Internal meshing planetary gear device and robot joint device

Abstract

An internal meshing planetary gear device (1), comprising: an internal gear (2), a planetary gear (3), crankshafts (7A, 7B, 7C), planet carriers (18, 19), and a limiting member (82). By means of swinging the planetary gear (3), the planetary gear (3) rotates relative to the internal gear (2); the inner gear (2) is provided with an annular gear body (22) and a plurality of outer pins (23) which can be kept in a self-rotating state in a plurality of inner circumferential grooves (223) formed in an inner peripheral face (221) of the gear body (22) and constitute inner teeth (21); the planetary gear (3) is provided with outer teeth (31) partially meshed with the inner teeth (21); the crankshafts (7A, 7B, 7C) rotate around an axis (Ax2) so as to swing the planetary gear (3); the planet carrier (19) is provided with a recess (81); the crankshaft (7A) is rotatably supported within the recess (81) by means of a crankshaft bearing (42); the limiting member (82) is arranged within the recess (81) of the planet carrier (19); the limiting member (82) is provided with a bottom (822) and a peripheral wall (823); the bottom (822) is arranged axially opposite to one end face of the crankshaft (7A); the peripheral wall (823) protrudes from the outer peripheral portion of the bottom (822) to the side axially opposite to the bottom face (811) of the recess; by means of the contact between the crankshafts (7A, 7B, 7C) and the bottom (822), the movement of the crankshafts (7A, 7B, 7C) towards the bottom face (811) side is restricted; the peripheral wall (823) constitutes an outer ring (401) of the crankshaft bearing (42). Such structure provides an internal meshing planetary gear device in which the shape of each member is easy to simplify. In addition, the present disclosure also relates to a robot joint device.

Description

Internal meshing planetary gear mechanism and joint mechanism for robot Technical Field

[0001] This disclosure generally relates to an internal meshing planetary gear device and a joint device for robots, and more specifically, to an internal meshing planetary gear device and a joint device for robots in which a planetary gear with external teeth is disposed inside an internal gear with internal teeth. Background Technology

[0002] As a related technology, a type of speed reducer, namely an eccentric oscillating type internal meshing planetary gear device, is known (for example, see Patent Document 1). The related technology internal meshing planetary gear device includes: a crankshaft; planetary gears (external gears) mounted on the crankshaft; internal gears (housing) having internal teeth that mesh with the planetary gears; and a planet carrier configured to rotate relative to the internal gears.

[0003] In this type of internal meshing planetary gear device, when the crankshaft is rotated by a drive source, the planetary gears are pressed and oscillated (rotated) by an eccentric body mounted on the crankshaft, and the planet carrier rotates relative to the internal gear according to the oscillation of the planetary gears. Thus, the decelerated rotation is output from the planet carrier or the internal gear to the other device.

[0004] In the aforementioned related art, the planetary carrier has a recess into which one end of the crankshaft is inserted. A restraining member is disposed on the bottom surface of the recess, which restrains the movement of the crankshaft along its rotational axis toward the bottom surface of the recess. A crankshaft bearing supporting the crankshaft is disposed on the inner circumferential surface of the recess, and the restraining member restricts the movement of the crankshaft bearing toward the bottom surface in the direction of its rotational axis. Here, the inner circumferential surface of the recess has a support surface supporting the crankshaft bearing and a clearance portion disposed between the support surface and the bottom surface in the direction of rotational axis, the diameter of which is larger than that of the support surface.

[0005] [Existing Technical Documents]

[0006] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2021-011936 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] In the structure of the related technology, it is necessary to form a relief portion with a diameter larger than the support surface (which supports the crankshaft bearing) on ​​the inner circumferential surface of the recess, which causes the shape of the planetary carrier to become complicated.

[0010] The purpose of this disclosure is to provide a simplified internal meshing planetary gear device and a joint device for robots that allows for easy realization of the shapes of each component.

[0011] [Technical means to solve the problem]

[0012] One aspect of the disclosed internal meshing planetary gear assembly includes: an internal gear, planetary gears, a crankshaft, a planet carrier, and a limiting member. The planetary gears are oscillated, causing them to rotate relative to the internal gear. The internal gear has an annular gear body and a plurality of external pins that are rotatably held in a plurality of inner circumferential grooves formed on the inner circumferential surface of the gear body and constitute internal teeth. The planetary gears have external teeth that partially mesh with the internal teeth. The crankshaft oscillates by rotating about its axis. The planet carrier has a recess, and the crankshaft is rotatably supported in the recess by a crankshaft bearing. The limiting member is disposed within the recess of the planet carrier. The limiting member has a bottom and a peripheral wall, the bottom being axially opposite one end face of the crankshaft, and the peripheral wall protruding from the outer periphery of the bottom toward the axially opposite bottom face of the recess. Movement of the crankshaft toward the bottom face is limited by contacting the bottom. The peripheral wall forms the outer ring of the crankshaft bearing.

[0013] One aspect of the robot joint device disclosed herein includes: the internal meshing planetary gear assembly; a first member fixed to the gear body; and a second member that rotates relative to the first member as the planetary gear rotates relative to the internal gear.

[0014] [The effects of the invention]

[0015] According to this disclosure, it has the following advantages: it can provide a simplified internal meshing planetary gear device and a joint device for robots that can easily realize the shapes of each component. Attached Figure Description

[0016] Figure 1 is a perspective view showing the schematic structure of the actuator of the internal meshing planetary gear device, including the basic structure.

[0017] Figure 2 is a schematic exploded perspective view of the internal meshing planetary gear device of the basic structure as seen from the input side of the rotating shaft.

[0018] Figure 3 is a schematic exploded perspective view of the basic structure of the internal meshing planetary gear device when viewed from the output side of the rotating shaft.

[0019] Figure 4 is a schematic cross-sectional view of the basic structure of the internal meshing planetary gear device.

[0020] Figure 5 is a cross-sectional view along line A1-A1 of Figure 4 showing the basic structure of the internal meshing planetary gear assembly.

[0021] Figure 6 is a cross-sectional view along line B1-B1 of Figure 4 showing the basic structure of the internal meshing planetary gear assembly.

[0022] Figure 7 is a schematic diagram of a robot articulation device using an internal meshing planetary gear mechanism with a basic structure.

[0023] Figure 8 is a schematic cross-sectional view of the main parts of the internal meshing planetary gear device, showing the basic structure.

[0024] Figure 9 is a schematic cross-sectional view showing the main parts of the internal meshing planetary gear device of Embodiment 1.

[0025] Figure 10 is a schematic cross-sectional view showing the main parts of the internal meshing planetary gear device of Embodiment 2. Embodiments of the present invention

[0026] (Basic Structure)

[0027] (1) Summary

[0028] Hereinafter, the general outline of the internal meshing planetary gear device 1 of this basic structure will be described with reference to Figures 1 to 4. The figures referred to in this disclosure are all schematic diagrams, and the size and thickness ratios of the various structural components in the figures are not necessarily limited to reflecting the actual size ratios. For example, the tooth shape, size, and number of teeth of the internal tooth 21 and the external tooth 31 in Figures 1 to 4 are only schematic representations for illustration and are not limited to the main idea of ​​the shape shown in the figures.

[0029] The internal meshing planetary gear assembly 1 (hereinafter also simply referred to as "gear assembly 1") of this basic structure is a gear assembly including an internal gear 2 and a planetary gear 3. In the gear assembly 1, the planetary gear 3 is arranged inside the annular internal gear 2, and by oscillating the planetary gear 3, the planetary gear 3 rotates relative to the internal gear 2. In addition, the internal meshing planetary gear assembly 1 also includes a bearing assembly 6 having an outer ring 62 and an inner ring 61. The inner ring 61 is arranged inside the outer ring 62 and is supported so as to be able to rotate relative to the outer ring 62. In particular, the gear assembly 1 of this basic structure is a type of eccentric oscillating internal meshing planetary gear assembly known as a distribution type.

[0030] As shown in Figures 1 to 4, the gear device 1 of this basic structure includes multiple (three in the basic structure) crankshafts (eccentric shafts) 7A, 7B, and 7C disposed at positions offset from the axis (rotation shaft Ax1) of the internal gear 2. Furthermore, the gear device 1 includes an input shaft 500 disposed on the axis (rotation shaft Ax1) of the internal gear 2, centered on the rotation shaft Ax1, and an input gear 501 integrally formed with the input shaft 500. Crankshaft gears 502A, 502B, and 502C are splinedly connected to the multiple crankshafts 7A, 7B, and 7C, respectively. These multiple (three in the basic structure) crankshaft gears 502A, 502B, and 502C are arranged to mesh with the input gear 501. Therefore, when the input shaft 500 is driven, the gear device 1 synchronously drives the crankshafts 7A, 7B, and 7C using the input gear 501, thereby causing the planetary gear 3 to oscillate.

[0031] The internal gear 2 has internal teeth 21 and is fixed to the outer ring 62. Specifically, in this basic structure, the internal gear 2 has an annular gear body 22 and multiple outer pins 23. The multiple outer pins 23 are held in a rotatable state on the inner circumferential surface 221 of the gear body 22 and constitute the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. That is, it presents a state where, inside the internal gear 2, the planetary gear 3 is internally connected to the internal gear 2, and a portion of the external teeth 31 meshes with a portion of the internal teeth 21. In this state, when the multiple crankshafts 7A, 7B, and 7C are driven, the planetary gear 3 oscillates, and the meshing position of the internal teeth 21 and external teeth 31 moves in the circumferential direction of the internal gear 2, generating a relative rotation between the two gears (internal gear 2 and planetary gear 3) corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2. Here, if the internal gear 2 is fixed, the planetary gear 3 rotates (self-rotates) as the two gears rotate relative to each other. As a result, based on the difference in the number of teeth between the two gears, a rotational output with a relatively high reduction ratio is obtained from planetary gear 3.

[0032] This gear device 1 is used in such a way that the rotation equivalent to the rotation component of the planetary gear 3 is taken out as the rotation of a pair of planetary carriers 18, 19, whose inner rings 61 of the bearing device 6 are fixed relative to each other by means of embedding or the like. Thus, the gear device 1 functions as a gear device with a relatively high reduction ratio, with the input shaft 500 as the input side and the pair of planetary carriers 18, 19 as the output side. Therefore, in this basic structure of the gear device 1, in order to transmit the rotation equivalent to the rotation component of the planetary gear 3 to the pair of planetary carriers 18, 19, a pair of planetary carriers 18, 19 are used to support multiple crankshafts 7A, 7B, 7C. The pair of planetary carriers 18, 19 are arranged on both sides of the axial direction (along the direction of the rotation axis Ax1) of the planetary gear 3, supporting each crankshaft 7A, 7B, 7C so that it can rotate.

[0033] Here, multiple crankshafts 7A, 7B, and 7C, each inserted into a plurality of openings 33 formed in the planetary gear 3, rotate relative to the internal gear 2 as the planetary gear 3 rotates. Furthermore, each crankshaft 7A, 7B, and 7C has a central shaft portion 71 and an eccentric portion 72 eccentrically positioned relative to the central shaft portion 71. A pair of planetary carriers 18 and 19 support the central shaft portion 71 of each crankshaft 7A, 7B, and 7C so that it can rotate, and the eccentric portions 72 of each crankshaft 7A, 7B, and 7C are inserted into the openings 33 of the planetary gear 3. When each crankshaft 7A, 7B, and 7C rotates about its respective central shaft portion 71, each eccentric portion 72 rotates eccentrically relative to its respective central shaft portion 71 (eccentric motion). Accompanying this, the planetary gear 3 oscillates. Through the oscillation of the planetary gear 3, the planetary gear 3 partially meshes with the internal gear 2 and rotates relative to the internal gear 2. As a result, planetary gear 3 rotates on its own central axis while revolving within internal gear 2, rotating about axis Ax1. As planetary gear 3 rotates, crankshafts 7A, 7B, and 7C revolve about axis Ax1. Planet carriers 18 and 19, which support the central shafts 71 of crankshafts 7A, 7B, and 7C, rotate in tandem with the revolution of crankshafts 7A, 7B, and 7C. Thus, the rotation (rotational component) of planetary gear 3, excluding its oscillating component (revolutionary component), is transmitted to a pair of planet carriers 18 and 19 via multiple crankshafts 7A, 7B, and 7C.

[0034] Furthermore, as shown in Figure 1, the gear assembly 1 of this basic structure, together with the drive source 101, constitutes the actuator 100. In other words, the actuator 100 of this basic structure includes the gear assembly 1 and the drive source 101. The drive source 101 generates a driving force for oscillating the planetary gear 3. Specifically, the drive source 101 oscillates the planetary gear 3 by rotating the input shaft 500 around the rotation axis Ax1.

[0035] (2) Definition

[0036] The term "ring-shaped" as used in this disclosure refers to a circle-like shape that forms a space (region) enclosed on the inside when viewed from above, and is not limited to a circular shape (ring-shaped) that is perfectly round when viewed from above. For example, it can also be an elliptical shape or a polygonal shape. Furthermore, for example, even a shape with a bottom, such as a cup shape, is included in "ring-shaped" as long as its peripheral walls are ring-shaped.

[0037] The term "revolution" as used in this disclosure refers to the rotation of an object about an axis other than the central axis passing through the object's center (center of gravity). When an object revolves, its center moves along a revolution path centered on the rotation axis. Therefore, for example, when an object rotates about an eccentric axis parallel to the central axis passing through its center (center of gravity), the object revolves around the eccentric axis as its rotation axis. As an example, planetary gear 3 revolves within internal gear 2 by oscillating and rotating about the rotation axis Ax1.

[0038] Furthermore, in this disclosure, one side of the rotating shaft Ax1 (the left side of FIG4) is sometimes referred to as the "output side," and the other side of the rotating shaft Ax1 (the right side of FIG4) is referred to as the "input side." In the example of FIG4, the input shaft 500 is rotated from the "input side" of the rotating shaft Ax1, and the rotation of a pair of planetary carriers 18 and 19 is taken out from the "output side" of the rotating shaft Ax1. Here, "input side" and "output side" are labels used for illustrative purposes only and do not limit the positional relationship of the input and output when viewed from the gear device 1.

[0039] In this disclosure, "rotation axis" refers to a virtual axis (line) that serves as the center of rotational motion of the rotating body. That is, rotation axis Ax1 is a virtual axis without a physical counterpart. Input axis 500 rotates around rotation axis Ax1.

[0040] In this disclosure, "internal teeth" and "external teeth" refer to a collection (group) of multiple "teeth," rather than a single "tooth." That is, the internal teeth 21 of the internal gear 2 comprise a collection of multiple teeth disposed on the inner circumferential surface 221 of the internal gear 2 (gear body 22). Similarly, the external teeth 31 of the planetary gear 3 comprise a collection of multiple teeth disposed on the outer circumferential surface of the planetary gear 3.

[0041] (3) Detailed structure of the gear mechanism

[0042] The detailed structure of the gear device 1 of this basic structure will be described below with reference to Figures 1 to 7.

[0043] Figure 1 is a perspective view showing the schematic structure of the actuator 100 including the gear assembly 1. In Figure 1, the drive source 101 is schematically shown. Figure 2 is a schematic exploded perspective view of the gear assembly 1 viewed from the input side of the rotating shaft Ax1. Figure 3 is a schematic exploded perspective view of the gear assembly 1 viewed from the output side of the rotating shaft Ax1. Figure 4 is a schematic cross-sectional view of the gear assembly 1. Figure 5 is a cross-sectional view along line A1-A1 of Figure 4. Figure 6 is a cross-sectional view along line B1-B1 of Figure 4. In Figures 5 and 6, for parts other than crankshafts 7A, 7B, and 7C, even in cross-sections, the shading lines are omitted.

[0044] (3.1) Overall structure

[0045] As shown in Figures 1 to 4, the gear assembly 1 of this basic structure includes: an internal gear 2, a planetary gear 3, a bearing assembly 6, multiple crankshafts 7A, 7B, and 7C, a pair of planetary carriers 18 and 19, and an input shaft 500. Additionally, in this basic structure, the gear assembly 1 also includes: an input gear 501, multiple crankshaft gears 502A, 502B, and 502C, a pair of crankshaft bearings 41 and 42, an eccentric bearing 5, and a housing 10. In this basic structure, the internal gear 2, planetary gear 3, multiple crankshafts 7A, 7B, and 7C, and the pair of planetary carriers 18 and 19, which are structural components of the gear assembly 1, are made of stainless steel, cast iron, carbon steel for mechanical structures, chromium-molybdenum steel, phosphor bronze, or aluminum bronze, or light metals such as aluminum or titanium. The metals mentioned here (including light metals) include metals that have undergone surface treatments such as nitriding.

[0046] Furthermore, in this basic structure, as an example of gear device 1, an internal planetary gear device using a subcycloid tooth profile is illustrated. That is, the gear device 1 of this basic structure includes an internal planetary gear 3 having a subcycloid curved tooth profile.

[0047] Furthermore, in this basic structure, as an example, the gear device 1 is used with the gear body 22 of the internal gear 2 and the outer ring 62 of the bearing device 6 fixed together on a fixed member such as the housing 10. As a result, with the relative rotation of the internal gear 2 and the planetary gear 3, the planetary gear 3 rotates relative to the fixed member (such as the housing 10).

[0048] Furthermore, in this basic structure, when the gear device 1 is used in the actuator 100, a rotational force is applied to the input shaft 500 as input, thereby extracting a rotational force as output from the pair of planetary carriers 18, 19 on the inner ring 61 to which the bearing device 6 is fixed. That is, the gear device 1 operates by taking the rotation of the input shaft 500 as input rotation and the rotation of the pair of planetary carriers 18, 19 on which the inner ring 61 is fixed as output rotation. Thus, in the gear device 1, an output rotation that is reduced at a relatively high reduction ratio relative to the input rotation can be obtained.

[0049] The drive source 101 is a power source such as a motor (electric motor). The power generated by the drive source 101 is transmitted to the input shaft 500 of the gear device 1. Specifically, the drive source 101 is connected to the input shaft 500, and the power generated by the drive source 101 is transmitted to the input shaft 500. Thus, the drive source 101 can rotate the input shaft 500.

[0050] Furthermore, in the gear device 1 of this basic structure, as shown in FIG4, the input-side rotational shaft Ax1 and the output-side rotational shaft Ax1 are located on the same straight line. In other words, the input-side rotational shaft Ax1 and the output-side rotational shaft Ax1 are coaxial. Here, the input-side rotational shaft Ax1 is the rotation center of the input shaft 500 to which the input rotation is given, and the output-side rotational shaft Ax1 is the rotation center of the inner ring 61 (and the pair of planetary carriers 18, 19) that generate the output rotation. That is, in the gear device 1, the output rotation after being reduced at a relatively high reduction ratio relative to the input rotation can be obtained on the same axis.

[0051] As shown in Figures 5 and 6, the internal gear 2 is an annular part with internal teeth 21. In this basic structure, at least the inner circumferential surface of the internal gear 2 has an annular shape that is a perfect circle when viewed from above. Internal teeth 21 are formed along the circumferential direction of the internal gear 2 on the inner circumferential surface of the annular internal gear 2. All the teeth constituting the internal teeth 21 are of the same shape and are arranged at equal pitch throughout the entire circumferential region of the inner circumferential surface of the internal gear 2. That is, the pitch circle of the internal teeth 21 is a perfect circle when viewed from above. The center of the pitch circle of the internal teeth 21 is located on the rotation axis Ax1. In addition, the internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. The tooth lines of the internal teeth 21 are all parallel to the rotation axis Ax1. The dimension of the internal teeth 21 in the tooth line direction is slightly smaller than the dimension of the internal gear 2 in the thickness direction.

[0052] Here, as described above, the internal gear 2 has an annular (ring-shaped) gear body 22 and multiple outer pins 23. The multiple outer pins 23 are held in a rotatable state on the inner circumferential surface 221 of the gear body 22 and constitute the internal gear 21. In other words, the multiple outer pins 23 function as multiple teeth constituting the internal gear 21. Specifically, as shown in FIG2, multiple inner circumferential grooves 223 are formed on the entire circumferential area of ​​the inner circumferential surface 221 of the gear body 22. All of the multiple inner circumferential grooves 223 are of the same shape and are arranged with equal pitch. The multiple inner circumferential grooves 223 are all parallel to the rotation axis Ax1 and are formed along the total length of the gear body 22 in the thickness direction. The multiple outer pins 23 are combined with the gear body 22 by being embedded in the multiple inner circumferential grooves 223. Each of the multiple outer pins 23 is held in a rotatable state within the inner circumferential groove 223. Furthermore, the gear body 22 (together with the outer ring 62) is fixed to the housing 10. Furthermore, multiple fixing holes 222 for fixing are formed in the gear body 22 (see Figure 5).

[0053] As shown in Figures 5 and 6, the planetary gear 3 is an annular part with external teeth 31. In this basic structure, at least the outer circumferential surface of the planetary gear 3 has an annular shape that is a perfect circle when viewed from above. External teeth 31 are formed on the outer circumferential surface of the annular planetary gear 3 along the circumferential direction of the planetary gear 3. All the teeth constituting the external teeth 31 are of the same shape and are arranged at equal pitch over the entire circumferential area of ​​the outer circumferential surface of the planetary gear 3. That is, the pitch circle of the external teeth 31 is a perfect circle when viewed from above. In addition, the planetary gear 3 has a predetermined thickness in the direction of the rotation axis Ax1. The external teeth 31 are all formed along the total length in the thickness direction of the planetary gear 3. The tooth lines of the external teeth 31 are all parallel to the rotation axis Ax1. In the planetary gear 3, unlike the internal gear 2, the external teeth 31 and the main body of the planetary gear 3 are integrally formed by a single metal component.

[0054] Furthermore, the gear assembly 1 of this basic structure includes a plurality of planetary gears 3. Specifically, the gear assembly 1 includes two planetary gears 3: a first planetary gear 301 and a second planetary gear 302. The two planetary gears 3 are arranged facing each other in a direction parallel to the rotation axis Ax1. That is, the planetary gears 3 include a first planetary gear 301 and a second planetary gear 302 arranged in a direction (axial direction) parallel to the rotation axis Ax1. The first planetary gear 301 and the second planetary gear 302 share a common shape.

[0055] These two planetary gears 3 (first planetary gear 301 and second planetary gear 302) are arranged about the rotation axis Ax1 with a phase difference of 180 degrees. In the example of Figure 4, the center (center of the pitch circle of the external tooth 31) C1 of the first planetary gear 301, located on the input side of the rotation axis Ax1 (the right side of Figure 4), is offset (biased) downwards relative to the rotation axis Ax1. On the other hand, the center (center of the pitch circle of the external tooth 31) C2 of the second planetary gear 302, located on the output side of the rotation axis Ax1 (the left side of Figure 4), is offset (biased) upwards relative to the rotation axis Ax1. Here, the distance ΔL1 between the rotation axis Ax1 and the center C1 is the eccentricity of the first planetary gear 301 relative to the rotation axis Ax1, and the distance ΔL2 between the rotation axis Ax1 and the center C2 is the eccentricity of the second planetary gear 302 relative to the rotation axis Ax1. In this way, by arranging multiple planetary gears 3 equally in the circumferential direction centered on the rotation axis Ax1, a balance of weight and load among the multiple planetary gears 3 can be achieved.

[0056] In the first planetary gear 301 and the second planetary gear 302, their centers C1 and C2 are located at positions symmetrically rotated 180 degrees relative to the rotation axis Ax1. In this basic structure, the eccentricities ΔL1 and ΔL2 have opposite orientations when viewed from the rotation axis Ax1, but their absolute values ​​are the same.

[0057] More specifically, each crankshaft 7A, 7B, and 7C has two eccentric portions 72 relative to a central shaft portion 71. The eccentricity ΔL0 of the center C0 of these two eccentric portions 72 from the center of the central shaft portion 71 (shaft Ax2) (refer to Figures 5 and 6) is the same as the eccentricity ΔL1 and eccentricity ΔL2 of the first planetary gear 301 and the second planetary gear 302 relative to the rotation axis Ax1, respectively. The shapes of the multiple crankshafts 7A, 7B, and 7C are common to each other. The shapes of the multiple crankshaft gears 502A, 502B, and 502C are also common to each other.

[0058] Furthermore, a pair of planetary carriers 18 and 19 are arranged on both sides of the first planetary gear 301 and the second planetary gear 302 in the direction parallel to the rotation axis Ax1 (axial direction). Distinguishing between the pair of planetary carriers 18 and 19, the planetary carrier 18 located on the input side of the rotation axis Ax1 (right side in Figure 4) is referred to as the "input-side planetary carrier 18," and the planetary carrier 19 located on the output side of the rotation axis Ax1 (left side in Figure 4) is referred to as the "output-side planetary carrier 19." The two ends of each crankshaft 7A, 7B, and 7C are held in place by the pair of planetary carriers 18 and 19 via crankshaft bearings 41 and 42. That is, each crankshaft 7A, 7B, and 7C is held on both sides of the planetary gear 3 in the direction parallel to the rotation axis Ax1 (axial direction) in a state capable of rotation.

[0059] An eccentric bearing 5 is installed in the eccentric portion 72 of each crankshaft 7A, 7B, and 7C. Each of the first planetary gear 301 and the second planetary gear 302 has three openings 33 corresponding to the three crankshafts 7A, 7B, and 7C. Furthermore, the eccentric bearing 5 is received in each opening 33. In other words, with the eccentric bearing 5 installed in the first planetary gear 301 and the second planetary gear 302, the eccentric bearing 5 and each crankshaft 7A, 7B, and 7C are combined into the planetary gear 3 by inserting each crankshaft 7A, 7B, and 7C into the eccentric bearing 5. With the eccentric bearing 5 and crankshafts 7A, 7B, and 7C combined in the planetary gear 3, when each crankshaft 7A, 7B, and 7C rotates, the planetary gear 3 oscillates around the rotation axis Ax1.

[0060] Based on the structure described above, a rotational force is applied as input to the input shaft 500, which rotates around the rotation axis Ax1. This rotational force is then distributed from the input gear 501 to multiple crankshafts 7A, 7B, and 7C. That is, when the input gear 501 rotates, the three crankshaft gears 502A, 502B, and 502C that mesh with the input gear 501 rotate in the same direction at the same speed. Since crankshafts 7A, 7B, and 7C are splinedly connected to each of the crankshaft gears 502A, 502B, and 502C, the three crankshafts 7A, 7B, and 7C rotate in the same direction at the same speed under reduced speed conditions due to the gear ratio between the input gear 501 and the crankshaft gears 502A, 502B, and 502C. As a result, the three eccentric portions 72 formed at the same position on the input side of the rotation shaft Ax1 of the three crankshafts 7A, 7B, and 7C rotate synchronously, causing the first planetary gear 301 to oscillate. Furthermore, the three eccentric portions 72 formed at the same position on the output side of the rotation shaft Ax1 of the three crankshafts 7A, 7B, and 7C rotate synchronously, causing the second planetary gear 302 to oscillate.

[0061] Figures 5 and 6 show the states of the first planetary gear 301 and the second planetary gear 302 at a certain point in time. Figure 5 is a cross-sectional view along line A1-A1 of Figure 4, showing the first planetary gear 301. Figure 6 is a cross-sectional view along line B1-B1 of Figure 4, showing the second planetary gear 302. As shown in Figures 5 and 6, the centers C1 and C2 of the first planetary gear 301 and the second planetary gear 302 are located at positions approximately symmetrical about 180 degrees relative to the rotation axis Ax1. In this basic structure, the eccentricities ΔL1 and ΔL2 have opposite orientations when viewed from the rotation axis Ax1, but their absolute values ​​are approximately the same (both are eccentricities ΔL0). According to this structure, the shaft center 71 rotates (rotates) around the shaft center Ax2, thereby causing the first planetary gear 301 and the second planetary gear 302 to rotate about the rotation axis Ax1 with a phase difference of approximately 180 degrees (eccentric motion). Furthermore, by arranging multiple planetary gears 3 approximately equally in the circumferential direction centered on the rotation axis Ax1, a balance of weight and load among the multiple planetary gears 3 can be achieved.

[0062] The planetary gears 3 (first planetary gear 301 and second planetary gear 302) configured in this way are positioned inside the internal gear 2. Viewed from above, the planetary gear 3 is one size smaller than the internal gear 2, allowing it to oscillate inside the internal gear 2 when combined with it. Here, external teeth 31 are formed on the outer circumferential surface of the planetary gear 3, and internal teeth 21 are formed on the inner circumferential surface of the internal gear 2. Therefore, when the planetary gear 3 is positioned inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0063] Furthermore, the pitch circle of the external tooth 31 is one size smaller than that of the internal tooth 21. Also, when the first planetary gear 301 is internally engaged with the internal gear 2, the center C1 of the pitch circle of the external tooth 31 of the first planetary gear 301 is located at a position offset by a distance ΔL1 from the center of the pitch circle of the internal tooth 21 (rotation axis Ax1). Similarly, when the second planetary gear 302 is internally engaged with the internal gear 2, the center C2 of the pitch circle of the external tooth 31 of the second planetary gear 302 is located at a position offset by a distance ΔL2 from the center of the pitch circle of the internal tooth 21 (rotation axis Ax1).

[0064] Therefore, in either the first planetary gear 301 or the second planetary gear 302, at least a portion of the external teeth 31 and the internal teeth 21 face each other with a gap. If the difference in the number of teeth between the external teeth 31 and the internal teeth 21 is 2 or more, they will not mesh together in the circumferential direction. However, since the planetary gear 3 oscillates (revolves) around the rotation axis Ax1 inside the internal gear 2, the external teeth 31 and the internal teeth 21 partially mesh. That is, by the oscillation of the planetary gears 3 (first planetary gear 301 and second planetary gear 302) around the rotation axis Ax1, as shown in Figures 5 and 6, a portion of the teeth constituting the external teeth 31 meshes with a portion of the teeth constituting the internal teeth 21. As a result, in the gear assembly 1, a portion of the external teeth 31 can mesh with a portion of the internal teeth 21.

[0065] Here, the number of teeth on the internal gear 21 of the internal gear 2 is N more than the number of teeth on the external gear 31 of the planetary gear 3 (N is a positive integer). In this basic structure, as an example, N is "2", and the number of teeth on the planetary gear 3 (external teeth 31) is "2" fewer than the number of teeth on the internal gear 2 (internal teeth 21). This difference in the number of teeth between the planetary gear 3 and the internal gear 2 defines the reduction ratio of the output rotation of the gear unit 1 relative to the input rotation.

[0066] Furthermore, in this basic structure, as an example, 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 of the internal gear 2. Moreover, the dimension of the external teeth 31 of the combined first planetary gear 301 and the second planetary gear 302 in the tooth line direction (parallel to the rotation axis Ax1) is smaller than the dimension of the internal teeth 21 in the tooth line direction (parallel to the rotation axis Ax1). In other words, in the direction parallel to the rotation axis Ax1, the external teeth 31 of the first planetary gear 301 and the second planetary gear 302 converge within the range of the tooth line of the internal teeth 21.

[0067] Here, the first planetary gear 301 and the second planetary gear 302 are internally meshed with the internal gear 2. Therefore, with each oscillation, the first planetary gear 301 and the second planetary gear 302 generate a phase deviation in the circumferential direction relative to the internal gear 2, corresponding to the difference in the number of teeth (between the internal teeth 21 and the external teeth 31), and rotate. This rotation, as the revolution of each crankshaft 7A, 7B, 7C around the axis (rotation axis Ax1) of the internal gear 2, is transmitted to a pair of planet carriers 18 and 19. Thus, with rotation axis Ax1 as the center, the pair of planet carriers 18 and 19 can rotate relative to (and) the gear body (integrated housing 10).

[0068] In summary, the gear assembly 1 of this basic structure utilizes multiple crankshafts 7A, 7B, and 7C positioned offset from the rotation axis Ax1 to oscillate the planetary gear 3, thereby obtaining rotational output through the oscillation of the planetary gear 3. Specifically, in the gear assembly 1, when the planetary gear 3 oscillates and the meshing position of the internal teeth 21 and external teeth 31 moves in the circumferential direction of the internal gear 2, a relative rotation is generated between the two gears (internal gear 2 and planetary gear 3) corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2. Here, if the internal gear 2 is fixed, the planetary gear 3 rotates (spins) as the two gears rotate relative to each other. As a result, based on the difference in the number of teeth between the two gears, a rotational output with a relatively high reduction ratio is obtained from the planetary gear 3.

[0069] The bearing assembly 6 is a component having an outer ring 62 and an inner ring 61, used to extract the output of the gear assembly 1 by rotating the inner ring 61 relative to the outer ring 62. In addition to the outer ring 62 and inner ring 61, the bearing assembly 6 also has multiple rolling elements 63 (see Figure 4). Both the outer ring 62 and the inner ring 61 are annular parts. Both the outer ring 62 and the inner ring 61 are circular rings that appear perfectly round when viewed from above. The inner ring 61 is smaller than the outer ring 62 and is positioned 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 created between the inner circumferential surface of the outer ring 62 and the outer circumferential surface of the inner ring 61.

[0070] Multiple rolling elements 63 are disposed in the gap between the outer ring 62 and the inner ring 61. The multiple rolling elements 63 are arranged in the circumferential direction of the outer ring 62. All of the multiple rolling elements 63 are metal parts of the same shape and are arranged at equal pitch throughout the circumferential direction of the outer ring 62.

[0071] More specifically, the gear assembly 1 of this basic structure includes a first main bearing 601 and a second main bearing 602, which are bearing assemblies 6. That is, the gear assembly 1 includes a pair of bearing assemblies 6 comprising the first main bearing 601 and the second main bearing 602. Specifically, as shown in FIG4, when viewed from the planetary gear 3, the first main bearing 601 is arranged on the input side of the rotating shaft Ax1 (the right side of FIG4), and the second main bearing 602 is arranged on the output side of the rotating shaft Ax1 (the left side of FIG4). The pair of bearing assemblies 6 are configured such that, by means of the first main bearing 601 and the second main bearing 602, they can withstand any of the following: loads in the radial direction, loads in the thrust direction (along the direction of the rotating shaft Ax1), and bending forces (bending moment loads) on the rotating shaft Ax1.

[0072] Here, the first main bearing 601 and the second main bearing 602 are arranged on opposite sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1 (axial direction), with opposing orientations in the same direction. As an example, the pair of bearing assemblies 6 are of a "back-end combination type" where the inner rings 61 of the first main bearing 601 and the second main bearing 602 bear loads in a mutually outward thrust direction (along the rotation axis Ax1). Furthermore, in the gear assembly 1, the first main bearing 601 and the second main bearing 602 are combined under appropriate preload by fastening their respective inner rings 61 toward each other.

[0073] Furthermore, in the gear assembly 1 of this basic structure, the input-side planetary carrier 18 and the output-side planetary carrier 19 are arranged on opposite sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1, and are engaged with each other via the planetary carrier bore 34 of the planetary gear 3 (see Figure 4). Specifically, as shown in Figure 4, when viewed from the planetary gear 3, the input-side planetary carrier 18 is arranged on the input side of the rotation axis Ax1 (the right side of Figure 4), and the output-side planetary carrier 19 is arranged on the output side of the rotation axis Ax1 (the left side of Figure 4). The inner rings 61 of a pair of bearing assemblies 6 (the first main bearing 601 and the second main bearing 602) are fixed to the input-side planetary carrier 18 and the output-side planetary carrier 19, respectively. In this basic structure, as an example, the inner ring 61 of the first main bearing 601 is fixed to the input-side planetary carrier 18. Similarly, the inner ring 61 of the second main bearing 602 is fixed to the output-side planetary carrier 19.

[0074] The output-side planetary carrier 19 has a plurality of (three in one example) planetary carrier pins 191 (see Figure 2) protruding from one surface of the output-side planetary carrier 19 toward the input side of the rotation axis Ax1. These plurality of planetary carrier pins 191 pass through a plurality of (three in one example) planetary carrier bores 34 formed in the planetary gear 3, and their tips are fixed to the input-side planetary carrier 18 by planetary carrier bolts. Here, a clearance is ensured between the planetary carrier pins 191 and the inner circumferential surface of the planetary carrier bores 34, thereby allowing the planetary carrier pins 191 to move within the planetary carrier bores 34, i.e., to move relative to the center of the planetary carrier bores 34. Therefore, when the planetary gear 3 oscillates, the planetary carrier pins 191 do not contact the inner circumferential surface of the planetary carrier bores 34.

[0075] With the aforementioned structure, the gear assembly 1 is used in such a way that the rotation corresponding to the rotational component of the planetary gear 3 is taken out as the rotation of the input-side planetary carrier 18 and the output-side planetary carrier 19, on which the inner ring 61 of the pair of bearing assemblies 6 (first main bearing 601 and second main bearing 602) is fixed. That is, in this basic structure, the relative rotation between the planetary gear 3 and the internal gear 2 is taken out from the input-side planetary carrier 18 and the output-side planetary carrier 19. In this basic structure, as an example, the gear assembly 1 is used with the outer ring 62 (see Figure 4) of the pair of bearing assemblies 6 (first main bearing 601 and second main bearing 602) fixed in the housing 10, which serves as a fixed member. That is, the planetary gear 3 is connected to the input-side planetary carrier 18 and the output-side planetary carrier 19, which serve as rotating members, via multiple crankshafts 7A, 7B, and 7C, and the gear body 22 is fixed to the fixed member, so the relative rotation between the planetary gear 3 and the internal gear 2 is taken out from the rotating members (input-side planetary carrier 18 and output-side planetary carrier 19). In other words, in this basic structure, the rotational force of the input-side planetary carrier 18 and the output-side planetary carrier 19 is taken out as output when the planetary gear 3 rotates relative to the gear body 22.

[0076] Furthermore, in this basic structure, the housing 10 and the gear body 22 of the internal gear 2 are seamlessly integrated. That is, in the direction parallel to the rotation axis Ax1, the gear body 22, as a fixing member, is seamlessly and continuously provided with the housing 10.

[0077] More specifically, the housing 10 is cylindrical and forms the outline of the gear assembly 1. In this basic structure, the central axis of the cylindrical housing 10 is aligned with the rotation axis Ax1. That is, at least the outer peripheral surface of the housing 10 is a perfect circle centered on the rotation axis Ax1 when viewed from above (viewed from one side of the axial direction). The housing 10 is formed as a cylinder with open ends in the axial direction. Here, the gear body 22 of the internal gear 2 is seamlessly integrated with the housing 10, and the housing 10 and the gear body 22 are treated as a single part. Therefore, the inner peripheral surface of the housing 10 includes the inner peripheral surface 221 of the gear body 22. Furthermore, the outer ring 62 of a pair of bearing assemblies 6 (first main bearing 601 and second main bearing 602) is fixed in the housing 10. That is, when viewed from the gear body 22 on the inner peripheral surface of the housing 10, the outer ring 62 of the first main bearing 601 is fixed by embedding on the input side of the rotation axis Ax1 (right side of FIG. 4). On the other hand, when viewed from the gear body 22 on the inner circumferential surface of the housing 10, the outer ring 62 of the second main bearing 602 is fixed by embedding on the output side of the rotating shaft Ax1 (left side of FIG4).

[0078] Furthermore, the end face of the input side (right side of Figure 4) of the rotation shaft Ax1 of the housing 10 is closed by the input-side planetary carrier 18, and the end face of the output side (left side of Figure 4) of the rotation shaft Ax1 of the housing 10 is closed by the output-side planetary carrier 19. Therefore, as shown in Figure 4, the space surrounded by the housing 10, the input-side planetary carrier 18, and the output-side planetary carrier 19 houses planetary gears 3 (first planetary gear 301 and second planetary gear 302), multiple outer pins 23, and eccentric bearings 5, among other components.

[0079] Multiple crankshafts 7A, 7B, and 7C (three in the basic structure) each have a central shaft portion 71 and two eccentric portions 72. The central shaft portion 71 has at least an outer circumferential surface that is a perfect circle when viewed from above, forming a cylindrical shape. The shaft center Ax2, which is the center of the central shaft portion 71, is parallel to the rotation axis Ax1. The shaft centers Ax2 of the multiple crankshafts 7A, 7B, and 7C are arranged at equal intervals along the circumferential direction on a virtual circle centered on the rotation axis Ax1. The outer circumferential surface of each eccentric portion 72 has at least an outer circumferential surface that is a perfect circle when viewed from above, forming a disk shape. The center (central axis) C0 of each eccentric portion 72 is parallel to the rotation axis Ax1 and is positioned radially offset from the rotation axis Ax1. Here, the distance ΔL0 between the shaft center Ax2 and the center C0 (refer to Figures 5 and 6) is the eccentricity of the eccentric portion 72 relative to the central shaft portion 71. The eccentric portion 72 has a flange shape at its center along the long side (axial direction) of the shaft portion 71, protruding from the outer circumference of the shaft portion 71. According to the structure described, each crankshaft 7A, 7B, 7C rotates (self-rotates) around the shaft center Ax2 via the shaft portion 71, thereby causing the eccentric portion 72 to perform eccentric motion.

[0080] In this basic structure, the central shaft 71 and the two eccentric shafts 72 are integrally formed from a single metal component, thereby achieving seamless crankshafts 7A, 7B, and 7C. These crankshafts 7A, 7B, and 7C, in this shape, are combined with the eccentric bearing 5 and then integrated into the planetary gear 3. Therefore, with the planetary gear 3 assembled with the eccentric bearing 5 and the crankshafts 7A, 7B, and 7C, the planetary gear 3 oscillates around the rotation axis Ax1 when the crankshafts 7A, 7B, and 7C rotate.

[0081] The eccentric bearing 5 is a component having multiple rolling elements 51 (see Figure 4) for absorbing the rotational component of crankshafts 7A, 7B, and 7C, and transmitting the rotational component of crankshafts 7A, 7B, and 7C, i.e., only the oscillating component (revolutionary component), to the planetary gear 3 after removing the rotational component of crankshafts 7A, 7B, and 7C. The multiple rolling elements 51 are arranged between the outer peripheral surface of the eccentric portion 72 of each crankshaft 7A, 7B, and 7C and the inner peripheral surface of each opening 33 of the planetary gear 3. That is, the eccentric portion 72 of each crankshaft 7A, 7B, and 7C functions as the inner ring of the eccentric bearing 5, and the inner peripheral surface of each opening 33 of the planetary gear 3 functions as the outer ring of the eccentric bearing 5.

[0082] With the eccentric bearing 5 and multiple crankshafts 7A, 7B, and 7C assembled into the planetary gear 3, when each crankshaft 7A, 7B, and 7C rotates (self-rotates), each eccentric part 72 rotates (eccentrically moves) around the axis Ax2. The planetary gear 3 is positioned in a direction parallel to the rotation axis Ax1 (axial direction) corresponding to each eccentric part 72. Therefore, the eccentric motion of each eccentric part 72 is transmitted to the planetary gear 3 via the eccentric bearing 5, and the planetary gear 3 oscillates around the rotation axis Ax1. That is, the eccentric motion of the eccentric parts 72 of crankshafts 7A, 7B, and 7C is transmitted to the planetary gear 3. The eccentric bearing 5 functions as follows: mitigating friction caused by the relative rotation due to the speed difference between the eccentric motion of the eccentric parts 72 of each crankshaft 7A, 7B, and 7C (i.e., the self-rotation of each crankshaft 7A, 7B, and 7C) and the revolution of the planetary gear 3, and also serving as a power transmission mechanism.

[0083] In the gear assembly 1 of the described structure, a rotational force is applied as input to the input shaft 500, which rotates around the rotation axis Ax1, causing the planetary gear 3 to oscillate (revolve) around the rotation axis Ax1. At this time, the planetary gear 3 is internally engaged with the internal gear 2 on the inner side, and oscillates while a portion of the external teeth 31 meshes with a portion of the internal teeth 21. Therefore, as the input shaft 500 rotates, the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2. This generates a relative rotation between the two gears (internal gear 2 and planetary gear 3) corresponding to the difference in the number of teeth between the planetary gear 3 and the internal gear 2. Furthermore, the rotation (rotational component) of the planetary gear 3, after the oscillation component (revolutionary component) has been removed, is transmitted to a pair of planetary carriers 18 and 19 via multiple crankshafts 7A, 7B, and 7C. As a result, a rotational output with a relatively high reduction ratio is obtained from the pair of planetary carriers 18 and 19, based on the difference in the number of teeth between the two gears.

[0084] Furthermore, in the gear device 1 of this basic structure, as described above, 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 of the gear device 1 relative to the input rotation. That is, when the number of teeth of the internal gear 2 is set to "V1" and the number of teeth of the planetary gear 3 is set to "V2", the reduction ratio R1 is expressed by the following formula 1.

[0085] R1=V2 / (V1-V2)(Formula 1)

[0086] In summary, the smaller the difference in the number of teeth (V1-V2) between the internal gear 2 and the planetary gear 3, the larger the reduction ratio R1. As an example, since 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 difference in the number of teeth (V1-V2) is "2", the reduction ratio R1 is "35" according to Equation 1. In this case, when viewed from the input side of the rotating shaft Ax1, each crankshaft 7A, 7B, 7C rotates clockwise one revolution (360 degrees) around the axis Ax2 of the shaft center 71 (refer to Figures 5 and 6), the pair of planetary carriers 18, 19 rotate counterclockwise around the rotating shaft Ax1 by an amount corresponding to the difference in the number of teeth "2" (i.e., approximately 10.3 degrees).

[0087] According to the gear device 1 of this basic structure, such a high reduction ratio R1 can be achieved through the combination of internal gear 2 and planetary gear 3. Furthermore, between the input gear 501 and the multiple crankshaft gears 502A, 502B, and 502C, a suitable reduction ratio can also be achieved based on the number of teeth of the input gear 501 and the crankshaft gears 502A, 502B, and 502C. As a result, the gear device 1 as a whole can achieve a high reduction ratio.

[0088] As shown in Figure 7, the gear assembly 1 of this basic structure, together with the first component 201 and the second component 202, constitutes a robot joint device 200. In other words, the robot joint device 200 of this basic structure includes: a gear assembly 1, a first component 201, and a second component 202. The first component 201 is fixed to the gear body 22. The second component 202 rotates relative to the first component 201 as the planetary gear 3 rotates relative to the internal gear 2. Figure 7 is a schematic cross-sectional view of the robot joint device 200. In addition, the first component 201, the second component 202, and the drive source 101 are schematically shown in Figure 7.

[0089] The robot joint device 200 configured in this way functions as a joint device by rotating relative to each other about a rotation axis Ax1 via a first component 201 and a second component 202. Here, the input shaft 500 of the gear device 1 is driven by a drive source 101, thereby causing the first component 201 and the second component 202 to rotate relative to each other. At this time, the rotation generated by the drive source 101 (input rotation) is reduced in the gear device 1 with a relatively high reduction ratio, and drives the first component 201 or the second component 202 with a relatively high torque. That is, the first component 201 and the second component 202 connected by the gear device 1 can perform flexion and extension movements about a rotation axis Ax1.

[0090] The robot joint device 200 is used, for example, in robots such as horizontal articulated robots (SCARA (Selective Compliance Assembly Robot Arm) type robots). Furthermore, the robot joint device 200 is not limited to horizontal articulated robots; it can also be used in industrial robots other than horizontal articulated robots, or in robots for other purposes. Additionally, the gear device 1 of this basic structure is not limited to the robot joint device 200; it can also be used as a wheel device such as an in-wheel motor in vehicles such as Automated Guided Vehicles (AGVs).

[0091] (3.2) Crankshaft support structure

[0092] Next, the support structures of crankshafts 7A, 7B, and 7C used in the gear assembly 1 of this basic structure will be described with reference to FIG8. Since the multiple (here, three) crankshafts 7A, 7B, and 7C have a common structure including their support structures, crankshaft 7A will be used as an example in the following description. FIG8 is a schematic cross-sectional view of the main part of the gear assembly 1 (the area corresponding to region Z1 in FIG4). In FIG8, the illustration of the bearing assembly 6 (first main bearing 601 and second main bearing 602) is simplified, and the illustrations of the inner ring 61, outer ring 62, and multiple rolling elements 63 are omitted.

[0093] The two ends of the crankshaft 7A along its axial direction (parallel to the axis Ax2) are held in place by a pair of planetary carriers 18 and 19 via crankshaft bearings 41 and 42. Specifically, the input side (right side of FIG. 8) of the crankshaft 7A has its shaft center 71 supported on the input side planetary carrier 18 via the crankshaft bearing 41, and the output side (left side of FIG. 8) of the crankshaft 7A has its shaft center 71 supported on the output side planetary carrier 19 via the crankshaft bearing 42. Thus, the crankshaft 7A is supported by the pair of planetary carriers 18 and 19 in a state where it can rotate.

[0094] In this basic structure, as an example, each crankshaft bearing 41 and 42 is a needle bearing. Each crankshaft bearing 41 and 42 has an outer ring 401, a plurality of rolling elements 402, and a retainer 403. Here, the core portion 71 of the crankshaft 7A functions as the inner ring of each crankshaft bearing 41 and 42.

[0095] The outer ring 401 is formed into a circular annulus when viewed from one side of the axial direction (e.g., the input side). The inner diameter of the outer ring 401 is larger than the outer diameter of the shaft center portion 71, and it is disposed around the shaft center portion 71 of the crankshaft 7A. That is, since the inner diameter of the outer ring 401 is larger than the outer diameter of the shaft center portion 71, a gap is generated between the inner circumferential surface of the outer ring 401 and the outer circumferential surface of the shaft center portion 71.

[0096] Multiple rolling elements 402 are each formed as a cylinder (or cylindrical shape) having a length in the axial direction (parallel to the axis Ax2). The multiple rolling elements 402 are disposed between the inner circumferential surface of the outer ring 401 and the outer circumferential surface of the shaft center portion 71 of the crankshaft 7A. The multiple rolling elements 402 are arranged in the circumferential direction of the outer ring 401. All multiple rolling elements 402 are metal parts of the same shape and are arranged at equal pitch throughout the entire circumferential region of the outer ring 401.

[0097] In this basic structure, the outer ring 401 and the multiple rolling elements 402, which are structural components of the crankshaft bearings 41 and 42, are made of metals such as stainless steel, bearing steel, carbon steel for mechanical structures, chromium-molybdenum steel, phosphor bronze, or aluminum bronze, or light metals such as aluminum or titanium. The metals mentioned here (including light metals) include metals that have undergone surface treatments such as nitriding. Furthermore, surface treatments may also include blackening treatments (ferromite treatment) to form a black oxide film on the surface. Blackening treatments are considered effective in preventing the peeling of the white layer caused by hydrogen embrittlement caused by hydrogen absorbing hydrogen from the metal surface and in suppressing the creep of the outer ring 401.

[0098] The retainer 403 is a component that holds a plurality of rolling elements 402 between the inner circumferential surface of the outer ring 401 and the outer circumferential surface of the shaft portion 71. The retainer 403 is disposed between the inner circumferential surface of the outer ring 401 and the outer circumferential surface of the shaft portion 71. The retainer 403 is formed into a circular ring when viewed from one side of the axial direction (e.g., the input side). The retainer 403 has a plurality of pockets in the circumferential direction (circumferential direction of the outer ring 401). By housing the rolling elements 402 in each of these pockets, the retainer 403 holds the plurality of rolling elements 402. Moreover, by holding the plurality of rolling elements 402 in a rolling state, the retainer 403 holds the plurality of rolling elements 402 at an equal pitch between the outer ring 401 and the inner ring (shaft portion 71). The retainer 403 is a molded product of resin (synthetic resin) or the like.

[0099] Thus, the crankshaft 7A is supported on a pair of planetary carriers 18 and 19 via crankshaft bearings 41 and 42 at its two ends in the axial direction, and is therefore supported to rotate in the state of passing through the planetary gear 3.

[0100] Furthermore, the gear device 1 of this basic structure has a structure for limiting the axial movement of the crankshaft 7A (in the direction parallel to the axis Ax2). Roughly speaking, the axial movement of the crankshaft 7A is limited by a structure in which a pair of planetary carriers 18 and 19 clamp the crankshaft 7A from both sides in the axial direction.

[0101] More specifically, in this basic structure, the output-side planetary carrier 19 has a recess 81 that opens toward the axial output side (right side of FIG. 8). The output-side planetary carrier 19 supports one end (axis 71) of the crankshaft 7A within the recess 81 via a crankshaft bearing 42, enabling it to rotate. The gear assembly 1 also includes a limiting member 82 disposed within the recess 81. The limiting member 82, by contacting the crankshaft 7A, restricts movement of the crankshaft 7A toward the bottom surface 811 side of the recess 81 (left side of FIG. 8).

[0102] Here, regarding the crankshaft bearing 42, when it is axially separated from the limiting member 82, its relative movement relative to the crankshaft 7A towards the bottom surface 811 of the recess 81 (left side of FIG. 8) is restricted. That is, the limiting member 82 directly restricts the movement of the crankshaft 7A towards the bottom surface 811, thereby indirectly restricting the movement of the crankshaft bearing 42 towards the bottom surface 811, which is also restricted in relative movement with respect to the crankshaft 7A.

[0103] As described above, the gear assembly 1 of this basic structure includes: an internal gear 2, a planetary gear 3, a crankshaft 7A, a crankshaft 7B, a crankshaft 7C, a planet carrier 19, and a limiting member 82. The internal gear 2 has: an annular gear body 22, and multiple outer pins 23 that are held in a rotatable state in a plurality of inner circumferential grooves 223 formed by the inner circumferential surface 221 of the gear body 22 and constitute the internal gear 21. The planetary gear 3 has outer teeth 31 that partially mesh with the internal gear 21. The crankshafts 7A, 7B, and 7C rotate about an axis Ax2, causing the planetary gear 3 to oscillate. The planet carrier 19 has a recess 81, within which the crankshafts 7A, 7B, and 7C are supported for rotation via a crankshaft bearing 42. The limiting member 82 is disposed within the recess 81 of the planetary carrier 19 such that it faces one end face (left end face in FIG. 8) of the crankshafts 7A, 7B, and 7C in the axial direction. The gear assembly 1 causes the planetary gear 3 to rotate relative to the internal gear 2 by oscillating the planetary gear 3. The gear assembly 1 restricts the movement of the crankshafts 7A, 7B, and 7C toward the bottom surface 811 of the recess 81 by bringing the crankshafts 7A, 7B, and 7C into contact with the limiting member 82. The crankshaft bearing 42, when axially separated from the limiting member 82, is restricted from relative axial movement toward the bottom surface 811 of the crankshafts 7A, 7B, and 7C.

[0104] According to the structure described above, the limiting member 82 disposed within the recess 81 of the planetary carrier 19 can directly restrict the axial movement of crankshafts 7A, 7B, and 7C toward the bottom surface 811 of the recess 81 (left side of FIG. 8), and indirectly restrict the axial movement of crankshaft bearing 42 toward the bottom surface 811 of the recess 81 (left side of FIG. 8). In this case, it is not necessary to form a clearance portion with a diameter larger than the support surface (supporting crankshaft bearing 42) on the inner circumferential surface 812 of the recess 81, thus easily simplifying the shape of the planetary carrier 19. Therefore, the gear device 1 according to this basic structure has the advantage of easily simplifying the shape of each component.

[0105] To elaborate further, the recess 81 is formed into a circular shape that appears as a perfect circle when viewed from one side of the axial direction (e.g., the input side). The inner diameter of the recess 81 is approximately the same as the outer diameter of the outer ring 401 of the crankshaft bearing 42, which is configured to be embedded within the recess 81.

[0106] On the bottom surface 811 of the recess 81, a step 811A is formed at the boundary between the central portion and the outer periphery. Inside the step 811A, the recess 81 is deeper than outside the step 811A. In the center of the inner region of the step 811A on the bottom surface 811 of the planet carrier 19, a hole 192 is formed that penetrates the planet carrier 19 axially. Furthermore, on the inner peripheral surface 812 of the recess 81, a step 812A is formed at the boundary between the bottom surface 811 side and the opening side axially. On the bottom surface 811 side of the step 812A, the diameter of the recess 81 is smaller than on the opening side of the step 812A.

[0107] The limiting member 82 is formed into a circular ring when viewed from one side of the axial direction (e.g., the input side). The outer diameter of the limiting member 82 is approximately the same as the inner diameter of the step 811A of the bottom surface 811 of the recess 81, and the limiting member 82 is arranged to be embedded in the space surrounded by the step 811A. The limiting member 82 is housed in the recess 81 with the surface opposite to the crankshaft 7A (output side) in contact with the bottom surface 811 of the recess 81.

[0108] Here, the limiting member 82 has a through hole 821 that extends through the limiting member 82 axially. The through hole 821 is located at the center of the limiting member 82 as viewed from one side (e.g., the input side) axially. The through hole 821 communicates with a hole 192 formed on the bottom surface 811 of the recess 81 of the planetary carrier 19. This allows lubricant (lubricating oil) to flow through the through hole 821, thus easily ensuring lubrication of, for example, the crankshaft bearing 42, etc.

[0109] Here, as shown in FIG8, in this basic structure, the gear device 1 includes a retaining ring 83, which is used to achieve the relative positioning of the crankshaft bearing 42 with respect to the crankshaft 7A. The retaining ring 83 is, for example, a C-ring or an E-ring, and is installed on the axial output side end of the crankshaft 7A using a groove formed on the outer peripheral surface of the end (shaft core 71) of the crankshaft 7A on the axial output side (left side of FIG8). In this basic structure, an annular washer 84 is disposed between the retaining ring 83 and the crankshaft bearing 42.

[0110] In summary, the relative movement of the crankshaft bearing 42 toward the bottom surface 811 relative to the crankshaft 7A is limited by the retaining ring 83 installed on the crankshaft 7A. According to this structure, the relative movement of the crankshaft bearing 42 relative to the crankshaft 7A can be limited with a relatively simple structure.

[0111] Furthermore, in this basic structure, the outer ring 401 of the crankshaft bearing 42 is embedded in the recess 81 of the planetary carrier 19 and would not normally move axially. That is, in this basic structure, the concern regarding axial movement of the crankshaft bearing 42 lies in the plurality of rolling elements 402 and the retainer 403. Therefore, in this basic structure, the retaining ring 83 directly or indirectly (via the retainer 403) restricts the movement of the plurality of rolling elements 402 toward the bottom surface 811.

[0112] Thus, the crankshaft bearing 42 has a plurality of rolling elements 402, which restrict the relative movement of the crankshaft 7A toward the bottom surface 811. Therefore, the relative movement of the crankshaft bearing 42 relative to the crankshaft 7A can be restricted with a relatively simple structure. In particular, by having a washer 84 spaced between the retaining ring 83 and the crankshaft bearing 42, the relative movement of the crankshaft bearing 42 relative to the crankshaft 7A can be restricted without hindering the movement of the crankshaft bearing 42.

[0113] Furthermore, as described above, the gear device 1 of this basic structure is a "distribution type" gear device 1 that applies a rotational force as input to the input shaft 500, causing the input shaft 500 to rotate around the rotation axis Ax1, thereby distributing the rotational force from the input gear 501 to multiple crankshafts 7A, 7B, and 7C. That is, the gear device 1 includes a distribution section that distributes the rotation of one input gear 501 to multiple crankshafts 7A, 7B, and 7C via multiple crankshaft gears 502A, 502B, and 502C. The planetary gear 3 oscillates due to the rotation of the multiple crankshafts 7A, 7B, and 7C.

[0114] Thus, in the gear assembly 1 having multiple (here, three) crankshafts 7A, 7B, and 7C, the aforementioned support structure for crankshaft 7A can be applied to all of the multiple crankshafts 7A, 7B, and 7C. That is, for any one of the multiple crankshafts 7A, 7B, and 7C, movement of crankshaft 7A, crankshaft 7B, and crankshaft 7C toward the bottom surface 811 of the recess 81 is restricted by bringing them into contact with the restricting member 82. Moreover, for any one of the multiple crankshafts 7A, 7B, and 7C, the crankshaft bearing 42 is restricted from relative movement relative to crankshaft 7A, crankshaft 7B, and crankshaft 7C toward the bottom surface 811 in the axial direction while being separated from the restricting member 82. Therefore, the gear assembly 1 according to this basic structure has the advantage of easily simplifying the shape of each component.

[0115] (4) Variations

[0116] The basic structure is merely one of many examples of this disclosure. Various modifications to the basic structure can be made to achieve the intended purpose of this disclosure, depending on the design. Furthermore, the accompanying drawings referenced in this disclosure are schematic, and the proportions of the size and thickness of each structural component in the drawings are not necessarily limited to reflecting actual dimensions. The following are examples of variations of the basic structure. These variations can be appropriately combined and applied.

[0117] The number of crankshafts 7A, 7B, and 7C is not limited to "3," and can also be 2 or more. Furthermore, if there is only one crankshaft, an eccentric oscillating type internal meshing planetary gear device, where the rotation axis Ax1 is aligned with the crankshaft axis Ax2, can be realized, rather than a distribution type. In this case, by driving the crankshaft, the planetary gear 3 oscillates, allowing a pair of planet carriers 18 and 19 to rotate relative to the gear body 22 with the rotation axis Ax1 as the center.

[0118] Furthermore, although the basic structure illustrates two types of gear devices 1 with planetary gears 3, the gear device 1 may also include three or more planetary gears 3. For example, when the gear device 1 includes three planetary gears 3, these three planetary gears 3 are preferably arranged with a phase difference of 120 degrees around the rotation axis Ax1. Alternatively, the gear device 1 may include only one planetary gear 3. Or, when the gear device 1 includes three planetary gears 3, two of these three planetary gears 3 may be in the same phase, and the remaining planetary gear 3 may be arranged with a phase difference of 180 degrees around the rotation axis Ax1.

[0119] In addition, the bearing assembly 6 can be an angular contact ball bearing, a cross roller bearing, a deep groove ball bearing, or a four-point contact ball bearing, etc. The rolling element 63 is not limited to a generally cylindrical shape (generally cylindrical), for example, it can also be frustoconical.

[0120] Furthermore, the number of teeth of the input gear 501, crankshaft gear 502A, crankshaft gear 502B, crankshaft gear 502C, the number of outer pins 23 (the number of teeth of the inner teeth 21), and the number of teeth of the outer teeth 31 described in the basic structure are just examples and can be appropriately changed.

[0121] In addition, the eccentric bearing 5 is not limited to roller bearings; for example, it can also be a deep groove ball bearing or an angular contact ball bearing.

[0122] In addition, crankshaft bearings 41 and 42 are not limited to needle roller bearings; for example, they can also be deep groove ball bearings or angular contact ball bearings.

[0123] Furthermore, the materials of the structural components of the gear device 1 are not limited to metal; for example, they can be resins such as engineering plastics. Conversely, the material of the retainer 403 is not limited to resin; for example, it can be metals.

[0124] Furthermore, the gear device 1 can be used as long as the relative rotation between the inner ring 61 and the outer ring 62 of the bearing device 6 is taken out as the output, and is not limited to the structure that takes out the rotational force of the inner ring 61 (the input-side planetary carrier 18 and the output-side planetary carrier 19) as the output. For example, the rotational force of the outer ring 62 (the housing 10) that rotates relative to the inner ring 61 can also be taken out as the output.

[0125] Alternatively, in the basic structure, a clearance portion with a diameter larger than the support surface (which supports the crankshaft bearing 42) can be formed on the inner circumferential surface 812 of the recess 81. This makes it easier to remove machining chips from the recess 81 during honing.

[0126] In addition, lubricants are not limited to liquid substances such as lubricating oil, but can also be gel-like substances such as lubricating grease.

[0127] (Implementation Method 1)

[0128] Regarding the internal meshing planetary gear device 1A (hereinafter also simply referred to as "gear device 1A") of this embodiment, as shown in FIG9, the support structures of crankshaft 7A, crankshaft 7B, and crankshaft 7C are different from those of the basic gear device 1. Hereinafter, common symbols will be used to mark structures that are the same as those in the basic structure, and explanations may be omitted as appropriate.

[0129] In the gear assembly 1A of this embodiment, since the multiple (here, three) crankshafts 7A, 7B, and 7C have a common structure including their support structures, the following description will take crankshaft 7A as an example. FIG9 is a schematic cross-sectional view of the main part of the gear assembly 1A (the area corresponding to region Z1 in FIG4). In FIG9, the illustration of the bearing assembly 6 (first main bearing 601 and second main bearing 602) is simplified, and the illustrations of the inner ring 61, outer ring 62, and multiple rolling elements 63 are omitted.

[0130] That is, the gear device 1A of this embodiment includes a connecting member 85. The connecting member 85 connects the outer ring 401 of the crankshaft bearing 42 to the limiting member 82 within the recess 81. In this embodiment, the limiting member 82, the connecting member 85, and the outer ring 401 are integrally formed from a single metal member. That is, a part that integrally forms the limiting member 82 and the outer ring 401 using the connecting member 85 is disposed within the recess 81. Furthermore, compared to the outer ring 401 and the limiting member 82, the connecting member 85 is formed with a thin wall.

[0131] Thus, in this embodiment, the crankshaft bearing 42 has an outer ring 401 embedded in the recess 81, and the outer ring 401 is connected to the limiting member 82 via a connecting member 85. Therefore, the limiting member 82 and the outer ring 401 can be treated as a single component, improving the assemblability of the gear assembly 1A.

[0132] In other words, in this embodiment, the limiting member 82 has a bottom 822 and a peripheral wall 823. The bottom 822 corresponds to the limiting member 82 in the basic structure, and is annular, and is housed in the recess 81 with the surface opposite to the crankshaft 7A (output side) in contact with the bottom surface 811 of the recess 81. The peripheral wall 823 forms the outer ring 401 of the crankshaft bearing 42. The limiting member 82 is formed by these bottom 822 and peripheral wall 823 in a cross-sectional shape that is approximately C-shaped.

[0133] That is, the limiting member 82 has a bottom 822 and a peripheral wall 823. The bottom 822 faces one end face of the crankshaft 7A in the axial direction (parallel to the axis Ax2). The peripheral wall 823 protrudes from the outer periphery of the bottom 822 toward the side opposite to the bottom surface 811 of the recess 81 in the axial direction. The limiting member 82 limits the movement of the crankshaft 7A toward the bottom surface 811 by bringing the crankshaft 7A into contact with the bottom 822. The peripheral wall 823 forms the outer ring 401 of the crankshaft bearing 42.

[0134] According to the structure described above, the bottom 822 of the limiting member 82, which is integrated with the outer ring 401 of the crankshaft bearing 42, can restrict the axial movement of the crankshafts 7A, 7B, and 7C toward the bottom surface 811 of the recess 81 (left side of FIG. 9). In this case, it is not necessary to form a clearance portion with a diameter larger than the support surface (which supports the crankshaft bearing 42) on the inner circumferential surface 812 of the recess 81, making it easy to simplify the shape of the planetary carrier 19. Therefore, the gear device 1A according to this embodiment has the advantage of easily simplifying the shape of each component.

[0135] In addition, in this embodiment, the bottom 822 also has a through hole 821, which is located at the center when viewed from one side in the axial direction and extends through the bottom 822 in the axial direction. The through hole 821 communicates with the hole 192 formed on the bottom surface 811 of the recess 81 of the planetary carrier 19. As a result, lubricant (lubricating oil) can flow through the through hole 821, for example, easily ensuring the lubrication of the crankshaft bearing 42, etc.

[0136] Furthermore, in this embodiment, the bottom surface 811 of the recess 81 has no step 811A, and the bottom surface 811 is formed flat. Similarly, the inner circumferential surface 812 of the recess 81 has no step 812A, and the inner diameter of the inner circumferential surface 812 is set in the same way. However, the structure is not limited to the above, and at least one of the step 811A of the bottom surface 811 and the step 812A of the inner circumferential surface 812 may also be formed.

[0137] The structure of Implementation 1 (including variations) can be suitably combined with various structures (including variations) described in the basic structure.

[0138] (Implementation Method 2)

[0139] Regarding the internal meshing planetary gear device 1B of this embodiment (hereinafter also simply referred to as "gear device 1B"), as shown in FIG10, the support structure of crankshaft 7A, crankshaft 7B, and crankshaft 7C differs from that of gear device 1A in Embodiment 1. Hereinafter, common symbols will be used to label the structures that are the same as in Embodiment 1, and descriptions will be omitted as appropriate.

[0140] In the gear assembly 1B of this embodiment, since the multiple (here, three) crankshafts 7A, 7B, and 7C have a common structure including their support structures, the following description will take crankshaft 7A as an example. FIG10 is a schematic cross-sectional view of the main part of the gear assembly 1A (the area corresponding to region Z1 in FIG4). In FIG10, the illustration of the bearing assembly 6 (first main bearing 601 and second main bearing 602) is simplified, and the illustrations of the inner ring 61, outer ring 62, and multiple rolling elements 63 are omitted.

[0141] That is, in the gear device 1B of this embodiment, the retaining ring 83 and the washer 84 are omitted. Furthermore, the limiting member 82 restricts the movement of the crankshaft 7A and the crankshaft bearing 42 toward the bottom surface 811 by contacting not only the crankshaft 7A but also the crankshaft bearing 42 with the bottom surface 822. In short, the limiting member 82 directly restricts the movement of the crankshaft 7A toward the bottom surface 811, as well as the crankshaft bearing 42.

[0142] More specifically, the bottom 822 of the limiting member 82 directly or indirectly (via the retainer 403) restricts the movement of the plurality of rolling elements 402 toward the bottom surface 811. Thus, the structure (retaining ring 83) for restricting the relative movement of the crankshaft bearing 42 relative to the crankshaft 7A is omitted, and the movement of both the crankshaft 7A and the crankshaft bearing 42 toward the bottom surface 811 can be restricted by a relatively simple structure.

[0143] Furthermore, in this embodiment, the bottom surface 811 of the recess 81 has no step 811A, and the bottom surface 811 is formed flat. Similarly, the inner circumferential surface 812 of the recess 81 has no step 812A, and the inner diameter of the inner circumferential surface 812 is set in the same way. However, the structure is not limited to the above, and at least one of the step 811A of the bottom surface 811 and the step 812A of the inner circumferential surface 812 may also be formed.

[0144] The structure of Embodiment 2 (including variations) can be suitably combined with the basic structure or the various structures (including variations) described in Embodiment 1.

[0145] (Summarize)

[0146] As described above, the first-form internal meshing planetary gear assembly (1, 1A, 1B) includes: an internal gear (2), a planetary gear (3), a crankshaft (7A, 7B, 7C), a planet carrier (19), and a limiting member (82). The planetary gear (3) is rotated relative to the internal gear (2) by oscillating. The internal gear (2) has an annular gear body (22) and multiple outer pins (23) that are held in a rotatable state in a plurality of inner circumferential grooves (223) formed by the inner circumferential surface (221) of the gear body (22) and constitute the internal teeth (21). The planetary gear (3) has outer teeth (31) that partially mesh with the internal teeth (21). The crankshaft (7A, 7B, 7C) oscillates the planetary gear (3) by rotating about the axis (Ax2). The planetary carrier (19) has a recess (81) within which the crankshafts (7A, 7B, 7C) are supported for rotation via a crankshaft bearing (42). A limiting member (82) is disposed within the recess (81) of the planetary carrier (19). The limiting member (82) has a bottom (822) facing one end face of the crankshafts (7A, 7B, 7C) axially, and a peripheral wall (823) protruding axially from the outer periphery of the bottom (822) toward the side opposite to the bottom surface (811) of the recess (81). By bringing the crankshafts (7A, 7B, 7C) into contact with the bottom (822), movement of the crankshafts (7A, 7B, 7C) toward the bottom surface (811) is limited. The peripheral wall (823) forms the outer ring (401) of the crankshaft bearing (42).

[0147] According to the described configuration, the bottom (822) of the limiting member (82) integrated with the outer ring (401) of the crankshaft bearing (42) can be used to restrict the axial movement of the crankshaft (7A, 7B, 7C) toward the bottom surface (811) of the recess (81). In this case, it is not necessary to form a clearance portion with a diameter larger than the support surface on the inner circumferential surface (812) of the recess (81), and the shape of the planetary carrier (19) can be easily simplified. Therefore, it has the advantage of easily simplifying the shape of each component.

[0148] The second form of the internal meshing planetary gear device (1, 1A, 1B) is based on the first form, wherein the crankshaft bearing (42) has a plurality of rolling elements (402) and the movement of at least a plurality of rolling elements (402) toward the bottom surface (811) is restricted by the bottom (822).

[0149] Based on the described form, the movement of the crankshaft bearing (42) toward the bottom surface (811) can be restricted by a relatively simple structure.

[0150] The third type of internal meshing planetary gear device (1, 1A, 1B) is based on the first type or the second type, wherein the bottom (822) has a through hole (821) located in the center when viewed from one side in the axial direction and penetrating the bottom (822) in the axial direction.

[0151] According to the described form, lubricant (lubricating oil) can flow through the through hole (821), for example, it is easy to ensure the lubrication of crankshaft bearings (42), etc.

[0152] The fourth type of internal meshing planetary gear device (1, 1A, 1B) is based on any one of the first to third types, and further includes a distribution unit that distributes the rotation of an input gear (501) to multiple crankshafts (7A, 7B, 7C) via multiple crankshaft gears (502A, 502B, 502C). The planetary gear (3) oscillates due to the rotation of the multiple crankshafts (7A, 7B, 7C).

[0153] According to the described configuration, for all of the multiple crankshafts (7A, 7B, 7C), the axial movement of the crankshafts (7A, 7B, 7C) and the crankshaft bearings (42) toward the bottom surface (811) can be restricted.

[0154] The fifth form of the robot joint device (200) includes: an internal meshing planetary gear device (1, 1A, 1B) of any of the first to fourth forms; a first member (201) fixed to the gear body (22); and a second member (202) that rotates relative to the first member (201) as the planetary gear (3) rotates relative to the internal gear (2).

[0155] According to the described form, it has the advantage of easily simplifying the shape of each component.

[0156] The structures of the second to fourth forms are not essential to the internal meshing planetary gear system (1, 1A, 1B) and can be appropriately omitted.

[0157] [Symbol Explanation]

[0158] 1, 1A, 1B: Internal meshing planetary gear assembly / gear assembly 2: Internal gear 3: Planetary gear 5: Eccentric bearing 6: Bearing assembly 7A, 7B, 7C: Crankshaft (eccentric shaft) 10: Housing 18: Input side planetary carrier / planetary carrier 19: Output side planetary carrier / planetary carrier 21: Internal gear 22: Gear body 23: Outer pin 31: External gear 33: Opening 34: Planetary carrier bore 41, 42: Crankshaft bearing 51: Rolling element 61: Inner ring 62: Outer ring 63: Rolling element 71: Shaft core 72: Eccentric part 81: Recess 82: Restricting member 83: Retaining ring 84: Washer 85: Connecting component 100: Actuator 101: Drive source 191: Planetary carrier pin 192: Bore 200: Robot joint assembly 201: First component 202: Second Component 221: Inner circumferential surface / (inner circumferential surface of gear body) 222: Fixing hole 223: Inner circumferential groove 301: First planetary gear 302: Second planetary gear 401: Outer ring 402: Rolling element 403: Retainer 500: Input shaft 501: Input gear 502A, 502B, 502C: Crankshaft gear 601: First main bearing 602: Second main bearing 811: Bottom surface 811A, 812A: Step difference 812: Inner circumferential surface 821: Through hole 822: Bottom 823: Peripheral wall Ax1: Rotation shaft Ax2: Shaft center C0: Center (central shaft) C1, C2: Center Z1: Region ΔL0, ΔL1, ΔL2: Eccentricity / distance

Claims

1. An internal meshing planetary gear device, comprising: An internal gear has an annular gear body and multiple external pins that are able to be held in a rotating state in multiple inner circumferential grooves formed on the inner circumferential surface of the gear body and constitute internal teeth. Planetary gears having external teeth that partially mesh with the internal teeth; The crankshaft, by rotating about its axis, causes the planetary gears to oscillate; A planetary carrier having a recess, and the crankshaft being rotatably supported in the recess by a crankshaft bearing; and A limiting member is disposed within the recess of the planet carrier. By oscillating the planetary gear, the planetary gear rotates relative to the internal gear. The limiting member has a bottom and a circumferential wall, the bottom being axially opposite to one end face of the crankshaft, and the circumferential wall protruding from the outer periphery of the bottom toward the axially opposite side to the bottom face of the recess. By bringing the crankshaft into contact with the bottom, the movement of the crankshaft towards the bottom surface is restricted. The peripheral wall forms the outer ring of the crankshaft bearing.

2. The internal meshing planetary gear device according to claim 1, wherein, The crankshaft bearing has a plurality of rolling elements, and the bottom restricts the movement of at least the plurality of rolling elements toward the bottom surface.

3. The internal meshing planetary gear device according to claim 1 or 2, wherein, The bottom has a through hole located at the center when viewed from one side of the axial direction and extending through the bottom in the axial direction.

4. The internal meshing planetary gear device according to claim 1 or 2, wherein, The internal meshing planetary gear assembly further includes a distribution unit that distributes the rotation of an input gear to a plurality of crankshafts via a plurality of crankshaft gears, the planetary gears oscillating due to the rotation of the plurality of crankshafts.

5. A joint device for a robot, comprising: The internal meshing planetary gear device according to claim 1 or 2; The first component is fixed to the gear body; as well as The second component rotates relative to the first component as the planetary gear rotates relative to the internal gear.

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