. Thereby, the driving source 101 can rotate the input shaft 500.

Further, in the gear device 1 of the present basic structure, as shown in fig. 4, the rotation axis Ax1 on the input side and the rotation axis Ax1 on the output side are on the same line. In other words, the input-side rotation axis Ax1 is coaxial with the output-side rotation axis Ax 1. Here, the input-side rotation axis Ax1 is the rotation center of the input shaft 500 to which the input rotation is given, and the output-side rotation axis Ax1 is the rotation center of the inner ring 61 (and the pair of brackets 18, 19) that generates the output rotation. That is, in the gear device 1, it is possible to obtain an output rotation that is decelerated at a relatively high reduction ratio with respect to an input rotation on the same axis.

As shown in fig. 5 and 6, the internal gear 2 is an annular member having internal teeth 21. In the present basic structure, the internal gear 2 has an annular shape with at least an inner peripheral surface that is perfectly circular in plan view. An inner tooth 21 is formed along the circumferential direction of the internal gear 2 on the inner circumferential surface of the annular internal gear 2. The plurality of teeth constituting the internal teeth 21 are all of the same shape and are provided at equal intervals over the entire circumferential direction of the inner circumferential surface of the internal gear 2. That is, the pitch circles of the internal teeth 21 are perfect circles in a plan view. The center of the pitch circle of the internal teeth 21 is on the rotation axis Ax 1. The internal gear 2 has a predetermined thickness along the direction of the rotation axis Ax 1. The tooth directions of the internal teeth 21 are all parallel to the rotation axis Ax 1. The dimension of the internal teeth 21 in the tooth direction is slightly smaller than the thickness direction of the internal gear 2.

Here, as described above, the internal gear 2 has the annular (circular ring-shaped) gear body 22 and the plurality of pins 23. The plurality of outer pins 23 are rotatably held on the inner peripheral surface 221 of the gear body 22, and constitute the internal teeth 21. In other words, the plurality of pins 23 function as a plurality of teeth constituting the internal teeth 21, respectively. Specifically, as shown in fig. 2, a plurality of inner peripheral grooves 223 are formed in the entire circumferential direction of the inner peripheral surface 221 of the gear body 22. The plurality of inner peripheral grooves 223 are all of the same shape and are disposed at equal intervals. The plurality of inner peripheral grooves 223 are each formed parallel to the rotation axis Ax1 over the entire length of the gear body 22 in the thickness direction. The plurality of pins 23 are assembled to the gear body 22 so as to be fitted into the plurality of inner peripheral grooves 223. Each of the plurality of pins 23 is held in a state capable of rotating in the inner peripheral groove 223. In addition, the gear main body 22 (together with the outer race 62) is fixed to the housing 10. Further, a plurality of fixing holes 222 for fixing are formed in the gear body 22 (see fig. 5).

As shown in fig. 5 and 6, the planetary gear 3 is an annular member having external teeth 31. In the present basic structure, the planetary gear 3 has an annular shape having a perfect circle in plan view to the outer peripheral surface. An outer tooth 31 is formed on the outer peripheral surface of the annular planetary gear 3 along the circumferential direction of the planetary gear 3. The plurality of teeth constituting the external teeth 31 are all of the same shape and are provided at equal intervals over the entire circumferential direction of the outer peripheral surface of the planetary gear 3. That is, the pitch circle of the external teeth 31 is a perfect circle in a plan view. The planetary gear 3 has a predetermined thickness along the direction of the rotation axis Ax 1. The external teeth 31 are formed over the entire length of the planetary gear 3 in the thickness direction. The tooth directions of the external teeth 31 are all parallel to the rotation axis Ax 1. In the planetary gear 3, unlike the internal gear 2, the external teeth 31 are integrally formed with the body of the planetary gear 3 from one metal member.

In addition, the gear device 1 of the present basic structure includes a plurality of planetary gears 3. Specifically, the gear device 1 includes two planetary gears 3, that is, a first planetary gear 301 and a second planetary gear 302. The 2 planetary gears 3 are arranged so as to face each other in a direction parallel to the rotation axis Ax 1. That is, the planetary gear 3 includes a first planetary gear 301 and a second planetary gear 302 juxtaposed in a direction (axial direction) parallel to the rotation axis Ax 1. The shapes of the first planetary gear 301 and the second planetary gear 302 are common to themselves.

These two planetary gears 3 (first planetary gear 301 and second planetary gear 302) are arranged 180 degrees apart around the rotation axis Ax 1. In the example of fig. 4, the center (center of the pitch circle of the external teeth 31) C1 of the first planetary gear 301 located on the input side (right side in fig. 4) of the rotation axis Ax1 among the first planetary gear 301 and the second planetary gear 302 is in a state of being deviated (offset) upward in the drawing with respect to the rotation axis Ax 1. On the other hand, the center (center of the pitch circle of the external teeth 31) C2 of the second planetary gear 302 located on the output side (left side in fig. 4) of the rotation shaft Ax1 is in a state of being deviated (offset) downward in the drawing with respect to the rotation shaft Ax 1. Here, the distance Δl1 between the rotation axis Ax1 and the center C1 is an eccentric amount of the first planetary gear 301 with respect to the rotation axis Ax1, and the distance Δl2 between the rotation axis Ax1 and the center C2 is an eccentric amount of the second planetary gear 302 with respect to the rotation axis Ax 1. In this way, the plurality of planetary gears 3 are equally arranged in the circumferential direction around the rotation axis Ax1, and thus the weight and load balance between the plurality of planetary gears 3 can be achieved.

In the first planetary gear 301 and the second planetary gear 302, their centers C1, C2 are located at 180 degrees of rotational symmetry with respect to the rotation axis Ax 1. In the present basic structure, the directions of the eccentric amounts Δl1 and Δl2 as viewed from the rotation axis Ax1 are opposite, but the absolute values thereof are the same.

More specifically, each of the crankshafts 7A, 7B, and 7C has 2 eccentric portions 72 with respect to the 1-axis portion 71. The amounts Δl0 (see fig. 5 and 6) of eccentricity of the center C0 of the 2 eccentric portions 72 from the center (axis Ax 2) of the axial center portion 71 are the same as the amounts Δl1, Δl2 of eccentricity of the first planetary gear 301 and the second planetary gear 302 with respect to the rotation axis Ax1, respectively. The shapes of the plurality of crankshafts 7A, 7B, 7C are themselves common. Regarding the plurality of crank gears 502A, 502B, 502C, their shapes are themselves common.

Further, a pair of carriers 18 and 19 are disposed on both sides of the first planetary gear 301 and the second planetary gear 302 in a direction (axial direction) parallel to the rotation axis Ax 1. When the pair of brackets 18 and 19 are distinguished from each other, the bracket 18 located on the input side (right side in fig. 4) of the rotation shaft Ax1 is referred to as an "input side bracket 18", and the bracket 19 located on the output side (left side in fig. 4) of the rotation shaft Ax1 is referred to as an "output side bracket 19". Both ends of each crankshaft 7A, 7B, 7C are held by a pair of brackets 18, 19 via rolling bearings 41, 42. That is, the crankshafts 7A, 7B, 7C are rotatably held by the input side carrier 18 and the output side carrier 19 on both sides of the planetary gear 3 in a direction (axial direction) parallel to the rotation axis Ax 1.

Eccentric body bearings 5 are mounted on eccentric portions 72 of the crankshafts 7A, 7B, and 7C. The first planetary gear 301 and the second planetary gear 302 have 3 openings 33 corresponding to the 3 crankshafts 7A, 7B, and 7C, respectively. Further, the eccentric body bearing 5 is accommodated in each opening 33. In other words, the eccentric body bearings 5 are mounted on the first planetary gear 301 and the second planetary gear 302, respectively, and the crankshafts 7A, 7B, 7C are inserted into the eccentric body bearings 5, whereby the eccentric body bearings 5 and the crankshafts 7A, 7B, 7C are combined with the planetary gear 3. In a state where the planetary gear 3 is combined with the eccentric body bearing 5 and the crankshafts 7A, 7B, 7C, when the crankshafts 7A, 7B, 7C rotate, the planetary gear 3 swings about the rotation axis Ax 1.

According to the configuration described above, the input shaft 500 is rotated about the rotation axis Ax1 by applying the rotation force as the input to the input shaft 500, and the rotation force is distributed from the input gear 501 to the plurality of crankshafts 7A, 7B, and 7C. That is, when the input gear 501 rotates, the 3 crank gears 502A, 502B, 502C that are simultaneously engaged with the input gear 501 rotate in the same direction and at the same rotational speed. Since the crankshafts 7A, 7B, and 7C are spline-coupled to the respective crank gears 502A, 502B, and 502C, the 3 crankshafts 7A, 7B, and 7C rotate in the same direction and at the same rotational speed in a state where the gear ratios of the input gear 501 and the crank gears 502A, 502B, and 502C are reduced. As a result, the 3 eccentric portions 72 formed at the same position on the input side of the rotation shaft Ax1 among the 3 crankshafts 7A, 7B, 7C are rotated in synchronization, and the first planetary gear 301 is caused to oscillate. Further, out of the 3 crankshafts 7A, 7B, 7C, 3 eccentric portions 72 formed at the same position on the output side of the rotation shaft Ax1 are rotated in synchronization, and the second planetary gear 302 is caused to oscillate.

Fig. 5 and 6 show states of the first planetary gear 301 and the second planetary gear 302 at a certain time. Fig. 5 is a sectional view taken along line A1-A1 of fig. 4, showing the first planetary gear 301. Fig. 6 is a sectional view taken along line B1-B1 of fig. 4, showing the second planetary gears 302. As shown in fig. 5 and 6, in the first planetary gear 301 and the second planetary gear 302, centers C1 and C2 thereof are located at substantially 180-degree rotationally symmetrical positions with respect to the rotation axis Ax 1. In the present basic structure, the directions of the eccentric amounts Δl1 and Δl2 as viewed from the rotation axis Ax1 are opposite, but the absolute values thereof are substantially the same (both the eccentric amounts Δl0). According to the above configuration, the shaft center portion 71 rotates (rotates) about the shaft center Ax2, and thereby the first planetary gear 301 and the second planetary gear 302 rotate (eccentrically move) about the rotation shaft Ax1 with a phase difference of substantially 180 degrees about the rotation shaft Ax 1. The plurality of planetary gears 3 are arranged substantially uniformly in the circumferential direction around the rotation axis Ax1, and thus the weight and load between the plurality of planetary gears 3 can be balanced.

The planetary gears 3 (the first planetary gear 301 and the second planetary gear 302) configured as described above are disposed inside the internal gear 2. The planetary gear 3 is formed to be smaller than the internal gear 2 by one turn in plan view, and the planetary gear 3 can swing inside the internal gear 2 in a state of being combined with the internal gear 2. At this time, the outer peripheral surface of the planetary gear 3 is formed with the outer teeth 31, and the inner peripheral surface of the inner gear 2 is formed with the inner teeth 21. Therefore, in a state where the planetary gear 3 is disposed inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

Further, the pitch circle of the external teeth 31 is one turn smaller than the pitch circle of the internal teeth 21. In a state where the first planetary gear 301 is inscribed in the internal gear 2, the center C1 of the pitch circle of the external teeth 31 of the first planetary gear 301 is located at a position offset from the center (rotation axis Ax 1) of the pitch circle of the internal teeth 21 by a distance Δl1. Similarly, in a state where the second planetary gear 302 is inscribed in the internal gear 2, the center C2 of the pitch circle of the external teeth 31 of the second planetary gear 302 is located at a position offset from the center (rotation axis Ax 1) of the pitch circle of the internal teeth 21 by a distance Δl2.

Therefore, in either the first planetary gear 301 or the second planetary gear 302, the external teeth 31 and at least a part of the internal teeth 21 are opposed to each other with a gap therebetween, and if the difference in number of teeth between the external teeth 31 and the internal teeth 21 is "2" or more, the entire circumferential direction does not mesh with each other. However, the planetary gear 3 swings (revolves) around the rotation axis Ax1 inside the inner gear 2, and therefore the outer teeth 31 mesh with the inner teeth 21 locally. That is, by the planetary gears 3 (the first planetary gear 301 and the second planetary gear 302) swinging around the rotation axis Ax1, as shown in fig. 5 and 6, the teeth constituting part of the plurality of teeth of the external teeth 31 mesh with the teeth constituting part of the plurality of teeth of the internal teeth 21. As a result, in the gear device 1, a part of the external teeth 31 can be meshed with a part of the internal teeth 21.

Here, the number of teeth of the internal teeth 21 in the internal gear 2 is N (N is a positive integer) greater than the number of teeth of the external teeth 31 of the planetary gear 3. In the present basic configuration, N is "2", for example, and the number of teeth (of the external teeth 31) of the planetary gear 3 is "2" smaller than the number of teeth (of the internal teeth 21) of the internal gear 2. The difference in the number of teeth between the planetary gear 3 and the internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the gear device 1.

In the present basic structure, the combined thickness of the first planetary gear 301 and the second planetary gear 302 is smaller than the thickness of the gear body 22 in the internal gear 2, for example. Further, the size of the external teeth 31 of the first planetary gear 301 and the second planetary gear 302 taken together in the tooth direction (direction parallel to the rotation axis Ax 1) is smaller than the size of the internal teeth 21 in the tooth direction (direction parallel to the rotation axis Ax 1). In other words, the outer teeth 31 of the first planetary gear 301 and the second planetary gear 302 are brought within the range of the tooth direction of the inner teeth 21 in the direction parallel to the rotation axis Ax 1.

Here, the first planetary gear 301 and the second planetary gear 302 are respectively in internal mesh with the internal gear 2. Therefore, each time the first planetary gear 301 and the second planetary gear 302 oscillate, the first planetary gear 301 and the second planetary gear 302 rotate with respect to the internal gear 2 by generating a phase shift in the circumferential direction (in which the number of teeth 21 and the number of teeth 31 are different). The rotation is transmitted to the pair of brackets 18 and 19 as revolution around the axis (rotation axis Ax 1) of the internal gear 2 of each crankshaft 7A, 7B, and 7C. As a result, the pair of brackets 18 and 19 can be rotated relative to the gear main body (the integrated housing 10) about the rotation axis Ax 1.

In short, the gear device 1 of the present basic structure swings the planetary gear 3 by the plurality of crankshafts 7A, 7B, 7C disposed at positions offset from the rotation axis Ax1, and obtains a rotational output by the swing of the planetary gear 3. That is, in the gear device 1, when the planetary gear 3 oscillates, the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2, a relative rotation corresponding to the difference in the number of teeth of the planetary gear 3 and the internal gear 2 occurs between the two gears (the internal gear 2 and the planetary gear 3). Here, if the internal gear 2 is fixed, the planetary gear 3 rotates (rotates) with the relative rotation of the two gears. As a result, a rotational output can be obtained from the planetary gear 3, which is decelerated at a relatively high reduction ratio according to the difference in the number of teeth between the two gears.

The bearing member 6 has an outer ring 62 and an inner ring 61, and is used to take out the output of the gear device 1 as rotation of the inner ring 61 relative to the outer ring 62. The bearing member 6 includes a plurality of rolling elements 63 (see fig. 4) in addition to the outer ring 62 and the inner ring 61. The outer ring 62 and the inner ring 61 are annular members. The outer ring 62 and the inner ring 61 each have a circular shape that is a perfect circle in plan view. The inner ring 61 is smaller than the outer ring 62 by one turn and is disposed inside the outer ring 62. Here, since the inner diameter of the outer ring 62 is larger than the outer diameter of the inner ring 61, a gap is generated between the inner peripheral surface of the outer ring 62 and the outer peripheral surface of the inner ring 61.

The plurality of rolling elements 63 are disposed in a gap between the outer ring 62 and the inner ring 61. The plurality of rolling elements 63 are arranged in parallel in the circumferential direction of the outer ring 62. The plurality of rolling elements 63 are all metal members of the same shape, and are disposed at equal intervals over the entire circumferential direction of the outer ring 62.

In more detail, the bearing member 6 of the gear device 1 of the present basic structure includes a first bearing member 601 and a second bearing member 602. The first bearing member 601 and the second bearing member 602 are each constituted by an angular ball bearing. Specifically, as shown in fig. 4, a first bearing member 601 is disposed on the input side (right side in fig. 4) of the rotation shaft Ax1 as viewed from the planetary gear 3, and a second bearing member 602 is disposed on the output side (left side in fig. 4) of the rotation shaft Ax1 as viewed from the planetary gear 3. The bearing member 6 is configured by the first bearing member 601 and the second bearing member 602 to be resistant to a load in the radial direction, a load in the thrust direction (direction along the rotation axis Ax 1), and a bending force (bending moment load) to the rotation axis Ax 1.

Here, the first bearing member 601 and the second bearing member 602 are disposed opposite to each other with respect to the planetary gear 3 on both sides in a direction (axial direction) parallel to the rotation axis Ax1 in a direction parallel to the rotation axis Ax 1. That is, the bearing member 6 is a "combined angular ball bearing" in which a plurality of (here, 2) angular ball bearings are combined. Here, as an example, the first bearing member 601 and the second bearing member 602 are "back surface combined type" that receive a load in a thrust direction (a direction along the rotation axis Ax 1) in which the respective inner rings 61 approach each other. Further, in the gear device 1, the first bearing member 601 and the second bearing member 602 are combined in a state where appropriate pre-compression force acts on the inner race 61 by fastening the respective inner races 61 in a direction to approach each other.

In the gear device 1 of the present basic structure, the input side carrier 18 and the output side carrier 19 are disposed on both sides of the planetary gear 3 in the direction parallel to the rotation axis Ax1, and pass through the carrier holes 34 (see fig. 4) of the planetary gear 3 to be coupled to each other. Specifically, as shown in fig. 4, an input side carrier 18 is disposed on the input side (right side in fig. 4) of the rotation shaft Ax1 as viewed from the planetary gear 3, and an output side carrier 19 is disposed on the output side (left side in fig. 4) of the rotation shaft Ax1 as viewed from the planetary gear 3. The inner race 61 of the bearing member 6 (each of the first bearing member 601 and the second bearing member 602) is fixed to the input side bracket 18 and the output side bracket 19. In the present basic structure, as an example, the inner ring of the first bearing member 601 is seamlessly integrated with the input side bracket 18. Likewise, the inner ring of the second bearing member 602 is seamlessly integrated with the output side bracket 19.

The output side bracket 19 has a plurality (3, as an example) of bracket pins 191 (see fig. 2) protruding from one surface of the output side bracket 19 toward the input side of the rotation shaft Ax 1. The plurality of carrier pins 191 pass through a plurality of (for example, 3) carrier holes 34 formed in the planetary gear 3, and distal ends of the plurality of carrier pins 191 are fixed to the input side carrier 18 by carrier bolts 192 (see fig. 7). Here, a gap is secured between the holder pin 191 and the inner peripheral surface of the holder hole 34, and the holder pin 191 is movable within the holder hole 34, that is, relatively movable with respect to the center of the holder hole 34. Thus, the carrier pin 191 does not contact the inner peripheral surface of the carrier hole 34 when the planetary gear 3 swings.

With the above-described structure, the gear device 1 is used in the following manner: the rotation corresponding to the rotation component of the planetary gear 3 is taken out as the rotation of the input side carrier 18 and the output side carrier 19 integrated with the inner ring 61 of the bearing member 6. That is, in the present basic structure, the relative rotation between the planetary gear 3 and the internal gear 2 is taken out from the input side carrier 18 and the output side carrier 19. In the present basic structure, as an example, the gear device 1 is used in a state in which the outer ring 62 (see fig. 4) of the bearing member 6 is fixed to the housing 10 as a fixing member. That is, the planetary gear 3 is coupled to the input side carrier 18 and the output side carrier 19, which are rotation members, by the plurality of crankshafts 7A, 7B, 7C, and the gear body 22 is fixed to the fixed member, so that the relative rotation between the planetary gear 3 and the internal gear 2 is taken out from the rotation members (the input side carrier 18 and the output side carrier 19). In other words, in the present basic configuration, when the planetary gear 3 rotates relative to the gear main body 22, the rotational force of the input side carrier 18 and the output side carrier 19 is taken out as output.

Further, in the present basic structure, the housing 10 is seamlessly integrated with the gear main body 22 of the internal gear 2. That is, the gear main body 22 as a fixing member is continuously provided with the housing 10 without any gap in a direction parallel to the rotation axis Ax 1.

More specifically, the housing 10 is cylindrical and forms the outer contour of the gear device 1. In the present basic structure, the central axis of the cylindrical housing 10 is configured to coincide with the rotation axis Ax 1. That is, at least the outer peripheral surface of the housing 10 is a perfect circle centered on the rotation axis Ax1 in plan view (as viewed from one axial direction). The case 10 is formed in a cylindrical shape with openings at both end surfaces in the axial direction. Here, the housing 10 is seamlessly integrated with the gear body 22 of the internal gear 2, so that the housing 10 and the gear body 22 are handled as one piece. Accordingly, the inner peripheral surface of the housing 10 includes the inner peripheral surface 221 of the gear main body 22. Further, an outer ring 62 of the bearing member 6 is fixed to the housing 10. That is, the outer ring 62 of the first bearing member 601 is fixed to the input side (right side in fig. 4) of the rotation shaft Ax1 by fitting, as viewed from the gear main body 22 in the inner peripheral surface of the housing 10. On the other hand, the outer ring 62 of the second bearing member 602 is fixed to the output side (left side in fig. 4) of the rotation shaft Ax1 by fitting, as viewed from the gear main body 22 in the inner peripheral surface of the housing 10.

Further, an end surface of the rotation shaft Ax1 of the housing 10 on the input side (right side in fig. 4) is closed by an input side bracket 18, and an end surface of the rotation shaft Ax1 of the housing 10 on the output side (left side in fig. 4) is closed by an output side bracket 19. Accordingly, as shown in fig. 4, the planetary gears 3 (the first planetary gears 301 and the second planetary gears 302), the plurality of pins 23, the eccentric body bearing 5, and the like are housed in the space surrounded by the housing 10, the input side carrier 18, and the output side carrier 19.

The plurality of (3 in basic structure) crankshafts 7A, 7B, 7C have a shaft portion 71 and 2 eccentric portions 72, respectively. The shaft portion 71 has a cylindrical shape with at least an outer peripheral surface thereof being substantially circular in plan view. The axis Ax2, which is the center of the shaft portion 71, is parallel to the rotation axis Ax 1. The axial centers Ax2 of the plurality of crankshafts 7A, 7B, 7C are arranged at equal intervals in the circumferential direction on a virtual circle centered on the rotation axis Ax 1. Each eccentric portion 72 has a disc shape with at least an outer peripheral surface having a perfect circle when the garment is viewed. The center (central axis) C0 of each eccentric portion 72 is parallel to the rotation axis Ax1, and is disposed at a position radially offset from the rotation axis Ax 1. Here, the distance Δl0 (see fig. 5 and 6) between the axial center Ax2 and the center C0 becomes an eccentric amount with respect to the axial center 71. The eccentric portion 72 has a flange shape protruding from the outer peripheral surface of the shaft portion 71 over the entire circumference at the center portion in the longitudinal direction (axial direction) of the shaft portion 71. According to the above configuration, the eccentric portion 72 is eccentrically moved by the rotation (autorotation) of the shaft portion 71 about the axial center Ax2 with respect to the respective crankshafts 7A, 7B, and 7C.

In the present basic structure, the shaft portion 71 and the 2 eccentric portions 72 are integrally formed of 1 metal member, whereby seamless crankshafts 7A, 7B, 7C are realized. The crankshafts 7A, 7B, 7C having such a shape are combined with the eccentric body bearing 5 in the planetary gear 3. Therefore, in a state where the planetary gear 3 is combined with the eccentric body bearing 5 and the crankshafts 7A, 7B, 7C, the planetary gear 3 swings about the rotation axis Ax1 when the crankshafts 7A, 7B, 7C rotate.

The eccentric body bearing 5 is a member that has a plurality of rolling elements 51 (see fig. 4), absorbs a rotation component in rotation of the crankshafts 7A, 7B, 7C, and transmits only rotation of the crankshafts 7A, 7B, 7C other than the rotation component of the crankshafts 7A, 7B, 7C, that is, a wobble component (revolution component) of the crankshafts 7A, 7B, 7C to the planetary gear 3. The plurality of rolling elements 51 are disposed between the outer peripheral surface of the eccentric portion 72 of each crankshaft 7A, 7B, 7C and the inner peripheral surface of each opening 33 of the planetary gear 3. That is, the eccentric portion 72 of each of the crankshafts 7A, 7B, 7C functions as an inner ring of the eccentric body bearing 5, and the inner peripheral surface of each of the openings 33 of the planetary gear 3 functions as an outer ring of the eccentric body bearing 5.

In a state where the planetary gear 3 is combined with the eccentric body bearing 5 and the plurality of crankshafts 7A, 7B, 7C, when each of the crankshafts 7A, 7B, 7C rotates, the eccentric body bearing 5 rotates (eccentrically moves) about the shaft center Ax 2. At this time, the rotation components of the crankshafts 7A, 7B, 7C are absorbed by the eccentric body bearings 5. Therefore, only the rotation of the crankshafts 7A, 7B, 7C, that is, the wobble component (revolution component) of the crankshafts 7A, 7B, 7C, in addition to the rotation component of the crankshafts 7A, 7B, 7C, is transmitted to the planetary gear 3 via the eccentric body bearing 5. Thus, in a state where the planetary gear 3 is combined with the eccentric body bearing 5 and the crankshafts 7A, 7B, 7C, the planetary gear 3 swings around the rotation axis Ax1 when the crankshafts 7A, 7B, 7C rotate.

In the gear device 1 having the above-described configuration, the rotational force as an input is applied to the input shaft 500, and the input shaft 500 rotates around the rotational axis Ax1, whereby the planetary gear 3 swings (revolves) around the rotational axis Ax 1. At this time, the planetary gear 3 swings in a state of being inscribed inside the internal gear 2 in the internal gear 2 and a part of the external teeth 31 being meshed with a part of the internal teeth 21, so that the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2. Thus, relative rotation is generated between the two gears (the internal gear 2 and the planetary gear 3) according to the difference in the number of teeth between the planetary gear 3 and the internal gear 2. Further, the rotation (rotation component) of the planetary gear 3, in addition to the swing component (revolution component) of the planetary gear 3, is transmitted to the pair of brackets 18, 19 by the plurality of crankshafts 7A, 7B, 7C. As a result, a rotational output is obtained from the pair of brackets 18, 19, which is decelerated at a relatively high reduction ratio in accordance with the difference in the number of teeth between the two gears.

However, as described above, in the gear device 1 of the present basic structure, the difference in the number of teeth between the internal gear 2 and the planetary gear 3 defines the reduction ratio of the output rotation to the input rotation in the gear device 1. That is, when the number of teeth of the internal gear 2 is "V1" and the number of teeth of the planetary gear 3 is "V2", the reduction ratio R1 is represented by the following formula 1.

R1=v2/(V1-V2) (formula 1)

In short, the smaller the tooth number difference (V1-V2) between the internal gear 2 and the planetary gear 3, the larger the reduction ratio R1. For example, the number of teeth V1 of the internal gear 2 is "72", the number of teeth V2 of the planetary gear 3 is "70", and the number of teeth difference (V1-V2) is "2", so that the reduction ratio R1 is "35" according to the above formula 1. In this case, when each of the crankshafts 7A, 7B, 7C rotates clockwise (360 degrees) about the axial center Ax2 (see fig. 5 and 6) of the axial center portion 71 as viewed from the input side of the rotation shaft Ax1, the pair of brackets 18, 19 rotates counterclockwise (that is, about 10.3 degrees) by the amount of the tooth number difference "2" about the rotation shaft Ax 1.

According to the gear device 1 of the present basic structure, such a high reduction ratio R1 can be achieved by the combination of the internal gear 2 and the planetary gears 3. Further, between the input gear 501 and the plurality of crank gears 502A, 502B, 502C, an appropriate reduction ratio can be realized according to the number of teeth of the input gear 501 and the crank gears 502A, 502B, 502C. As a result, a high reduction ratio can be achieved as the entire gear device 1.

The gear device 1 may include at least the internal gear 2, the planetary gear 3, the crankshafts 7A, 7B, 7C, and a pair of carriers 18, 19, and may include a spacer 11, for example, as shown in fig. 4. The spacer 11 is disposed between the pair of planetary gears 3 (the first planetary gear 301 and the second planetary gear 302) in a direction (axial direction) parallel to the rotation axis Ax 1.

Embodiment one

As shown in fig. 7 and 8, the ring gear planetary gear device 1A (hereinafter, also simply referred to as "gear device 1A") of the present embodiment mainly has a structure around the bearing member 6 and a structure around the crankshafts 7A, 7B, 7C, which are different from the gear device 1 of the basic structure. Hereinafter, the same reference numerals are given to the same structures as those of the basic structures, and the description thereof will be omitted as appropriate. Fig. 7 is a schematic cross-sectional view of the gear device 1A. Fig. 8 is a schematic enlarged view of the region Z1 in fig. 7.

As shown in fig. 7, the gear device 1A of the embodiment further includes a plurality of oil seals 121, 122, and the like. The oil seal 121 blocks a gap between the housing 10 and the outer peripheral surface of the output side bracket 19. The oil seal 122 blocks a center hole 193 formed in the center portion of the output side bracket 19. The lubricant holding space 17 is constituted by a space enclosed by the plurality of oil seals 121, 122 and the like. The lubricant retaining space 17 contains a space between the inner ring 61 and the outer ring 62 of the bearing member 6. Further, the plurality of pins 23, the planetary gear 3, the pair of rolling bearings 41 and 42, the eccentric body bearing 5, and the like are accommodated in the lubricant holding space 17.

A lubricant is enclosed in the lubricant holding space 17. The lubricant is liquid and can flow in the lubricant holding space 17. Therefore, at the time of use of the gear device 1, for example, a lubricant enters the meshing portion of the internal teeth 21 composed of the plurality of external pins 23 and the external teeth 31 of the planetary gear 3. As used herein, "liquid" means a substance containing a liquid or gel state. The term "gel state" as used herein refers to a state having intermediate properties between a liquid and a solid, and containing a colloid (colloid) composed of two phases, i.e., a liquid phase and a solid phase. For example, an emulsion (emulsion) in which a dispersing agent is a liquid phase and a dispersoid is a liquid phase, and a suspension (suspension) in which a dispersoid is a solid phase, or the like, is included in a state called gel (gel) or sol (sol). The state in which the dispersant is in a solid phase and the dispersoid is in a liquid phase is also included in "gel-like state". In the present basic structure, the lubricant is, for example, liquid lubricating oil (oil liquid).

The gear device 1A of the present embodiment further includes a pair of covers 13, 14 attached to both sides of the brackets 18, 19 in the axial direction. When the pair of covers 13 and 14 are distinguished from each other, the cover 13 positioned on the input side (right side in fig. 7) of the rotation shaft Ax1 is referred to as "input side cover 13", and the cover 14 positioned on the output side (left side in fig. 7) of the rotation shaft Ax1 is referred to as "output side cover 14". In the present embodiment, the pair of covers 13 and 14 are made of a metal such as stainless steel, cast iron, carbon steel for machine construction, or chrome molybdenum steel, or a metal subjected to heat treatment.

The input-side cover 13 is formed in a disk shape centering on the rotation axis Ax 1. Here, at least the outer peripheral surface of the input-side cover 13 is a perfect circle centered on the rotation axis Ax1 in a plan view (viewed from one of the axial directions). The outer diameter of the input-side cover 13 is smaller than the outer diameter of the input-side bracket 18 by one turn. The input-side cover 13 is mounted with respect to the input-side carrier 18 from the outside, that is, from the side opposite to the planetary gears 3 when viewed from the input-side carrier 18 (right side in fig. 7).

The output-side cover 14 is formed in a disk shape centering on the rotation axis Ax 1. Here, at least the outer peripheral surface of the output-side cover 14 is a perfect circle centered on the rotation axis Ax1 in a plan view (viewed from one of the axial directions). The outer diameter of the output-side cover 14 is smaller than the outer diameter of the output-side bracket 19 by one turn. The output-side cover 14 is mounted with respect to the output-side carrier 19 from the outside, that is, from the opposite side (left side in fig. 7) of the planetary gear 3 as viewed from the output-side carrier 19.

Here, the pair of covers 13, 14 are detachably attached to the pair of brackets 18, 19. That is, the input-side cover 13 is detachably attached to the input-side bracket 18, and the output-side cover 14 is detachably attached to the output-side bracket 19. In the present embodiment, as an example, the covers 13 and 14 are attached to the brackets 18 and 19 by a plurality of fixing bolts 142 (see fig. 7). Therefore, by removing the plurality of fixing bolts 142, the covers 13 and 14 can be removed from the brackets 18 and 19.

Here, a plurality of through holes 141 are provided in the output side cover 14 of the pair of covers 13 and 14 so as to correspond to a plurality of mounting holes 194 (see fig. 7) provided in the output side bracket 19. That is, a plurality of mounting holes 194 (female screws) for fixing the target member are provided in the output side bracket 19. Accordingly, a plurality of through holes 141 are formed at positions corresponding to the plurality of mounting holes 194 in the output side cover 14 mounted on the outer side of the output side bracket 19.

On the other hand, the shaft holes 131 (see fig. 7) that pass through the crankshafts 7A, 7B, and 7C are provided only in the input-side cover 13 of the pair of covers 13 and 14. That is, the input-side cover 13 is provided with shaft holes 131 corresponding to the plurality of crankshafts 7A, 7B, 7C. An axial center portion 71 of each of the crankshafts 7A, 7B, 7C is inserted into each of the shaft holes 131. Here, in order to avoid the contact between the shaft portion 71 and the inner peripheral surface of the shaft hole 131, the inner diameter of each shaft hole 131 is set to be one turn larger than the outer diameter of the shaft portion 71.

Here, the gear device 1A of the present embodiment includes a restricting structure 70 that restricts movement of the crankshafts 7A, 7B, 7C in the axial direction. That is, in the gear device 1A of the present embodiment, the restriction structure 70 restricts the axial movement of the crankshafts 7A, 7B, 7C. The term "axial direction" as used in the present disclosure means a direction along the rotation axis Ax1, that is, along the axial center Ax2 of the crankshafts 7A, 7B, 7C, in particular, a direction (thrust direction) parallel to the axial center Ax2 of the crankshafts 7A, 7B, 7C. In addition, the term "movement restriction" as used in the present disclosure means that some restriction is applied to movement, and includes not only the movement being completely prohibited, but also the movement range being restricted, the movement being made difficult to move, and the like. That is, in the present embodiment, the movement of the crankshafts 7A, 7B, 7C is regulated in the axial direction along the axial center Ax2 of the crankshafts 7A, 7B, 7C by providing the regulating structure 70.

In the present embodiment, the restricting structure 70 prohibits the movement of the crankshafts 7A, 7B, 7C on both sides of one side (input side of the rotation shaft Ax 1) and the other side (output side of the rotation shaft Ax 1) in the axial direction, as an example. That is, in the example of fig. 7, the restricting structure 70 prohibits any one of the movement of the crankshafts 7A, 7B, 7C to the right in the drawing and the movement to the left in the drawing with respect to the pair of brackets 18, 19. Thereby, the positions of the crankshafts 7A, 7B, 7C in the axial direction (with respect to the pair of brackets 18, 19) are positioned at predetermined positions.

In the present embodiment, the restricting structure 70 includes a pair of covers 13, 14 attached to both sides of the pair of brackets 18, 19 in the axial direction. In short, the gear device 1A restricts movement of the crankshafts 7A, 7B, and 7C to one side and the other side in the axial direction using the input side cover 13 attached to the input side bracket 18 and the output side cover 14 attached to the output side bracket 19.

Specifically, the input-side cover 13 receives a force acting from the crankshafts 7A, 7B, 7C toward one side in the axial direction (rightward in fig. 7), and restricts movement of the crankshafts 7A, 7B, 7C toward one side in the axial direction. On the other hand, the output-side cover 14 receives a force acting from the crankshafts 7A, 7B, 7C toward the other side in the axial direction, and restricts movement of the crankshafts 7A, 7B, 7C toward the other side in the axial direction.

More specifically, the stepped portions of the crankshafts 7A, 7B, 7C on the input side (right side in fig. 8) of the rotation shaft Ax1 are brought into contact with the periphery of the shaft hole 131 on the surface of the input side cover 13 on the output side (left side in fig. 7) of the rotation shaft Ax1, whereby the crankshafts 7A, 7B, 7C are restrained from moving to one side (right side in fig. 7) in the axial direction. In addition, the end surfaces of the crankshafts 7A, 7B, 7C facing the output side (left side in fig. 7) of the rotation shaft Ax1 are brought into contact with the surface of the output side cover 14 facing the input side (right side in fig. 7) of the rotation shaft Ax1, whereby the movement of the crankshafts 7A, 7B, 7C to the other side (left side in fig. 7) in the axial direction is restricted.

However, as shown in fig. 7 and 8, the gear device 1A of the present embodiment further includes an elastic portion 8 that imparts a pre-compression force (forces F1, F2) between the inner race 61 and the outer race 62 of the bearing member 6. The elastic portion 8 applies forces F1 and F2 in a direction of compressing a gap Sp1 (see fig. 8) between the inner ring 61 and the outer ring 62 constituting the bearing member 6 in opposition to each other in the axial direction of the rotation axis Ax1, thereby applying a pre-compression force to the inner ring 61 and the outer ring 62. In fig. 8, the rolling elements 63 are shown by broken lines (two-dot chain lines).

The term "pre-stress" as used in the present disclosure means a state where internal stress is always applied by applying a pre-stress, and is a so-called preload (preload). That is, in the gear device 1A of the present embodiment, the pre-pressing force acts from the elastic portion 8 between the inner race 61 and the outer race 62 constituting the bearing member 6 in a state where the input shaft 500 is not driven, that is, in a state where the gear device 1A is not driven. In short, in the present embodiment, even when the gear device 1A is not driven, the inner ring 61 and the outer ring 62 are pressed against the rolling elements 63 interposed between the inner ring 61 and the outer ring 62 in the axial direction by the pre-pressure applied between the inner ring 61 and the outer ring 62, needless to say, when the gear device 1A is driven.

In summary, the gear device 1A of the present embodiment includes: an internal gear 2 having internal teeth 21; a planetary gear 3 having external teeth 31 partially meshed with the internal teeth 21; and a bearing member 6 having an inner race 61 and an outer race 62. In the gear device 1A, the planetary gear 3 is rotated relative to the internal gear 2 by swinging the planetary gear 3, and the outer ring 62 is rotated relative to the inner ring 61 about the rotation axis Ax 1. Here, a gap Sp1 is provided between the inner ring 61 and the outer ring 62 in the axial direction along the rotation axis Ax1, and a pre-compression force (forces F1, F2) is applied between the inner ring 61 and the outer ring 62 by the elastic portion 8 so as to fill the gap Sp 1.

According to the above configuration, the inner ring 61 and the outer ring 62 are always pressed against the rolling elements 63 by the pre-pressing force in the axial direction along the rotation axis Ax1, and a state in which the rolling elements 63 are separated from the inner ring 61 or the outer ring 62 is hardly generated. Therefore, if the drive gear device 1A is driven, the outer ring 62 rotates relative to the inner ring 61 about the rotation axis Ax1 in a state where the inner ring 61 and the outer ring 62 are pressed against the rolling elements 63 in the axial direction along the rotation axis Ax 1. In general, during operation of the gear device, at least one of the sliding members such as the inner ring 61, the outer ring 62, and the rolling elements 63 may wear, and a precompression may fall off due to an insufficient precompression with respect to the rated value, and in the gear device 1A of the present embodiment, such precompression falling off is easily avoided. As a result, the reduction in torque rigidity of the gear device 1A due to the pre-pressure drop can be suppressed, and the gear device 1A with less reliability degradation can be realized. In particular, as described later, when the gear device 1A is used in the joint device 200 for a robot (see fig. 10), the drop in torque rigidity directly relates to the sway (positional displacement) of the tip portion of the arm or the like, and the drop in torque rigidity is suppressed, thereby improving the control accuracy of the robot.

More specifically, in a general gear device, the elastic portion 8 is not provided as in the gear device 1X of the comparative example shown in fig. 9. In the gear device 1X, when the gear device 1A is assembled, the relative relationship between the distance between the inner ring 61 and the outer ring 62 in the axial direction and the diameter of the rolling elements 63 is adjusted, whereby the pre-compression force due to the predetermined position pre-compression system is applied between the inner ring 61 and the outer ring 62. That is, in the gear device 1X of the comparative example, the distance between the inner ring 61 and the outer ring 62 in the axial direction is set to be slightly smaller than the diameter of the rolling elements 63, so that the inner ring 61 and the outer ring 62 are pressed against the rolling elements 63. In such a predetermined position pre-compression, at least one of sliding members such as the inner ring 61, the outer ring 62, and the rolling elements 63 is worn out during the operation of the gear device 1X, and the pre-compression between the inner ring 61 and the outer ring 62 becomes small, so that the pre-compression may be released. The bearing member 6 is a member that receives a moment load in the gear device 1X, and if a pre-pressure drop occurs in the bearing member 6, the moment rigidity as the gear device 1X decreases. Particularly, in the long-term use of the gear device 1X, any pre-pressure may be generated to fall off, and the reliability of the gear device 1X may be lowered.

Further, in the gear device 1X using the predetermined position pre-compression force, in order to achieve the desired pre-compression force, dimensional accuracy and assembly accuracy of each component are required at the time of assembly of the gear device 1X so that the relationship between the distance between the inner ring 61 and the outer ring 62 in the axial direction and the diameter of the rolling elements 63 becomes a desired relationship. For example, in the case where there is a small dimensional deviation among the plurality of rolling elements 63, it may be necessary to perform the preliminary pressure adjustment by replacing at least a part of the plurality of rolling elements 63 or the like. As a result, the number of assembly steps of the gear device 1X may increase.

In contrast, in the gear device 1A of the present embodiment, the following constant pressure pre-pressing method is adopted: a gap Sp1 is set between the inner ring 61 and the outer ring 62 in the axial direction, and a precompression (forces F1, F2) is applied between the inner ring 61 and the outer ring 62 by the elastic portion 8 so as to fill the gap Sp 1. The term "to fill the gap Sp 1" as used in the present disclosure is synonymous with "a direction in which the gap Sp1 is narrowed". That is, in the gear device 1A, even if the rolling elements 63 are interposed between the inner ring 61 and the outer ring 62 in a state where the elastic portion 8 is not present, a gap Sp1 is generated between at least one of the inner ring 61 and the outer ring 62 and the rolling elements 63, and a "play" in which the rolling elements 63 move in the axial direction is generated. When the elastic portion 8 is added to the gear device 1A in this state, a pre-pressing force (forces F1, F2) acts on the bearing member 6 from the elastic portion 8 in a direction to narrow the gap Sp1, that is, in a direction to bring the inner ring 61 and the outer ring 62 relatively closer to each other in the axial direction. Further, by applying a precompression equal to or higher than a predetermined value, the movement of the rolling elements 63 in the axial direction is restricted, and the looseness of the rolling elements 63 is also suppressed.

In the gear device 1A employing the constant-pressure precompression method as described above, precompression is applied so that the gap Sp1 existing in itself is filled with the elastic force generated by the elastic portion 8. Therefore, even if at least any one of the sliding members such as the inner ring 61, the outer ring 62, and the rolling elements 63 is worn out during the operation of the gear device 1A, the pre-compression force between the inner ring 61 and the outer ring 62 can be maintained, and the pre-compression force is less likely to fall off. Therefore, the gear device 1A according to the present embodiment has an advantage that the pre-pressing drop due to the wear of the members is less likely to occur, and the reliability is less likely to be lowered. Further, when the gear device 1A is assembled, since dimensional accuracy and assembly accuracy of each component such as the gear device 1X of the comparative example are not required, it is difficult to take time and effort for adjusting the pre-pressure, and therefore, it is also expected that the man-hour for assembling the gear device 1A will be reduced.

Specifically, as shown in fig. 8, in the embodiment, the elastic portion 8 includes a component different from the bearing member 6. That is, the bearing member 6 includes the inner ring 61, the outer ring 62, and the plurality of rolling elements 63, and the gear device 1A of the present embodiment includes components as the elastic portion 8 in addition to the inner ring 61, the outer ring 62, and the plurality of rolling elements 63. Further, in the present embodiment, the inner ring 61 is integrated with the input side bracket 18, and the elastic portion 8 is configured as another member that can be separated from the input side bracket 18. According to this structure, a desired pre-compression force can be applied between the inner ring 61 and the outer ring 62 by the elastic portion 8 without performing special processing on the bearing member 6 itself.

Here, the elastic portion 8 composed of a component different from the bearing member 6 is exemplified by spring washers 81, 82 (lock washers). That is, the elastic portion 8 includes the spring washers 81, 82. In particular, in the present embodiment, as an example, as shown in fig. 7 and 8, the 2 kinds of spring washers 81, 82 function as the elastic portion 8.

A spring washer 81 is disposed between the outer race 62 of the first bearing member 601 and the gear body 22 of the internal gear 2. That is, the outer ring 62 of the first bearing member 601 is disposed so as to face the gear main body 22 of the internal gear 2 via the spring washer 81 in the axial direction. Therefore, the spring washer 81 applies a force F1 to the outer race 62, which presses the outer race 62 in the axial direction in a direction away from the gear body 22 (i.e., the axial outer side (right side in fig. 8), with reference to the gear body 22.

The other spring washer 82 is disposed between the input side bracket 18 integrated with the inner race 61 of the first bearing member 601 and the head of the bracket bolt 192. That is, the inner ring 61 (input side bracket 18) of the first bearing member 601 is disposed so as to face the head of the bracket bolt 192 fixed to the output side bracket 19 via the spring washer 82 in the axial direction. Here, a normal washer 83 (flat washer) is mounted on the bracket bolt 192 together with the spring washer 82, and the washer 83 is disposed between the bottom surface of the bolt hole 181 (see fig. 8) of the input side bracket 18 in which the head portion of the bracket bolt 192 is housed and the spring washer 82. Therefore, the spring washer 82 applies a force F2 to the inner ring 61 in the axial direction toward the direction approaching the output side bracket 19, that is, the axial inner side (left side in fig. 8) with respect to the output side bracket 19. In practice, since the input side bracket 18 is fixed to the output side bracket 19 by a plurality (3, for example) of bracket bolts 192, a plurality (3, for example) of spring washers 82 are provided for each bracket bolt 192.

Thus, one spring washer 81 causes an axially outward (right in fig. 8) force F1 to act on the outer race 62 of the bearing member 6, and the other spring washer 82 causes an axially inward (left in fig. 8) force F2 to act on the inner race 61 of the bearing member 6. As a result, the elastic portion 8 imparts a pre-compression force to the inner ring 61 and the outer ring 62 of the first bearing member 601 in the direction of filling the gap Sp1 in the axial direction.

In particular, according to the elastic portion 8 having the above-described structure, the pre-compression force is indirectly applied not only to the first bearing member 601 but also to the second bearing member 602. That is, the spring washer 81 applies an axially outward (left side in fig. 7) force to the outer race 62 of the second bearing member 602 via the gear main body 22. On the other hand, the output side bracket 19 integrated with the inner ring 61 of the second bearing member 602 is pulled inward in the axial direction (rightward in fig. 7) by the bracket bolt 192 by the head of the bracket bolt 192 receiving the rightward force of fig. 7 from the spring washer 82. That is, the spring washer 82 applies an axially inward (rightward in fig. 7) force to the inner race 61 of the second bearing member 602 via the bracket bolt 192.

Thus, in the present embodiment, the bearing member 6 includes the first bearing member 601 and the second bearing member 602 separated in the axial direction. The elastic portion 8 imparts a pre-compression force to both the first bearing member 601 and the second bearing member 602. According to the first bearing member 601 and the second bearing member 602 separated in the axial direction, the torque rigidity as the gear device 1A can be improved as compared with the case of only the single bearing member 6. Further, since the elastic portion 8 imparts the pre-compression force to both the first bearing member 601 and the second bearing member 602, the pre-compression force generated by the abrasion of the sliding component is easily prevented from falling off by either the first bearing member 601 or the second bearing member 602.

Further, in the present embodiment, the outer ring 62 is non-rotatably combined with the internal gear 2, and the elastic portion 8 is interposed between the outer ring 62 and the internal gear 2. That is, the spring washers 81 among the spring washers 81, 82 functioning as the elastic portion 8 are disposed between the outer ring 62 and the gear body 22 of the internal gear 2. Therefore, the elastic portion 8 (the spring washer 81) directly applies the force F1 to the outer ring 62 (of the first bearing member 601), thereby easily imparting a desired pre-compression force. Further, the pre-pressure drop due to plastic deformation or the like of each member is not easily generated.

However, the elastic portion 8 is not limited to the spring washers 81 and 82, as long as it has elasticity that imparts only a pre-compression force between the inner race 61 and the outer race 62 of at least one of the first bearing member 601 and the second bearing member 602. That is, the elastic portion 8 has a property (elasticity) of being deformed by an external force and returning to an original shape when the external force is released, and a pre-pressure is applied between the inner ring 61 and the outer ring 62 by the elastic force. The elastic portion 8 is preferably made of a material having a young's modulus of 220GPa or less.

As shown in fig. 10, the gear device 1A of the present embodiment forms a robot joint device 200 together with a first member 201 and a second member 202. In other words, the joint device 200 for a robot of the present embodiment includes the gear device 1A, the first member 201, and the second member 202. The first member 201 is fixed to the internal gear 2. The second member 202 is opposed to the first member 201 in association with the relative rotation of the planetary gear 3 to the internal gear 2. Fig. 10 is a schematic cross-sectional view of the joint device 200 for a robot. In addition, in fig. 10, the first member 201, the second member 202, and the driving source 101 are schematically shown.

The joint device 200 for a robot thus configured functions as a joint device by rotating the first member 201 and the second member 202 relative to each other about the rotation axis Ax 1. Here, the first member 201 and the second member 202 are rotated relatively by driving the input shaft 500 of the gear device 1A by the driving source 101. At this time, the rotation (input rotation) generated by the drive source 101 is decelerated at a relatively high reduction ratio in the gear device 1A, and the first member 201 or the second member 202 is driven at a relatively high torque. That is, the first member 201 and the second member 202 coupled by the gear device 1A can perform the bending and stretching operation about the rotation axis Ax 1.

The robot joint device 200 is used for a robot such as a horizontal multi-joint robot (articulated robot), for example. The robot joint device 200 is not limited to a horizontal multi-joint robot, and may be used for example, an industrial robot other than a horizontal multi-joint robot, a robot other than an industry, or the like. The gear device 1A of the present embodiment is not limited to the robot joint device 200, and may be used for a vehicle such as an unmanned vehicle (AGV: automated Guided Vehicle) as a wheel device such as an in-wheel motor.

< Modification >

The first embodiment is merely one of various embodiments of the present invention. As long as the object of the present invention can be achieved, various modifications can be made according to the design and the like. In the present invention, the drawings referred to are schematic, and the ratio of the size and thickness of each component in the drawings is not necessarily limited to reflect the actual dimensional ratio. A modification of the first embodiment will be described below. The modifications described below can be applied in any suitable combination.

The number of crankshafts 7A, 7B, and 7C is not limited to "3", and may be 2 or 4 or more. Further, if the number of crankshafts is only 1, an eccentric oscillating type ring gear device is realized in which the rotation axis Ax1 coincides with the axial center Ax2 of the crankshaft, instead of the split type ring gear device. In this case, the planetary gear 3 is oscillated by driving the crankshaft, and the pair of carriers 18 and 19 can be rotated relative to the gear body 22 about the rotation axis Ax 1.

In the first embodiment, the gear device 1A of the type in which the number of planetary gears 3 is 2 is exemplified, but the gear device 1A may include 3 or more planetary gears 3. For example, in the case where the gear device 1A includes three planetary gears 3, it is preferable that the three planetary gears 3 are arranged with a phase difference of 120 degrees around the rotation axis Ax 1. In addition, the gear device 1A may include only one planetary gear 3. Alternatively, in the case where the gear device 1A includes three planetary gears 3, two of the three planetary gears 3 may be identical in phase, and the remaining one planetary gear 3 may be disposed 180 degrees apart around the rotation axis Ax 1.

The bearing member 6 may be a cross roller bearing, a deep groove ball bearing, a four-point contact ball bearing, or the like.

The number of teeth of the input gear 501, the number of teeth of the crank gears 502A, 502B, 502C, the number of pins 23 (the number of teeth of the internal teeth 21), the number of teeth of the external teeth 31, and the like described in the first embodiment are merely examples, and may be appropriately changed.

The eccentric body bearing 5 is not limited to a roller ball bearing, and may be, for example, a deep groove ball bearing or an angular contact ball bearing.

The material of each component of the gear device 1A is not limited to metal, and may be, for example, resin such as process plastic.

The gear device 1A is not limited to a configuration in which the rotational force of the inner ring 61 (the input side bracket 18 and the output side bracket 19) is taken out as output, as long as the relative rotation between the inner ring 61 and the outer ring 62 of the bearing member 6 can be taken out as output. For example, the rotational force of the outer ring 62 (the case 10) that rotates relative to the inner ring 61 may be taken out as an output.

In the first embodiment, the output-side end surface of the rotation shaft Ax1 of the crankshafts 7A, 7B, 7C is in direct contact with the output-side cover 14, but the present invention is not limited to this configuration, and a plate-like member such as a spacer member may be disposed between the end surface and the output-side cover 14. In this case, when the output-side cover 14 is attached, the gap between the end surface and the output-side cover 14 can be adjusted in the axial direction by adjusting the thickness (and/or the number of pieces) of the plate-like member, and the "play" in the axial direction of the crankshafts 7A, 7B, 7C can be adjusted. Further, the plate-like member functions as a rail ring (rail disc) that reduces friction between the end surface and the output-side cover 14.

The lubricant is not limited to a liquid substance such as a lubricating oil (oil liquid), and may be a gel substance such as grease.

The elastic portion 8 is not limited to the structure having the 2 kinds of spring washers 81 and 82, and may have only one of the spring washers 81 and 82. Further, the elastic portion 8 may include an elastic member such as a coil spring, a leaf spring, rubber, or sponge, for example.

Embodiment II

As shown in fig. 11, the structure of an elastic portion 8 of a ring gear planetary gear device 1B (hereinafter, also simply referred to as "gear device 1B") of the present embodiment is different from that of the gear device 1A of the first embodiment. Hereinafter, the same reference numerals are given to the same configurations as those of the first embodiment, and the description thereof will be omitted as appropriate. Fig. 11 is a schematic view corresponding to fig. 8 (an enlarged view of a region Z1 in fig. 7), and shows the rolling elements 63 by a broken line (two-dot chain line).

In the gear device 1B of the present embodiment, the elastic portion 8 has thin portions 84, 85 instead of the spring washers 81, 82 (see fig. 8). In short, the elastic portion 8 has a film structure, and elastically deforms itself by the thin portions 84, 85 to provide a preload between the inner ring 61 and the outer ring 62 so as to fill the gap Sp1 between the inner ring 61 and the outer ring 62.

A thin portion 84 includes a rolling surface of the rolling element 63 in the outer ring 62 of the first bearing member 601, that is, a surface facing the inner ring 61, and is configured to have a thickness (thin wall) of a degree of elasticity. Specifically, a hollow is formed in the outer ring 62 along the rolling surface of the rolling element 63, and a portion between the hollow and the rolling element 63 functions as the thin portion 84. That is, the thin wall portion 84 formed in the outer ring 62 of the first bearing member 601 causes a force that presses (the rolling surface of the rolling element 63 in) the outer ring 62 in the axial direction toward the direction away from the gear main body 22, that is, the axial outside (the right side in fig. 11) to act on the outer ring 62.

The other thin-walled portion 85 includes a rolling surface of the rolling element 63 in the inner ring 61 of the first bearing member 601, that is, a surface facing the outer ring 62, and is configured to have a thickness (thin wall) of a degree of elasticity. Specifically, a hollow is formed in the inner ring 61 along the rolling surface of the rolling element 63, and a portion between the hollow and the rolling element 63 functions as the thin-walled portion 85. That is, the thin wall portion 85 formed in the inner ring 61 of the first bearing member 601 causes a force pressing (the rolling surface of the rolling element 63 in) the inner ring 61 toward the direction approaching the output side bracket 19 in the axial direction, that is, toward the inner side in the axial direction (left side in fig. 11) to act on the inner ring 61.

As described above, in the gear device 1B of the present embodiment, the elastic portion 8 includes a part of the bearing member 6. That is, the thin wall portions 84, 85 as the elastic portions 8 are realized by a part of the inner ring 61 and the outer ring 62 of the bearing member 6. By realizing the elastic portion 8 by using the component of the bearing member 6 in this way, it is possible to suppress an increase in the component of the gear device 1B, and at the same time, it is possible to adopt a constant-pressure precompression system, and it is possible to suppress precompression from falling off.

However, the thin portions 84, 85 may be provided to at least one of the first bearing member 601 and the second bearing member 602, and may have elasticity that imparts only a pre-pressure between the inner ring 61 and the outer ring 62. The elastic portion 8 formed of a part of the bearing member 6 is not limited to the membrane structure, and may be, for example, a beam structure. Further, the elastic portion 8 is not limited to the structure having the thin portions 84, 85, and may have only one of the thin portions 84, 85.

In addition, the elastic portion 8 formed of a part of the bearing member 6 as in the present embodiment and the elastic portion 8 formed of a different member from the bearing member 6 as in the first embodiment may be used in combination.

The configuration of the second embodiment (including the modification) can be appropriately combined with the various configurations described in the first embodiment (including the modification).

(Summary)

As described above, the ring gear planetary gear device (1, 1A, 1B) of the first aspect includes the internal gear (2), the planetary gear (3), and the bearing member (6). The internal gear (2) has internal teeth (21). The planetary gear (3) has external teeth (31) that mesh with the internal teeth (21) locally. The bearing member (6) has an inner ring (61) and an outer ring (62). The ring gear device (1, 1A, 1B) swings the planetary gear (3), thereby relatively rotating the planetary gear (3) with respect to the internal gear (2), and relatively rotating the outer ring (62) with respect to the inner ring (61) about the rotation axis (Ax 1). A gap (Sp 1) is provided between the inner ring (61) and the outer ring (62) in the axial direction along the rotation axis (Ax 1), and a pre-compression force is applied between the inner ring (61) and the outer ring (62) by an elastic portion (8) so as to fill the gap (Sp 1).

According to this aspect, the inner ring (61) and the outer ring (62) are always pressed against the rolling elements (63) by the pre-pressing force in the axial direction along the rotation axis (Ax 1), and a state in which the rolling elements (63) are separated from the inner ring (61) or the outer ring (62) is hardly generated. As a result, the drop in torque rigidity of the ring gear planetary gear devices (1, 1A, 1B) caused by the drop in pre-pressure can be suppressed, and the ring gear planetary gear devices (1, 1A, 1B) that are less likely to drop in reliability can be realized.

In the ring gear planetary gear device (1, 1A, 1B) of the second aspect, the elastic portion (8) includes a part of the bearing member (6) in addition to the first aspect.

According to this aspect, by realizing the elastic portion (8) by the member of the bearing member (6), the increase of the member can be suppressed, and the pre-compression drop can be suppressed.

In the ring gear planetary gear device (1, 1A, 1B) of the third aspect, the elastic portion (8) includes a component different from the bearing member (6) in addition to the first or second aspect.

According to this aspect, a desired pre-compression force can be applied between the inner ring (61) and the outer ring (62) by the elastic portion (8) without performing special processing on the bearing member (6) itself.

In the ring gear planetary gear device (1, 1A, 1B) of the fourth aspect, the elastic portion (8) includes spring washers (81, 82) in addition to the third aspect.

According to this structure, a desired pre-compression force can be applied between the inner ring (61) and the outer ring (62) by the elastic portion (8) with a relatively simple structure.

In the ring gear planetary gear device (1, 1A, 1B) according to the fifth aspect, the bearing member (6) includes a first bearing member (601) and a second bearing member (602) separated in the axial direction in addition to any one of the first to fourth aspects. The elastic portion (8) imparts a pre-compression force to both the first bearing member (601) and the second bearing member (602).

According to this aspect, since the elastic portion (8) imparts a pre-compression force to both the first bearing member (601) and the second bearing member (602), the pre-compression force generated by the wear of the sliding component can be easily prevented from falling off by either the first bearing member (601) or the second bearing member (602).

In the ring gear device (1, 1A, 1B) of the sixth aspect, the outer ring (62) is combined with the internal gear (2) in a direction in which the outer ring cannot rotate in any of the first to fifth aspects. The elastic portion (8) is interposed between the outer ring (62) and the internal gear (2).

According to this aspect, the elastic portion (8) can directly apply a force to the outer ring (62), and a desired pre-compression force can be easily applied thereto.

The seventh aspect of the joint device (200) for a robot includes: an internal-gearing planetary gear device (1, 1A, 1B) according to any one of the first to sixth aspects; a first member (201) fixed to the internal gear (2); and a second member (202) that rotates relative to the first member (201) in conjunction with the relative rotation of the planetary gear (3) to the internal gear (2).

According to this aspect, the drop in torque rigidity of the ring gear planetary gear devices (1, 1A, 1B) due to the drop in pre-pressure can be suppressed, and the robot joint device (200) with less reliability degradation can be realized. In particular, in the joint device (200) for a robot, the drop in moment rigidity is directly related to the sway (positional deviation) of the tip portion of the arm or the like, and the drop in moment rigidity is suppressed, so that the control accuracy of the robot is improved.

The second to sixth configurations are not necessarily provided for the ring gear devices (1, 1A, 1B), and may be omitted as appropriate.

Description of the reference numerals

1. 1A, 1B internal meshing planetary gear device

2. Internal tooth gear

3. Planetary gear

8. Elastic part

21. Internal teeth

31. External teeth

61. Inner ring

62. Outer ring

81. 82 Spring washer

200. Joint device for robot

201. First component

202. Second component

601. First bearing component

602. Second bearing member

Ax1 rotation shaft

Sp1 gap.

Claims (7)

1. An internal meshing planetary gear device, comprising:

an internal gear having internal teeth;

A planetary gear having external teeth partially meshed with the internal teeth; and

A bearing member having an inner race and an outer race,

By swinging the planetary gear, the planetary gear is rotated relative to the internal gear, and the outer ring is rotated relative to the inner ring about a rotation axis,

A gap is provided between the inner ring and the outer ring in an axial direction along the rotary shaft, and a pre-compression force is applied between the inner ring and the outer ring by an elastic portion so as to fill the gap.

2. The ring gear arrangement of claim 1, wherein,

The elastic portion includes a portion of the bearing member.

3. The ring gear arrangement according to claim 1 or 2, wherein,

The elastic portion includes a component different from the bearing member.

4. The ring gear arrangement as claimed in claim 3, wherein,

The resilient portion includes a spring washer.

5. The ring gear arrangement according to claim 1 or 2, wherein,

The bearing member includes a first bearing member and a second bearing member separated in the axial direction,

The elastic portion imparts a pre-compression force to both the first bearing member and the second bearing member.

6. The ring gear arrangement according to claim 1 or 2, wherein,

The outer race is non-rotatably combined with the internal gear,

The elastic portion is interposed between the outer race and the internal gear.

7. A joint device for a robot, comprising:

The ring gear arrangement of claims 1-2;

a first member fixed to the internal gear; and

A second member that rotates relative to the first member in association with the relative rotation of the planetary gear to the internal gear.