Harmonic gear unit, actuator and cover

Abstract

A harmonic gear device (1) deforms a flexible external gear (3) as a wave generator (4) rotates around a rotation axis (Ax1), causing a portion of the external teeth (31) to mesh with a portion of the internal teeth (21), thereby causing the flexible external gear (3) to rotate relative to the rigid internal gear (2) according to the difference in the number of teeth between the flexible external gear (3) and the rigid internal gear (2). The wave generator (4) includes: a non-circular cam (41) driven to rotate around the rotation axis (Ax1); and a bearing (42) arranged between the outer peripheral surface (411) of the cam (41) and the inner peripheral surface (301) of the flexible external gear (3). The harmonic gear device (1) also includes a cover member (5) arranged to face the bearing (42) from one side of the rotation axis (Ax1). The cover member (5) faces the bearing (42) while ensuring a gap (G1) between the cover member (5) and the outer ring (421) of the bearing (42), thereby preventing foreign matter (X1) from entering the inner side of the outer ring (421) from one side of the rotating axis Axl.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims the benefit of priority from Japanese patent application No. 2020-078964, filed on April 28, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] 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 Art

[0004] Patent Document 1 discloses that a flexible external gear in a wave gear device (flexure meshing gear device) is surface-treated by nitriding.

[0005] The wave gearing device comprises an annular rigid internal gear, a cup-shaped flexible external gear disposed inside the annular gear, and an elliptical wave generator embedded within the annular gear. The flexible external gear comprises a cylindrical body and external teeth formed on the outer circumference of the body. The wave generator bends the flexible external gear into an elliptical shape, with the external teeth at either end of the elliptical shape meshing with the internal teeth formed on the inner circumference of the rigid internal gear.

[0006] When the wave generator is rotated by a motor, for example, the meshing position of the two gears moves circumferentially, generating relative rotation between the two gears corresponding to the difference in the number of teeth between the internal and external teeth (2N, where N is a positive integer). When the rigid internal gear is fixed, the flexible external gear produces a rotational output significantly reduced by the difference in the number of teeth between the two gears.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-59153 Summary of the Invention

[0010] However, because a wave gearing system transmits power through the meshing of internal and external teeth while flexing a flexible external gear, wear between the internal and external teeth can generate foreign matter such as metal powder and nitrides, particularly over extended use. If such foreign matter enters the wave generator bearing, it could damage the surfaces of the outer and inner rings, or the rolling elements (balls), affecting the reliability of the wave gearing system.

[0011] The embodiments of the present disclosure are made in view of the above circumstances, and an object thereof is to provide a harmonic gear device, an actuator, and a cover with high reliability.

[0012] Solutions for solving technical problems

[0013] A harmonic gear device according to one embodiment of the present disclosure includes: 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 flexible external gear to cause the flexible external gear to flex. The harmonic gear device deforms the flexible external gear as the wave generator rotates about a rotation axis, causing a portion of the external teeth to mesh with a portion of the internal teeth, thereby causing the flexible external gear to rotate relative to the rigid internal gear by a difference in the number of teeth between the flexible external gear and the rigid internal gear. The wave generator includes: a non-circular cam driven to rotate about the rotation axis; and a bearing disposed between the outer circumferential surface of the cam and the inner circumferential surface of the flexible external gear. The harmonic gear device also includes a cover member disposed so as to face the bearing from one side of the rotation axis. The cover member faces the bearing with a gap secured between the cover member and the outer ring of the bearing, thereby preventing foreign matter from entering the inner side of the outer ring from one side of the rotating shaft.

[0014] An actuator according to one aspect of the embodiment of the present disclosure includes: the wave gear device; a drive source for rotating the cam; and an output unit for outputting a rotational force of the flexible externally toothed gear.

[0015] The cover according to one aspect of the embodiment of the present disclosure is used as the cover member in the wave gear device.

[0016] Effects of the Invention

[0017] According to the embodiments of the present disclosure, there is an advantage of avoiding reliability degradation and thus achieving high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A This is a cross-sectional view showing a schematic structure of a wave gear device according to the first embodiment. Figure 1B yes Figure 1A Magnified view of area Z1.

[0019] Figure 2A This is a schematic diagram of the above-mentioned wave gear device viewed from the input shaft of the rotating shaft with the cover member removed. Figure 2B This is a schematic diagram of the above-mentioned wave gear device viewed from the input side of the rotating shaft.

[0020] Figure 3AThis is a schematic exploded perspective view of the above-mentioned wave gear device viewed from the output side of the rotating shaft. Figure 3B This is a schematic exploded perspective view of the above-mentioned wave gear device viewed from the input side of the rotating shaft.

[0021] Figure 4 This is a cross-sectional view showing a schematic structure of an actuator including the above-mentioned wave gear device.

[0022] Figure 5A and Figure 5B This is an enlarged view of the periphery of the umbrella portion of the cover member in the above-mentioned wave gear device.

[0023] Figure 6 This is a cross-sectional view showing an example of a robot using the above-mentioned wave gear device.

[0024] Figure 7A This is a cross-sectional view showing a schematic structure of a wave gear device according to a second embodiment. Figure 7B yes Figure 7A An enlarged view of the main part.

[0025] Figure 8A This is a cross-sectional view schematically illustrating the structure of a wave gear device according to a first modified example of the second embodiment. Figure 8B yes Figure 8A An enlarged view of the main part.

[0026] Figure 9A This is a cross-sectional view schematically illustrating a structure of a wave gear device according to a second modified example of the second embodiment. Figure 9B yes Figure 9A An enlarged view of the main part.

[0027] Figure 10A 、 Figure 10B and Figure 10C These are cross-sectional views of main parts schematically illustrating the configuration of wave gear devices according to third, fourth, and fifth modifications of the second embodiment.

[0028] Figure 11A This is a cross-sectional view showing a schematic structure of a wave gear device according to a third embodiment. Figure 11B yes Figure 11A An enlarged view of the main part. DETAILED DESCRIPTION

[0029] (Implementation Method)

[0030] (1) Summary

[0031] Hereinafter, for an overview of the wave gear device 1 according to this embodiment, refer to Figures 1A to 4The drawings referred to in the embodiments of the present disclosure are all schematic diagrams, and the size and thickness ratios of the structural elements in the drawings are not necessarily limited to reflect the actual size ratios. For example, Figures 2A to 3B The tooth shapes, sizes, and numbers of teeth of the internal teeth 21 and the external teeth 31 are schematically shown for the purpose of explanation only, and are not intended to be limiting.

[0032] The harmonic wave gearing device 1 according to this embodiment is a gearing device comprising a rigid internal gear 2, a flexible external gear 3, and a wave generator 4. In this harmonic wave gearing device 1, the annular flexible external gear 3 is disposed inside the annular rigid internal gear 2, and the wave generator 4 is further disposed inside the flexible external gear 3. The wave generator 4 bends the flexible external gear 3 into a non-circular shape, causing the external teeth 31 of the flexible external gear 3 to partially mesh with the internal teeth 21 of the rigid internal gear 2. When the wave generator 4 rotates, the meshing position between the internal teeth 21 and the external teeth 31 moves along the circumferential direction of the rigid internal gear 2, causing relative rotation between the two gears (rigid internal gear 2 and flexible external gear 3) by the difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2. If the rigid internal gear 2 is fixed, the flexible external gear 3 rotates in conjunction with the relative rotation of the two gears. As a result, a rotational output reduced in speed at a relatively high reduction ratio according to the difference in the number of teeth between the two gears can be obtained from the flexible externally toothed gear 3 .

[0033] The wave generator 4 for bending the flexible external gear 3 has a rotation axis Ax1 on the input side (see Figure 1A ) and a bearing 42. The bearing 42 is positioned between the outer circumferential surface 411 of the cam 41 and the inner circumferential surface 301 of the flexible external gear 3. The inner ring 422 of the bearing 42 is fixed to the outer circumferential surface 411 of the cam 41. The outer ring 421 of the bearing 42 is elastically deformed by the pressure of the cam 41 via ball-shaped rolling elements 423. The rolling of the rolling elements 423 allows the outer ring 421 to rotate relative to the inner ring 422. Therefore, when the non-circular cam 41 rotates, the rotation of the inner ring 422 is not transmitted to the outer ring 421. Instead, the outer teeth 31 of the flexible external gear 3, which are pressed by the cam 41, generate a fluctuating motion. This fluctuating motion of the outer teeth 31 causes the meshing position of the inner teeth 21 and 31 to shift along the circumferential direction of the rigid internal gear 2, as described above. This causes relative rotation between the flexible external gear 3 and the rigid internal gear 2.

[0034] In summary, in this wave gear device 1, the wave generator 4 having the bearing 42 realizes power transmission through the meshing of the internal teeth 21 and the external teeth 31 while bending the flexible external gear 3. Therefore, especially when used for a long time, there is a possibility that foreign matter X1 such as metal powder or nitride will be generated due to wear between the internal teeth 21 and the external teeth 31 (see Figure 5A If such foreign matter X1 enters the bearing 42, it may damage the surface of any of the outer ring 421, inner ring 422, or rolling elements 423 of the bearing 42, thereby affecting the reliability of the harmonic gear device 1. The harmonic gear device 1 according to this embodiment mainly suppresses the entry of foreign matter X1 into the bearing 42 through the following structure, thereby preventing a reduction in reliability.

[0035] That is, Figures 1A to 3B As shown, the wave gear device 1 according to this embodiment includes: an annular rigid internal gear 2 having internal teeth 21; an annular flexible external gear 3 having external teeth 31; and a wave generator 4. The flexible external gear 3 is arranged inside the rigid internal gear 2. As the wave generator 4 rotates about the rotation axis Ax1, the wave gear device 1 deforms the flexible external gear 3, causing a portion of the external teeth 31 to mesh with a portion of the internal teeth 21, thereby rotating the flexible external gear 3 by the difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2. The wave generator 4 includes a bearing 42 and a non-circular cam 41. The cam 41 is driven to rotate about the rotation axis Ax1. The bearing 42 is arranged between the outer circumferential surface 411 of the cam 41 and the inner circumferential surface 301 of the flexible external gear 3. The wave gear device 1 also includes a cover member 5. The cover member 5 is arranged so as to face the bearing 42 from one side of the rotation axis Ax1. A gap G1 is ensured between the cover member 5 and the outer ring 421 of the bearing 42 (see Figure 1B ) is opposite to the bearing 42, thereby preventing foreign matter X1 from entering the inner side of the outer ring 421 from one side of the rotation axis Ax1.

[0036] According to this embodiment, the cover member 5, positioned so as to face the bearing 42 from one side of the rotation axis Ax1, prevents foreign matter X1 from entering the inner side of the outer ring 421 of the bearing 42 from the one side of the rotation axis Ax1. Therefore, even if foreign matter X1 such as metal powder or nitrides is generated due to wear between the internal teeth 21 and the external teeth 31 over a long period of use of the wave gear device 1, this foreign matter X1 can be prevented from entering the bearing 42 (inside the outer ring 421). As a result, damage to the outer ring 421, inner ring 422, and rolling elements 423 of the bearing 42 by foreign matter X1 is less likely to occur, and the reliability of the wave gear device 1 is not reduced due to damage to the bearing 42. Therefore, the wave gear device 1 according to this embodiment has the advantage of high reliability. Furthermore, the wave gear device 1 according to this embodiment does not suffer a decrease in reliability even after long-term use, thereby achieving a long life and high performance of the wave gear device 1.

[0037] In addition, if Figure 4 As shown, the strain wave gear device 1 according to this embodiment, together with a drive source 101 and an output unit 102, constitutes an actuator 100. In other words, the actuator 100 according to this embodiment includes the strain wave gear device 1, the drive source 101, and the output unit 102. The drive source 101 rotates the cam 41. The output unit 102 extracts the rotational force of the flexible externally toothed gear 3 as an output.

[0038] The cover member 5 of the wave gear device 1 according to the present embodiment constitutes a cover body 10 (see Figure 1A ). In other words, the cover 10 according to the present embodiment is used as the cover member 5 in the wave gear device 1. That is, the cover 10 is the cover member 5.

[0039] According to the actuator 100 and the cover 10 according to this embodiment, there is an advantage that the reliability of the wave gear device 1 is high.

[0040] (2) Definition

[0041] The term "annular" as used in the embodiments of the present disclosure refers to a shape that, at least when viewed from above, encloses a space (region) within a ring (ring). This shape is not limited to a true circle (annular) when viewed from above; for example, an elliptical or polygonal shape is also possible. Furthermore, a flexible external gear 3 having a base 322, such as a cup-shaped flexible external gear 3, may be considered "annular" if its body 321 is annular.

[0042] The term "obstruction" used in the embodiments of this disclosure means hindering or blocking, not completely blocking. That is, the cover member 5 that prevents foreign matter X1 from entering the inner side of the outer ring 421 only needs to prevent the foreign matter X1 from entering the inner side of the outer ring 421; it does not necessarily need to completely block the foreign matter X1. In other words, the cover member 5 only needs to inhibit the foreign matter X1 from entering the inner side of the outer ring 421, which, in turn, reduces the amount of foreign matter X1 that enters the inner side of the outer ring 421. Of course, the cover member 5 can also completely block the foreign matter X1 from entering the inner side of the outer ring 421.

[0043] The "foreign matter" referred to in the embodiments of this disclosure refers to matter other than the original components of the wave gear device 1. Examples include metal powder and nitrides generated by wear between the internal teeth 21 and the external teeth 31. In other words, the foreign matter X1 that is prevented from entering the inner side of the outer ring 421 by the cover member 5 is not limited to matter generated by wear within the wave gear device 1. For example, it also includes dust, sand, and dirt that enters from outside the wave gear device 1.

[0044] The "rigidity" mentioned in the embodiments of the present disclosure refers to the property of an object to resist deformation when an external force is applied to the object. In other words, an object with rigidity is difficult to deform even if an external force is applied. In addition, the "flexibility" mentioned in the embodiments of the present disclosure refers to the property of an object to undergo elastic deformation (bending) when an external force is applied to the object. In other words, an object with flexibility is prone to elastic deformation when an external force is applied. Therefore, "rigidity" and "flexibility" have opposite meanings.

[0045] In particular, in the disclosed embodiments, the terms "rigidity" of the rigid internal gear 2 and "flexibility" of the flexible external gear 3 are used relative to each other. Specifically, the "rigidity" of the rigid internal gear 2 means that it possesses relatively high rigidity, at least compared to the flexible external gear 3. This means that it is difficult to deform even when external forces are applied. Similarly, the "flexibility" of the flexible external gear 3 means that it possesses relatively high flexibility, at least compared to the rigid internal gear 2. This means that it easily elastically deforms when external forces are applied.

[0046] In addition, in the embodiment of the present disclosure, one side of the rotation axis Ax1 ( Figure 1A The right side of the rotation axis Ax1 is called the "input side", and the other side of the rotation axis Ax1 ( Figure 1A The left side of the output is called the "output side". Figure 1A In the example shown in FIG1 , the cover member 5 is arranged to face the bearing 42 from the "input side" of the rotation axis Ax1. However, the terms "input side" and "output side" are merely labels given for the purpose of explanation and are not intended to limit the positional relationship between the input and output as viewed from the wave gear device 1.

[0047] The term "non-circular shape" used in the embodiments of this disclosure refers to shapes that are not perfectly circular, including, for example, ellipses and oval shapes. As an example in this embodiment, the non-circular cam 41 of the wave generator 4 is elliptical. In other words, in this embodiment, the wave generator 4 bends the flexible external gear 3 into an elliptical shape.

[0048] The "elliptical shape" mentioned in the embodiments of the present disclosure refers to a shape in which a perfect circle is flattened so that the intersection of the major axis and the minor axis, which are orthogonal to each other, is located at the center. It is not limited to a curve consisting of a set of points whose sum of distances from two fixed points on a plane is constant, that is, a mathematical "ellipse". In other words, the cam 41 in this embodiment can also be a curve consisting of a set of points whose sum of distances from two fixed points on a plane is constant, like a mathematical "ellipse", or it can be an elliptical shape like an elongated circle instead of a mathematical "ellipse". As mentioned above, the drawings referenced in the embodiments of the present disclosure are all schematic diagrams, and the ratios of the sizes and thicknesses of the various structural elements in the drawings are not necessarily limited to reflecting the actual size ratios. As mentioned above, the drawings referenced in the embodiments of the present disclosure are all schematic diagrams, and the ratios of the sizes and thicknesses of the various structural elements in the drawings are not necessarily limited to reflecting the actual size ratios.

[0049] The "rotation axis" referred to in the embodiments of this disclosure refers to a virtual axis (straight line) that serves as the center of rotation of a rotating body. In other words, the rotation axis Ax1 is a virtual axis without a physical entity. The wave generator 4 rotates about the rotation axis Ax1.

[0050] The terms "internal teeth" and "external teeth" used in the present disclosure refer to a collection (group) of multiple "teeth" rather than individual "teeth." Specifically, the internal teeth 21 of the rigid internal gear 2 comprise a collection of multiple teeth formed on its inner circumference. Similarly, the external teeth 31 of the flexible external gear 3 comprise a collection of multiple teeth formed on its outer circumference.

[0051] (3) Composition

[0052] For detailed structures of the wave gear device 1 and the actuator 100 according to this embodiment, refer to Figures 1A to 4 Provide explanation.

[0053] Figure 1A is a cross-sectional view showing a schematic structure of the harmonic gear device 1. Figure 1B yes Figure 1A Magnified view of area Z1. Figure 2A From the input side of the rotation axis Ax1 ( Figure 1A Schematic diagram of the wave gear device 1 with the cover member 5 removed, as viewed from the right side of the figure. Figure 2BThis is a schematic diagram of the wave gear device 1 including the cover member 5 , viewed from the input side of the rotation axis Ax1 . Figure 3A From the output side of the rotation axis Ax1 ( Figure 1A A schematic exploded perspective view of the harmonic gear device 1 as viewed from the left side of the figure. Figure 3B It is a schematic exploded perspective view of the wave gear device 1 as viewed from the input side of the rotation axis Ax1. Figure 4 1 is a cross-sectional view showing a schematic structure of an actuator 100 including the wave gear device 1 .

[0054] (3.1) Harmonic gear device

[0055] As described above, the wave gear device 1 according to this embodiment includes a rigid internal gear 2, a flexible external gear 3, a wave generator 4, and a cover member 5. In this embodiment, the components of the wave gear device 1, namely the rigid internal gear 2, the flexible external gear 3, the wave generator 4, and the cover member 5, are made of a metal such as stainless steel, cast iron, carbon steel for machine structures, chrome-molybdenum steel, phosphor bronze, or aluminum bronze. The metal referred to herein includes metals that have undergone surface treatments such as nitriding.

[0056] Furthermore, in this embodiment, a cup-type wave gearing device is illustrated as an example of a wave gearing device 1. Specifically, the wave gearing device 1 according to this embodiment uses a cup-shaped flexible externally toothed gear 3. The wave generator 4 is combined with the cup-shaped flexible externally toothed gear 3 so as to be housed within the cup-shaped flexible externally toothed gear 3.

[0057] In addition, as an example of the present embodiment, the wave gear device 1 is configured such that the rigid internal gear 2 is fixed to the input side housing 111 (see Figure 4 ) and the output side housing 112 (refer to Figure 4 ) etc. Thus, as the rigid internal gear 2 and the flexible external gear 3 rotate relative to each other, the flexible external gear 3 rotates relative to the fixed member (the input side housing 111 etc.).

[0058] Furthermore, in this embodiment, when the wave gear device 1 is used in the actuator 100, a rotational force is applied as input to the wave generator 4, thereby extracting a rotational force as output from the flexible externally toothed gear 3. In other words, the wave gear device 1 operates using the rotation of the wave generator 4 as input rotation and the rotation of the flexible externally toothed gear 3 as output rotation. As a result, the wave gear device 1 can produce an output rotation that is reduced by a high reduction ratio relative to the input rotation.

[0059] Furthermore, in the wave gear device 1 according to this embodiment, the input-side rotation axis Ax1 and the output-side rotation axis Ax2 are collinear. In other words, the input-side rotation axis Ax1 and the output-side rotation axis Ax2 are coaxial. Here, the input-side rotation axis Ax1 is the rotation center of the wave generator 4 to which the input rotation is applied, while the output-side rotation axis Ax1 is the rotation center of the flexible externally toothed gear 3 that generates the output rotation. In other words, the wave gear device 1 can produce output rotation that is reduced at a high reduction ratio relative to the input rotation while being coaxial.

[0060] The rigid internal gear 2, also called a circular spline, is an annular component having internal teeth 21. In the present embodiment, the rigid internal gear 2 has an annular shape, at least the inner circumference of which is a perfect circle when viewed from above. On the inner circumference of the annular rigid internal gear 2, internal teeth 21 are formed along the circumferential direction of the rigid internal gear 2. The plurality of teeth constituting the internal teeth 21 are all of the same shape and are arranged at equal intervals over the entire circumferential area of ​​the inner circumference of the rigid internal gear 2. In other words, the pitch circle of the internal teeth 21 is a perfect circle when viewed from above. In addition, the rigid internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. The internal teeth 21 are all formed over the entire length of the rigid internal gear 2 in the thickness direction. The tooth lines of the internal teeth 21 are all parallel to the rotation axis Ax1.

[0061] As described above, the rigid internal gear 2 is fixed to the input side housing 111 (see Figure 4 ) and the output side housing 112 (refer to Figure 4 ) etc. Therefore, a plurality of fixing holes 22 for fixing are formed in the rigid internal gear 2 .

[0062] The flexible external gear 3, also known as a flex spline, is an annular component having external teeth 31. In this embodiment, the flexible external gear 3 is formed into a cup shape using a relatively thin metal elastic body (metal plate). In other words, the flexible external gear 3 is flexible due to its relatively small thickness (thinness). The flexible external gear 3 has a cup-shaped main body 32. The main body 32 has a body 321 and a bottom 322. When the flexible external gear 3 is not elastically deformed, at least the inner circumferential surface 301 of the body 321 has a cylindrical shape that is a perfect circle when viewed from above. The central axis of the body 321 coincides with the rotation axis Ax1. The bottom 322 is located on one of the openings of the body 321 and has a disc-like shape that is a perfect circle when viewed from above. The bottom 322 is located on the output side of the pair of openings of the body 321, whichever is closer to the rotation axis Ax1. As described above, the main body 32 is formed into a bottomed cylindrical, or cup-shaped, shape that is open toward the input side of the rotation axis Ax1, by the body 321 and the bottom 322. In this embodiment, the body 321 and the bottom 322 are integrally formed from a single metal member, thereby achieving a seamless main body 32.

[0063] Here, the wave generator 4, which has a non-circular (elliptical) shape, is combined with the flexible external gear 3 by embedding the wave generator 4 inside the body 321. This causes the flexible external gear 3 to be elastically deformed into a non-circular shape by receiving an external force in the radial direction (a direction perpendicular to the rotation axis Ax1) from the inside toward the outside from the wave generator 4. In this embodiment, the combination of the wave generator 4 and the flexible external gear 3 causes the body 321 of the flexible external gear 3 to elastically deform into an elliptical shape. In other words, the state in which the flexible external gear 3 is not elastically deformed refers to the state in which the wave generator 4 is not combined with the flexible external gear 3. Conversely, the state in which the flexible external gear 3 is elastically deformed refers to the state in which the wave generator 4 is combined with the flexible external gear 3.

[0064] Furthermore, external teeth 31 are formed along the circumference of the body 321 at least at the end of the outer circumferential surface of the body 321 on the side opposite the bottom 322 (the input side of the rotation axis Ax1). The multiple teeth comprising the external teeth 31 are all identical in shape and are arranged at equal intervals throughout the circumferential area of ​​the outer circumferential surface of the flexible external gear 3. In other words, the pitch circle of the external teeth 31 is a true circle when viewed from above when the flexible external gear 3 is not elastically deformed. The external teeth 31 are formed only within a range of a constant width from the end edge of the opening side of the body 321 (the input side of the rotation axis Ax1). The tooth lines of the external teeth 31 are all parallel to the rotation axis Ax1.

[0065] As described above, in this embodiment, the rotation of the flexible externally geared wheel 3 is taken out as the output rotation. Therefore, the output portion 102 (see FIG. 1 ) of the actuator 100 is attached to the flexible externally geared wheel 3. Figure 4 The bottom 322 of the flexible externally toothed gear 3 is formed with a plurality of mounting holes 33 for mounting the shaft serving as the output portion 102. Furthermore, a through-hole 34 is formed in the center of the bottom 322. The area around the through-hole 34 in the bottom 322 is thicker than the rest of the bottom 322.

[0066] The flexible external gear 3 thus constructed is positioned inside the rigid internal gear 2. The flexible external gear 3 is assembled with the rigid internal gear 2 so that only the end of the outer circumferential surface of the body portion 321, on the side opposite the bottom portion 322 (the input side of the rotation axis Ax1), is inserted into the inner side of the rigid internal gear 2. External teeth 31 are formed on the outer circumferential surface of the flexible external gear 3, while internal teeth 21 are formed on the inner circumferential surface of the rigid internal gear 2. Therefore, when the flexible external gear 3 is positioned inside the rigid internal gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0067] Here, the number of teeth of the internal teeth 21 of the rigid internal gear 2 is 2N greater than the number of teeth of the external teeth 31 of the flexible external gear 3 (N is a positive integer). As an example of this embodiment, N is "1," and the number of teeth of the flexible external gear 3 (external teeth 31) is "2" greater than the number of teeth of the rigid internal gear 2 (internal teeth 21). This difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation to the input rotation in the wave gearing device 1.

[0068] In this embodiment, as an example, the dimensions of the external teeth 31 in the tooth trace direction (parallel to the rotation axis Ax1) are smaller than the dimensions of the internal teeth 21 in the tooth trace direction (parallel to the rotation axis Ax1). In other words, the external teeth 31 fit within the tooth trace of the internal teeth 21 in the direction parallel to the rotation axis Ax1.

[0069] However, when the flexible external gear 3 is not elastically deforming (when the wave generator 4 is not attached to the flexible external gear 3), the pitch circle of the external teeth 31, which describe a perfect circle, is set slightly smaller than the pitch circle of the internal teeth 21, which also describe a perfect circle. In other words, when the flexible external gear 3 is not elastically deforming, the external teeth 31 and the internal teeth 21 face each other with a gap therebetween, and do not mesh with each other.

[0070] On the other hand, when the flexible external gear 3 is elastically deformed (the wave generator 4 and the flexible external gear 3 are assembled), the body portion 321 is bent into an elliptical shape (non-circular shape), so the external teeth 31 of the flexible external gear 3 and the internal teeth 21 of the rigid internal gear 2 are partially engaged. Figure 2AAs shown, since the flexible external gear 3 (its body portion 321) elastically deforms into an elliptical shape, the external teeth 31 located at both ends of the elliptical shape in the major axis direction 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 perfectly circular internal teeth 21, while the minor diameter of the pitch circle of the elliptical external teeth 31 is smaller than the diameter of the pitch circle of the perfectly circular internal teeth 21. Thus, when the flexible external gear 3 elastically deforms, a portion of the multiple teeth comprising the external teeth 31 mesh with a portion of the multiple teeth comprising the internal teeth 21. Consequently, in the wave gearing device 1, a portion of the external teeth 31 can mesh with a portion of the internal teeth 21.

[0071] The wave generator 4, also called a wave generator, bends the flexible externally gear 3, thereby generating a wave motion in the external teeth 31 of the flexible externally gear 3. In this embodiment, the wave generator 4 has a non-circular outer peripheral shape, specifically an elliptical shape, when viewed from above.

[0072] The wave generator 4 includes a non-circular (here, elliptical) cam 41 and a bearing 42 mounted on the outer circumference of the cam 41. Specifically, the cam 41 and bearing 42 are combined so that the non-circular (elliptical) cam 41 is embedded inside the inner ring 422 of the bearing 42. Consequently, the bearing 42 is elastically deformed into a non-circular shape by receiving an external force in the radial direction (orthogonal to the rotation axis Ax1) from the inside of the inner ring 422 toward the outside of the cam 41. This force is applied to the bearing 42 in the radial direction (orthogonal to the rotation axis Ax1) from the inside of the inner ring 422. This force is applied to the bearing 42 in the non-circular shape. In other words, the state in which the bearing 42 is not elastically deformed refers to the state in which the cam 41 and bearing 42 are not combined. Conversely, the state in which the bearing 42 is elastically deformed refers to the state in which the cam 41 and bearing 42 are combined.

[0073] The cam 41 is a non-circular (here, elliptical) component that is driven to rotate about the input-side rotation axis Ax1. The cam 41 has an outer peripheral surface 411 (see Figure 1B ), at least the outer peripheral surface 411 is made of a metal plate that is elliptical in a plan view. The cam 41 has a predetermined thickness in the direction of the rotation axis Ax1. Thus, the cam 41 has the same degree of rigidity as the rigid internal gear 2. However, the thickness of the cam 41 is smaller (thinner) than the thickness of the rigid internal gear 2. As described above, in this embodiment, the rotation of the wave generator 4 is used as the input rotation. Therefore, the input portion 103 of the actuator 100 (see Figure 4 A cam hole 43 for mounting a shaft serving as the input unit 103 is formed in the center of the cam 41 of the wave generator 4 .

[0074] The bearing 42 includes an outer ring 421, an inner ring 422, and a plurality of rolling elements 423. In the present embodiment, the bearing 42 includes a deep groove ball bearing using balls as the rolling elements 423, as an example.

[0075] The outer ring 421 and inner ring 422 are both annular components. They are formed into an annular shape using a thin-walled metal elastic body (metal plate). In other words, their relatively small thickness (thinness) gives them flexibility. In this embodiment, when the bearing 42 is not elastically deformed (when the cam 41 is not assembled with the bearing 42), both the outer ring 421 and the inner ring 422 have a perfectly circular annular shape when viewed from above. The inner ring 422 is slightly smaller than the outer ring 421 and is positioned inside it. Because the inner diameter of the outer ring 421 is larger than the outer diameter of the inner ring 422, a gap is created between the inner circumference of the outer ring 421 and the outer circumference of the inner ring 422.

[0076] Multiple rolling elements 423 are arranged in the gap between the outer ring 421 and the inner ring 422. They are arranged in a row along the circumference of the outer ring 421. These rolling elements 423 are metal balls (balls) of identical shape and are spaced evenly across the entire circumference of the outer ring 421. Although not specifically shown, the bearing 42 also includes a retainer, which holds the rolling elements 423 between the outer ring 421 and the inner ring 422.

[0077] In addition, as an example of this embodiment, the dimension of the inner ring 422 in the width direction (the direction parallel to the rotation axis Ax1) is the same as the thickness of the cam 41. The dimension of the outer ring 421 in the width direction (the direction parallel to the rotation axis Ax1) is larger than the dimension of the inner ring 422 in the width direction. In this embodiment, as Figure 1B As shown, the outer ring 421 and inner ring 422 are positioned so that their end faces on the output side of the rotation axis Ax1 are flush. Therefore, on the input side of the rotation axis Ax1, the outer ring 421 protrudes relative to the inner ring 422. Furthermore, the width dimension of the outer ring 421 is smaller than the thickness of the rigid internal gear 2.

[0078] With this bearing 42 structure, the cam 41 and bearing 42 are combined, securing the inner ring 422 of the bearing 42 to the cam 41. The inner ring 422 elastically deforms into an elliptical shape similar to the outer periphery of the cam 41. At this point, the outer ring 421 of the bearing 42 is pressed against the inner ring 422 via the multiple rolling elements 423, elastically deforming into the elliptical shape. Consequently, both the outer ring 421 and the inner ring 422 of the bearing 42 are elastically deformed into elliptical shapes. Thus, when the bearing 42 is elastically deformed (when the cam 41 and bearing 42 are assembled), the outer ring 421 and the inner ring 422 maintain similar elliptical shapes.

[0079] Even when bearing 42 is elastically deformed, the gap between the outer ring 421 and the inner ring 422 is maintained substantially constant throughout the entire circumference of the outer ring 421 due to the presence of multiple rolling elements 423 between them. Furthermore, in this state, the rolling of the multiple rolling elements 423 between the outer ring 421 and the inner ring 422 allows the outer ring 421 to rotate relative to the inner ring 422. Therefore, when the cam 41 rotates about the rotation axis Ax1 while bearing 42 is elastically deformed, the rotation of the cam 41 is not transmitted to the outer ring 421, but the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 via the multiple rolling elements 423. In other words, in the wave generator 4, when the cam 41 rotates about the rotation axis Ax1, the outer ring 421 elastically deforms so that the major axis of the elliptical shape emulated by the outer ring 421 rotates about the rotation axis Ax1. Therefore, the outer peripheral shape of the wave generator 4 as a whole, which is an ellipse as viewed from the input side of the rotation axis Ax1, changes with the rotation of the cam 41 so that its major axis rotates around the rotation axis Ax1.

[0080] The wave generator 4, constructed in this manner, is positioned inside the flexible externally geared gear 3. Here, the flexible externally geared gear 3 and wave generator 4 are combined so that only the end portion of the inner circumferential surface 301 of the body portion 321, on the side opposite the bottom portion 322 (the input side of the rotation axis Ax1), is engaged with the wave generator 4. The bearing 42 of the wave generator 4 is positioned between the outer circumferential surface 411 of the cam 41 and the inner circumferential surface 301 of the flexible externally geared gear 3. When the bearing 42 is not elastically deformed (when the cam 41 is not assembled with the bearing 42), the outer diameter of the outer ring 421 is the same as the inner diameter of the flexible externally gear 3 (body portion 321) in the similarly undeformed state. Therefore, the outer circumferential surface of the outer ring 421 of the wave generator 4 is in contact with the inner circumferential surface 301 of the flexible externally geared gear 3 without any gap. Thus, when the flexible external gear 3 is elastically deformed (wave generator 4 and flexible external gear 3 are combined), the body 321 bends into an elliptical shape (non-circular shape). In this state, the flexible external gear 3 is fixed to the outer ring 421 of the bearing 42.

[0081] The cover member 5 is arranged to face at least the bearing 42 from one side (input side) of the rotation axis Ax1. A gap G1 is ensured between the cover member 5 and the outer ring 421 of the bearing 42 (see Figure 1B ) is opposite to the bearing 42, thereby preventing the foreign matter X1 (refer to Figure 5A ) enters the inner side of the outer ring 421 from one side (input side) of the rotation axis Ax1. The cover member 5 will be described in detail in the column "(3.3) Cover member".

[0082] like Figure 2AAs shown, in the above-described wave gearing device 1, the body portion 321 of the flexible externally geared gear 3 flexes into an elliptical (non-circular) shape, causing the external teeth 31 of the flexible externally geared gear 3 to partially mesh with the internal teeth 21 of the rigid internally geared gear 2. Specifically, as the flexible externally gear 3 (the body portion 321) elastically deforms into an elliptical shape, the external teeth 31 at two locations, corresponding to the ends of the elliptical shape in the major axis direction, mesh with the internal teeth 21. Furthermore, when the cam 41 rotates about the rotation axis Ax1, the rotation of the cam 41 is not transmitted to the outer ring 421 and the flexible externally geared gear 3. Instead, the elastic deformation of the inner ring 422 is transmitted to the outer ring 421 and the flexible externally gear 3 via the multiple rolling elements 423. Therefore, the outer peripheral shape of the flexible externally gear 3, which is elliptical as viewed from the input side of the rotation axis Ax1, changes with the rotation of the cam 41, such that its major axis rotates about the rotation axis Ax1.

[0083] As a result, the external teeth 31 formed on the outer circumference of the flexible external gear 3 generate a fluctuating motion. This fluctuating motion of the external teeth 31 causes the meshing position between the internal teeth 21 and the external teeth 31 to shift along the circumferential direction of the rigid internal gear 2, causing the flexible external gear 3 to rotate relative to the rigid internal gear 2. Specifically, since the external teeth 31 mesh with the internal teeth 21 at both ends of the elliptical shape formed by (the body portion 321 of) the flexible external gear 3 along the major axis, the gear rotates about the rotation axis Ax1 about the major axis of the elliptical shape, shifting the meshing position between the internal teeth 21 and the external teeth 31. Thus, in the wave gear device 1 according to this embodiment, the rotation of the wave generator 4 about the rotation axis Ax1 deforms the flexible external gear 3, causing a portion of the external teeth 31 to mesh with a portion of the internal teeth 21, thereby causing the flexible external gear 3 to rotate by the difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2.

[0084] As described above, in the wave gearing 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 relative to the input rotation in the wave gearing device 1. Specifically, assuming the number of teeth of the rigid internally toothed gear 2 is "V1" and the number of teeth of the flexible externally toothed gear 3 is "V2," the reduction ratio R1 is expressed by the following equation 1.

[0085] R1=V2 / (V1-V2)……(Formula 1)

[0086] In general, the smaller the difference in the number of teeth (V1 - V2) between the rigid internal gear 2 and the flexible external gear 3, the greater the reduction ratio R1. For example, if the number of teeth V1 of the rigid internal gear 2 is 202 and the number of teeth V2 of the flexible external gear 3 is 200, the difference (V1 - V2) is 2. Therefore, according to the above equation 1, the reduction ratio R1 is 100. In this case, when the cam 41 rotates clockwise around the rotation axis Ax1 once (360 degrees), the flexible external gear 3 rotates counterclockwise around the rotation axis Ax1 by the difference in the number of teeth, 2 (i.e., 3.6 degrees).

[0087] According to the wave gear device 1 of the present embodiment, such a high reduction ratio R1 can be achieved by the combination of the single-stage gears (the rigid internal gear 2 and the flexible external gear 3 ).

[0088] The wave gear device 1 only needs to include at least the rigid internal gear 2 , the flexible external gear 3 , the wave generator 4 , and the cover member 5 , and may further include the spline bushing 113 described in the section “(3.2) Actuator” as a component.

[0089] (3.2) Actuator

[0090] Next, the structure of the actuator 100 according to this embodiment will be described in more detail.

[0091] like Figure 4 As shown, the actuator 100 according to this embodiment includes the wave gear device 1 according to this embodiment, a drive source 101, and an output unit 102. Specifically, the actuator 100 includes the drive source 101 and the output unit 102, in addition to the rigid internal gear 2, flexible external gear 3, wave generator 4, and cover member 5 that constitute the wave gear device 1. Furthermore, in addition to the wave gear device 1, the drive source 101, and the output unit 102, the actuator 100 also includes an input unit 103, an input-side housing 111, an output-side housing 112, a spline bushing 113, a spacer 114, a first stopper 115, a second stopper 116, and a mounting plate 117. Furthermore, in this embodiment, the actuator 100 also 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.

[0092] In this embodiment, the material of the actuator 100 components other than the drive source 101 , the input oil seal 120 , and the output oil seal 123 is metal such as stainless steel, cast iron, carbon steel for mechanical structures, chrome-molybdenum steel, phosphor bronze, or aluminum bronze.

[0093] The drive source 101 is a power source such as a 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 drive source 101 is connected to a shaft serving as an input portion 103, and the power generated by the drive source 101 is transmitted to the cam 41 via the input portion 103. As a result, the drive source 101 can rotate the cam 41.

[0094] The output portion 102 is a cylindrical shaft arranged along the output-side rotation axis Ax2. The central axis of the output portion 102 is aligned with the rotation axis Ax2. The output portion 102 is held rotatably about the rotation axis Ax2 by the output-side housing 112. The output portion 102 is fixed to the bottom 322 of the main body 32 of the flexible externally gear 3 and rotates along with the flexible externally gear 3 about the rotation axis Ax2. In other words, the output portion 102 extracts the rotational force of the flexible externally gear 3 as output.

[0095] The input part 103 is a cylindrical shaft arranged along the rotation axis Ax1 on the input side. The central axis of the shaft of the input part 103 is consistent with the rotation axis Ax1. The input part 103 is maintained by the input side housing 111 so as to be rotatable around the rotation axis Ax1. The input part 103 is mounted on the cam 41 of the wave generator 4 and rotates together with the cam 41 around the rotation axis Ax1. That is, the input part 103 transmits the power (rotational force) generated by the drive source 101 as input to the cam 41. As described above, in this embodiment, the rotation axis Ax1 on the input side and the rotation axis Ax2 on the output side are located on the same straight line, so the input part 103 and the output part 102 are located on the same axis.

[0096] The input side housing 111 holds the input unit 103 rotatably via the input side bearings 118 and 119. The pair of input side bearings 118 and 119 are arranged side by side with a gap along the rotation axis Ax1. In this embodiment, the shaft of the input unit 103 passes through the input side housing 111, and the front end of the input unit 103 extends from the end face ( Figure 4 The gap between the input side end surface of the input side housing 111 and the input portion 103 is blocked by the input side oil seal 120.

[0097] The output side housing 112 holds the output portion 102 rotatably via the output side bearings 121 and 122. The pair of output side bearings 121 and 122 are arranged in a spaced relationship along the rotation axis Ax2. In this embodiment, the shaft of the output portion 102 passes through the output side housing 112, and the front end of the output portion 102 extends from the end face ( Figure 4The gap between the output side end surface of the output side housing 112 and the output portion 102 is blocked by an output side oil seal 123.

[0098] Here, if Figure 4 As shown, the input-side housing 111 and the output-side housing 112 are joined together, sandwiching the rigid internal gear 2 of the wave gear device 1 from both sides parallel to the rotation axis Ax1. Specifically, the input-side housing 111 contacts the rigid internal gear 2 from the input side of the rotation axis Ax1, while the output-side housing 112 contacts the rigid internal gear 2 from the output side of the rotation axis Ax1. Thus, with the rigid internal gear 2 sandwiched between the input-side housing 111 and the output-side housing 112, screws (bolts) are inserted through a plurality of fixing holes 22 to secure the input-side housing 111 and the output-side housing 112. Thus, the input-side housing 111, the output-side housing 112, and the rigid internal gear 2 are joined together to form a single unit. In other words, the rigid internal gear 2, together with the input-side housing 111 and the output-side housing 112, forms the outer contour of the actuator 100.

[0099] The spline bushing 113 is a cylindrical component used to connect the shaft of the input unit 103 to the cam 41. The spline bushing 113 is inserted into the cam hole 43 formed in the cam 41, and the shaft of the input unit 103 is inserted into the spline bushing 113 so as to pass through the spline bushing 113. Here, the movement of the spline bushing 113 relative to both the cam 41 and the input unit 103 in the rotation direction centered on the rotation axis Ax1 is restricted. The spline bushing 113 is at least movable relative to the input unit 103 in a direction parallel to the rotation axis Ax1. This enables a spline connection structure to be used as the connection structure between the input unit 103 and the cam 41. As a result, the cam 41 can move relative to the input unit 103 along the rotation axis Ax1 and rotate together with the input unit 103 about the rotation axis Ax1.

[0100] In this embodiment, the spline bushing 113 connects not only the shaft of the input portion 103 to the cam 41 but also to the cover member 5. Therefore, the spline bushing 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 bushing 113 relative to both the cover member 5 and the input portion 103 in the rotational direction centered on the rotation axis Ax1 is restricted. However, the spline bushing 113 is movable at least relative to the input portion 103 in a direction parallel to the rotation axis Ax1. This achieves a spline connection structure for connecting the input portion 103 to the cover member 5. Consequently, the cover member 5 can move relative to the input portion 103 along the rotation axis Ax1 and rotate together with the input portion 103 about the rotation axis Ax1.

[0101] The spacer 114 fills the gap between the spline bushing 113 and the cam 41. The first stopper 115 prevents the spline bushing 113 from falling off the cam 41 and the cover member 5. The first stopper 115 comprises, 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 rotation axis Ax1. The second stopper 116 prevents the input portion 103 from falling off the spline bushing 113. The second stopper 116 comprises, for example, an E-ring and is attached to the input portion 103 so as to contact the spline bushing 113 from the output side of the rotation axis Ax1.

[0102] The mounting plate 117 is used to attach the shaft, which serves as the output portion 102, to the base 322 of the flexible externally gear 3. Specifically, with the area surrounding the through-hole 34 in the base 322 sandwiched between the mounting plate 117 and the flange of the output portion 102, screws (bolts) are inserted through the multiple mounting holes 33 to secure the mounting plate 117 to the flange. This secures the shaft, which serves as the output portion 102, to the base 322 of the flexible externally gear 3.

[0103] (3.3) Cover member

[0104] Next, regarding the structure of the cover member 5 (cover body 10) of the harmonic gear device 1 according to this embodiment, refer to Figures 1A to 3B Provide a more detailed explanation.

[0105] The cover member 5 is a plate-shaped component that covers the bearing 42 from one side (the input side) of the rotation axis Ax1. The cover member 5 is a non-circular component (here, an elliptical shape). At least the outer peripheral surface of the cover member 5 is composed of a metal plate that is elliptical in a 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 smaller (thinner) than the thickness of the rigid internal gear 2. Therefore, the cover member 5 has a higher rigidity than the flexible external gear 3 and a lower rigidity than the rigid internal gear 2.

[0106] The cover member 5 has a base 51 and an umbrella portion 52. When viewed from one side (input side) of the rotation axis Ax1, the base 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 periphery of the cover member 5. In other words, the base 51 is located on the inner side of the umbrella portion 52. In the present embodiment, when viewed from one side (input side) of the rotation axis Ax1, at least the outer periphery of the umbrella portion 52 is also formed into an elliptical shape. In the present embodiment, the outer periphery of the umbrella portion 52 and the outer periphery of the base 51 are both similar to the outer periphery of the cam 41. In addition, the base 51 and the umbrella portion 52 are formed integrally by a metal member, thereby enabling a seamless cover member 5 to be realized.

[0107] The cover member 5 is arranged to face at least the bearing 42 from the input side of the rotation axis Ax1, so that the cover member 5 covers the bearing 42 from the input side of the rotation axis Ax1. In other words, the cover member 5 and the wave generator 4 are combined so that they overlap with the input side of the wave generator 4 from the rotation axis Ax1. In this embodiment, in a direction parallel to the rotation axis Ax1, the cover member 5 and the wave generator 4 are combined so that most of the cover member 5 is accommodated between the two surfaces in the thickness direction of the rigid internal gear 2. Figure 1A As shown, only a portion 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. This prevents foreign matter X1 from entering the inner side of the outer ring 421 from one side (the input side) of the rotation axis Ax1. However, the cover member 5 is positioned opposite the bearing 42, ensuring a gap G1 greater than a certain value between the cover member 5 and the outer ring 421. Therefore, the cover member 5 does not contact the outer ring 421.

[0108] In this embodiment, the cover member 5 has a shape and size that covers at least the entire wave generator 4 when viewed from one side of the rotation axis Ax1. Furthermore, the cover member 5 has the same outer peripheral shape as the flexible external gear 3. Therefore, Figure 2B As shown, when viewed from the input side of the rotation axis Ax1 , the cover member 5 covers not only the bearing 42 but also the entire wave generator 4 including the cam 41 , and further covers the flexible externally gear 3 .

[0109] Thus, when viewed from one side of the rotation axis Ax1, the cover member 5 has a non-circular portion corresponding to the cam 41 at a portion opposite to the bearing 42. In this embodiment, when viewed from one side of the rotation axis Ax1, the entire cover member 5 composed of the base portion 51 and the umbrella portion 52 has a non-circular shape (here, an elliptical shape) similar to the cam 41. Therefore, when viewed from the input side of the rotation axis Ax1, although the cover member 5 covers the entire wave generator 4, it is almost not exposed from the wave generator 4. Furthermore, the wave generator 4 will not be exposed from the cover member 5. In other words, Figure 2B As shown, when viewed from one side of the rotation axis Ax1, the cover member 5 and the wave generator 4 (the cam 41 and the bearing 42) have elliptical shapes similar to each other and having their major axes in the same direction.

[0110] As described above, in this embodiment, the cover member 5 is coupled to the shaft serving as the input portion 103 via the spline bushing 113. Therefore, a cover hole 53 for attaching the shaft serving as the input portion 103 is formed in the center of the base portion 51. When viewed from one side (the input side) of the rotation axis Ax1, the cover hole 53 has the same shape as the cam hole 43 of the cam 41.

[0111] In this embodiment, the cover member 5 rotates at the same speed as the cam 41. That is, the cover member 5 and the cam 41 rotate relative to the rigid internal gear 2 together. Therefore, when viewed from the input side of the rotation axis Ax1, when the cam 41 rotates one full rotation (360 degrees) clockwise around the rotation axis Ax1, the cover member 5 also rotates one full rotation (360 degrees) clockwise around the rotation axis Ax1. As described above, in this embodiment, a spline connection structure can be used as the connection structure between the input portion 103, the cam 41, and the cover member 5, thereby allowing the cover member 5 and the cam 41 to rotate at the same speed. Furthermore, by rotating the cover member 5 and the cam 41 at the same speed, when viewed from one side of the rotation axis Ax1, the cover member 5 and the wave generator 4 (cam 41 and bearing 42) maintain an elliptical shape that is similar to each other and has its major axis in the same direction.

[0112] Next, the shape of the base 51 will be described in more detail. The base 51 has a recessed portion 511 on the outer periphery of the surface on the output side of the rotation axis Ax1. Figure 3A As shown, the recessed portion 511 is formed at the outer periphery of the base 51, forming a step such that the surface on the output side of the rotation axis Ax1 is recessed. The recessed portion 511 is formed on the entire circumference of the base 51. Here, the side surface and the bottom surface of the recessed portion 511 are orthogonal to each other. Therefore, as shown in FIG. Figure 1B As shown, an “interior angle” that is a right angle when viewed in cross section is formed in the recessed portion 511 .

[0113] The base 51 is combined with the wave generator 4 in such a manner that the corner of the outer ring 421 of the bearing 42 is accommodated in the recessed portion 511. Figure 1B As shown, the recessed portion 511 of the base 51 accommodates the inner corner of the end surface of the outer ring 421 on the input side of the rotation axis Ax1. In this embodiment, the gap G1 between the cover member 5 and the outer ring 421 of the bearing 42 is minimized within the recessed portion 511. However, the cover member 5 faces the bearing 42 while maintaining the gap G1 between the cover member 5 and the outer ring 421 of the bearing 42. Even within the recessed portion 511, the cover member 5 does not contact the outer ring 421. Specifically, a gap G11 in the radial direction (orthogonal to the rotation axis Ax1) exists between the side surface of the recessed portion 511 and the inner circumferential surface 424 of the outer ring 421. Furthermore, a gap G12 in the axial direction (parallel to the rotation axis Ax1) exists between the bottom surface of the recessed portion 511 and the end surface of the outer ring 421 on the input side of the rotation axis Ax1. The gap G1 between the cover member 5 and the outer ring 421 includes a gap G11 and a gap G12 .

[0114] The gaps G11 and G12 are both set to a size that does not interfere with each other even when processing errors and assembly errors of the components are taken into account, and are set to 0.05 mm to 1.0 mm as an example. More preferably, the gaps G11 and G12 are both 0.1 mm to 0.5 mm.

[0115] Furthermore, the recessed portion 511 is formed along the entire circumference of the base portion 51. Furthermore, in this 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 described above is maintained along the entire circumference of the outer ring 421. In other words, the gap G1 is maintained substantially uniformly along the circumference of the outer ring 421.

[0116] In addition, the base portion 51 has a constricted portion 512 in a region inside the recessed portion 511 on the surface on the output side of the rotation axis Ax1. Figure 3A As shown, the constricted portion 512 is formed by recessing the surface of the base 51, excluding the central portion, on the output side of the rotation axis Ax1. This makes the thickness of the base 51 smaller (thinner) than the central portion of the base 51. The constricted portion 512 is formed along the entire circumference of the base 51. The constricted portion 512 ensures the rigidity required for the cover member 5 while also reducing the weight of the cover member 5.

[0117] Furthermore, the base 51 has a recess 513 in an annular region around the cover hole 53 on the surface on the input side of the rotation axis Ax1. Figure 3B As shown, recessed portion 513 is formed by recessing the surface of base portion 51, excluding the central portion, on the input side of rotation axis Ax1. This allows base portion 51 to be thinner than the central portion. Recessed portion 513 is formed along the entire circumference of base portion 51. Recessed portion 513 ensures the required rigidity of cover member 5 while reducing its weight.

[0118] Next, the shape of the umbrella portion 52 will be described in further detail. Figure 1B As shown, 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. In other words, the umbrella portion 52 has an outer peripheral surface 521 that is inclined with respect to the rotation axis Ax1 so that the distance (radius) from the rotation axis Ax1 gradually increases as the distance from the bearing 42 increases. Figure 1B As shown in FIG. 1 , the umbrella portion 52 has a triangular shape in a cross-sectional view. The umbrella portion 52 is formed over the entire circumference of the cover member 5 in the circumferential direction.

[0119] The cover member 5 is constructed so that a predetermined clearance is maintained between the outer ring 421 of the bearing 42, and further between the flexible external gear 3 and the rigid internal gear 2, even at the bevel portion 52. The guide portion 23 provided on the rigid internal gear 2 has the narrowest clearance between the outer ring 421, the flexible external gear 3, and the rigid internal gear 2 and the bevel portion 52. The guide portion 23 faces the bevel portion 52 with a predetermined distance therebetween. Figure 1B As shown, the guide portion 23 is a portion that protrudes from the end surface on the input side of the rotation axis Ax1 in the internal teeth 21 of the rigid internal gear 2 toward the input side of the rotation axis Ax1.

[0120] The guide portion 23 has an inclined surface 231 that is inclined relative to the rotation axis Ax1 so that the 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. As a result, the umbrella portion 52 can narrow the gap with the rigid internal gear 2 in the guide portion 23 while ensuring a certain gap between the umbrella portion 52 and the rigid internal gear 2. The gap (interval) between the umbrella portion 52 and the guide portion 23 is set to a size that does not cause interference even when considering the processing errors and assembly errors of each component. As an example, it is set to a size of not less than 0.05 mm and not more than 1.0 mm. The gap (interval) between the umbrella portion 52 and the guide portion 23 is more preferably not less than 0.1 mm and not more than 0.5 mm. In this embodiment, the guide portion 23 and the rigid internal gear 2 are formed integrally by a single metal member.

[0121] However, in this embodiment, the cover member 5 is configured to prevent the liquid from passing through (i.e., to prevent the liquid from passing through). In other words, the liquid is shielded by the cover member 5 and does not penetrate the cover member 5. The "liquid" in the embodiment of the present disclosure refers to a substance containing a liquid or gel state. The "gel state" mentioned here refers to a state with intermediate properties between a liquid and a solid, and contains a colloid state consisting of two phases, a liquid phase and a solid phase. For example, states such as an emulsion (emulsion) in which the dispersion medium is a liquid phase and the dispersed substance is a liquid phase, and a suspension (suspension) in which the dispersed substance is a solid phase, which are called gel (gel) or sol (sol) are included in the "gel state". In addition, a state in which the dispersion medium is a solid phase and the dispersed substance is a liquid phase is also included in the "gel state". That is, if the temperature and pressure of the liquid shielded by the cover member 5 are constant, then the volume is also constant, and it is an object with the properties of a fluid that does not have a definite shape. In other words, the liquid shielded by the cover member 5 is a fluid (fluid) other than a gas. The "fluid" mentioned here includes both Newtonian fluids and non-Newtonian fluids.

[0122] In the harmonic gear device 1, for example, a liquid or gel lubricant 54 ( Figure 5A Since the lubricant 54 is liquid, the cover member 5 at least shields the lubricant 54. Therefore, the lubricant 54 is unlikely to penetrate into the cover member 5.

[0123] In addition, in the present embodiment, the cover member 5 is oleophobic. Although the cover member 5 may also be oleophobic as a whole, it is sufficient for at least a part to be oleophobic. In the present embodiment, an oleophobic coating based on, for example, a fluoride is locally applied to the cover member 5, so that the portion of the cover member 5 coated with the oleophobic coating is oleophobic. Specifically, the outer peripheral surface 521 of the umbrella portion 52 in the cover member 5 is oleophobic. As an example, when lubricating oil (oil) as a lubricant 54 is attached to the oleophobic portion of the cover member 5, the static contact angle of the cover member 5 with respect to the droplets of the lubricant 54, that is, the oil contact angle of the cover member 5 is preferably greater than 25 degrees. The "oil contact angle" mentioned here refers to the contact angle with respect to oil, that is, the angle formed by the oil droplet and the solid surface when the oil droplet containing the lubricant 54 (lubricating oil) is attached to the solid surface (the surface of the oleophobic portion of the cover member 5).

[0124] (4) Function

[0125] Next, regarding the operation of the harmonic gear device 1 according to this embodiment, refer to Figure 5A and Figure 5B Provide explanation.

[0126] Figure 5A and Figure 5B yes Figure 1B An enlarged view of the surrounding area of ​​the umbrella portion 52 of the cover member 5. Figure 5A and Figure 5B In order to explain the function of the cover member 5, although the cover member 5 is used to block the foreign matter X1 entering the inner side of the outer ring 421, it does not mean that the foreign matter X1 is included in the components of the harmonic gear device 1. Figure 5A and Figure 5B In the figure, the lubricant 54 held between the outer ring 421 and the cover member 5 is shown, but the shape and amount of the lubricant 54 are not necessarily limited to the form shown in the figure.

[0127] In addition, Figure 5A and Figure 5BWhile lubricant 54 is shown retained between outer ring 421 and cover member 5, the shape and amount of lubricant 54 are not necessarily limited to the illustrated form. Thus, cover member 5 prevents foreign matter X1 from entering the inner side of outer ring 421 from one side (the input side) of rotation axis Ax1. Therefore, even if foreign matter X1, such as metal powder or nitride, is generated by wear between inner teeth 21 and outer teeth 31, it is unlikely to enter the inner side of outer ring 421 (between outer ring 421 and inner ring 422).

[0128] In particular, in the wave gear device 1, power transmission due to the meshing of the internal teeth 21 and the external teeth 31 involves sliding in both the tooth profile and tooth trace directions, making it susceptible to the generation of foreign matter X1 due to wear. Furthermore, although lubricant 54 is employed, the flow rate of lubricant 54 is relatively low within the speed range used by the wave gear device 1, making it difficult to expect any foreign matter X1 to be effectively washed away by the lubricant 54. If such foreign matter X1 enters the bearing 42, it could damage the surfaces of any of the outer ring 421, inner ring 422, or rolling elements 423 of the bearing 42, thereby affecting the reliability of the wave gear device 1. Specifically, if foreign matter X1 enters between the outer ring 421 and inner ring 422 of the bearing 42, the rolling elements 423 may bite into the foreign matter X1, potentially damaging the surfaces of any of the outer ring 421, inner ring 422, or rolling elements 423. The wave gear device 1 according to the present embodiment prevents the foreign matter X1 from entering the bearing 42 by the cover member 5 , and thus does not cause a decrease in reliability.

[0129] For example, if the inner circumferential surface (rolling surface) of the outer ring 421 peels off due to the penetration of foreign matter X1, the function of the bearing 42 may be impaired, causing a malfunction in the operation of the wave gear device 1. In the wave gear device 1 according to this embodiment, the cover member 5 can significantly reduce the penetration of foreign matter X1 into the bearing 42, thereby improving the reliability of the wave gear device 1. In particular, this prevents a decrease in reliability even during long-term use, thereby achieving a longer life and higher performance of the wave gear device 1.

[0130] Furthermore, the cover member 5 maintains a gap G1 greater than a certain value between itself and the outer ring 421 of the bearing 42, preventing contact with the outer ring 421. Therefore, even when the wave gear device 1 is driven, even if relative movement occurs between the cover member 5 and the outer ring 421 of the bearing 42, frictional resistance between the cover member 5 and the outer ring 421 and wear of the cover member 5 or the outer ring 421 are unlikely to occur. Specifically, in this embodiment, the cover member 5 rotates with the cam 41, and the outer ring 421 rotates with the flexible externally toothed gear 3. Therefore, relative rotation occurs between the cover member 5 and the outer ring 421 corresponding to the difference in rotational speed (reduction ratio) between the cam 41 and the flexible externally toothed gear 3. In this case, by maintaining a gap G1 between the cover member 5 and the outer ring 421, frictional resistance and wear of the cover member 5 or the outer ring 421 are unlikely to occur, minimizing any adverse effects on the operation of the wave gear device 1 due to the presence of the cover member 5.

[0131] The relative rotational speed between the cover member 5 and the outer ring 421 depends on the speed difference (reduction ratio) between the cam 41 and the flexible externally toothed gear 3. However, a higher reduction ratio increases the relative rotational speed between the cover member 5 and the outer ring 421. As a result, when frictional resistance occurs between the cover member 5 and the outer ring 421, the power transmission efficiency of the wave gear device 1 is significantly reduced, potentially also affecting starting performance in harsh environments such as cold regions. In the wave gear device 1 according to this embodiment, the gap G1 between the cover member 5 and the outer ring 421 mitigates problems caused by this frictional resistance, significantly improving the reliability of the wave gear device 1.

[0132] However, as described above, in the harmonic gear device 1 according to this embodiment, a liquid or gel lubricant 54 is injected into, for example, the meshing portion between the internal teeth 21 and the external teeth 31 and between the outer ring 421 and the inner ring 422 of the bearing 42. As an example, the lubricant 54 is a liquid lubricating oil (oil). Figure 5A and Figure 5B As shown, when the wave gear device 1 is used, the lubricant 54 penetrates between the outer ring 421 of the bearing 42 and the cover member 5. Specifically, the lubricant 54 is mixed into the gap G1 between the outer ring 421 and the cover member 5 (see Figure 1B ) and seals at least a portion of the gap G1. In short, in this embodiment, at least a portion of the gap G1 between the outer ring 421 and the cover member 5 is filled with the lubricant 54.

[0133] exist Figure 5A and Figure 5BIn the example of FIG, the lubricant 54 is filled in the entire gap G1 so as to fill both the radial gap G11 and the axial gap G12 between the outer ring 421 and the cover member 5. Furthermore, in this embodiment, the entire gap G1 formed along the entire circumference of the outer ring 421 is filled with the lubricant 54. With respect to the cover member 5, the input side ( Figure 5A The space on the right side of the rotation axis Ax1 ( Figure 5A The space on the left side of the cover member 5 (on the left side) can be connected by the gap G1. Thus, the gap G1, which forms a narrow path connecting the inside and outside of the cover member 5, is filled with lubricant 54. Therefore, the space on the input side of the rotation axis Ax1 and the space on the output side of the rotation axis Ax1 are shielded by the lubricant 54. This more reliably prevents foreign matter X1 from entering the inner side of the outer ring 421 from one side (the input side) of the rotation axis Ax1.

[0134] Here, lubricant 54 is retained in gap G1 between outer ring 421 and lid member 5 by capillary action. Specifically, gap G1 between outer ring 421 and lid member 5 is relatively narrow, and when gap G1 is filled with lubricant 54, lubricant 54 is retained within gap G1 by capillary action. Consequently, gap G1 is maintained filled with lubricant 54. The magnitude of the capillary action's retaining force also varies depending on the wettability of lubricant 54 with outer ring 421 and lid member 5. Therefore, at least the portion of lid member 5 facing gap G1, specifically the side surfaces and bottom surface of recessed portion 511, is preferably non-oleophobic.

[0135] Furthermore, in the wave gear device 1 according to this embodiment, since the cover member 5 includes the bevel portion 52, it can be expected that centrifugal force will be used to fling foreign matter X1 outward. Specifically, the bevel portion 52 is formed so that the distance from the rotation axis Ax1 gradually increases from the bearing 42 side toward the input side of the rotation axis Ax1. Therefore, even if foreign matter X1 such as metal powder or nitrides is generated due to wear between the internal teeth 21 and the external teeth 31 and adheres to the outer peripheral surface 521 of the bevel portion 52, the foreign matter X1 can be flung outward (toward the input side of the rotation axis Ax1).

[0136] 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 attached to the outer peripheral surface 521 of the umbrella portion 52. Figure 5A As shown, the foreign matter X1 attached to the outer peripheral surface 521 of the umbrella portion 52 moves along the outer peripheral surface 521 in a direction away from the rotation axis Ax1, that is, in the input side of the rotation axis Ax1. As a result, the foreign matter X1 moves away from the bearing 42, and finally Figure 5BAs shown, foreign matter X1 is ejected toward the input side of the cover member 5, closer to the rotation axis Ax1. At this point, the foreign matter X1 is ejected by passing between the outer peripheral surface 521 of the umbrella portion 52 and the inclined surface 231 of the guide portion 23. In other words, the gap between the umbrella portion 52 and the guide portion 23 forms a path for the foreign matter X1 to be ejected. This function of the umbrella portion 52 allows the generated foreign matter X1 to be ejected toward the outside of the cover member 5, thus preventing the foreign matter X1 from accumulating inside the cover member 5.

[0137] Furthermore, as described above, the outer peripheral surface 521 of the umbrella portion 52 of the cover member 5 has oleophobicity. Therefore, foreign matter X1 containing oil, such as that caused by the lubricant 54, is less likely to remain on the umbrella portion 52 and is easily thrown out of the cover member 5.

[0138] (5) Application examples

[0139] Next, for application examples of the harmonic gear device 1 and the actuator 100 according to this embodiment, refer to Figure 6 Provide explanation.

[0140] Figure 6 1 is a cross-sectional view showing an example of a robot 9 that adopts the wave gear device 1 according to the present embodiment. The robot 9 is a horizontal multi-joint robot, that is, a so-called SCARA (Selective Compliance Assembly Robot Arm) type robot.

[0141] like Figure 6 As shown, the robot 9 includes two harmonic gear devices 1 and a connecting rod 91. The two harmonic gear devices 1 are respectively provided at the joints of two locations of the robot 9. The connecting rod 91 connects the joints of the two locations. Figure 6 In the example, the harmonic gear device 1 is not a cup type, but a top hat type harmonic gear device. Figure 6 In the illustrated harmonic gear device 1, a flexible external gear 3 formed in a top hat shape is used. Figure 6 The cover member 5 is omitted in the figure.

[0142] (6) Modification

[0143] Implementation 1 is merely one of the various implementations of the embodiments of the present disclosure. Implementation 1 can be modified in various ways, depending on the design, etc., if it can achieve the objectives of the present disclosure. In addition, the figures referenced in the embodiments of the present disclosure are schematic diagrams, and the sizes and thickness ratios of the various structural elements in the figures are not necessarily limited to reflect actual dimensional ratios. The following lists variations of Implementation 1. The variations described below can be appropriately combined and applied.

[0144] The wave gear device 1 is not limited to the cup type described in the first embodiment, and may be, for example, a top hat type, a ring type, a differential type, a flat type (pancake type), or a shield type.

[0145] Furthermore, the cover member 5 can be positioned facing the bearing 42 from one side of the rotation axis Ax1, and does not need to be positioned on the input side of the rotation axis Ax1 relative to the bearing 42 as in the first embodiment. In other words, the cover member 5 can also be positioned facing the bearing 42 from the output side of the rotation axis Ax1. In this case, the cover member 5 prevents foreign matter X1 from entering the inner side of the outer ring 421 from the output side of the rotation axis Ax1.

[0146] Furthermore, the cover member 5 can be positioned so as to face the bearing 42 from one side of the rotation axis Ax1. Alternatively, a pair of cover members 5 may be positioned on the input and output sides of the rotation axis Ax1 relative to the bearing 42. In this case, the cover members 5 prevent foreign matter X1 from entering the inner side of the outer ring 421 from both the input and output sides of the rotation axis Ax1.

[0147] Furthermore, the structure of actuator 100 is not limited to that described in the first embodiment and can be modified as appropriate. For example, the connection structure between input portion 103, cam 41, and cover member 5 is not limited to a spline connection; a cross coupling, etc., can also be used. By using a cross coupling as the connection structure between input portion 103, cam 41, and cover member 5, eccentricity between the input-side rotation axis Ax1 and wave generator 4 (cam 41) can be offset, furthermore, eccentricity between the rigid internal gear 2 and the flexible external gear 3 can be offset. Furthermore, cam 41 and cover member 5 can also move along rotation axis Ax1 without moving relative to input portion 103.

[0148] Furthermore, the application examples of the harmonic gear device 1 and actuator 100 of this embodiment are not limited to the horizontal multi-joint robot described above. For example, industrial robots other than horizontal multi-joint robots or robots for non-industrial applications may also be used. For example, industrial robots other than horizontal multi-joint robots include vertical multi-joint robots and parallel link robots. For example, robots for non-industrial applications include household robots, nursing robots, and medical robots.

[0149] The bearing 42 is not limited to a deep groove ball bearing, and may be, for example, a thrust angular contact ball bearing, etc. Furthermore, the bearing 42 is not limited to a ball bearing, and may be, for example, 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 composed of "rollers" other than balls.

[0150] Furthermore, the material of each component of the wave gear device 1 or the actuator 100 is not limited to metal, and may be, for example, a resin such as engineering plastic.

[0151] Furthermore, it is not essential for the wave gear device 1 to have the cover member 5 and the cam 41 rotate at the same speed. For example, the cover member 5 may not rotate relative to the rigid internal gear 2 .

[0152] Furthermore, the guide portion 23 only needs to be provided on the rigid internal gear 2, and forming the guide portion 2 integrally with the rigid internal gear 2 using a single metal component is not a necessary feature of the wave gear device 1. For example, the guide portion 23, a separate component from the rigid internal gear 2, can be fixed to the rigid internal gear 2 by welding or the like, thereby being provided on the rigid internal gear 2. Furthermore, a plate material can be fixed to the inner circumferential surface of the input-side housing 111 to which the rigid internal gear 2 is fixed, so that the plate material functions as the guide portion 23.

[0153] The lubricant 54 is not limited to liquid substances such as lubricating oil (oil), but may be a gel substance such as grease.

[0154] (Implementation Method 2)

[0155] like Figure 7A and Figure 7B As shown, the structure of the cover member 5A of the strain wave gear device 1A according to this embodiment is different from that of the strain wave gear device 1 according to Embodiment 1. Hereinafter, the same components as those of Embodiment 1 are denoted by the same reference numerals and description thereof will be omitted as appropriate.

[0156] Figure 7A 1A is a cross-sectional view showing a schematic structure of a wave gear device 1A. Figure 7B yes Figure 7A The main part (equivalent to Figure 1A An enlarged view of the range of area Z1).

[0157] In this embodiment, the wave gear device 1A includes a pair of cover members 5A. One cover member 5A faces the bearing 42 from the input side of the rotation axis Ax1, while the other cover member 5A faces the bearing 42 from the output side of the rotation axis Ax1. In other words, the wave gear device 1A includes a pair of cover members 5A, which are disposed on the input and output sides of the rotation axis Ax1, respectively, relative to the bearing 42.

[0158] According to this structure, the bearing 42 is sandwiched by the pair of cover members 5A in a direction parallel to the rotation axis Ax1. Therefore, the pair of cover members 5A prevents foreign matter X1 from entering the inner side of the outer ring 421 from both sides of the rotation axis Ax1.

[0159] The shape of each cover member 5A is also different from that of the cover member 5 in Embodiment 1. In this embodiment, the pair of cover members 5A have symmetrical shapes in a direction parallel to the rotation axis Ax1, so the shape of one of the pair of cover members 5A will be described below.

[0160] That is, in this embodiment, if Figure 7B As shown, the cover member 5A has a base 51 and a convex portion 55. When viewed from one side (input side) of the rotation axis Ax1, the base 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 into an elliptical shape. In this embodiment, the outer peripheral shape of the convex portion 55 and the outer peripheral shape of the base 51 are both similar to the outer peripheral shape of the cam 41. In addition, the base 51 and the convex portion 55 are formed integrally by a metal part, thereby realizing a seamless cover member 5A.

[0161] The base 51 is positioned inside the flexible externally gear 3. A first gap G21 is formed between the outer circumferential surface 514 of the base 51 and the inner circumferential surface 301 of the flexible externally gear 3. The outer circumferential surface 514 of the base 51 and the inner circumferential surface 301 of the flexible externally gear 3 face each other in a direction perpendicular to the rotation axis Ax1. Specifically, when viewed from one side (the input side) of the rotation axis Ax1, the outer circumferential shape of the base 51 is slightly smaller than the inner circumferential surface 301 of the flexible externally gear 3. Therefore, the outer circumferential surface 514 of the base 51, positioned inside the flexible externally gear 3, faces the flexible externally gear 3 while maintaining the first gap G21 between the outer circumferential surface 514 and the inner circumferential surface 301 of the flexible externally gear 3, without contacting the flexible externally gear 3. More specifically, a first gap G21 exists in the radial direction (perpendicular to the rotation axis Ax1) between the outer circumferential surface 514 of the base 51 and the inner circumferential surface 301 of the flexible externally gear 3.

[0162] The protrusion 55 protrudes from the base 51 and is inserted into the inner side of the outer ring 421. A second gap G22 is formed between the outer circumferential surface 551 of the protrusion 55 and the inner circumferential surface 424 of the outer ring 421. The outer circumferential surface 551 of the protrusion 55 and the inner circumferential surface 424 of the outer ring 421 face each other in a direction perpendicular to the rotation axis Ax1. Specifically, when viewed from one side (the input side) of the rotation axis Ax1, the outer circumferential shape of the protrusion 55 is slightly smaller than the inner circumferential surface 424 of the outer ring 421. Therefore, the outer circumferential surface 551 of the protrusion 55, located on the inner side of the outer ring 421, faces the outer ring 421 while maintaining the second gap G22 between the outer circumferential surface 424 and the outer ring 421, without contacting the outer ring 421. More specifically, a second gap G22 exists in the radial direction (a direction perpendicular to the rotation axis Ax1 ) between the outer peripheral surface 551 of the protrusion 55 and the inner peripheral surface 424 of the outer ring 421 .

[0163] In addition, a third gap G23 is formed between the base 51 and the outer ring 421, and the base 51 and the outer ring 421 are opposite to each other in the direction of the rotation axis Ax1. The first gap G21 and the second gap G22 are connected by the third gap G23. That is, the base 51 is opposite to the outer ring 421 while ensuring the third gap G23 between the end face 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 (a direction parallel to the rotation axis Ax1) exists between the base 51 and the outer ring 421. And, as Figure 7B As shown, the first gap G21 and the second gap G22 in the radial direction are connected by the third gap G23. The gap G2 between the cover member 5A and the outer ring 421 and the flexible external gear 3 includes the first gap G21, the second gap G22, and the third gap G23.

[0164] The first gap G21, the second gap G22, and the third gap G23 are each set to a size that does not cause interference even when considering machining errors and assembly errors of the various components. As an example, they are set to a size of 0.05 mm to 1.0 mm. More preferably, the first gap G21, the second gap G22, and the third gap G23 are each set to a size of 0.1 mm to 0.5 mm.

[0165] That is, a crankshaft-shaped gap G2 is formed between the cover member 5A, the outer ring 421, and the flexible external gear 3 by the first gap G21, the second gap G22, and the third gap G23. Figure 7A The space on the right side of the rotation axis Ax1 ( Figure 7A The space on the left side of the cover member 5A can be connected by the gap G2. In this way, the gap G2, which forms a narrow path connecting the inside and outside of the cover member 5A, improves the sealing performance based on the cover member 5A by adopting the labyrinth structure formed as described above. As a result, it is possible to more reliably prevent foreign matter X1 from entering the inner side of the outer ring 421 from one side (input side or output side) of the rotation axis Ax1. Moreover, with regard to the third gap G23 in the axial direction, in particular, it is maintained at a constant minimum gap regardless of the elastic deformation of the outer ring 421 and the flexible external gear 3, thereby easily preventing foreign matter X1 from passing through the gap G2. With regard to the first gap G21 and the second gap G22 in the radial direction, they are also able to maintain a constant minimum gap regardless of the elastic deformation of the outer ring 421 and the flexible external gear 3, thereby preventing foreign matter X1 from passing through the gap G2.

[0166] Furthermore, in this embodiment, the cover member 5A has a constricted portion 515 in the area surrounding the cover hole 53 (see FIG. Figure 10AAs shown in Figure 7, the constricted portion 515 is a portion of the cover member 5A that is thinner (thinner) than the center portion of the cover member 5A by recessing both surfaces in the thickness direction (parallel to the rotation axis Ax1). The constricted portion 515 is formed along the entire circumference of the cover member 5A. This constricted portion 515 ensures the required rigidity of the cover member 5A while also reducing its weight.

[0167] In addition, in this embodiment as well, it is preferable that the gap G2 is filled with the lubricant 54 .

[0168] Figure 8A 1 is a cross-sectional view showing a schematic structure of a wave gear device 1B according to a first modified example of the second embodiment. Figure 8B yes Figure 8A The main part (equivalent to Figure 1A (enlarged view of the region Z1). In a first modified example of the second embodiment, a wave gear device 1B employs the cover member 5 described in the first embodiment, replacing the cover member 5A of the pair of cover members 5A described in the second embodiment that faces the bearing 42 from the input side of the rotation axis Ax1. In this configuration, the cover member 5 that faces the bearing 42 from the input side of the rotation axis Ax1 can eject any foreign matter X1 that is generated toward the outside of the cover member 5 through the function of the umbrella portion 52, thereby preventing the foreign matter X1 from accumulating inside the cover member 5.

[0169] Figure 9A 1 is a cross-sectional view showing a schematic structure of a wave gear device 1C according to a second modification of the second embodiment. Figure 9B yes Figure 9A The main part (equivalent to Figure 1A An enlarged view of the region Z1 (see FIG. 2 ) is provided. In a second modified example of the second embodiment, a wave gearing device 1C employs a cover member 5C having a different shape, replacing the cover member 5A of the pair of cover members 5A described in the second embodiment that faces the bearing 42 from the input side of the rotation axis Ax1. In addition to having the same base portion 51 and convex portion 55 as the cover member 5A, the cover member 5C also has an umbrella portion 52.

[0170] like Figure 9BAs shown, the umbrella portion 52 of the cover member 5C protrudes from the surface on the side opposite to the bearing 42 in the thickness direction of the base 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 (the input side) of the rotation axis Ax1. In other words, the umbrella portion 52 has an outer peripheral surface 521 that is inclined relative to the rotation axis Ax1 in such a manner that the distance (radius) from the rotation axis Ax1 gradually increases as it moves away from the bearing 42. This umbrella portion 52 is formed over the entire circumference of the cover member 5. In this structure, for the cover member 5C that faces the bearing 42 on the input side of the rotation axis Ax1, it can throw out any foreign matter X1 that is generated toward the outside of the cover member 5C through the function of the umbrella portion 52, so that the foreign matter X1 is less likely to accumulate inside the cover member 5C.

[0171] Figure 10A 、 Figure 10B and Figure 10C These are cross-sectional views of main parts schematically illustrating the configurations of wave gear devices 1D, 1E, and 1F according to third, fourth, and fifth modifications of the second embodiment, respectively.

[0172] like Figure 10A As shown, in the third modified example of the second embodiment, the shape of the cover member 5D differs from the cover member 5A described in the second embodiment. In the cover member 5D, a groove 56 is provided in place of the protrusion 55 at a portion of the surface of the base 51 that faces the outer ring 421. The groove 56 is formed along the entire circumference of the base 51. Furthermore, the outer ring 421 has a rib 425 that protrudes from the end surface in the direction of the rotation axis Ax1. The rib 425 is formed along the entire circumference of the outer ring 421. The rib 425 is inserted into the groove 56. A gap G3 is thus defined between the cover member 5D and the outer ring 421, including between the rib 425 and the groove 56. This gap G3 forms a labyrinthine structure, similar to the gap G2 described above, formed by the rib 425 and the groove 56. This improves the sealing performance of the cover member 5D.

[0173] like Figure 10BAs shown, in the wave gear device 1E according to the fourth modified example of the second embodiment, the shape of the cover member 5E differs from that of the cover member 5A described in the second embodiment. In the cover member 5E, the base 51 itself is positioned inside the outer ring 421. Specifically, when viewed from one side (the input side) of the rotation axis Ax1, the outer circumference of the base 51 is an elliptical shape slightly smaller than the inner circumferential surface 424 of the outer ring 421. Here, the cover member 5E has a rib 57 protruding from the outer circumferential surface 514 of the base 51. The rib 57 is formed along the entire circumference of the base 51. Furthermore, the outer ring 421 has a groove 426 on its inner circumferential surface. The groove 426 is formed along the entire circumference of the outer ring 421. The rib 57 is inserted into the groove 426. A gap G4 is maintained between the cover member 5E and the outer ring 421, including between the rib 57 and the groove 426. The gap G4 forms a labyrinth structure similar to the gap G2 by integrating the ribs 57 and the grooves 426 , thereby improving the sealing performance of the cover member 5E. Furthermore, the gap G4 is filled with a lubricant 54 .

[0174] like Figure 10C As shown, in the fifth modified example of the second embodiment, the shape of the cover member 5F differs from that of the cover member 5E of the fourth modified example of the second embodiment. The cover member 5F has a rib 58 protruding from the outer circumferential surface 514 of the base 51. The outer circumferential 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 along the entire circumference of the base 51. Furthermore, the outer ring 421 has a groove 427 on its inner circumferential surface. The groove 427 is formed along the entire circumference of the outer ring 421. The inner diameter of the outer ring 421 differs between the inner and outer sides of the groove 427, with the outer side of the groove 427 being larger. The rib 58 faces the groove 427. A gap G5 is maintained between the cover member 5F and the outer ring 421, including between the rib 58 and the groove 427. The gap G5 forms a labyrinth structure similar to the gap G2 by integrating the ribs 58 and the grooves 427 , thereby improving the sealing performance of the cover member 5F. Furthermore, the gap G5 is filled with a lubricant 54 .

[0175] Furthermore, the various cover members 5A to 5F described in the second embodiment do not need to be provided in pairs, and only one cover member may be provided so as to face the bearing 42 from one side of the rotation axis Ax1.

[0176] The structure (including modified examples) of the second embodiment can be applied in combination with the structure (including modified examples) described in the first embodiment as appropriate.

[0177] (Implementation Method 3)

[0178] like Figure 11A and Figure 11BAs shown, the structure of the cover member 5G of the strain wave gear device 1G according to this embodiment is different from that of the strain wave gear device 1A according to Embodiment 2. Hereinafter, the same components as those of Embodiment 2 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

[0179] Figure 11A 1G is a cross-sectional view showing a schematic structure of a wave gear device 1G. Figure 11B yes Figure 11A The main part (equivalent to Figure 1A An enlarged view of the range of area Z1).

[0180] In the present embodiment, the pair of cover members 5G have symmetrical structures in a direction parallel to the rotation axis Ax1 , and therefore, the shape of one of the pair of cover members 5G will be described below.

[0181] That is, in this embodiment, the cover member 5G faces only the bearing 42 of the wave generator 4 from one side of the rotation axis Ax1. In other words, the cover member 5G is a member formed in the same annular shape as the bearing 42. The cover member 5G is fixed to the inner ring 422 of the bearing 42.

[0182] Specifically, the cover member 5G includes a main plate 501, a first side plate 502, and a second side plate 503. When viewed from one side of the rotation axis Ax1, the main plate 501 is a plate-shaped component formed in an annular shape. The first side plate 502 protrudes from the inner peripheral edge of the main plate 501 along the rotation axis Ax1 toward the bearing 42 side. The second side plate 503 protrudes from the outer peripheral edge of the main plate 501 along the rotation axis Ax1 toward the bearing 42 side. In other words, the first side plate 502 and the second side plate 503 are opposite to each other in the radial direction and are connected by the main plate 501. The main plate 501, the first side plate 502, and the second side plate 503 are formed integrally by a metal component, thereby realizing a seamless cover member 5G.

[0183] The cover member 5G has flexibility due to its relatively small thickness (thinness). Therefore, when the inner ring 422 elastically deforms while the cover member 5G is fixed to the inner ring 422, the cover member 5G also elastically deforms along with the deformation of the inner ring 422.

[0184] Here, the main plate 501 faces the bearing 42 with a gap between it and the end face of the bearing 42, from one side of the rotation axis Ax1. Furthermore, the first side plate 502 is press-fitted into the gap between the inner ring 422 and the cam 41, and the cover member 5G is secured to the inner ring 422 via the first side plate 502. Meanwhile, the second side plate 503 is inserted into the gap between the outer ring 421 and the flexible externally gear 3, but a gap G6 is maintained between the outer ring 421 and the flexible externally gear 3 within the second side plate 503.

[0185] With the above configuration, the cover member 5G faces the bearing 42 with a gap G6 maintained between it and the outer ring 421 of the bearing 42. The cover member 5G also has the 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.

[0186] In addition, the cover members 5G described in the third embodiment do not need to be provided in pairs, and only one cover member 5G may be provided so as to face the bearing 42 from one side of the rotation axis Ax1.

[0187] The structure (including modified examples) of the third embodiment can be applied in combination with the structure (including modified examples) described in the first embodiment or the second embodiment as appropriate.

[0188] (Summarize)

[0189] As shown above, the harmonic gear device (1, 1A to 1G) involved in the first embodiment includes: an annular rigid internal gear (2) having internal teeth (21); an annular flexible external gear (3) having external teeth (31) and arranged on the inner side of the rigid internal gear (2); and a wave generator (4). The wave generator (4) is arranged on the inner side of the flexible external gear (3) and causes the flexible external gear (3) to bend. The harmonic gear device (1, 1A to 1G) deforms the flexible external gear (3) as the wave generator (4) rotates around the rotation axis (Ax1), causing a portion of the external teeth (31) to mesh with a portion of the internal teeth (21), thereby causing the flexible external gear (3) to rotate relative to the rigid internal gear (2) according to the difference in the number of teeth with the rigid internal gear (2). The wave generator (4) includes: a non-circular cam (41) driven to rotate around a rotating shaft (Ax1); and a bearing (42) disposed between an outer peripheral surface (411) of the cam (41) and an inner peripheral surface (301) of a flexible external gear (3). The harmonic gear device (1, 1A to 1G) further includes a cover member (5, 5A to 5G) disposed so as to face the bearing (42) from one side of the rotating shaft (Ax1). The cover member (5, 5A to 5G) faces the bearing (42) while ensuring a gap (G1 to G6) between the cover member and the outer ring (421) of the bearing (42), thereby preventing foreign matter (X1) from entering the inner side of the outer ring (421) from one side of the rotating shaft (Ax1).

[0190] According to this method, even if foreign matter (X1) is generated due to wear between the internal teeth (21) and the external teeth (31) caused by long-term use of the harmonic gear device (1, 1A to 1G), such foreign matter (X1) can be prevented from entering the bearing (42). Therefore, it has the advantage of high reliability.

[0191] According to the first aspect, in the wave gear device (1, 1A to 1G) according to the second aspect, the cover member (5, 5A to 5G) and the cam (41) rotate at the same speed.

[0192] According to this embodiment, even if the bearing (42) is elastically deformed, the cover member (5, 5A to 5G) can follow the elastic deformation of the bearing (42).

[0193] According to the second embodiment, in the harmonic gear device (1, 1A to 1G) involved in the third embodiment, the cover member (5, 5A to 5G) has an umbrella portion (52) formed so that the distance from the rotating axis (Ax1) gradually increases from the bearing (42) side toward one side of the rotating axis (Ax1).

[0194] According to this embodiment, the foreign matter (X1) attached to the umbrella portion (52) can be moved in a direction away from the bearing (42) by centrifugal force.

[0195] According to the third aspect, the harmonic gear device (1, 1A to 1G) according to the fourth aspect further includes a guide portion (23) provided on the rigid internal gear (2) and facing the bevel portion (52) with a gap greater than a certain value.

[0196] According to this embodiment, the movement of the foreign matter (X1) attached to the umbrella portion (52) can be guided by the centrifugal force.

[0197] According to any one of the first to fourth aspects, in the harmonic gear device (1, 1A to 1G) involved in 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 (Ax1) at a portion facing the bearing (42).

[0198] According to this embodiment, the amount of protrusion of the cover member (5, 5A to 5G) from the wave generator (4) can be suppressed to a relatively small level.

[0199] According to any one of the first to fifth aspects, in the sixth aspect of the harmonic gear device (1, 1A to 1G), at least a portion of the gap (G1 to G6) between the outer ring (421) and the cover member (5, 5A to 5G) is filled with a lubricant (54).

[0200] According to this embodiment, sealing using the lubricant (54) can be achieved.

[0201] According to the sixth aspect, in the wave gear device (1, 1A to 1G) according to the seventh aspect, the lubricant (54) is retained in the gaps (G1 to G6) between the outer ring (421) and the cover member (5, 5A to 5G) by a capillary phenomenon.

[0202] According to this embodiment, a member for retaining the lubricant (54) is unnecessary.

[0203] In the harmonic gear device (1, 1A to 1G) according to the eighth embodiment, the cover member (5, 5A to 5G) has a base (51) disposed inside the flexible external gear (3). A first gap (G21) is formed between an outer peripheral surface (514) of the base (51) and an inner peripheral surface (301) of the flexible external gear (3), which are opposed to each other in a direction perpendicular to the rotation axis (Ax1).

[0204] According to this method, a narrow path is formed by the first gap (G21), which easily prevents foreign matter (X1) from entering the inner side of the outer ring (421).

[0205] According to the eighth aspect, in the harmonic gear device (1, 1A to 1G) according to the ninth aspect, the cover member (5, 5A to 5G) further includes a protrusion (55) that protrudes from the base (51) and is inserted into the inner side of the outer ring (421). A second gap (G22) is formed between an outer peripheral surface (551) of the protrusion (55) and an inner peripheral surface (424) of the outer ring (421), which are opposed in a direction perpendicular to the rotation axis (Ax1).

[0206] According to this method, a narrow path is formed by the second gap (G22), which easily prevents foreign matter (X1) from entering the inner side of the outer ring (421).

[0207] According to the ninth aspect, in the wave gear device (1, 1A-1G) according to the tenth aspect, a third gap (G23) is formed between the base (51) and the outer ring (421) facing each other in the direction of the rotation axis (Ax1). The first gap (G21) and the second gap (G22) are connected by the third gap (G23).

[0208] According to this method, a narrow path is formed by the first gap (G21), the second gap (G22) and the third gap (G23), which easily prevents foreign matter (X1) from entering the inner side of the outer ring (421).

[0209] In the wave gear device (1, 1A to 1G) according to an eleventh aspect according to any one of the first to tenth aspects, the cover member (5, 5A to 5G) is configured to prevent passage of liquid.

[0210] According to this aspect, the cover member (5, 5A to 5G) can block the liquid.

[0211] In the wave gear device (1, 1A to 1G) according to a twelfth aspect according to any one of the first to eleventh aspects, the cover member (5, 5A to 5G) has oil repellency.

[0212] According to this embodiment, foreign matter (X1) containing oil is less likely to adhere to the cover member (5, 5A to 5G).

[0213] The actuator involved in the thirteenth embodiment includes: the harmonic gear device (1, 1A to 1G) involved in any one of the first to twelfth embodiments; a driving source (101) for rotating a cam (41); and an output portion (102) for outputting the rotational force of a flexible external gear (3).

[0214] According to this embodiment, there is an advantage in that a decrease in reliability is avoided and high reliability is achieved.

[0215] The cover body (10) according to the fourteenth aspect is used as a cover member (5, 5A to 5G) of the wave gear device (1, 1A to 1G) according to any one of the first to twelfth aspects.

[0216] According to this embodiment, there is an advantage in that a decrease in reliability is avoided and high reliability is achieved.

[0217] The configurations according to the second to twelfth aspects are not essential to the wave gear device (1, 1A to 1G) and can be omitted as appropriate.

[0218] Description of Reference Numerals

[0219] 1. 1A~1G harmonic gear device

[0220] 2 Rigid internal gear

[0221] 3 Flexible external gear

[0222] 4-wave generator

[0223] 5, 5A~5G cover components

[0224] 10 cover

[0225] 21 internal teeth

[0226] 23 Guidance Department

[0227] 31 external teeth

[0228] 41 Cam

[0229] 42 bearings

[0230] 51 base

[0231] 52 Umbrella Department

[0232] 54 Lubricant

[0233] 55 convex part

[0234] 100 actuators

[0235] 101 drive source

[0236] 102 output unit

[0237] 411 outer surface

[0238] 421 outer ring

[0239] Ax1 rotation axis

[0240] G1~G6 clearance

[0241] G21 Second Gap

[0242] G22 Second Gap

[0243] G23 third gap

[0244] X1 foreign body

[0245] Industrial Applicability

[0246] According to the embodiments of the present disclosure, it is possible to provide a harmonic gear device, an actuator, and a cover body that have high reliability.

Claims

1. A harmonic gear device, wherein: include: 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 is arranged on the inner side of the flexible external gear and causes the flexible external gear to bend. In the harmonic gear device, the flexible external gear is deformed as the wave generator rotates about the rotation axis, causing a portion of the external teeth to mesh with a portion of the internal teeth, thereby causing the flexible external gear to rotate relative to the rigid internal gear by a difference in the number of teeth between the flexible external gear and the rigid internal gear. The wave generator has: a non-circular cam driven to rotate about the rotation axis; and A bearing is disposed between the outer peripheral surface of the cam and the inner peripheral surface of the flexible external gear. The harmonic gear device further includes a cover member disposed so as to face the bearing from one side of the rotating shaft. The cover member is opposite to the bearing while ensuring a gap between the cover member and the outer ring of the bearing, thereby preventing foreign matter from entering the inner side of the outer ring from one side of the rotating shaft. The cover member has a non-circular portion at the position opposite to the bearing that corresponds to the cam when viewed from one side of the rotating shaft.

2. The harmonic gear device according to claim 1, wherein: The cover member rotates at the same speed as the cam.

3. The harmonic gear device according to claim 2, wherein: The cover member includes an umbrella portion formed so that a distance from the rotation axis gradually increases from the bearing side toward one side of the rotation axis.

4. The harmonic gear device according to claim 3, wherein: The wave gear device further includes a guide portion provided on the rigid internal gear and facing the bevel portion with a gap greater than a certain value therebetween.

5. The harmonic gear device according to any one of claims 1 to 4, wherein: At least a portion of a gap between the outer ring and the cover member is filled with a lubricant.

6. The harmonic gear device according to claim 5, wherein: The lubricant is retained in the gap between the outer ring and the cover member by a capillary phenomenon.

7. The harmonic gear device according to any one of claims 1 to 4, wherein: The cover member has a base portion, and the base portion is arranged inside the flexible external gear. A first gap is formed between an outer peripheral surface of the base portion and an inner peripheral surface of the flexible externally gear. The outer peripheral surface of the base portion and the inner peripheral surface of the flexible externally gear face each other in a direction perpendicular to the rotation axis.

8. The harmonic gear device according to claim 5, wherein: The cover member has a base portion, and the base portion is arranged inside the flexible external gear. A first gap is formed between an outer peripheral surface of the base portion and an inner peripheral surface of the flexible externally gear. The outer peripheral surface of the base portion and the inner peripheral surface of the flexible externally gear face each other in a direction perpendicular to the rotation axis.

9. The harmonic gear device according to claim 7, wherein: The cover member further includes a convex portion that protrudes from the base portion and is inserted into the inner side of the outer ring. A second gap is formed between an outer peripheral surface of the convex portion and an inner peripheral surface of the outer ring, and the outer peripheral surface of the convex portion and the inner peripheral surface of the outer ring are opposed to each other in a direction perpendicular to the rotation axis.

10. The harmonic gear device according to claim 8, wherein: The cover member further includes a convex portion that protrudes from the base portion and is inserted into the inner side of the outer ring. A second gap is formed between an outer peripheral surface of the convex portion and an inner peripheral surface of the outer ring, and the outer peripheral surface of the convex portion and the inner peripheral surface of the outer ring are opposed to each other in a direction perpendicular to the rotation axis.

11. The harmonic gear device according to claim 9, wherein: A third gap is formed between the base and the outer ring, and the base and the outer ring are opposite to each other along the direction of the rotation axis. The first gap and the second gap are connected through the third gap.

12. The harmonic gear device according to any one of claims 1 to 4, wherein: The cover member is configured to block passage of liquid.

13. The harmonic gear device according to any one of claims 1 to 4, wherein: The cover member has oleophobicity.

14. An actuator, wherein: Actuator A harmonic gear device comprising any one of claims 1 to 13; a drive source for rotating the cam; and An output portion that outputs the rotational force of the flexible externally gear.

15. A cover, wherein: The wave gear device according to any one of claims 1 to 12 is used as the cover member.

Images