CN115461560A - Harmonic gear device, actuator, and cover - Google Patents

Abstract

A harmonic gear device (1) is configured such that, as a wave generator (4) rotates about a rotation axis (Ax 1), a flexible externally toothed gear (3) is deformed, and a portion of external teeth (31) and a portion of internal teeth (21) mesh with each other, so that the flexible externally toothed gear (3) rotates relative to a rigid internally toothed gear (2) in accordance with the difference in the number of teeth between the flexible externally toothed gear and the rigid internally toothed gear (2). The wave generator (4) has: a non-circular cam (41) that is rotationally driven around a rotation axis (Ax 1); and a bearing (42) disposed between the outer peripheral surface (411) of the cam (41) and the inner peripheral surface (301) of the circular flexible externally toothed gear (3). The harmonic gear device (1) further comprises a cover member (5), and the cover member (5) is disposed so as to face the bearing (42) from one side of the rotating shaft (Ax 1). The cover member (5) faces the bearing (42) with a gap (G1) secured between the cover member and the outer ring (421) of the bearing (42), and prevents foreign matter (X1) from entering the inner side of the outer ring (421) from one side of the rotation axis Axl.

Description

Harmonic gear device, actuator, and cover

Cross Reference to Related Applications

This application is filed and claimed based on japanese patent application having application No. 2020-078964 filed on 28/04/2020, the entire contents of which are incorporated herein by reference.

Technical Field

Embodiments of the present disclosure relate to a harmonic gear device, an actuator, and a cover, and more particularly, to a harmonic gear device, an actuator, and a cover including a rigid internal gear, a flexible external gear, and a wave generator.

Background

Patent document 1 discloses surface treatment of a flexible externally toothed gear in a harmonic gear device (a flex-mesh gear device) by nitriding.

The harmonic gear device includes: an annular rigid internal gear; a cup-shaped flexible external gear disposed inside the flexible external gear; and an elliptical wave generator embedded inside thereof. The circular flexible externally toothed gear includes a cylindrical body portion and external teeth formed on an outer peripheral surface of the body portion. The flexible externally toothed gear is bent into an elliptical shape by the wave generator, and portions of the external teeth located at both ends in the major axis direction of the elliptical shape mesh with internal teeth formed on the inner circumferential surface of the rigid internally toothed gear.

When the wave generator is rotated by a motor or the like, the meshing positions of the two gears move in the circumferential direction, and relative rotation corresponding to the difference in the number of teeth of the internal teeth and the external teeth (2N (N is a positive integer)) is generated between the two gears. Here, when the rigid internal gear side is fixed, a rotation output that is greatly decelerated in accordance with the difference in the number of teeth of the two gears can be obtained from the flexible external gear side.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2001-59153

Disclosure of Invention

However, in the harmonic gear device, since the transmission of the power is performed by the engagement of the internal teeth and the external teeth while the flexible externally toothed gear is flexed, foreign substances such as metal powder and nitrides may be generated due to abrasion and the like generated between the internal teeth and the external teeth, particularly if used for a long period of time. If such foreign matter enters the bearing of the wave generator, damage may occur on the surface of any one of the outer ring, the inner ring, and the rolling elements (balls) of the bearing, and the reliability of the harmonic gear device may be affected.

The present embodiment has been made in view of the above circumstances, and an object thereof is to provide a highly reliable harmonic gear device, an actuator, and a cover.

Means for solving the technical problem

A harmonic gear device according to an aspect of the present disclosure includes: an annular rigid internal gear having internal teeth; an annular flexible externally toothed gear having external teeth and disposed inside the rigid internally toothed gear; and a wave generator disposed inside the circular flexible external gear and configured to flex the circular flexible external gear. The harmonic gear device deforms the flexible externally toothed gear in accordance with rotation of the wave generator about a rotation axis, and causes a part of the external teeth to mesh with a part of the internal teeth, thereby causing the flexible externally toothed gear to rotate relative to the rigid internally toothed gear in accordance with a difference in the number of teeth between the flexible externally toothed gear and the rigid internally toothed gear. The wave generator has: a non-circular cam that is driven to rotate about the rotation axis; and a bearing disposed between an outer peripheral surface of the cam and an inner peripheral surface of the circular flexible externally toothed gear. The harmonic gear device further includes a cover member disposed to face the bearing from one side of the rotation shaft. The cover member faces the bearing while maintaining a gap between the cover member and an outer ring of the bearing, and prevents foreign matter from entering an inner side of the outer ring from one side of the rotary shaft.

An actuator according to an aspect of the present disclosure includes: the harmonic gear device; a drive source that rotates the cam; and an output section that outputs the rotational force of the circular flexible external gear.

A cover according to an aspect of the disclosed embodiment is configured such that the harmonic gear device serves as the cover member.

Effects of the invention

According to the embodiments of the present disclosure, there is an advantage in that reduction in reliability is avoided, thereby achieving high reliability.

Drawings

Fig. 1A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to a first embodiment. Fig. 1B is an enlarged view of a region Z1 of fig. 1A.

Fig. 2A is a schematic view of the harmonic gear device as viewed from the input shaft of the rotary shaft with the cover member removed. Fig. 2B is a schematic view of the harmonic gear device as viewed from the input side of the rotary shaft.

Fig. 3A is a schematic exploded perspective view of the harmonic gear device as viewed from the output side of the rotary shaft. Fig. 3B is a schematic exploded perspective view of the harmonic gear device as viewed from the input side of the rotary shaft.

Fig. 4 is a sectional view showing a schematic configuration of an actuator including the harmonic gear device.

Fig. 5A and 5B are enlarged views of the periphery of the umbrella part of the cover member in the harmonic gear device.

Fig. 6 is a cross-sectional view showing an example of a robot using the harmonic gear device.

Fig. 7A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to a second embodiment. Fig. 7B is an enlarged view of a main portion of fig. 7A.

Fig. 8A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to a first modification of the second embodiment. Fig. 8B is an enlarged view of a main portion of fig. 8A.

Fig. 9A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to a second modification of the second embodiment. Fig. 9B is an enlarged view of a main portion of fig. 9A.

Fig. 10A, 10B, and 10C are sectional views of main portions of a schematic configuration of a harmonic gear device according to third, fourth, and fifth modifications of the second embodiment, respectively.

Fig. 11A is a cross-sectional view showing a schematic configuration of a harmonic gear device according to a third embodiment. Fig. 11B is an enlarged view of a main portion of fig. 11A.

Detailed Description

(embodiment mode)

(1) Summary of the invention

The outline of the harmonic gear device 1 according to the present embodiment will be described below with reference to fig. 1A to 4. The drawings referred to in the embodiments of the present disclosure are schematic drawings, and the ratio of each size and thickness of each structural element in the drawings is not necessarily limited to reflect an actual dimensional ratio. For example, the tooth shapes, sizes, numbers of teeth, and the like of the internal teeth 21 and the external teeth 31 in fig. 2A to 3B are schematically illustrated for explanation only, and the gist thereof is not limited to the illustrated shapes.

The 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 the harmonic gear device 1, an annular flexible externally toothed gear 3 is disposed inside an annular rigid internally toothed gear 2, and a wave generator 4 is further disposed inside the flexible externally toothed gear 3. The wave generator 4 causes the external teeth 31 of the flexible externally toothed gear 3 to partially mesh with the internal teeth 21 of the rigid internally toothed gear 2 by flexing the flexible externally toothed 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 in the circumferential direction of the rigid internal gear 2, and relative rotation is generated between the two gears (the rigid internal gear 2 and the flexible external gear 3) such that the flexible external gear 3 follows the difference in the number of teeth from the rigid internal gear 2. Here, if the rigid internally toothed gear 2 is fixed, the circular externally toothed flexible gear 3 rotates along with the relative rotation of the two gears. As a result, a rotation output reduced in speed at a relatively high reduction ratio according to the difference in the number of teeth of the two gears can be obtained from the circular flexible externally toothed gear 3.

The wave generator 4 that deflects the circular flexible externally toothed gear 3 includes a non-circular cam 41 that is driven to rotate about the input-side rotation axis Ax1 (see fig. 1A), and a bearing 42. The bearing 42 is disposed between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the circular flexible externally toothed gear 3. The inner ring 422 of the bearing 42 is fixed to 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 rolling elements 423 of a ball shape and elastically deformed. Here, since the outer ring 421 can rotate relative to the inner ring 422 by the rolling elements 423 rolling, when the non-circular cam 41 rotates, the rotation of the inner ring 422 is not transmitted to the outer ring 421, but the external teeth 31 of the circular flexible externally toothed gear 3 pressed by the cam 41 fluctuate. Since the wave 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 as described above, so that relative rotation occurs between the flexible externally toothed gear 3 and the rigid internally toothed gear 2.

In short, in the harmonic gear device 1, the wave generator 4 having the bearing 42 realizes power transmission by meshing of the internal teeth 21 and the external teeth 31 while flexing the flexible externally toothed gear 3. Therefore, if used for a long period of time in particular, foreign matter X1 such as metal powder or nitride may be generated due to abrasion or the like generated between the internal teeth 21 and the external teeth 31 (see fig. 5A). If such foreign matter X1 enters the bearing 42, damage may occur on the surface of any one of the outer ring 421, the inner ring 422, and the rolling elements 423 of the bearing 42, thereby affecting the reliability of the harmonic gear device 1. The harmonic gear device 1 according to the present embodiment mainly suppresses entry of foreign matter X1 into the bearing 42 by the following configuration, and thus does not reduce reliability.

That is, as shown in fig. 1A to 3B, the harmonic gear device 1 according to the present embodiment includes: an annular rigid internal gear 2 having internal teeth 21; an annular circular flexible externally toothed gear 3 having external teeth 31; and a wave generator 4. The circular flexible external gear 3 is disposed inside the circular rigid internal gear 2. The harmonic gear device 1 deforms the flexible externally toothed gear 3 in accordance with the rotation of the wave generator 4 about the rotation axis Ax1, and causes a part of the external teeth 31 to mesh with a part of the internal teeth 21, thereby rotating the flexible externally toothed gear 3 in accordance with the difference in the number of teeth from the rigid internally toothed gear 2. The wave generator 4 has a bearing 42 and a cam 41 of a non-circular shape. The cam 41 is rotationally driven around the rotation axis Ax1. The bearing 42 is disposed between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the circular flexible externally toothed gear 3. The harmonic gear device 1 further includes a cover member 5. The cover member 5 is disposed to face the bearing 42 from one side of the rotation axis Ax1. The cover member 5 faces the bearing 42 with a gap G1 (see fig. 1B) secured between the cover member and the outer ring 421 of the bearing 42, and prevents foreign matter X1 from entering the inner side of the outer ring 421 from one side of the rotation axis Ax1.

According to this aspect, the cover member 5 disposed so as to face the bearing 42 from one side of the rotary shaft Ax1 can prevent the foreign matter X1 from entering the inside of the outer ring 421 of the bearing 42 from one side of the rotary shaft Ax1. Therefore, even if foreign matter X1 such as metal powder or nitride is generated due to abrasion or the like generated between the internal teeth 21 and the external teeth 31 by use of the harmonic gear device 1 for a long period of time, it is possible to suppress such foreign matter X1 from entering the bearing 42 (inside the outer ring 421). As a result, it is difficult for the foreign matter X1 to damage the surfaces of the outer ring 421, the inner ring 422, the rolling elements 423, and the like of the bearing 42, and the reliability of the harmonic gear device 1 is not reduced by the damage of the bearing 42. Thus, the harmonic gear device 1 according to the present embodiment has an advantage of high reliability. Further, according to the harmonic gear device 1 of the present embodiment, since reliability is not lowered even when the harmonic gear device is used for a long period of time, the harmonic gear device 1 can be extended in life and improved in performance.

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 according to the present embodiment includes the harmonic gear device 1, the drive source 101, and the output unit 102. The drive source 101 rotates the cam 41. The output portion 102 takes out the rotational force of the circular flexible externally toothed gear 3 as an output.

The cover member 5 of the harmonic gear device 1 according to the present embodiment constitutes a cover 10 (see fig. 1A). In other words, the lid 10 according to the present embodiment is used as the lid member 5 in the harmonic gear device 1. That is, the lid 10 is the lid member 5.

According to the actuator 100 and the cover 10 according to the present embodiment, the harmonic gear device 1 has an advantage of high reliability.

(2) Definition of

The "annular shape" mentioned in the embodiments of the present disclosure is a shape such as a ring (ring) in which a space (region) surrounded by the inner side is formed at least in a plan view, and is not limited to a circular shape (annular shape) which is a perfect circle in a plan view, and may be, for example, an elliptical shape, a polygonal shape, or the like. Further, for example, the circular flexspline 3 may have a shape having a bottom portion 322 like the cup-shaped flexspline 3, and if the body portion 321 is circular, it is referred to as a "circular" flexspline 3.

The term "block" as used in the embodiments of the present disclosure means to block or obstruct, and does not mean to completely block or obstruct. That is, the cover member 5 that blocks the foreign matter X1 from entering the inner side of the outer ring 421 only needs to block the foreign matter X1 from entering the inner side of the outer ring 421, and does not necessarily completely block the foreign matter X1. In other words, by providing the cover member 5, it is only necessary to suppress the foreign matter X1 from entering the inside of the outer ring 421, and as a result, the amount of the foreign matter X1 entering the inside of the outer ring 421 can be reduced. Of course, the entry of the foreign matter X1 into the inside of the outer ring 421 may be completely intercepted by the cover member 5.

The "foreign matter" mentioned in the embodiment of the present disclosure is a substance other than the original structural elements of the harmonic gear device 1, and includes, as an example thereof, metal powder, nitride, or the like generated by abrasion between the internal teeth 21 and the external teeth 31. That is, the foreign matter X1 that is blocked from entering the inside of the outer ring 421 by the cover member 5 is not limited to a substance generated by abrasion inside the harmonic gear device 1, and includes, for example, dust, sand dust, or dirt entering from the outside of the harmonic gear device 1.

The "rigidity" referred to in the embodiments of the present disclosure means a property of an object against deformation when an external force is applied to the object and the object is to be deformed. In other words, an object having rigidity is hard to deform even if an external force is applied. In addition, "flexibility" referred to in the embodiments of the present disclosure means a property that an object is elastically deformed (flexed) when an external force is applied to the object. In other words, an object having flexibility is easily elastically deformed when an external force is applied thereto. Thus, "rigid" and "flexible" are opposite meanings.

Particularly in the present disclosed embodiment, the "rigidity" of the rigid internal gear 2 and the "flexibility" of the circular flexible external gear 3 are used in opposite senses. That is, the "rigidity" of the rigid internal gear 2 means that the rigid internal gear 2 has relatively high rigidity, that is, is hard to deform even if an external force is applied to the rigid internal gear 2, as compared with at least the circular flexible external gear 3. Also, the "flexibility" of the circular flexible externally toothed gear 3 means that the circular flexible externally toothed gear 3 has relatively high flexibility at least as compared with the rigid internally toothed gear 2, that is, the circular flexible externally toothed gear 3 is easily elastically deformed when an external force is applied.

In the embodiment of the present disclosure, one side of the rotating shaft Ax1 (the right side in fig. 1A) may be referred to as an "input side", and the other side of the rotating shaft Ax1 (the left side in fig. 1A) may be referred to as an "output side". That is, in the example of fig. 1A, the cover member 5 is disposed opposite to the bearing 42 from the "input side" of the rotation axis Ax1. However, the "input side" and the "output side" are merely labels given for the purpose of explanation, and the gist thereof is not limited to the positional relationship between the input and the output as viewed from the harmonic gear device 1.

The "non-circular shape" referred to in the embodiments of the present disclosure means a shape that is not a perfect circle, including, for example, an elliptical shape, an oblong shape, and the like. In the present embodiment, the non-circular cam 41 of the wave generator 4 is elliptical. That is, in the present embodiment, the wave generator 4 bends the circular flexible externally toothed gear 3 into an elliptical shape.

The term "elliptical shape" as used in the embodiments of the present disclosure refers to an overall shape in which a perfect circle is flattened so that an intersection point of a major axis and a minor axis perpendicular to each other is located at the center, and is not limited to a mathematical "ellipse" which is a curve composed of a set of points whose sum of distances to two fixed points on one plane is constant. That is, the cam 41 in the present embodiment may be in a curved shape composed of a set of points whose sum of distances to two fixed points on one plane is constant, such as a mathematical "ellipse", or may be in an elliptical shape such as an oval, not a mathematical "ellipse". As described above, the drawings referred to in the embodiments of the present disclosure are schematic views, and the respective ratios of the size and the thickness of each structural element in the drawings are not necessarily limited to reflect actual dimensional ratios. As described above, the drawings referred to in the embodiments of the present disclosure are schematic views, and the respective ratios of the size and the thickness of each structural element in the drawings are not necessarily limited to reflect actual dimensional ratios.

The "rotation axis" referred to in the embodiments of the present disclosure means 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 not accompanied by a solid body. The wave generator 4 performs a rotational motion around the rotation axis Ax1.

The "internal teeth" and "external teeth" mentioned in the embodiments of the present disclosure refer to a set (group) of a plurality of "teeth" respectively, rather than the "teeth" of a single body. That is, the internal teeth 21 of the rigid internal gear 2 include a set of a plurality of teeth formed on the inner peripheral surface of the rigid internal gear 2. Likewise, the external teeth 31 of the circular flexible externally toothed gear 3 include a set of a plurality of teeth formed on the outer peripheral surface of the circular flexible externally toothed gear 3.

(3) Form a

The detailed configurations of the harmonic gear device 1 and the actuator 100 according to the present embodiment will be described below with reference to fig. 1A to 4.

Fig. 1A is a sectional view showing a schematic configuration of the harmonic gear device 1, and fig. 1B is an enlarged view of a region Z1 of fig. 1A. Fig. 2A is a schematic view of the harmonic gear device 1 in a state where the cover member 5 is removed, as viewed from the input side (right side in fig. 1A) of the rotation axis Ax1. Fig. 2B is a schematic diagram of the harmonic gear device 1 including the cover member 5, as viewed from the input side of the rotation axis Ax1. Fig. 3A is a schematic exploded perspective view of the harmonic gear device 1 as viewed from the output side (left side in fig. 1A) of the rotation shaft Ax1. Fig. 3B is a schematic exploded perspective view of the harmonic gear device 1 as viewed from the input side of the rotation shaft Ax1. Fig. 4 is a sectional view showing a schematic configuration of an actuator 100 including the harmonic gear device 1.

(3.1) harmonic Gear device

As described above, the harmonic gear device 1 according to the present embodiment includes the rigid internal gear 2, the flexible external gear 3, the wave generator 4, and the cover member 5. In the present embodiment, the rigid internal gear 2, the flexible external gear 3, the wave generator 4, and the cover member 5, which are the constituent elements of the harmonic gear device 1, are made of a metal such as stainless steel, cast iron, mechanical structural carbon steel, chrome molybdenum steel, phosphor bronze, or aluminum bronze. The metal here includes a metal subjected to surface treatment such as nitriding.

In the present embodiment, a cup-shaped harmonic gear device is exemplified as an example of the harmonic gear device 1. That is, the flexspline 3 formed in a cup shape is used in the harmonic gear device 1 according to the present embodiment. The wave generator 4 is combined with the circular flexible external gear 3 so as to be housed inside the cup-shaped circular flexible external gear 3.

In addition, as an example of the present embodiment, the harmonic gear device 1 is used in a state where 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. As a result, the circular flexible externally toothed gear 3 rotates relative to the fixed member (the input-side housing 111, etc.) in accordance with the relative rotation between the circular rigid internally toothed gear 2 and the circular flexible externally toothed gear 3.

Further, in the present embodiment, when the harmonic gear device 1 is used in the actuator 100, the rotational force can be extracted as the output from the circular flexible externally toothed gear 3 by applying the rotational force as the input to the wave generator 4. That is, the harmonic gear device 1 operates with the rotation of the wave generator 4 as input rotation and the rotation of the circular flexible externally toothed gear 3 as output rotation. As a result, the harmonic gear device 1 can obtain output rotation that is decelerated at a high reduction ratio with respect to input rotation.

Further, in the harmonic gear device 1 according to the present embodiment, the input-side rotation shaft Ax1 and the output-side rotation shaft Ax2 are on the same straight line. In other words, the input-side rotation axis Ax1 and the output-side rotation axis Ax2 are coaxial. Here, the input-side rotation axis Ax1 is a rotation center of the wave generator 4 to which input rotation is applied, and the output-side rotation axis Ax1 is a rotation center of the circular flexible externally toothed gear 3 that generates output rotation. That is, in the harmonic gear device 1, the output rotation decelerated at a high speed reduction ratio with respect to the input rotation can be obtained coaxially.

The rigid internal gear 2 is also called a circular spline (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 perfectly circular in a plan view. Internal teeth 21 are formed on the inner circumferential surface of the annular rigid internal gear 2 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 circumferential area of the inner circumferential surface of the rigid internal gear 2. That is, the pitch circle of the internal teeth 21 is a perfect circle in a plan view. The rigid internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. The internal teeth 21 are formed over the entire length of the rigid internal gear 2 in the thickness direction. The tooth trace of the internal teeth 21 is parallel to the rotational 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.

The circular flexible external gear 3 is also called a flex spline (flex spline), and is an annular member having an external tooth 31. In the present embodiment, the circular flexible externally toothed gear 3 is formed in a cup shape using a relatively thin metal elastic body (metal plate). That is, the circular flexible externally toothed gear 3 possesses flexibility because its thickness is relatively small (thin). The circular flexible externally toothed gear 3 has a cup-shaped body portion 32. The main body portion 32 has a body portion 321 and a bottom portion 322. At least the inner peripheral surface 301 of the body portion 321 has a cylindrical shape that is a perfect circle in a plan view in a state where the circular flexible externally toothed gear 3 is not elastically deformed. The central axis of the body 321 coincides with the rotation axis Ax1. The bottom portion 322 is disposed on one opening surface of the body portion 321, and has a circular disk shape in plan view. The bottom portion 322 is disposed on the output-side opening surface closer to the rotation axis Ax1, of the pair of opening surfaces of the body portion 321. As described above, the body portion 32 has a bottomed cylindrical shape, i.e., a cup shape, which is open to the input side of the rotation axis Ax1, through the entirety of the body portion 321 and the bottom portion 322. In the present embodiment, the body 321 and the bottom 322 are integrally formed of one metal member, and thus the seamless main body 32 can be realized.

Here, the wave generator 4 is combined with the circular flexible externally toothed gear 3 so that the wave generator 4 having a non-circular shape (an elliptical shape) is fitted inside the body 321. As a result, the circular flexible externally toothed gear 3 is elastically deformed into a non-circular shape by receiving an external force in a radial direction (a direction orthogonal to the rotation axis Ax 1) from the wave generator 4 from the inside toward the outside. In the present embodiment, the wave generator 4 is combined with the circular flexible externally toothed gear 3, whereby the body portion 321 of the circular flexible externally toothed gear 3 is elastically deformed into an elliptical shape. That is, the state in which the circular flexible externally toothed gear 3 is not elastically deformed means a state in which the wave generator 4 is not combined with the circular flexible externally toothed gear 3. In contrast, the state in which the circular flexible external gear 3 is elastically deformed means a state in which the wave generator 4 and the circular flexible external gear 3 are combined.

At least an end portion of the outer peripheral surface of the body portion 321 on the side opposite to the bottom portion 322 (the input side of the rotation axis Ax 1) is formed with external teeth 31 along the circumferential direction of the body portion 321. The plurality of teeth constituting the external teeth 31 are all of the same shape, and are provided at equal intervals over the entire circumferential region of the outer circumferential surface of the circular flexible externally toothed gear 3. That is, the pitch circle of the external teeth 31 is a perfect circle in a plan view in a state where the circular flexible externally toothed gear 3 is not elastically deformed. The external teeth 31 are formed only in a range having a constant width from the end edge of the opening side (the input side of the rotation axis Ax 1) of the body portion 321. The tooth trace of the external teeth 31 is parallel to the rotational axis Ax1.

As described above, in the present embodiment, the rotation of the circular flexible externally toothed gear 3 is extracted as the output rotation. Therefore, the output portion 102 of the actuator 100 is attached to the circular flexible externally toothed gear 3 (see fig. 4). A plurality of mounting holes 33 for mounting shafts of the output portion 102 are formed in the bottom portion 322 of the circular flexible externally toothed gear 3. Further, a through hole 34 is formed in the center of the bottom portion 322. The periphery of the through-hole 34 in the bottom portion 322 is thicker than the other portions of the bottom portion 322.

The circular flexible external gear 3 configured as described above is disposed inside the rigid internal gear 2. Here, the circular flexible externally toothed gear 3 is combined with the rigid internally toothed gear 2 so that only an end portion of the outer peripheral surface of the body portion 321 on the side opposite to the bottom portion 322 (the input side of the rotation axis Ax 1) is inserted inside the rigid internally toothed gear 2. Here, the external teeth 31 are formed on the outer peripheral surface of the circular flexible externally toothed gear 3, and the internal teeth 21 are formed on the inner peripheral surface of the rigid internally toothed gear 2. Therefore, in a state where the circular flexible externally toothed gear 3 is disposed inside the rigid internally toothed gear 2, the external teeth 31 and the internal teeth 21 face each other.

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

In the present embodiment, for example, the dimension in the tooth trace direction of the external teeth 31 (the direction parallel to the rotation axis Ax 1) is smaller than the dimension in the tooth trace direction of the internal teeth 21 (the direction parallel to the rotation axis Ax 1). In other words, the external teeth 31 are accommodated within the range of the tooth trace of the internal teeth 21 in the direction parallel to the rotation axis Ax1.

However, in a state where the circular flexible externally toothed gear 3 is not elastically deformed (a state where the wave generator 4 is not combined with the circular flexible externally toothed gear 3), the pitch circle of the external teeth 31 that draw a perfect circle is set to be one smaller than the pitch circle of the internal teeth 21 that also draw a perfect circle. That is, in a state where the circular flexible externally toothed gear 3 is not elastically deformed, the external teeth 31 and the internal teeth 21 face each other with a gap therebetween and do not mesh with each other.

On the other hand, in a state where the flexible externally toothed gear 3 is elastically deformed (a state where the wave generator 4 and the flexible externally toothed gear 3 are combined), the body portion 321 is flexed into an elliptical shape (non-circular shape), so that the external teeth 31 of the flexible externally toothed gear 3 and the internal teeth 21 of the rigid internally toothed gear 2 are partially engaged with each other. That is, as shown in fig. 2A, since (the body portion 321 of) the circular flexible externally toothed gear 3 is elastically deformed into an elliptical shape, the external teeth 31 located at both ends in the longitudinal direction of the elliptical shape mesh with the internal teeth 21. In other words, the major diameter of the pitch circle of the elliptical external teeth 31 matches 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 the diameter of the pitch circle of the perfect circular internal teeth 21. In this manner, when the circular flexible externally toothed 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. As a result, in the harmonic gear device 1, a part of the external teeth 31 can mesh with a part of the internal teeth 21.

The wave generator 4 is also called a wave generator (wave generator), and is a component that generates a wave motion in the external teeth 31 of the circular flexible external gear 3 by flexing the circular flexible external gear 3. In the present embodiment, the wave generator 4 is a member having an outer peripheral shape of a non-circular shape, specifically, an elliptical shape in a plan view.

The wave generator 4 has a cam 41 of 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 to form the cam 41 having a non-circular shape (elliptical shape) which is fitted inside the inner race 422 of the bearing 42. Thereby, the bearing 42 receives an external force in the radial direction (the direction orthogonal to the rotation axis Ax 1) from the cam 41 toward the outside from the inside of the inner ring 422, and is elastically deformed into a non-circular shape. That is, the state in which the bearing 42 is not elastically deformed refers to a state in which the cam 41 is not combined with the bearing 42. Conversely, the state in which the bearing 42 is elastically deformed means a state in which the cam 41 and the bearing 42 are combined.

The cam 41 is a member having a non-circular shape (here, an elliptical shape) and driven to rotate about the input-side rotation 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 a metal plate having an elliptical shape in a plan view. The cam 41 has a predetermined thickness in the direction of the rotation axis Ax1. Thereby, the cam 41 has the same degree of rigidity as the rigid internal gear 2. However, the thickness of the cam 41 is small (thin) compared to the thickness 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, an input unit 103 of the actuator 100 (see fig. 4) is attached to the wave generator 4. A cam hole 43 for mounting a shaft as the input portion 103 is formed in the center portion 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 bodies 423. In the present embodiment, the bearing 42 includes a deep groove ball bearing using balls as the rolling elements 423, for example.

The outer ring 421 and the inner ring 422 are both annular members. The outer ring 421 and the inner ring 422 are both formed annularly using a thin-walled metal elastic body (metal plate). That is, both the outer ring 421 and the inner ring 422 have flexibility because of their small (thin) thickness. In the present embodiment, the outer ring 421 and the inner ring 422 both have a perfect circular ring shape in plan view in a state where the bearing 42 is not elastically deformed (a state where the cam 41 is not combined with the bearing 42). The inner ring 422 is smaller than the outer ring 421 by one turn 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 formed between the inner peripheral surface of the outer ring 421 and the outer peripheral surface of the inner ring 422.

The 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 in a circumferential direction of the outer ring 421. The plurality of rolling elements 423 are metal balls (balls) having the same shape, and are provided at equal intervals over the entire circumferential area of the outer ring 421. Although not particularly shown here, the bearing 42 further includes a retainer, and the plurality of rolling elements 423 are retained between the outer ring 421 and the inner ring 422 by the retainer.

In addition, as an example of the present embodiment, the dimension in the width direction of the inner ring 422 (the direction parallel to the rotation axis Ax 1) is the same as the thickness of the cam 41. The dimension in the width direction of the outer ring 421 (the direction parallel to the rotation axis Ax 1) is larger than the dimension in the width direction of the inner ring 422. In the present embodiment, as shown in fig. 1B, the outer ring 421 and the inner ring 422 are in a positional relationship such that the end surface on the output side of the rotating shaft Ax1 is flush with each other, and therefore the outer ring 421 protrudes from the inner ring 422 on the input side of the rotating shaft Ax1. Further, the dimension of the outer ring 421 in the width direction is 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 race 422 of the bearing 42 is fixed to the cam 41, and the inner race 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 pressed by the inner ring 422 via the plurality of rolling elements 423 and elastically deformed into an elliptical shape. Thereby, 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 a state where the bearing 42 is elastically deformed, since the 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 substantially constant over the entire circumference of the outer ring 421. In this state, the plurality of rolling elements 423 roll between the outer ring 421 and the inner ring 422, and the outer ring 421 can rotate relative to the inner ring 422. Thus, when the cam 41 rotates about the rotation axis Ax1 in a state where the bearing 42 is elastically deformed, the rotation of the cam 41 is not transmitted to the outer ring 421, and the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 via the plurality of rolling elements 423. That is, in the wave generator 4, when the cam 41 rotates about the rotation axis Ax1, the outer ring 421 elastically deforms so as to rotate about the rotation axis Ax1 with the major axis of the elliptical shape traced by the outer ring 421. Therefore, the outer peripheral shape of the wave generator 4, which is an elliptical shape as viewed from the input side of the rotation axis Ax1 as a whole of the wave generator 4, changes with the rotation of the cam 41 such that the major axis thereof rotates about the rotation axis Ax1.

The wave generator 4 configured as described above is disposed inside the circular flexible externally toothed gear 3. Here, the circular flexible externally toothed gear 3 is combined with the wave generator 4 such that only the end portion of the inner peripheral surface 301 of the body portion 321 on the side opposite to the bottom portion 322 (the input side of the rotation shaft Ax 1) is fitted into the wave generator 4. At this time, the bearing 42 of the wave generator 4 is disposed between the outer peripheral surface 411 of the cam 41 and the inner peripheral surface 301 of the circular flexible externally toothed gear 3. Here, the outer diameter of the outer ring 421 in a state where the bearing 42 is not elastically deformed (a state where the cam 41 is not combined with the bearing 42) is the same as the inner diameter of the circular flexible externally toothed gear 3 (the body portion 321) in a state where elastic deformation is not generated in the same manner. Therefore, the outer peripheral surface of the outer ring 421 of the wave generator 4 is in contact with the inner peripheral surface 301 of the circular flexible externally toothed gear 3 without a gap. Thus, in a state where the circular flexible externally toothed gear 3 is elastically deformed (a state where the wave generator 4 and the circular flexible externally toothed gear 3 are combined), the body portion 321 is flexed into an elliptical shape (non-circular shape). In this state, the circular flexible externally toothed gear 3 is fixed to the outer ring 421 of the bearing 42.

The cover member 5 is disposed to face at least the bearing 42 from one side (input side) of the rotation axis Ax1. The cover member 5 faces the bearing 42 with a gap G1 (see fig. 1B) secured between the cover member and the outer ring 421 of the bearing 42, and prevents foreign matter X1 (see fig. 5A) from entering the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1. The lid member 5 is described in detail in the section "(3.3) lid member".

As shown in fig. 2A, in the harmonic gear device 1 configured as described above, the body portion 321 of the flexible externally toothed gear 3 is flexed into an elliptical shape (non-circular shape), whereby the external teeth 31 of the flexible externally toothed gear 3 are partially meshed with the internal teeth 21 of the rigid internally toothed gear 2. That is, the external teeth 31 at two locations corresponding to both ends in the longitudinal direction of the elliptical shape are engaged with the internal teeth 21 by the (body portion 321 of the) flexible externally toothed gear 3 being elastically deformed into an elliptical shape. When the cam 41 rotates about the rotation shaft Ax1, the rotation of the cam 41 is not transmitted to the outer ring 421 and the circular flexible externally toothed gear 3, and the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 and the circular flexible externally toothed gear 3 via the plurality of rolling elements 423. Therefore, the outer peripheral shape of the circular flexible externally toothed gear 3, which is viewed from the input side of the rotation axis Ax1 and has an elliptical shape, changes as the cam 41 rotates so that the major axis thereof rotates around the rotation axis Ax1.

As a result, the external teeth 31 formed on the outer peripheral surface of the circular flexible externally toothed gear 3 undulate. Since the wave 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, and the flexible external gear 3 rotates relative to the rigid internal gear 2. That is, since the external teeth 31 mesh with the internal teeth 21 at both ends in the long axis direction of the elliptical shape formed by (the body portion 321 of) the circular flexible externally toothed gear 3, the meshing position of the internal teeth 21 and the external teeth 31 is moved by the rotation of the long axis of the elliptical shape about the rotation axis Ax1. As described above, in the harmonic gear device 1 according to the present embodiment, the flexible externally toothed gear 3 is deformed in accordance with the rotation of the wave generator 4 about the rotation axis Ax1, and the flexible externally toothed gear 3 rotates in accordance with the difference in the number of teeth from the rigid internally toothed gear 2 by meshing part of the external teeth 31 with part of the internal teeth 21.

As described above, in the harmonic gear device 1, the difference in the number of teeth between the flexible externally toothed gear 3 and the rigid internally toothed gear 2 defines the reduction ratio of the output rotation 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 reduction ratio R1 is expressed by the following formula 1.

R1= V2/(V1-V2) \8230; (formula 1)

In short, the reduction gear ratio R1 is increased as the difference in the number of teeth (V1-V2) between the rigid internally toothed gear 2 and the flexible externally toothed gear 3 is decreased. For example, since the number of teeth V1 of the rigid internal gear 2 is "202", the number of teeth V2 of the circular flexible external gear 3 is "200", and the difference in the number of teeth (V1-V2) is "2", the reduction ratio R1 is "100" according to the above equation 1. In this case, when the cam 41 rotates clockwise by one rotation (360 degrees) around the rotation axis Ax1 as viewed from the input side of the rotation axis Ax1, the circular flexible externally toothed gear 3 rotates counterclockwise around the rotation axis Ax1 by the tooth count difference "2" (i.e., 3.6 degrees).

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

The harmonic gear device 1 may include at least the rigid internally toothed gear 2, the flexible externally toothed gear 3, the wave generator 4, and the cover member 5, and may further include, as a component, a spline bush 113 described in the section "(3.2) actuator", for example.

(3.2) actuators

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

As shown in fig. 4, an actuator 100 according to the present embodiment includes the harmonic gear device 1 according to 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, the wave generator 4, and the cover member 5 that constitute the harmonic gear device 1. In addition, the actuator 100 includes an input portion 103, an input-side housing 111, an output-side housing 112, a spline bush 113, a spacer 114, a first stopper 115, a second stopper 116, and a mounting plate 117, in addition to the harmonic gear device 1, the drive source 101, and the output portion 102. In the present embodiment, the actuator 100 further includes input- side bearings 118 and 119, an input-side oil seal 120, output- side bearings 121 and 122, and an output-side oil seal 123.

In the present embodiment, the actuator 100 is made of a metal such as stainless steel, cast iron, mechanical structural carbon steel, chromium molybdenum steel, phosphor bronze, or aluminum bronze, as a material of a member other than the drive source 101, the input-side oil seal 120, and the output-side oil seal 123.

The drive source 101 is a power generation source such as a motor (electric motor). The power generated by the drive source 101 is transmitted to the cam 41 of the wave generator 4 in the harmonic gear device 1. Specifically, the driving source 101 is connected to a shaft as an input unit 103, and power generated by the driving 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 disposed along the rotation axis Ax2 on the output side. The central axis of the shaft as the output unit 102 coincides with the rotation axis Ax 2. The output portion 102 is held by an output-side case 112 so as to be rotatable about a rotation axis Ax 2. The output portion 102 is fixed to the bottom portion 322 of the main body portion 32 in the circular flexible externally toothed gear 3, and rotates together with the circular flexible externally toothed gear 3 around the rotation axis Ax 2. That is, the output portion 102 takes out the rotational force of the circular flexible externally toothed gear 3 as an output.

The input portion 103 is a cylindrical shaft disposed along the input-side rotation axis Ax1. The central axis of the shaft as the input unit 103 coincides with the rotation axis Ax1. Input portion 103 is held by input-side case 111 so as to be rotatable around 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 portion 103 transmits the power (rotational force) generated by the drive source 101 to the cam 41 as an input. As described above, in the present embodiment, since the input-side rotation shaft Ax1 and the output-side rotation shaft Ax2 are positioned on the same straight line, the input unit 103 and the output unit 102 are positioned coaxially.

The input-side housing 111 holds the input portion 103 via input- side bearings 118 and 119 such that the input portion 103 can rotate. The pair of input- side bearings 118 and 119 are arranged in a row with a space therebetween along the rotation axis Ax1. In the present embodiment, a shaft as the input portion 103 passes through the input-side housing 111, and a tip end portion of the input portion 103 protrudes from an input-side end surface (right end surface in fig. 4) of the rotary shaft Ax1 in the input-side housing 111. A gap between the input portion 103 and the input-side end surface of the rotary shaft Ax1 of the input-side housing 111 is closed by the input-side oil seal 120.

The output-side housing 112 holds the output unit 102 via output- side bearings 121 and 122 so that the output unit 102 can rotate. The pair of output side bearings 121 and 122 are arranged in line with an interval therebetween along the rotation axis Ax 2. In the present embodiment, the shaft as the output portion 102 passes through the output side case 112, and the tip end portion of the output portion 102 protrudes from the output side end surface (left end surface in fig. 4) of the rotating shaft Ax1 in the output side case 112. A gap between the output-side oil seal 123 and the output portion 102 in the output-side end surface of the rotary shaft Ax1 of the output-side housing 112 is closed.

Here, as shown in fig. 4, the input-side housing 111 and the output-side housing 112 are coupled to each other in a state where the rigid internal gear 2 of the harmonic gear device 1 is sandwiched from both sides in the direction parallel to the rotational axis Ax1. Specifically, the input side housing 111 contacts the rigid internal gear 2 from the input side of the rotating shaft Ax1, and the output side housing 112 contacts the rigid internal gear 2 from the output side of the rotating shaft Ax1. In this manner, the input-side case 111 and the output-side case 112 are fastened and fixed to each other with screws (bolts) inserted through the plurality of fixing holes 22 in a state where the rigid internal gear 2 is sandwiched between the input-side case 111 and the output-side case 112. 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 together with the input-side housing 111 and the output-side housing 112 form the outer contour of the actuator 100.

The spline bushing 113 is a cylindrical member for coupling the shaft as the input portion 103 and the cam 41. The spline bushing 113 is inserted into the cam hole 43 formed in the cam 41, and a shaft as the input portion 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 with respect to both the cam 41 and the input portion 103 is restricted in the rotational direction around the rotational shaft Ax1, and the spline bush 113 is movable at least with respect to the input portion 103 in the direction parallel to the rotational shaft Ax1. This enables a spline coupling structure to be realized as a coupling 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 unit 103, and can rotate together with the input unit 103 around the rotation axis Ax1.

In the present embodiment, the spline bush 113 is coupled to the cover member 5 as well as the shaft as the input portion 103 to the cam 41. Therefore, the spline bush 113 is inserted not only into the cam hole 43 but also into the cover hole 53 formed in the cover member 5. Here, the movement of the spline bush 113 with respect to both the cover member 5 and the input portion 103 is restricted in the rotational direction around the rotational shaft Ax1, and the spline bush 113 is movable at least with respect to the input portion 103 in the direction parallel to the rotational shaft Ax1. This enables a spline coupling structure to be used as a coupling structure between the input portion 103 and the cover member 5. Thereby, the cover member 5 can move along the rotation axis Ax1 with respect to the input unit 103, and can rotate together with the input unit 103 around 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 member that prevents the spline bush 113 from coming off the cam 41 and the cover member 5. The first stopper 115 includes, for example, an E-ring, and is attached to the spline bushing 113 so as to contact the cover member 5 from the input side of the rotational shaft Ax1. The second stopper 116 is a member that prevents the input portion 103 from coming off the spline bushing 113. The second stopper 116 is formed of, for example, an E-ring, and is attached to the input portion 103 so as to contact the spline bush 113 from the output side of the rotating shaft Ax1.

The mounting plate 117 is a member for mounting the shaft as the output portion 102 to the bottom portion 322 of the circular flexible externally toothed gear 3. Specifically, the mounting plate 117 and the flange portion are fastened and fixed by screws (bolts) through the plurality of mounting holes 33 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 portion 102. Thereby, a shaft as the output portion 102 is fixed to the bottom portion 322 of the circular flexible externally toothed gear 3.

(3.3) cover Member

Next, the structure of the cover member 5 (cover body 10) of the harmonic gear device 1 according to the present embodiment will be described in more detail with reference to fig. 1A to 3B.

The cover member 5 is a plate-like member that covers the bearing 42 from one side (input side) of the rotation axis Ax1. The cover member 5 is a member having a non-circular shape (here, an elliptical shape). At least the outer peripheral surface of the cover member 5 is formed of a metal plate having an elliptical shape in plan view. The cover member 5 has a predetermined thickness in the direction of the rotation axis Ax1. However, the thickness of the cover member 5 is small (thin) compared to the thickness of the rigid internal gear 2. Thereby, the cover member 5 has higher rigidity than the circular flexible external gear 3 and lower rigidity than the rigid internal gear 2.

The cover member 5 has a base portion 51 and an umbrella portion 52. The base portion 51 is a metal plate having an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. The umbrella portion 52 is an annular portion that becomes the outer peripheral portion of the cover member 5 when viewed from one side (input side) of the rotation axis Ax1. In other words, the base 51 is located inside the umbrella 52. In the present embodiment, at least the outer peripheral shape of the umbrella portion 52 is also formed in an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. In the present embodiment, the outer peripheral shape of the umbrella portion 52 and the outer peripheral shape of the base portion 51 are similar to the outer peripheral shape of the cam 41. Further, the base portion 51 and the umbrella portion 52 are integrally formed by one metal member, whereby the seamless lid member 5 can be realized.

The cover member 5 is disposed so as to face at least the bearing 42 from the input side of the rotating shaft Ax1, so that the cover member 5 covers the bearing 42 from the input side of the rotating shaft Ax1. That is, the cover member 5 is combined with the wave generator 4 so as to coincide with the wave generator 4 from the input side of the rotation axis Ax1. In the present embodiment, the cover member 5 and the wave generator 4 are combined in a direction parallel to the rotation axis Ax1 such that most of the cover member 5 is accommodated between both surfaces of the rigid internal gear 2 in the thickness direction. As shown in fig. 1A, only a part of the cover member 5 in the thickness direction protrudes from the rigid internal gear 2 toward the input side of the rotation axis Ax1. Thereby, the cover member 5 prevents the foreign matter X1 from entering the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1. However, the cover member 5 is disposed to face the bearing 42 with a gap G1 of a certain value or more between the cover member and the outer ring 421 of the bearing 42. Therefore, the cover member 5 does not contact the outer ring 421.

In the present embodiment, the cover member 5 has a shape and a size at least as large as covering the entire wave generator 4 when viewed from one side of the rotation axis Ax1. Further, the cover member 5 has the same outer peripheral shape as the circular flexible externally toothed gear 3. Therefore, as shown in fig. 2B, the cover member 5 covers not only the bearing 42 but also the entire wave generator 4 including the cam 41 and further the circular flexible externally toothed gear 3 as viewed from the input side of the rotation shaft Ax1.

As described above, the cover member 5 has a non-circular portion corresponding to the cam 41 at a portion facing the bearing 42 when viewed from one side of the rotation axis Ax1. In the present embodiment, the entire cover member 5 including the base portion 51 and the umbrella portion 52 has a non-circular shape (here, an elliptical shape) similar to the cam 41 when viewed from one side of the rotation axis Ax1. Therefore, the cover member 5 covers the entire wave generator 4 when viewed from the input side of the rotation shaft Ax1, but is hardly exposed from the wave generator 4. Further, the wave generator 4 is not exposed from the cover member 5. In other words, as shown in fig. 2B, the cover member 5 and the wave generator 4 (the cam 41 and the bearing 42) have an elliptical shape that is similar to each other and has a long axis in the same direction when viewed from one side of the rotation axis Ax1.

As described above, in the present embodiment, the cover member 5 is coupled to the shaft as the input portion 103 via the spline bush 113. Therefore, a cover hole 53 for attaching a shaft as the input portion 103 is formed in the central portion of the base portion 51. The cover hole 53 has the same shape as the cam hole 43 of the cam 41 when viewed from one side (input side) of the rotation axis Ax1.

In the present embodiment, the cover member 5 and the cam 41 rotate at the same speed. That is, the cover member 5 rotates together with the cam 41 relative to the rigid internal gear 2. Therefore, when the cam 41 rotates clockwise by one rotation (360 degrees) around the rotation axis Ax1 as viewed from the input side of the rotation axis Ax1, the cover member 5 also rotates clockwise by one rotation (360 degrees) around the rotation axis Ax1. As described above, in the present embodiment, a spline coupling structure can be adopted as a coupling structure of the input portion 103, the cam 41, and the cover member 5, and thereby the cover member 5 and the cam 41 rotate at the same speed. Further, by the cap member 5 and the cam 41 rotating at the same speed, the cap member 5 and the wave generator 4 (the cam 41 and the bearing 42) maintain an elliptical shape that is similar to each other and has a major axis in the same direction when viewed from one side of the rotation axis Ax1.

Next, the shape of the base 51 will be described in further detail. The base portion 51 has a recessed portion 511 in an outer peripheral portion of the surface on the output side of the rotating shaft Ax1. As shown in fig. 3A, the recess 511 forms a step in the outer peripheral portion of the base 51 so as to recess the surface on the output side of the rotating shaft Ax1. The depression 511 is formed over the entire circumference of the base 51 in the circumferential direction. Here, the side surface and the bottom surface of the depression 511 are orthogonal to each other. Therefore, as shown in fig. 1B, an "inner angle" that becomes a right angle in cross section is formed in the concave portion 511.

The base 51 is combined with the wave generator 4 so that a corner of the outer ring 421 of the bearing 42 is accommodated in the recess 511. That is, as shown in fig. 1B, an inner corner portion of the end surface of the base portion 51 on the input side of the rotating shaft Ax1 in the outer ring 421 is housed in the recessed portion 511. In the present embodiment, the gap G1 between the cover member 5 and the outer ring 421 of the bearing 42 is the smallest in the recess 511. However, the cover member 5 faces the bearing 42 with a gap G1 secured between the cover member and the outer ring 421 of the bearing 42, and the cover member 5 does not contact the outer ring 421 even in the recess 511. More specifically, a gap G11 in the radial direction (the direction orthogonal to the rotation axis Ax 1) is present between the side surface of the recess portion 511 and the inner circumferential surface 424 of the outer ring 421. Further, a gap G12 in the axial direction (direction parallel to the rotation axis Ax 1) exists between the bottom surface of the recess 511 and the input-side end surface of the rotation axis Ax1 in the outer ring 421. The gap G1 between the cover member 5 and the outer ring 421 includes a gap G11 and a gap G12.

The gap G11 and the gap G12 are set to a dimension such that interference does not occur even when machining errors and assembly errors of the respective members are taken into consideration, and are set to 0.05mm to 1.0mm, for example. Both the gap G11 and the gap G12 are more preferably 0.1mm or more and 0.5mm or less.

The concave portion 511 is formed over the entire circumferential range of the base portion 51. In the present embodiment, the entire cover member 5 has an elliptical shape similar to the cam 41 when viewed from one side of the rotation axis Ax1. Therefore, the gap G1 is ensured over the entire circumferential range of the outer ring 421. That is, the gap G1 is ensured substantially uniformly in the circumferential direction of the outer ring 421.

The base portion 51 has a constricted portion 512 in a region that is inside the recessed portion 511 on the surface on the output side of the rotating shaft Ax1. As shown in fig. 3A, the constricted portion 512 is a portion in which the thickness of the base portion 51 is smaller (thinner) than the central portion of the base portion 51 by recessing the surface of the base portion 51 on the output side of the rotation axis Ax1 except the central portion. The constricted portion 512 is formed over the entire circumferential range of the base portion 51. The neck portion 512 can secure the rigidity required as the lid member 5, and can reduce the weight of the lid member 5.

Further, the base 51 has a recess 513 in an annular region around the cover hole 53 in the surface on the input side of the rotation axis Ax1. As shown in fig. 3B, the concave portion 513 is formed by recessing the surface of the base portion 51 on the input side of the rotation axis Ax1 except for the central portion, so that the thickness of the base portion 51 is smaller (thinner) than the central portion of the base portion 51. The recess 513 is formed over the entire circumference of the base 51 in the circumferential direction. By the recess 513, the cover member 5 can be reduced in weight while the required rigidity of the cover member 5 is ensured.

Next, the shape of the umbrella portion 52 will be described in further detail. As shown in fig. 1B, the umbrella portion 52 is formed so that the distance from the rotational axis Ax1 gradually increases from the bearing 42 side toward one side (input side) of the rotational axis Ax1. That is, the umbrella portion 52 has an outer peripheral surface 521, and the outer peripheral surface 521 is inclined with respect to the rotation axis Ax1 such that the distance (radius) from the rotation axis Ax1 gradually increases as the distance from the bearing 42 increases. Therefore, as shown in fig. 1B, the umbrella portion 52 has a triangular shape in cross section. Such an umbrella portion 52 is formed over the entire circumference of the cover member 5 in the circumferential direction.

The lid member 5 is configured to secure a predetermined gap with the outer ring 421 of the bearing 42, and further with the circular flexible externally toothed gear 3 and the rigid internally toothed gear 2 even in the umbrella portion 52. Of the outer ring 421, the flexible externally toothed gear 3, and the rigid internally toothed gear 2, the guide portion 23 provided in the rigid internally toothed gear 2 is the narrowest gap with the umbrella portion 52. The guide portion 23 faces the umbrella portion 52 at a predetermined interval or more. As shown in fig. 1B, the guide portion 23 is a portion that protrudes from the end surface of the internal teeth 21 of the rigid internal gear 2 on the input side of the rotating shaft Ax1 toward the input side of the rotating shaft Ax1.

The guide portion 23 has an inclined surface 231, and the inclined surface 231 is inclined with respect to the rotation axis Ax1 such that a distance (radius) from the rotation axis Ax1 gradually increases toward one side (input side) of the rotation axis Ax1. The inclined surface 231 of the guide portion 23 is parallel to the outer peripheral surface 521 of the umbrella portion 52. This makes it possible to narrow the gap between the umbrella portion 52 and the rigid internal gear 2 in the guide portion 23 and to secure a gap equal to or larger than a certain value with respect to the rigid internal gear 2. The gap (interval) between the umbrella part 52 and the guide part 23 is set to a dimension that does not interfere with each other in consideration of machining errors and assembly errors of the respective members, and is set to 0.05mm to 1.0mm, for example. The gap (interval) between the umbrella part 52 and the guide part 23 is more preferably 0.1mm to 0.5 mm. In the present embodiment, the guide portion 23 and the rigid internal gear 2 are integrally formed by one metal member.

However, in the present embodiment, the cover member 5 is configured not to allow the liquid to pass therethrough (i.e., to block the liquid). In other words, the liquid is shielded by the cover member 5 without passing through the cover member 5. The term "liquid" in the embodiments of the present disclosure means a substance containing a liquid state or a gel state. The "gel state" as used herein refers to a state having an intermediate property between a liquid and a solid, and includes a colloid (colloid) composed of two phases of a liquid phase and a solid phase. For example, a state called gel (gel) or sol (sol) such as an emulsion (emulsion) in which the dispersion medium is a liquid phase, a dispersion in which the dispersoid is a liquid phase, or a suspension (suspension) in which the dispersoid is a solid phase is included in the "gel state". The state where the dispersion medium is a solid phase and the dispersoid is a liquid phase is also included in the "gel state". That is, the liquid shielded by the cover member 5 has a constant volume when the temperature and the pressure are constant, and is an object having a property of being a fluid not having a predetermined shape. In other words, the liquid shielded by the cover member 5 is a fluid (fluid) other than gas. As used herein, "fluid" includes both Newtonian and non-Newtonian fluids.

In the harmonic gear device 1, for example, a liquid or gel lubricant 54 (see fig. 5A) is injected between the meshing portion of the internal teeth 21 and the external teeth 31 and the outer ring 421 and the inner ring 422 of the bearing 42. Since the lubricant 54 is liquid, the lid member 5 shields at least the lubricant 54. Therefore, the lubricant 54 is difficult to wet the cover member 5.

In the present embodiment, the cover member 5 has oil repellency. The cover member 5 may have oil repellency as a whole, but may have oil repellency at least in a part thereof. In the present embodiment, a fluoride-based oil-repellent coating, for example, is locally applied to the cover member 5, and the oil-repellent coated portion of the cover member 5 is rendered oil-repellent. Specifically, the outer peripheral surface 521 of the umbrella portion 52 in the lid member 5 has oil repellency. For example, when a lubricant (oil) as the lubricant 54 is attached to a portion of the cover member 5 having oil repellency, the static contact angle of the cover member 5 with respect to a droplet of the lubricant 54, that is, the oil contact angle of the cover member 5, is preferably 25 degrees or more. The "contact angle against oil" referred to herein is a contact angle against oil, that is, an angle formed by oil droplets including lubricant 54 (lubricating oil) and a solid surface (a surface of a portion of cover member 5 having oil repellency) when the oil droplets adhere to the solid surface.

(4) Function of

Next, an operation of the harmonic gear device 1 according to the present embodiment will be described with reference to fig. 5A and 5B.

Fig. 5A and 5B are enlarged views of the periphery of the umbrella portion 52 of the cover member 5 in fig. 1B. In fig. 5A and 5B, in order to explain the function of the cover member 5, the foreign matter X1 entering the inner side of the outer ring 421 is blocked by the cover member 5, but the foreign matter X1 is not included in the components of the harmonic gear device 1. In fig. 5A and 5B, the lubricant 54 held between the outer ring 421 and the cover member 5 is illustrated, but the shape and amount of the lubricant 54 are not intended to be the same as illustrated.

Although the lubricant 54 held between the outer ring 421 and the cover member 5 is illustrated in fig. 5A and 5B, the shape and the amount of the lubricant 54 are not intended to be limited to the illustrated form. Thereby, the cover member 5 blocks the foreign matter X1 from entering the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1. Therefore, even if foreign matter X1 such as metal powder or nitride is generated due to abrasion or the like generated between the internal teeth 21 and the external teeth 31, the foreign matter X1 is hard to enter the inside of the outer ring 421 (between the outer ring 421 and the inner ring 422).

In particular, in the harmonic gear device 1, the power transmission due to the engagement of the internal teeth 21 and the external teeth 31 is accompanied by sliding in both the tooth profile direction and the tooth trace direction, and therefore, the foreign matter X1 due to wear is likely to be generated. Further, although the lubricant 54 is used, the flow speed of the lubricant 54 is relatively low in the rotational speed region used in the harmonic gear device 1, and the effect of flushing the generated foreign matter X1 by the lubricant 54 is difficult to expect. If such foreign matter X1 enters the bearing 42, it may damage the surface of any one of the outer ring 421, the inner ring 422, and the rolling elements 423 of the bearing 42, thereby affecting the reliability of the harmonic gear device 1. That is, when the foreign matter X1 enters between the outer ring 421 and the inner ring 422 of the bearing 42, biting of the foreign matter X1 by the rolling body 423 occurs, and damage may occur to the surface of any one of the outer ring 421, the inner ring 422, and the rolling body 423. In the harmonic gear device 1 according to the present embodiment, the cover member 5 prevents the foreign matter X1 from entering the bearing 42, and therefore, reliability is not reduced.

For example, if the inner peripheral surface (rolling surface) of the outer ring 421 is peeled off by the biting of the foreign matter X1, the function as the bearing 42 may be impaired, which may cause a malfunction in the operation as the harmonic gear device 1. In the harmonic gear device 1 according to the present embodiment, the cover member 5 can overwhelmingly reduce the biting of the foreign matter X1 into the bearing 42, which leads to improvement in the reliability of the harmonic gear device 1. In particular, the harmonic gear device 1 does not deteriorate in reliability even when used for a long period of time, and has a longer life and higher performance.

The cover member 5 is kept at a gap G1 of at least a certain value with the outer ring 421 of the bearing 42 without contacting the outer ring 421. Therefore, even if relative movement occurs between the cover member 5 and the outer ring 421 of the bearing 42 during driving of the harmonic gear device 1, frictional resistance, wear of the cover member 5 or the outer ring 421, and the like are less likely to occur between the cover member 5 and the outer ring 421. That is, in the present embodiment, since the cover member 5 rotates together with the cam 41 and the outer ring 421 rotates together with the circular flexible externally toothed gear 3, relative rotation corresponding to the difference in the rotation speed (reduction ratio) between the cam 41 and the circular flexible externally toothed gear 3 occurs between the cover member 5 and the outer ring 421. At this time, by securing the gap G1 between the cover member 5 and the outer ring 421, frictional resistance, wear of the cover member 5 or the outer ring 421, and the like are less likely to occur, and a malfunction of the operation of the harmonic gear device 1 due to the provision of the cover member 5 is less likely to occur.

The relative rotational speed between the cover member 5 and the outer ring 421 depends on the difference in rotational speed (reduction gear ratio) between the cam 41 and the circular flexible externally toothed gear 3, but if the reduction gear ratio is high, the relative rotational speed between the cover member 5 and the outer ring 421 also becomes large. As a result, if frictional resistance occurs between the cover member 5 and the outer ring 421, the power transmission efficiency of the harmonic gear device 1 is significantly reduced, and the starting performance may be affected even in a harsh environment such as a cold region. In the harmonic gear device 1 according to the present embodiment, the gap G1 between the cover member 5 and the outer ring 421 makes it difficult for such a problem due to the frictional resistance to occur, and the reliability of the harmonic gear device 1 is greatly improved.

However, as described above, in the harmonic gear device 1 according to the present embodiment, the liquid or gel lubricant 54 is injected into, for example, the meshing portion between the internal teeth 21 and the external teeth 31 and the space between the outer ring 421 and the inner ring 422 of the bearing 42. For example, the lubricant 54 is a liquid lubricating oil (oil). Then, as shown in fig. 5A and 5B, at the time of use of the harmonic gear device 1, the lubricant 54 penetrates deeply between the outer ring 421 of the bearing 42 and the cover member 5. Specifically, the lubricant 54 is mixed into at least a part of the gap G1 (see fig. 1B) between the outer ring 421 and the cover member 5, and seals at least a part of the gap G1. In short, in the present embodiment, the lubricant 54 is filled in at least a part of the gap G1 between the outer ring 421 and the cover member 5.

In the example of fig. 5A and 5B, the lubricant 54 is filled in the entire gap G1 so as to fill up both the gap G11 in the radial direction and the gap G12 in the axial direction between the outer ring 421 and the cover member 5. Further, in the present embodiment, the lubricant 54 is filled in the entire gap G1 formed over the entire circumferential length of the outer ring 421. The cover member 5 can connect a space on the input side (right side in fig. 5A) of the rotating shaft Ax1 and a space on the output side (left side in fig. 5A) of the rotating shaft Ax1 through a gap G1. In this way, the gap G1 forming the narrow path connecting the inside and the outside of the cover member 5 is filled with the lubricant 54. Therefore, the space on the input side of the rotating shaft Ax1 and the space on the output side of the rotating shaft Ax1 are shielded by the lubricant 54. Therefore, the foreign matter X1 can be more reliably prevented from entering the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1.

Here, the lubricant 54 is held in the gap G1 between the outer ring 421 and the cover member 5 by capillary action. That is, the gap G1 between the outer ring 421 and the cover member 5 is relatively narrow, and the lubricant 54 is held in the gap G1 by a capillary phenomenon in a state where the gap G1 is filled with the lubricant 54. Therefore, the state in which the gap G1 is filled with the lubricant 54 can be maintained. The magnitude of the holding force by the capillary phenomenon also varies depending on the "wettability" between the outer ring 421 and the lid member 5 and the lubricant 54. Therefore, at least a portion of the cover member 5 facing the gap G1, that is, a side surface of the recess 511 and a bottom surface of the recess 511, preferably do not have oil repellency.

In the harmonic gear device 1 according to the present embodiment, since the cover member 5 includes the umbrella portion 52, a function of throwing away the foreign matter X1 outward by a centrifugal force can also be expected. That is, the umbrella portion 52 is formed so that the distance from the rotating shaft Ax1 gradually increases from the bearing 42 side toward the input side of the rotating shaft Ax1. Therefore, even if a foreign substance X1 such as metal powder or nitride is generated due to wear or the like occurring between the internal teeth 21 and the external teeth 31 and the foreign substance X1 adheres to the outer peripheral surface 521 of the umbrella portion 52, the foreign substance X1 can be thrown outward (the input side of the rotation axis Ax 1).

That is, as the cover member 5 rotates, a centrifugal force in a direction away from the rotation axis Ax1 acts on the foreign matter X1 adhering to the outer peripheral surface 521 of the umbrella portion 52. As a result, as shown in fig. 5A, the foreign matter X1 adhering to the outer peripheral surface 521 of the umbrella portion 52 moves along the outer peripheral surface 521 toward the input side of the rotation axis Ax1, which is the direction away from the rotation axis Ax1. As a result, the foreign matter X1 moves in a direction away from the bearing 42, and finally, as shown in fig. 5B, the foreign matter X1 is discharged to the input side closer to the rotation axis Ax1 than the cover member 5. At this time, the foreign matter X1 passes through between the outer peripheral surface 521 of the umbrella portion 52 and the inclined surface 231 of the guide portion 23 and is discharged. In other words, the gap between the umbrella part 52 and the guide part 23 constitutes a discharge path for the foreign matter X1. With the function of the umbrella portion 52, the generated foreign matter X1 can be thrown outward of the lid member 5, and therefore the foreign matter X1 is less likely to accumulate inside the lid member 5.

As described above, the lid member 5 has oil repellency on the outer peripheral surface 521 of the umbrella portion 52. Therefore, in particular, the foreign matter X1 having oil components carried thereon by the lubricant 54 or the like is less likely to stay on the umbrella portion 52 and is likely to be thrown outward of the lid member 5.

(5) Application example

Next, an application example of the harmonic gear device 1 and the actuator 100 according to the present embodiment will be described with reference to fig. 6.

Fig. 6 is a cross-sectional view showing an example of a robot 9 to which the harmonic gear device 1 according to the present embodiment is applied. The Robot 9 is a so-called SCARA (Selective Compliance Assembly Robot Arm) type Robot, which is a horizontal articulated Robot.

As shown in fig. 6, the robot 9 includes two harmonic gear devices 1 and a link 91. The two harmonic gear devices 1 are respectively provided at joint portions of two portions of the robot 9. The link 91 connects the joint portions of the two portions. In the example of fig. 6, the harmonic gear device 1 is not a cup type but is constituted by a top hat type harmonic gear device. That is, in the harmonic gear device 1 illustrated in fig. 6, the circular flexible externally toothed gear 3 formed in a top hat shape is used. In fig. 6, illustration of the cover member 5 is omitted.

(6) Modification example

The implementation manner is merely one of various implementation manners of the embodiments of the present disclosure. If the object of the present invention can be achieved, the embodiment can be variously modified according to design or the like. In addition, the drawings referred to in the embodiments of the present disclosure are schematic drawings, and the ratio of the size and thickness of each component in the drawings is not necessarily limited to reflect the actual dimensional ratio. Modifications of the first embodiment will be described below. The modifications described below can be applied in appropriate combinations.

The harmonic gear device 1 is not limited to the cup type described in the first embodiment, and may be a silk hat type, a ring type, a differential type, a flat type (pancake type), a shield type, or the like.

The cover member 5 may be disposed so as to face the bearing 42 from one side of the rotational axis Ax1, and need not be disposed on the input side of the rotational axis Ax1 with respect to the bearing 42 as in the first embodiment. That is, the cover member 5 may be disposed so as to face the bearing 42 from the output side of the rotation axis Ax1. In such a case, the cover member 5 prevents the foreign matter X1 from entering the outer ring 421 from the output side of the rotation shaft Ax1.

Further, the cover member 5 may be disposed so as to face the bearing 42 from one side of the rotation axis Ax1, and the pair of cover members 5 may be disposed on the input side and the output side of the rotation axis Ax1 with respect to the bearing 42. In such a case, the cover member 5 blocks entry of the foreign matter X1 from the input side and the output side of the rotation shaft Ax1 to the inside of the outer ring 421, respectively.

The structure of the actuator 100 is not limited to the structure described in the first embodiment, and may be appropriately changed. For example, the coupling structure of the input portion 103, the cam 41, and the cover member 5 is not limited to the spline coupling structure, and an oldham coupling or the like may be used. By using the oldham coupling as the coupling structure of the input portion 103, the cam 41, and the cover member 5, it is possible to cancel the eccentricity between the rotary shaft Ax1 on the input side and the wave generator 4 (cam 41), and further, it is possible to cancel the eccentricity between the rigid internal gear 2 and the flexible external gear 3. Further, the cam 41 and the cover member 5 may not move along the rotation axis Ax1 with respect to the input portion 103.

The application examples of the harmonic gear device 1 and the actuator 100 according to the present embodiment are not limited to the horizontal articulated robot described above, and may be, for example, an industrial robot other than the horizontal articulated robot, a robot other than an industrial robot, or the like. As an example, industrial robots other than the horizontal articulated robot include a vertical articulated robot, a parallel link robot, and the like. As examples of robots other than industrial robots, there are home robots, nursing-care robots, medical robots, and the like.

The bearing 42 is not limited to a deep groove ball bearing, and may be, for example, an angular contact thrust ball bearing. Further, the bearing 42 is not limited to a ball bearing, and may be a roller bearing such as a cylindrical roller bearing, a needle roller bearing, or a tapered roller bearing in which the rolling elements 423 are formed of "rollers" other than ball-shaped.

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

The cover member 5 and the cam 41 do not necessarily rotate at the same speed as each other, and the cover member 5 may not rotate relative to the rigid internal gear 2, for example.

The guide portion 23 may be provided on the rigid internal gear 2, and it is not essential for the harmonic gear device 1 to be formed integrally with the rigid internal gear 2 using one metal member. For example, the guide portion 23, which is a member different from the rigid internal gear 2, may be fixed to the rigid internal gear 2 by bonding or the like, and may be provided in the rigid internal gear 2. Further, a plate material may be fixed to the inner peripheral surface of the input side housing 111 to which the rigid internal gear 2 is fixed, and the plate material may function as the guide portion 23.

The lubricant 54 is not limited to a liquid material such as a lubricating oil (oil), and may be a gel material such as a grease.

(second embodiment)

As shown in fig. 7A and 7B, a harmonic gear device 1A according to the present embodiment is different from the harmonic gear device 1 according to the first embodiment in the configuration of a cover member 5A. Hereinafter, the same configurations as those of the first embodiment will be given common reference numerals and their description will be omitted.

Fig. 7A is a sectional view showing a schematic configuration of the harmonic gear device 1A, and fig. 7B is an enlarged view of a main portion of fig. 7A (corresponding to a range of a region Z1 of fig. 1A).

In the present embodiment, the harmonic gear device 1A has a pair of cover members 5A. One of the pair of cover members 5A faces the bearing 42 from the input side of the rotational shaft Ax1, and the other cover member 5A faces the bearing 42 from the output side of the rotational shaft Ax1. In other words, the harmonic gear device 1A includes a pair of cover members 5A, and the pair of cover members 5A are disposed on the input side and the output side of the rotation shaft Ax1 with respect to the bearing 42, respectively.

With this configuration, the bearing 42 is sandwiched between the pair of cover members 5A in the direction parallel to the rotation axis Ax1. Therefore, the pair of cover members 5A prevent foreign matter X1 from entering the outer ring 421 from both sides of the rotation shaft Ax1.

The shape of each cover member 5A is also different from the cover member 5 in the first embodiment. In the present embodiment, since the pair of lid members 5A have a symmetrical shape in a direction parallel to the rotation axis Ax1, a shape of one of the pair of lid members 5A will be described below.

That is, in the present embodiment, as shown in fig. 7B, the cover member 5A has a base portion 51 and a convex portion 55. The base portion 51 is a metal plate having an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. At least the outer peripheral shape of the convex portion 55 is also formed in an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. In the present embodiment, the outer peripheral shape of the projection 55 and the outer peripheral shape of the base 51 are similar to the outer peripheral shape of the cam 41. Further, the base portion 51 and the projection portion 55 are integrally formed by one metal member, whereby the seamless lid member 5A can be realized.

The base portion 51 is disposed inside the circular flexible external gear 3. A first gap G21 is formed between the outer peripheral surface 514 of the base portion 51 and the inner peripheral surface 301 of the circular flexible externally toothed gear 3, and the outer peripheral surface 514 of the base portion 51 and the inner peripheral surface 301 of the circular flexible externally toothed gear 3 face each other in a direction orthogonal to the rotation axis Ax1. That is, the outer peripheral shape of the base portion 51 is an elliptical shape slightly smaller than the inner peripheral surface 301 of the circular flexible externally toothed gear 3 when viewed from one side (input side) of the rotation axis Ax1. Therefore, the outer peripheral surface 514 of the base portion 51 disposed inside the circular flexible external gear 3 faces the circular flexible external gear 3 without contacting the circular flexible external gear 3 while maintaining the first gap G21 with the inner peripheral surface 301 of the circular flexible external gear 3. More specifically, a first gap G21 in the radial direction (the direction orthogonal to the rotation axis Ax 1) exists between the outer peripheral surface 514 of the base portion 51 and the inner peripheral surface 301 of the circular flexible external gear 3.

The projection 55 projects from the base 51 and is inserted inside the outer ring 421. A second gap G22 is formed between the outer peripheral surface 551 of the projection 55 and the inner peripheral surface 424 of the outer ring 421, and the outer peripheral surface 551 of the projection 55 and the inner peripheral surface 424 of the outer ring 421 face each other in the direction orthogonal to the rotation axis Ax1. That is, the outer circumferential shape of the convex portion 55 is slightly smaller than the inner circumferential surface 424 of the outer ring 421 in an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. Therefore, the outer peripheral surface 551 of the projection 55 disposed inside the outer ring 421 faces the outer ring 421 without contacting the outer ring 421 while maintaining the second gap G22 with the inner peripheral surface 424 of the outer ring 421. More specifically, a second gap G22 in the radial direction (the direction orthogonal to the rotation axis Ax 1) is present between the outer peripheral surface 551 of the projection 55 and the inner peripheral surface 424 of the outer ring 421.

Further, a third gap G23 is formed between the base portion 51 and the outer ring 421, and the base portion 51 and the outer ring 421 oppose each other in the direction of the rotation axis Ax1. The first gap G21 and the second gap G22 are connected by a third gap G23. That is, the base portion 51 faces the outer ring 421 with the third gap G23 secured between the base portion and the end surface of the outer ring 421 in the direction of the rotation axis Ax1, and does not contact the outer ring 421. More specifically, a third gap G23 in the axial direction (the direction parallel to the rotation axis Ax 1) exists between the base 51 and the outer ring 421. As shown in fig. 7B, the first gap G21 and the second gap G22 in the radial direction are connected by a third gap G23. The gap G2 between the cover member 5A and the outer ring 421 and the circular flexible externally toothed gear 3 includes these first gap G21, second gap G22, and third gap G23.

The first gap G21, the second gap G22, and the third gap G23 are set to have a dimension such that interference does not occur even when machining errors and assembly errors of the respective members are taken into consideration, and are set to be 0.05mm or more and 1.0mm or less, for example. The first gap G21, the second gap G22, and the third gap G23 are each more preferably 0.1mm or more and 0.5mm or less.

That is, a crank-shaped gap G2 in cross section is formed between the cover member 5A and the outer ring 421 and the flexible externally toothed gear 3 by the first gap G21, the second gap G22, and the third gap G23. The cover member 5A has a space on the input side (right side in fig. 7A) of the rotation axis Ax1 and a space on the output side (left side in fig. 7A) of the rotation axis Ax1 connected by a gap G2. In this way, the labyrinth structure formed by the gap G2 forming the narrow path connecting the inside and the outside of the lid member 5A is adopted, thereby improving the sealing performance by the lid member 5A. This can more reliably prevent the foreign matter X1 from entering the inner side of the outer ring 421 from one side (input side or output side) of the rotating shaft Ax1. In particular, the third gap G23 in the axial direction is maintained at a constant minimum gap regardless of the elastic deformation of the outer ring 421 and the circular flexible externally toothed gear 3, and thus the foreign matter X1 is easily prevented from passing through the gap G2. The first gap G21 and the second gap G22 in the radial direction can maintain a constant minimum gap regardless of the elastic deformation of the outer ring 421 and the circular flexible externally toothed gear 3, and the foreign matter X1 can be prevented from passing through the gap G2.

Further, in the present embodiment, the lid member 5A has a constricted portion 515 in a region around the lid hole 53 (see fig. 10A). As shown in fig. 7, the constricted portion 515 is a portion in which both surfaces in the thickness direction (direction parallel to the rotation axis Ax 1) are recessed so that the thickness of the lid member 5A is smaller (thinner) than the central portion of the lid member 5A. The constricted portion 515 is formed over the entire circumference of the circumferential direction of the cover member 5A. The neck portion 515 can ensure the rigidity required for the lid member 5A, but can reduce the weight of the lid member 5A.

In the present embodiment, it is also preferable that the gap G2 is filled with the lubricant 54.

Fig. 8A is a cross-sectional view showing a schematic configuration of a harmonic gear device 1B according to a first modification of the second embodiment, and fig. 8B is an enlarged view of a main portion of fig. 8A (corresponding to a range of a region Z1 of fig. 1A). In a harmonic gear device 1B according to a first modification of the second embodiment, the cover member 5 described in embodiment 1 is used instead of one cover member 5A of the pair of cover members 5A described in embodiment two, which faces the bearing 42 from the input side of the rotation shaft Ax1. In this configuration, since the foreign matter X1 generated in the one cover member 5 facing the bearing 42 from the input side of the rotation axis Ax1 can be thrown outward of the cover member 5 by the function of the umbrella portion 52, the foreign matter X1 is less likely to accumulate inside the cover member 5.

Fig. 9A is a cross-sectional view showing a schematic structure of a harmonic gear device 1C according to a second modification of the second embodiment, and fig. 9B is an enlarged view of a main portion of fig. 9A (corresponding to a range of a region Z1 of fig. 1A). In the harmonic gear device 1C according to the second modification of the second embodiment, the cover member 5C having a different shape is used instead of the one cover member 5A facing the bearing 42 from the input side of the rotation shaft Ax1 of the pair of cover members 5A described in the second embodiment. The lid member 5C has an umbrella portion 52 in addition to the base portion 51 and the projection 55 which are the same as those of the lid member 5A.

As shown in fig. 9B, the umbrella portion 52 of the cover member 5C protrudes from the surface on the opposite side of the bearing 42 in the thickness direction of the base portion 51. The umbrella portion 52 is formed so that the distance from the rotation axis Ax1 gradually increases from the bearing 42 side toward one side (input side) of the rotation axis Ax1. That is, the umbrella portion 52 has an outer peripheral surface 521, and the outer peripheral surface 521 is inclined with respect to the rotation axis Ax1 such that the distance (radius) from the rotation axis Ax1 gradually increases as the distance from the bearing 42 increases. Such an umbrella portion 52 is formed over the entire circumference of the cover member 5 in the circumferential direction. In this configuration, since the foreign matter X1 generated in the cover member 5C facing the bearing 42 from the input side of the rotation shaft Ax1 can be thrown outward of the cover member 5C by the function of the umbrella portion 52, the foreign matter X1 is less likely to accumulate inside the cover member 5C.

Fig. 10A, 10B, and 10C are sectional views of main portions showing schematic configurations of harmonic gear devices 1d,1e, and 1f according to third, fourth, and fifth modifications of the second embodiment, respectively.

As shown in fig. 10A, in a harmonic gear device 1D according to a third modification of the second embodiment, the shape of a cover member 5D is different from the cover member 5A described in the second embodiment. In the cover member 5D, a groove portion 56 is provided in place of the projection portion 55 at a portion of the surface of the base portion 51 facing the outer ring 421. The groove 56 is formed over the entire circumferential length of the base 51. Further, the outer ring 421 has a rib 425 protruding from an end surface in the direction of the rotation axis Ax1. The rib 425 is formed on the entire circumferential circumference of the outer ring 421. The ribs 425 are inserted into the groove portions 56. Here, a gap G3 is ensured between the cover member 5D and the outer ring 421 including between the rib 425 and the groove portion 56. Since the rib 425 and the groove portion 56 form a labyrinth structure in the gap G3, which is similar to the gap G2, the sealing performance of the lid member 5D is improved.

As shown in fig. 10B, in a harmonic gear device 1E according to a fourth modification of the second embodiment, the shape of a cover member 5E is different from the cover member 5A described in the second embodiment. In the cover member 5E, the base portion 51 itself is disposed inside the outer ring 421. That is, the outer peripheral shape of the base portion 51 is slightly smaller than the inner peripheral surface 424 of the outer ring 421 in an elliptical shape when viewed from one side (input side) of the rotation axis Ax1. Here, the cover member 5E has a rib 57 protruding from the outer peripheral surface 514 of the base portion 51. The rib 57 is formed over the entire circumferential circumference of the base portion 51. Further, the outer ring 421 has a groove 426 on the inner peripheral surface. The groove 426 is formed over the entire circumferential length of the outer ring 421. The rib 57 is inserted into the groove 426. Here, a gap G4 is ensured between the cover member 5E and the outer ring 421 including between the rib 57 and the groove 426. The gap G4 has a labyrinth structure formed by the rib 57 and the groove portion 426, which is incorporated in the same manner as the gap G2, and therefore, the sealing performance of the lid member 5E is improved. Further, the gap G4 is filled with the lubricant 54.

As shown in fig. 10C, in a harmonic gear device 1F according to a fifth modification of the second embodiment, a shape of a cover member 5F is different from that of a cover member 5E according to a fourth modification of the second embodiment. The lid member 5F has a rib 58 protruding from the outer peripheral surface 514 of the base 51. The outer peripheral shape of the rib 58 is slightly smaller than the inner diameter of the outer ring 421 in the width direction. The rib 58 is formed on the entire circumferential circumference of the base 51. Further, the outer ring 421 has a groove 427 on the inner peripheral surface. The groove 427 is formed over the entire circumferential length of the outer race 421. The inner diameter of the outer ring 421 holds the groove 427 and is different between the inner side and the outer side, and the outer side of the groove 427 is larger. The rib 58 opposes the groove 427. Here, a gap G5 is ensured between the cover member 5F and the outer ring 421 including between the rib 58 and the groove portion 427. Since the gap G5 has a labyrinth structure formed by the rib 58 and the groove portion 427 in the same manner as the gap G2, the sealing performance by the lid member 5F is improved. Further, the gap G5 is filled with the lubricant 54.

Note that, the pair of the various cover members 5A to 5F described in the second embodiment need not be provided, and only one cover member may be provided so as to face the bearing 42 from one side of the rotation axis Ax1.

The configuration (including the modification) of the second embodiment can be applied in appropriate combination with the configuration (including the modification) described in the first embodiment.

(third embodiment)

As shown in fig. 11A and 11B, the harmonic gear device 1G according to the present embodiment differs from the harmonic gear device 1A according to the second embodiment in the configuration of the cover member 5G. Hereinafter, the same configurations as those in the second embodiment are given the same reference numerals, and the description thereof will be omitted.

Fig. 11A is a sectional view showing a schematic configuration of the harmonic gear device 1G, and fig. 11B is an enlarged view of a main portion of fig. 11A (corresponding to a range of the region Z1 of fig. 1A).

In the present embodiment, since the pair of lid members 5G have a symmetrical structure in a direction parallel to the rotation axis Ax1, a shape of one of the pair of lid members 5G will be described below.

That is, in the present embodiment, the cover member 5G faces only the bearing 42 in the wave generator 4 from one side of the rotation axis Ax1. That is, the cover member 5G is a ring-shaped member formed in the same manner as the bearing 42. The cover member 5G is fixed to the inner race 422 of the bearing 42.

Specifically, the cover member 5G has a main plate 501, a first side plate 502, and a second side plate 503. The main plate 501 is a plate-shaped member formed in an annular shape when viewed from one side of the rotation axis Ax1. The first side plate 502 protrudes from the inner peripheral edge of the main plate 501 toward the bearing 42 side along the rotation axis Ax1. The second side plate 503 protrudes from the outer peripheral edge of the main plate 501 toward the bearing 42 along the rotation axis Ax1. In other words, the first side plate 502 and the second side plate 503 are opposed to each other in the radial direction and are joined by the main plate 501. The main plate 501, the first side plate 502, and the second side plate 503 are integrally formed by one metal component, whereby the seamless lid member 5G can be realized.

The cover member 5G possesses flexibility because its thickness is relatively small (thin). Therefore, in a state where the lid member 5G is fixed to the inner ring 422, if the inner ring 422 is elastically deformed, the lid member 5G is elastically deformed in accordance with the deformation of the inner ring 422.

Here, the main plate 501 faces the bearing 42 with a gap from one side of the rotation axis Ax1 to the end surface of the bearing 42. The first side plate 502 is press-fitted into a gap between the inner race 422 and the cam 41, and the lid member 5G is fixed to the inner race 422 via the first side plate 502. On the other hand, the second side plate 503 is inserted into the gap between the outer ring 421 and the circular flexible externally toothed gear 3, but a gap G6 is secured between the outer ring 421 and the circular flexible externally toothed gear 3 in the second side plate 503.

According to the above configuration, the cover member 5G faces the bearing 42 with a gap G6 secured between the cover member and the outer ring 421 of the bearing 42. The cover member 5G also has a function of preventing foreign matter X1 from entering the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1.

Note that the pair of cover members 5G described in the third embodiment need not be provided, and only one cover member may be provided so as to face the bearing 42 from one side of the rotation axis Ax1.

The configuration (including the modification) of the third embodiment can be applied in appropriate combination with the configuration (including the modification) described in the first embodiment or the second embodiment.

(conclusion)

As described above, the harmonic gear device (1, 1A to 1G) according to the first aspect includes: an annular rigid internal gear (2) having internal teeth (21); an annular circular flexible externally toothed gear (3) having external teeth (31) and disposed inside the rigid internally toothed gear (2); and a wave generator (4). The wave generator (4) is disposed inside the circular flexible external gear (3), and bends the circular flexible external gear (3). The harmonic gear devices (1, 1A-1G) deform the flexible externally toothed gear (3) with the rotation of the wave generator (4) about the rotation axis (Ax 1), mesh part of the external teeth (31) with part of the internal teeth (21), and rotate the flexible externally toothed gear (3) relative to the rigid internally toothed gear (2) in accordance with the difference in the number of teeth with the rigid internally toothed gear (2). The wave generator (4) comprises: a non-circular cam (41) that is rotationally driven around a rotation axis (Ax 1); and a bearing (42) disposed between the outer peripheral surface (411) of the cam (41) and the inner peripheral surface (301) of the circular flexible externally toothed gear (3). The harmonic gear device (1, 1A-1G) further comprises a cover member (5, 5A-5G), and the cover member (5, 5A-5G) is arranged to face the bearing (42) from one side of the rotating shaft (Ax 1). The cover members (5, 5A-5G) face the bearing (42) with gaps (G1-G6) secured between the cover members and the outer ring (421) of the bearing (42), and prevent foreign matter (X1) from entering the inner side of the outer ring (421) from one side of the rotating shaft (Ax 1).

According to this aspect, even if foreign matter (X1) is generated due to wear or the like that occurs between the internal teeth (21) and the external teeth (31) as a result of long-term use of the harmonic gear devices (1, 1A-1G), it is possible to suppress entry of such foreign matter (X1) into the bearing (42). Therefore, the method has the advantage of high reliability.

According to a first aspect, in a harmonic gear device (1, 1A to 1G) relating to a second aspect, a cover member (5, 5A to 5G) and a cam (41) rotate at a constant speed.

According to this aspect, even if the bearing (42) elastically deforms, the cover member (5, 5A-5G) can follow the elastic deformation of the bearing (42).

According to a second aspect, in the harmonic gear devices (1, 1A to 1G) according to the third aspect, the cover members (5, 5A to 5G) have the umbrella portions (52), and the umbrella portions (52) are formed such that the distance from the rotation axis (Ax 1) gradually increases from the bearing (42) side toward one side of the rotation axis (Ax 1).

According to this aspect, foreign matter (X1) adhering to the umbrella part (52) can be moved in a direction away from the bearing (42) by centrifugal force.

According to a third aspect, the harmonic gear device (1, 1A to 1G) according to the fourth aspect further includes a guide portion (23), and the guide portion (23) is provided on the rigid internal gear (2) and faces the umbrella portion (52) with a gap equal to or larger than a predetermined value.

According to this aspect, the movement of the foreign matter (X1) adhering to the umbrella part (52) can be guided by centrifugal force.

According to one aspect of the first to fourth aspects, in the harmonic gear device (1, 1A to 1G) relating to the fifth aspect, the cover member (5, 5A to 5G) has a non-circular portion corresponding to the cam (41) when viewed from one side of the rotating shaft (Ax 1) at a portion facing the bearing (42).

According to this embodiment, the amount of exposure of the cover members (5, 5A-5G) from the wave generator (4) can be kept relatively small.

According to any one of the first to fifth aspects, in the harmonic gear device (1, 1A to 1G) according to the sixth aspect, the lubricant (54) is filled in at least a portion of the gaps (G1 to G6) between the outer ring (421) and the cover members (5, 5A to 5G).

According to this mode, sealing with the lubricant (54) can be achieved.

According to a sixth aspect, in the harmonic gear devices (1, 1A to 1G) relating to the seventh aspect, the lubricant (54) is held in the gaps (G1 to G6) between the outer ring (421) and the cover members (5, 5A to 5G) by capillary phenomenon.

According to this manner, a member for holding the lubricant (54) is not required.

According to one aspect of the first to seventh aspects, in the harmonic gear device (1, 1A to 1G) relating to the eighth aspect, the cover member (5, 5A to 5G) has a base portion (51), and the base portion (51) is disposed inside the circular flexible externally toothed gear (3). A first gap (G21) is formed between the outer peripheral surface (514) of the base (51) and the inner peripheral surface (301) of the circular flexible externally toothed gear (3), which face each other in the direction orthogonal to the rotation axis (Ax 1).

According to this aspect, the first gap (G21) forms a narrow path, and the foreign matter (X1) is easily prevented from entering the inner side of the outer ring (421).

According to an eighth aspect, in the harmonic gear device (1, 1A to 1G) according to the ninth aspect, the cover member (5, 5A to 5G) further has a convex portion (55), and the convex portion (55) protrudes from the base portion (51) and is inserted inside the outer ring (421). A second gap (G22) is formed between the outer peripheral surface (551) of the projection (55) and the inner peripheral surface (424) of the outer ring (421), which face each other in the direction orthogonal to the rotation axis (Ax 1).

According to this aspect, the second gap (G22) forms a narrow path, and the foreign matter (X1) is easily prevented from entering the inner side of the outer ring (421).

According to a ninth aspect, in the harmonic gear devices (1, 1A to 1G) relating to the tenth aspect, a third gap (G23) is formed between the base portion (51) and the outer ring (421) that face each other in the direction of the rotation axis (Ax 1). The first gap (G21) and the second gap (G22) are connected by a third gap (G23).

According to this aspect, a narrow path is formed by the first gap (G21), the second gap (G22), and the third gap (G23), and foreign matter (X1) is easily prevented from entering the inside of the outer ring (421).

According to any one of the first to tenth aspects, in the harmonic gear device (1, 1A to 1G) relating to the eleventh aspect, the cover member (5, 5A to 5G) is configured to block the passage of liquid.

According to this embodiment, the liquid can be blocked by the cover member (5, 5A-5G).

According to any one of the first to eleventh aspects, in the harmonic gear device (1, 1A to 1G) relating to the twelfth aspect, the cover member (5, 5A to 5G) has oil repellency.

According to this embodiment, the oil-laden foreign matter (X1) is less likely to adhere to the lid members (5, 5A-5G).

An actuator according to a thirteenth aspect includes: a harmonic gear device (1, 1A to 1G) according to any one of the first to twelfth aspects; a drive source (101) for rotating the cam (41); and an output unit (102) that outputs the rotational force of the circular flexible external gear (3).

According to this mode, there is an advantage that reduction in reliability is avoided and high reliability is achieved.

A cover body (10) according to a fourteenth aspect is configured such that the harmonic gear device (1, 1A to 1G) according to any one of the first to twelfth aspects is used as a cover member (5, 5A to 5G).

According to this mode, there is an advantage that reduction in reliability is avoided and high reliability is achieved.

The configurations according to the second to twelfth aspects are not essential to the harmonic gear devices (1, 1A to 1G), and can be omitted as appropriate.

Description of the reference numerals

1. 1A-1G harmonic gear device

2. Rigid internal gear

3. Flexible external gear

4. Wave generator

5,5A to 5G cover member

10. Cover body

21. Internal tooth

23. Guide part

31. External tooth

41. Cam wheel

42. Bearing assembly

51. Base part

52. Umbrella part

54. Lubricant agent

55. Convex part

100. Actuator

101. Driving source

102. Output unit

411. Peripheral surface

421. Outer ring

Ax1 rotating shaft

G1-G6 gap

G21 Second gap

G22 Second gap

G23 Third gap

Foreign matter X1

Industrial applicability

According to the embodiments of the present disclosure, it is possible to provide a harmonic gear device, an actuator, and a cover body with high reliability.

Claims (20)

1. A harmonic gear device, comprising:

   an annular rigid internal gear having internal teeth;

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

   a wave generator disposed inside the circular flexible external gear and configured to deflect the circular flexible external gear,

   in the harmonic gear device, the flexible externally toothed gear is deformed in accordance with rotation of the wave generator about a rotation axis, and the flexible externally toothed gear is caused to mesh with a part of the internal teeth, thereby rotating relative to the rigid internally toothed gear in accordance with a difference in the number of teeth between the flexible externally toothed gear and the rigid internally toothed gear,

   the wave generator has:

   a non-circular cam that is driven to rotate about the rotation axis; and

   a bearing disposed between an outer peripheral surface of the cam and an inner peripheral surface of the circular flexible externally toothed gear,

   the harmonic gear device further includes a cover member that is disposed to be opposed to the bearing from one side of the rotation shaft,

   the cover member faces the bearing while maintaining a gap between the cover member and an outer ring of the bearing, and prevents foreign matter from entering an inner side of the outer ring from one side of the rotary shaft.
2. The harmonic gear device according to claim 1,

   the cover member and the cam rotate at a constant speed.
3. The harmonic gear device according to claim 2,

   the cover member has an umbrella portion formed so that the distance from the rotating shaft gradually increases from the bearing side toward one side of the rotating shaft.
4. A harmonic gear device in accordance with claim 3,

   the harmonic gear device further includes a guide portion provided in the rigid internal gear and facing the umbrella portion with a gap of at least a certain amount.
5. The harmonic gear device according to any one of claims 1 to 4,

   the cover member has a non-circular portion corresponding to the cam when viewed from one side of the rotary shaft at a portion facing the bearing.
6. The harmonic gear device according to any one of claims 1 to 4,

   at least a portion of a gap between the outer race and the cover member is filled with a lubricant.
7. The harmonic gear device of claim 5 wherein,

   at least a portion of a gap between the outer race and the cover member is filled with a lubricant.
8. The harmonic gear device of claim 6 wherein,

   the lubricant is held in a gap between the outer ring and the cover member by a capillary phenomenon.
9. The harmonic gear device of claim 7 wherein,

   the lubricant is held in a gap between the outer ring and the cover member by a capillary phenomenon.
10. The harmonic gear device according to any one of claims 1 to 4 and 7 to 9, wherein,

    the cover member has a base portion disposed inside the circular flexible external gear,

    a first gap is formed between an outer peripheral surface of the base portion and an inner peripheral surface of the circular flexible external gear, and the outer peripheral surface of the base portion and the inner peripheral surface of the circular flexible external gear face each other in a direction orthogonal to the rotation axis.
11. The harmonic gear device of claim 5 wherein,

    the cover member has a base portion disposed inside the circular flexible external gear,

    a first gap is formed between an outer peripheral surface of the base portion and an inner peripheral surface of the circular flexible external gear, and the outer peripheral surface of the base portion and the inner peripheral surface of the circular flexible external gear face each other in a direction orthogonal to the rotation axis.
12. A harmonic gear device in accordance with claim 6,

    the cover member has a base portion disposed inside the circular flexible external gear,

    a first gap is formed between an outer peripheral surface of the base portion and an inner peripheral surface of the circular flexible external gear, and the outer peripheral surface of the base portion and the inner peripheral surface of the circular flexible external gear face each other in a direction orthogonal to the rotation shaft.
13. A harmonic gear device in accordance with claim 10,

    the cover member further has a projection projecting from the base and inserted inside the outer ring,

    a second gap is formed between an outer peripheral surface of the projection and an inner peripheral surface of the outer ring, the outer peripheral surface of the projection and the inner peripheral surface of the outer ring facing each other in a direction orthogonal to the rotation shaft.
14. The harmonic gear device of claim 11 wherein,

    the cover member further has a projection projecting from the base and inserted inside the outer ring,

    a second gap is formed between an outer peripheral surface of the projection and an inner peripheral surface of the outer ring, the outer peripheral surface of the projection and the inner peripheral surface of the outer ring facing each other in a direction orthogonal to the rotation shaft.
15. The harmonic gear device of claim 12 wherein,

    the cover member further has a projection projecting from the base and inserted inside the outer ring,

    a second gap is formed between an outer peripheral surface of the projection and an inner peripheral surface of the outer ring, the outer peripheral surface of the projection and the inner peripheral surface of the outer ring facing each other in a direction orthogonal to the rotation shaft.
16. The harmonic gear device according to any one of claims 13 to 15,

    a third gap is formed between the base and the outer ring, the base and the outer ring being opposed in the direction of the rotation shaft,

    the first gap and the second gap are connected by the third gap.
17. The harmonic gear device according to any one of claims 1 to 4, 7 to 9, and 11 to 15, wherein,

    the cover member is configured to block passage of liquid.
18. The harmonic gear device according to any one of claims 1 to 4, 7 to 9, and 11 to 15, wherein,

    the cover member has oleophobic properties.
19. An actuator, wherein the actuator

    A harmonic gear device including the harmonic gear device defined in any one of claims 1 to 18;

    a drive source that rotates the cam; and

    and an output unit that outputs the rotational force of the circular flexible external gear.
20. A cover body is provided, wherein,

    the harmonic gear device as recited in any one of claims 1 to 17 is used as the cover member.

Images