WO2023071232A1

WO2023071232A1 - Harmonic gear device and manufacturing method therefor, joint device for robot, and gear component

Info

Publication number: WO2023071232A1
Application number: PCT/CN2022/099489
Authority: WO
Inventors: 王刚; 林文捷; 峯岸清次; 伊佐地毅; 郭子铭
Original assignee: 美的集团股份有限公司; 广东极亚精机科技有限公司; 广东美的制冷设备有限公司
Priority date: 2021-10-25
Filing date: 2022-06-17
Publication date: 2023-05-04
Also published as: CN118251554A; JP2023063962A; JP7490627B2

Abstract

A harmonic gear device (1), comprising a rigid internal gear (2), a flexible external gear (3), and a wave generator (4). The wave generator (4) has a non-circular cam (41), which is rotationally driven by taking a rotation axis as the center, and a bearing (42), which is fitted to an outer side of the cam. The harmonic gear device (1) makes the flexible external gear (3) deform as the cam (41) rotates, such that some external teeth (31) mesh with some internal teeth (21), thereby making the flexible external gear (3) carry out relative rotation relative to the rigid internal gear (2) according to the difference in the number of teeth between the flexible external gear and the rigid internal gear (2). A first region (R1) of an inner peripheral face (301) of the flexible external gear (3) that is located on the back side of the external teeth (31) has a surface roughness less than that of a second region (R2) apart from the first region (R1). Further provided are a manufacturing method for the harmonic gear device; a joint device for a robot, which device comprises the harmonic gear device; and a gear component serving as a flexible external gear of the harmonic gear device.

Description

Harmonic gear device, method of manufacturing harmonic gear device, joint device for robot, and gear part

Cross References to Related Applications

This application is based on Japanese patent application No. 2021-174098 and filing date of October 25, 2021, and claims the priority of this Japanese patent application. The entire content of this Japanese patent application is hereby incorporated into this application as refer to.

technical field

The present disclosure generally relates to a harmonic gear device, a manufacturing method of a harmonic gear device, a joint device for a robot, and a gear part, and more particularly, to a harmonic gear device including a rigid internal gear, a flexible external gear, and a wave generator, A method of manufacturing a harmonic gear device, a joint device for a robot, and a gear part.

Background technique

Patent Document 1 discloses that the surface treatment of a flexible external gear in a harmonic gear device (flexural mesh gear device) is carried out by nitriding treatment.

The harmonic gear device has: a ring-shaped rigid internal gear; a cup-shaped flexible external gear arranged inside; and an elliptical wave generator embedded in the inside. The flexible external gear includes a cylindrical body and external teeth formed on the outer peripheral surface of the body. The flexible external gear is bent into an ellipse by the wave generator, and portions of the external teeth located at both ends of the ellipse in the major axis direction mesh with internal teeth formed on the inner peripheral surface of the rigid internal gear.

When the wave generator is rotated by a motor, etc., the meshing position of the two gears moves in the circumferential direction, and a relative rotation corresponding to the difference in the number of teeth of the inner teeth and the outer teeth (2N (N is a positive integer)) is generated between the two gears. Here, when the rigid internal gear side is fixed, it is possible to obtain a rotational output greatly reduced in accordance with the difference in the number of teeth of both gears from the flexible external gear side.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-59153

Contents of the invention

The technical problem to be solved by the invention

However, in the above-mentioned harmonic gear device, since the wave generator fitted inside the flexible external gear rotates, especially if it is used for a long period of time, there is a possibility of micro Dynamic wear (fretting wear). If fretting wear occurs, it will lead to roughness of the surface, rust caused by wear powder, and damage to the wave generator (bearing) caused by wear powder entering the inside of the wave generator, which may affect the harmonic gear. device reliability.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a harmonic gear device, a method of manufacturing a harmonic gear device, a robot joint device, and a gear component that are less prone to reliability degradation.

Solutions for technical problems

A harmonic gear device according to one aspect of the present disclosure includes a rigid internal gear, a flexible external gear, and a wave generator. The rigid internal gear is an annular member having internal teeth. The flexible external gear is an annular member having external teeth and arranged inside the rigid internal gear. The wave generator has a non-circular cam that is rotationally driven about a rotating shaft, and a bearing mounted on the outer side of the cam. The wave generator is arranged inside the flexible external gear and makes the flexible external gear deflect. The harmonic gear device deforms the flexible external gear as the cam rotates, and a part of the external teeth meshes with a part of the internal teeth, so that the flexible external gear conforms to the The rigid internal gear rotates relative to the rigid internal gear due to the difference in the number of teeth of the rigid internal gear. Among the inner peripheral surfaces of the flexible external gear, a first region located on the back side of the external teeth has a smaller surface roughness than a second region other than the first region.

A method of manufacturing a harmonic gear device according to an aspect of the present disclosure includes: a preparatory step of preparing a base material to be a base of the flexible external gear; and a plastic working step of forming the inner peripheral surface of the base material by plastic working. first area.

A joint device for a robot according to one aspect of the present disclosure includes: the harmonic gear unit; a first member fixed to the rigid internal gear; and a second member fixed to the flexible external gear.

A gear member according to one aspect of the present disclosure is used as the flexible external gear of the harmonic gear device.

Invention effect

According to the present disclosure, there is an advantage in that it is possible to provide a harmonic gear device, a method of manufacturing a harmonic gear device, a joint device for a robot, and a gear component that are less prone to reliability degradation.

Description of drawings

FIG. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to an embodiment.

FIG. 1B is an enlarged view of area Z1 of FIG. 1A .

Fig. 2A is a schematic diagram of the above-mentioned harmonic gear device viewed from the input side of the rotary shaft.

FIG. 2B is an enlarged view of area Z1 of FIG. 2A .

FIG. 3A is a schematic exploded perspective view of the above harmonic gear device viewed from the output side of the rotary shaft.

Fig. 3B is a schematic exploded perspective view of the above-mentioned harmonic gear device viewed from the input side of the rotary shaft.

FIG. 4 is a cross-sectional view showing a schematic configuration of an actuator including the above-mentioned harmonic gear device.

FIG. 5 is an enlarged schematic cross-sectional view of a main part of a range corresponding to FIG. 1B .

6A is a schematic diagram showing the surface state of the inner peripheral surface of the flexible external gear in the zone Z1 of FIG. 5 .

6B is a schematic diagram showing the surface state of the inner peripheral surface of the flexible external gear in the zone Z2 of FIG. 5 .

FIG. 7 is an enlarged schematic view of a region Z1 in FIG. 2B .

FIG. 8A is a schematic diagram showing the surface state of the external teeth in the zone Z1 of FIG. 7 .

FIG. 8B is a schematic diagram showing the surface state of the external teeth in the zone Z2 of FIG. 7 .

FIG. 9 is a conceptual explanatory diagram for illustrating the operation of the long-axis side and the short-axis side of the tapered surface of the above-mentioned harmonic gear device.

Fig. 10 is a cross-sectional view showing an example of a robot using the above-mentioned harmonic gear device.

FIG. 11 is a schematic explanatory view showing the process of machining the inner peripheral surface of the flexible external gear of the harmonic gear device.

12A is a schematic cross-sectional view showing a rolling roller and a chuck member used for machining the inner peripheral surface of the flexible external gear of the harmonic gear device.

12B is a schematic side view showing a rolling roller and a chuck member used for machining the inner peripheral surface of the flexible external gear of the harmonic gear device.

Fig. 13A is a schematic cross-sectional view showing a chuck member of a modified example.

FIG. 13B is a schematic enlarged view of a region Z1 in FIG. 13A .

Fig. 14 is a schematic explanatory view showing the process of machining the external teeth of the flexible external gear of the harmonic gear device.

15A is a schematic cross-sectional view showing a hob used for machining the external teeth of the flexible external gear of the harmonic gear device.

15B is a schematic side view showing a hob used for machining the external teeth of the flexible external gear of the harmonic gear device.

16A is a schematic cross-sectional view showing a tool used for machining the external teeth of the flexible external gear of the harmonic gear device.

16B is a schematic side view showing a tool used for machining the external teeth of the flexible external gear of the harmonic gear device.

17A is a cross-sectional view illustrating a schematic configuration of a harmonic gear device according to a modified example of the embodiment.

FIG. 17B is an enlarged view of the area Z1 of FIG. 17A .

Fig. 18A is a schematic diagram showing a main part of the harmonic gear device according to the embodiment.

FIG. 18B is a schematic view showing the surface state of the internal teeth in the region Z1 of FIG. 18A .

FIG. 18C is a schematic diagram showing the surface state of the internal teeth in the zone Z2 of FIG. 18B .

Detailed ways

(1) Summary

Hereinafter, the outline of the harmonic gear device 1 according to the present embodiment will be described with reference to FIGS. 1A to 5 . The drawings referred to in the present disclosure are all schematic diagrams, and the respective ratios of the sizes and thicknesses of the constituent elements in the drawings are not necessarily limited to reflect actual dimensional ratios. For example, in FIGS. 2A to 3B , the tooth shapes, dimensions, and number of teeth of the internal teeth 21 and the external teeth 31 are schematically shown for illustration only, and are not intended to be limited to the illustrated shapes.

A harmonic gear device 1 according to the present embodiment is a gear device including a rigid internal gear 2 , a flexible external gear 3 , and a wave generator 4 . In this harmonic gear device 1 , an annular flexible external gear 3 is arranged inside an annular rigid internal gear 2 , and a wave generator 4 is further arranged inside the flexible external gear 3 . The wave generator 4 locally meshes the external teeth 31 of the flexible external gear 3 with the internal teeth 21 of the rigid internal gear 2 by bending the flexible external gear 3 into a non-circular shape. When the wave generator 4 rotates, the meshing position of the internal teeth 21 and the external teeth 31 moves along the circumferential direction of the rigid internal gear 2, and a flexible force is generated between the two gears (the rigid internal gear 2 and the flexible external gear 3). The external gear 3 rotates relative to the rigid internal gear 2 according to the difference in the number of teeth. Here, if the rigid internal gear 2 is fixed, the flexible external gear 3 rotates with the relative rotation of both gears. As a result, a rotational output decelerated by a relatively high reduction ratio according to the difference in the number of teeth of both gears can be obtained from the flexible external gear 3 .

In addition, the wave generator 4 that flexes the flexible external gear 3 has a non-circular cam 41 and a bearing 42 that are driven to rotate around the input side rotation axis Ax1 (see FIG. 1A ). The bearing 42 is disposed between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the flexible external gear 3 . The inner ring 422 of the bearing 42 is fixed on the outer peripheral surface 411 of the cam 41 , and the outer ring 421 of the bearing 42 is pressed by the cam 41 via the ball-shaped rolling element 423 to be elastically deformed. Here, since the outer ring 421 can rotate relative to the inner ring 422 due to the rolling of the rolling elements 423, when the non-circular cam 41 rotates, the rotation of the inner ring 422 is not transmitted to the outer ring 421, but is transmitted by the cam. 41 The external teeth 31 of the pressed flexible external gear 3 undergo harmonic motion. Due to the harmonic motion of the external teeth 31, the meshing position of the internal teeth 21 and the external teeth 31 moves along the circumferential direction of the rigid internal gear 2 as described above, so that the flexible external gear 3 and the rigid internal gear 2 generate contact. relative rotation.

In short, in such a harmonic gear device 1 , the wave generator 4 having the bearing 42 achieves power transmission through the meshing of the internal teeth 21 and the external teeth 31 while flexing the flexible external gear 3 .

In such a harmonic gear device 1, especially if it is used for a long period of time, along with the rotation of the wave generator 4 embedded inside the flexible external gear 3, the contact portion between the flexible external gear 3 and the wave generator 4 may Fretting wear occurs. If fretting wear occurs, it will cause roughness of the surface, rust caused by wear powder, and damage to the wave generator 4 (bearing 42) caused by wear powder entering the inside of the wave generator 4, which may affect the harmonic. The reliability of the wave gear device 1.

As an example, if the deformation followability of the flexible external gear 3 is hindered due to surface roughness or rust, the rotation of the wave generator 4 requires additional energy, resulting in a decrease in power transmission efficiency or due to the load applied to the bearing 42. shortened lifespan due to increase. In addition, when the wear powder enters the bearing 42, the indentation caused by the bite of the wear powder into the outer ring 421 or the inner ring 422 of the bearing 42 and the rolling element 423 is the origin, and the outer ring 421, the inner ring 422 and the rolling elements The surface of any of the bodies 423 may be damaged. Such damage (exfoliation of the surface origin type) leads to deterioration of the quality, characteristics, etc. of the harmonic gear device 1 , and consequently leads to a decrease in the reliability of the harmonic gear device 1 . Therefore, the harmonic gear device 1 according to the present embodiment suppresses the occurrence of fretting wear by the following configuration, so that a decrease in reliability hardly occurs.

That is, as shown in FIGS. 1A to 3B , the harmonic gear device 1 of the present embodiment includes an annular rigid internal gear 2 having internal teeth 21 , an annular flexible external gear 3 having external teeth 31 , and a wave generating device 4. The flexible external gear 3 is disposed inside the rigid internal gear 2 . The wave generator 4 is disposed inside the flexible external gear 3 and causes the flexible external gear 3 to bend. The wave generator 4 has: a non-circular cam 41 that is driven to rotate about the rotation axis Ax1; and a bearing 42 that is attached to the outside of the cam 41 . The harmonic gear unit 1 deforms the flexible external gear 3 along with the rotation of the cam 41, so that a part of the external teeth 31 meshes with a part of the internal teeth 21, so that the flexible external gear 3 and the rigid internal gear 2 have a different number of teeth. And relative rotation is performed with respect to the rigid internal gear 2 . Here, as shown in FIG. 5 , the first region R1 located on the back side of the external teeth 31 in the inner peripheral surface 301 of the flexible external gear 3 has a higher surface roughness than the second region R2 other than the first region R1 . Small.

According to this aspect, the contact portion of the flexible external gear 3 with the bearing 42 has a surface state in which it is easy to maintain a state covered with the lubricant Lb1 (see FIG. 4 ). In short, in the inner peripheral surface 301 of the flexible external gear 3, the back side of the external teeth 31 pressed by the bearing 42 is provided with the first region R1 whose surface roughness is smaller than the other surface roughness. It is easy to maintain the state covered with lubricant Lb1.

That is, the harmonic gear device 1 of the present embodiment suppresses the occurrence of fretting wear by preventing "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3 . Further, by providing the first region R1 having a surface roughness smaller than the second region R2 on the back side of the external teeth 31 in the inner peripheral surface 301 of the flexible external gear 3, the flexible external gear 3 and the wave The contact portion of the generator 4 maintains sufficient lubricant Lb1. As a result, the surface of the contact portion of the flexible external gear 3 with the bearing 42 (outer ring 421 ) is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. Therefore, in the harmonic gear device 1 of the present embodiment, it is difficult to cause troubles caused by fretting wear between (the outer ring 421 of) the bearing 42 and the flexible external gear 3 , and it is possible to provide reliability Descending harmonic gearing 1. Furthermore, since the harmonic gear device 1 of the present embodiment is less prone to reliability degradation even when used for a long period of time, the transmission efficiency of the harmonic gear device 1 is improved, its life is extended, and its performance is improved.

In addition, in such a harmonic gear device 1 , the external teeth 31 located at both ends of the long-axis direction of the flexible external gear 3 bent into an ellipse (non-circular shape) press the internal surface of the rigid internal gear 2 like a wedge. tooth 21, whereby the external tooth 31 meshes with the internal tooth 21 to obtain a rotational output. Therefore, in a state where the external teeth 31 are pressed against the internal teeth 21 , the external teeth 31 and the internal teeth 21 rub against each other particularly at the contact portion between the external teeth 31 and the internal teeth 21 . Therefore, loss due to friction occurs at the contact portion of the external teeth 31 and the internal teeth 21, resulting in roughness of the surface, rust due to wear powder, and wave generation due to the penetration of wear powder into the inside of the wave generator 4. Damage to the gear 4 may affect the reliability of the harmonic gear device 1 .

That is, if the loss caused by the friction between the external teeth 31 and the internal teeth 21, or the roughness of the surface or the generation of rust hinders the deformation followability of the flexible external gear 3, the rotation of the wave generator 4 requires additional time. energy, resulting in a decrease in power transmission efficiency. Therefore, the harmonic gear device 1 of the present embodiment reduces the friction between the external teeth 31 and the internal teeth 21 by the following configuration, thereby making it difficult to reduce the power transmission efficiency.

As shown in FIG. 2B , in the harmonic gear device 1 of the present embodiment, at least one of the external teeth 31 and the internal teeth 21 includes a rolling surface 300 . The rolling surface 300 is not formed by cutting metal crystal grains, but is formed by not cutting metal crystal grains (rolling processing). Therefore, the rolling surface 300 included in at least one of the external teeth 31 and the internal teeth 21 has a smooth surface state in which metal crystal grains are not sheared.

According to this state, since the friction between the external teeth 31 and the internal teeth 21 is reduced, the loss due to the friction between the external teeth 31 and the internal teeth 21 is reduced, making it difficult to reduce the power transmission efficiency of the harmonic gear device 1 . In addition, since surface roughness or rust caused by friction is suppressed, it is also difficult to hinder the deformation followability of the flexible external gear 3, and the rotation of the wave generator 4 is unlikely to require additional energy, thereby suppressing power transmission efficiency. Decline. As a result, it is possible to provide the harmonic gear device 1 in which a drop in power transmission efficiency hardly occurs.

The rolling surface 300 only needs to be provided on at least one of the outer teeth 31 and the inner teeth 21 . In this disclosure, when distinguishing the rolling surfaces provided on the external teeth 31 and the internal teeth 21 respectively, the rolling surface 300 provided on the external teeth 31 is referred to as the "first rolling surface", and the rolling surface provided on the internal teeth 21 is referred to as the "first rolling surface". The rolling surface 200 (see FIG. 18A ) of the tooth 21 is called "second rolling surface". In this embodiment, as an example, the rolling surface 300 is provided only on the outer teeth 31 of the outer teeth 31 and the inner teeth 21 . In other words, in the present embodiment, the rolling surface 300 includes the “first rolling surface” provided on the external teeth 31 . On the other hand, the rolling surface (second rolling surface) on the side of the internal teeth 21 will be described in another embodiment.

In addition, as shown in FIG. 4 , the harmonic gear device 1 according to the present embodiment constitutes an actuator 100 together with a drive source 101 and an output unit 102 . In other words, the actuator 100 of the present embodiment includes the harmonic gear device 1 , the drive source 101 and the output unit 102 . The drive source 101 rotates the wave generator 4 . The output unit 102 takes out the rotational force of either the rigid internal gear 2 or the flexible external gear 3 as an output.

In addition, as shown in FIG. 4 , the harmonic gear device 1 of this embodiment constitutes a joint device 130 for a robot together with a first member 131 and a second member 132 . In other words, the robot joint device 130 of this embodiment includes the harmonic gear device 1 , the first member 131 and the second member 132 . The first member 131 is fixed to the rigid internal gear 2 . The second member 132 is fixed to the flexible external gear 3 . As a result, in the harmonic gear device 1 , the flexible external gear 3 rotates relative to the rigid internal gear 2 , whereby the first member 131 and the second member 132 in the robot joint device 130 relatively rotate.

According to the robot joint device 130 of the present embodiment, there is an advantage that the reliability of the harmonic gear device 1 is less likely to be lowered. In addition, according to the robot joint device 130 of the present embodiment, there is an advantage in that a drop in power transmission efficiency hardly occurs.

(2) Definition

The term "annular" as used in the present disclosure means a shape such as a circle (ring) that forms a space (region) surrounded on the inside at least when viewed from above, and is not limited to a circular shape (circle) that is a perfect circle when viewed from above. Ring), for example, oval shape and polygonal shape etc. are also possible. Furthermore, for example, a shape such as a cup-shaped flexible external gear 3 may have a bottom 322 , and if the body portion 321 is annular, it may be called a "ring-shaped" flexible external gear 3 .

The "rigidity" mentioned in the present disclosure refers to the property of an object to resist deformation when an external force is applied to the object and the object is about to deform. In other words, a rigid object is difficult to deform even when an external force is applied. In addition, "flexibility" mentioned in the present disclosure refers to the property that an object elastically deforms (bends) when an external force is applied to the object. In other words, a flexible object tends to deform elastically when an external force is applied. Therefore, "rigid" and "flexible" have opposite meanings.

Particularly in the present disclosure, "rigidity" of the rigid internal gear 2 and "flexibility" of the flexible external gear 3 are used in relative meanings. That is, the "rigidity" of the rigid internal gear 2 means that the rigid internal gear 2 has relatively high rigidity at least compared with the flexible external gear 3 , that is, the rigid internal gear 2 is hardly deformed even if an external force is applied to the rigid internal gear 2 . Similarly, the "flexibility" of the flexible external gear 3 means that at least compared with the rigid internal gear 2, the flexible external gear 3 has relatively high flexibility, that is to say, the flexible external gear 3 is easily elastic when an external force is applied. out of shape.

In addition, in this disclosure, one side of the rotation axis Ax1 (the right side in FIG. 1A ) is sometimes referred to as an “input side”, and the other side of the rotation axis Ax1 (the left side in FIG. 1A ) is sometimes referred to as an “output side”. ". That is, in the example of FIG. 1A , the flexible external gear 3 has the opening surface 35 on the "input side" of the rotation axis Ax1. However, the terms "input side" and "output side" are merely labels for explanation, and do not mean to limit the positional relationship between the input and output viewed from the harmonic gear device 1 .

The "non-circular shape" mentioned in the present disclosure refers to a shape that is not a perfect circle, and includes, for example, an oval shape, an oblong shape, and the like. As an example in this embodiment, the non-circular cam 41 of the wave generator 4 has an elliptical shape. That is, in the present embodiment, the wave generator 4 bends the flexible external gear 3 into an elliptical shape.

The "elliptical shape" mentioned in this disclosure refers to the entire shape in which a perfect circle is flattened so that the intersection point of the major axis and the minor axis orthogonal to each other is located at the center, and is not limited to the relationship between two fixed points on a plane. The curve formed by the set of points whose sum of distance is constant is called "ellipse" in mathematics. That is to say, the cam 41 in the present embodiment can be a curved line formed by a collection of points whose distances from two fixed points on a plane are constant as a mathematical "ellipse", or it can be a mathematical "ellipse". The "ellipse" above is an ellipse like an oblong. As described above, the drawings referred to in the present disclosure are all schematic diagrams, and the respective ratios of sizes and thicknesses of the constituent elements in the drawings are not necessarily limited to reflect actual dimensional ratios. Therefore, for example, in FIG. 2A , the shape of the cam 41 of the wave generator 4 is a slightly larger elliptical shape, but the actual shape of the cam 41 is not intended to be limited.

The "axis of rotation" used in this disclosure refers to a virtual axis (straight line) that becomes the center of the rotational motion of the rotating body. That is, the rotation axis Ax1 is a virtual axis without a real body. The wave generator 4 rotates around the rotation axis Ax1.

The "internal teeth" and "external teeth" mentioned in the present disclosure respectively refer to a collection (group) of a plurality of "teeth" rather than a single "teeth". That is, the internal teeth 21 of the rigid internal gear 2 are constituted by a collection of a plurality of teeth formed on the inner peripheral surface of the rigid internal gear 2 . Similarly, the external teeth 31 of the flexible external gear 3 are composed of a set of teeth formed on the outer peripheral surface of the flexible external gear 3 .

The "parallel" mentioned in this disclosure refers to the situation that as long as two straight lines on a plane are extended to any position and do not intersect, that is to say, except that the angle between the two is strictly 0 degrees (or 180 degrees) Except for some cases, the angle between the two is in the relationship of an error range that converges to a few degrees (for example, less than 10 degrees) relative to 0 degrees. Similarly, the "orthogonal" mentioned in this disclosure means that the angle between the two converges to a few degrees (for example, less than 10 degrees) relative to 90 degrees, except that the angle between the two intersects strictly at 90 degrees. relationship to the margin of error.

(3) Composition

Hereinafter, detailed configurations of the harmonic gear device 1 , the actuator 100 , and the robot joint device 130 according to the present embodiment will be described with reference to FIGS. 1A to 4 .

FIG. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device 1 , and FIG. 1B is an enlarged view of a region Z1 in FIG. 1A . FIG. 2A is a schematic view of the harmonic gear device 1 viewed from the input side of the rotation axis Ax1 (the right side of FIG. 1A ), and FIG. 2B is an enlarged view of a region Z1 in FIG. 2A . FIG. 3A is a schematic exploded perspective view of the harmonic gear device 1 viewed from the output side of the rotation axis Ax1 (the left side in FIG. 1A ). FIG. 3B is a schematic exploded perspective view of the harmonic gear device 1 viewed from the input side of the rotary axis Ax1. 4 is a cross-sectional view showing a schematic configuration of the actuator 100 including the harmonic gear device 1 and the robot joint device 130 .

(3.1) Harmonic gear device

As described above, the harmonic gear device 1 of the present embodiment includes the rigid internal gear 2 , the flexible external gear 3 and the wave generator 4 . In this embodiment, the materials of the rigid internal gear 2, the flexible external gear 3, and the wave generator 4, which are the structural elements of the harmonic gear device 1, are stainless steel, cast iron, carbon steel for mechanical structure, chrome-molybdenum steel, phosphorus Metals such as bronze or aluminum bronze. The metal mentioned here includes metals subjected to surface treatment such as nitriding treatment.

In addition, in this embodiment, as an example of the harmonic gear device 1 , a cup-shaped wave speed reduction device is illustrated. That is, the cup-shaped flexible external gear 3 is used in the harmonic gear device 1 of the present embodiment. The wave generator 4 is combined with the flexible external gear 3 so as to be accommodated in the cup-shaped flexible external gear 3 .

In addition, as an example in this embodiment, the harmonic gear unit 1 is used in a state where the rigid internal gear 2 is fixed to the input side case 111 (see FIG. 4 ) and the output side case 112 (see FIG. 4 ). Accordingly, the flexible external gear 3 relatively rotates with respect to the fixed member (input-side housing 111 and the like) along with the relative rotation of the rigid internal gear 2 and the flexible external gear 3 .

Further, in the present embodiment, when the harmonic gear device 1 is used as the actuator 100, by applying a rotational force as an input to the wave generator 4, it is possible to extract a rotational force as an output from the flexible external gear 3. rotational force. That is, the harmonic gear device 1 operates with the rotation of the wave generator 4 as an input rotation and with the rotation of the flexible external gear 3 as an output rotation. Accordingly, in the harmonic gear device 1 , it is possible to obtain an output rotation decelerated by a high reduction ratio relative to the input rotation.

Further, in the harmonic gear device 1 of the present embodiment, the input side rotation axis Ax1 and the output side rotation axis Ax2 are on the same straight line. In other words, the rotation axis Ax1 on the input side and the rotation axis Ax2 on the output side are coaxial. Here, the rotation axis Ax1 on the input side is the rotation center of the wave generator 4 to which the input rotation is applied, and the rotation axis Ax1 on the output side is the rotation center of the flexible external gear 3 which generates the output rotation. That is, in the harmonic gear device 1 , on the same axis, an output rotation decelerated by a high reduction ratio relative to the input rotation can be obtained.

The rigid internal gear 2 is also called a circular spline, and is an annular member having internal teeth 21 . In the present embodiment, the rigid internal gear 2 has an annular shape in which at least the inner peripheral surface is a perfect circle in plan view. On the inner peripheral surface of the annular rigid internal gear 2 , internal teeth 21 are formed along the circumferential direction of the rigid internal gear 2 . The plurality of teeth constituting the internal teeth 21 are all of the same shape and are provided at equal intervals over the entire area of the inner peripheral surface of the rigid internal gear 2 in the circumferential direction. That is to say, the pitch circle of the internal teeth 21 is a perfect circle in plan view. In addition, the rigid internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. Internal teeth 21 are formed over the entire length of the rigid internal gear 2 in the thickness direction. The tooth directions of the internal teeth 21 are all parallel to the rotation axis Ax1.

As described above, the rigid internal gear 2 is fixed to the input-side housing 111 (see FIG. 4 ), the output-side housing 112 (see FIG. 4 ), and the like. Therefore, a plurality of fixing holes 22 for fixing are formed in the rigid internal gear 2 (see FIGS. 3A and 3B ).

The flexible external gear 3 is also called a flex spline, and is an annular member having external teeth 31 . In the present embodiment, the flexible external gear 3 is formed into a cup shape using a relatively thin metal elastic body (metal plate). That is, the flexible external gear 3 has flexibility due to its relatively small (thin) thickness. The flexible external gear 3 has a cup-shaped body portion 32 . The main body part 32 has a body part 321 and a bottom part 322 . In a state where the flexible external gear 3 is not elastically deformed, at least the inner peripheral surface 301 of the trunk portion 321 has a cylindrical shape that is a perfect circle in plan view. The central axis of the body part 321 coincides with the rotation axis Ax1. The bottom portion 322 is disposed on one opening surface of the trunk portion 321 and has a disc shape that is a perfect circle in plan view. The bottom portion 322 is disposed on the opening surface near the output side of the rotation axis Ax1 among the pair of opening surfaces of the body portion 321 . As described above, the body part 32 has a bottomed cylindrical cup shape that is open on the input side of the rotation axis Ax1 by the body part 321 and the bottom part 322 as a whole. In other words, the opening surface 35 is formed on the end surface opposite to the bottom portion 322 in the direction of the rotation axis Ax1 of the flexible external gear 3 . That is, the flexible external gear 3 has a cylindrical shape having an opening surface 35 on one side in the tooth direction D1 (here, the input side of the rotation axis Ax1). In the present embodiment, the trunk portion 321 and the bottom portion 322 are integrally formed of one metal member, whereby a seamless main body portion 32 can be realized.

Here, the wave generator 4 and the flexible external gear 3 are combined so that the non-circular (elliptical) wave generator 4 is fitted inside the trunk portion 321 . Accordingly, the flexible external gear 3 receives an external force in the radial direction (direction perpendicular to the rotation axis Ax1 ) from the wave generator 4 from the inside toward the outside, thereby being elastically deformed into a non-circular shape. In this embodiment, by combining the wave generator 4 with the flexible external gear 3, the body portion 321 of the flexible external gear 3 is elastically deformed into an elliptical shape. That is, the state where the flexible external gear 3 is not elastically deformed refers to the state where the wave generator 4 is not combined with the flexible external gear 3 . On the contrary, the elastically deformed state of the flexible external gear 3 refers to the combined state of the wave generator 4 and the flexible external gear 3 .

More specifically, the wave generator 4 is fitted into an end portion of the inner peripheral surface 301 of the trunk portion 321 on the side opposite to the bottom portion 322 (input side of the rotation axis Ax1 ). In other words, the wave generator 4 is fitted into the end portion on the opening surface 35 side in the direction of the rotation axis Ax1 of the body portion 321 of the flexible external gear 3 . Therefore, in the state where the flexible external gear 3 is elastically deformed, the end of the flexible external gear 3 on the opening surface 35 side in the direction of the rotation axis Ax1 deforms more than the end on the bottom 322 side, and becomes closer to the flexible external gear 3 . The shape of the oval shape. Due to such a difference in the amount of deformation in the direction of the rotation axis Ax1, in the state where the flexible external gear 3 is elastically deformed, the inner peripheral surface 301 of the body portion 321 of the flexible external gear 3 includes an inclination with respect to the rotation axis Ax1. The tapered surface 302 (see Figure 9).

In addition, external teeth 31 are formed along the circumferential direction of the body portion 321 at least at an end portion on the side opposite to the bottom portion 322 (input side of the rotation axis Ax1 ) of the outer peripheral surface of the body portion 321 . In other words, the external teeth 31 are provided at least at an end portion on the opening surface 35 side in the direction of the rotation axis Ax1 in the body portion 321 of the flexible external gear 3 . The plurality of teeth constituting the external teeth 31 all have the same shape and are provided at equal intervals over the entire area in the circumferential direction of the outer peripheral surface of the flexible external gear 3 . That is, the pitch circles of the external teeth 31 are perfect circles in plan view when the flexible external gear 3 is not elastically deformed. The external teeth 31 are formed only within a certain width range from the end edge of the trunk portion 321 on the opening surface 35 side (the input side of the rotation axis Ax1 ). Specifically, external teeth 31 are formed on the outer peripheral surface of at least a portion (end portion on the side of the opening surface 35 ) into which the wave generator 4 is fitted in the direction of the rotation axis Ax1 in the trunk portion 321 . The tooth directions of the external teeth 31 are all parallel to the rotation axis Ax1.

In short, in the harmonic gear device 1 of the present embodiment, any tooth direction of the internal teeth 21 of the rigid internal gear 2 and the external teeth 31 of the flexible external gear 3 is parallel to the rotation axis Ax1. Therefore, in the present embodiment, the "tooth direction D1" is a direction parallel to the rotation axis Ax1. Moreover, the dimension of the tooth direction D1 of the internal teeth 21 is the tooth width of the internal teeth 21, and similarly, the dimension of the tooth direction D1 of the external teeth 31 is the tooth width of the external teeth 31, so the tooth direction D1 is the same as the tooth width direction. righteous.

As described above, in the present embodiment, the rotation of the flexible external gear 3 is taken out as the output rotation. Therefore, the output unit 102 of the actuator 100 is attached to the flexible external gear 3 (see FIG. 4 ). A plurality of mounting holes 33 for mounting a shaft serving as the output unit 102 are formed in the bottom portion 322 of the flexible external gear 3 . Further, a penetrating hole 34 is formed at a central portion of the bottom portion 322 . The wall around the through hole 34 in the bottom 322 is thicker than other parts of the bottom 322 .

The flexible external gear 3 configured in this way is disposed inside the rigid internal gear 2 . Here, the flexible external gear 3 is connected to the rigid internal gear 2 so that only the end portion on the side opposite to the bottom 322 (the input side of the rotation axis Ax1 ) of the outer peripheral surface of the body portion 321 is inserted into the rigid internal gear 2 . 2 to combine. That is, the portion (the end portion on the side of the opening surface 35 ) into which the wave generator 4 is fitted in the direction of the rotation axis Ax1 of the body portion 321 of the flexible external gear 3 is inserted inside the rigid internal gear 2 . Here, external teeth 31 are formed on the outer peripheral surface of the flexible external gear 3 , and internal teeth 21 are formed on the inner peripheral surface of the rigid internal gear 2 . Therefore, in a state where the flexible external gear 3 is arranged inside the rigid internal gear 2 , the external teeth 31 and the internal teeth 21 face each other.

Here, the number of internal teeth 21 of the rigid internal gear 2 is 2N greater than the number of external teeth 31 of the flexible external gear 3 (N is a positive integer). As an example of this embodiment, N is "1", and the number of teeth of the flexible external gear 3 (of the external teeth 31 ) is "2" larger than the number of teeth of the rigid internal gear 2 (of the internal teeth 21 ). The difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation relative to the input rotation in the harmonic gear device 1 .

Here, in this embodiment, as an example, as shown in FIGS. 1A and 1B , the rotation axis Ax1 is set so that the center of the outer tooth 31 in the tooth direction D1 faces the center of the inner tooth 21 in the tooth direction D1. The relative position of the flexible external gear 3 and the rigid internal gear 2 in the direction of . That is, in the external teeth 31 of the flexible external gear 3 and the internal teeth 21 of the rigid internal gear 2 , the positions of the centers in the tooth direction D1 are aligned with the same position in the direction of the rotation axis Ax1 . In addition, in the present embodiment, the dimension (tooth width) of the external teeth 31 in the tooth direction D1 is larger than the dimension (tooth width) of the internal teeth 21 in the tooth direction D1. Therefore, the internal teeth 21 converge within the range of the tooth direction of the external teeth 31 in a direction parallel to the rotation axis Ax1. In other words, the external teeth 31 protrude to at least one side in the tooth direction D1 relative to the internal teeth 21 . In the present embodiment, the external teeth 31 protrude toward both sides (the input side and the output side of the rotation axis Ax1 ) in the tooth direction D1 with respect to the internal teeth 21 .

Here, in a state in which the flexible external gear 3 is not elastically deformed (a state in which the flexible external gear 3 is not combined with the wave generator 4), the pitch circles of the external teeth 31 that draw a perfect circle are set to be larger than those drawn in the same way. The pitch circle of the round internal teeth 21 is one circle smaller. That is, in a state where the flexible external gear 3 is not elastically deformed, the external teeth 31 and the internal teeth 21 face each other with gaps therebetween, and are not in mesh with each other.

On the other hand, in the state where the flexible external gear 3 is elastically deformed (the wave generator 4 and the flexible external gear 3 are combined), since the trunk part 321 is bent into an elliptical shape (non-circular shape), the flexure The external teeth 31 of the rigid external gear 3 partially mesh with the internal teeth 21 of the rigid internal gear 2 . That is, as shown in FIG. 2A , the body portion 321 (at least the end portion on the opening surface 35 side) of the flexible external gear 3 is elastically deformed into an elliptical shape, whereby the external teeth located at both ends of the elliptical shape in the major axis direction 31 meshes with the internal teeth 21. In other words, the major diameter of the pitch circle of the elliptical external teeth 31 coincides with the diameter of the pitch circle of the perfect circular internal teeth 21, and the minor diameter of the pitch circle of the elliptical external teeth 31 is smaller than that of the perfect circular internal teeth 21. The diameter of the pitch circle is small. In this way, when the flexible external gear 3 is elastically deformed, some of the plurality of teeth constituting the external teeth 31 mesh with some of the plurality of teeth constituting the internal teeth 21 . From the results, in the harmonic gear unit 1 , a part of the external teeth 31 can be meshed with a part of the internal teeth 21 .

The wave generator 4 is also called a wave generator (wave generator), which is a component that makes the flexible external gear 3 deflect, thereby causing the external teeth 31 of the flexible external gear 3 to generate harmonic motion. In the present embodiment, the wave generator 4 has a non-circular outer peripheral shape, specifically an elliptical shape in plan view.

The wave generator 4 has a cam 41 having a non-circular shape (here, an elliptical shape) and a bearing 42 fitted to the outer periphery of the cam 41 . That is, the cam 41 and the bearing 42 are combined such that the non-circular (ellipse) cam 41 is fitted inside the inner ring 422 of the bearing 42 . As a result, the bearing 42 receives an external force from the cam 41 in the radial direction (direction perpendicular to the rotation axis Ax1) from the inner side toward the outer side of the inner ring 422, and is elastically deformed into a non-circular shape. That is, the state where the bearing 42 is not elastically deformed refers to the state where the cam 41 is not combined with the bearing 42 . On the contrary, the elastically deformed state of the bearing 42 refers to the combined state of the cam 41 and the bearing 42 .

The cam 41 is a member having a non-circular shape (here, an elliptical shape) that is rotationally driven around the input-side rotational axis Ax1. The cam 41 has an outer peripheral surface 411 (see FIG. 1B ), and at least the outer peripheral surface 411 is formed of an elliptical metal plate in plan view. The cam 41 has a predetermined thickness in the direction of the rotation axis Ax1 (that is, the tooth direction D1). Thus, the cam 41 has rigidity equivalent to that of the rigid internal gear 2 . However, the thickness of the cam 41 is smaller (thinner) than that of the rigid internal gear 2 . As described above, in the present embodiment, the rotation of the wave generator 4 is used as the input rotation. Therefore, the input unit 103 of the actuator 100 is attached to the wave generator 4 (see FIG. 4 ). A cam hole 43 for attaching a shaft serving as the input unit 103 is formed at the center of the cam 41 of the wave generator 4 .

The bearing 42 has an outer ring 421 , an inner ring 422 and a plurality of rolling elements 423 . In the present embodiment, as an example, the bearing 42 is constituted by a deep groove ball bearing using spherical balls as the rolling elements 423 .

Both the outer ring 421 and the inner ring 422 are annular members. Both the outer ring 421 and the inner ring 422 are annular members formed using a thin metal elastic body (metal plate). That is to say, both the outer ring 421 and the inner ring 422 have flexibility due to their relatively small (thin) thickness. In the present embodiment, both the outer ring 421 and the inner ring 422 have an annular shape that is perfectly circular in plan view when the bearing 42 is not elastically deformed (the cam 41 is not combined with the bearing 42 ). The inner ring 422 is one turn smaller than the outer ring 421 and is disposed inside the outer ring 421 . Here, since the inner diameter of the outer ring 421 is larger than the outer diameter of the inner ring 422 , a gap is generated between the inner peripheral surface 425 of the outer ring 421 and the outer peripheral surface of the inner ring 422 .

A plurality of rolling elements 423 are disposed in a gap between the outer ring 421 and the inner ring 422 . The plurality of rolling elements 423 are arranged along the circumferential direction of the outer ring 421 . The plurality of rolling elements 423 are all metal balls (balls) of the same shape, and are arranged at equal intervals over the entire area of the outer ring 421 in the circumferential direction. Although not particularly shown here, the bearing 42 further has a cage, and a plurality of rolling elements 423 are held between the outer ring 421 and the inner ring 422 by the cage.

In addition, in this embodiment, as an example, the dimensions in the width direction (direction parallel to the rotation axis Ax1 ) of the outer ring 421 and the inner ring 422 are the same as the thickness of the cam 41 . That is, the dimensions in the width direction of the outer ring 421 and the inner ring 422 are smaller than the thickness of the rigid internal gear 2 .

With this structure of the bearing 42 , the cam 41 is combined with the bearing 42 , whereby the inner ring 422 of the bearing 42 is fixed to the cam 41 , and the inner ring 422 is elastically deformed into an elliptical shape similar to the outer peripheral shape of the cam 41 . At this time, the outer ring 421 of the bearing 42 is elastically deformed into an elliptical shape by being pressed by the inner ring 422 via the plurality of rolling elements 423 . Accordingly, both the outer ring 421 and the inner ring 422 of the bearing 42 are elastically deformed into an elliptical shape. In this way, in a state where the bearing 42 is elastically deformed (a state where the cam 41 and the bearing 42 are combined), the outer ring 421 and the inner ring 422 have elliptical shapes similar to each other.

Even in the state where the bearing 42 is elastically deformed, since a plurality of rolling elements 423 are interposed between the outer ring 421 and the inner ring 422 , the gap between the outer ring 421 and the inner ring 422 is maintained over the entire circumference of the outer ring 421 is roughly constant. In this state, the outer ring 421 can rotate relative to the inner ring 422 by the rolling of the plurality of rolling elements 423 between the outer ring 421 and the inner ring 422 . Therefore, in the state where the bearing 42 is elastically deformed, when the cam 41 rotates around the rotation axis Ax1, the rotation of the cam 41 is not transmitted to the outer ring 421, but the elastic deformation of the inner ring 422 is transmitted through a plurality of rolling elements 423. to the outer ring 421 . That is, in the wave generator 4, when the cam 41 rotates about the rotation axis Ax1, the outer ring 421 is elastically deformed so that the major axis of the ellipse model imitated by the outer ring 421 rotates about the rotation axis Ax1. . Therefore, as the wave generator 4 as a whole, the outer peripheral shape of the wave generator 4 having an elliptical shape viewed from the input side of the rotation axis Ax1 is accompanied by a cam so that the major axis rotates around the rotation axis Ax1. 41 rotations vary.

The wave generator 4 configured in this way is disposed inside the flexible external gear 3 . Here, the flexible external gear 3 is combined with the wave generator 4 so that only the end portion on the inner peripheral surface 301 of the trunk portion 321 on the side opposite to the bottom 322 (opening surface 35 side) is fitted to the wave generator 4 . At this time, the bearing 42 of the wave generator 4 is arranged between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the flexible external gear 3 . Here, the outer diameter of the outer ring 421 in the state where the bearing 42 is not elastically deformed (the state where the cam 41 is not combined with the bearing 42) is the same as that of the flexible external gear 3 (body part 321) in the same state where the elastic deformation is not generated. same inner diameter. Therefore, the outer peripheral surface 424 (see FIG. 5 ) of the outer ring 421 in the wave generator 4 is in contact with the inner peripheral surface 301 of the flexible external gear 3 over the entire circumference of the bearing 42 in the circumferential direction. Accordingly, in a state where the flexible external gear 3 is elastically deformed (a state where the wave generator 4 is combined with the flexible external gear 3 ), the trunk portion 321 is bent into an elliptical shape (non-circular shape). In this state, the flexible external gear 3 is fixed to the outer ring 421 of the bearing 42 .

However, since only the flexible external gear 3 and the wave generator 4 are fitted, the flexible external gear 3 and the outer ring 421 of the bearing 42 are not completely fixed. Therefore, as described above, a gap X1 is generated between the flexible external gear 3 and the outer ring 421 fitted inside the flexible external gear 3 (refer to FIG. 1B ). Strictly speaking, the diameter of the outer peripheral surface 424 of the outer ring 421 is slightly smaller than the diameter of the inner peripheral surface 301 of the flexible external gear 3, so the gap X1 between the outer ring 421 and the flexible external gear 3 will not be completely filled. , creating a gap X1 at least locally. In addition, there is also the influence of the gap X1, the outer ring 421 and the flexible external gear 3 are elastically deformed as the cam 41 of the wave generator 4 rotates, and relative rotation may occur between the outer ring 421 and the flexible external gear 3 . This relative rotation is, for example, a few thousandths or a few hundredths of the rotation speed of the cam 41. However, the relative friction between the outer ring 421 and the flexible external gear 3 due to such relative rotation is fretting wear. one reason.

The "gap" in the present disclosure refers to a space that may be generated between opposing surfaces of two objects, and a gap may be generated between the two objects even if the two objects are not separated. In other words, even if two objects are in contact, there is a possibility that a gap may be generated between the two objects although it is small. Between the flexible external gear 3 and the outer ring 421 fitted inside the flexible external gear 3 , a gap X1 is formed between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 that face each other. However, since the outer peripheral surface 424 of the outer ring 421 is basically in contact with the inner peripheral surface 301 of the flexible external gear 3, there is no large gap X1 therebetween. Therefore, the gap X1 between the outer ring 421 and the flexible external gear 3 is a small gap that can be locally generated between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 . As an example, a microscopic gap X1 is formed between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible external gear 3 to the extent that the lubricant Lb1 can penetrate.

As shown in FIG. 2A, in the harmonic gear device 1 configured as above, the body part 321 of the flexible external gear 3 is bent into an elliptical shape (non-circular shape), so that the external teeth 31 of the flexible external gear 3 and the rigid The internal teeth 21 of the internal gear 2 mesh locally. That is, when (the trunk portion 321 of) the flexible external gear 3 is elastically deformed into an elliptical shape, two external teeth 31 corresponding to both ends of the elliptical shape in the long-axis direction mesh with the internal teeth 21 . Moreover, when the cam 41 rotates around the rotation axis Ax1, the rotation of the cam 41 is not transmitted to the outer ring 421 and the flexible external gear 3, while the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 and the flexible outer gear 3 via a plurality of rolling elements 423. Flexible external gear 3. Therefore, the outer peripheral shape of the elliptical flexible external gear 3 viewed from the input side of the rotation axis Ax1 changes with the rotation of the cam 41 so that the major axis rotates around the rotation axis Ax1 .

As a result, harmonic motion occurs in the external teeth 31 formed on the outer peripheral surface of the flexible external gear 3 . Since the harmonic motion of the external teeth 31 occurs, the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the rigid internal gear 2 , thereby generating relative rotation between the flexible external gear 3 and the rigid internal gear 2 . That is, since the external teeth 31 mesh with the internal teeth 21 at both ends in the direction of the long axis of the ellipse formed by the flexible external gear 3 (the body part 321 of the flexible external gear), the rotation axis passes through the long axis of the ellipse. Ax1 rotates around the center to move the meshing position of the internal teeth 21 and the external teeth 31 . In this way, in the harmonic gear device 1 according to the present embodiment, the flexible external gear 3 is deformed with the rotation of the wave generator 4 centered on the rotation axis Ax1, so that a part of the external teeth 31 are aligned with the internal teeth. 21, so that the flexible external gear 3 rotates according to the difference in the number of teeth of the rigid internal gear 2.

Also, as described above, in the harmonic gear device 1 , the difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation relative to the input rotation in the harmonic gear device 1 . That is, when the number of teeth of the rigid internal gear 2 is "V1" and the number of teeth of the flexible external gear 3 is "V2", the speed reduction ratio R1 is expressed by the following formula 1.

R1=V2/(V1-V2)...(Formula 1)

In short, the smaller the tooth number difference (V1-V2) between the rigid internal gear 2 and the flexible external gear 3, the larger the reduction ratio R1. As an example, if the number of teeth V1 of the rigid internal gear 2 is "72" and the number of teeth V2 of the flexible external gear 3 is "70", and the difference between the number of teeth (V1-V2) is "2", then according to the above formula 1, the reduction ratio R1 is "35". In this case, when the cam 41 rotates one revolution (360 degrees) clockwise about the rotation axis Ax1 when viewed from the input side of the rotation axis Ax1, the flexible external gear 3 only rotates counterclockwise about the rotation axis Ax1. The number of teeth differs by an amount of "2" (ie, 10.3 degrees).

According to the harmonic gear device 1 according to the present embodiment, such a high reduction ratio R1 can be realized by a combination of one-stage gears (the rigid internal gear 2 and the flexible external gear 3 ).

In addition, the wave gear device 1 only needs to include at least a rigid internal gear 2, a flexible external gear 3, and a wave generator 4, and may also include, for example, the spline bushing 113 described in the column of "(3.2) Actuator". as a constituent element.

(3.2) Actuator

Next, the structure of the actuator 100 according to this embodiment will be described in more detail.

As shown in FIG. 4 , the actuator 100 according to the present embodiment includes the harmonic gear device 1 of the present embodiment, a drive source 101 , and an output unit 102 . That is, the actuator 100 includes a drive source 101 and an output portion 102 in addition to the rigid internal gear 2 , the flexible external gear 3 , and the wave generator 4 constituting the harmonic gear device 1 . In addition, the actuator 100 includes an input unit 103 , an input side case 111 , an output side case 112 , a spline bush 113 , and a spacer 114 in addition to the harmonic gear unit 1 , the drive source 101 , and the output unit 102 . , the first stopper 115 , the second stopper 116 and the mounting plate 117 . In addition, in this embodiment, the actuator 100 further includes

input side bearings

118 , 119 , an input side oil seal 120 ,

output side bearings

121 , 122 and an output side oil seal 123 .

In this embodiment, the materials of the components other than the driving source 101, the input side oil seal 120 and the output side oil seal 123 in the actuator 100 are stainless steel, cast iron, carbon steel for mechanical structure, chrome molybdenum steel, phosphor bronze or metals such as aluminum bronze.

The driving source 101 is a power generation source such as an electric motor (electric motor). The power generated by the driving source 101 is transmitted to the cam 41 of the wave generator 4 in the harmonic gear device 1 . Specifically, the drive source 101 is connected to a shaft serving as the input unit 103, and power generated by the drive source 101 is transmitted to the cam 41 via the input unit 103. Thereby, the drive source 101 can rotate the cam 41 .

The output unit 102 is a cylindrical shaft arranged along the rotation axis Ax2 on the output side. The central axis which is the axis of the output unit 102 coincides with the rotation axis Ax2. The output unit 102 is held rotatably around the rotation axis Ax2 by the output side case 112 . The output part 102 is fixed to the bottom 322 of the main body part 32 of the flexible external gear 3 , and rotates together with the flexible external gear 3 around the rotation axis Ax2 . That is, the output unit 102 takes out the rotational force of the flexible external gear 3 as an output.

The input unit 103 is a cylindrical shaft arranged along the rotation axis Ax1 on the input side. The central axis that is the axis of the input unit 103 coincides with the rotation axis Ax1. The input unit 103 is held by the input side case 111 so as to be rotatable about the rotation axis Ax1. The input unit 103 is attached to the cam 41 of the wave generator 4, and rotates together with the cam 41 around the rotation axis Ax1. That is, the input unit 103 transmits power (rotational force) generated by the driving source 101 to the cam 41 as an input. As described above, in this embodiment, the input side rotation axis Ax1 and the output side rotation axis Ax2 are located on the same straight line, so the input unit 103 and the output unit 102 are located on the same axis.

The input side housing 111 holds the input unit 103 rotatably via

input side bearings

118 and 119 . A pair of input-

side bearings

118 and 119 are arranged along the rotation axis Ax1 with a gap therebetween. In this embodiment, the shaft serving as the input part 103 penetrates the input side housing 111, and the front end of the input part 103 protrudes from the end surface (the right end surface in FIG. 4 ) on the input side of the rotation axis Ax1 of the input side housing 111. . The input side oil seal 120 closes the gap between the input side end surface of the rotation shaft Ax1 of the input side housing 111 and the input part 103 .

The output side housing 112 holds the output unit 102 rotatably via

output side bearings

121 and 122 . A pair of output-

side bearings

121 and 122 are arranged along the rotation axis Ax2 with a gap between them. In this embodiment, the shaft serving as the output part 102 penetrates the output side housing 112, and the front end part of the output part 102 protrudes from the output side end surface (the left end surface in FIG. 4 ) of the rotation axis Ax1 in the output side housing 112. . The output side oil seal 123 closes the gap between the output side end surface of the output side housing 112 on the output side of the rotation shaft Ax1 and the output portion 102 .

Here, as shown in FIG. 4 , the input-side housing 111 and the output-side housing 112 sandwich the rigid internal gear 2 of the harmonic gear unit 1 from both sides in the direction parallel to the rotation axis Ax1, that is, the tooth direction D1. state combined with each other. Specifically, the input side case 111 is in contact with the rigid internal gear 2 from the input side of the rotation axis Ax1 , and the output side case 112 is in contact with the rigid internal gear 2 from the output side of the rotation axis Ax1 . In this way, in the state where the rigid internal gear 2 is clamped between the input side case 111 and the output side case 112, the input side case 111 and the output side case are connected by screws (bolts) through a plurality of fixing holes 22 . The body 112 is fastened and fixed. Thereby, the input-side housing 111, the output-side housing 112, and the rigid internal gear 2 are integrated with each other. In other words, the rigid internal gear 2 constitutes the outer contour of the actuator 100 together with the input side housing 111 and the output side housing 112 .

The spline bushing 113 is a cylindrical member for connecting the shaft serving as the input portion 103 to the cam 41 . The spline bushing 113 is inserted into the cam hole 43 formed in the cam 41 , and the shaft serving as the input unit 103 is inserted into the spline bushing 113 so as to pass through the spline bushing 113 . Here, the movement of the spline bush 113 relative to both the cam 41 and the input portion 103 is restricted in the rotational direction centering on the rotational axis Ax1, and the spline bush 113 is restricted in the direction parallel to the rotational axis Ax1. 113 is at least movable relative to the input unit 103 . Thus, a spline connection structure can be realized as a connection structure between the input unit 103 and the cam 41 . Thereby, the cam 41 can move along the rotation axis Ax1 with respect to the input part 103, and rotates together with the input part 103 centering on the rotation axis Ax1.

The spacer 114 is a member that fills the gap between the spline bush 113 and the cam 41 . The first stopper 115 is a component that prevents the spline bushing 113 from coming off the cam 41 . The first stopper 115 is formed of, for example, an E-ring, and is attached to the spline bush 113 at a position on the input side of the rotation axis Ax1 when viewed from the cam 41 . The second stopper 116 is a member that prevents the input portion 103 from coming off the spline bush 113 . The second stopper 116 is composed of, for example, an E-ring, and is attached to the input portion 103 so as to be in contact with the spline bush 113 from the output side of the rotation shaft Ax1.

The mounting plate 117 is a member for mounting the shaft serving as the output portion 102 to the bottom portion 322 of the flexible external gear 3 . Specifically, in a state where the portion around the penetration hole 34 in the bottom portion 322 is sandwiched between the mounting plate 117 and the flange portion of the output unit 102, a plurality of mounting holes 33 are passed through using screws (bolts). Fasten and fix the mounting plate 117 and the flange portion. Thus, the shaft serving as the output unit 102 is fixed to the bottom portion 322 of the flexible external gear 3 .

However, in the present embodiment, the lubricant Lb1 is sealed inside the outer contour of the actuator 100 constituted by the input-side housing 111 , the output-side housing 112 , and the rigid internal gear 2 . That is, in the space surrounded by the input-side housing 111 , the output-side housing 112 , and the rigid internal gear 2 , there is a “lubricant reservoir” capable of storing the lubricant Lb1 in liquid or gel state.

That is, in the harmonic gear device 1 of the present embodiment, for example, a lubricant in a liquid or gel state is injected into the meshing portion of the internal teeth 21 and the external teeth 31 and between the outer ring 421 and the inner ring 422 of the bearing 42 . Lb1. As an example, the lubricant Lb1 is liquid lubricating oil (oil). Furthermore, when the harmonic gear unit 1 is used, the lubricant Lb1 also enters the gap X1 between the outer ring 421 (outer peripheral surface 424 ) of the bearing 42 and the flexible external gear 3 .

As shown in FIG. 4 , in this embodiment, as an example, the lubricant Lb1 is placed only on the lower portion of the outer contour of the actuator 100 (lead The lower part in the vertical direction) stores the lubricant Lb1. Therefore, with regard to the external teeth 31 and the outer ring 421 of the bearing 42 , etc., only a part in the rotational direction is immersed in the lubricant Lb1 in the state of FIG. 4 . When the output part 102 rotates from this state accompanying the rotation of the input part 103, the outer ring 421 and the flexible external gear 3 also rotate around the rotation axis Ax1, so as a result, the external teeth 31 and the outer ring 421 of the bearing 42 etc. Immerse in lubricant Lb1 in the direction of rotation.

(3.3) Joint device for robot

Next, the configuration of the robot joint device 130 according to this embodiment will be described in more detail.

As shown in FIG. 4 , the robot joint device 130 of this embodiment includes the harmonic gear device 1 of this embodiment, a first member 131 , and a second member 132 . That is, the robot joint device 130 includes a first member 131 and a second member 132 in addition to the rigid internal gear 2 , the flexible external gear 3 , and the wave generator 4 constituting the harmonic gear device 1 .

The first member 131 is a member fixed to the rigid internal gear 2, and the second member 132 is a member fixed to the flexible external gear 3. Therefore, in the harmonic gear device 1 , relative rotation occurs between the flexible external gear 3 and the rigid internal gear 2 , and thus relative rotation also occurs between the first member 131 and the second member 132 . In this way, the joint device 130 for a robot constitutes a connection site when two or more members (the first member 131 and the second member 132 ) are mutually movably connected (movably connected) via the harmonic gear device 1 .

Here, the first member 131 and the second member 132 may be directly or indirectly fixed to the rigid internal gear 2 and the flexible external gear 3 , respectively. In the example of FIG. 4 , the first member 131 is indirectly coupled (fixed) to the rigid internal gear 2 by being coupled to the output side case 112 . Likewise, the second member 132 is indirectly coupled (fixed) to the flexible external gear 3 by being coupled to the output portion 102 .

In the robot joint device 130 configured in this way, for example, when the cam 41 of the wave generator 4 rotates by the power generated by the drive source 101, a relative force is generated between the flexible external gear 3 and the rigid internal gear 2. rotate. And, with the relative rotation of the flexible external gear 3 and the rigid internal gear 2, between the first member 131 and the second member 132, the rotation axis Ax2 on the output side (coaxial with the rotation axis Ax1 on the input side) is The center produces relative rotation. As a result, according to the joint device 130 for a robot, the first member 131 and the second member 132 connected via the harmonic gear device 1 can be driven to rotate relative to each other around the rotation axis Ax1. Thus, the robot joint device 130 can realize various joint mechanisms of robots.

(4) Detailed structure of each part

Next, a more detailed configuration of each part of the harmonic gear device 1 of the present embodiment will be described in more detail with reference to FIGS. 1A to 2B and FIGS. 5 to 8B .

FIG. 5 is an enlarged schematic cross-sectional view of a main part of a range corresponding to FIG. 1B . 6A is a schematic diagram showing the surface state of the inner peripheral surface 301 of the flexible external gear 3 in the zone Z1 of FIG. Schematic diagram of the surface state. FIG. 7 is an enlarged schematic view of the area Z1 in FIG. 2B . Fig. 8A is a schematic view showing the surface state of the external teeth 31 in the zone Z1 of Fig. 7, and Fig. 8B is a schematic view showing the surface state of the external teeth 31 in the zone Z2 of Fig. 7 .

(4.1) Through hole

As shown in FIGS. 1A and 1B , in this embodiment, at least one of the outer ring 421 of the bearing 42 and the external teeth 31 of the flexible external gear 3 is provided with a through hole H1 along the radial direction. It penetrates in the direction and is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 . That is, the inner peripheral surface 425 (refer to FIG. 5 ) serving as the rolling surface of the plurality of rolling elements 423 in the outer ring 421 of the bearing 42 and the inner peripheral surface 425 (see FIG. 5 ) of the external teeth 31 of the flexible external gear 3 that are compatible with the internal teeth 21 At least one of the outer peripheral surfaces of the engaging surfaces communicates with the gap X1 through the through hole H1. Therefore, the lubricant Lb1 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1.

That is, the harmonic gear device 1 of the present embodiment can supply the lubricant Lb1 to the contact portion of the flexible external gear 3 and the wave generator 4 through the through hole H1 by providing the through hole H1, thereby maintaining sufficient Lubricant Lb1. As a result, "lubricant depletion" is prevented, the surface of the contact portion between the outer ring 421 and the flexible external gear 3 is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. As a result, in the harmonic gear device 1 of the present embodiment, troubles due to fretting wear between the outer ring 421 and the flexible external gear 3 are less likely to occur, and it is possible to provide harmonics with less reliability degradation. gear unit 1.

However, the through hole H1 may be provided in at least one of the outer ring 421 and the external teeth 31 of the flexible external gear 3 . In this disclosure, when distinguishing the through-holes H1 provided in the outer ring 421 and the external teeth 31 of the flexible external gear 3, the through-holes H1 provided in the outer ring 421 are referred to as "first through-holes". hole", the through-hole H2 (see FIG. 17B ) provided in the external tooth 31 of the flexible external gear 3 is referred to as a "second through-hole". In this embodiment, as an example, the through hole H1 is provided only in the outer ring 421 among the outer ring 421 and the external teeth 31 of the flexible external gear 3 . In other words, in this embodiment, the through hole H1 includes the “first through hole” provided in the outer ring 421 . On the other hand, the through-hole H2 (second through-hole) on the side of the external teeth 31 of the flexible external gear 3 will be described in "(8) Modification".

In addition, "penetrating along the radial direction" in this disclosure means penetrating along the radial direction, that is, the direction perpendicular to the rotation axis Ax1, that is, radially. That is, as long as the through hole H1 is provided in the outer ring 421 as in the present embodiment, the through hole H1 only needs to penetrate between the inner peripheral surface 425 and the outer peripheral surface 424 on both sides of the outer ring 421 in the radial direction. For example, It is also possible to be inclined with respect to the radial direction.

Here, first, the shape and size of the through-hole H1 in this embodiment will be described with reference to FIG. 5 .

The through hole H1 (first through hole) provided in the outer ring 421 penetrates the outer ring 421 in the radial direction. Thus, one opening surface of the through hole H1 faces the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other opening surface of the through hole H1 opens to the inner peripheral surface 425 of the outer ring 421 . Therefore, one end of the through hole H1 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other end is connected to the space between the inner peripheral surface 425 of the outer ring 421 and the outer peripheral surface of the inner ring 422 . Therefore, the space between the inner peripheral surface 425 of the outer ring 421 on which the plurality of rolling elements 423 are arranged and the outer peripheral surface of the inner ring 422 is separated from the gap X1 between the outer ring 421 and the flexible external gear 3 via the through hole H1. connected.

In addition, the through hole H1 is a circular hole having a circular (perfect circle) cross-sectional shape perpendicular to the radial direction. In this embodiment, as an example, the center line of the through hole H1 is parallel to the radial direction. That is, the through hole H1 is a hole extending straight in the radial direction from the inner peripheral surface 425 to the outer peripheral surface 424 of the outer ring 421 . Furthermore, the cross-sectional shape of the through hole H1 perpendicular to the radial direction is the same shape over the entire length of the through hole H1 in the radial direction. That is, a cylindrical space is formed inside the through hole H1.

Here, the diameter φ1 (see FIG. 5 ) of the through hole H1 is the smaller of 0.1 times or less and 1.0 mm or less the diameter φ2 (see FIG. 5 ) of each of the plurality of rolling elements 423 . The diameter φ1 of the through-hole H1 referred to here refers to the diameter of the through-hole H1 when the cross-sectional shape of the through-hole H1 is a perfect circle. It means the dimension of the minor axis direction of the through-hole H1. In this embodiment, as an example, the diameter φ1 of the through hole H1 is not more than 0.1 times the diameter φ2 of the rolling element 423 and not more than 1.0 mm. According to such a diameter φ1 of the through hole H1 , the lubricant Lb1 can be efficiently supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1 .

According to the structure described above, the space between the outer ring 421 and the inner ring 422 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1, so the space between the outer ring 421 and the inner ring 422 The lubricant Lb1 is supplied to the gap X1 through the through hole H1. In FIG. 5 , the flow of the lubricant Lb1 in the through hole H1 is schematically indicated by dotted arrows. In particular, when the bearing 42 operates and the plurality of rolling elements 423 rotate, the rolling elements 423 function as a pump and can send the lubricant Lb1 between the outer ring 421 and the inner ring 422 into the gap X1 through the through hole H1. As a result, "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3 is prevented, and the occurrence of fretting wear is easily suppressed.

In short, the harmonic gear device 1 of the present embodiment includes a pump structure for supplying the lubricant Lb1 to the gap X1 through the through hole H1 when the flexible external gear 3 rotates relative to the rigid internal gear 2 . When the flexible external gear 3 rotates relative to the rigid internal gear 2 , the plurality of rolling elements 423 of the bearing 42 roll in the circumferential direction of the outer ring 421 , so the plurality of rolling elements 423 function as a pump as described above. That is, a plurality of rolling elements 423 constitute a pump structure. In particular, in this embodiment, the rolling elements 423 roll in the space between the outer ring 421 and the inner ring 422 , thereby increasing the pressure in the space between the outer ring 421 and the inner ring 422 , so that the space between the outer ring 421 and the inner ring 422 increases. The lubricant Lb1 between the inner rings 422 is extruded to the side of the gap X1 through the through hole H1. In this way, the rolling elements 423 constitute a positive displacement pump such as a vane pump, and since the lubricant Lb1 is extruded to the gap X1 side with a sufficient pressure, it is easy to supply a sufficient amount of the lubricant Lb1 into the gap X1.

In addition, the opening surface of the through hole H1 on the inner peripheral surface 425 side of the outer ring 421 opens on the bottom surface of the rolling groove 426 formed in the inner peripheral surface 425 of the outer ring 421 . That is, a rolling groove 426 extending in the circumferential direction over the entire circumference of the outer ring 421 is formed at the center of the inner peripheral surface 425 of the outer ring 421 in the width direction (tooth direction D1), and the plurality of rolling elements 423 along the The rolling groove 426 rolls. Similar rolling grooves 427 are formed on the outer peripheral surface of the inner ring 422 , and a plurality of rolling elements 423 are sandwiched between these rolling

grooves

426 , 427 facing each other. Further, the through holes H1 are arranged in the range where the rolling grooves 426 are formed in the width direction (tooth direction D1) of the outer ring 421 so as to open to the bottom surface of the rolling grooves 426 of the outer ring 421 .

Furthermore, in this embodiment, the through-hole H1 is arrange|positioned at the same position as the center of the some rolling element 423 in the direction (tooth direction D1) parallel to the rotation axis Ax1. In other words, the through hole H1 is arranged at the center of the rolling groove 426 in the width direction (tooth direction D1 ) of the outer ring 421 . According to this configuration, the center of the plurality of rolling elements 423 passes through the opening surface of the through hole H1, and when the rolling elements 423 rotate, the rolling elements 423 efficiently function as a pump, and the lubricant Lb1 is easily sent into the gap through the through hole H1. X1. Furthermore, it can be seen that the outer ring 421 is in contact with the flexible external gear 3 mainly at both ends of the outer ring 421 in the width direction (tooth direction D1 ). Therefore, the through hole H1 is formed at the center of the outer ring 421 in the width direction (tooth direction D1), so that when the outer ring 421 comes into contact with the flexible external gear 3, the outer ring 421 is less likely to be damaged due to the through hole H1. decrease in strength.

Here, as shown in FIG. 5 , the rolling

grooves

426 and 427 are formed in an arc shape in cross section perpendicular to the circumferential direction of the outer ring 421 . In addition, the curvature of the circular arc of the cross-sectional shape of the rolling

grooves

426 and 427 is larger than the curvature of each of the plurality of rolling elements 423 . In other words, the radius of curvature of the circular arc of the cross-sectional shape of the rolling

grooves

426 and 427 is smaller than the radius of curvature of the rolling element 423 . Therefore, in a state where the plurality of rolling elements 423 are held between the rolling

grooves

426 and 427 in a sandwiched manner, a certain amount of clearance is ensured between the bottom surfaces of the rolling

grooves

426 and 427 and the surfaces of the respective rolling elements 423. . In other words, as shown in FIG. Both end edges in the direction D1) are supported at four points in total. However, since a load in a thrust direction (a direction parallel to the rotation axis Ax1 ) is actually applied relatively between the outer ring 421 and the inner ring 422 , the rolling elements 423 are supported by a pair of end edges that are obliquely opposed to each other.

Therefore, the opening surface of the through-hole H1 formed in the bottom surface of the rolling groove 426 faces the surface of the rolling element 423 via the gap. In short, in the present embodiment, in the radial direction, between the tracks of the plurality of rolling elements 423 and the opening surface of the outer ring 421 on the inner peripheral surface 425 side of the (first) through hole H1 provided in the outer ring 421 Ensure that there is a distance above the specified value. That is, even when the rolling element 423 exists at a position corresponding to the through hole H1, a distance (gap) equal to or greater than a predetermined value is ensured between the opening surface of the through hole H1 and the rolling element 423, and the through hole H1 Will not be closed by rolling elements 423. Accordingly, when the plurality of rolling elements 423 roll, even if the rolling elements 423 pass through the through-hole H1 , they do not collide with the opening edge of the through-hole H1 . As a result, when the rolling elements 423 pass through the through-hole H1, the impact caused by the rolling elements 423 colliding with the opening edge of the through-hole H1 can be avoided, and the outer ring 421, the rolling elements 423, etc. can be easily protected from the impact.

(4.2) Number and arrangement of through holes

Next, the number and arrangement of the through-holes H1 in this embodiment will be described with reference to FIGS. 2A and 2B .

As shown in FIG. 2A , the through holes H1 include a plurality of first through holes arranged in the outer ring 421 in the circumferential direction of the outer ring 421 . In this embodiment, the through-holes H1 are formed only by the first through-holes provided in the outer ring 421 , so all the through-holes H1 are arranged along the circumferential direction of the outer ring 421 . In this embodiment, as an example, three through-holes H1 are provided in the outer ring 421 . Therefore, the lubricant Lb1 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1 at a plurality of places (three places in the present embodiment) in the circumferential direction of the outer ring 421 . As a result, it becomes easier to supply the lubricant Lb1 over the entire area in the circumferential direction of the outer ring 421 at the gap X1, compared to the case where the through hole H1 is provided at only one location in the circumferential direction of the outer ring 421 .

Here, as shown in FIG. 2A , the interval P1 of the plurality of through holes H1 (first through holes) is a value other than a multiple of the interval P2 of the plurality of rolling elements 423 . In this embodiment, as an example, the bearing 42 has 26 rolling elements 423 and has three through-holes H1 in the outer ring 421 . In addition, the 26 rolling elements 423 and the three through holes H1 are provided at equal intervals (equal intervals) in the circumferential direction of the outer ring 421 . Therefore, the interval P1 of the three through holes H1 in the circumferential direction of the outer ring 421 is 120 degrees (= 360 degrees ÷ 3), and the interval P2 of the 26 rolling elements 423 in the circumferential direction of the outer ring 421 is 13.85 degrees (= 360 degrees ÷26). Here, the interval P1 is a value representing the distance between the centers of two through-holes H1 adjacent in the circumferential direction of the outer ring 421 by an angle around the rotation axis Ax1. The value of the distance between the centers of two rolling elements 423 adjacent in the circumferential direction of the ring 421 . In this embodiment, even if the interval P2 (13.85 degrees) of the plurality of rolling elements 423 is multiplied by any integer, the interval P1 (120 degrees) of the plurality of through-holes H1 does not match the interval P1 (120 degrees), so that the interval P1 cannot be separated. P2 divisible such values.

Accordingly, the rolling elements 423 do not simultaneously exist at positions corresponding to all the through-holes H1. That is, in a state where one rolling element 423 is located at a position corresponding to one through-hole H1, the rolling element 423 is not located at a position corresponding to the other two through-holes H1. Therefore, in the harmonic gear device 1 of this embodiment, it is possible to avoid relatively large impacts that may occur when a plurality of rolling elements 423 are simultaneously fitted (or pulled out) into a plurality of through-holes H1, and it is easy to protect the outer ring 421. And rolling elements 423 etc. from impact. In addition, the pump action by the rolling of the rolling elements 423 is also more efficient than when the rolling elements 423 are positioned on all the through holes H1.

(4.3) Surface condition of the inner peripheral surface of the flexible external gear

Next, the surface state of the inner peripheral surface 301 of the flexible external gear 3 according to this embodiment will be described with reference to FIGS. 5 , 6A, and 6B.

As described above, in the present embodiment, the first region R1 located on the back side of the external teeth 31 in the inner peripheral surface 301 of the flexible external gear 3 is formed to have a surface roughness higher than that of the second region other than the first region R1. R2 is small. That is, the inner peripheral surface 301 of the flexible external gear 3 includes a first region R1 and a second region R2 having different surface roughnesses. Furthermore, as shown in FIG. 5 , the first region R1 is provided on at least the back side of the external teeth 31 on the inner peripheral surface 301 . The surface roughness of the first region R1 is smaller than that of the second region R2, that is to say, the first region R1 has a smoother surface state. The bearing 42 of the wave generator 4 is in contact with the first region R1 thus provided on the back side of the external teeth 31 .

In short, a gap X1 is generated, although small, between the first region R1 on the inner peripheral surface 301 of the flexible external gear 3 and the outer ring 421 of the bearing 42 fitted inside the flexible external gear 3 . Occurrence of fretting wear at the contact portion between the flexible external gear 3 and the outer ring 421 is suppressed by allowing the lubricant Lb1 to penetrate into the gap X1. That is, in the present embodiment, the lubricant Lb1 is held between the first region R1 and the outer peripheral surface 424 (of the bearing 42 ) of the wave generator 4 . In addition, as in the first region R1, by making the inner peripheral surface 301 of the flexible external gear 3 into a partially smooth surface state, the lubricant Lb1 is likely to stay at the contact portion of the flexible external gear 3 with the wave generator 4 , sufficient lubricant Lb1 can be maintained at the contact site.

In addition, in the present embodiment, the first region R1 is provided over the entire region of the surface facing the outer peripheral surface 424 (of the bearing 42 ) of the wave generator 4 at least in a direction parallel to the rotation axis Ax1 (tooth direction D1 ). . That is, as shown in FIG. 5 , the entire region of the inner peripheral surface 301 of the flexible external gear 3 that faces the outer peripheral surface 424 of the bearing 42 has a smooth surface state as the first region R1 . As a result, the contact portion of the inner peripheral surface 301 of the flexible external gear 3 with the wave generator 4 is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed.

Here, the first region R1 is formed by, for example, not shearing metal crystal grains such as cutting but not shearing metal crystal grains (rolling). Therefore, the first region R1 provided on the inner peripheral surface 301 at least at the back side of the external teeth 31 has a smooth surface state in which metal crystal grains are not sheared. On the other hand, the second region R2 having a relatively large surface roughness is formed by shearing metal crystal grains such as cutting, grinding, or honing. Therefore, the second region R2 in the inner peripheral surface 301 has a surface state in which crystal grains of the metal are sheared. That is, in the present embodiment, the first region R1 is a rolling surface, and the second region R2 is a cutting surface. In this way, the surface roughness of the first region R1 and the second region R2 can be easily adjusted by employing different processes in the first region R1 and the second region R2.

In addition, the first region R1 is provided at an end edge of the inner peripheral surface 301 of the flexible external gear 3 on the opening surface 35 side in the direction of the rotation axis Ax1 . That is, in the present embodiment, the flexible external gear 3 has a cylindrical shape having an opening surface 35 on one side in the tooth direction D1 of the external teeth 31 (here, the input side of the rotation axis Ax1). The first region R1 is connected to the opening surface 35 . In this way, by providing the first region R1 at the end edge on the opening surface 35 side, when the wave generator 4 is fitted into the flexible external gear 3 from the opening surface 35 side, it is difficult for the wave generator 4 to catch on the flexible external gear 3. The inner peripheral surface 301 of the situation.

As shown in FIG. 6A , which is an enlarged part of the inner peripheral surface 301 of the flexible external gear 3 (region Z1 in FIG. 5 ), the first region R1 mainly has a smooth surface state in which crystal grains are not sheared. On the other hand, as shown in FIG. 6B , which enlarges a part of the inner peripheral surface 301 of the flexible external gear 3 (region Z2 in FIG. 5 ), the second region R2 mainly has a surface state in which crystal grains are sheared. In the present embodiment, as an example, the "surface roughness" is a value obtained from the arithmetic mean roughness (Ra) in a direction (tooth direction D1 ) parallel to the rotation axis Ax1 . As shown in FIGS. 6A and 6B, when the unit length W1 (0.25 mm as an example) of the tooth direction D1 and the unit length Y1 (1 μm as an example) in the direction of longitudinal magnification are specified, the first region R1 The surface roughness is smaller than that of the second region R2.

Here, the surface roughness of the first region R1 is preferably not less than 1/40 and not more than 1/10 of the surface roughness of the second region R2. The surface roughness of the first region R1 is not limited to 1/40 times or more than the surface roughness of the second region R2, for example, it may be 1/80 times or more, 1/50 times or more, 1/30 times or more, or 1/16 times. above and so on. Likewise, the surface roughness of the first region R1 is not limited to 1/10 or less than the surface roughness of the second region R2, for example, it may be 1/2 or less, 1/5 or less, 1/12 or less, or 1/10 or less. /16 times or less, etc. In this way, since the surface roughness of the first region R1 is sufficiently smaller than the surface roughness of the second region R2, the lubricant Lb1 tends to stay in the first region R1. As an example, the surface roughness of the first region R1 is preferably not less than Ra0.01 and not more than Ra0.1, and in this case, it is preferably not more than 1/10 times the surface roughness (Ra) of the second region R2.

That is, in the second region R2 formed by performing processing such as cutting, grinding, or honing on the inner peripheral surface 301 of the flexible external gear 3 to shear the crystal grains of the metal structure, a grain boundary is generated. Scaly "burrs" (protrusions). On the other hand, in the first region R1 formed by subjecting the inner peripheral surface 301 of the flexible external gear 3 to the inner peripheral surface 301 such as rolling without shearing the crystal grains of the metal structure, such scaly spots do not occur. "burrs" to achieve a smooth surface state. However, the "surface roughness" is not limited to the arithmetic mean roughness (Ra) in the direction parallel to the rotation axis Ax1 (tooth direction D1). "Surface roughness" can be, for example, the arithmetic average roughness (Ra) or the maximum height (Ry) of the flexible external gear 3 in the circumferential direction, the ten-point average roughness (Rz), the average interval of concavities and convexities (Sm), the local peak The average interval (S) or the load length rate (tp) and so on.

In addition, in order for the lubricant Lb1 to easily permeate the gap X1 between the flexible external gear 3 and the outer ring 421, it is preferable that at least the first region R1 of the inner peripheral surface 301 of the flexible external gear 3 and the outer peripheral surface of the outer ring 421 424 is not oil-resistant.

(4.4) Surface state of external teeth

Next, the surface state of the external teeth 31 in this embodiment will be described with reference to FIGS. 7 , 8A, and 8B.

As described above, in the present embodiment, the rolling surface 300 (first rolling surface) which is not formed by shearing metal crystal grains (rolling process) is provided on the external teeth 31 . Therefore, as shown in FIG. 7 , the rolling surface 300 included in the external teeth 31 has a smooth surface state in which metal crystal grains are not sheared. Thereby, the friction between the external teeth 31 and the internal teeth 21 is reduced, the loss due to the friction between the external teeth 31 and the internal teeth 21 is reduced, and the power transmission efficiency of the harmonic gear device 1 is hardly lowered.

Especially in this embodiment, the rolling surface 300 is only provided on the outer teeth 31 among the outer teeth 31 and the inner teeth 21 . In short, the rolling surface 300 is at least provided on the outer teeth 31 , and the surface roughness is smaller than that of the inner teeth 21 . The rolling surface 300 is a surface formed by processing (rolling processing) without shearing the crystal grains of the metal, so for example, the internal surface formed by processing the crystal grains of the metal like cutting, grinding, or honing. Compared with the teeth 21, the surface roughness of the rolling surface 300 is of course smaller. Furthermore, by providing the rolling surface 300 having such a smooth surface state on the external teeth 31 pressed against the internal teeth 21 of the rigid internal gear 2 like a wedge, the friction between the external teeth 31 and the internal teeth 21 can be further reduced.

In addition, the rolling surface 300 is provided only on the external teeth 31 in the outer peripheral surface of (the body portion 321 of) the flexible external gear 3 . That is, the external teeth 31 are provided on the outer peripheral surface of the flexible external gear 3, and parts other than the external teeth 31 in the outer peripheral surface of the flexible external gear 3 are sheared by, for example, cutting, grinding or honing. Formed by grain processing. As a result, the rolling surface 300 of the external teeth 31 has a smaller surface roughness than a portion of the outer peripheral surface of the flexible external gear 3 other than the external teeth 31 . Thereby, only the required portion of the outer peripheral surface of the flexible external gear 3 can be rolled, which has the advantage of improving workability.

Here, the rolling surface 300 is provided at a position other than the tooth tops 313 and 213 of at least one of the external teeth 31 and the internal teeth 21 . That is to say, as shown in FIG. 7, the external tooth 31 has a dedendum 312, a dedendum 313, and a middle portion 314 in the tooth height direction, and the rolling surface 300 of the external tooth 31 is provided at a position other than the dedendum 313 (the dedendum 313). 312 and middle portion 314 etc.). In the present embodiment, the rolling surface 300 is only the dedendum 312 and the middle portion 314 in the tooth height direction on the surface of the external tooth 31, and the tooth top 313 is cut by cutting, grinding, or honing, for example. Formed by grain processing. Therefore, the surface roughness of the rolled surface 300 , that is, the surface of the dedendum 312 and the middle portion 314 in the tooth height direction is smaller than that of the tooth top 313 which is not the rolled surface 300 . Therefore, the rolling surface 300 (the surface of the dedendum 312 and the middle portion 314 in the tooth height direction) corresponds to the first region R1 in the inner peripheral surface 301 of the flexible external gear 3 , not the tooth top 313 of the rolling surface 300 The surface of is equivalent to the second region R2.

In this way, by providing the rolling surface 300 at a location other than the tooth tip 313 (the dedendum 312 , the middle portion 314 , etc.), the friction between the external teeth 31 and the internal teeth 21 can be easily reduced. In short, even in a state where the internal teeth 21 and the external teeth 31 are meshed, as shown in FIG. 7 , a gap G1 is ensured between the dedendum 313 of the external teeth 31 and the dedendum 212 of the internal teeth 21 . In addition, the external teeth 31 are in contact with the internal teeth 21 at parts other than the tooth tops 313 (the dedendum 312 and the middle part 314, etc.). tooth 21 friction.

In addition, in the present embodiment, the rolling surface 300 includes a flank trimming portion 310 (see FIG. 1B ) provided at at least one end in the flank direction D1. The “tooth profile modification” mentioned in the present disclosure refers to the profile modification in the tooth profile direction D1, and the profile profile modification portion 310 of the external tooth 31 is a part of the external tooth 31 where profile profile modification is performed. By flank modification, it is possible to give an intentional bulge to the regular flank shape of the gear, or to change the helix angle. Typical processing for tooth profile correction includes crown processing and relief processing (end undulation). The crowning is processing that rounds the center portion of the gear in the tooth direction D1 so that the center portion thereof is convex in the tooth direction D1. Ripping machining is a machining method in which both ends in the tooth radial direction D1 are moderately avoided. Conveying is processing that extends over substantially the entire length in the radial direction D1 such that the center portion is rounded, whereas relief processing is processing that avoids only both ends in the radial direction D1. Whether it is crowning or undercutting, by making the tooth thickness at both ends in the tooth line direction D1 smaller than that in the center, the tooth contact position with the mating gear can be brought closer to the center in the tooth line direction D1. Through such tooth shape modification, it is possible to suppress the "one-sided contact" in which the tooth contact is biased towards one end of the tooth direction D1 due to manufacturing errors or assembly errors of the gear, especially the end of the tooth direction D1 (tooth width end). ) The stress concentration at ) is alleviated, and the tooth contact is improved. The details of the flank trimming portion 310 will be described in the column of "(4.6) Flank trimming".

As shown in FIG. 8A in which a part of the dedendum 312 of the external tooth 31 (area Z1 in FIG. 7 ) is enlarged, in the external tooth 31, the dedendum 312 and the middle part 314 where the rolling surface 300 is provided mainly become A smooth surface state where the grains are not sheared. On the other hand, as shown in FIG. 8B , which is an enlarged part of the tooth tip 313 of the external tooth 31 (region Z2 in FIG. 7 ), at the tooth tip 313 where the rolling surface 300 is not provided, the crystal grains are mainly sheared. surface condition. As shown in FIGS. 8A and 8B , when the unit length W1 (0.25 mm as an example) of the tooth direction D1 and the unit length Y1 (1 μm as an example) in the direction of the longitudinal magnification are specified, the dedendum 312 (roll The surface roughness of the pressing surface 300) is smaller than the surface roughness of the crest 313.

Here, the surface roughness of the rolling surface 300 is preferably not less than 1/64 times and not more than 1/10 times the surface roughness of the crests 313 . The surface roughness of the rolling surface 300 is not limited to 1/64 or more of the surface roughness of the crest 313, for example, it may be 1/80 or more, 1/50 or 1/30 or 1/16. above and so on. Similarly, the surface roughness of the rolling surface 300 is not limited to 1/10 or less of the surface roughness of the crest 313, for example, it may be 1/2 or less, 1/5 or less, 1/12 or less, or 1/10 or less. 16 times or less, etc. In this way, the surface roughness of the rolling surface 300 (the dedendum 312 and the middle portion 314 ) is a value sufficiently smaller than the surface roughness of the tooth top 313 , so that the tooth root 312 and the middle portion 314 are easily reduced. 21 friction between. As an example, the surface roughness of the rolling surface 300 is preferably not less than Ra0.01 and not more than Ra0.2, and in this case, it is preferably not more than 1/10 of the surface roughness (Ra) of the crest 313 .

That is, on the surface of the external teeth 31 formed by performing processing such as cutting, grinding, or honing on the outer peripheral surface of the flexible external gear 3 to shear the crystal grains of the metal structure, scales are originally formed at the grain boundaries. The "burr" (convex part). On the other hand, in the rolling surface 300 formed by performing processing on the outer teeth 31 without shearing the crystal grains of the metal structure, such as rolling processing, such scaly "burrs" are not generated, and a smooth surface is realized. state.

In addition, the surface hardness of the middle portion 314 in the tooth height direction of the external teeth 31 is at least higher than that of the tooth tips 313 . Specifically, for example, only the middle portion 314 of the outer tooth 31 is locally heat-treated using a method such as laser hardening that enables local heat treatment, thereby locally increasing the surface hardness of the outer tooth 31 . As an example, the surface hardness of the tooth tips 313 of the external teeth 31 is HRC40, and the surface hardness of the middle part 314 is about HRC60.

If the harmonic gear unit 1 is used for a long period of time, for example, foreign matter such as metal powder or nitride may be generated due to chipping, abrasion, or the like due to contact between the internal teeth 21 and the external teeth 31 . In the present embodiment, the surface hardness of the external teeth 31 is locally increased, thereby making it less likely to damage the toughness and maintain the stability of the flexible external gear 3 compared to the case where the surface hardness of the entire flexible external gear 3 is increased. Deformation tolerance. On this basis, regarding the middle portion 314 in the tooth height direction, which can actually come into contact with the internal teeth 21, of the external teeth 31 of the flexible external gear 3, by increasing the surface hardness, it is possible to suppress the occurrence of damage due to contact with the internal teeth 21. Generation of foreign matter such as metal powder or nitride caused by chipping or wear of the external teeth 31.

(4.5) surface hardness

Next, the surface hardness of the internal teeth 21 and the external teeth 31 in this embodiment will be described.

As described above, in the present embodiment, the surface hardness of the internal teeth 21 is lower than that of the external teeth 31 . That is, the hardness of the surface of the external teeth 31 is higher (harder) than the hardness of the surface of the internal teeth 21 . The “hardness” mentioned in this disclosure refers to the degree of hardness of an object, and the hardness of a metal is represented by, for example, the size of a pit formed by pushing a steel ball with a certain pressure. Specifically, examples of the hardness of metal include Rockwell hardness (HRC), Brinell hardness (HB), Vickers hardness (HV), or Shore hardness (Hs). In the present embodiment, unless otherwise stated, the hardness is represented by Vickers hardness (HV). As a means for increasing the hardness (hardening) of a metal member, there are, for example, alloying or heat treatment.

In this embodiment, the surface of the external teeth 31 of the flexible external gear 3 is made of a material with high hardness and high toughness (toughness), and the internal teeth 21 of the rigid internal gear 2 are made of a material with a hardness lower than that of the external teeth 31 . In this embodiment, as an example, a material obtained by heat-treating (quenching and tempering) nickel-chromium-molybdenum steel specified as "SNCM439" by Japanese Industrial Standards (JIS: Japanese Industrial Standards) is used for the external teeth 31 . Spherical graphite cast iron specified as "FCD800-2" by Japanese Industrial Standards (JIS) is used for the internal teeth 21 .

Further, the surface hardness of the internal teeth 21 , which is relatively low in hardness compared with the external teeth 31 , is preferably HV350 or less. In this embodiment, as an example, the surface hardness of the internal teeth 21 is selected within the range of HV250 or more and less than HV350. The lower limit of the surface hardness of the internal teeth 21 is not limited to HV250, and may be, for example, HV150, HV160, HV170, HV180, HV190, HV200, HV210, HV220, HV230, or HV240. Likewise, the upper limit of the surface hardness of the internal teeth 21 is not limited to HV350, and may be, for example, HV360, HV370, HV380, HV390, HV400, HV410, HV420, HV430, HV440, or HV450.

In contrast, the surface hardness of the external teeth 31 , which is relatively harder than the internal teeth 21 , is preferably HV380 or higher. In this embodiment, as an example, the surface hardness of the external teeth 31 is selected within the range of not less than HV380 and not more than HV450. The lower limit of the surface hardness of the external teeth 31 is not limited to HV380, and may be, for example, HV280, HV290, HV300, HV310, HV320, HV330, HV340, HV350, HV360, or HV370. Likewise, the upper limit of the surface hardness of the internal teeth 21 is not limited to HV450, and may be, for example, HV460, HV470, HV480, HV490, HV500, HV510, HV520, HV530, HV540, or HV550.

In addition, in the present embodiment, the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is HV50 or more. That is, the surface hardness of the external teeth 31 is set to be HV50 or more higher than the surface hardness of the internal teeth 21 . In short, for example, if the surface hardness of the internal teeth 21 is HV350, the surface hardness of the external teeth 31 is HV400 or more. In addition, if the surface hardness of the external teeth 31 is HV380, the surface hardness of the internal teeth 21 is HV330 or less. The difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is not limited to HV50 or greater, and may be, for example, HV20 or greater, HV30 or greater, or HV40 or greater. Furthermore, the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is preferably greater, for example, more preferably HV60 or higher, HV70 or higher, HV80 or higher, HV90 or higher, or HV100 or higher. If the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is HV100 or more, when the surface hardness of the internal teeth 21 is HV350, the surface hardness of the external teeth 31 is HV450 or more.

As described above, in the present embodiment, the surface hardness of the internal teeth 21 is set to be lower than the surface hardness of the external teeth 31 . Therefore, when the internal teeth 21 contact the external teeth 31 during the operation of the harmonic gear device 1 , the internal teeth 21 having a relatively low surface hardness wear more aggressively than the external teeth 31 . When the two members (the inner teeth 21 and the outer teeth 31 ) having different surface hardnesses contact each other, the wear of the relatively soft inner teeth 21 advances, thereby suppressing the wear of the relatively hard outer teeth 31 . That is to say, in the initial stage of use of the harmonic gear unit 1, since the tooth surfaces of the internal teeth 21 are moderately worn, the real contact area between the internal teeth 21 and the external teeth 31 increases, and the surface pressure decreases, making it difficult to generate Wear of the external teeth 31 . In addition, when the surface hardness of the internal teeth 21 is HV350 or less as in the present embodiment, even if foreign matter is generated due to chipping or wear of the internal teeth 21 due to contact between the internal teeth 21 and the external teeth 31, the foreign matter is relatively small. Soft. In short, by making the foreign matter caused by abrasion that is likely to occur at the initial stage of use of the harmonic gear device 1 as a soft foreign matter that comes out of the relatively soft internal teeth 21, for example, even if the foreign matter enters the bearing 42, damage to the bearing can be suppressed. 42 damage. As a result, for example, the amount of generation of hard foreign matter that greatly damages the bearing 42 and the like are suppressed. In particular, when the difference between the surface hardness of the internal teeth 21 and the surface hardness of the external teeth 31 is a relatively large value such as HV50 or more, the above-mentioned effect is remarkable.

Furthermore, by using spherical graphite cast iron as the material of the internal teeth 21 , an effect of suppressing tooth surface ablation of the internal teeth 21 and the external teeth 31 can be expected at the time of initial wear of the internal teeth 21 . Thereby, a lubricating effect can be obtained at the meshing portion of the internal teeth 21 and the external teeth 31, and the power transmission efficiency in the wave gear device 1 can be improved.

The surface hardness of the internal teeth 21 and the external teeth 31 does not have to be specified by Vickers hardness (HV), and can also be specified by other hardness, such as Rockwell hardness (HRC), Brinell hardness (HB) or Shore hardness (Hs). The surface hardness of the internal teeth 21 and the external teeth 31 is specified.

Specifically, when the surface hardness is defined by the Rockwell hardness, the surface hardness of the internal teeth 21 is preferably HRC30 or less. As an example, the surface hardness of the internal teeth 21 is selected within the range of HRC20 to less than HRC30. The lower limit of the surface hardness of the internal teeth 21 is not limited to HRC20, and may be, for example, HRC10, HRC15, or HRC25. Likewise, the upper limit of the surface hardness of the internal teeth 21 is not limited to HRC30, and may be, for example, HRC35, HRC40, or HRC45.

In contrast, the surface hardness of the external teeth 31 is preferably HRC40 or higher. As an example, the surface hardness of the external teeth 31 is selected within the range of not less than HRC40 and not more than HRC60. The lower limit of the surface hardness of the external teeth 31 is not limited to HRC40, and may be, for example, HRC30, HRC35, or the like. Likewise, the upper limit of the surface hardness of the external teeth 31 is not limited to HRC60, and may be, for example, HRC50, HRC55, HRC65, HRC70, or HRC75.

In addition, due to fretting wear between the flexible external gear 3 and the wave generator 4 (the outer ring 421 of the bearing 42 ), foreign matter generated due to chipping, abrasion, etc. is relatively hard. That is, the foreign matter generated by the contact between the flexible external gear 3 with a relatively high surface hardness and the outer ring 421 of the bearing 42 is harder than the soft foreign matter coming out of the internal teeth 21 as described above. When the hard foreign matter from the flexible external gear 3 or the outer ring 421 enters the bearing 42, the indentation caused by the biting of the foreign matter into the outer ring 421 or the inner ring 422 and the rolling element 423 is the origin, and the outer ring 421, the inner ring 422, and the surface of any one of the rolling elements 423 may be damaged. Such damage (exfoliation of the surface origin type) leads to deterioration of the quality, characteristics, etc. of the harmonic gear device 1 , and consequently leads to a decrease in the reliability of the harmonic gear device 1 .

However, as described above, in the harmonic gear device 1 of the present embodiment, by providing the first region R1 with a small surface roughness on the back side of the external teeth 31 in the inner peripheral surface 301 of the flexible external gear 3, Accordingly, sufficient lubricant Lb1 is maintained at the contact portion between the flexible external gear 3 and the wave generator 4 . Therefore, the surface of the contact portion of the flexible external gear 3 with the bearing 42 (the outer ring 421 ) is covered with the lubricant Lb1, and the occurrence of fretting wear can be suppressed. Or the generation of foreign objects of sound quality coming out of the outer ring 421 . As a result, for example, it becomes difficult to cause damage caused by entry of relatively hard foreign matter into the bearing 42, and it is difficult to cause a decrease in reliability especially during long-term use. Therefore, the transmission efficiency of the harmonic gear device 1 is further improved. , extended life and improved performance.

(4.6) Tooth trimming

Next, tooth profile dressing of the internal teeth 21 and the external teeth 31 in this embodiment will be described.

As a premise, as shown in FIG. 1B , the internal teeth 21 have a dedendum 212 and a dedendum 213 . The internal teeth 21 are provided on the inner peripheral surface of the rigid internal gear 2, so the dedendum 212 of the internal teeth 21 corresponds to the inner peripheral surface of the rigid internal gear 2, and the addendum 213 faces inward from the inner peripheral surface of the rigid internal gear 2 (the rigid internal gear 2 center of gear 2) protrudes.

On the other hand, the external teeth 31 have a dedendum 312 and a dedendum 313 as shown in FIG. 1B . The external teeth 31 are arranged on the outer peripheral surface of the flexible external gear 3 (the body part 321), so the dedendum 312 of the external teeth 31 is equivalent to the outer peripheral surface of the flexible external gear 3 (the body part 321), and the addendum 313 is from the flexible external gear 3 (the body part 321). The outer peripheral surface of (the body part 321 of) the external gear 3 protrudes outward.

At the meshing position of the internal teeth 21 and the external teeth 31 , the crests 313 of the external teeth 31 are inserted between adjacent pairs of crests 213 of the internal teeth 21 , so that the internal teeth 21 and the external teeth 31 are meshed. At this time, the dedendum 313 of the external tooth 31 is opposed to the dedendum 212 of the internal tooth 21 , and the dedendum 213 of the internal tooth 21 is opposed to the dedendum 312 of the external tooth 31 . In addition, ideally, a slight clearance is ensured between the dedendum 212 of the internal tooth 21 and the dedendum 313 of the external tooth 31 , and between the dedendum 312 of the external tooth 31 and the dedendum 213 of the internal tooth 21 . In this state, the opposing tooth surfaces of the internal teeth 21 and the external teeth 31 in the tooth thickness direction contact each other, and power transmission between the rigid internal gear 2 and the flexible external gear 3 is performed.

Furthermore, the internal teeth 21 have chamfered portions 211 at both end portions in the tooth direction D1. The chamfered portion 211 is a C surface that reduces the amount of protrusion of the internal teeth 21 toward both sides in the tooth direction D1 , and is basically a portion that does not contribute to the meshing of the internal teeth 21 and the external teeth 31 . That is to say, the chamfered portion 211 of the internal tooth 21 does not contact the external tooth 31 at the meshing position of the internal tooth 21 and the external tooth 31 . Likewise, the external teeth 31 have chamfered portions 311 at both end portions in the tooth direction D1. The chamfered portion 311 is a C surface that reduces the amount of protrusion of the internal teeth 21 toward both sides in the tooth direction D1 , and is basically a portion that does not contribute to the meshing of the internal teeth 21 and the external teeth 31 . That is to say, the chamfered portion 311 of the external tooth 31 is not in contact with the internal tooth 21 at the meshing position of the internal tooth 21 and the external tooth 31 .

Here, in the present embodiment, the internal teeth 21 of the rigid internal gear 2 have tooth-shaft trimming portions 210 . That is, in the wave gear device 1 , at least the internal teeth 21 are shaped. The tooth profile trimming portion 210 of the inner tooth 21 is disposed at least one end portion in the tooth profile direction D1. In other words, the internal tooth 21 has the tooth profile modification portion 210 at least one end portion of the internal tooth 21 in the tooth profile direction D1. In this embodiment, the flank trimming portions 210 are provided at both ends of the internal teeth 21 in the flank direction D1.

In addition, in the present embodiment, the external teeth 31 of the flexible external gear 3 also have tooth-shape correcting portions 310 . That is to say, the harmonic gear unit 1 implements profile correction not only on the internal teeth 21 but also on the external teeth 31 . The flank trimming portion 210 of the external teeth is disposed at least one end portion in the flank direction D1. In other words, the external teeth 31 have tooth profile trimming portions 310 at least one end portion of the external teeth 31 in the tooth profile direction D1. In this embodiment, the flank trimming portions 310 are provided at both ends of the external teeth 31 in the flank direction D1.

In this way, in the wave gear device 1 of the present embodiment, at least one of the inner teeth 21 and the outer teeth 31 has the tooth

shape modification portions

210 , 310 . The tooth

shape trimming portions

210 and 310 make it difficult to generate stress concentration due to excessive tooth contact between the internal teeth 21 and the external teeth 31 , and as a result, the tooth contact between the internal teeth 21 and the external teeth 31 can be improved. Thereby, foreign matter caused by chipping or abrasion due to contact between the internal teeth 21 and the external teeth 31 is less likely to occur, and it is possible to realize the wave gear device 1 in which reliability is less likely to be lowered.

(5) Function

Next, the action of the wave gear device 1 of this embodiment will be described in more detail.

As described above, in the wave gear device 1, especially if it is used for a long time, along with the rotation of the wave generator 4 embedded inside the flexible external gear 3, the contact portion between the flexible external gear 3 and the wave generator 4 will be damaged. Fretting wear may occur. In addition, if fretting wear occurs, roughness of the surface, rust caused by abrasive powder, and damage to the wave generator 4 (the bearing 42) caused by the ingress of abrasive powder into the wave generator 4, etc. may be caused. The reliability of the harmonic gear unit 1 is affected.

The cause of such fretting wear is considered to be "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the flexible external gear 3 and the wave generator 4 . That is, it is presumed that the contact portion between the flexible external gear 3 and the wave generator 4 is originally in an environment where fretting wear is likely to occur due to microvibration between the contact surfaces in a state where the lubricant Lb1 is insufficient. The following two reasons are specifically considered as reasons why such fretting wear is likely to occur in an environment.

The first reason is that the elastic deformation of the flexible external gear 3 is repeated frequently. That is, during one revolution of the cam 41 of the wave generator 4, the flexible external gear 3 repeats elastic deformation twice in one direction (for example, the up-down direction in FIG. 2A ) to have an elliptical major axis. Therefore, when the cam 41 rotates at a high speed, the flexible external gear 3 is elastically deformed repeatedly at high speed, and vibrations are likely to be generated at the contact portion between the flexible external gear 3 and the wave generator 4 as the elastic deformation is repeated. As a result, microvibration occurs in a state where the lubricant Lb1 is insufficient at the contact portion between the flexible external gear 3 and the wave generator 4 .

More specifically, in a state where the flexible external gear 3 is elastically deformed, the end of the flexible external gear 3 on the opening surface 35 side in the direction of the rotation axis Ax1 is deformed more than the end on the bottom 322 side, Becomes a shape closer to an elliptical shape. Therefore, in the state where the flexible external gear 3 is elastically deformed, as shown in FIG. 302. Also, the inclination angle θ1 of the tapered surface 302 changes with elastic deformation of the flexible external gear 3 . That is, when the flexible external gear 3 is viewed from the side of the opening surface 35, the inclination angle θ1 of the tapered surface 302 becomes the largest at both ends in the major axis direction of the ellipse ("major axis side" in FIG. 9 ). , the inclination angle θ1 of the tapered surface 302 is the smallest at both ends in the minor axis direction of the ellipse ("minor axis side" in FIG. 9). Therefore, the inclination angle θ1 of the tapered surface 302 also changes at a high speed due to the frequent and repeated elastic deformation of the flexible external gear 3, whereby the inner peripheral surface 301 (tapered surface 302) of the flexible external gear 3 repeatedly impacts the outer surface. The outer peripheral surface 424 of the ring 421 vibrates in a manner. As described above, microvibrations accompanying impacts are generated, and as a result, fretting wear is likely to occur at the contact portion between the flexible external gear 3 and the wave generator 4 .

The second reason is that the relative rotation between the outer ring 421 and the flexible external gear 3 is at a low speed. That is, due to the influence of the gap X1 between the outer ring 421 and the flexible external gear 3, the outer ring 421 and the flexible external gear 3 are elastically deformed as the cam 41 of the wave generator 4 rotates. There may be relative rotation with the flexible external gear 3 . However, this relative rotation is, for example, a low-speed rotation of about a few thousandths or a few hundredths of the rotation speed of the cam 41 . Therefore, in the gap X1 between the outer ring 421 and the flexible external gear 3, the lubricant Lb1 cannot be expected to flow due to the relative rotation, and it is disadvantageous to form a film (oil film) of the lubricant Lb1 at the contact portion. environment of. Nevertheless, since the outer ring 421 and the flexible external gear 3 may be relatively rotated, the outer ring 421 and the flexible external gear 3 rub against each other, creating an environment where fretting wear is likely to occur.

In the harmonic gear device 1 of the present embodiment, for the reasons described above, the lubricant Lb1 can be forcibly supplied to the contact portion between the outer ring 421 and the flexible external gear 3 in an environment where fretting wear is likely to occur. . That is, the harmonic gear device 1 can supply the lubricant Lb1 to the contact portion of the flexible external gear 3 and the wave generator 4 through the through hole H1 , thereby maintaining sufficient lubricant Lb1 at the contact portion. In this way, occurrence of fretting wear is suppressed by preventing "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3 .

In addition, in the harmonic gear device 1 of the present embodiment, the first region R1 located on the inner peripheral surface 301 of the flexible external gear 3 on the back side of the external teeth 31 is formed to have a surface roughness higher than that of the first region R1. The second region R2 is small. Therefore, by making the inner peripheral surface 301 of the flexible external gear 3 a partially smooth surface like the first region R1, the lubricant Lb1 is likely to stay at the contact portion of the flexible external gear 3 with the wave generator 4. , sufficient lubricant Lb1 can be maintained at the contact site. Accordingly, it is possible to further prevent "lubricant depletion" in which the lubricant Lb1 is insufficient or exhausted at the contact portion between the outer ring 421 and the flexible external gear 3, and suppress the occurrence of fretting wear.

As a result, the surface of the contact portion between the outer ring 421 and the flexible external gear 3 is covered with the lubricant Lb1, and the occurrence of fretting wear is suppressed. As a result, in the harmonic gear device 1 of the present embodiment, it is possible to provide a device in which troubles due to fretting wear between the outer ring 421 and the flexible external gear 3 are less likely to occur, and a decrease in reliability is less likely to occur. Harmonic gear unit 1. Furthermore, since the harmonic gear device 1 of the present embodiment is less prone to reliability degradation even when it is used for a long period of time, the transmission efficiency of the harmonic gear device 1 is improved, its life is extended, and its performance is improved.

That is, since the harmonic gear unit 1 supplies the lubricant Lb1 to the contact portion between the outer ring 421 and the flexible external gear 3, it is difficult to hinder the deformation followability of the flexible external gear 3, and it brings about improvement of power transmission efficiency and the improvement of power transmission efficiency based on application. Life extension due to reduction of load on the bearing 42 and the like. Furthermore, since the wear powder generated by fretting wear is also prevented from entering the bearing 42, etc., it is also possible to reduce the occurrence of damage originating from indentation (surface-originated spalling) due to the bite of wear powder. Therefore, life extension and performance improvement can be expected as the harmonic gear device 1 .

In particular, when focusing on a part of the circumference of the outer ring 421, in the structure in which the lubricant reservoir exists only in the lower part of the outer contour of the actuator 100 (see FIG. 4), if there is no through hole H1, then The lubricant Lb1 can penetrate into the gap X1 only when the eye point passes the lubricant reservoir. Also, since the rotation speed of the outer ring 421 is lower than that of the inner ring 422 , the frequency with which the lubricant Lb1 can infiltrate into the gap X1 is low. On the other hand, in the wave gear device 1 of the present embodiment, since the through hole H1 is provided, when the visible portion of the outer ring 421 passes through the lubricant reservoir, only the lubricant Lb1 is supplied between the outer ring 421 and the inner ring 422 , the lubricant Lb1 can also be supplied to the gap X1. That is, since the lubricant Lb1 supplemented between the outer ring 421 and the inner ring 422 is supplied to the gap X1 through the through hole H1, it is difficult to generate a “slip” at the contact portion with the flexible external gear 3 on the entire circumference of the outer ring 421. Lubricant exhausted".

In addition, in the present embodiment, when the bearing 42 operates to rotate the plurality of rolling elements 423 , the rolling elements 423 function as a pump, whereby the lubricant Lb1 can be forcibly sent into the gap X1 through the through hole H1 . Further, the surface roughness of the first region R1 located on the back side of the external teeth 31 in the inner peripheral surface 301 of the flexible external gear 3 is formed small. According to these configurations, the lubricant Lb1 supplied to the gap X1 through the through hole H1 easily stays on the inner peripheral surface 301 of the flexible external gear 3 , and depletion of the lubricant in the gap X1 can be efficiently eliminated. Furthermore, the elastic deformation of the flexible external gear 3 is repeated, and the rapid change of the inclination angle θ1 of the tapered surface 302 also contributes to the diffusion of the lubricant Lb1 in the gap X1. Furthermore, not only suppression of lubricant depletion but also improvement of startability of the harmonic gear device 1 in a low-temperature environment where the lubricant Lb1 is likely to solidify can be achieved, for example.

(6) Application example

Next, an application example of the harmonic gear device 1 , the actuator 100 , and the robot joint device 130 of the present embodiment will be described with reference to FIG. 10 .

Fig. 10 is a cross-sectional view showing an example of a robot 9 employing the harmonic gear device 1 according to the present embodiment. The robot 9 is a horizontal multi-joint robot, that is, a so-called SCARA (Selective Compliance Assembly Robot Arm) type robot.

As shown in FIG. 10 , the robot 9 includes two robot joint devices 130 (including the harmonic gear unit 1 ) and a link 91 . The two robot joint devices 130 are respectively provided at two joints of the robot 9 . The link 91 connects the two robot joint devices 130 . In the example of FIG. 10 , the harmonic gear unit 1 is not a cup type, but a top hat type wave speed reduction device. That is, in the harmonic gear device 1 illustrated in FIG. 10 , the flexible external gear 3 formed in the shape of a hat is used.

(7) Manufacturing method

Next, a method of manufacturing the harmonic gear device 1 of the present embodiment will be described with reference to FIGS. 11 to 16B .

FIG. 11 is a schematic explanatory view showing the process of machining the inner peripheral surface 301 of the flexible external gear 3 . FIG. 12A is a schematic sectional view showing a rolling roll T1 and a chuck member T2 used for processing the inner peripheral surface 301 of the flexible external gear 3 , and FIG. 12B is a schematic side view thereof. FIG. 13A is a schematic sectional view showing a chuck member T2 of a modified example, and FIG. 13B is a schematic enlarged view of a region Z1 in FIG. 13A . FIG. 14 is a schematic explanatory view showing the process of machining the external teeth 31 of the flexible external gear 3 . FIG. 15A is a schematic front view of a hob T3 used for machining the external teeth 31 , and FIG. 15B is a schematic side view thereof. FIG. 16A is a schematic front view showing a tool T4 used for processing the rolling surface 300 of the external tooth 31, and FIG. 16B is a schematic side view thereof.

(7.1) Processing of the inner peripheral surface of the flexible external gear

First, a method of processing the inner peripheral surface 301 of the flexible external gear 3 in the method of manufacturing the harmonic gear device 1 according to the present embodiment will be described.

As shown in FIG. 11 , the manufacturing method of the harmonic gear device 1 according to this embodiment includes a preparation step (step P11 ) and a plastic working step (step P13 ). The preparation step is a step of preparing the base material 3A to be the base of the flexible external gear 3 . The plastic working step is a step of forming the first region R1 on the inner peripheral surface 301 of the base material 3A by plastic working. That is, in this manufacturing method, an operator first prepares a cylindrical base material 3A having an inner peripheral surface 301 in a preparation step. The inner peripheral surface 301 of the base material 3A is formed, for example, by cutting, grinding, or honing of a metal member. That is, the inner peripheral surface 301 of the base material 3A prepared in the preparation step is in a surface state in which metal crystal grains are sheared throughout the inner peripheral surface 301 like the second region R2 .

Then, in the plastic working step, the operator performs plastic working on a part of the inner peripheral surface 301 of the base material 3A, so that the inner peripheral surface 301 includes the first region R1 (rolled surface) and the second region R2 (cutting surface). Surface) flexible external gear 3. In this embodiment, as an example, the plastic working performed in the plastic working step is tumble processing using the rolling roll T1. Rolling processing is a type of rolling processing in which a metal surface is flattened by a roll T12 (see FIG. 12A ) of the rolling roll T1 to form a smooth surface state. That is, in the plastic working step, in the state where the roller T12 made of a high-hardness metal is pressed against the inner peripheral surface 301 of the base material 3A, the roller T12 is rolled along the inner peripheral surface 301 along the inner surface. The circumferential movement of the peripheral surface 301 plastically deforms the inner peripheral surface 301 to form the first region R1.

More specifically, a rolling roll T1 as shown in FIGS. 12A and 12B is used in the plastic working step. FIG. 12A corresponds to the cross section along line A1-A1 of FIG. 12B. The rolling roll T1 has a main shaft portion T11 configured to be rotatable (rotatable) around a central axis Ax3, and a plurality of rolls T12 held on the outer peripheral portion of the main shaft portion T11. A plurality of (here, eight as an example) rollers T12 are arranged at equal intervals in the circumferential direction of the main shaft portion T11. Each roller T12 is formed in a cylindrical shape, and is held by the main shaft portion T11 in a rotatable (rotatable) state about a central axis Ax4 parallel to the central axis Ax3. In the state where such rolling roller T1 is inserted into the base material 3A, by rotating and driving the main shaft portion T11 around the central axis Ax3 (counterclockwise in the example of FIG. The central axis Ax4 rotates around the center (clockwise in the example of FIG. 12B ). At this time, the plurality of rolls T12 in contact with the inner peripheral surface 301 of the base material 3A perform rolling while moving so as to roll on the inner peripheral surface 301 (step P13 of FIG. 11 ). According to such a plastic working step, not only the first region R1 with a smooth surface state can be formed, but also surface modification such as improvement in wear resistance and improvement in fatigue strength can be expected.

In addition, in this embodiment, there is also a chucking step (step P12 ) of chucking the base material 3A from the outer peripheral surface side with the chuck member T2 at least in the plastic working step. Accordingly, in a state where the roller T12 is pressed against the inner peripheral surface 301 of the base material 3A, the deformation of the base material 3A itself extending to the outer peripheral side can be suppressed, and the inner peripheral surface 301 can be rolled efficiently.

As shown in FIGS. 12A and 12B , the chuck member T2 is formed in a cylindrical shape that is opened on both sides in a direction parallel to the central axis Ax3 as a whole. The chuck member T2 has a body portion T21 integrally formed continuously in the circumferential direction and a plurality of individual pieces T22 divided into a plurality in the circumferential direction. The plurality of individual pieces T22 are connected to one end edge (the right end edge in FIG. 12A ) of the main body portion T21 in the axial direction. The inner diameter of the portion surrounded by the plurality of individual pieces T22 is reduced by bending the plurality of individual pieces T22 toward the central axis Ax3 with the connecting portion with the main body T21 as a fulcrum. Therefore, as shown in FIG. 11 , the base material 3A is inserted from the side of the plurality of individual pieces T22 in the chuck member T2 (process P11), and thereafter, by fastening the plurality of individual pieces T22 from the outside, the chuck member T2 is removed from the outer peripheral side. Clip substrate 3A.

Then, in a state where the cylindrical base material 3A is clamped (held) by the chuck member T2 from the outer peripheral surface side, the rolling roll T1 is inserted into the base material 3A, and the rolling roll T1 is rotated about the axis Ax3. (Process P13). After the first region R1 is formed by plastic working (rolling), the rolling roller T1 is pulled out from the base material 3A, and the fastening of the plurality of individual pieces T22 is released, thereby releasing the chuck member T2 from the base material 3A. clamping (process P14). In this state, the base material 3A can be taken out from the chuck member T2.

In addition, in this embodiment, the external teeth 31 on the outer peripheral surface of the flexible external gear 3 are not formed in the plastic working step. That is, the base material 3A shown in FIG. 11 is in a state where the external teeth 31 are not formed. The details of the process for forming the external teeth 31 will be described in the column of "(7.2) Processing of external teeth". That is, the method of manufacturing the harmonic gear device 1 of the present embodiment further includes a step of forming the external teeth 31 on the outer peripheral surface of the base material 3A after the plastic working step. Accordingly, in the plastic working step of forming the first region R1 at the position on the back side of the external teeth 31 , troubles such as deformation of the external teeth 31 can be avoided.

After the external teeth 31 are formed, the base material 3A may be subjected to surface treatment such as shot peening or chemical conversion film formation, for example. In the shot peening process, the fatigue strength of the flexible external gear 3 can be improved by projecting small spherical shot material to modify and harden the surface. It is preferable to perform curing (masking) on the inner peripheral surface (particularly, the first region R1 ) of the rolled base material 3A when performing these shot peening processes, surface treatments, and the like. Thereby, the inner peripheral surface of the base material 3A after rolling is less likely to be affected by shot peening, surface treatment, or the like.

In addition, in the present embodiment, the plastic working is performed by rotationally driving (the main shaft portion T11 of) the rolling roll T1, but it is not limited thereto, as long as there is a relative friction between the main shaft portion T11 of the rolling roll T1 and the base material 3A. Just rotate it. For example, plastic working may be performed by rotating the chuck member T2 while the main shaft portion T11 of the rolling roll T1 is fixed to rotate the substrate 3A relative to the main shaft portion T11 of the rolling roll T1 .

In addition, as shown in FIGS. 13A and 13B , the chuck member T2 may have an inner peripheral surface T221 having a shape corresponding to the outer peripheral surface of the base material 3A. The inner peripheral surfaces T221 of the plurality of individual pieces T22 of the chuck member T2 shown in FIGS. 13A and 13B are formed in a shape following the shape of the outer peripheral surface of the base material 3A before incising, that is, before the outer teeth 31 are formed. Specifically, as shown in FIG. 13B , an expansion portion 31A is provided on the outer peripheral surface of the base material 3A before tooth cutting and on the side of the opening surface 35 . The swollen portion 31A is provided over the entire circumferential direction of the base material 3A, and is formed thicker than other portions. In addition, the inner peripheral surface T221 of the plurality of individual pieces T22 has a recess having a shape corresponding to the swollen portion 31A, and the swelled portion 31A is fitted into the sag when the base material 3A is clamped by the chuck member T2.

That is, in the example of FIGS. 13A and 13B , the chuck member T2 has an inner peripheral surface T221 having a shape corresponding to the outer peripheral surface of the base material 3A, and is configured to be divisible into a plurality of individual pieces T22 in the circumferential direction. According to this configuration, in the plastic working step, the chuck member T2 can receive the rolling force from the rolling roll T1 over the entire area of the outer peripheral surface of the base material 3A. Therefore, for example, compressive residual stress due to rolling is also applied to the boundary portion between the body portion 321 of the flexible external gear 3 and the external teeth 31 . That is to say, in addition to the outer tooth 31 part of the flexible external gear 3, the inner peripheral surface 301 is also formed of a rolling surface for the body part 321, so that at least the boundary part between the outer tooth 31 and the body part 321 can also be applied. Structure of compressive residual stress generated by rolling process. This makes the flexible external gear 3 thinner and improves the toughness (increases the allowable stress) under the action of compressive residual stress, so that the resistance to deformation of the flexible external gear 3 can be maintained.

(7.2) Processing of external gears

Next, a method of processing the external teeth 31 of the flexible external gear 3 in the method of manufacturing the harmonic gear device 1 according to the present embodiment will be described.

As shown in FIG. 14 , the manufacturing method of the harmonic gear device 1 according to the present embodiment includes a step P21 , a step P22 , and a step P23 . Step P21 is a step of preparing the (second) base material 3A to be the base of the flexible external gear 3 . Step P22 is a step of forming the external teeth 31 on the (second) base material 3A. Step P23 is a step of forming the rolling surface 300 on the external teeth 31 by plastic working. That is, in this manufacturing method, an operator first prepares the base material 3A having the swollen portion 31A in step P21. In the present embodiment, the (second) base material 3A prepared in the step P21 is in a state in which the inner peripheral surface 301 is plastically worked (rolled) in the above-mentioned plastic working step to form the first region R1 . Then, in step P22, the external teeth 31 are formed on the swollen portion 31A by, for example, cutting, grinding, or honing. That is, before the rolling surface 300 is formed in the step P23, the outer teeth 31 of the base material 3A are in a surface state in which metal crystal grains are sheared in the entire area of the outer teeth 31, similarly to the second region R2.

In addition, in the embodiment, since the (first) rolling surface 300 is formed on the outer teeth 31, the manufacturing method includes the above-mentioned steps P21 to P22 (see FIG. 14 ). However, as in other embodiments, the inner teeth 21 are formed (first) 2) In the case of the rolling surface 200, the steps P21 to P23 are replaced as follows. That is, step P21 is a step of preparing the first base material to be the base of the rigid internal gear 2 . Step P22 is a step of forming the internal teeth 21 on the first base material. Step P23 is a step of forming the rolling surface 200 by plastic working the internal teeth.

Here, at least one of the step of forming the internal teeth 21 on the first base material and the step P22 of forming the external teeth 31 on the (second) base material 3A includes cutting. Specifically, the internal teeth 21 and the external teeth 31 are formed by gear cutting (hob processing) using a hob that rotationally drives the hob T3. That is, in the step P22 of forming the external teeth 31 on the base material 3A, as shown in FIG. The hob T3 cuts the expanded portion 31A to form the external teeth 31 . At this time, as the hob T3 rotates, the base material 3A also rotates around the rotation axis Ax1 , whereby the external teeth 31 are formed over the entire circumference of the outer peripheral surface of the base material 3A.

More specifically, in step P22, hob T3 is used as shown in FIGS. 15A and 15B . The hob T3 has a cylindrical portion T31 configured to be rotatable (rotatable) around the central axis Ax5, and a plurality of blades T32 protruding from the outer peripheral surface of the cylindrical portion T31. The plurality of cutting edges T32 are arranged in a row so as to form a helical shape centering on the central axis Ax5. In FIGS. 14 , 15A and 15B , the outline of a row (blade row) composed of a plurality of blades T32 is shown by a phantom line (two-dot chain line), and illustration of a part of the blades T32 is omitted. In the state where the plurality of blades T32 of the hob T3 are pressed against the swollen portion 31A of the base material 3A, while the base material 3A is rotated around the rotation axis Ax1, the center axis Ax5 is used as the center axis Ax5 by the hob head. The center (clockwise in the example of FIG. 15B ) rotationally drives the cylindrical portion T31. At this time, the expansion portion 31A of the substrate 3A is cut by the cutting edge T32 of the hob T3, and the external teeth 31 are formed at the same pitch as the plurality of cutting edges T32 in the direction parallel to the central axis Ax5 (step P22 in FIG. 14 ). .

In addition, according to the tooth cutting by such cutting (hob machining), the external teeth 31 are formed, but the surface of the external teeth 31 is the same as the second region R2, and the entire region has a surface state in which metal crystal grains are sheared. . That is, scale-shaped tool marks are generated on the surface of the external teeth 31 in accordance with the feeding amount of the hob T3 and the like. In the present embodiment, in the step P23 after the step P22, the rolling surface 300 is formed on the external teeth 31 by plastic working, thereby flattening the surface of the external teeth 31 with such irregularities as tool marks, thereby achieving smoothness. surface state.

Specifically, in the step P23, the plastic working uses a tool T4 having ribs T42 having the same pitch as the hob T3 used for cutting, as shown in FIGS. 16A and 16B . The tool T4 has a cylindrical portion T41 configured to be rotatable (rotatable) around the central axis Ax5, and a rib T42 protruding from the outer peripheral surface of the cylindrical portion T41. The rib T42 is formed in a spiral shape centered on the central axis Ax5. Here, the cylindrical portion T41 has the same shape as the cylindrical portion T31 of the hob T3, and the rib T42 has the same shape as the outer shape of the row (blade row) constituted by the plurality of blades T32 of the hob T3. That is, the tool T4 corresponds to a shape in which the blade portion T32 of the hob T3 is removed, and can be attached to the hob head instead of the hob T3.

In the state where the ribs T42 of the tool T4 are pressed against the external teeth 31 of the base material 3A, the base material 3A is rotated around the rotation axis Ax1, and the center axis Ax5 is used as the center by the hob (in FIG. 16B, clockwise) to rotate and drive the cylindrical portion T41. At this time, the surface of the external tooth 31 is plastically deformed in a state where the rib T42 of the tool T4 is in pressure contact with the external tooth 31 to form the rolling surface 300 (step P23 of FIG. 14 ). As a result, the grain boundaries generated by the shearing of crystal grains are flattened together with the tool marks generated during tooth cutting, and the rolling surface 300 with a smooth surface state is realized. As a result, the operator can easily form the rolling surface 300 on the outer teeth 31 by using the tool T4 instead of the hob T3 and only performing the same hob operation as in the hob machining.

In addition, since the tool T4 forms the rolling surface 300 on the external tooth 31 by performing the same operation as the hob T3, machining such as crowning or tooth relief (end undulation) can be performed by rolling. Thereby, the rolling surface 300 including the flank trimming portion 310 can be easily realized.

(7.3) Others

When manufacturing the harmonic gear device 1 according to the present embodiment, especially when manufacturing the outer ring 421 , it is preferable to take measures to avoid a decrease in strength due to the provision of the through-hole H1 .

As an example, after the drilling step of forming the through-hole H1, a surface processing step of surface processing the outer ring 421 (in particular, the inner peripheral surface 425 serving as the rolling surface) is performed. That is, in order to prevent the through-hole H1 from becoming the origin of cracks in the outer ring 421 , it is preferable to leave a compressive residual stress around the through-hole H1 in the outer ring 421 . Therefore, it is preferable to form the through-hole H1 and leave the compressive residual stress generated by the heat treatment before the outer ring 421 is subjected to a surface processing step such as quenching. Alternatively, the fatigue strength of the outer ring 421 may be improved by performing shot peening in which a small spherical shot material is shot around the through hole H1 of the outer ring 421 to modify and harden the surface after the heat treatment.

(8) Variations

The above-described embodiment is only one of various embodiments of the present disclosure. Embodiments can be changed in various ways depending on the design and the like as long as the object of the present disclosure can be achieved. In addition, the drawings referred to in the present disclosure are all schematic diagrams, and the respective ratios of sizes and thicknesses of components in the drawings do not necessarily reflect actual dimensional ratios. Hereinafter, modification examples of the embodiment will be listed. Modifications described below can be applied in combination as appropriate.

The through hole H1 may be located at a position deviated from the center of the plurality of rolling elements 423 in a direction (tooth direction D1 ) parallel to the rotation axis Ax1 . As an example, the through hole H1 is disposed at a position deviated from the center of the rolling element 423 toward the opening surface 35 , that is, at a position between the center of the rolling element 423 and the opening surface 35 in the tooth direction D1 . According to this configuration, even if a large load is applied in the radial direction from the rolling elements 423 to the member (here, the outer ring 421 ) formed with the through-hole H1 , the load hardly acts on the periphery of the through-hole H1 . Cracks or the like originating from the through-hole H1 are less likely to occur.

In addition, the through-hole H1 may be provided in a plurality of places in a direction (tooth direction D1) parallel to the rotation axis Ax1. In addition, in the radial direction, the opening area of the through hole H1 on the side of the gap X1 may be smaller than the opening area on the side opposite to the gap X1. That is, in the (first) through hole H1 provided in the outer ring 421 , the opening area of the through hole H1 on the outer peripheral surface 424 side on the side of the gap X1 is larger than the opening area of the through hole H1 on the inner peripheral surface 425 side on the opposite side to the gap X1 . The hole H1 has a small opening area. Thereby, the pressure of the lubricant Lb1 supplied to the gap X1 through the through-hole H1 can be increased.

17A and 17B show modified examples of the embodiment, and are cross-sectional views corresponding to FIGS. 1A and 1B . In the harmonic gear device 1A shown in FIGS. 17A and 17B , (second) through holes H2 are provided in the external teeth 31 of the flexible external gear 3 . In other words, in this modified example, the through-holes H2 include “second through-holes” provided in the external teeth 31 of the flexible external gear 3 . The through hole H2 provided in the portion of the external teeth 31 of the flexible external gear 3 , that is, the through hole H2 provided in a portion corresponding to the bearing 42 in the direction of the rotation axis Ax1 penetrates the flexible external gear 3 in the radial direction. Thus, the opening surface on one side of the through hole H2 faces the gap X1 between the outer ring 421 and the flexible external gear 3 , and the opening surface on the other side of the through hole H2 faces the gap X1 between the external teeth 31 of the flexible external gear 3 . The outer peripheral surface serving as the meshing surface with the internal teeth 21 is open. Therefore, one end of the through hole H2 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 , and the other end is connected to the space between the outer teeth 31 and the inner teeth 21 . Therefore, the space between the external teeth 31 and the internal teeth 21 communicates with the gap X1 between the outer ring 421 and the flexible external gear 3 via the through hole H2. Thereby, the lubricant Lb1 in the space between the external teeth 31 and the internal teeth 21 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through-hole H2.

When the flexible external gear 3 rotates relative to the rigid internal gear 2 , a part of the external teeth 31 meshes with the internal teeth 21 , so the external teeth 31 and the internal teeth 21 function as a pump. That is, the outer teeth 31 and the inner teeth 21 constitute a pump. In this modified example, since the external teeth 31 mesh with the internal teeth 21, the pressure in the space between the external teeth 31 and the internal teeth 21 is increased, so that the lubricant Lb1 between the external teeth 31 and the internal teeth 21 passes through the through holes. H2 is extruded to the side of the gap X1. In this way, the external teeth 31 and the internal teeth 21 constitute a positive displacement pump such as a vane pump, and squeeze out the lubricant Lb1 to the gap X1 side with sufficient pressure, so that sufficient lubricant Lb1 can be easily supplied into the gap X1.

Here, as shown in FIG. 17B , the (second) through hole H2 is located between the center and the end on the opening surface 35 side in the external teeth 31 in a direction parallel to the rotation axis Ax1 (tooth direction D1 ). In addition, the (second) through-hole H2 is arranged at the dedendum 313 of the dedendum 312 and the dedendum 313 of the external teeth 31 . Thereby, compared with the case where the through-hole H2 is formed in the dedendum 312 , by forming the through-hole H2 in the addendum 313 , it is difficult to generate a split or the like originating in the through-hole H2 .

In addition, the through holes H1 and H2 may be provided on both the outer ring 421 and the external teeth 31 of the flexible external gear 3 . In this case, the lubricant Lb1 in the space between the outer ring 421 and the inner ring 422 of the bearing 42 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H1 . Furthermore, the lubricant Lb1 in the space between the external teeth 31 and the internal teeth 21 can be supplied to the gap X1 between the outer ring 421 and the flexible external gear 3 through the through hole H2. Therefore, the lubricant Lb1 can be supplied to the gap X1 from both sides (inside and outside) in the radial direction. Here, it is preferable that the positions of the internal teeth 21 in the tooth radial direction D1 differ between the (first) through hole H1 and the (second) through hole H2 .

In addition, the profile modification of the internal teeth 21 and the external teeth 31 is not an indispensable structure of the harmonic gear device 1 . For example, at least one of the internal teeth 21 and the external teeth 31 may not be subjected to profile modification.

In addition, it is not essential for the harmonic gear unit 1 to secure a distance equal to or greater than a predetermined value in the radial direction between the tracks of the plurality of rolling elements 423 and the opening surface of the (first) through-hole H1 provided in the outer ring 421 . indispensable structure. That is, the rolling element 423 may close the through hole H1 without a gap between the opening surface of the through hole H1 and the rolling element 423 while the rolling element 423 is present at a position corresponding to the through hole H1 .

In addition, in the bearing 42 , it is not essential for the harmonic gear device 1 that each rolling element 423 is supported at four points, and for example, each rolling element 423 may be supported at two points.

In addition, the harmonic gear unit 1 is not limited to the cup type described in the embodiment, and may be, for example, a top hat type, a ring type, a differential type, a flat type (pancake type), or a shield type. For example, even a hat-shaped harmonic gear device 1 as illustrated in FIG. 10 has a cylindrical flexible external gear 3 having an opening surface 35 on one side in the tooth direction D1 as in the cup type. That is, the hat-shaped flexible external gear 3 has a flange portion at one end of the rotation axis Ax1 and has an opening surface 35 at an end opposite to the flange portion. Even the hat-shaped flexible external gear 3 has external teeth 31 at the end on the opening surface 35 side, and the wave generator 4 is fitted therein.

In addition, the structure of the actuator 100 is not limited to the structure described in the embodiment, and can be appropriately changed. For example, the connection structure between the input unit 103 and the cam 41 is not limited to a spline connection structure, and an Oldham coupling or the like may be used. By using the Oldham coupling as the connection structure between the input part 103 and the cam 41, the eccentricity between the input side rotation axis Ax1 and the wave generator 4 (cam 41) can be canceled out, and the rigidity of the internal gear 2 and the flexibility can be further canceled out. Eccentricity of external gear 3. Furthermore, the cam 41 may not be able to move along the rotation axis Ax1 relative to the input unit 103 .

In addition, the application examples of the harmonic gear device 1, the actuator 100, and the robot joint device 130 of this embodiment are not limited to the above-mentioned horizontal articulated robot, for example, industrial robots other than the horizontal articulated robot or Robots other than those for industrial use. Among the industrial robots other than the horizontal articulated robot, there are, for example, a vertical articulated robot, a parallel link robot, and the like. Examples of robots other than industrial use include home-use robots, care-use robots, and medical-use robots.

In addition, the bearing 42 is not limited to a deep groove ball bearing, For example, an angular contact ball bearing etc. may be sufficient. Further, the bearing 42 is not limited to a ball bearing, and may be, for example, a cylindrical roller bearing in which the rolling elements 423 are not ball-shaped "rollers", a needle roller bearing, or a tapered roller bearing. Even with the rolling elements 423 other than the ball shape (spherical body shape), a pressure difference is generated by the rotation of the rolling elements 423, and the rolling elements 423 function as a pump structure.

In addition, the material of each component of the harmonic gear device 1 , the actuator 100 , or the robot joint device 130 is not limited to metal, and may be resin such as engineering plastic, for example.

In addition, the lubricant Lb1 is not limited to a liquid substance such as lubricating oil (oil), but may be a gel state substance such as grease.

In addition, the number and arrangement of the through-holes H1 are not limited to those described in the embodiment. For example, one, two, or four or more through holes H1 may be provided. Further, when a plurality of through-holes H1 are provided, the interval P1 of the plurality of through-holes H1 may also be a multiple of the interval P2 of the plurality of rolling elements 423, and it is not essential that the plurality of through-holes H1 be arranged at equal intervals. of.

In addition, the rolling roll T1 and the chuck member T2 used for processing the inner peripheral surface 301 of the flexible external gear 3 are not limited to the above-mentioned configuration, and can be appropriately changed. Similarly, the hob T3 and the tool T4 used for the machining of the external teeth 31 are not limited to the above configurations, and can be appropriately changed. As an example, the hob cutter T3 and the tool T4 may be integrated so that the row (blade row) of the hob cutter T3 including the plurality of cutting parts T32 is switched from the middle to the rib T42 of the tool T4.

As shown in FIG. 18A , FIG. 18B and FIG. 18C , the harmonic gear device 1B of this embodiment is different from the harmonic gear device 1 of the above-mentioned embodiment in that the rolling surface 200 is provided on the internal teeth 21 of the rigid internal gear 2 . . Hereinafter, the same reference numerals are assigned to the same configurations as those in Embodiment 1, and descriptions thereof are appropriately omitted. Fig. 18A is an enlarged schematic view of the area Z1 in Fig. 2B. 18B is a schematic view showing the surface state of the internal teeth 21 in the zone Z1 of FIG. 18A , and FIG. 18C is a schematic view showing the surface state of the internal teeth 21 in the zone Z2 of FIG. 18A .

That is, in the present embodiment, the rolling surface 200 is provided only on the inner teeth 21 among the outer teeth 31 and the inner teeth 21 . In other words, in the present embodiment, the rolling surface 200 is a “second rolling surface” provided on the internal teeth 21 of the rigid internal gear 2 . The (second) rolling surface 200 is also formed by processing (rolling processing) without shearing metal crystal grains, similarly to the (first) rolling surface 300 of the above-mentioned embodiment.

In addition, in the rolling surface 200 (second rolling surface) provided on the internal teeth 21, it is also the same as the rolling surface 300 (first rolling surface) of the external teeth 31, and it is preferable that the parts other than the addendum 213 ( tooth root 212, etc.) is provided with a rolling surface 300. That is, as shown in FIG. 18B , which enlarges a part of the dedendum 212 of the internal tooth 21 (area Z1 in FIG. 18A ), the dedendum 212 and the like where the rolling surface 200 is provided in the internal tooth 21 mainly become A smooth surface state where the grains are not sheared. On the other hand, as shown in FIG. 18C , which is an enlarged part of the tooth top 213 of the internal tooth 21 (region Z2 in FIG. 18A ), at the tooth top 213 where the rolling surface 200 is not provided, crystal grains are mainly sheared. surface condition. Furthermore, it was found that the surface roughness of the dedendum 212 (rolled surface 200 ) is smaller than that of the dedendum 213 .

Even in the structure in which the rolling surface 200 is provided on the internal teeth 21 as in this embodiment, since the friction between the external teeth 31 and the internal teeth 21 is reduced, the loss due to the friction between the external teeth 31 and the internal teeth 21 is also reduced. , so that the reduction in the power transmission efficiency of the harmonic gear device 1B is less likely to occur. In addition, since the surface roughness or rust caused by friction is suppressed, it is also difficult to hinder the deformation followability of the flexible external gear 3, and the rotation of the wave generator 4 is not likely to require additional energy, thereby suppressing the loss of power transmission efficiency. decline. As a result, it is possible to provide the harmonic gear device 1B in which a drop in power transmission efficiency hardly occurs.

As a modified example of the embodiment, the rolling

surfaces

200 and 300 are provided on both the internal teeth 21 and the external teeth 31 .

The structure (including modifications) of this embodiment can be applied in appropriate combination with the structures (including modifications) described in the above-mentioned embodiment.

(Summarize)

As explained above, the harmonic gear unit (1, 1A, 1B) of the first aspect includes a rigid internal gear (2), a flexible external gear (3), and a wave generator (4). The rigid internal gear (2) is an annular member having internal teeth (21). The flexible external gear (3) is an annular member having external teeth (31) and arranged inside the rigid internal gear (2). The wave generator (4) has: a non-circular cam (41) driven to rotate about a rotating shaft (Ax1); and a bearing (42) attached to the outside of the cam (41). The wave generator (4) is arranged inside the flexible external gear (3), and causes the flexible external gear (3) to bend. The harmonic gear device (1, 1A, 1B) deforms the flexible external gear (3) along with the rotation of the cam (41), so that a part of the external teeth (31) meshes with a part of the internal teeth (21), thereby making The flexible external gear (3) rotates relative to the rigid internal gear (2) according to the difference in the number of teeth of the rigid internal gear (2). In the inner peripheral surface (301) of the flexible external gear (3), the first region (R1) located on the back side of the external teeth (31) is the same as the second region (R2) other than the first region (R1). Smaller than surface roughness.

According to this aspect, occurrence of fretting wear is suppressed by preventing "lubricant depletion" in which the lubricant (Lb1) is insufficient or exhausted at the contact portion between the bearing (42) and the flexible external gear (3). Further, by providing the first region (R1) having a smaller surface roughness than the second region (R2) on the back side of the external teeth (31) in the inner peripheral surface (301) of the flexible external gear (3) , thereby maintaining sufficient lubricant (Lb1) at the contact portion of the flexible external gear (3) and the wave generator (4). As a result, the surface of the contact portion of the flexible external gear (3) with the bearing (42) is covered with the lubricant (Lb1), and the occurrence of fretting wear is suppressed. Thereby, troubles due to fretting wear between the bearing (42) and the flexible external gear (3) are less likely to occur, and a harmonic gear device (1, 1A, 1B) less prone to reliability degradation can be provided.

According to the first aspect, in the harmonic gear device (1, 1A, 1B) of the second aspect, the lubricant ( Lb1).

According to this aspect, the lubricant (Lb1) is easily maintained in the first region (R1) whose surface roughness is smaller than that of the second region (R2) due to its surface state.

According to the first or second aspect, in the harmonic gear device (1, 1A, 1B) of the third aspect, the first region (R1) is a rolling surface, and the second region (R2) is a cutting surface.

According to this aspect, the first region ( R1 ) and the second region ( R2 ) can be relatively easily realized by different processing methods.

According to any one of the first to third aspects, in the harmonic gear device (1, 1A, 1B) of the fourth aspect, the first region ( R1 ) is provided at least in a direction parallel to the rotation axis ( Ax1 ). on the entire area of the surface opposite to the outer peripheral surface (424) of the wave generator (4).

According to this mode, the entire region of the inner peripheral surface (301) of the flexible external gear (3) that is in contact with the outer peripheral surface (424) of the wave generator (4) is defined as the first region ( R1 ), whereby It is easy to further suppress the occurrence of fretting wear.

According to any one of the first to fourth forms, in the harmonic gear device (1, 1A, 1B) of the fifth form, the flexible external gear (3) is in the tooth direction (D1 ) has a cylindrical shape with an open face (35) on one side. The first region (R1) is connected to the opening surface (35).

According to this aspect, it is easy to fit the wave generator (4) into the flexible external gear (3) from the opening surface (35) side.

According to any one of the first to fifth aspects, in the harmonic gear device (1, 1A, 1B) of the sixth aspect, the surface roughness of the first region (R1) is equal to the surface roughness of the second region (R2). 1/40 times or more and 1/10 times or less of the roughness.

According to this aspect, the first region ( R1 ) can have a surface roughness suitable for suppression of fretting wear.

According to any one of the first to sixth aspects, in the harmonic gear device (1, 1A, 1B) of the seventh aspect, the outer ring (421) of the bearing (42) and the flexible external gear (3) At least one of the outer teeth (31) in the middle is provided with a through hole (H1, H2), and the through hole (H1, H2) penetrates along the radial direction and is connected with the outer ring (421) and the flexible outer ring. The gap (X1) between the gears (3) is connected.

According to this aspect, the lubricant (Lb1) can be supplied to the gap (X1) between the outer ring (421) and the flexible external gear (3) through the through holes (H1, H2). Thus, by preventing "lubricant depletion" in which the lubricant (Lb1) is insufficient or exhausted at the contact portion between the outer ring (421) and the flexible external gear (3), the occurrence of fretting wear can be further suppressed.

A method of manufacturing a harmonic gear device (1, 1A, 1B) according to an eighth aspect is a method of manufacturing a harmonic gear device (1, 1A, 1B) according to any one of the first to seventh aspects, and includes a preparation step and Plastic processing process. In the preparation step, a base material (3A) to be the base of the flexible external gear (3) is prepared. In the plastic working step, the first region (R1) is formed on the inner peripheral surface (301) of the base material (3A) by plastic working.

According to this aspect, troubles caused by fretting wear between the bearing (42) and the flexible external gear (3) are less likely to occur, and it is possible to provide a harmonic gear device (1, 1A, 1B) that is less likely to cause a decrease in reliability. ).

According to the eighth aspect, in the method of manufacturing the harmonic gear device (1, 1A, 1B) of the ninth aspect, the external teeth (31) are further formed on the outer peripheral surface of the base material (3A) after the plastic working step.

According to this aspect, it is easy to avoid deformation of the external teeth (31) during the plastic working process.

According to the eighth or ninth aspect, the method of manufacturing the harmonic gear unit (1, 1A, 1B) of the tenth aspect further includes a clamping step. In the clamping process, at least during the plastic working process, the base material (3A) is clamped by the chuck member ( T2 ) from the outer peripheral surface side.

According to this aspect, since the base material (3A) is supported by the chuck member ( T2 ) from the outer peripheral surface side, it is easy to roll the inner peripheral surface ( 301 ) of the base material ( 3A).

According to the tenth aspect, in the method of manufacturing the harmonic gear device (1, 1A, 1B) of the eleventh aspect, the chuck member (T2) has an inner periphery having a shape corresponding to the outer peripheral surface of the base material (3A) surface (T221), and is configured to be divided into a plurality of single pieces (T22) in the circumferential direction.

According to this configuration, the chuck member ( T2 ) can receive rolling force over the entire area of the outer peripheral surface of the base material ( 3A).

A robot joint device (130) of a twelfth aspect includes: the harmonic gear device (1, 1A, 1B) of any one of the first to seventh aspects; a first member (131) fixed to a rigid internal gear (2) ); and a second member (132) fixed to the flexible external gear (3).

According to this aspect, troubles due to fretting wear between the bearing (42) and the flexible external gear (3) are less likely to occur, and it is possible to provide a robot joint device (130) in which reliability is less likely to be lowered.

The gear member of the thirteenth aspect is used as the flexible external gear (3) of the harmonic gear device (1, 1A, 1B) of any one of the first to seventh aspects.

According to this aspect, troubles due to fretting wear between the bearing (42) and the flexible external gear (3) are less likely to occur, and it is possible to provide a gear component that is less likely to decrease in reliability.

The configurations of the second to seventh aspects are not indispensable for the harmonic gear device (1, 1A, 1B), and can be appropriately omitted. The configurations of the ninth to eleventh aspects are not indispensable to the manufacturing method of the harmonic gear device (1, 1A, 1B), and can be appropriately omitted.

Explanation of reference signs

1, 1A, 1B harmonic gear device

2 rigid internal gears

3 flexible external gear (gear part)

3A substrate

4 wave generator

21 internal teeth

31 external teeth

35 open face

41 cam

42 bearings

130 robot joint device

131 first member

132 second component

301 (flexible external gear) inner peripheral surface

421 outer ring

424 (outer ring) outer peripheral surface

Ax1 rotation axis

D1 tooth direction

H1 (first) through hole

H2 (second) through hole

Lb1 lubricant

R1 first area

R2 second area

T2 chuck member

T22 monolithic

T221 (chuck member) inner peripheral surface

X1 clearance

Industrial Applicability

According to the embodiments of the present disclosure, it is possible to provide a harmonic gear device, a method of manufacturing a harmonic gear device, a joint device for a robot, and a gear component in which reliability degradation hardly occurs.

Claims

A harmonic gear device comprising:

an annular rigid internal gear having internal teeth;

an annular flexible external gear having external teeth and disposed inside said rigid internal gear; and

The wave generator has a non-circular cam driven to rotate about a rotating shaft, and a bearing mounted on the outside of the cam, and the wave generator is arranged inside the flexible external gear so that the The flexible external gear flexes,

As the cam rotates, the flexible external gear is deformed so that a part of the external teeth meshes with a part of the internal teeth so that the flexible external gear has the same number of teeth as the rigid internal gear. difference while performing relative rotation with respect to the rigid internal gear, where,

A first region on the inner peripheral surface of the flexible external gear located on the back side of the external teeth has a smaller surface roughness than a second region other than the first region.
The harmonic gear device according to claim 1, wherein,

A lubricant is retained between the first region and the outer peripheral surface of the wave generator.
The harmonic gear device according to claim 1 or 2, wherein,

The first area is a rolling surface, and the second area is a cutting surface.
The harmonic gear device according to any one of claims 1 to 3, wherein:

The first region is provided over an entire region of a surface opposite to an outer peripheral surface of the wave generator at least in a direction parallel to the rotation axis.
The harmonic gear device according to any one of claims 1 to 4, wherein:

The flexible external gear has a cylindrical shape with an open surface on one side in the tooth direction of the external teeth, wherein

The first region is connected to the opening surface.
The harmonic gear device according to any one of claims 1 to 5, wherein:

The surface roughness of the first region is 1/40 to 1/10 times the surface roughness of the second region.
The harmonic gear device according to any one of claims 1 to 6, wherein:

At least one of the outer ring of the bearing and the outer teeth of the flexible external gear is provided with a through hole that penetrates in the radial direction and is connected to the outer ring and the outer teeth of the flexible external gear. The gaps between the flexible external gears are connected.
A manufacturing method of a harmonic gear device is the manufacturing method of a harmonic gear device according to any one of claims 1 to 7, wherein the manufacturing method comprises:

a preparation process of preparing a base material to be a base of said flexible external gear; and

In the plastic working step, the first region is formed by plastic working on the inner peripheral surface of the base material.
The method of manufacturing a harmonic gear device according to claim 8, wherein,

After the plastic working step, there is a step of forming the external teeth on the outer peripheral surface of the base material.
The method of manufacturing a harmonic gear device according to claim 8 or 9, wherein,

It also has a chucking step of chucking the base material from the outer peripheral surface side with a chuck member at least during the plastic working step.
The method of manufacturing a harmonic gear device according to claim 10, wherein,

The chuck member has an inner peripheral surface having a shape corresponding to the outer peripheral surface of the base material, and the chuck member is configured to be divisible into a plurality of individual pieces in the circumferential direction.
A joint device for a robot, including:

The harmonic gear device according to any one of claims 1-7;

a first member fixed to said rigid internal gear; and

The second member is fixed to the flexible external gear.
A gear component used as the flexible external gear of the harmonic gear device according to any one of claims 1 to 7.