JP2024086522A - Gear device and method for manufacturing gear device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear device that can reduce the weight while maintaining the strength, and to provide a method for manufacturing a gear device.

SOLUTION: A gear device includes a first gear and a second gear. The second gear meshes with the first gear and rotates relative to the first gear. The first gear includes: a skeleton part 225; and a coating layer 224 having a specific gravity that is larger than that of the skeleton part 225. At least a slide contact part which slides on the other parts in the skeleton part 225 is covered with the coating layer 224.

SELECTED DRAWING: Figure 11

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates generally to a gear device and a method for manufacturing the gear device, and more specifically to a gear device including a first gear and a second gear that rotates relative to the first gear, and a method for manufacturing the gear device.

As a related art, a gear device (power transmission device) having a sliding portion where a pair of sliding members slide against each other is known (see, for example, Patent Document 1). This gear device is an internally oscillating meshing type planetary gear device having an input shaft, an eccentric body integrated with the input shaft, an external gear that oscillates and rotates due to the eccentric body, an internal gear with internal teeth that internally meshes with the external gear, and a flange body that is disposed axially outside the external gear and is connected to an internal pin that extracts the rotation component of the external gear.

In the above gear device, at least one of the two opposing sliding surfaces of a pair of sliding members, such as the end retaining surfaces of the outer pin that form the internal teeth and the surfaces facing the end retaining surfaces of the outer pin, has a surface roughness formed by a predetermined roughness processing and a carbon-based coating. The carbon-based coating is formed on the surface roughness by adding a metal element.

JP 2009-41747 A

In the above related technology, for example, the base material of the sliding member such as the first gear (internal gear) is made of metal, and a certain thickness is required to perform roughening, making the weight relatively large. This can therefore be an obstacle to reducing the weight of the gear device as a whole.

The objective of this disclosure is to provide a gear device that is easy to reduce weight while maintaining strength, and a method for manufacturing the gear device.

A gear device according to one aspect of the present disclosure includes a first gear and a second gear. The second gear rotates relative to the first gear by meshing with the first gear. The first gear has a skeleton and a coating layer having a higher specific gravity than the skeleton. At least the portion of the skeleton that comes into sliding contact with another component is covered with the coating layer.

A method for manufacturing a gear device according to one aspect of the present disclosure includes a thermal spraying process for forming the coating layer on at least a portion of the framework of the first gear by thermal spraying.

This disclosure makes it possible to provide a gear device that is easy to reduce weight while maintaining strength, and a method for manufacturing the gear device.

FIG. 1 is a perspective view showing a schematic configuration of an actuator including an internal meshing planetary gear device according to a first embodiment. FIG. 2 is a schematic exploded perspective view of the internal meshing planetary gear device as viewed from the output side of the rotary shaft. FIG. 3 is a schematic cross-sectional view of the internal meshing planetary gear device. FIG. 4 is a cross-sectional view taken along line A1-A1 in FIG. 3, showing the internal meshing planetary gear device. FIG. 5A is a perspective view showing a planetary gear of the internal meshing planetary gear device alone. FIG. 5B is a front view showing a planetary gear of the internal meshing planetary gear device alone. FIG. 6A is a perspective view showing the bearing member of the internal meshing planetary gear device alone. FIG. 6B is a front view showing the bearing member of the internal meshing planetary gear device alone. FIG. 7A is a perspective view showing the eccentric shaft of the internal meshing planetary gear device alone. FIG. 7B is a front view showing the eccentric shaft of the internal meshing planetary gear set alone. FIG. 8A is a perspective view showing the support body of the internal meshing planetary gear device alone. FIG. 8B is a front view showing the support body of the internal meshing planetary gear set alone. FIG. 9 is an enlarged view of an area Z1 in FIG. 3, showing the internal meshing planetary gear device. FIG. 10 is a cross-sectional view taken along line B1-B1 in FIG. 3, showing the internal meshing planetary gear device. FIG. 11 is a schematic cross-sectional view showing the internal meshing planetary gear device of the same as above, enlarging the meshing portion between the internal teeth 21 and the external teeth 31 in FIG. FIG. 12 is a schematic cross-sectional view taken along line A1-A1 in FIG. 11, showing the internal meshing planetary gear device. FIG. 13A is a schematic perspective view showing an inner circumferential groove of an internal gear of the internal meshing planetary gear device. FIG. 13B is a schematic perspective view showing an inner circumferential groove of an internal gear of the internal meshing planetary gear device. FIG. 14 is a perspective view showing a schematic configuration of an internal meshing planetary gear device according to the second embodiment. FIG. 15 is a schematic exploded perspective view of the internal meshing planetary gear device as viewed from the input side of the rotary shaft. FIG. 16 is a schematic cross-sectional view of the internal meshing planetary gear device. FIG. 17 is a cross-sectional view showing a schematic configuration of a strain wave gear device according to a first comparative example of the third embodiment. FIG. 18 is a schematic diagram of the above strain wave gear device as viewed from the input side of the rotary shaft. FIG. 19 is a schematic exploded perspective view of the strain wave gear device as viewed from the output side of the rotary shaft. FIG. 20 is a schematic exploded perspective view of the strain wave gear device as viewed from the input side of the rotary shaft.

(Embodiment 1)
(1) Overview An overview of the internally meshing planetary gear device 1 according to this embodiment will be described below with reference to Figures 1 to 3. All of the drawings referred to in this disclosure are schematic diagrams, and the ratios of sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios. For example, the tooth shapes, dimensions, number of teeth, etc. of the internal teeth 21 and external teeth 31 in Figures 1 to 3 are merely shown schematically for the purpose of explanation, and are not intended to be limited to the shapes shown in the drawings.

The internally meshing planetary gear device 1 (hereinafter, simply referred to as "gear device 1") according to this embodiment is a gear device including an internal gear 2, a planetary gear 3, and a plurality of internal pins 4. In this gear device 1, the planetary gear 3 is arranged inside the annular internal gear 2, and further, an eccentric bearing 5 is arranged inside the planetary gear 3. The eccentric bearing 5 has an eccentric inner ring 51 and an eccentric outer ring 52, and the planetary gear 3 is oscillated by the eccentric inner ring 51 rotating (eccentric motion) around a rotation axis Ax1 (see FIG. 3) shifted from the center C1 (see FIG. 3) of the eccentric inner ring 51. The eccentric inner ring 51 rotates (eccentric motion) around the rotation axis Ax1, for example, by the rotation of the eccentric shaft 7 inserted into the eccentric inner ring 51. The internally meshing planetary gear device 1 further includes a bearing member 6 having an outer ring 62 and an inner ring 61. The inner ring 61 is disposed inside the outer ring 62 and is supported so as to be rotatable relative to the outer ring 62.

The internal gear 2 has internal teeth 21 and is fixed to the outer ring 62. In particular, in this embodiment, the internal gear 2 has an annular gear body 22 and multiple outer pins 23. The multiple outer pins 23 are held on the inner circumferential surface 221 of the gear body 22 in a rotatable state, forming the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. In other words, the planetary gear 3 is inscribed with the internal gear 2 inside the internal gear 2, and a part of the external teeth 31 is meshed with a part of the internal teeth 21. In this state, when the eccentric shaft 7 rotates, the planetary gear 3 oscillates, and the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2, and a relative rotation according to the difference in the number of teeth between the planetary gear 3 and the internal gear 2 occurs between both gears (the internal gear 2 and the planetary gear 3). If the internal gear 2 is fixed, the planetary gear 3 rotates (spins) in response to the relative rotation of the two gears. As a result, the planetary gear 3 produces a rotational output that is reduced at a relatively high reduction ratio according to the difference in the number of teeth between the two gears.

This type of gear device 1 is used to extract the rotation equivalent to the rotation component of the planetary gear 3 as the rotation of the output shaft integrated with the inner ring 61 of the bearing member 6, for example. As a result, the gear device 1 functions as a gear device with a relatively high reduction ratio, with the eccentric shaft 7 as the input side and the output shaft as the output side. Therefore, in the gear device 1 according to this embodiment, in order to transmit the rotation equivalent to the rotation component of the planetary gear 3 to the inner ring 61 of the bearing member 6, the planetary gear 3 and the inner ring 61 are connected by a plurality of inner pins 4. The plurality of inner pins 4 rotate relative to the internal gear 2 while revolving within the respective loose fitting holes 32, while being inserted into the respective loose fitting holes 32 formed in the planetary gear 3. In other words, the loose fitting holes 32 have a larger diameter than the inner pins 4, and the inner pins 4 are movable so as to revolve within the loose fitting holes 32 while being inserted into the loose fitting holes 32. The oscillation component of the planetary gear 3, that is, the orbital component of the planetary gear 3, is absorbed by the loose fit between the loose fit holes 32 of the planetary gear 3 and the inner pin 4. In other words, the oscillation component of the planetary gear 3 is absorbed by the multiple inner pins 4 moving so as to revolve within the multiple loose fit holes 32. Therefore, the rotation (rotation component) of the planetary gear 3, excluding the oscillation component (orbital component) of the planetary gear 3, is transmitted to the inner ring 61 of the bearing member 6 by the multiple inner pins 4.

In this type of gear device 1, the rotation of the planetary gear 3 is transmitted to the multiple inner pins 4 while the inner pin 4 revolves within the loose fitting hole 32 of the planetary gear 3. Therefore, as a first related technique, it is known to use an inner roller that is attached to the inner pin 4 and can rotate around the inner pin 4. That is, in the first related technique, the inner pin 4 is held in a pressed state against the inner ring 61 (or a carrier integrated with the inner ring 61), and when the inner pin 4 revolves within the loose fitting hole 32, the inner pin 4 slides against the inner circumferential surface 321 of the loose fitting hole 32. Therefore, as the first related technique, an inner roller is used to reduce losses due to frictional resistance between the inner circumferential surface 321 of the loose fitting hole 32 and the inner pin 4. However, if an inner roller is provided as in the first related technique, the loose fitting hole 32 needs to have a diameter that allows the inner pin 4 with the inner roller to revolve, making it difficult to reduce the size of the loose fitting hole 32. If it is difficult to reduce the size of the loose fitting hole 32, this will hinder the miniaturization (particularly the diameter reduction) of the planetary gear 3, and ultimately hinder the miniaturization of the entire gear device 1. The gear device 1 according to this embodiment has the following configuration, making it possible to provide an internal meshing planetary gear device 1 that is easy to reduce in size.

That is, the gear device 1 according to this embodiment includes a bearing member 6, an internal gear 2, a planetary gear 3, and a number of internal pins 4, as shown in Figs. 1 to 3. The bearing member 6 has an outer ring 62 and an inner ring 61 arranged inside the outer ring 62. The inner ring 61 is supported so as to be rotatable relative to the outer ring 62. The internal gear 2 has internal teeth 21 and is fixed to the outer ring 62. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The multiple internal pins 4 are inserted into multiple loose fitting holes 32 formed in the planetary gear 3, respectively, and rotate relative to the internal gear 2 while revolving within the loose fitting holes 32. Here, each of the multiple internal pins 4 is held by the inner ring 61 in a rotatable state. Furthermore, at least a portion of each of the multiple internal pins 4 is arranged at the same position as the bearing member 6 in the axial direction of the bearing member 6.

According to this aspect, each of the multiple inner pins 4 is held by the inner ring 61 in a rotatable state, so that when the inner pin 4 revolves within the loose fitting hole 32, the inner pin 4 itself can rotate. Therefore, even if an inner roller that is attached to the inner pin 4 and can rotate around the inner pin 4 is not used, the loss due to friction resistance between the inner peripheral surface 321 of the loose fitting hole 32 and the inner pin 4 can be reduced. Therefore, the gear device 1 according to this embodiment has the advantage that the inner roller is not essential and it is easy to make it compact. Moreover, since at least a portion of each of the multiple inner pins 4 is disposed at the same position as the bearing member 6 in the axial direction of the bearing member 6, the dimensions of the gear device 1 in the axial direction of the bearing member 6 can be kept small. In other words, compared to a configuration in which the bearing member 6 and the inner pin 4 are arranged (opposed) in the axial direction of the bearing member 6, the gear device 1 according to this embodiment can reduce the dimensions of the gear device 1 in the axial direction, which can contribute to further miniaturization (thinning) of the gear device 1.

Furthermore, if the dimensions of the planetary gear 3 are the same as those in the first related technology, it is possible to increase the number of inner pins 4 to smooth the transmission of rotation or to make the inner pins 4 thicker to improve strength, compared to the first related technology.

In addition, in this type of gear device 1, since the inner pin 4 needs to revolve within the loose fitting hole 32 of the planetary gear 3, as a second related technology, the multiple inner pins 4 may be held only by the inner ring 61 (or a carrier integrated with the inner ring 61). According to the second related technology, it is difficult to improve the accuracy of centering the multiple inner pins 4, and centering failure may lead to problems such as vibration generation and reduced transmission efficiency. In other words, the multiple inner pins 4 transmit the rotation component of the planetary gear 3 to the inner ring 61 of the bearing member 6 by rotating relative to the internal gear 2 while revolving within the loose fitting hole 32. At this time, if the centering accuracy of the multiple inner pins 4 is insufficient and the rotation axis of the multiple inner pins 4 is misaligned or tilted with respect to the rotation axis of the inner ring 61, a centering failure state will occur, which may lead to problems such as vibration generation and reduced transmission efficiency. The gear device 1 according to this embodiment has the following configuration, making it possible to provide an internally meshing planetary gear device 1 that is less susceptible to problems caused by misalignment of multiple inner pins 4.

That is, the gear device 1 according to this embodiment includes an internal gear 2, a planetary gear 3, multiple internal pins 4, and a support 8, as shown in Figs. 1 to 3. The internal gear 2 has an annular gear body 22 and multiple external pins 23. The multiple external pins 23 are held on the inner peripheral surface 221 of the gear body 22 in a rotatable state to form the internal teeth 21. The planetary gear 3 has external teeth 31 that partially mesh with the internal teeth 21. The multiple internal pins 4 are inserted into multiple loose fitting holes 32 formed in the planetary gear 3, and rotate relative to the gear body 22 while revolving within the loose fitting holes 32. The support 8 is annular and supports the multiple internal pins 4. Here, the position of the support 8 is restricted by contacting the outer peripheral surface 81 with the multiple external pins 23.

According to this aspect, the multiple inner pins 4 are supported by the annular support 8, so that the multiple inner pins 4 are bundled by the support 8, and the relative deviation and inclination of the multiple inner pins 4 is suppressed. Moreover, the outer peripheral surface 81 of the support 8 contacts the multiple outer pins 23, thereby regulating the position of the support 8. In short, the support 8 is centered by the multiple outer pins 23, and as a result, the multiple inner pins 4 supported by the support 8 are also centered by the multiple outer pins 23. Therefore, according to the gear device 1 of this embodiment, it is easy to improve the accuracy of centering the multiple inner pins 4, and there is an advantage that malfunctions caused by poor centering of the multiple inner pins 4 are less likely to occur.

As shown in FIG. 1, the gear device 1 according to this embodiment constitutes an actuator 100 together with a driving source 101. In other words, the actuator 100 according to this embodiment includes the gear device 1 and a driving source 101. The driving source 101 generates a driving force for oscillating the planetary gear 3. Specifically, the driving source 101 oscillates the planetary gear 3 by rotating the eccentric shaft 7 about the rotation axis Ax1.

(2) Definition In the present disclosure, "annular" means a ring-like shape that forms an enclosed space (region) at least in a plan view, and is not limited to a circular shape (annular shape) such as a perfect circle in a plan view, but may be, for example, an elliptical shape, a polygonal shape, etc. Furthermore, even if the shape has a bottom, such as a cup shape, it is included in the "annular" shape as long as the peripheral wall is annular.

In this disclosure, "loose fit" means being fitted with play (gap), and the loose fit hole 32 is a hole into which the inner pin 4 is loosely fitted. In other words, the inner pin 4 is inserted into the loose fit hole 32 with a spatial margin (gap) secured between the inner circumferential surface 321 of the loose fit hole 32. In other words, the diameter of at least the portion of the inner pin 4 inserted into the loose fit hole 32 is smaller (thinner) than the diameter of the loose fit hole 32. Therefore, the inner pin 4 can move within the loose fit hole 32 when inserted into the loose fit hole 32, that is, it can move relatively to the center of the loose fit hole 32. Therefore, the inner pin 4 can revolve within the loose fit hole 32. However, it is not essential that a gap as a cavity is secured between the inner circumferential surface 321 of the loose fit hole 32 and the inner pin 4, and for example, this gap may be filled with a fluid such as a liquid.

In this disclosure, "revolution" means that an object revolves around an axis of rotation other than the central axis that passes through the center (center of gravity) of the object, and when an object revolves, the center of the object moves along an orbital path centered on the axis of rotation. Therefore, for example, when an object rotates around an eccentric axis that is parallel to the central axis that passes through the center (center of gravity) of the object, the object revolves around the eccentric axis as the axis of rotation. As an example, the inner pin 4 revolves within the loose fitting hole 32, revolving around the axis of rotation that passes through the center of the loose fitting hole 32.

In addition, in this disclosure, one side of the rotating shaft Ax1 (left side in FIG. 3) may be referred to as the "input side," and the other side of the rotating shaft Ax1 (right side in FIG. 3) may be referred to as the "output side." In the example of FIG. 3, rotation is imparted to the rotating body (eccentric inner ring 51) from the "input side" of the rotating shaft Ax1, and rotation of the multiple inner pins 4 (inner ring 61) is extracted from the "output side" of the rotating shaft Ax1. However, the "input side" and "output side" are merely labels added for the purpose of explanation, and are not intended to limit the positional relationship between the input and output as viewed from the gear device 1.

In this disclosure, the term "rotation axis" refers to a virtual axis (straight line) that is the center of rotational motion of a rotating body. In other words, the rotation axis Ax1 is a virtual axis that does not have a physical entity. The eccentric inner ring 51 rotates around the rotation axis Ax1.

In this disclosure, "internal teeth" and "external teeth" do not refer to individual "tooths," but rather to a collection (group) of multiple "teeth." In other words, the internal teeth 21 of the internal gear 2 are made up of a collection of multiple teeth arranged on the inner circumferential surface 221 of the internal gear 2 (gear body 22). Similarly, the external teeth 31 of the planetary gear 3 are made up of a collection of multiple teeth arranged on the outer circumferential surface of the planetary gear 3.

(3) Configuration Hereinafter, a detailed configuration of the internal meshing planetary gear device 1 according to this embodiment will be described with reference to FIGS. 1 to 8B.

Figure 1 is a perspective view showing the schematic configuration of an actuator 100 including a gear device 1. In Figure 1, a driving source 101 is shown in schematic form. Figure 2 is a schematic exploded perspective view of the gear device 1 as viewed from the output side of the rotation axis Ax1. Figure 3 is a schematic cross-sectional view of the gear device 1. Figure 4 is a cross-sectional view taken along the line A1-A1 in Figure 3. However, in Figure 4, hatching is omitted for parts other than the eccentric shaft 7, even in cross-section. Furthermore, in Figure 4, the inner peripheral surface 221 of the gear body 22 is omitted. Figures 5A and 5B are perspective and front views showing the planetary gear 3 alone. Figures 6A and 6B are perspective and front views showing the bearing member 6 alone. Figures 7A and 7B are perspective and front views showing the eccentric shaft 7 alone. Figures 8A and 8B are perspective and front views showing the support body 8 alone.

(3.1) Overall Configuration As shown in Figs. 1 to 3, the gear device 1 according to this embodiment includes an internal gear 2, a planetary gear 3, a plurality of inner pins 4, an eccentric bearing 5, a bearing member 6, an eccentric shaft 7, and a support 8. In this embodiment, the gear device 1 further includes a first bearing 91, a second bearing 92, and a case 10. In this embodiment, the materials of the components of the gear device 1, such as the internal gear 2, the planetary gear 3, the plurality of inner pins 4, the eccentric bearing 5, the bearing member 6, the eccentric shaft 7, and the support 8, are metals such as stainless steel, cast iron, carbon steel for mechanical construction, chromium molybdenum steel, phosphorus bronze, or aluminum bronze, or light metals such as aluminum or titanium. The metal (including light metals) referred to here includes metals that have been subjected to surface treatment such as nitriding. In this embodiment, the gear body 22 of the internal gear 2 is made of aluminum, for example.

In addition, in this embodiment, an internal planetary gear device using a trochoidal tooth profile is illustrated as an example of the gear device 1. In other words, the gear device 1 according to this embodiment includes an internal planetary gear 3 having a trochoidal curved tooth profile.

In addition, in this embodiment, as an example, the gear device 1 is used in a state where the gear body 22 of the internal gear 2 is fixed to a fixed member such as the case 10 together with the outer ring 62 of the bearing member 6. As a result, the planetary gear 3 rotates relative to the fixed member (such as the case 10) in conjunction with the relative rotation between the internal gear 2 and the planetary gear 3.

Furthermore, in this embodiment, when the gear device 1 is used in the actuator 100, a rotational force is applied as an input to the eccentric shaft 7, and a rotational force is output from the output shaft integrated with the inner ring 61 of the bearing member 6. In other words, the gear device 1 operates with the rotation of the eccentric shaft 7 as the input rotation and the rotation of the output shaft integrated with the inner ring 61 as the output rotation. As a result, the gear device 1 can obtain an output rotation that is reduced at a relatively high reduction ratio compared to the input rotation.

The driving source 101 is a power generating source such as a motor (electric motor). The power generated by the driving source 101 is transmitted to the eccentric shaft 7 in the gear device 1. Specifically, the driving source 101 is connected to the eccentric shaft 7 via an input shaft, and the power generated by the driving source 101 is transmitted to the eccentric shaft 7 via the input shaft. This allows the driving source 101 to rotate the eccentric shaft 7.

Furthermore, in the gear device 1 according to this embodiment, as shown in FIG. 3, the input side rotation axis Ax1 and the output side rotation axis Ax1 are on the same straight line. In other words, the input side rotation axis Ax1 and the output side rotation axis Ax1 are coaxial. Here, the input side rotation axis Ax1 is the rotation center of the eccentric shaft 7 to which the input rotation is applied, and the output side rotation axis Ax1 is the rotation center of the inner ring 61 (and the output shaft) that generates the output rotation. In other words, in the gear device 1, an output rotation that is reduced in speed at a relatively high reduction ratio compared to the input rotation on the same axis is obtained.

The internal gear 2 is an annular part having internal teeth 21, as shown in FIG. 4. In this embodiment, the internal gear 2 has an annular shape, with at least the inner peripheral surface being a perfect circle in a plan view. The internal teeth 21 are formed along the circumferential direction of the internal gear 2 on the inner peripheral surface of the annular internal gear 2. The multiple teeth constituting the internal teeth 21 all have the same shape and are provided at equal pitch over the entire circumferential area of the inner peripheral surface of the internal gear 2. In other words, the pitch circle of the internal teeth 21 is a perfect circle in a plan view. The center of the pitch circle of the internal teeth 21 is on the rotation axis Ax1. The internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. The tooth traces of the internal teeth 21 are all parallel to the rotation axis Ax1. The dimension of the internal teeth 21 in the tooth trace direction is slightly smaller than the thickness direction of the internal gear 2.

Here, as described above, the internal gear 2 has an annular (circular) gear body 22 and a plurality of outer pins 23. The plurality of outer pins 23 are held on the inner circumferential surface 221 of the gear body 22 in a rotatable state to form the internal teeth 21. In other words, the plurality of outer pins 23 function as a plurality of teeth that form the internal teeth 21. Specifically, as shown in FIG. 2, the inner circumferential surface 221 of the gear body 22 has a plurality of inner circumferential grooves 223 formed over the entire circumferential area. All of the inner circumferential grooves 223 have the same shape and are provided at equal pitches. All of the inner circumferential grooves 223 are parallel to the rotation axis Ax1 and are formed over the entire length of the gear body 22 in the thickness direction. The plurality of outer pins 23 are combined with the gear body 22 so as to fit into the plurality of inner circumferential grooves 223. Each of the plurality of outer pins 23 is held in a rotatable state within the inner circumferential groove 223. In addition, the gear body 22 (together with the outer ring 62) is fixed to the case 10. Therefore, the gear body 22 has multiple fixing holes 222 for fixing.

As shown in FIG. 4, the planetary gear 3 is an annular part having external teeth 31. In this embodiment, the planetary gear 3 has an annular shape in which at least the outer peripheral surface is a perfect circle in a plan view. The outer peripheral surface of the annular planetary gear 3 has external teeth 31 formed along the circumferential direction of the planetary gear 3. The multiple teeth constituting the external teeth 31 all have the same shape and are provided at equal pitch over the entire circumferential area of the outer peripheral surface of the planetary gear 3. In other words, the pitch circle of the external teeth 31 is a perfect circle in a plan view. The center C1 of the pitch circle of the external teeth 31 is shifted from the rotation axis Ax1 by a distance ΔL (see FIG. 4). The planetary gear 3 also has a predetermined thickness in the direction of the rotation axis Ax1. All of the external teeth 31 are formed over the entire length of the planetary gear 3 in the thickness direction. All of the tooth traces of the external teeth 31 are parallel to the rotation axis Ax1. In the planetary gear 3, unlike the internal gear 2, the external teeth 31 are formed integrally with the main body of the planetary gear 3 from a single metal member.

Here, the eccentric body bearing 5 and the eccentric shaft 7 are combined with the planetary gear 3. That is, the planetary gear 3 has an opening 33 that opens in a circular shape. The opening 33 is a hole that penetrates the planetary gear 3 along the thickness direction. In a plan view, the center of the opening 33 and the center of the planetary gear 3 coincide with each other, and the inner peripheral surface of the opening 33 (the inner peripheral surface of the planetary gear 3) and the pitch circle of the external teeth 31 are concentric. The opening 33 of the planetary gear 3 accommodates the eccentric body bearing 5. Furthermore, the eccentric shaft 7 is inserted into the eccentric body bearing 5 (the eccentric inner ring 51), so that the eccentric body bearing 5 and the eccentric shaft 7 are combined with the planetary gear 3. When the eccentric shaft 7 rotates with the eccentric body bearing 5 and the eccentric shaft 7 combined with the planetary gear 3, the planetary gear 3 oscillates around the rotation axis Ax1.

The planetary gear 3 configured in this manner is disposed inside the internal gear 2. In a plan view, the planetary gear 3 is formed to be one size smaller than the internal gear 2, and the planetary gear 3 can oscillate inside the internal gear 2 when combined with the internal gear 2. Here, external teeth 31 are formed on the outer peripheral surface of the planetary gear 3, and internal teeth 21 are formed on the inner peripheral surface of the internal gear 2. Therefore, when the planetary gear 3 is disposed inside the internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

Furthermore, the pitch circle of the external teeth 31 is one size smaller than the pitch circle of the internal teeth 21. And, when the planetary gear 3 is inscribed in the internal gear 2, the center C1 of the pitch circle of the external teeth 31 is located at a position shifted by a distance ΔL (see FIG. 4) from the center of the pitch circle of the internal teeth 21 (rotation axis Ax1). Therefore, at least a part of the external teeth 31 faces the internal teeth 21 through a gap, and they do not mesh with each other in the entire 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 with each other. In other words, by oscillating the planetary gear 3 around the rotation axis Ax1, some of the teeth that make up the external teeth 31 mesh with some of the teeth that make up the internal teeth 21, as shown in FIG. 4. As a result, in the gear device 1, it is possible to mesh some of the external teeth 31 with some of the internal teeth 21.

Here, the number of teeth of the internal teeth 21 of the internal gear 2 is N (N is a positive integer) more than the number of teeth of the external teeth 31 of the planetary gear 3. In this embodiment, as an example, N is "1", and the number of teeth (of the external teeth 31) of the planetary gear 3 is "1" more than the number of teeth (of the internal teeth 21) of the internal gear 2. Such a 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 this embodiment, as an example, the thickness of the planetary gear 3 is smaller than the thickness of the gear body 22 in the internal gear 2. Furthermore, the dimension of the external teeth 31 in the tooth trace direction (direction parallel to the rotation axis Ax1) is smaller than the dimension of the internal teeth 21 in the tooth trace direction (direction parallel to the rotation axis Ax1). In other words, in the direction parallel to the rotation axis Ax1, the external teeth 31 are contained within the range of the tooth trace of the internal teeth 21.

In this embodiment, as described above, the rotation equivalent to the rotation component of the planetary gear 3 is taken out as the rotation (output rotation) of the output shaft integrated with the inner ring 61 of the bearing member 6. Therefore, the planetary gear 3 is connected to the inner ring 61 by a plurality of inner pins 4. As shown in FIG. 5A and FIG. 5B, the planetary gear 3 has a plurality of loose fitting holes 32 for inserting a plurality of inner pins 4. The loose fitting holes 32 are provided in the same number as the inner pins 4, and in this embodiment, as an example, 18 loose fitting holes 32 and 18 inner pins 4 are provided. Each of the multiple loose fitting holes 32 is a hole that opens in a circular shape and penetrates the planetary gear 3 along the thickness direction. The multiple (here, 18) loose fitting holes 32 are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the opening 33.

The multiple inner pins 4 are components that connect the planetary gear 3 and the inner ring 61 of the bearing member 6. Each of the multiple inner pins 4 is formed in a cylindrical shape. The diameter and length of the multiple inner pins 4 are the same for all of the multiple inner pins 4. The diameter of the inner pin 4 is one size smaller than the diameter of the loose fitting hole 32. As a result, the inner pin 4 is inserted into the loose fitting hole 32 with a spatial margin (gap) secured between the inner circumferential surface 321 of the loose fitting hole 32 (see FIG. 4).

The bearing member 6 has an outer ring 62 and an inner ring 61, and is a component for extracting the output of the gear device 1 as the rotation of the inner ring 61 relative to the outer ring 62. In addition to the outer ring 62 and the inner ring 61, the bearing member 6 also has a number of rolling elements 63 (see FIG. 3).

As shown in Figures 6A and 6B, the outer ring 62 and the inner ring 61 are both annular components. The outer ring 62 and the inner ring 61 both have an annular shape that is a perfect circle in a plan view. The inner ring 61 is one size smaller than the outer ring 62 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 inner ring 61 has a number of retaining holes 611 into which the inner pins 4 are respectively inserted. The number of retaining holes 611 is the same as the number of inner pins 4, and in this embodiment, as an example, 18 retaining holes 611 are provided. As shown in Figures 6A and 6B, each of the retaining holes 611 has a circular opening and is a hole that penetrates the inner ring 61 in the thickness direction. The multiple retaining holes 611 (here, 18) are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the outer periphery of the inner ring 61. The diameter of the retaining hole 611 is equal to or greater than the diameter of the inner pin 4 and smaller than the diameter of the loose fitting hole 32.

Furthermore, the inner ring 61 is integrated with the output shaft, and the rotation of the inner ring 61 is taken out as the rotation of the output shaft. Therefore, the inner ring 61 is formed with a plurality of output side mounting holes 612 (see FIG. 2) for mounting the output shaft. In this embodiment, the plurality of output side mounting holes 612 are located inside the plurality of retaining holes 611 and are arranged on a virtual circle concentric with the outer periphery of the inner ring 61.

The outer ring 62 is fixed to a fixed member such as the case 10 together with the gear body 22 of the internal gear 2. For this reason, the outer ring 62 is formed with a plurality of through holes 621 for fixing. Specifically, as shown in FIG. 3, the outer ring 62 is fixed to the case 10 by fixing screws (bolts) 60 that pass through the through holes 621 and the fixing holes 222 of the gear body 22 with the gear body 22 sandwiched between the outer ring 62 and the case 10.

The 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 a line in the circumferential direction of the outer ring 62. The multiple rolling elements 63 are all metal parts of the same shape, and are provided at equal pitches over the entire circumferential area of the outer ring 62.

In this embodiment, as an example, the bearing member 6 is a cross roller bearing. That is, the bearing member 6 has cylindrical rollers as rolling elements 63. The axis of the cylindrical rolling elements 63 is inclined at 45 degrees with respect to a plane perpendicular to the rotation axis Ax1, and perpendicular to the outer periphery of the inner ring 61. Furthermore, a pair of rolling elements 63 adjacent to each other in the circumferential direction of the inner ring 61 are arranged so that their axial directions are perpendicular to each other. The bearing member 6 made of such a cross roller bearing is easily subjected to radial loads, thrust loads (directions along the rotation axis Ax1), and bending forces (bending moment loads) against the rotation axis Ax1. Moreover, a single bearing member 6 can withstand these three types of loads and ensure the necessary rigidity.

As shown in Figures 7A and 7B, the eccentric shaft 7 is a cylindrical part. The eccentric shaft 7 has an axial center portion 71 and an eccentric portion 72. The axial center portion 71 has a cylindrical shape with at least the outer peripheral surface being a perfect circle in a plan view. The center (central axis) of the axial center portion 71 coincides with the rotation axis Ax1. The eccentric portion 72 has a disk shape with at least the outer peripheral surface being a perfect circle in a plan view. The center (central axis) of the eccentric portion 72 coincides with the center C1 shifted from the rotation axis Ax1. Here, the distance ΔL (see Figure 7B) between the rotation axis Ax1 and the center C1 is the eccentricity of the eccentric portion 72 with respect to the axial center portion 71. The eccentric portion 72 has a flange shape that protrudes from the outer peripheral surface of the axial center portion 71 over the entire circumference at the center of the longitudinal direction (axial direction) of the axial center portion 71. According to the above-described configuration, the eccentric shaft 7 rotates (spins) the axial center portion 71 about the rotation axis Ax1, causing the eccentric portion 72 to perform eccentric motion.

In this embodiment, the shaft center portion 71 and the eccentric portion 72 are integrally formed from a single metal member, thereby realizing a seamless eccentric shaft 7. The eccentric shaft 7 having this shape is combined with the planetary gear 3 together with the eccentric body bearing 5. Therefore, when the eccentric shaft 7 rotates with the eccentric body bearing 5 and the eccentric shaft 7 combined with the planetary gear 3, the planetary gear 3 oscillates around the rotation axis Ax1.

Furthermore, the eccentric shaft 7 has a through hole 73 that passes through the shaft center portion 71 in the axial direction (longitudinal direction). The through hole 73 opens in a circular shape on both axial end faces of the shaft center portion 71. The center (central axis) of the through hole 73 coincides with the rotation axis Ax1. For example, cables such as power lines and signal lines can be passed through the through hole 73.

In addition, in this embodiment, a rotational force is applied as an input from the driving source 101 to the eccentric shaft 7. Therefore, the eccentric shaft 7 is formed with a plurality of input side mounting holes 74 (see Figures 7A and 7B) for mounting an input shaft connected to the driving source 101. In this embodiment, the plurality of input side mounting holes 74 are arranged on a virtual circle concentric with the through hole 73 around the through hole 73 on one end face in the axial direction of the shaft center portion 71.

The eccentric bearing 5 has an eccentric outer ring 52 and an eccentric inner ring 51, and is a component that absorbs the rotational component of the rotation of the eccentric shaft 7 and transmits only the rotation of the eccentric shaft 7 excluding the rotational component of the eccentric shaft 7, that is, only the oscillation component (revolution component) of the eccentric shaft 7, to the planetary gear 3. In addition to the eccentric outer ring 52 and the eccentric inner ring 51, the eccentric bearing 5 has multiple rolling elements 53 (see Figure 3).

The eccentric outer ring 52 and the eccentric inner ring 51 are both annular parts. The eccentric outer ring 52 and the eccentric inner ring 51 both have an annular shape that is a perfect circle in a plan view. The eccentric inner ring 51 is one size smaller than the eccentric outer ring 52 and is disposed inside the eccentric outer ring 52. Here, since the inner diameter of the eccentric outer ring 52 is larger than the outer diameter of the eccentric inner ring 51, a gap is generated between the inner peripheral surface of the eccentric outer ring 52 and the outer peripheral surface of the eccentric inner ring 51.

The multiple rolling elements 53 are arranged in the gap between the eccentric outer ring 52 and the eccentric inner ring 51. The multiple rolling elements 53 are arranged in a line in the circumferential direction of the eccentric outer ring 52. The multiple rolling elements 53 are all metal parts of the same shape, and are provided at equal pitches over the entire circumferential area of the eccentric outer ring 52. In this embodiment, as an example, the eccentric bearing 5 is a deep groove ball bearing that uses balls as the rolling elements 53.

Here, the inner diameter of the eccentric inner ring 51 is equal to the outer diameter of the eccentric portion 72 of the eccentric shaft 7. The eccentric bearing 5 is combined with the eccentric shaft 7 with the eccentric portion 72 of the eccentric shaft 7 inserted into the eccentric inner ring 51. The outer diameter of the eccentric outer ring 52 is equal to the inner diameter (diameter) of the opening 33 of the planetary gear 3. The eccentric bearing 5 is combined with the planetary gear 3 with the eccentric outer ring 52 fitted into the opening 33 of the planetary gear 3. In other words, the opening 33 of the planetary gear 3 accommodates the eccentric bearing 5 attached to the eccentric portion 72 of the eccentric shaft 7.

In addition, in this embodiment, as an example, the width dimension (direction parallel to the rotation axis Ax1) of the eccentric inner ring 51 in the eccentric bearing 5 is approximately the same as the thickness of the eccentric portion 72 of the eccentric shaft 7. The width dimension (direction parallel to the rotation axis Ax1) of the eccentric outer ring 52 is slightly smaller than the width dimension of the eccentric inner ring 51. Furthermore, the width dimension of the eccentric outer ring 52 is larger than the thickness of the planetary gear 3. Therefore, in the direction parallel to the rotation axis Ax1, the planetary gear 3 fits within the range of the eccentric bearing 5. On the other hand, the width dimension of the eccentric outer ring 52 is smaller than the dimension in the tooth trace direction of the internal teeth 21 (direction parallel to the rotation axis Ax1). Therefore, in the direction parallel to the rotation axis Ax1, the eccentric bearing 5 fits within the range of the internal gear 2.

When the eccentric shaft 7 rotates with the eccentric bearing 5 and the eccentric shaft 7 combined with the planetary gear 3, the eccentric inner ring 51 rotates (eccentrically moves) around the rotation axis Ax1 that is offset from the center C1 of the eccentric inner ring 51 in the eccentric bearing 5. At this time, the rotation component of the eccentric shaft 7 is absorbed by the eccentric bearing 5. Therefore, only the rotation of the eccentric shaft 7 excluding the rotation component of the eccentric shaft 7, that is, only the oscillation component (revolution component) of the eccentric shaft 7 is transmitted to the planetary gear 3 by the eccentric bearing 5. Therefore, when the eccentric shaft 7 rotates with the eccentric bearing 5 and the eccentric shaft 7 combined with the planetary gear 3, the planetary gear 3 oscillates around the rotation axis Ax1.

As shown in Figs. 8A and 8B, the support 8 is an annular component that supports multiple inner pins 4. The support 8 has multiple support holes 82 into which the multiple inner pins 4 are inserted. The support holes 82 are provided in the same number as the inner pins 4, and in this embodiment, as an example, 18 support holes 82 are provided. As shown in Figs. 8A and 8B, each of the multiple support holes 82 opens in a circular shape and penetrates the support 8 in the thickness direction. The multiple (here, 18) support holes 82 are arranged at equal intervals in the circumferential direction on a virtual circle concentric with the outer circumferential surface 81 of the support 8. The diameter of the support hole 82 is equal to or greater than the diameter of the inner pin 4 and smaller than the diameter of the loose fitting hole 32. In this embodiment, as an example, the diameter of the support hole 82 is equal to the diameter of the retaining hole 611 formed in the inner ring 61.

As shown in FIG. 3, the support 8 is disposed so as to face the planetary gear 3 from one side (input side) of the rotation axis Ax1. The inner pins 4 are inserted into the support holes 82, and the support 8 functions to bundle the inner pins 4. Furthermore, the position of the support 8 is restricted by contacting the outer peripheral surface 81 with the outer pins 23. This allows the support 8 to be centered by the outer pins 23, and as a result, the inner pins 4 supported by the support 8 are also centered by the outer pins 23. The support 8 will be described in detail in the "(3.3) Support" section.

The first bearing 91 and the second bearing 92 are each mounted on the axial center portion 71 of the eccentric shaft 7. Specifically, as shown in FIG. 3, the first bearing 91 and the second bearing 92 are mounted on both sides of the eccentric portion 72 in the axial center portion 71 so as to sandwich the eccentric portion 72 in a direction parallel to the rotation axis Ax1. The first bearing 91 is disposed on the input side of the rotation axis Ax1 as viewed from the eccentric portion 72. The second bearing 92 is disposed on the output side of the rotation axis Ax1 as viewed from the eccentric portion 72. The first bearing 91 holds the eccentric shaft 7 rotatably relative to the case 10. The second bearing 92 holds the eccentric shaft 7 rotatably relative to the inner ring 61 of the bearing member 6. As a result, the axial center portion 71 of the eccentric shaft 7 is rotatably held at two locations on both sides of the eccentric portion 72 in a direction parallel to the rotation axis Ax1.

The case 10 is cylindrical and has a flange portion 11 on the output side of the rotating shaft Ax1. The flange portion 11 has a plurality of mounting holes 111 for fixing the case 10 itself. A bearing hole 12 is formed in the end face of the case 10 on the output side of the rotating shaft Ax1. The bearing hole 12 has a circular opening. The first bearing 91 is attached to the case 10 by fitting it into the bearing hole 12.

In addition, multiple screw holes 13 are formed around the bearing hole 12 on the output side end face of the rotation axis Ax1 in the case 10. The multiple screw holes 13 are used to fix the gear body 22 of the internal gear 2 and the outer ring 62 of the bearing member 6 to the case 10. Specifically, the fixing screw 60 is passed through the through hole 621 of the outer ring 62 and the fixing hole 222 of the gear body 22 and tightened into the screw hole 13, thereby fixing the gear body 22 and the outer ring 62 to the case 10.

As shown in FIG. 3, the gear device 1 according to this embodiment further includes a plurality of oil seals 14, 15, 16, etc. The oil seal 14 is attached to the input side end of the rotating shaft Ax1 of the eccentric shaft 7, and closes the gap between the case 10 and the eccentric shaft 7 (shaft center portion 71). The oil seal 15 is attached to the output side end of the rotating shaft Ax1 of the eccentric shaft 7, and closes the gap between the inner ring 61 and the eccentric shaft 7 (shaft center portion 71). The oil seal 16 is attached to the output side end face of the rotating shaft Ax1 of the bearing member 6, and closes the gap between the inner ring 61 and the outer ring 62. The space sealed by these plurality of oil seals 14, 15, 16 constitutes a lubricant retention space 17 (see FIG. 9). The lubricant retention space 17 includes the space between the inner ring 61 and the outer ring 62 of the bearing member 6. Furthermore, the lubricant retention space 17 contains multiple outer pins 23, planetary gears 3, eccentric bearings 5, support 8, first bearing 91, second bearing 92, etc.

The lubricant is injected into the lubricant retaining space 17. The lubricant is liquid and can flow in the lubricant retaining space 17. Therefore, when the gear device 1 is used, the lubricant enters, for example, the meshing portion between the internal teeth 21 consisting of the multiple outer pins 23 and the external teeth 31 of the planetary gear 3. In this disclosure, the term "liquid" includes liquid or gel-like substances. The term "gel-like" here means a state having intermediate properties between liquid and solid, and includes a colloidal state consisting of two phases, a liquid phase and a solid phase. For example, the term "gel-like" includes a state called a gel or sol, such as an emulsion in which the dispersion medium is in a liquid phase and the dispersoid is in a liquid phase, and a suspension in which the dispersoid is in a solid phase. The term "gel-like" also includes a state in which the dispersion medium is in a solid phase and the dispersoid is in a liquid phase. In this embodiment, as an example, the lubricant is a liquid lubricating oil (oil).

In the gear device 1 having the above-mentioned configuration, a rotational force is applied to the eccentric shaft 7 as an input, and the eccentric shaft 7 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 inscribed in the internal gear 2 inside the internal gear 2, and oscillates with a part of the external teeth 31 meshing with a part of the internal teeth 21, so that the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2. As a result, a relative rotation according 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). The rotation (rotation component) of the planetary gear 3, excluding the oscillation component (revolution component) of the planetary gear 3, is transmitted to the inner ring 61 of the bearing member 6 by the multiple inner pins 4. As a result, a rotation output reduced at a relatively high reduction ratio according to the difference in the number of teeth between the two gears is obtained from the output shaft integrated with the inner ring 61.

As described above, in the gear device 1 according to this embodiment, the difference in the number of teeth between the internal gear 2 and the planetary gear 3 determines the reduction ratio of the output rotation to the input rotation in the gear device 1. In other words, if 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 expressed by the following formula 1.

R1=V2/(V1-V2) (Equation 1)
In short, 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, the number of teeth V1 of the internal gear 2 is "52", the number of teeth V2 of the planetary gear 3 is "51", and the difference in the number of teeth (V1-V2) is "1", so from the above formula 1, the reduction ratio R1 is "51". In this case, when viewed from the input side of the rotation axis Ax1, when the eccentric shaft 7 rotates one revolution (360 degrees) clockwise around the rotation axis Ax1, the inner ring 61 rotates counterclockwise around the rotation axis Ax1 by the difference in the number of teeth of "1" (i.e., approximately 7.06 degrees).

With the gear device 1 according to this embodiment, such a high reduction ratio R1 can be achieved with a combination of one gear stage (internal gear 2 and planetary gear 3).

The gear device 1 must include at least an internal gear 2, a planetary gear 3, a number of internal pins 4, a bearing member 6, and a support 8, and may further include other components such as a spline bush.

In the case of the gear device 1 according to the present embodiment, when the input rotation on the high-speed rotating side is accompanied by eccentric motion, if the weight balance of the rotating body rotating at high speed is not maintained, it may lead to vibration, etc., so a counterweight or the like may be used to balance the weight. That is, since a rotating body consisting of at least one of the eccentric inner ring 51 and a member (eccentric shaft 7) rotating with the eccentric inner ring 51 moves eccentrically at high speed, it is preferable to balance the weight of the rotating body with respect to the rotation axis Ax1. In this embodiment, as shown in Figures 3 and 4, a gap 75 is provided in a part of the eccentric portion 72 of the eccentric shaft 7, thereby balancing the weight of the rotating body with respect to the rotation axis Ax1.

In short, in this embodiment, instead of adding a counterweight or the like, a part of the rotating body (here, the eccentric shaft 7) is hollowed out to reduce its weight, thereby balancing the weight of the rotating body with respect to the rotation axis Ax1. That is, the gear device 1 according to this embodiment is provided with an eccentric bearing 5 that is housed in an opening 33 formed in the planetary gear 3 and swings the planetary gear 3. The eccentric bearing 5 has an eccentric outer ring 52 and an eccentric inner ring 51 that is arranged inside the eccentric outer ring 52. A rotating body consisting of at least one of the eccentric inner ring 51 and a member that rotates with the eccentric inner ring 51 has a gap 75 in a part on the center C1 side of the eccentric outer ring 52 as viewed from the rotation axis Ax1 of the eccentric inner ring 51. In this embodiment, the eccentric shaft 7 is a "member that rotates with the eccentric inner ring 51" and corresponds to a "rotating body". Therefore, the gap 75 formed in the eccentric part 72 of the eccentric shaft 7 corresponds to the gap 75 of the rotating body. As shown in Figures 3 and 4, this gap 75 is located on the center C1 side when viewed from the rotation axis Ax1, so it acts to make the weight balance of the eccentric shaft 7 closer to even in the circumferential direction from the rotation axis Ax1.

More specifically, the gap 75 includes a recess formed on the inner circumferential surface of a through hole 73 that penetrates the rotor along the rotation axis Ax1 of the eccentric inner ring 51. That is, in this embodiment, since the rotor is an eccentric shaft 7, the recess formed on the inner circumferential surface of the through hole 73 that penetrates the eccentric shaft 7 along the rotation axis Ax1 functions as the gap 75. In this way, by using the recess formed on the inner circumferential surface of the through hole 73 as the gap 75, it is possible to balance the weight of the rotor without changing the appearance.

In this embodiment, the internal gear 2 is an example of a "first gear," and the planetary gear 3 is an example of a "second gear." That is, the first gear is an internal gear 2 having an annular gear body 22 and a number of outer pins 23. The outer pins 23 are rotatably held in a number of inner circumferential grooves 223 formed on the inner circumferential surface 221 of the gear body 22, forming the internal teeth 21. The second gear is a planetary gear 3 having external teeth 31 that partially mesh with the internal teeth 21. In this gear device 1, the planetary gear 3 is oscillated about the rotation axis Ax1, thereby rotating the planetary gear 3 relative to the internal gear 2.

(3.2) Rotation Structure of Inner Pin Next, the rotation structure of the inner pin 4 of the gear device 1 according to this embodiment will be described in more detail with reference to Fig. 9. Fig. 9 is an enlarged view of region Z1 in Fig. 3.

First, as a premise, as described above, the multiple inner pins 4 are components that connect the planetary gear 3 and the inner ring 61 of the bearing member 6. Specifically, one longitudinal end of the inner pin 4 (in this embodiment, the end on the input side of the rotation axis Ax1) is inserted into the loose fitting hole 32 of the planetary gear 3, and the other longitudinal end of the inner pin 4 (in this embodiment, the end on the output side of the rotation axis Ax1) is inserted into the retaining hole 611 of the inner ring 61.

Here, since the diameter of the inner pin 4 is slightly smaller than the diameter of the loose fitting hole 32, a gap is secured between the inner pin 4 and the inner peripheral surface 321 of the loose fitting hole 32, and the inner pin 4 can move within the loose fitting hole 32, that is, it can move relatively to the center of the loose fitting hole 32. On the other hand, the diameter of the retaining hole 611 is equal to or larger than the diameter of the inner pin 4, but is smaller than the diameter of the loose fitting hole 32. In this embodiment, the diameter of the retaining hole 611 is approximately the same as the diameter of the inner pin 4, and is slightly larger than the diameter of the inner pin 4. Therefore, the movement of the inner pin 4 within the retaining hole 611 is restricted, that is, the movement relative to the center of the retaining hole 611 is prohibited. Therefore, the inner pin 4 is held in a state in which it can revolve within the loose fitting hole 32 in the planetary gear 3, and is held in a state in which it cannot revolve within the retaining hole 611 relative to the inner ring 61. As a result, the oscillation component of the planetary gear 3, i.e., the revolution component of the planetary gear 3, is absorbed by the loose fit between the loose fit hole 32 and the inner pin 4, and the rotation (rotation component) of the planetary gear 3, excluding the oscillation component (revolution component) of the planetary gear 3, is transmitted to the inner ring 61 by the multiple inner pins 4.

In this embodiment, the diameter of the inner pin 4 is slightly larger than the retaining hole 611, so that the inner pin 4 is prohibited from revolving within the retaining hole 611 when inserted into the retaining hole 611, but is able to rotate within the retaining hole 611. In other words, even when inserted into the retaining hole 611, the inner pin 4 is not pressed into the retaining hole 611, so it is able to rotate within the retaining hole 611. In this way, in the gear device 1 according to this embodiment, each of the multiple inner pins 4 is held by the inner ring 61 in a rotatable state, so that the inner pin 4 itself can rotate when it revolves within the loose fitting hole 32.

In short, in this embodiment, the inner pin 4 is held in a state in which it can both revolve and rotate within the loose fitting hole 32 relative to the planetary gear 3, and is held in a state in which it can only rotate within the retaining hole 611 relative to the inner ring 61. In other words, the multiple inner pins 4 can rotate (revolve) around the rotation axis Ax1 and revolve within the multiple loose fitting holes 32 in a state in which their respective rotations are not restricted (a state in which they can rotate). Therefore, when the multiple inner pins 4 transmit the rotation (rotation component) of the planetary gear 3 to the inner ring 61, the inner pin 4 can rotate within the retaining hole 611 while revolving and rotating within the loose fitting hole 32. Therefore, when the inner pin 4 revolves within the loose fitting hole 32, the inner pin 4 is in a state in which it can rotate, and therefore rolls against the inner peripheral surface 321 of the loose fitting hole 32. In other words, the inner pin 4 revolves within the loose-fitting hole 32 by rolling on the inner circumferential surface 321 of the loose-fitting hole 32, so losses due to frictional resistance between the inner circumferential surface 321 of the loose-fitting hole 32 and the inner pin 4 are unlikely to occur.

In this way, in the configuration according to this embodiment, since loss due to frictional resistance between the inner peripheral surface 321 of the loose fitting hole 32 and the inner pin 4 is unlikely to occur in the first place, it is possible to omit the inner roller. Therefore, in this embodiment, a configuration is adopted in which each of the multiple inner pins 4 directly contacts the inner peripheral surface 321 of the loose fitting hole 32. In other words, in this embodiment, the inner pin 4 without the inner roller is inserted into the loose fitting hole 32, and the inner pin 4 directly contacts the inner peripheral surface 321 of the loose fitting hole 32. As a result, the inner roller can be omitted and the diameter of the loose fitting hole 32 can be kept relatively small, making it possible to reduce the size of the planetary gear 3 (especially the diameter), and making it easier to reduce the size of the gear device 1 as a whole. If the dimensions of the planetary gear 3 are constant, it is possible to increase the number (number) of inner pins 4 to smooth the transmission of rotation, or to thicken the inner pins 4 to improve strength, compared to the first related technology. Furthermore, the number of parts can be reduced by the amount of the inner roller, which also leads to lower costs for the gear device 1.

In the gear device 1 according to this embodiment, at least a portion of each of the inner pins 4 is disposed at the same position as the bearing member 6 in the axial direction of the bearing member 6. That is, as shown in FIG. 9, at least a portion of the inner pin 4 is disposed at the same position as the bearing member 6 in the direction parallel to the rotation axis Ax1. In other words, at least a portion of the inner pin 4 is located between both end faces of the bearing member 6 in the direction parallel to the rotation axis Ax1. In other words, at least a portion of each of the inner pins 4 is disposed inside the outer ring 62 of the bearing member 6. In this embodiment, the end of the inner pin 4 on the output side of the rotation axis Ax1 is at the same position as the bearing member 6 in the direction parallel to the rotation axis Ax1. In short, the end of the inner pin 4 on the output side of the rotation axis Ax1 is inserted into the retaining hole 611 formed in the inner ring 61 of the bearing member 6, so that at least the end is disposed at the same position as the bearing member 6 in the axial direction of the bearing member 6.

In this way, at least a portion of each of the multiple inner pins 4 is positioned at the same position as the bearing member 6 in the axial direction of the bearing member 6, so that the dimensions of the gear device 1 in the direction parallel to the rotation axis Ax1 can be kept small. In other words, compared to a configuration in which the bearing member 6 and the inner pins 4 are lined up (opposed) in the axial direction of the bearing member 6, the gear device 1 according to this embodiment can reduce the dimensions of the gear device 1 in the direction parallel to the rotation axis Ax1, which can contribute to further miniaturization (thinning) of the gear device 1.

The open surface of the retaining hole 611 on the output side of the rotating shaft Ax1 is closed by, for example, an output shaft that is integrated with the inner ring 61. As a result, movement of the inner pin 4 toward the output side of the rotating shaft Ax1 (the right side in FIG. 9) is restricted by the output shaft that is integrated with the inner ring 61.

In addition, in this embodiment, the following configuration is adopted to ensure smooth rotation of the inner pin 4 relative to the inner ring 61. That is, the rotation of the inner pin 4 is made smooth by interposing a lubricant (lubricating oil) between the inner circumferential surface of the retaining hole 611 formed in the inner ring 61 and the inner pin 4. In particular, in this embodiment, a lubricant retention space 17 into which a lubricant is injected is present between the inner ring 61 and the outer ring 62, and the lubricant in the lubricant retention space 17 is used to smooth the rotation of the inner pin 4.

In this embodiment, as shown in FIG. 9, the inner ring 61 has a plurality of retaining holes 611 into which the plurality of inner pins 4 are respectively inserted, and a plurality of connecting passages 64. The plurality of connecting passages 64 connect the lubricant retaining space 17 between the inner ring 61 and the outer ring 62 and the plurality of retaining holes 611. Specifically, the inner ring 61 has a connecting passage 64 extending in the radial direction from a portion of the inner peripheral surface of the retaining hole 611 that corresponds to the rolling element 63. The connecting passage 64 is a hole that penetrates between the bottom surface of a recess (groove) that accommodates the rolling element 63 on the surface of the inner ring 61 facing the outer ring 62 and the inner peripheral surface of the retaining hole 611. In other words, the opening surface of the connecting passage 64 on the lubricant retaining space 17 side is arranged at a position facing (opposing) the rolling element 63 of the bearing member 6. The lubricant retaining space 17 and the retaining hole 611 are spatially connected via such a connecting passage 64.

According to the above-mentioned configuration, the lubricant retaining space 17 and the retaining hole 611 are connected by the connecting passage 64, so that the lubricant in the lubricant retaining space 17 is supplied to the retaining hole 611 through the connecting passage 64. In other words, when the bearing member 6 operates and the rolling body 63 rotates, the rolling body 63 functions as a pump and can send the lubricant in the lubricant retaining space 17 to the retaining hole 611 via the connecting passage 64. In particular, since the opening surface of the connecting passage 64 on the lubricant retaining space 17 side is located in a position facing (opposing) the rolling body 63 of the bearing member 6, the rolling body 63 efficiently acts as a pump when the rolling body 63 rotates. As a result, the lubricant is interposed between the inner peripheral surface of the retaining hole 611 and the inner pin 4, and the rotation of the inner pin 4 relative to the inner ring 61 can be smoothed.

(3.3) Support Next, the configuration of the support 8 of the gear device 1 according to this embodiment will be described in more detail with reference to Fig. 10. Fig. 10 is a cross-sectional view taken along line B1-B1 in Fig. 3. However, in Fig. 10, hatching is omitted for parts other than the support 8, even in the cross section. Also, Fig. 10 shows only the internal gear 2 and the support 8, and omits illustration of other parts (such as the inner pin 4). Furthermore, Fig. 10 omits illustration of the inner circumferential surface 221 of the gear body 22.

First, as a premise, the support 8 is a component that supports the multiple inner pins 4, as described above. In other words, the support 8 bundles the multiple inner pins 4 together to distribute the load on the multiple inner pins 4 when transmitting the rotation (rotation component) of the planetary gear 3 to the inner ring 61. Specifically, it has multiple support holes 82 into which the multiple inner pins 4 are inserted. In this embodiment, as an example, the diameter of the support hole 82 is equal to the diameter of the retaining hole 611 formed in the inner ring 61. Therefore, the support 8 supports the multiple inner pins 4 in a state in which each of the multiple inner pins 4 can rotate on its own axis. In other words, each of the multiple inner pins 4 is held in a state in which it can rotate on its own axis with respect to both the inner ring 61 of the bearing member 6 and the support 8.

In this way, the support body 8 positions the multiple inner pins 4 relative to the support body 8 in both the circumferential and radial directions. In other words, by inserting the inner pins 4 into the support holes 82 of the support body 8, movement in all directions within a plane perpendicular to the rotation axis Ax1 is restricted. Therefore, the inner pins 4 are positioned by the support body 8 not only in the circumferential direction but also in the radial direction.

Here, the support 8 has an annular shape in which at least the outer peripheral surface 81 is a perfect circle in a plan view. The outer peripheral surface 81 of the support 8 is regulated in position by contacting the outer peripheral surface 81 with the multiple outer pins 23 of the internal gear 2. The multiple outer pins 23 form the internal teeth 21 of the internal gear 2, so in other words, the support 8 is regulated in position by contacting the outer peripheral surface 81 with the internal teeth 21. Here, the diameter of the outer peripheral surface 81 of the support 8 is the same as the diameter of a virtual circle (tooth tip circle) passing through the tips of the internal teeth 21 of the internal gear 2. Therefore, all of the multiple outer pins 23 are in contact with the outer peripheral surface 81 of the support 8. Therefore, when the support 8 is regulated in position by the multiple outer pins 23, the center of the support 8 is regulated in position so that it overlaps with the center (rotation axis Ax1) of the internal gear 2. This causes the support 8 to be centered, and as a result, the multiple inner pins 4 supported by the support 8 are also centered by the multiple outer pins 23.

The inner pins 4 rotate (revolve) around the rotation axis Ax1 to transmit the rotation (rotation component) of the planetary gear 3 to the inner ring 61. Therefore, the support 8 supporting the inner pins 4 rotates around the rotation axis Ax1 together with the inner pins 4 and the inner ring 61. At this time, the support 8 is centered by the outer pins 23, so the support 8 rotates smoothly while the center of the support 8 is maintained on the rotation axis Ax1. Moreover, the support 8 rotates with its outer peripheral surface 81 in contact with the outer pins 23, so that each of the outer pins 23 rotates (rotates) with the rotation of the support 8. Therefore, the support 8 forms a needle bearing together with the internal gear 2, and rotates smoothly.

In other words, the outer peripheral surface 81 of the support 8 rotates together with the multiple inner pins 4 relative to the gear body 22 while in contact with the multiple outer pins 23. Therefore, if the gear body 22 of the internal gear 2 is considered to be the "outer ring" and the support 8 is considered to be the "inner ring," the multiple outer pins 23 interposed between the two function as "rolling elements (rollers)." In this way, the support 8, together with the internal gear 2 (gear body 22 and multiple outer pins 23), constitutes a needle bearing, enabling smooth rotation.

Furthermore, since the support 8 sandwiches the outer pins 23 between itself and the gear body 22, the support 8 also functions as a "stopper" that suppresses movement of the outer pins 23 away from the inner circumferential surface 221 of the gear body 22. In other words, the outer pins 23 are sandwiched between the outer circumferential surface 81 of the support 8 and the inner circumferential surface 221 of the gear body 22, suppressing lifting of the outer pins 23 from the inner circumferential surface 221 of the gear body 22. In short, in this embodiment, each of the outer pins 23 comes into contact with the outer circumferential surface 81 of the support 8, thereby restricting movement away from the gear body 22.

In this embodiment, as shown in FIG. 9, the support 8 is located on the opposite side of the inner ring 61 of the bearing member 6 across the planetary gear 3. In other words, the support 8, the planetary gear 3, and the inner ring 61 are arranged in a direction parallel to the rotation axis Ax1. In this embodiment, as an example, the support 8 is located on the input side of the rotation axis Ax1 as viewed from the planetary gear 3, and the inner ring 61 is located on the output side of the rotation axis Ax1 as viewed from the planetary gear 3. The support 8 supports both ends of the inner pin 4 in the longitudinal direction (direction parallel to the rotation axis Ax1) together with the inner ring 61, and the central portion of the inner pin 4 in the longitudinal direction is inserted into the loose fitting hole 32 of the planetary gear 3. In short, the gear device 1 according to this embodiment has an outer ring 62 and an inner ring 61 arranged inside the outer ring 62, and is provided with a bearing member 6 in which the inner ring 61 is supported so as to be rotatable relative to the outer ring 62. The gear body 22 is fixed to the outer ring 62. Here, the planetary gear 3 is located between the support 8 and the inner ring 61 in the axial direction of the support 8.

According to this configuration, the support 8 and the inner ring 61 support both ends of the inner pin 4 in the longitudinal direction, so that the inner pin 4 is less likely to tilt. In particular, the inner pins 4 are more likely to receive bending forces (bending moment loads) with respect to the rotation axis Ax1. In addition, in this embodiment, the support 8 is sandwiched between the planetary gear 3 and the case 10 in a direction parallel to the rotation axis Ax1. As a result, the movement of the support 8 toward the input side of the rotation axis Ax1 (left side in FIG. 9) is restricted by the case 10. The movement of the inner pin 4 that penetrates the support hole 82 of the support 8 and protrudes from the support 8 toward the input side of the rotation axis Ax1 is also restricted by the case 10 toward the input side of the rotation axis Ax1 (left side in FIG. 9).

In this embodiment, the support 8 and the inner ring 61 contact both ends of the outer pins 23. That is, as shown in FIG. 9, the support 8 contacts one end (the end on the input side of the rotation axis Ax1) of the outer pins 23 in the longitudinal direction (parallel to the rotation axis Ax1). The inner ring 61 contacts the other end (the end on the output side of the rotation axis Ax1) of the outer pins 23 in the longitudinal direction (parallel to the rotation axis Ax1). With this configuration, the support 8 and the inner ring 61 are centered at both ends of the outer pins 23 in the longitudinal direction, so that the inner pins 4 are less likely to tilt. In particular, the inner pins 4 are more likely to receive bending forces (bending moment loads) against the rotation axis Ax1.

The multiple outer pins 23 also have a length equal to or greater than the thickness of the support 8. In other words, in the direction parallel to the rotation axis Ax1, the support 8 fits within the range of the tooth trace of the internal teeth 21. This means that the outer peripheral surface 81 of the support 8 comes into contact with the multiple outer pins 23 over the entire length in the tooth trace direction of the internal teeth 21 (direction parallel to the rotation axis Ax1). Therefore, problems such as "uneven wear", in which the outer peripheral surface 81 of the support 8 is partially worn, are less likely to occur.

In addition, in this embodiment, the outer peripheral surface 81 of the support 8 has a smaller surface roughness than the surface adjacent to the outer peripheral surface 81 of the support 8. In other words, the surface roughness of the outer peripheral surface 81 is smaller than both end surfaces of the support 8 in the axial direction (thickness direction). In this disclosure, "surface roughness" refers to the degree of roughness of the surface of an object, and the smaller the value, the smaller (fewer) the surface irregularities are, and the smoother the surface is. In this embodiment, as an example, the surface roughness is the arithmetic mean roughness (Ra). For example, by processing such as polishing, the outer peripheral surface 81 has a smaller surface roughness than the surfaces of the support 8 other than the outer peripheral surface 81. In this configuration, the rotation of the support 8 becomes smoother.

In this embodiment, the hardness of the outer peripheral surface 81 of the support 8 is lower than that of the peripheral surfaces of the outer pins 23 and higher than that of the inner peripheral surface 221 of the gear body 22. In this disclosure, "hardness" means the degree of hardness of an object, and the hardness of a metal is expressed, for example, by the size of a depression made by pressing a steel ball with a certain pressure. Specifically, examples of metal hardness include Rockwell hardness (HRC), Brinell hardness (HB), Vickers hardness (HV), and Shore hardness (Hs). Means for increasing (hardening) the hardness of metal parts include, for example, alloying or heat treatment. In this embodiment, as an example, the hardness of the outer peripheral surface 81 of the support 8 is increased by a process such as carburizing and quenching. In this configuration, wear powder and the like is less likely to be generated even when the support 8 rotates, and it is easy to maintain smooth rotation of the support 8 for a long period of time.

(4) Application Examples Next, application examples of the gear device 1 and the actuator 100 according to this embodiment will be described.

The gear device 1 and actuator 100 according to this embodiment are applied to a robot such as a horizontal articulated robot, a so-called SCARA (Selective Compliance Assembly Robot Arm) type robot.

In addition, application examples of the gear device 1 and actuator 100 according to this embodiment are not limited to the horizontal articulated robot described above, but may be, for example, industrial robots other than horizontal articulated robots, or non-industrial robots. Examples of industrial robots other than horizontal articulated robots include vertical articulated robots and parallel link robots. Examples of non-industrial robots include domestic robots, nursing care robots, and medical robots.

(5) Details of the Internal Gear Next, details of the internal gear 2 in the gear device 1 according to this embodiment will be described with reference to Figs. 11 to 13. Fig. 11 is a schematic cross-sectional view showing an enlarged meshing portion between the internal teeth 21 (outer pins 23) and the external teeth 31 in Fig. 9, with parts other than the internal gear 2 (gear body 22 and outer pins 23) and the planetary gears 3 being omitted. Fig. 12 is a schematic cross-sectional view taken along line A1-A1 in Fig. 11, with parts other than the internal gear 2 and planetary gears 3 being omitted as in Fig. 11. Also, in Figs. 11 and 12, schematic enlarged views of the main parts are shown in speech bubbles.

In the gear device 1, which includes a first gear (internal gear 2) and a second gear (planetary gear 3) that rotates relative to the first gear by meshing with the first gear as in this embodiment, for example, "sliding contact" occurs between the gear body 22 of the first gear (internal gear 2) and the outer pin 23 that forms the internal teeth 21. In this disclosure, "sliding contact" refers to a contact state between two parties in which macroscopic slippage (gross slip) occurs, compared to the microscopic slippage (microslip) in rolling contact (or fixed contact) and the like. In other words, "sliding contact" is one of the motion forms of two solid surfaces that are in contact and move relative to each other, and is a form of relative motion that causes macroscopic slippage between the two parties, unlike rolling contact.

In this way, in the first gear (internal gear 2), a coating layer 224 is formed on "sliding contact areas" such as the inner surfaces of the multiple inner circumferential grooves 223 where sliding contact occurs with another component (here, the outer pin 23) as shown in Figures 11 and 12. Here, the coating layer 224 is a layer that covers at least a part of the skeletal portion 225 that serves as the base material. In other words, in this embodiment, at least the inner surfaces of the multiple inner circumferential grooves 223 that serve as sliding contact areas of the skeletal portion 225 that serves as the base material of the gear body 22 of the internal gear 2 are covered with the coating layer 224.

The coating layer 224 is made of a material having a higher specific gravity than the skeletal portion 225. In this embodiment, both the coating layer 224 and the skeletal portion 225 are made of metal, and the coating layer 224 is made of a metal having a higher specific gravity than the skeletal portion 225. As an example, the skeletal portion 225, which is the base material of the gear body 22, is made of aluminum (Al), and the coating layer 224 is made of iron (Fe).

In short, the gear device 1 according to this embodiment includes a first gear (internal gear 2) and a second gear (planetary gear 3). The second gear rotates relative to the first gear by meshing with the first gear. The first gear has a skeletal portion 225 and a coating layer 224 having a higher specific gravity than the skeletal portion 225. At least the portion of the skeletal portion 225 that comes into sliding contact with other components is covered with the coating layer 224.

According to the configuration described above, the skeleton 225 of the first gear (internal gear 2) itself is made of a material with a low specific gravity, so that even if it has a certain thickness, it is possible to keep the weight relatively small. On the other hand, the sliding contact area (with other parts) of the skeleton 225 is covered with a coating layer 224 with a higher specific gravity than the skeleton 225, so that the wear resistance of the sliding contact area is improved and the strength of the first gear (internal gear 2) can be maintained. As a result, the gear device 1 according to this embodiment makes it possible to realize a gear device 1 that is easy to reduce weight while maintaining its strength.

In this embodiment, the first gear is the internal gear 2 and the second gear is the planetary gear 3, so that the inner surfaces of the multiple inner circumferential grooves 223 in the skeleton 225 of the internal gear 2 with which at least the multiple outer pins 23 as other components come into sliding contact are the sliding contact areas. Therefore, at least the inner surfaces (sliding contact areas) of the multiple inner circumferential grooves 223 are covered with the coating layer 224.

In other words, as shown in Figures 11 and 12, the inner surfaces of the multiple inner circumferential grooves 223 that hold the multiple outer pins 23 of the gear body 22 are covered with the coating layer 224, so that even if each outer pin 23 rotates (spins) and makes sliding contact with the inner surface of the inner circumferential groove 223, it is possible to suppress wear of the inner surface of the inner circumferential groove 223. In short, with respect to the inner surface of the inner circumferential groove 223 with which the outer pins 23 make sliding contact, the skeleton part 225 is covered with the coating layer 224, so that the skeleton part 225 is protected, and wear resistance can be increased and strength can be maintained. Therefore, when the planetary gear 3 rotates relative to the internal gear 2, wear of the gear body 22 due to sliding contact of the outer pins 23 is suppressed.

In this embodiment, the coating layer 224 is formed around the entire circumference of the inner circumferential surface 221 of the gear body 22 so as to cover the entire inner surface of the inner circumferential groove 223. Therefore, the skeleton portion 225 is not exposed on the inner surface of the inner circumferential groove 223 with which the outer pin 23 slides. However, as shown in FIG. 11, the coating layer 224 is not formed on both ends of the inner circumferential surface 221 of the gear body 22 in the tooth trace direction of the internal teeth 21 (direction parallel to the rotation axis Ax1), and the skeleton portion 225 is exposed. Specifically, on the inner circumferential surface 221 of the gear body 22, the portion constituting the inner circumferential groove 223 protrudes toward the inside (the rotation axis Ax1 side), and the coating layer 224 is formed to cover only this protruding portion.

In this embodiment, particularly, the coating layer 224 is formed so as to completely cover the skeletal portion 225 at the corners at both ends of the inner circumferential groove 223 in the tooth trace direction of the internal tooth 21, that is, the portions that form an outward corner shape in the cross section shown in FIG. 11. In other words, the coating layer 224 is formed from the inner surface of the inner circumferential groove 223 to the step portion adjacent thereto. In this way, since the corners are covered with the coating layer 224, even if the corners come into contact with the outer pin 23, the outer pin 23 can be prevented from coming into direct contact with the skeletal portion 225, and wear of the skeletal portion 225 is easily suppressed.

In this embodiment, coating layer 224 is formed by thermal spraying. In this disclosure, "thermal spraying" refers to a processing technique in which a coating is formed on the surface of an object to be processed by spraying particles of a spray material, such as a metal, melted and softened by various heat sources onto the surface of the object to be processed. When the molten particles sprayed by thermal spraying adhere to the base material, such as a metal, of the object to be processed, they instantly cool and solidify to form a coating. The coating formed by thermal spraying on skeleton portion 225 constitutes coating layer 224.

That is, the manufacturing method of the gear device 1 according to this embodiment includes a thermal spraying process in which a coating layer 224 is formed by thermal spraying on at least a part of the skeleton portion 225 of the first gear (internal gear 2). The coating layer 224 formed by thermal spraying can have a larger thickness than a coating formed by a method such as plating or vapor deposition.

However, since a porous film may occur on the surface of the coating formed by thermal spraying, it is preferable to finish the surface. Therefore, the manufacturing method of the gear device 1 according to this embodiment includes a surface finishing process such as polishing after the thermal spraying process. Although the surface finishing process reduces the thickness of the coating formed by thermal spraying, by forming a coating of sufficient thickness by thermal spraying, it is possible to achieve a coating (coating layer 224) of sufficient thickness even after the surface finishing process.

The skeletal portion 225 also has a higher thermal conductivity than the coating layer 224. In this embodiment, as described above, the coating layer 224 is made of iron (Fe), and therefore the thermal conductivity of the coating layer 224 is 80.3 (W/m·K). In contrast, the skeletal portion 225 is made of aluminum (Al), and therefore the thermal conductivity of the skeletal portion 225 is 237 (W/m·K). In other words, the skeletal portion 225 has a thermal conductivity nearly three times that of the coating layer 224. This allows most of the gear body 22 of the first gear (internal gear 2) to be composed of the skeletal portion 225, which has a high thermal conductivity, and improves the heat dissipation of the first gear (internal gear 2).

For example, when heat is generated due to friction or the like at the meshing portion between the first gear (internal gear 2) and the second gear (planetary gear 3) or at the sliding contact point of the outer pin 23 on the gear body 22 as the gear device 1 operates, the generated heat can be efficiently dissipated. In particular, the gear body 22, together with the case 10, forms part of the outer shell of the gear device 1, and heat generated inside the gear device 1 can be efficiently dissipated to the outside of the gear device 1.

In addition, in this embodiment, the coating layer 224 is a sprayed film having a different composition from the skeletal portion 225. That is, as described above, the coating layer 224 is a sprayed film formed by spraying. Here, while a sprayed film having the same composition as the skeletal portion 225 can also be formed on the surface of the skeletal portion 225, in this embodiment, a sprayed film having a different composition from the skeletal portion 225 is formed. Specifically, the skeletal portion 225 is made of aluminum (Al), while the coating layer 224 is made of iron (Fe).

However, in consideration of the adhesion of the coating layer 224 to the skeleton 225, it is preferable that the linear expansion coefficients of the skeleton 225 and the coating layer 224 are close to each other. Specifically, in a temperature environment of 93°C (200°F) or less, it is preferable that the linear expansion coefficients of the two are close enough that the coating layer 224 does not peel off from the skeleton 225 due to the difference in linear expansion coefficients.

In addition, in this embodiment, the coating layer 224 has a thickness of 50 μm or more. In other words, the coating layer 224 formed by thermal spraying has a characteristic that it can have a larger film thickness than a coating formed by a method such as plating or vapor deposition, and the specific film thickness is preferably 50 μm or more. As an example, a 150 μm coating is formed on the surface of the skeleton part 225 in the thermal spraying process, and then polished 100 μm in the surface finishing process, resulting in a 50 μm coating layer 224. By having the coating layer 224 have such a sufficient film thickness, it is possible to prevent the outer pin 23 from directly contacting the skeleton part 225, and wear of the skeleton part 225 is easily suppressed.

Here, the first gear (internal gear 2) has a base layer 226 on the surface of the skeleton 225, and the coating layer 224 is laminated on the base layer 226. That is, as shown in the speech bubbles in Figures 11 and 12, the base layer 226 and the coating layer 224 are laminated in this order on the surface of the skeleton 225. As a result, the coating layer 224 is not laminated directly on the surface of the skeleton 225, but is laminated via the base layer 226, which improves the adhesion of the coating layer 224 to the skeleton 225.

The base layer 226 is formed on the surface of the skeletal part 225, for example, by processing that increases the surface roughness (arithmetic mean roughness (Ra)) of the skeletal part 225. Specifically, in this embodiment, as an example, the base layer 226 is formed by performing laser peening on the surface of the skeletal part 225. The "laser peening" referred to in this disclosure is a surface modification technique in which a laser pulse is irradiated onto an object to be processed, compressive residual stress is imparted to the surface of the object to be processed, and the surface hardness is improved. In other words, the manufacturing method of the gear device 1 according to this embodiment includes a base formation process for forming the base layer 226 by laser peening or the like, prior to the thermal spraying process.

Here, it is preferable that the grain direction of the base layer 226 is a direction based on the sliding direction of the other part at the sliding contact area. That is, as shown in Figures 13A and 13B, the sliding direction of the other part is determined on the inner surface of the inner circumferential groove 223, which is the sliding contact area of the other part (outer pin 23) in the skeleton part 225. In other words, since the outer pin 23 rotates (spins) around its central axis within the inner circumferential groove 223, a sliding direction along the circumferential direction is generated on the inner surface of the inner circumferential groove 223. Therefore, by determining the grain direction of the base layer 226 based on this sliding direction, the adhesion of the coating layer 224 is improved and peeling of the coating layer 224 can be easily suppressed.

As an example, as shown in FIG. 13A, it is preferable that the grain direction of the base layer 226 formed by laser peening or the like is a direction that intersects with the sliding direction of the other component (outer pin 23) at the sliding contact area. For example, by making the grain direction of the base layer 226 a direction along the longitudinal direction of the inner circumferential groove 223, the grain direction of the base layer 226 is perpendicular to the sliding direction of the other component. With this configuration, even if the other component (outer pin 23) makes sliding contact with the coating layer 224 formed on the base layer 226, the coating layer 224 will get caught in the processing grain of the base layer 226 and will not easily peel off from the skeleton portion 225.

As another example, as shown in FIG. 13B, the base layer 226 formed by laser peening or the like may be arranged in a lattice pattern based on the sliding direction of the other component (outer pin 23) at the sliding contact site. For example, discrete processing marks are formed so as to be distributed approximately evenly in the longitudinal direction and circumferential direction of the inner circumferential groove 223. The individual processing marks may have any suitable shape, such as a circular ring, a polygonal shape, or a dot shape. With this configuration, even if the other component (outer pin 23) slides against the coating layer 224 formed on the base layer 226, the coating layer 224 will be caught by the processing marks of the base layer 226 and will not easily peel off from the skeleton 225.

(6) Modifications The first embodiment is merely one of various embodiments of the present disclosure. Various modifications of the first embodiment are possible depending on the design, etc., as long as the object of the present disclosure can be achieved. In addition, all drawings referred to in this disclosure are schematic drawings, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios. Modifications of the first embodiment are listed below. The modifications described below can be applied in appropriate combination.

The gear body 22 of the internal gear 2 may be seamlessly integrated with the case 10. In this case, the case 10 is made of the same material as the gear body 22 (e.g., aluminum), and the case 10 and gear body 22 are treated as a single component. In this configuration, the volume and surface area of the aluminum parts are larger than in a configuration in which the gear body 22 and case 10 are separate, and it is expected that the gear device 1 as a whole will be lighter and have better heat dissipation. Similarly, the outer ring 62 of the bearing member 6 may be seamlessly integrated with the gear body 22 of the internal gear 2.

It is not essential that the first gear is the internal gear 2 and the second gear is the planetary gear 3. For example, the first gear may be the planetary gear 3 and the second gear may be the internal gear 2. In this case, the base material of the planetary gear 3 forms the skeleton, and for example, the portion of the planetary gear 3 that comes into sliding contact with another part (the inner pin 4) is covered with a coating layer.

The skeleton 225 is not limited to iron (Fe), and the coating layer 224 is not limited to aluminum (Al). The coating layer 224 may be made of a material having a higher specific gravity than the skeleton 225, and at least one of the coating layer 224 and the skeleton 225 may be non-metallic. Even in this case, it is preferable that the skeleton 225 has a higher thermal conductivity than the coating layer 224.

The coating layer 224 is not limited to being formed by thermal spraying, and may be formed by methods other than thermal spraying.

The base layer 226 is not limited to laser peening, and may be formed by processing such as shot peening, in which a projecting material is projected onto the workpiece. The grain direction of the base layer 226 is not limited to the example shown in Figures 13A and 13B, and may be, for example, a direction along the sliding direction of the other component (outer pin 23), or a direction inclined with respect to the sliding direction of the other component (outer pin 23).

In the first embodiment, a gear device 1 having one type of planetary gear 3 is exemplified, but the gear device 1 may have two or more planetary gears 3. For example, when the gear device 1 has three planetary gears 3, it is preferable that these three planetary gears 3 are arranged with a phase difference of 120 degrees around the rotation axis Ax1. Alternatively, when the gear device 1 has three planetary gears 3, two of these three planetary gears 3 may be in phase, and the remaining planetary gear 3 may be arranged with a phase difference of 180 degrees around the rotation axis Ax1.

In addition, the number of outer pins 23 (the number of teeth of the internal teeth 21) and the number of teeth of the external teeth 31 described in embodiment 1 are merely examples and can be changed as appropriate.

In addition, the material of each component of the gear device 1 is not limited to metal, but may be, for example, a resin such as engineering plastic.

The gear device 1 is not limited to a configuration in which the rotational force of the inner ring 61 is output, as long as it can extract the relative rotation between the inner ring 61 and the outer ring 62 of the bearing member 6 as an output. For example, the rotational force of the outer ring 62 (case 10) rotating relative to the inner ring 61 may be output.

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

(Embodiment 2)
＜Overview＞
As shown in Figures 14 to 16, the gear device 1A according to this embodiment differs from the gear device 1 according to embodiment 1 in that it is an eccentric oscillating type internal meshing planetary gear device known as a distribution type. Hereinafter, common reference numerals are used for configurations similar to those in embodiment 1, and descriptions thereof will be omitted as appropriate. Figure 14 is a perspective view showing a schematic configuration of the gear device 1A. Figure 15 is a schematic exploded perspective view of the gear device 1A as viewed from the input side of the rotation axis Ax1. Figure 16 is a schematic cross-sectional view of the gear device 1A.

As shown in Figures 14 to 16, the gear device 1A according to this embodiment includes multiple (three in this embodiment) eccentric shafts (crank shafts) 7A, 7B, and 7C arranged at positions offset from the axis (rotation axis Ax1) of the internal gear 2. Furthermore, the gear device 1A includes an input shaft 500 centered on the rotation axis Ax1 arranged on the axis (rotation axis Ax1) of the internal gear 2, and an input gear 501 formed integrally with the input shaft 500. The multiple eccentric shafts 7A, 7B, and 7C are spline-connected to crank shaft gears 502A, 502B, and 502C, respectively. These multiple (three in this embodiment) crank shaft 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 1A drives the eccentric shafts 7A, 7B, and 7C synchronously with the input gear 501, causing the planetary gear 3 to oscillate and mesh internally with the internal gear 2.

The gear device 1A according to this embodiment also includes a plurality of planetary gears 3. Specifically, the gear device 1A includes two planetary gears 3, a first planetary gear 301 and a second planetary gear 302. The two planetary gears 3 are arranged to face each other in a direction parallel to the rotation axis Ax1. In other words, the planetary gears 3 include the first planetary gear 301 and the second planetary gear 302 that are aligned in a direction parallel to the rotation axis Ax1. The shapes of the first planetary gear 301 and the second planetary gear 302 themselves are the same.

These two planetary gears 3 (first planetary gear 301 and second planetary gear 302) are arranged with a phase difference of 180 degrees around the rotation axis Ax1. In the example of FIG. 16, the center C1 of the first planetary gear 301 located on the input side of the rotation axis Ax1 (right side of FIG. 16) of the first planetary gear 301 and the second planetary gear 302 is shifted (biased) upward from the rotation axis Ax1. On the other hand, the center C2 of the second planetary gear 302 located on the output side of the rotation axis Ax1 (left side of FIG. 16) is shifted (biased) downward from 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 with respect 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 with respect to the rotation axis Ax1. In this way, by arranging the multiple planetary gears 3 evenly in the circumferential direction around the rotation axis Ax1, it is possible to achieve a weight balance between the multiple planetary gears 3.

The centers C1 and C2 of the first planetary gear 301 and the second planetary gear 302 are located at 180 degrees rotational symmetry with respect to the rotation axis Ax1. In this embodiment, the eccentricity amount ΔL1 and the eccentricity amount ΔL2 are oriented in opposite directions as viewed from the rotation axis Ax1, but their absolute values are the same.

More specifically, each of the eccentric shafts 7A, 7B, and 7C has two eccentric portions 72 with respect to one axial portion 71. The eccentricity of the centers of these two eccentric portions 72 from the center of the axial portion 71 is the same as the eccentricity ΔL1 and ΔL2 of the first planetary gear 301 and the second planetary gear 302 with respect to the rotation axis Ax1, respectively. The shapes of the multiple eccentric shafts 7A, 7B, and 7C are the same. The shapes of the multiple crankshaft gears 502A, 502B, and 502C are also the same.

In addition, a carrier flange 18 and an output flange 19 are arranged on both sides of the first planetary gear 301 and the second planetary gear 302 in a direction parallel to the rotation axis Ax1. Both ends of each eccentric shaft 7A, 7B, 7C are held by the carrier flange 18 and the output flange 19 via rolling bearings 41, 42. In other words, each eccentric shaft 7A, 7B, 7C is held by the carrier flange 18 and the output flange 19 in a rotatable state on both sides of the direction parallel to the rotation axis Ax1 relative to the planetary gear 3.

An eccentric body bearing 5 is attached to the eccentric portion 72 of each of the eccentric shafts 7A, 7B, and 7C. Three openings 33 corresponding to the three eccentric shafts 7A, 7B, and 7C are formed in each of the first planetary gear 301 and the second planetary gear 302. The eccentric body bearing 5 is accommodated in each opening 33. In other words, the first planetary gear 301 and the second planetary gear 302 are each fitted with an eccentric body bearing 5, and the eccentric shafts 7A, 7B, and 7C are inserted into the eccentric body bearing 5, so that the eccentric body bearing 5 and the eccentric shafts 7A, 7B, and 7C are combined with the planetary gear 3. In the gear device 1A according to this embodiment, the inner pin 4 is omitted, and instead of the inner pin 4, multiple eccentric shafts 7A, 7B, and 7C are used to extract the rotation (rotation component) of the planetary gear 3, excluding the oscillation component (revolution component) of the planetary gear 3.

According to the above-described configuration, a rotational force is applied to the input shaft 500 as an input, and the input shaft 500 rotates around the rotation axis Ax1, and this rotational force is distributed from the input gear 501 to the multiple eccentric shafts 7A, 7B, and 7C. In other words, when the input gear 501 rotates, the three crankshaft gears 502A, 502B, and 502C that are simultaneously engaged with the input gear 501 rotate in the same direction at the same rotational speed. Since the eccentric shafts 7A, 7B, and 7C are spline-connected to the crankshaft gears 502A, 502B, and 502C, the three eccentric shafts 7A, 7B, and 7C rotate in the same direction at the same rotational speed while being decelerated by the gear ratio between the input gear 501 and the crankshaft gears 502A, 502B, and 502C. As a result, the three eccentric parts 72 formed at the same position on the input side of the rotation axis Ax1 on the three eccentric shafts 7A, 7B, and 7C rotate synchronously, causing the first planetary gear 301 to oscillate. Furthermore, the three eccentric parts 72 formed at the same position on the output side of the rotation axis Ax1 on the three eccentric shafts 7A, 7B, and 7C rotate synchronously, causing the second planetary gear 302 to oscillate.

As a result, the shaft centers 71 of the multiple eccentric shafts 7A, 7B, and 7C each rotate (spin) around the rotation axis Ax1, causing the first planetary gear 301 and the second planetary gear 302 to rotate (perform eccentric motion) around the rotation axis Ax1 with a phase difference of 180 degrees around the rotation axis Ax1.

Here, the first planetary gear 301 and the second planetary gear 302 are in inscribed mesh with the internal gear 2. Therefore, each time the first planetary gear 301 and the second planetary gear 302 oscillate once, the first planetary gear 301 and the second planetary gear 302 rotate on their own axis, with a circumferential phase shift of the difference in the number of teeth (between the internal teeth 21 and the external teeth 31) occurring with respect to the internal gear 2. This rotation is transmitted to the carrier flange 18 and the output flange 19 as a revolution around the axis (rotation axis Ax1) of the internal gear 2 of each eccentric shaft 7A, 7B, 7C. This allows the carrier flange 18 and the output flange 19 to rotate relative to the gear body (case 10 integrated with it) around the rotation axis Ax1.

In short, the gear device 1A according to this embodiment differs from the first embodiment in that the planetary gear 3 is oscillated by a plurality of eccentric shafts 7A, 7B, and 7C arranged at a position offset from the rotation axis Ax1, but is the same as the first embodiment in that the rotation output is obtained by utilizing the oscillation of the planetary gear 3. In other words, in the gear device 1A, when the planetary gear 3 oscillates and the meshing position between the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the internal gear 2, a relative rotation according 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 (spins) in accordance with the relative rotation of the two gears. As a result, the planetary gear 3 produces a rotation output that is reduced at a relatively high reduction ratio according to the difference in the number of teeth between the two gears.

More specifically, in the gear device 1A according to this embodiment, the bearing member 6A includes a first bearing member 601A and a second bearing member 602A. The first bearing member 601A and the second bearing member 602A are each made of an angular ball bearing. Specifically, as shown in FIG. 16, the first bearing member 601A is disposed on the input side (right side of FIG. 16) of the rotation axis Ax1 as viewed from the planetary gear 3, and the second bearing member 602A is disposed on the output side (left side of FIG. 16) of the rotation axis Ax1 as viewed from the planetary gear 3. The bearing member 6A is configured so that the first bearing member 601A and the second bearing member 602A can withstand any of a radial load, a thrust load (direction along the rotation axis Ax1), and a bending force (bending moment load) against the rotation axis Ax1.

Here, the first bearing member 601A and the second bearing member 602A are arranged on both sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1, facing opposite directions in the direction parallel to the rotation axis Ax1. In other words, the bearing member 6A is a "combined angular ball bearing" that combines multiple (here, two) angular ball bearings. As an example, the first bearing member 601A and the second bearing member 602A are of a "back-to-back combination type" that receives a load in the thrust direction (direction along the rotation axis Ax1) in which the respective inner rings approach each other. Furthermore, in the gear device 1A, the first bearing member 601A and the second bearing member 602A are combined in a state in which an appropriate preload acts on the inner rings by tightening the respective inner rings in a direction in which they approach each other.

The gear device 1A according to this embodiment also includes a carrier flange 18 and an output flange 19. The carrier flange 18 and the output flange 19 are disposed on both sides of the planetary gear 3 in a direction parallel to the rotation axis Ax1, and are connected to each other through the carrier hole 34 (see FIG. 16) of the planetary gear 3. Specifically, as shown in FIG. 16, the carrier flange 18 is disposed on the input side (right side in FIG. 16) of the rotation axis Ax1 as viewed from the planetary gear 3, and the output flange 19 is disposed on the output side (left side in FIG. 16) of the rotation axis Ax1 as viewed from the planetary gear 3. The inner rings of the bearing members 6A (each of the first bearing member 601A and the second bearing member 602A) are fixed to the carrier flange 18 and the output flange 19. In this embodiment, as an example, the inner ring of the first bearing member 601A is seamlessly integrated with the carrier flange 18. Similarly, the inner ring of the second bearing member 602A is seamlessly integrated with the output flange 19.

The output flange 19 has a plurality of (three, for example) carrier pins 191 (see FIG. 15) that protrude from one surface of the output flange 19 toward the input side of the rotation axis Ax1. These carrier pins 191 each pass through a plurality of (three, for example) carrier holes 34 formed in the planetary gear 3, and their tips are fixed to the carrier flange 18 by carrier bolts. A gap is provided between the carrier pins 191 and the inner peripheral surface of the carrier hole 34, and the carrier pins 191 are movable within the carrier hole 34, that is, are movable relative to the center of the carrier hole 34. This prevents the carrier pins 191 from coming into contact with the inner peripheral surface of the carrier hole 34 when the planetary gear 3 oscillates.

As a result, the gear device 1A is used to extract the rotation equivalent to the rotation component of the planetary gear 3 as the rotation of the carrier flange 18 and the output flange 19 integrated with the inner ring 61 of the bearing member 6A. That is, in the first embodiment, the relative rotation between the planetary gear 3 and the internal gear 2 is extracted as the rotation component of the planetary gear 3 from the inner ring 61 connected to the planetary gear 3 by a plurality of inner pins 4. In contrast, in the present embodiment, the relative rotation between the planetary gear 3 and the internal gear 2 is extracted from the carrier flange 18 and the output flange 19 integrated with the inner ring. In the present embodiment, as an example, the gear device 1A is used in a state where the outer ring 62 (see FIG. 16) of the bearing member 6A is fixed to the case 10, which is a fixed member. That is, the planetary gear 3 is connected to the rotating members, the carrier flange 18 and the output flange 19, by a plurality of eccentric shafts 7A, 7B, and 7C, and the gear body 22 is fixed to a fixed member, so that the relative rotation between the planetary gear 3 and the internal gear 2 is taken from the rotating members (the carrier flange 18 and the output flange 19). In other words, in this embodiment, when the planetary gear 3 rotates relative to the gear body 22, the rotational force of the carrier flange 18 and the output flange 19 is taken as an output.

Furthermore, in this embodiment, the case 10 is seamlessly integrated with the gear body 22 of the internal gear 2. That is, in embodiment 1, the gear body 22 of the internal gear 2 is used in a state where it is fixed to the case 10 together with the outer ring 62 of the bearing member 6. In contrast, in this embodiment, the gear body 22, which is the fixed member, and the case 10 are provided in a seamless continuity in the direction parallel to the rotation axis Ax1.

More specifically, the case 10 is cylindrical and constitutes the outer shell of the gear device 1A. In this embodiment, the central axis of the cylindrical case 10 is configured to coincide with the rotation axis Ax1. In other words, at least the outer peripheral surface of the case 10 is a perfect circle centered on the rotation axis Ax1 in a plan view (seen from one side in the direction of the rotation axis Ax1). The case 10 is formed in a cylindrical shape with both end faces in the direction of the rotation axis Ax1 open. Here, the gear body 22 of the internal gear 2 is seamlessly integrated with the case 10, and the case 10 and the gear body 22 are treated as one part. Therefore, the inner peripheral surface of the case 10 includes the inner peripheral surface 221 of the gear body 22. Furthermore, the outer ring 62 of the bearing member 6A is fixed to the case 10. In other words, the outer ring 62 of the first bearing member 601A is fitted and fixed to the input side (right side in FIG. 16) of the rotation axis Ax1 as seen from the gear body 22 on the inner peripheral surface of the case 10. Meanwhile, the outer ring 62 of the second bearing member 602A is fitted and fixed to the output side (left side in FIG. 16) of the rotation axis Ax1 as viewed from the gear body 22 on the inner circumferential surface of the case 10.

Furthermore, the end face of the case 10 on the input side (right side in FIG. 16) of the rotating shaft Ax1 is closed by a carrier flange 18, and the end face of the case 10 on the output side (left side in FIG. 16) of the rotating shaft Ax1 is closed by an output flange 19. Therefore, as shown in FIG. 16, parts such as the planetary gear 3 (first planetary gear 301 and second planetary gear 302), multiple outer pins 23, and eccentric bearing 5 are housed in the space surrounded by the case 10, carrier flange 18, and output flange 19.

In addition, the gear device 1A according to this embodiment further includes a retaining member 80 that is disposed inside the gear body 22 and holds the multiple outer pins 23 between the gear body 22 in the radial direction (diameter direction of the gear body 22). The retaining member 80 is disposed between the two planetary gears 3, the first planetary gear 301 and the second planetary gear 302. The retaining member 80 has multiple outer peripheral grooves 801 that hold the multiple outer pins 23 on its outer peripheral surface. That is, in this embodiment, the retaining member 80 provided in place of the support body 8 of the first embodiment functions as a "stopper" that suppresses the movement of the outer pins 23 in a direction away from the inner peripheral surface 221 of the gear body 22 by sandwiching the multiple outer pins 23 between the gear body 22. In short, each of the multiple outer pins 23 is restricted from moving in a direction away from the gear body 22 by contacting the outer peripheral surface of the retaining member 80, and is also restricted from moving in a circumferential direction around the rotation axis Ax1 by being fitted into the outer peripheral groove 801. In other words, the outer pin 23 is positioned by the retaining member 80 and the gear body 22 not only in the radial direction but also in the circumferential direction.

Therefore, rattle is unlikely to occur between the outer pin 23 and the retaining member 80 and the gear body 22, and even if a force acts on the outer pin 23 in a direction in which the outer teeth 31 pulls it out of the inner circumferential groove 223 when the inner teeth 21 (outer pin 23) and the outer teeth 31 mesh, the meshing between the inner teeth 21 and the outer teeth 31 is unlikely to become unstable. Therefore, the gear device 1A according to this embodiment has the advantage that the meshing between the inner teeth 21 and the outer teeth 31 is likely to be stable.

In the gear device 1A according to this embodiment, the internal gear 2 is an example of the "first gear" and the planetary gear 3 is an example of the "second gear". That is, the first gear is the internal gear 2 having an annular gear body 22 and a plurality of outer pins 23. The plurality of outer pins 23 are held in a rotatable state in a plurality of inner circumferential grooves 223 formed on the inner circumferential surface 221 of the gear body 22, forming the internal teeth 21. The second gear is the planetary gear 3 having the external teeth 31 that partially mesh with the internal teeth 21. In this gear device 1, the planetary gear 3 is rotated relative to the internal gear 2 by oscillating the planetary gear 3 about the rotation axis Ax1. In this embodiment, the inner surfaces of the plurality of inner circumferential grooves 223 with which at least the plurality of outer pins 23 as other components slide in contact are the sliding contact parts of the skeleton part 225 of the internal gear 2. Therefore, at least the inner surfaces (sliding contact parts) of the plurality of inner circumferential grooves 223 are covered with the coating layer 224.

The configuration of embodiment 2 (including the modified examples) can be adopted in appropriate combination with the various configurations (including the modified examples) described in embodiment 1.

(Embodiment 3)
As shown in Figures 17 to 20, the gear device 1C of this embodiment differs from the gear device 1 of embodiment 1 in that it includes a rigid internal gear 2C, a flexible external gear 3C, and a wave generator 4C.

In the gear device 1C according to this embodiment, an annular flexible external gear 3C is arranged inside an annular rigid internal gear 2C, and a wave generator 4C is arranged inside the flexible external gear 3C. The wave generator 4C bends the flexible external gear 3C into a non-circular shape, thereby partially meshing the external teeth 31C of the flexible external gear 3C with the internal teeth 21C of the rigid internal gear 2C. When the wave generator 4C rotates, the meshing position between the internal teeth 21C and the external teeth 31C moves in the circumferential direction of the rigid internal gear 2C, and a relative rotation according to the difference in the number of teeth between the flexible external gear 3C and the rigid internal gear 2C occurs between the two gears (rigid internal gear 2C and flexible external gear 3C). Here, if the rigid internal gear 2C is fixed, the flexible external gear 3C will rotate in accordance with the relative rotation of the two gears. As a result, the flexible external gear 3C produces a rotational output that is reduced at a relatively high reduction ratio depending on the difference in the number of teeth between the two gears.

The wave generator 4C, which causes the flexible external gear 3C to bend, has a non-circular cam 41C that is rotated around the input rotation axis Ax1, and a bearing 42C. The bearing 42C is disposed between the outer peripheral surface of the cam 41C and the inner peripheral surface 301C of the flexible external gear 3C. The inner ring 422C of the bearing 42C is fixed to the outer peripheral surface of the cam 41C, and the outer ring 421C of the bearing 42C is elastically deformed by being pressed by the cam 41C via the ball-shaped rolling body 423C. Here, since the outer ring 421C can rotate relative to the inner ring 422C by the rolling of the rolling body 423C, when the non-circular cam 41C rotates, the rotation of the inner ring 422C is not transmitted to the outer ring 421C, and a wave motion is generated in the external teeth 31C of the flexible external gear 3C that is pressed by the cam 41C. As a result of the wave motion of the external teeth 31C, the meshing position between the internal teeth 21C and the external teeth 31C moves in the circumferential direction of the rigid internal gear 2C as described above, and relative rotation occurs between the flexible external gear 3C and the rigid internal gear 2C.

In short, in this type of gear device 1C, a wave generator 4C having a bearing 42C flexes the flexible external gear 3C, and power is transmitted by meshing between the internal teeth 21C and the external teeth 31C.

More specifically, a cup-type strain wave gear device is shown as an example of the gear device 1C. That is, the gear device 1C according to this embodiment uses a flexible external gear 3C formed in a cup shape. The wave generator 4C is combined with the flexible external gear 3C so as to be housed within the cup-shaped flexible external gear 3C.

In the gear device 1C according to this embodiment, the input side rotation axis Ax1 and the output side rotation axis Ax2 are on the same straight line. In other words, the input side rotation axis Ax1 and the output side rotation axis Ax2 are coaxial. Here, the input side rotation axis Ax1 is the rotation center of the wave generator 4C to which the input rotation is applied, and the output side rotation axis Ax1 is the rotation center of the flexible external gear 3C that generates the output rotation. In other words, in the gear device 1C, an output rotation that is reduced in speed at a relatively high reduction ratio compared to the input rotation is obtained on the same axis.

The rigid internal gear 2C is also called a circular spline and is an annular part having internal teeth 21C. In this embodiment, the rigid internal gear 2C has an annular shape in which at least the inner peripheral surface is a perfect circle in a plan view. The inner peripheral surface of the annular rigid internal gear 2C is formed with internal teeth 21C along the circumferential direction of the rigid internal gear 2C. The multiple teeth constituting the internal teeth 21C all have the same shape and are provided at equal pitch over the entire circumferential area of the inner peripheral surface of the rigid internal gear 2C. In other words, the pitch circle of the internal teeth 21C is a perfect circle in a plan view. In addition, the rigid internal gear 2C has a predetermined thickness in the direction of the rotation axis Ax1. All of the internal teeth 21C are formed over the entire length of the rigid internal gear 2C in the thickness direction. All of the tooth traces of the internal teeth 21C are parallel to the rotation axis Ax1.

The flexible external gear 3C is also called a flex spline and is an annular part having external teeth 31C. In this embodiment, the flexible external gear 3C is a part formed in a cup shape from a relatively thin metal elastic body (metal plate). In other words, the flexible external gear 3C has flexibility due to its relatively small (thin) thickness. The flexible external gear 3C has a cup-shaped main body 32C. The main body 32C has a body 321C and a bottom 322C. The body 321C has a cylindrical shape in which at least the inner circumferential surface 301C is a perfect circle in a plan view when no elastic deformation occurs in the flexible external gear 3C. The central axis of the body 321C coincides with the rotation axis Ax1. The bottom 322C is disposed on one opening surface of the body 321C and has a disk shape that is a perfect circle in a plan view. The bottom 322C is disposed on the opening surface on the output side of the rotation axis Ax1, out of a pair of opening surfaces of the body 321C. As described above, the body 32C is realized in a bottomed cylindrical shape, that is, a cup shape, which is open to the input side of the rotation axis Ax1, by the entire body 321C and bottom 322C. In other words, an opening surface 35C is formed on the end surface opposite the bottom 322C in the direction of the rotation axis Ax1 of the flexible external gear 3C. In other words, the flexible external gear 3C is cylindrical with an opening surface 35C on one side of the tooth trace direction D1 (here, the input side of the rotation axis Ax1). In this embodiment, the body 321C and the bottom 322C are integrally formed from a single metal member, thereby realizing a seamless body 32C.

Here, the flexible external gear 3C is combined with the wave generator 4C such that the non-circular wave generator 4C is fitted inside the body 321C. As a result, the flexible external gear 3C elastically deforms into a non-circular shape when it receives an external force from the wave generator 4C in the radial direction (direction perpendicular to the rotation axis Ax1) from the inside to the outside. In the first comparative example of this embodiment, the flexible external gear 3C elastically deforms into an elliptical shape at the body 321C by combining the elliptical wave generator 4C with the flexible external gear 3C (see FIG. 18). In other words, a state in which no elastic deformation occurs in the flexible external gear 3C means a state in which the wave generator 4C is not combined with the flexible external gear 3C. Conversely, a state in which elastic deformation occurs in the flexible external gear 3C means a state in which the wave generator 4C is combined with the flexible external gear 3C.

More specifically, the wave generator 4C is fitted into the end of the inner circumferential surface 301C of the body 321C opposite to the bottom 322C (the input side of the rotation axis Ax1). In other words, the wave generator 4C is fitted into the end of the body 321C of the flexible external gear 3C on the opening surface 35C side in the direction of the rotation axis Ax1. Therefore, when elastic deformation occurs in the flexible external gear 3C, the end of the flexible external gear 3C on the opening surface 35C side in the direction of the rotation axis Ax1 is more deformed than the end on the bottom 322C side, and becomes closer to an elliptical shape. Due to such a difference in the amount of deformation in the direction of the rotation axis Ax1, when elastic deformation occurs in the flexible external gear 3C, the inner circumferential surface 301C of the body 321C of the flexible external gear 3C includes a tapered surface that is inclined with respect to the rotation axis Ax1.

In addition, at least at the end of the outer peripheral surface of the body 321C opposite to the bottom 322C (the input side of the rotation axis Ax1), the external teeth 31C are formed along the circumferential direction of the body 321C. In other words, the external teeth 31C are provided at least at the end of the body 321C of the flexible external gear 3C on the opening surface 35C side in the direction of the rotation axis Ax1. The multiple teeth constituting the external teeth 31C are all of the same shape and are provided at equal pitches over the entire circumferential area of the outer peripheral surface of the flexible external gear 3C. In other words, the pitch circle of the external teeth 31C is a perfect circle in a plan view when no elastic deformation occurs in the flexible external gear 3C. The external teeth 31C are formed only within a certain width range from the edge of the opening surface 35C side (the input side of the rotation axis Ax1) of the body 321C. Specifically, at least the portion of the body 321C where the wave generator 4C is fitted in the direction of the rotation axis Ax1 (the end portion on the opening surface 35C side) has external teeth 31C formed on the outer circumferential surface. The tooth traces of the external teeth 31C are all parallel to the rotation axis Ax1.

The flexible external gear 3C configured in this manner is placed inside the rigid internal gear 2C. Here, the flexible external gear 3C is combined with the rigid internal gear 2C so that only the end of the outer circumferential surface of the body 321C opposite the bottom 322C (the input side of the rotation axis Ax1) is inserted inside the rigid internal gear 2C. In other words, the flexible external gear 3C is inserted inside the rigid internal gear 2C at the part of the body 321C where the wave generator 4C is fitted (the end on the opening surface 35C side) in the direction of the rotation axis Ax1. Here, the external teeth 31C are formed on the outer circumferential surface of the flexible external gear 3C, and the internal teeth 21C are formed on the inner circumferential surface of the rigid internal gear 2C. Therefore, when the flexible external gear 3C is placed inside the rigid internal gear 2C, the external teeth 31C and the internal teeth 21C face each other.

Here, the number of teeth of the internal teeth 21C of the rigid internal gear 2C is 2N (N is a positive integer) more than the number of teeth of the external teeth 31C of the flexible external gear 3C. In this embodiment, as an example, N is "1", and the number of teeth (of the external teeth 31C) of the flexible external gear 3C is "2" more than the number of teeth (of the internal teeth 21C) of the rigid internal gear 2C. Such a difference in the number of teeth between the flexible external gear 3C and the rigid internal gear 2C defines the reduction ratio of the output rotation to the input rotation in the gear device 1C.

Here, in this embodiment, as an example, the relative positions of the flexible external gear 3C and the rigid internal gear 2C in the direction of the rotation axis Ax1 are set so that the center of the tooth trace direction D1 of the external teeth 31C and the center of the tooth trace direction D1 of the internal teeth 21C face each other. In other words, the positions of the centers of the tooth trace direction D1 of the external teeth 31C of the flexible external gear 3C and the internal teeth 21C of the rigid internal gear 2C are aligned to the same position in the direction of the rotation axis Ax1. Also, in this embodiment, the dimension (tooth width) of the tooth trace direction D1 of the external teeth 31C is larger than the dimension (tooth width) of the tooth trace direction D1 of the internal teeth 21C. Therefore, in the direction parallel to the rotation axis Ax1, the internal teeth 21C are contained within the range of the tooth trace of the external teeth 31C. In other words, the external teeth 31C protrude in at least one direction of the tooth trace direction D1 relative to the internal teeth 21C. In this embodiment, the external teeth 31C protrude in both directions of the tooth trace D1 (the input side and the output side of the rotation axis Ax1) relative to the internal teeth 21C.

Here, when no elastic deformation occurs in the flexible external gear 3C (when the wave generator 4C is not combined with the flexible external gear 3C), the pitch circle of the external teeth 31C, which form a perfect circle, is set to be slightly smaller than the pitch circle of the internal teeth 21C, which also form a perfect circle. In other words, when no elastic deformation occurs in the flexible external gear 3C, the external teeth 31C and the internal teeth 21C face each other with a gap between them and do not mesh with each other.

On the other hand, when elastic deformation occurs in the flexible external gear 3C (when the wave generator 4C is combined with the flexible external gear 3C), the body 321C bends in a non-circular shape, so that the external teeth 31C of the flexible external gear 3C partially mesh with the internal teeth 21C of the rigid internal gear 2C. In other words, in the first comparative example, the body 321C of the flexible external gear 3C (at least the end on the opening surface 35C side) is elastically deformed into an ellipse, so that the external teeth 31C located at both ends in the major axis direction of the ellipse mesh with the internal teeth 21C, as shown in FIG. 18. In other words, the major axis of the pitch circle of the external teeth 31C that draws an ellipse coincides with the diameter of the pitch circle of the internal teeth 21C that draws a perfect circle, and the minor axis of the pitch circle of the external teeth 31C that draws an ellipse is smaller than the diameter of the pitch circle of the internal teeth 21C that draws a perfect circle. In this way, when the flexible external gear 3C elastically deforms, some of the multiple teeth that make up the external teeth 31C mesh with some of the multiple teeth that make up the internal teeth 21C. As a result, in the gear device 1C, it is possible to mesh some of the external teeth 31C with some of the internal teeth 21C.

The wave generator 4C, also known as a wave generator, is a component that causes deflection in the flexible external gear 3C, generating wave motion in the external teeth 31C of the flexible external gear 3C. In the first comparative example of this embodiment, the wave generator 4C is a component whose outer periphery is non-circular in plan view, specifically, elliptical.

In the gear device 1C according to the present embodiment, the rigid internal gear 2C is an example of the "first gear", and the flexible external gear 3C is an example of the "second gear". That is, the first gear is an annular rigid internal gear 2C having internal teeth 21C. The second gear is an annular flexible external gear 3C having external teeth 31C and arranged inside the rigid internal gear 2C. This gear device 1C further includes a wave generator 4C arranged inside the flexible external gear 3C and causing deflection in the flexible external gear 3C. The gear device 1C deforms the flexible external gear 3C in accordance with the rotation of the wave generator 4C about the rotation axis Ax1, meshing a part of the external teeth 31C with a part of the internal teeth 21C, and rotating the flexible external gear 3C relative to the rigid internal gear 2C according to the difference in the number of teeth with the rigid internal gear 2C. Furthermore, of the skeleton 225 of the rigid internal gear 2C (first gear), at least the surface of the internal teeth 21C with which the external teeth 31C, which is another component, slides is covered with a coating layer 224.

In short, in this embodiment, the rigid internal gear 2C is an example of the "first gear", so the skeleton 225 made of aluminum (Al) is used as the base material of the rigid internal gear 2C. When the flexible external gear 3C elastically deforms into an elliptical shape, as described above, the external teeth 31C mesh with the internal teeth 21C at two locations on both ends of the long axis direction of the elliptical shape. In this way, at multiple meshing locations with the external teeth 31C on the internal teeth 21C, sliding contact occurs between the internal teeth 21C and the external teeth 31C. Therefore, in the rigid internal gear 2C, which is the first gear, the surface of the internal teeth 21C becomes a sliding contact location with another component (the external teeth 31C of the flexible external gear 3C), so the surface of the internal teeth 21C is covered with a coating layer 224 made of iron (Fe), for example.

As a modified example of the third embodiment, it is not essential that the first gear is a rigid internal gear 2C and the second gear is a flexible external gear 3C. For example, the first gear may be a flexible external gear 3C and the second gear may be a rigid internal gear 2C. In this case, the base material of the flexible external gear 3C forms the skeleton, and for example, the sliding contact area of the flexible external gear 3C with another component (wave generator 4C) is covered with a coating layer.

The configuration of embodiment 3 (including the modified examples) can be adopted in appropriate combination with the various configurations (including the modified examples) described in embodiment 1 or embodiment 2.

(summary)
As described above, the gear device (1, 1A, 1C) according to the first aspect includes a first gear and a second gear. The second gear rotates relative to the first gear by meshing with the first gear. The first gear has a skeleton portion (225) and a coating layer (224) having a specific gravity greater than that of the skeleton portion (225). At least a portion of the skeleton portion (225) that comes into sliding contact with another component is covered with the coating layer (224).

According to this embodiment, the skeleton portion (225) of the first gear itself is made of a material with a low specific gravity, so that even if it has a certain thickness, it is possible to keep the weight relatively small. On the other hand, the sliding contact portion of the skeleton portion (225) (with other parts) is covered with a coating layer (224) with a higher specific gravity than the skeleton portion (225), so that the wear resistance of the sliding contact portion can be increased and the strength of the first gear can be maintained. As a result, it is possible to realize a gear device (1, 1A, 1C) that is easy to reduce weight while maintaining its strength.

In the gear device (1, 1A, 1C) according to the second aspect, in the first aspect, the skeleton portion (225) has a higher thermal conductivity than the coating layer (224).

According to this embodiment, most of the first gear can be made up of a skeletal portion (225) with high thermal conductivity, improving the heat dissipation of the first gear.

In the gear device (1, 1A, 1C) according to the third aspect, in the first or second aspect, the coating layer (224) is a sprayed film having a different composition from the framework (225).

This embodiment makes it easier to form a coating layer (224) with a relatively large thickness.

In the gear device (1, 1A, 1C) according to the fourth aspect, in any of the first to third aspects, the first gear has a base layer (226) on the surface of the skeleton portion (225), and the coating layer (224) is laminated on the base layer (226).

According to this embodiment, the adhesion of the coating layer (224) to the skeletal portion (225) can be improved.

In the gear device (1, 1A, 1C) according to the fifth aspect, in the fourth aspect, the grain direction of the base layer (226) is a direction based on the sliding direction of other parts at the sliding contact area.

According to this embodiment, the adhesion of the coating layer (224) to the skeletal portion (225) can be improved.

In the gear device (1, 1A, 1C) according to the sixth aspect, in any one of the first to fifth aspects, the coating layer (224) has a thickness of 50 μm or more.

According to this embodiment, it is possible to prevent other parts from directly contacting the skeletal portion (225) at the sliding contact area, which makes it easier to suppress wear of the skeletal portion (225).

In the gear device (1, 1A, 1C) according to the seventh aspect, in any one of the first to sixth aspects, the first gear is an internal gear (2) and the second gear is a planetary gear (3). The internal gear (2) has an annular gear body (22) and a plurality of outer pins (23) that are rotatably held in a plurality of inner circumferential grooves (223) formed on the inner circumferential surface (221) of the gear body (22). The planetary gear (3) has external teeth (31) that partially mesh with the internal teeth (21). The gear device (1, 1A, 1C) rotates the planetary gear (3) relative to the internal gear (2) by oscillating the planetary gear (3) about the rotation axis (Ax1). Of the skeleton portion (225) of the internal gear (2), at least the inner surfaces of the multiple inner circumferential grooves (223) with which the multiple outer pins (23) serving as other components slide and contact are covered with a coating layer (224).

This aspect makes it possible to realize an internally meshing planetary gear device (1, 1A, 1C) that is easy to reduce weight while maintaining strength.

In the gear device (1, 1A, 1C) according to the eighth aspect, in any one of the first to sixth aspects, the first gear is an annular rigid internal gear (2C) having internal teeth (21C), and the second gear is an annular flexible external gear (3C) having external teeth (31C) and arranged inside the rigid internal gear (2C). The gear device (1, 1A, 1C) further includes a wave generator (4C) arranged inside the flexible external gear (3C) and causing a deflection in the flexible external gear (3C). The gear device (1, 1A, 1C) is a gear device that deforms the flexible external gear (3C) in response to the rotation of the wave generator (4C) about the rotation axis (Ax1), meshes a part of the external teeth (31C) with a part of the internal teeth (21C), and rotates the flexible external gear (3C) relative to the rigid internal gear (2C) according to the difference in the number of teeth with the rigid internal gear (2C). Of the skeleton part (225) of the rigid internal gear, at least the surface of the internal teeth (21C) with which the external teeth (31C) as another component slides is covered with a coating layer (224).

According to this aspect, it is possible to realize a gear device (1, 1A, 1C) that is easy to reduce weight while maintaining strength in a wave gear device.

The manufacturing method of the gear device according to the ninth aspect is a manufacturing method of the gear device according to any one of the first to eighth aspects, and includes a thermal spraying process for forming a coating layer (224) by thermal spraying on at least a part of the skeleton portion (225) of the first gear.

According to this aspect, the skeleton portion (225) of the first gear itself is made of a material with a low specific gravity, so that even if it has a certain thickness, it is possible to keep the weight relatively small. On the other hand, the sliding contact portion of the skeleton portion (225) (with other parts) is formed by thermal spraying and is covered with a coating layer (224) with a higher specific gravity than the skeleton portion (225), so that the wear resistance of the sliding contact portion can be increased and the strength of the first gear can be maintained. As a result, it is possible to realize a manufacturing method for a gear device (1, 1A, 1C) that can easily be made lighter while maintaining its strength.

The configurations according to the second to eighth aspects are not essential to the gear device (1, 1A, 1C) and may be omitted as appropriate.

1, 1A (internal meshing planetary) gear device 1C (wave) gear device 2 Internal gear (first gear)
2C Rigid internal gear (first gear)
3 Planetary gear (second gear)
3C Flexible external gear (second gear)
4C Wave generator 21, 21C Internal teeth 22 Gear body 23 Outer pin (other parts)
31, 31C External teeth (other parts)
221 (of gear body) inner peripheral surface 223 inner peripheral groove 224 coating layer 225 skeleton portion 226 base layer Ax1 rotating shaft

Claims (9)

A first gear;
a second gear that rotates relatively to the first gear by meshing with the first gear,
the first gear has a skeleton portion and a coating layer having a specific gravity greater than that of the skeleton portion,
At least a portion of the skeleton that comes into sliding contact with another component is covered with the coating layer.
Gear mechanism. The skeleton has a higher thermal conductivity than the coating layer.
2. The gear arrangement of claim 1. The coating layer is a sprayed film having a different composition from that of the skeleton.
A gear device according to claim 1 or 2. The first gear has a base layer on a surface of the skeleton portion, and the coating layer is laminated on the base layer.
A gear device according to claim 1 or 2. The grain direction of the base layer is a direction based on the sliding direction of the other component at the sliding contact portion.
5. A gear arrangement according to claim 4. The coating layer has a thickness of 50 μm or more.
A gear device according to claim 1 or 2. The first gear is an internal gear having an annular gear body and a plurality of outer pins that are rotatably held in a plurality of inner circumferential grooves formed on an inner circumferential surface of the gear body and that constitute internal teeth,
The second gear is a planetary gear having external teeth that partially mesh with the internal teeth,
The planetary gear is rotated relative to the internal gear by swinging the planetary gear about a rotation axis,
In the skeleton portion of the internal gear, at least inner surfaces of the plurality of inner circumferential grooves with which the plurality of outer pins as the other components slide and come into contact are covered with the coating layer.
A gear device according to claim 1 or 2. The first gear is an annular rigid internal gear having internal teeth,
The second gear is an annular flexible external gear having external teeth and disposed inside the rigid internal gear,
Further, a wave generator is disposed inside the flexible external gear and causes the flexible external gear to deflect,
a gear device in which the flexible external gear is deformed in accordance with rotation of the wave generator about a rotation axis, a portion of the external teeth is meshed with a portion of the internal teeth, and the flexible external gear is rotated relative to the rigid internal gear in accordance with a difference in the number of teeth between the flexible external gear and the rigid internal gear,
At least a surface of the internal teeth of the skeleton portion of the rigid internal gear with which the external teeth as the other component come into sliding contact is covered with the coating layer.
A gear device according to claim 1 or 2. A method for manufacturing a gear device according to any one of claims 1 to 8, comprising the steps of:
a thermal spraying step of forming the coating layer on at least a part of the skeleton portion of the first gear by thermal spraying,
A method for manufacturing a gear device.

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