Harmonic gear device, joint device for robot, and gear component

Abstract

The invention provides a harmonic gear device, a joint device for a robot, and a gear component. A harmonic gear device (1) is provided with a rigid internally toothed gear (2), a flexible externally toothed gear (3), and a harmonic generator. The harmonic generator has a non-circular cam that is rotationally driven about a rotation axis, and a bearing (42) attached to the outside of the cam. A harmonic gear device (1) deforms a flexible externally toothed gear (3) in accordance with the rotation of a cam, causes a part of external teeth (31) to mesh with a part of internal teeth (21), and causes the flexible externally toothed gear (3) to rotate relative to a rigid internally toothed gear (2) in accordance with the tooth number difference with the rigid internally toothed gear (2). A portion of an inner peripheral surface (301) of the flexible external gear (3) facing an outer ring (421) of the bearing (42) includes a small-diameter portion (305) having a narrower width than the outer ring (421) in a tooth trace direction (D1) of the external teeth (31) and a large-diameter portion (306) having a larger diameter than the small-diameter portion (305).

Description

Technical Field

[0001] The present invention generally relates to a harmonic gear device, a joint device for a robot and a gear part, and more specifically, to a harmonic gear device, a joint device for a robot and a gear part having a rigid internal gear, a flexible external gear and a harmonic generator. Background Art

[0002] Patent Document 1 discloses that a surface treatment of a flexible externally toothed gear in a wave gear device (flexible meshing gear device) is performed by nitriding.

[0003] The harmonic gear device comprises an annular rigid internal gear, a cup-shaped flexible external gear arranged inside the annular rigid gear, and an elliptical harmonic generator embedded inside the annular rigid gear. The flexible external gear comprises a cylindrical main body and external teeth formed on the outer peripheral surface of the main body. The flexible external gear is bent into an elliptical shape by the harmonic generator, and the external teeth at both ends of the elliptical shape in the long axis direction mesh with the internal teeth formed on the inner peripheral surface of the rigid internal gear.

[0004] When the harmonic generator is rotated by a motor or the like, the meshing position of the two gears moves in the circumferential direction, and a relative rotation corresponding to the difference in the number of teeth between the internal teeth and the external teeth (2N (N is a positive integer)) is generated between the two gears. Here, if the rigid internal gear side is fixed, a rotation output that is greatly reduced in speed corresponding to the difference in the number of teeth between the two gears can be obtained from the flexible external gear side.

[0005] [Prior art literature]

[0006] [Patent Document]

[0007] Patent Document 1: Japanese Patent Application Publication No. 2001-59153 Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] However, in the above-described harmonic gear device, since the harmonic generator embedded inside the flexible external gear rotates, wear may occur at the contact portion of the inner circumferential surface of the flexible external gear with the outer wheel of the bearing of the harmonic generator, especially if used for a long time. Due to the wear, a step difference may occur at the portion corresponding to the two end portions (corners) in the width direction of the outer wheel on the inner circumferential surface of the flexible external gear. In a state where such a step difference occurs, the outer wheel repeatedly collides with the step difference along with the deformation (bending) of the flexible external gear, thereby causing damage to the flexible external gear or the harmonic generator (bearing), etc., which may affect the reliability of the harmonic gear device.

[0010] The present disclosure has been made in view of the above-mentioned reasons, and an object of the present disclosure is to provide a harmonic gear device, a robot joint device, and a gear component that are unlikely to suffer a decrease in reliability.

[0011] [Technical means to solve the problem]

[0012] A harmonic gear device of one form of the present disclosure includes a rigid internal gear, a flexible external gear, and a harmonic generator. The rigid internal gear is an annular part having internal teeth. The flexible external gear is an annular part having external teeth and arranged on the inner side of the rigid internal gear. The harmonic generator includes a non-circular cam that is driven to rotate around a rotating shaft, and a bearing mounted on the outer side of the cam. The harmonic generator is arranged on the inner side of the flexible external gear to cause the flexible external gear to bend. The harmonic gear device deforms the flexible external gear as the cam rotates, causing a part of the external teeth to mesh with a part of the internal teeth, and causing the flexible external gear to rotate relative to the rigid internal gear in accordance with the difference in the number of teeth with the rigid internal gear. The portion of the inner circumferential surface of the flexible external gear that faces the outer wheel of the bearing includes a small diameter portion that is narrower than the outer wheel in the tooth line direction of the external teeth and a large diameter portion that is larger in diameter than the small diameter portion.

[0013] A robot joint device according to one aspect of the present disclosure includes the above-mentioned wave gear device, a first member fixed to the rigid internally toothed gear, and a second member fixed to the flexible externally toothed gear.

[0014] A gear component according to one aspect of the present disclosure is used as the flexible externally toothed gear of the harmonic gear device.

[0015] [Effects of the Invention]

[0016] According to the present disclosure, there is an advantage that a strain wave gear device, a robot joint device, and a gear component that are unlikely to suffer a decrease in reliability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A This is a cross-sectional view showing a schematic structure of the harmonic gear device according to the first embodiment.

[0018] Figure 1B yes Figure 1A A magnified view of area Z1.

[0019] Figure 2A This is a schematic diagram of the above-mentioned harmonic gear device viewed from the input side of the rotating shaft.

[0020] Figure 2B yes Figure 2A A magnified view of area Z1.

[0021] Figure 3A This is a schematic exploded perspective view of the above-mentioned harmonic gear device as viewed from the output side of the rotating shaft.

[0022] Figure 3B This is a schematic exploded perspective view of the above-mentioned wave gear device as viewed from the input side of the rotating shaft.

[0023] Figure 4 It is a cross-sectional view showing a schematic structure of an actuator including the above-mentioned harmonic gear device.

[0024] Figure 5 is equivalent to Figure 1B The scope enlarges the schematic cross-section of the main parts.

[0025] Figure 6 Yes Figure 5 A schematic diagram of an enlarged view of area Z1.

[0026] Figure 7 This is a conceptual explanatory diagram for illustrating the operation of the major axis side and the minor axis side of the tapered surface of the above-mentioned wave gear device.

[0027] Figure 8 This is a cross-sectional view showing an example of a robot using the above-mentioned harmonic gear device.

[0028] Fig. 9 The harmonic gear device of the second embodiment is for Figure 1B The scope enlarges the schematic cross-section of the main parts. DETAILED DESCRIPTION

[0029] (Implementation Method 1)

[0030] (1) Summary

[0031] For an overview of the harmonic gear device 1 according to the present embodiment, refer to Figure 1A to Figure 5 The drawings referred to in this disclosure are schematic drawings, and the size and thickness ratios of the components in the drawings do not necessarily reflect the actual size ratios. For example, Figure 2A to Figure 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 limited to the shapes shown in the figure.

[0032] The harmonic gear device 1 of the present embodiment is a gear device including a rigid internal gear 2, a flexible external gear 3, and a harmonic generator 4. The harmonic gear device 1 is provided with an annular flexible external gear 3 inside the annular rigid internal gear 2, and further, a harmonic generator 4 is provided inside the flexible external gear 3. The harmonic generator 4 causes the flexible external gear 3 to bend into a non-circular shape, thereby partially meshing the external teeth 31 of the flexible external gear 3 with the internal teeth 21 of the rigid internal gear 2. When the harmonic generator 4 rotates, the meshing position of the internal teeth 21 and the external teeth 31 moves in the circumferential direction of the rigid internal gear 2, so that the flexible external gear 3 generates relative rotation according to the difference in the number of teeth of the rigid internal gear 2 between the two gears (the rigid internal gear 2 and the flexible external gear 3). Here, if the rigid internal gear 2 is fixed, the flexible external gear 3 rotates with the relative rotation of the two gears. As a result, a rotation output reduced in speed at a relatively high reduction ratio corresponding to the difference in the number of teeth between the two gears can be obtained from the flexible externally-toothed gear 3 .

[0033] The harmonic generator 4 for causing the flexible externally toothed gear 3 to bend has a rotation axis Ax1 (see Figure 1A ) is a non-circular cam 41 and a bearing 42 that are driven to rotate around. 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 inner wheel 422 of the bearing 42 is fixed to the outer circumferential surface 411 of the cam 41, and the outer wheel 421 of the bearing 42 is elastically deformed by being pressed by the cam 41 via the spherical rotating body 423. Here, the outer wheel 421 can rotate relative to the inner wheel 422 by the rolling of the rotating body 423. Therefore, when the non-circular cam 41 rotates, the rotation of the inner wheel 422 is not transmitted to the outer wheel 421, but the outer teeth 31 of the flexible external gear 3 pressed by the cam 41 generate harmonic motion. By generating the harmonic motion of the outer teeth 31, as described above, the meshing position of the inner teeth 21 and the outer teeth 31 moves in the circumferential direction of the rigid internal gear 2, so that the flexible external gear 3 generates relative rotation with the rigid internal gear 2.

[0034] In short, in this type of harmonic gear device 1 , while the flexible externally toothed gear 3 is flexed by the harmonic generator 4 having the bearing 42 , power transmission is achieved by the meshing of the internal teeth 21 and the external teeth 31 .

[0035] In this kind of harmonic gear device 1, especially when used for a long time, the contact portion of the inner circumferential surface 301 of the flexible externally toothed gear 3 with the outer race 421 of the bearing 42 of the harmonic generator 4 may be worn as the harmonic generator 4 embedded in the inner side of the flexible externally toothed gear 3 rotates. Due to the wear, a step may be generated at the portion corresponding to the two ends (corners) of the outer race 421 in the width direction (rotation axis Ax1 direction) of the inner circumferential surface 301 of the flexible externally toothed gear 3. In a state where such a step is generated, the outer race 421 repeatedly collides with the step as the flexible externally toothed gear 3 deforms (bends), thereby causing damage to the flexible externally toothed gear 3 or the harmonic generator 4 (bearing 42), etc., which may affect the reliability of the harmonic gear device 1.

[0036] That is, the outer race 421 of the bearing 42 of the harmonic generator 4 is converged within the range of the flexible externally toothed gear 3 in the direction parallel to the rotation axis Ax1. Here, for example, in the harmonic gear device 1 in which the harmonic generator 4 bends the flexible externally toothed gear 3 into an elliptical shape, the flexible externally toothed gear 3 repeats two times in one direction (for example, Figure 2A The flexible external gear 3 is elastically deformed to form an elliptical long axis (in the vertical direction) by the high-speed rotation of the cam 41. Therefore, the flexible external gear 3 is repeatedly elastically deformed at a high speed by the high-speed rotation of the cam 41. With the repetition of the elastic deformation, the contact portion between the flexible external gear 3 and the harmonic generator 4 is prone to vibration. With this vibration, the two ends (corners) in the width direction of the outer wheel 421 are repeatedly pressed against the inner circumferential surface 301 of the flexible external gear 3, and the portions where the two ends in the width direction of the outer wheel 421 touch are more susceptible to wear than other portions. In addition, the inner circumferential surface 301 of the flexible external gear 3 sometimes has a lower hardness than the outer wheel 421 of the bearing 42. In this case, the wear of the portions where the two ends in the width direction of the outer wheel 421 touch in the inner circumferential surface 301 of the flexible external gear 3 is more likely to be aggravated.

[0037] As a result, the portions of the inner circumferential surface 301 of the flexible externally toothed gear 3 that are hit by both ends in the width direction of the outer race 421 are partially worn (larger than other portions), and there is a possibility that a "step difference" is generated between portions that are not in contact with the outer race 421. That is, a pair of steps spaced apart in the thrust direction (direction parallel to the rotation axis Ax1) may be generated on the inner circumferential surface 301 of the flexible externally toothed gear 3, and the outer race 421 is sandwiched between the pair of steps. In a state where such a step difference is generated, whenever the cam 41 of the harmonic generator 4 rotates and the flexible externally toothed gear 3 is deformed (deflected), a load in the thrust direction is applied from the outer race 421 to the step difference. Therefore, the flexible externally toothed gear 3 or the harmonic generator 4 (bearing 42) may be deteriorated or damaged, resulting in a decrease in the reliability of the harmonic gear device 1. Therefore, the harmonic gear device 1 of the present embodiment suppresses the generation of a step difference on the inner circumferential surface 301 of the flexible externally toothed gear 3 by the following structure, so that it is difficult to cause a decrease in reliability.

[0038] That is, the harmonic gear device 1 of this embodiment is as follows Figure 1A to Figure 3B As shown, the harmonic gear device 1 includes an annular rigid internal gear 2 having internal teeth 21, an annular flexible external gear 3 having external teeth 31, and a harmonic generator 4. The flexible external gear 3 is arranged on the inner side of the rigid internal gear 2. The harmonic generator 4 is arranged on the inner side of the flexible external gear 3 to cause the flexible external gear 3 to bend. The harmonic generator 4 has a non-circular cam 41 that is driven to rotate around a rotation axis Ax1, and a bearing 42 mounted on the outer side of the cam 41. The harmonic gear device 1 deforms the flexible external gear 3 as the cam 41 rotates, causing a portion of the external teeth 31 to mesh with a portion of the internal teeth 21, causing the flexible external gear 3 to rotate relative to the rigid internal gear 2 in accordance with the difference in the number of teeth with the rigid internal gear 2. Here, as shown in FIG. Figure 5 As shown, the portion of the inner circumferential surface 301 of the flexible externally toothed gear 3 that faces the outer race 421 of the bearing 42 includes a small diameter portion 305 that is narrower than the outer race 421 in the tooth line direction D1 of the external teeth 31 and a large diameter portion 306 that has a larger diameter than the small diameter portion 305 .

[0039] According to this form, the inner peripheral surface 301 of the flexible externally toothed gear 3 contacts the outer race 421 only at the small diameter portion 305 of the portion facing the outer race 421 of the bearing 42, and does not contact the outer race 421 at the large diameter portion 306. In addition, the small diameter portion 305 of the portion in contact with the outer race 421 of the inner peripheral surface 301 of the flexible externally toothed gear 3 is narrower than the outer race 421 in the tooth line direction D1 of the external teeth 31. Therefore, both ends (corners) in the width direction of the outer race 421 are unlikely to contact the inner peripheral surface 301 of the flexible externally toothed gear 3, and the outer race 421 is in surface contact with the small diameter portion 305 of the portion in contact with the outer race 421. Therefore, the portion of the inner peripheral surface 301 of the flexible externally toothed gear 3 facing the outer race 421 of the bearing 42 is evenly worn over the entire small diameter portion 305 contacting the outer race 421.

[0040] As a result, it is difficult to generate a "step difference" caused by local wear (larger than other parts) of the parts that the two ends of the outer race 421 in the width direction touch on the inner peripheral surface 301 of the flexible external gear 3. Therefore, in the harmonic gear device 1 of the present embodiment, it is difficult to generate a step difference on the inner peripheral surface 301 of the flexible external gear 3 caused by the contact of the bearing 42 (the outer race 421), so that the harmonic gear device 1 that is difficult to reduce reliability can be provided. In addition, the harmonic gear device 1 of the present embodiment is difficult to reduce reliability even when used for a long time, and even contributes to the improvement of the transmission efficiency, the extension of the life, and the high performance of the harmonic gear device 1.

[0041] Moreover, the harmonic gear device 1 of this embodiment is as follows Figure 4 As shown, the actuator 100 is constituted together with the driving source 101 and the output unit 102. In other words, the actuator 100 of the present embodiment includes the harmonic gear device 1, the driving source 101 and the output unit 102. The driving source 101 rotates the harmonic generator 4. The output unit 102 derives the rotational force of one of the rigid internal gear 2 and the flexible external gear 3 as an output.

[0042] Moreover, the harmonic gear device 1 of this embodiment is as follows Figure 4 As shown, the robot joint device 130 is constituted together with the first member 131 and the second member 132. In other words, the robot joint device 130 of the present embodiment includes the harmonic gear device 1, the first member 131 and the second member 132. The first member 131 is fixed to the rigid internal gear 2. The second member 132 is fixed to the flexible external gear 3. As a result, relative rotation is generated between the flexible external gear 3 and the rigid internal gear 2 in the harmonic gear device 1, and thus the first member 131 and the second member 132 in the robot joint device 130 rotate relative to each other.

[0043] According to the robot joint device 130 of the present embodiment, there is an advantage that the reliability of the strain wave gear device 1 is unlikely to be reduced.

[0044] (2) Definition

[0045] The "ring-shaped" mentioned in the present disclosure refers to a shape like a circle (loop) that forms a space (region) enclosed inside at least when viewed from above, and is not limited to a circular shape (ring-shaped) that is a perfect circle when viewed from above, and may be, for example, an elliptical shape or a polygonal shape, etc. Furthermore, even if it is a shape having a bottom 322 like a cup-shaped flexible externally toothed gear 3, as long as its main body 321 is ring-shaped, it is also called a "ring-shaped" flexible externally toothed gear 3.

[0046] The "rigidity" mentioned in the present disclosure refers to the property of an object to resist deformation when an external force is applied to the object and the object wants to deform. In other words, an object with rigidity is difficult to deform even if an external force is applied. Moreover, the "flexibility" mentioned in 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.

[0047] In particular, in the present disclosure, the "rigidity" of the rigid internal gear 2 and the "flexibility" of the flexible external gear 3 are used in a relative sense. That is, the "rigidity" of the rigid internal gear 2 means that at least compared with the flexible external gear 3, the rigid internal gear 2 has relatively high rigidity, that is, it is difficult to deform even when an external force is applied. Similarly, the "flexibility" of the flexible external gear 3 means that at least compared with the rigid internal gear 2, the flexible external gear 3 has relatively high flexibility, that is, it is easy to elastically deform when an external force is applied.

[0048] In addition, in the present disclosure, one side ( 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 of FIG. 1 , the flexible externally toothed gear 3 has an opening surface 35 on the “input side” of the rotation axis Ax1. However, “input side” and “output side” are merely labels for explanation and are not intended to limit the positional relationship between input and output when viewed from the harmonic gear device 1 .

[0049] The "non-circular shape" mentioned in the present disclosure refers to a shape that is not a perfect circle, for example, an elliptical shape and an oblong shape. In the present embodiment, as an example, the non-circular cam 41 of the harmonic generator 4 is set to an elliptical shape. That is, in the present embodiment, the harmonic generator 4 bends the flexible external gear 3 into an elliptical shape.

[0050] The "elliptical shape" mentioned in the present disclosure refers to all shapes in which a perfect circle is flattened and the intersection of the major axis and the minor axis that are orthogonal to each other is located at the center, and is not limited to a curve that includes a set of points whose sum of distances from two fixed points on a plane is fixed, that is, an "ellipse" in the mathematical sense. That is, the cam 41 in the present embodiment may be a curve that includes a set of points whose sum of distances from two fixed points on a plane is fixed, like an "ellipse" in the mathematical sense, or it may be an elliptical shape like an elongated circle instead of an "ellipse" in the mathematical sense. As described above, the drawings referred to in the present disclosure are all schematic drawings, and the size and thickness ratios of the components in the drawings do not necessarily reflect the actual size ratios. Therefore, for example, in Figure 2A In the embodiment, the shape of the cam 41 of the harmonic generator 4 is set to a slightly larger elliptical shape, but it is not intended to limit the actual shape of the cam 41.

[0051] The "rotation axis" referred to in the present disclosure refers to a virtual axis (straight line) that is the rotation center of a rotating body. That is, the rotation axis Ax1 is a virtual axis without a physical body. The harmonic generator 4 performs rotational motion around the rotation axis Ax1.

[0052] The "internal teeth" and "external teeth" mentioned in the present disclosure are not single "teeth" but a collection (group) of multiple "teeth". That is, the internal teeth 21 of the rigid internal gear 2 includes a collection of multiple teeth formed on the inner peripheral surface of the rigid internal gear 2. Similarly, the external teeth 31 of the flexible external gear 3 includes a collection of multiple teeth formed on the outer peripheral surface of the flexible external gear 3.

[0053] In the present disclosure, the term "parallel" refers to a situation where two straight lines on a plane do not intersect no matter where they are extended, that is, the angle between the two lines is strictly 0 degrees (or 180 degrees), and also refers to a situation where the angle between the two lines is within an error range of several degrees (for example, less than 10 degrees) relative to 0 degrees. Similarly, the term "orthogonal" refers to a situation where the angle between the two lines is strictly 90 degrees, and also refers to a situation where the angle between the two lines is within an error range of several degrees (for example, less than 10 degrees) relative to 90 degrees.

[0054] (3) Structure

[0055] For detailed structures of the harmonic gear device 1, the actuator 100, and the robot joint device 130 according to the present embodiment, refer to Figure 1A to Figure 4 to explain.

[0056] Figure 1A is a cross-sectional view showing a schematic structure of the harmonic gear device 1. Figure 1B yes Figure 1A A magnified view of area Z1. Figure 2A From the input side of the rotation axis Ax1 ( Figure 1A Observe the schematic diagram of the harmonic gear device 1 on the right side of the Figure 2B yes Figure 2A A magnified view of area Z1. 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 It is a cross-sectional view showing a schematic structure of an actuator 100 including the strain wave gear device 1 and a robot joint device 130 .

[0057] (3.1) Harmonic gear device

[0058] As described above, the harmonic gear device 1 of the present embodiment includes the rigid internal gear 2, the flexible external gear 3, and the harmonic generator 4. In the present embodiment, the constituent elements of the harmonic gear device 1, namely, the rigid internal gear 2, the flexible external gear 3, and the harmonic generator 4, are made of metals such as stainless steel, cast iron, carbon steel for mechanical structure, chrome-molybdenum steel, phosphor bronze, or aluminum bronze. The metal mentioned here includes metals subjected to surface treatment such as nitriding treatment.

[0059] In addition, in the present embodiment, a cup-type harmonic gear device is illustrated as an example of the harmonic gear device 1. That is, in the harmonic gear device 1 of the present embodiment, a flexible externally toothed gear 3 formed in a cup shape is used. The harmonic generator 4 is combined with the flexible externally toothed gear 3 in a manner of being accommodated in the cup-shaped flexible externally toothed gear 3.

[0060] In this embodiment, as an example, the harmonic gear device 1 is a device in which 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, along with the relative rotation of the rigid internally toothed gear 2 and the flexible externally toothed gear 3, the flexible externally toothed gear 3 rotates relative to the fixed member (the input side housing 111 etc.).

[0061] Furthermore, in the present embodiment, when the harmonic gear device 1 is used for the actuator 100, a rotational force as an input is applied to the harmonic generator 4, thereby deriving a rotational force as an output from the flexible externally toothed gear 3. That is, the harmonic gear device 1 operates by using the rotation of the harmonic generator 4 as an input rotation and the rotation of the flexible externally toothed gear 3 as an output rotation. Thus, in the harmonic gear device 1, an output rotation reduced by a relatively high reduction ratio relative to the input rotation is obtained.

[0062] Furthermore, in the harmonic gear device 1 of the present 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. In other words, the rotation axis Ax1 on the input side and the rotation axis Ax2 on the output side are coaxial. Here, the rotation axis Ax1 on the input side is the rotation center of the harmonic generator 4 to which the input rotation is given, and the rotation axis Ax1 on the output side is the rotation center of the flexible externally toothed gear 3 that generates the output rotation. That is, in the harmonic gear device 1, on the coaxial axis, the output rotation that is reduced at a relatively high reduction ratio relative to the input rotation is obtained.

[0063] The rigid internal gear 2, also called a circular spline, is an annular part having internal teeth 21. In the present embodiment, the rigid internal gear 2 has an annular shape whose at least inner circumference 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 pitches over the entire circumferential area on the inner circumferential surface of the rigid internal gear 2. That is, the pitch circle of the internal teeth 21 is a perfect circle when viewed from above. Furthermore, the rigid internal gear 2 has a predetermined thickness in the direction of the rotation axis Ax1. The internal teeth 21 are formed over the entire length of the rigid internal gear 2 in the thickness direction. The tooth lines of the internal teeth 21 are all parallel to the rotation axis Ax1.

[0064] As described above, the rigid internally toothed gear 2 is fixed to the input side housing 111 (see Figure 4 ) and the output side housing 112 (refer to Figure 4 ) etc. For this purpose, a plurality of fixing holes 22 for fixing are formed in the rigid internal gear 2 (see Figure 3A as well as Figure 3B ).

[0065] The flexible external gear 3 is also called a flex spline, and is an annular part having external teeth 31. In the present embodiment, the flexible external gear 3 is a part formed into a cup shape by a metal elastic body (metal plate) having a relatively thin wall thickness. That is, the flexible external gear 3 is flexible due to its relatively small (thin) thickness. The flexible external gear 3 has a cup-shaped main body 32. The main body 32 has a main body 321 and a bottom 322. The main body 321 has a cylindrical shape in which at least the inner peripheral surface 301 is a perfect circle when viewed from above when the flexible external gear 3 has not yet undergone elastic deformation. The central axis of the main body 321 coincides with the rotation axis Ax1. The bottom 322 is arranged on one of the opening surfaces of the main body 321, and has a disc shape that is a perfect circle when viewed from above. The bottom 322 is arranged on the opening surface on the output side of the rotation axis Ax1 among a pair of opening surfaces of the main body 321. According to the above, the main body 32 is realized in the shape of a bottomed cylindrical or cup-shaped body 321 and the bottom 322 that is open toward the input side of the rotation axis Ax1. In other words, an opening surface 35 is formed on the end surface of the flexible externally toothed gear 3 on the opposite side of the bottom 322 in the direction of the rotation axis Ax1. That is, the flexible externally toothed gear 3 is a cylinder having an opening surface 35 on one side (here, the input side of the rotation axis Ax1) in the tooth line direction D1. In the present embodiment, the main body 321 and the bottom 322 are integrally formed by a single metal member, thereby realizing a seamless main body 32.

[0066] Here, the harmonic generator 4 is combined with the flexible external gear 3 in such a manner that the harmonic generator 4 of a non-circular shape (elliptical shape) is embedded inside the main body 321. As a result, the flexible external gear 3 receives an external force in the radial direction (a direction orthogonal to the rotation axis Ax1) from the harmonic generator 4 from the inside to the outside, thereby elastically deforming into a non-circular shape. In the present embodiment, by combining the harmonic generator 4 with the flexible external gear 3, the main body 321 of the flexible external gear 3 is elastically deformed into an elliptical shape. That is, the state in which the flexible external gear 3 has not yet been elastically deformed refers to the state in which the harmonic generator 4 has not yet been combined with the flexible external gear 3. Conversely, the state in which the flexible external gear 3 has been elastically deformed refers to the state in which the harmonic generator 4 has been combined with the flexible external gear 3.

[0067] In more detail, the harmonic generator 4 is embedded in the end portion of the inner circumferential surface 301 of the main body 321 on the opposite side to the bottom 322 (the input side of the rotation axis Ax1). In other words, the harmonic generator 4 is embedded in the end portion of the main body 321 of the flexible externally toothed gear 3 on the side of the opening surface 35 in the direction of the rotation axis Ax1. Therefore, when the flexible externally toothed gear 3 is elastically deformed, the end portion of the flexible externally toothed gear 3 on the side of the opening surface 35 in the direction of the rotation axis Ax1 is deformed more greatly than the end portion on the side of the bottom 322, and becomes a shape closer to an elliptical shape. Due to the difference in the amount of deformation in the direction of the rotation axis Ax1, when the flexible externally toothed gear 3 is elastically deformed, the inner circumferential surface 301 of the main body 321 of the flexible externally toothed gear 3 includes a tapered surface 302 (see FIG. 3 ) inclined relative to the rotation axis Ax1. Figure 7 ).

[0068] In addition, the external teeth 31 are formed along the circumferential direction of the main body 321 at least at the end on the opposite side to the bottom 322 (the input side of the rotation axis Ax1) of the outer peripheral surface of the main body 321. In other words, the external teeth 31 are provided at least at the end on the side of the opening surface 35 in the direction of the rotation axis Ax1 of the main body 321 of the flexible externally toothed gear 3. The plurality of teeth constituting the external teeth 31 are all of the same shape and are provided at equal pitches over the entire area in the circumferential direction of the outer peripheral surface of the flexible externally toothed gear 3. That is, the pitch circle of the external teeth 31 is a perfect circle in a plan view when the flexible externally toothed gear 3 is not elastically deformed. The external teeth 31 are formed only within a range of a fixed width from the end edge on the side of the opening surface 35 (the input side of the rotation axis Ax1) of the main body 321. Specifically, the external teeth 31 are formed on the outer peripheral surface of at least the portion (the end on the side of the opening surface 35) in the direction of the rotation axis Ax1 of the main body 321 where the harmonic generator 4 is embedded. The tooth lines of the external teeth 31 are all parallel to the rotation axis Ax1.

[0069] In summary, in the harmonic gear device 1 of the present embodiment, the tooth traces of the internal teeth 21 of the rigid internal gear 2 and the external teeth 31 of the flexible external gear 3 are parallel to the rotation axis Ax1. Therefore, in the present embodiment, the "tooth trace direction D1" is a direction parallel to the rotation axis Ax1. In addition, the dimension of the tooth trace direction D1 in the internal teeth 21 is the tooth width of the internal teeth 21, and similarly, the dimension of the tooth trace direction D1 in the external teeth 31 is the tooth width of the external teeth 31, so the tooth trace direction D1 is synonymous with the tooth width direction.

[0070] In this embodiment, as described above, the rotation of the flexible externally toothed gear 3 is derived as the output rotation. For this purpose, the output portion 102 (see FIG. 1 ) of the actuator 100 is mounted on the flexible externally toothed gear 3. Figure 4). A plurality of mounting holes 33 for mounting the shaft as the output portion 102 are formed in the bottom 322 of the flexible externally toothed gear 3. Furthermore, a through hole 34 is formed in the central portion of the bottom 322. The thickness around the through hole 34 in the bottom 322 is thicker than other portions of the bottom 322.

[0071] The flexible externally toothed gear 3 configured in this way is arranged on the inner side of the rigid internally toothed gear 2. Here, the flexible externally toothed gear 3 is combined with the rigid internally toothed gear 2 in such a manner that the end portion of the outer peripheral surface of the main body 321 on the opposite side to the bottom 322 (the input side of the rotation axis Ax1) is inserted into the inner side of the rigid internally toothed gear 2. That is, the portion of the main body 321 of the flexible externally toothed gear 3 in which the harmonic generator 4 is embedded in the direction of the rotation axis Ax1 (the end portion on the side of the opening surface 35) is inserted into the inner side of the rigid internally toothed gear 2. Here, the external teeth 31 are formed on the outer peripheral surface of the flexible externally toothed gear 3, and the internal teeth 21 are formed on the inner peripheral surface of the rigid internally toothed gear 2. Therefore, in a state where the flexible externally toothed gear 3 is arranged on the inner side of the rigid internally toothed gear 2, the external teeth 31 and the internal teeth 21 face each other.

[0072] Here, the number of teeth of the internal teeth 21 in the rigid internal gear 2 is 2N (N is a positive integer) greater than the number of teeth of the external teeth 31 of the flexible external gear 3. In the present embodiment, as an example, N is "1", and the number of teeth (of the external teeth 31) of the flexible external gear 3 is "2" greater than the number of teeth (of the internal teeth 21) of the rigid internal gear 2. Such a difference in the number of teeth between the flexible external gear 3 and the rigid internal gear 2 defines the reduction ratio of the output rotation relative to the input rotation in the harmonic gear device 1.

[0073] Here, in this embodiment, as an example, Figure 1A as well as Figure 1B As shown, the relative position of the flexible external gear 3 and the rigid internal gear 2 in the direction of the rotation axis Ax1 is set so that the center of the tooth line direction D1 of the external teeth 31 faces the center of the tooth line direction D1 of the internal teeth 21. That is, the positions of the centers of the tooth line direction D1 of the external teeth 31 of the flexible external gear 3 and the internal teeth 21 of the rigid internal gear 2 coincide with the same position in the direction of the rotation axis Ax1. Moreover, in the present embodiment, the dimension (tooth width) of the tooth line direction D1 of the external teeth 31 is larger than the dimension (tooth width) of the tooth line direction D1 of the internal teeth 21. Therefore, in the direction parallel to the rotation axis Ax1, the internal teeth 21 converge within the tooth line range of the external teeth 31. In other words, the external teeth 31 protrude toward at least one side of the tooth line direction D1 relative to the internal teeth 21. In the present embodiment, the external teeth 31 protrude toward both sides of the tooth line direction D1 (the input side and the output side of the rotation axis Ax1) relative to the internal teeth 21.

[0074] Here, in a state where the flexible externally toothed gear 3 has not yet been elastically deformed (a state where the harmonic generator 4 has not yet been assembled to the flexible externally toothed gear 3), the pitch circle of the external teeth 31 describing a perfect circle is set to be one circle smaller than the pitch circle of the internal teeth 21 also describing a perfect circle. That is, in a state where the flexible externally toothed gear 3 has not yet been elastically deformed, the external teeth 31 and the internal teeth 21 face each other with a gap therebetween, and do not mesh with each other.

[0075] On the other hand, when the flexible externally toothed gear 3 is elastically deformed (the harmonic generator 4 is combined with the flexible externally toothed gear 3), the main body 321 is bent into an elliptical shape (non-circular shape), so that the external teeth 31 of the flexible externally toothed gear 3 partially mesh with the internal teeth 21 of the rigid internally toothed gear 2. That is, the main body 321 of the flexible externally toothed gear 3 (at least the end portion on the opening surface 35 side) is elastically deformed into an elliptical shape, thereby Figure 2A As shown, 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 external teeth 31 describing the ellipse is consistent with the diameter of the pitch circle of the internal teeth 21 describing the perfect circle, and the minor diameter of the pitch circle of the external teeth 31 describing the ellipse is smaller than the diameter of the pitch circle of the internal teeth 21 describing the perfect circle. In this way, when the flexible external-tooth gear 3 is elastically deformed, a part of the teeth constituting the external teeth 31 meshes with a part of the teeth constituting the internal teeth 21. As a result, in the harmonic gear device 1, a part of the external teeth 31 can be meshed with a part of the internal teeth 21.

[0076] The harmonic generator 4 is also called a wave generator, and is a component that causes the flexible externally toothed gear 3 to bend and generate harmonic motion in the external teeth 31 of the flexible externally toothed gear 3. In this embodiment, the harmonic generator 4 is a component having a non-circular outer peripheral shape, specifically an elliptical shape, in plan view.

[0077] The harmonic generator 4 has a non-circular (here, elliptical) cam 41 and a bearing 42 mounted on the outer periphery of the cam 41. That is, the cam 41 is combined with the bearing 42 in such a manner that the non-circular (elliptical) cam 41 is embedded in the inner side of the inner wheel 422 of the bearing 42. As a result, the bearing 42 receives an external force in the radial direction (a direction orthogonal to the rotation axis Ax1) from the inner side of the inner wheel 422 toward the outer side, thereby elastically deforming into a non-circular shape. That is, the state in which the bearing 42 has not yet been elastically deformed refers to the state in which the cam 41 has not yet been combined with the bearing 42. Conversely, the state in which the bearing 42 has been elastically deformed refers to the state in which the cam 41 has been combined with the bearing 42.

[0078] The cam 41 is a non-circular (here, elliptical) component that is driven to rotate about the rotation axis Ax1 on the input side. The cam 41 has an outer peripheral surface 411 (see Figure 1B), at least the outer peripheral surface 411 includes a metal plate that is elliptical in plan view. The cam 41 has a predetermined thickness in the direction of the rotation axis Ax1 (i.e., the tooth line direction D1). 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. In the present embodiment, as described above, the rotation of the harmonic generator 4 is set as the input rotation. For this purpose, the input portion 103 of the actuator 100 is installed on the harmonic generator 4 (refer to Figure 4 ) A cam hole 43 for mounting a shaft as the input unit 103 is formed in the center of the cam 41 of the harmonic generator 4 .

[0079] 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 spherical balls as the rolling elements 423, as an example.

[0080] The outer wheel 421 and the inner wheel 422 are both annular parts. The outer wheel 421 and the inner wheel 422 are both formed into annular parts by a metal elastic body (metal plate) with a relatively thin wall thickness. That is, the outer wheel 421 and the inner wheel 422 are each flexible due to their relatively small (thin) thickness. In the present embodiment, the outer wheel 421 and the inner wheel 422 have an annular shape that is a perfect circle when viewed from above when the bearing 42 has not yet undergone elastic deformation (the cam 41 has not yet been assembled to the bearing 42). The inner wheel 422 is one circle smaller than the outer wheel 421 and is arranged on the inner side of the outer wheel 421. Here, since the inner diameter of the outer wheel 421 is larger than the outer diameter of the inner wheel 422, a gap is generated between the inner circumferential surface 425 of the outer wheel 421 and the outer circumferential surface of the inner wheel 422.

[0081] The plurality of rotating bodies 423 are arranged in the gap between the outer wheel 421 and the inner wheel 422. The plurality of rotating bodies 423 are arranged in a row along the circumferential direction of the outer wheel 421. The plurality of rotating bodies 423 are all metal balls (spheres) of the same shape and are arranged at equal intervals throughout the circumferential direction of the outer wheel 421. Although not specifically shown here, the bearing 42 also has a retainer, and the plurality of rotating bodies 423 are retained between the outer wheel 421 and the inner wheel 422 by the retainer.

[0082] In this embodiment, as an example, the width dimensions of the outer race 421 and the inner race 422 (direction parallel to the rotation axis Ax1) are equal to the thickness of the cam 41. That is, the width dimensions of the outer race 421 and the inner race 422 are smaller than the thickness of the rigid internally toothed gear 2.

[0083] With the structure of the bearing 42, by combining the cam 41 with the bearing 42, the inner wheel 422 of the bearing 42 is fixed to the cam 41, and the inner wheel 422 is elastically deformed into an elliptical shape that imitates the outer peripheral shape of the cam 41. At this time, the outer wheel 421 of the bearing 42 is pressed by the inner wheel 422 via the plurality of rotating bodies 423 and elastically deformed into an elliptical shape. Therefore, the outer wheel 421 and the inner wheel 422 of the bearing 42 are elastically deformed into an elliptical shape. In the state where the bearing 42 is elastically deformed like this (the state where the cam 41 has been combined with the bearing 42), the outer wheel 421 and the inner wheel 422 are elliptical shapes that are similar to each other.

[0084] Even when the bearing 42 is elastically deformed, the gap between the outer wheel 421 and the inner wheel 422 is maintained substantially constant over the entire circumference of the outer wheel 421 because a plurality of rotating bodies 423 are interposed between the outer wheel 421 and the inner wheel 422. In this state, the outer wheel 421 can rotate relative to the inner wheel 422 by the rolling of the plurality of rotating bodies 423 between the outer wheel 421 and the inner wheel 422. Therefore, when the cam 41 rotates around the rotation axis Ax1 in the state in which the bearing 42 is elastically deformed, the rotation of the cam 41 is not transmitted to the outer wheel 421, and the elastic deformation of the inner wheel 422 is transmitted to the outer wheel 421 via the plurality of rotating bodies 423. That is, in the harmonic generator 4, when the cam 41 rotates around the rotation axis Ax1, the outer wheel 421 is elastically deformed so that the major axis of the elliptical shape imitated by the outer wheel 421 rotates around the rotation axis Ax1. Therefore, as the harmonic generator 4 as a whole, the outer peripheral shape of the harmonic generator 4 which is elliptical when viewed from the input side of the rotation axis Ax1 changes with the rotation of the cam 41 so that the major axis thereof rotates around the rotation axis Ax1.

[0085] The harmonic generator 4 constructed in this way is arranged on the inner side of the flexible external gear 3. Here, the flexible external gear 3 is combined with the harmonic generator 4 in such a manner that only the end portion of the inner circumferential surface 301 of the main body 321 on the opposite side to the bottom 322 (opening surface 35 side) is fitted into the harmonic generator 4. At this time, the bearing 42 of the harmonic generator 4 is arranged between the outer circumferential surface 411 of the cam 41 and the inner circumferential surface 301 of the flexible external gear 3. Here, the outer diameter of the outer race 421 in a state where the bearing 42 has not yet been elastically deformed (a state where the cam 41 has not yet been combined with the bearing 42) is the same as the inner diameter of the flexible external gear 3 (main body 321) in a state where the elastic deformation has not yet occurred. The inner diameter of the flexible external gear 3 mentioned here refers to the diameter of the small diameter portion 305 in the inner circumferential surface 301 of the flexible external gear 3. (Refer to Figure 6 ). Therefore, the outer peripheral surface 424 (refer to Figure 5) contacts the inner circumferential surface 301 of the flexible external gear 3 over the entire circumference of the bearing 42. Therefore, in a state where the flexible external gear 3 is elastically deformed (a state where the harmonic generator 4 is combined with the flexible external gear 3), the main body 321 is bent into an elliptical shape (non-circular shape). In this state, the flexible external gear 3 is fixed relative to the outer ring 421 of the bearing 42.

[0086] However, since the flexible external gear 3 and the harmonic generator 4 are only fitted together, the flexible external gear 3 and the outer wheel 421 of the bearing 42 are not completely fixed. Therefore, a small gap X1 is generated between the flexible external gear 3 and the outer wheel 421 embedded inside the flexible external gear 3 (see Figure 1B ). Strictly speaking, since the diameter of the outer circumference 424 of the outer wheel 421 is slightly smaller than the diameter of the inner circumference 301 of the flexible external gear 3, the gap X1 between the outer wheel 421 and the flexible external gear 3 is not completely filled, and the gap X1 is at least partially generated. Also, due to the influence of this gap X1, the outer wheel 421 and the flexible external gear 3 are elastically deformed with the rotation of the cam 41 of the harmonic generator 4, and relative rotation may be generated between the outer wheel 421 and the flexible external gear 3. This relative rotation is, for example, a rotation of about one thousandth or one hundredth of the rotation speed of the cam 41, but due to this relative rotation, the relative friction between the outer wheel 421 and the flexible external gear 3 is one of the causes of wear and loss.

[0087] The "gap" mentioned in the present disclosure refers to a space that may be generated between the facing surfaces of two objects, and a gap may be generated between the two objects even if the two objects are not separated. That is, even if the two objects are in contact, a small gap may be generated between the two objects. Between the flexible external gear 3 and the outer wheel 421 embedded in the inner side of the flexible external gear 3, a gap X1 is generated between the outer peripheral surface 424 of the outer wheel 421 facing each other and the inner peripheral surface 301 of the flexible external gear 3. However, basically, since the outer peripheral surface 424 of the outer wheel 421 is in contact with the inner peripheral surface 301 of the flexible external gear 3, a large gap X1 will not be generated between the two. Therefore, the gap X1 between the outer wheel 421 and the flexible external gear 3 is a small gap that may be locally generated between the outer peripheral surface 424 of the outer wheel 421 and the inner peripheral surface 301 of the flexible external gear 3. As an example, a microscopic gap X1 is generated between the outer peripheral surface 424 of the outer ring 421 and the inner peripheral surface 301 of the flexible externally-toothed gear 3 to such an extent that the lubricant Lb1 can penetrate.

[0088] In the harmonic gear device 1 of the structure, as Figure 2AAs shown, the main body 321 of the flexible external gear 3 is bent into an elliptical shape (non-circular shape), so that the external teeth 31 of the flexible external gear 3 partially mesh with the internal teeth 21 of the rigid internal gear 2. That is, the flexible external gear 3 (main body 321) is elastically deformed into an elliptical shape, so that the two external teeth 31 corresponding to the two ends of the long axis direction of the elliptical shape are meshed with the internal teeth 21. And when the cam 41 rotates around the rotation axis Ax1, the rotation of the cam 41 is not transmitted to the outer wheel 421 and the flexible external gear 3, and the elastic deformation of the inner wheel 422 is transmitted to the outer wheel 421 and the flexible external gear 3 via the plurality of rotating bodies 423. Therefore, the outer peripheral shape of the flexible external gear 3, which is an elliptical shape viewed from the input side of the rotation axis Ax1, changes with the rotation of the cam 41 so that its long axis rotates around the rotation axis Ax1.

[0089] As a result, the external teeth 31 formed on the outer peripheral surface of the flexible externally toothed gear 3 generate harmonic motion. By generating the harmonic motion of the external teeth 31, the meshing position of the internal teeth 21 and the external teeth 31 moves along the circumferential direction of the rigid internally toothed gear 2, and relative rotation occurs between the flexible externally toothed gear 3 and the rigid internally toothed gear 2. That is, the external teeth 31 mesh with the internal teeth 21 at both ends of the long axis direction of the elliptical shape of the flexible externally toothed gear 3 (the main body 321), so that the meshing position of the internal teeth 21 and the external teeth 31 moves by rotating around the rotation axis Ax1 through the long axis of the elliptical shape. In this way, the harmonic gear device 1 of the present embodiment deforms the flexible externally toothed gear 3 as the harmonic generator 4 rotates around the rotation axis Ax1, so that a part of the external teeth 31 meshes with a part of the internal teeth 21, and the flexible externally toothed gear 3 rotates according to the difference in the number of teeth with the rigid internally toothed gear 2.

[0090] In the harmonic gear device 1, as described above, 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 harmonic gear device 1. That is, when the number of teeth of the rigid internally toothed gear 2 is set to "V1" and the number of teeth of the flexible externally toothed gear 3 is set to "V2", the reduction ratio R1 is expressed by the following formula 1.

[0091] R1=V2 / (V1-V2)…(Formula 1)

[0092] In short, the smaller the difference in the number of teeth (V1-V2) between the rigid internal gear 2 and the flexible external gear 3 is, the larger the reduction ratio R1 is. For example, if the number of teeth V1 of the rigid internal gear 2 is "72" and the number of teeth V2 of the flexible external gear 3 is "70", and the difference in the number of teeth (V1-V2) is "2", then according to the above formula 1, the reduction ratio R1 is "35". At this time, when the cam 41 rotates one circle (360 degrees) clockwise around the rotation axis Ax1 as viewed from the input side of the rotation axis Ax1, the flexible external gear 3 rotates counterclockwise around the rotation axis Ax1 by an amount corresponding to the difference in the number of teeth "2" (i.e., 10.3 degrees).

[0093] According to the harmonic 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 internally toothed gear 2 and the flexible externally toothed gear 3 ).

[0094] The harmonic gear device 1 only needs to include at least the rigid internal gear 2 , the flexible external gear 3 , and the harmonic generator 4 , and may further include, for example, the spline bushing 113 described in the section “(3.2) Actuator” as a constituent element.

[0095] (3.2) Actuator

[0096] Next, the structure of the actuator 100 according to the present embodiment will be described in further detail.

[0097] The actuator 100 of this embodiment is as follows Figure 4 As shown, the actuator 100 includes the harmonic gear device 1 of the present embodiment, a drive source 101, and an output portion 102. That is, the actuator 100 includes the drive source 101 and the output portion 102 in addition to the rigid internal gear 2, the flexible external gear 3, and the harmonic generator 4 constituting the harmonic gear device 1. Furthermore, the actuator 100 includes an input portion 103, an input side housing 111, an output side housing 112, a spline bushing 113, a spacer 114, a first clip 115, a second clip 116, and a mounting plate 117 in addition to the harmonic gear device 1, the drive source 101, and the output portion 102. Furthermore, in the present embodiment, the actuator 100 also includes input side bearings 118, 119, an input side oil seal 120, output side bearings 121, 122, and an output side oil seal 123.

[0098] In this embodiment, the parts of the actuator 100 other than the driving source 101, the input side oil seal 120 and the output side oil seal 123 are made of metals such as stainless steel, cast iron, carbon steel for mechanical structures, chrome-molybdenum steel, phosphor bronze or aluminum bronze.

[0099] The driving source 101 is a power generating source such as a motor (electric motor). The power generated by the driving source 101 is transmitted to the cam 41 of the harmonic generator 4 in the harmonic gear device 1. Specifically, the driving source 101 is connected to a shaft as an input part 103, and the power generated by the driving source 101 is transmitted to the cam 41 via the input part 103. Thus, the driving source 101 can rotate the cam 41.

[0100] The output part 102 is a cylindrical shaft arranged along the rotation axis Ax2 on the output side. The central axis of the shaft of the output part 102 is consistent with the rotation axis Ax2. The output part 102 is held by the output side housing 112 in a manner that it can rotate around the rotation axis Ax2. The output part 102 is fixed to the bottom 322 of the main body 32 in the flexible external gear 3, and rotates together with the flexible external gear 3 around the rotation axis Ax2. That is, the output part 102 derives the rotational force of the flexible external gear 3 as an output.

[0101] The input part 103 is a cylindrical shaft arranged along the rotation axis Ax1 of 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 held by the input side housing 111 in a manner that it can rotate around the rotation axis Ax1. The input part 103 is mounted on the cam 41 of the harmonic 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 driving source 101 as input to the cam 41. In this embodiment, as described above, the rotation axis Ax1 of the input side and the rotation axis Ax2 of the output side are located on the same straight line, so the input part 103 and the output part 102 will be located on the same axis.

[0102] The input side housing 111 holds the input part 103 via the input side bearings 118 and 119 so that the input part 103 can rotate. A pair of input side bearings 118 and 119 are arranged at intervals along the rotation axis Ax1. In this embodiment, the shaft of the input part 103 passes through the input side housing 111, and the front end of the input part 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 sealed by the input side oil seal 120 .

[0103] The output side housing 112 holds the output part 102 via the output side bearings 121 and 122 so that the output part 102 can rotate. A pair of output side bearings 121 and 122 are arranged at intervals along the rotation axis Ax2. In this embodiment, the shaft of the output part 102 passes through the output side housing 112, and the front end of the output part 102 extends from the end face ( Figure 4 The gap between the output portion 102 and the end surface of the output side housing 112 on the output side of the rotation axis Ax1 is sealed by an output side oil seal 123.

[0104] Here, the input side housing 111 and the output side housing 112 are as shown in FIG. Figure 4 As shown, the input side housing 111 and the output side housing 112 are connected to each other in a state where the rigid internal gear 2 of the harmonic gear device 1 is sandwiched from both sides in a direction parallel to the rotation axis Ax1, that is, in the tooth line direction D1. Specifically, the input side housing 111 contacts the rigid internal gear 2 from the input side of the rotation axis Ax1, and the output side housing 112 contacts the rigid internal gear 2 from the output side of the rotation axis Ax1. In this way, the input side housing 111 is fastened and fixed to the output side housing 112 by screws (bolts) through a plurality of fixing holes 22 in a state where the rigid internal gear 2 is sandwiched between the input side housing 111 and the output side housing 112. As a result, the input side housing 111, the output side housing 112, and the rigid internal gear 2 are connected to each other and integrated. In other words, the rigid internal gear 2, the input side housing 111, and the output side housing 112 together constitute the outer profile of the actuator 100.

[0105] The spline bushing 113 is a cylindrical part used to connect the shaft of the input part 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 part 103 is inserted into the spline bushing 113 in a manner of penetrating the spline bushing 113. Here, the movement of the spline bushing 113 relative to both the cam 41 and the input part 103 in the rotation direction centered on the rotation axis Ax1 is restricted, and it is movable at least relative to the input part 103 in the direction parallel to the rotation axis Ax1. Thus, a spline connection structure is realized as a connection structure between the input part 103 and the cam 41. Therefore, the cam 41 can move along the rotation axis Ax1 relative to the input part 103, and rotate together with the input part 103 centered on the rotation axis Ax1.

[0106] The spacer 114 is a part for filling the gap between the spline bushing 113 and the cam 41. The first buckle 115 is a part for preventing the spline bushing 113 from being disengaged from the cam 41. The first buckle 115 includes, for example, an E-ring, and is mounted on the spline bushing 113 at a position on the input side of the rotation axis Ax1 as viewed from the cam 41. The second buckle 116 is a part for preventing the input portion 103 from being disengaged from the spline bushing 113. The second buckle 116 includes, for example, an E-ring, and is mounted on the input portion 103 in such a manner that it contacts the spline bushing 113 from the output side of the rotation axis Ax1.

[0107] The mounting plate 117 is a component for mounting the shaft as the output part 102 to the bottom 322 of the flexible externally toothed gear 3. Specifically, the mounting plate 117 is fastened and fixed to the flange part by screws (bolts) through the plurality of mounting holes 33, with the peripheral portion of the through hole 34 in the bottom 322 being sandwiched between the mounting plate 117 and the flange part of the output part 102. Thus, the shaft as the output part 102 is fixed to the bottom 322 of the flexible externally toothed gear 3.

[0108] Furthermore, in the present embodiment, the lubricant Lb1 is sealed inside the outer shell of the actuator 100 including the input-side housing 111, the output-side housing 112, and the rigid internally toothed gear 2. That is, in the space surrounded by the input-side housing 111, the output-side housing 112, and the rigid internally toothed gear 2, there is a "lubricant reservoir" that can store the lubricant Lb1 in liquid or gel form.

[0109] That is, in the harmonic gear device 1 of the present embodiment, a liquid or gel lubricant Lb1 is injected, for example, into the meshing portion between the internal teeth 21 and the external teeth 31 and between the outer race 421 and the inner race 422 of the bearing 42. As an example, the lubricant Lb1 is a liquid lubricant (oil). Furthermore, when the harmonic gear device 1 is used, the lubricant Lb1 also enters the gap X1 between the outer race 421 (outer peripheral surface 424) of the bearing 42 and the flexible external gear 3.

[0110] In this embodiment, as an example, Figure 4 As shown in FIG. 1 , the lubricant Lb1 is stored only at the lower part (vertical lower part) of the outer profile of the actuator 100 so that the liquid level of the lubricant Lb1 is located below the lower ends of the output side bearings 121 and 122. Therefore, for the external teeth 31 and the outer ring 421 of the bearing 42, etc., Figure 4 In the state, only a part in the rotation direction is immersed in the lubricant Lb1. When the output part 102 rotates with the rotation of the input part 103 from this state, the outer ring 421 and the flexible externally toothed gear 3 also rotate around the rotation axis Ax1, so as a result, the entire rotation direction of the external teeth 31 and the outer ring 421 of the bearing 42, etc. will be immersed in the lubricant Lb1.

[0111] (3.3) Robot joint device

[0112] Next, the structure of the robot joint device 130 according to the present embodiment will be described in further detail.

[0113] The robot joint device 130 of this embodiment is as follows Figure 4As shown, the robot joint device 130 includes the harmonic gear device 1 of this embodiment, a first member 131 and a second member 132. That is, the robot joint device 130 includes the first member 131 and the second member 132 in addition to the rigid internal gear 2, the flexible external gear 3 and the harmonic generator 4 constituting the harmonic gear device 1.

[0114] The first member 131 is a member fixed to the rigid internal gear 2, and the second member 132 is a member fixed to the flexible external gear 3. Therefore, in the wave gear device 1, by causing relative rotation between the flexible external gear 3 and the rigid internal gear 2, relative rotation is also caused between the first member 131 and the second member 132. In this way, the robot joint device 130 constitutes a joint portion when two or more members (the first member 131 and the second member 132) are connected (movably connected) in a state where they can move with each other via the wave gear device 1.

[0115] Here, the first member 131 and the second member 132 may be fixed directly or indirectly to the rigid internally toothed gear 2 and the flexible externally toothed gear 3 , respectively. Figure 4 In the example of , the first member 131 is coupled to the output side housing 112, thereby being indirectly coupled (fixed) to the rigid internal gear 2. Similarly, the second member 132 is coupled to the output portion 102, thereby being indirectly coupled (fixed) to the flexible external gear 3.

[0116] In the robot joint device 130 configured as above, for example, when the cam 41 of the harmonic generator 4 rotates by the power generated by the driving source 101, relative rotation occurs between the flexible external gear 3 and the rigid internal gear 2. And, along with the relative rotation of the flexible external gear 3 and the rigid internal gear 2, relative rotation occurs between the first member 131 and the second member 132 around the rotation axis Ax2 on the output side (coaxial with the rotation axis Ax1 on the input side). As a result, according to the robot joint device 130, the first member 131 and the second member 132 connected via the harmonic gear device 1 can be driven to rotate relatively around the rotation axis Ax1. Thus, the robot joint device 130 can realize the joint mechanism of various robots.

[0117] (4) Detailed structure of each part

[0118] Next, for more detailed structures of the various components of the harmonic gear device 1 of this embodiment, refer to Figure 1A to Figure 2B ,

[0119] Figure 5 as well as Figure 6 Let's explain in further detail. Figure 5 is equivalent to Figure 1BThe scope enlarges the schematic cross-section of the main parts.

[0120] Figure 6 Yes Figure 5 A schematic diagram of an enlarged view of area Z1.

[0121] (4.1)Through hole

[0122] In this embodiment, if Figure 1A as well as Figure 1B As shown, at least one of the outer race 421 of the bearing 42 and the external teeth 31 of the flexible external gear 3 is provided with a through hole H1 that penetrates in the radial direction and connects to the gap X1 between the outer race 421 and the flexible external gear 3. That is, the inner circumferential surface 425 (see FIG. 1 ) of the outer race 421 of the bearing 42, which becomes the rotation surface of the plurality of rotating bodies 423 Figure 5 ) and at least one of the outer peripheral surfaces of the outer teeth 31 of the flexible externally toothed gear 3 that mesh with the inner teeth 21 are connected to the gap X1 through the through hole H1. Therefore, the lubricant Lb1 can be supplied to the gap X1 between the outer race 421 and the flexible externally toothed gear 3 through the through hole H1.

[0123] That is, the harmonic gear device 1 of the present embodiment is provided with the through hole H1, so that the lubricant Lb1 can be supplied to the contact portion between the flexible external gear 3 and the harmonic generator 4 through the through hole H1, thereby maintaining sufficient lubricant Lb1 at the contact portion. As a result, it helps to prevent "lack of lubricant", and the surface of the contact portion between the outer ring 421 and the flexible external gear 3 is covered with the lubricant Lb1, and the occurrence of wear loss is suppressed. Therefore, in the harmonic gear device 1 of the present embodiment, it is difficult to cause a malfunction caused by wear loss between the outer ring 421 and the flexible external gear 3, and it is possible to provide a harmonic gear device 1 that is unlikely to cause a decrease in reliability.

[0124] In addition, the through hole H1 only needs to be provided in at least one of the outer ring 421 and the external teeth 31 of the flexible external gear 3. In the present disclosure, when distinguishing between the through holes H1 provided in the outer ring 421 and the external teeth 31 of the flexible external gear 3, the through hole H1 provided in the outer ring 421 is referred to as the "first through hole", and the through hole H2 provided in the external teeth 31 of the flexible external gear 3 is referred to as the "second through hole". In the present embodiment, as an example, the through hole H1 is provided only in the outer ring 421 of the outer ring 421 and the external teeth 31 of the flexible external gear 3. In other words, in the present embodiment, the through hole H1 includes the "first through hole" provided in the outer ring 421. On the other hand, the through hole H2 (second through hole) on the side of the external teeth 31 of the flexible external gear 3 is described in "(8) Modification".

[0125] Moreover, the term "penetrating in the radial direction" in the present disclosure means penetrating in the radial direction, i.e., in the direction perpendicular to the rotation axis Ax1, i.e., in the radial direction. That is, if the through hole H1 is provided in the outer ring 421 as in the present embodiment, the through hole H1 only needs to penetrate between the two radial surfaces of the outer ring 421, i.e., the inner peripheral surface 425 and the outer peripheral surface 424, and may be inclined with respect to the radial direction, for example.

[0126] Here, first, regarding the shape and size of the through hole H1 in this embodiment, refer to Figure 5 to explain.

[0127] The through hole H1 (first through hole) provided in the outer ring 421 penetrates the outer ring 421 in the radial direction. Thus, one of the opening surfaces of the through hole H1 faces the gap X1 between the outer ring 421 and the flexible external gear 3, and the other opening surface of the through hole H1 opens at the inner peripheral surface 425 of the outer ring 421. Therefore, one end of the through hole H1 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3, and the other end is connected to the space between the inner peripheral surface 425 of the outer ring 421 and the outer peripheral surface of the inner ring 422. Therefore, the space between the inner peripheral surface 425 of the outer ring 421 where the plurality of rotating bodies 423 are arranged and the outer peripheral surface of the inner ring 422 is connected to the gap X1 between the outer ring 421 and the flexible external gear 3 via the through hole H1.

[0128] Moreover, the through hole H1 is a circular hole whose cross-sectional shape perpendicular to the radial direction is circular (perfect circle). In the present embodiment, as an example, the center line of the through hole H1 is parallel to the radial direction. That is, the through hole H1 is a hole extending straightly from the inner peripheral surface 425 of the outer wheel 421 to the outer peripheral surface 424 in the radial direction. Furthermore, the cross-sectional shape of the through hole H1 perpendicular to the radial direction is the same shape throughout the entire length of the through hole H1 in the radial direction. That is, a cylindrical space is formed inside the through hole H1.

[0129] Here, the diameter of the through hole H1 is (Refer to Figure 5 ) is as small as the diameter of each of the plurality of rotating bodies 423 (Refer to Figure 5 The diameter of the through hole H1 is less than 0.1 times of 1.0 mm or less. When the cross-sectional shape of the through hole H1 is a perfect circle, it refers to its diameter. When the cross-sectional shape of the through hole H1 is a non-circular shape (for example, an elliptical shape), it refers to its dimension in the short axis direction. is the diameter of the rotating body 423 The diameter of the through hole H1 is less than 0.1 times and less than 1.0 mm. The lubricant Lb1 can be efficiently supplied to the gap X1 between the outer ring 421 and the flexible externally-toothed gear 3 through the through-hole H1 .

[0130] According to the above-described structure, the space between the outer ring 421 and the inner ring 422 is connected to the gap X1 between the outer ring 421 and the flexible externally toothed gear 3 via the through hole H1 , so the lubricant Lb1 between the outer ring 421 and the inner ring 422 is supplied to the gap X1 through the through hole H1 . Figure 5 In FIG. 4 , the flow of the lubricant Lb1 in the through hole H1 is schematically indicated by the dotted arrow. In particular, when the bearing 42 is in operation and the plurality of rotating bodies 423 rotate, the rotating bodies 423 function as a pump and can send the lubricant Lb1 between the outer ring 421 and the inner ring 422 into the gap X1 through the through hole H1. As a result, the "lubricant shortage" in which the lubricant Lb1 is insufficient or exhausted is prevented at the contact portion between the outer ring 421 and the flexible externally toothed gear 3, and the occurrence of wear loss is easily suppressed.

[0131] In summary, the harmonic gear device 1 of the present embodiment has a pump structure that supplies the lubricant Lb1 to the gap X1 through the through hole H1 when the flexible external gear 3 rotates relative to the rigid internal gear 2. When the flexible external gear 3 rotates relative to the rigid internal gear 2, the plurality of rotors 423 of the bearing 42 rotate along the circumferential direction of the outer race 421, and therefore, as described above, the plurality of rotors 423 function as a pump. That is, the plurality of rotors 423 constitute a pump structure. In particular, in the present embodiment, the pressure in the space between the outer race 421 and the inner race 422 increases as the rotor 423 rotates in the space between the outer race 421 and the inner race 422, and thus the lubricant Lb1 between the outer race 421 and the inner race 422 is squeezed out to the gap X1 side through the through hole H1. In this way, the rotor 423 constitutes a positive displacement pump such as an impeller pump, and squeezes the lubricant Lb1 to the gap X1 side with sufficient pressure, so that sufficient lubricant Lb1 is easily supplied to the gap X1.

[0132] Furthermore, the opening surface of the through hole H1 on the inner circumferential surface 425 side of the outer ring 421 opens at the bottom surface of the rotation groove 426 formed on the inner circumferential surface 425 of the outer ring 421. That is, a rotation groove 426 extending along the circumferential direction over the entire circumference of the outer ring 421 is formed at the center portion of the inner circumferential surface 425 of the outer ring 421 in the width direction (tooth trace direction D1), and the plurality of rotating bodies 423 rotate along the rotation groove 426. A similar rotation groove 427 is also formed on the outer circumferential surface of the inner ring 422, and the plurality of rotating bodies 423 are held in a sandwiched manner between these mutually facing rotation grooves 426, 427. Furthermore, the through hole H1 is arranged in the range where the rotation groove 426 is formed in the width direction (tooth trace direction D1) of the outer ring 421 so as to open at the bottom surface of the rotation groove 426 of the outer ring 421.

[0133] Furthermore, in the present embodiment, the through hole H1 is arranged at the same position as the center of the plurality of rotating bodies 423 in the direction parallel to the rotation axis Ax1 (tooth trace direction D1). In other words, the through hole H1 is arranged at the center of the rotation groove 426 in the width direction (tooth trace direction D1) of the outer ring 421. According to this structure, the center of the plurality of rotating bodies 423 passes through the opening surface of the through hole H1, and when the rotating body 423 rotates, the rotating body 423 functions efficiently as a pump, so that the lubricant Lb1 is easily sent to the gap X1 through the through hole H1. Furthermore, it is known that the outer ring 421 and the flexible externally toothed gear 3 are mainly in contact at both ends of the outer ring 421 in the width direction (tooth trace direction D1). Therefore, by forming the through hole H1 in the center of the outer ring 421 in the width direction (tooth trace direction D1), it is difficult to cause the strength of the outer ring 421 to decrease due to the through hole H1 when the outer ring 421 and the flexible externally toothed gear 3 are in contact.

[0134] Here, the rotating grooves 426, 427 are as follows Figure 5 As shown, the cross-sectional shape perpendicular to the circumferential direction of the outer ring 421 is formed into an arc shape. Furthermore, the curvature of the arc in the cross-sectional shape of the rotating grooves 426 and 427 is greater than the curvature of each of the plurality of rotating bodies 423. In other words, the radius of curvature of the arc in the cross-sectional shape of the rotating grooves 426 and 427 is smaller than the radius of curvature of the rotating body 423. Therefore, in a state where the plurality of rotating bodies 423 are held in a sandwiched manner between the rotating grooves 426 and 427, a certain degree of clearance is ensured between the bottom surface of the rotating grooves 426 and 427 and the surface of each rotating body 423. That is, as Figure 5 As shown, each rotating body 423 is supported at four points in total, namely, at both ends of the rotating groove 426 in the outer ring 421 in the width direction (tooth line direction D1) and at both ends of the rotating groove 427 in the inner ring 422 in the width direction (tooth line direction D1). However, in reality, a load in the thrust direction (direction parallel to the rotation axis Ax1) is relatively borne between the outer ring 421 and the inner ring 422, so the rotating body 423 is supported by a pair of ends that are in a mutually oblique relationship.

[0135] Therefore, the opening surface of the through hole H1 formed on the bottom surface of the rotation groove 426 faces the surface of the rotating body 423 across the gap. In short, in the present embodiment, in the radial direction, a distance greater than a specified value is ensured between the tracks of the plurality of rotating bodies 423 and the opening surface on the inner circumferential surface 425 side of the outer ring 421 provided with the (first) through hole H1 of the outer ring 421. That is, even when the rotating body 423 is located at a position corresponding to the through hole H1, a distance greater than a specified value (gap) is ensured between the opening surface of the through hole H1 and the rotating body 423, and the through hole H1 is not blocked by the rotating body 423. Thus, when the plurality of rotating bodies 423 rotate, even if the rotating body 423 passes through the through hole H1, the rotating body 423 does not collide with the opening edge of the through hole H1. As a result, when the rotating body 423 passes through the through hole H1 , the impact caused by the rotating body 423 colliding with the opening edge of the through hole H1 can be avoided, and the outer ring 421 and the rotating body 423 can be easily protected from the impact.

[0136] (4.2) Number and arrangement of through holes

[0137] Next, regarding the number and arrangement of the through holes H1 in this embodiment, refer to Figure 2A as well as Figure 2B Provide explanation.

[0138] like Figure 2A As shown, the through holes H1 include a plurality of first through holes provided in the outer ring 421 in a manner arranged in the circumferential direction of the outer ring 421. In the present embodiment, the through holes H1 include only the first through holes provided in the outer ring 421, and therefore all the plurality of through holes H1 are arranged in the circumferential direction of the outer ring 421. In the present embodiment, as an example, three through holes H1 are provided in the outer ring 421. Therefore, the lubricant Lb1 can be supplied to the gap X1 between the outer ring 421 and the flexible externally toothed gear 3 through the through holes H1 at multiple locations (three locations in the present embodiment) in the circumferential direction of the outer ring 421. As a result, compared with a case where the through hole H1 is provided at only one location in the circumferential direction of the outer ring 421, it is easy to supply the lubricant Lb1 over the entire circumferential region of the outer ring 421 in the gap X1.

[0139] Here, if Figure 2AAs shown, the interval P1 of the plurality of through holes H1 (first through holes) is a value other than a multiple of the interval P2 of the plurality of rotating bodies 423. In the present embodiment, as an example, the bearing 42 has 26 rotating bodies 423, and the outer ring 421 has 3 through holes H1. Furthermore, the 26 rotating bodies 423 and the 3 through holes H1 are arranged at equal intervals (equal intervals) in the circumferential direction of the outer ring 421. Therefore, the interval P1 of the 3 through holes H1 in the circumferential direction of the outer ring 421 is 120 degrees (=360 degrees ÷ 3), and the interval P2 of the 26 rotating bodies 423 in the circumferential direction of the outer ring 421 is 13.85 degrees (=360 degrees ÷ 26). Here, the interval P1 is a value representing the distance between the centers of two through holes H1 adjacent to each other in the circumferential direction of the outer ring 421 in terms of the angle around the rotation axis Ax1, and similarly, the interval P2 is a value representing the distance between the centers of two rotating bodies 423 adjacent to each other in the circumferential direction of the outer ring 421 in terms of the angle around the rotation axis Ax1. In the present embodiment, the interval P1 is set to a value that is not divisible by the interval P2, so that no matter which integer is multiplied by the interval P2 (13.85 degrees) of the plurality of rotating bodies 423, it will not coincide with the interval P1 (120 degrees) of the plurality of through holes H1.

[0140] Thus, the rotating body 423 will not be located at positions corresponding to all through holes H1 at the same time. That is, when one rotating body 423 is located at a position corresponding to one through hole H1, the rotating body 423 will not be located at positions corresponding to the other two through holes H1. Therefore, in the harmonic gear device 1 of this embodiment, it is possible to avoid the generation of relatively large impacts that may be generated when multiple rotating bodies 423 are simultaneously inserted into (or removed from) multiple through holes H1, and it is easy to protect the outer ring 421 and the rotating body 423 from the impact. In addition, compared with the case where the rotating body 423 is located on all through holes H1 at the same time, the pumping action brought about by the rotation of the rotating body 423 also becomes more efficient.

[0141] (4.3) Inner Surface Shape of Flexible Externally Toothed Gear

[0142] Next, regarding the surface condition of the inner peripheral surface 301 of the flexible externally toothed gear 3 in this embodiment, refer to Figure 5 as well as Figure 6 Provide explanation.

[0143] In this embodiment, as described above, the portion of the inner circumferential surface 301 of the flexible externally toothed gear 3 that faces the outer race 421 of the bearing 42 includes the small diameter portion 305 that is narrower than the outer race 421 in the tooth trace direction D1 of the external teeth 31 and the large diameter portion 306 that is larger in diameter than the small diameter portion 305. The large diameter portion 306 has a relatively larger diameter than the small diameter portion 305, and thus is a portion that is less likely to come into contact with the outer race 421 in the width direction (tooth trace direction D1) of the outer race 421. That is, the diameter of the portion of the inner circumferential surface 301 of the flexible externally toothed gear 3 that faces the outer race 421 is not constant, but includes the small diameter portion 305 that is relatively smaller in diameter and the large diameter portion 306 that is relatively larger in diameter. Therefore, in a state where the harmonic generator 4 is embedded inside the main body 321 of the flexible externally toothed gear 3, only the small diameter portion 305 of the small diameter portion 305 and the large diameter portion 306 contacts the outer circumferential surface 424 of the outer race 421.

[0144] That is, the outer diameter of the outer race 421 in a state where the bearing 42 has not yet been elastically deformed (the cam 41 is not assembled to the bearing 42) and the diameter (diameter) of the small diameter portion 305 of the flexible externally toothed gear 3 in a state where the bearing 42 has not yet been elastically deformed are equal to each other. On the other hand, due to the diameter (diameter) of the large diameter portion 306 (Refer to Figure 6 ) is larger than the diameter of the small diameter portion 305 Therefore, when the harmonic generator 4 is fitted inside the main body 321 of the flexible externally-toothed gear 3 , the large-diameter portion 306 is not in contact with the outer peripheral surface 424 of the outer ring 421 .

[0145] Furthermore, the small diameter portion 305, which is a contact portion with the outer race 421 in the inner circumferential surface 301 of the flexible externally toothed gear 3, is narrower than the outer race 421 in the tooth line direction D1 (direction parallel to the rotation axis Ax1) of the external teeth 31. Therefore, on the inner circumferential surface 301 of the flexible externally toothed gear 3, it is difficult to generate a "step difference" caused by local wear (larger than other portions) of the portions contacted by the two ends in the width direction of the outer race 421.

[0146] Here, there is a difference of 5 μm or more and 30 μm or less between the radius of the small diameter portion 305 and the radius of the large diameter portion 306. Figure 6 As shown, if the diameter of the small diameter portion 305 1 / 2 and the diameter of the large diameter part 306 , the difference is 5 μm or more and 30 μm or less. Thus, a stepped middle portion 307 having a height difference of 5 μm or more and 30 μm or less is generated between the small diameter portion 305 and the large diameter portion 306. Thus, by providing a sufficient height difference between the small diameter portion 305 and the large diameter portion 306, a sufficient gap X1 is ensured between the large diameter portion 306 and the outer ring 421, thereby preventing the outer ring 421 from contacting the large diameter portion 306.

[0147] In the present embodiment, the dimension L1 (width) of the small diameter portion 305 in the tooth line direction D1 of the external teeth 31 is equal to the diameter (diameter) of the rotating body 423 of the bearing 42. That is, the dimension L1 of the small diameter portion 305 of the external tooth 31 in the tooth trace direction D1 is set to be smaller than the dimension of the outer wheel 421 in the tooth trace direction D1 and equal to the diameter of the rotating body 423. As an example, Figure 5 As shown, the size L1 of the small diameter portion 305 may also be larger than the diameter of the rotating body 423. This example is not limited thereto, and the diameter of the rotating body 423 may also be the following.

[0148] Here, if Figure 5 As shown, in this embodiment, large diameter portions 306 are provided on both sides of the small diameter portion 305 in the tooth trace direction D1 of the external teeth 31. That is, the large diameter portion 306 includes a first large diameter portion 306A and a second large diameter portion 306B located on both sides of the small diameter portion 305 in the tooth trace direction D1 of the external teeth 31. The first large diameter portion 306A is located on the output side of the rotation axis Ax1 when viewed from the small diameter portion 305, and the second large diameter portion 306B is located on the input side of the rotation axis Ax1 when viewed from the small diameter portion 305. In this embodiment, the same diameter is used in the first large diameter portion 306A and the second large diameter portion 306B. As a result, on the inner peripheral surface 301 of the flexible externally toothed gear 3 , a “step difference” caused by local wear (larger than other parts) of the parts hit by the two ends in the width direction of the outer ring 421 is less likely to occur.

[0149] In this embodiment, in particular, the inner circumferential surface 301 of the flexible externally toothed gear 3 has a diameter other than the small diameter portion 305 that is equal to the large diameter portion 306. That is, in all parts of the main body 321 of the flexible externally toothed gear 3 except the small diameter part 305, the inner diameter thereof has the same diameter as the large diameter part 306. As a result, on the inner peripheral surface 301 of the flexible externally toothed gear 3 , a “step difference” caused by local wear (larger than other parts) of the parts hit by the two ends in the width direction of the outer ring 421 is less likely to occur.

[0150] Furthermore, as described above, the flexible externally toothed gear 3 is a cylindrical shape having an opening surface 35 on one side in the tooth line direction D1 of the external teeth 31. Here, the large diameter portion 306 is located at least on the opening surface 35 side relative to the small diameter portion 305. In short, the large diameter portion 306 is formed at least on the opening surface 35 side (the input side of the rotation axis Ax1) of the main body portion 321 of the flexible externally toothed gear 3 as viewed from the small diameter portion 305. In this embodiment, as described above, the large diameter portion 306 is provided on both sides of the small diameter portion 305, but the second large diameter portion 306B of the first large diameter portion 306A and the second large diameter portion 306B is located on the opening surface 35 side relative to the small diameter portion 305. Thus, on the opening surface 35 side where the collision of the outer race 421 is particularly strong due to the elastic deformation of the flexible externally toothed gear 3, it is possible to suppress the contact between the inner peripheral surface of the flexible externally toothed gear 3 and the outer race 421.

[0151] Moreover, in the present embodiment, the small diameter portion 305 is integrated with the flexible externally toothed gear 3. That is, the small diameter portion 305 is seamlessly and continuously formed integrally with the main body portion 321 of the flexible externally toothed gear 3. Thus, the positional accuracy of the small diameter portion 305 can be improved, and the small diameter portion 305 and the large diameter portion 306 can be easily formed.

[0152] Furthermore, the flexible externally toothed gear 3 is made of a material that is at least softer than the outer ring 421 of the bearing 42. That is, in the present embodiment, the outer ring 421 has a higher hardness than the inner peripheral surface 301 of the flexible externally toothed gear 3. In the present embodiment, in particular, the outer ring 421 is made of a material having high hardness and high toughness (toughness), and the flexible externally toothed gear 3 is made of a material having a lower hardness than the outer ring 421. Therefore, when the flexible externally toothed gear 3 and the outer ring 421 come into contact, the inner peripheral surface 301 of the flexible externally toothed gear 3 having a relatively low hardness is worn out preferentially over the outer ring 421. As a result, the wear of the outer ring 421 is suppressed.

[0153] That is, when the harmonic gear device 1 is in operation, when the flexible externally toothed gear 3 contacts the outer ring 421, the flexible externally toothed gear 3 having a relatively low surface hardness wears more actively than the outer ring 421. When two parts having different surface hardnesses (the flexible externally toothed gear 3 and the outer ring 421) contact, the wear of the relatively soft flexible externally toothed gear 3 is accelerated, thereby suppressing the wear of the relatively hard outer ring 421. Therefore, even if the intermediate portion 307 generated between the small diameter portion 305 and the large diameter portion 306 sometimes contacts the outer ring 421, it is difficult to generate a "step difference" in the outer ring 421 caused by the partial wear (larger than other portions) of the portion hit by the intermediate portion 307.

[0154] (4.4) Surface hardness

[0155] Next, the surface hardness of the inner peripheral surface 301 of the flexible externally toothed gear 3 and the outer ring 421 of the bearing 42 in the present embodiment will be described.

[0156] In the present embodiment, as described above, the hardness of the outer wheel 421 is higher than the inner circumferential surface 301 of the flexible external tooth gear 3. That is, the hardness of the surface of the outer wheel 421 is higher (harder) than the inner circumferential surface 301 of the flexible external tooth gear 3. The "hardness" mentioned in the present disclosure refers to the hardness of an object. The hardness of a metal is, for example, represented by the size of a depression that occurs when a steel ball is pressed with a fixed pressure. Specifically, as an example of the hardness of a metal, there are Rockwell hardness (HRC), Brinell hardness (HB), Vickers hardness (HV) or Shore hardness (Hs). In the present embodiment, unless otherwise specified, the hardness is represented by Vickers hardness (HV). As a way to increase (harden) the hardness of metal parts, there are, for example, alloying or heat treatment.

[0157] Specifically, the surface hardness of the inner circumferential surface 301 of the flexible external gear 3, which has a relatively lower hardness than the outer ring 421, is preferably HV (Vickers hardness) 450 or less. In the present embodiment, as an example, the surface hardness of the inner circumferential surface 301 of the flexible external gear 3 is selected within the range of HV400 or more and HV450 or less. The lower limit value of the surface hardness of the inner circumferential surface 301 of the flexible external gear 3 is not limited to HV400, and may be, for example, HV280, HV290, HV300, HV310, HV320, HV330, HV340, HV350, HV360, HV370, HV380, or HV390, etc. Similarly, the upper limit of the surface hardness of the inner peripheral surface 301 of the flexible externally toothed gear 3 is not limited to HV450, and may be, for example, HV460, HV470, HV480, HV490, HV500, HV510, HV520, HV530, HV540, or HV550.

[0158] In contrast, the surface hardness of the outer ring 421 (outer surface 424) having a relatively higher hardness than the inner surface 301 of the flexible external gear 3 is preferably HV700 or higher. In the present embodiment, as an example, the surface hardness of the outer ring 421 is selected within the range of HV700 or higher and HV770 or lower. The lower limit value of the surface hardness of the outer ring 421 is not limited to HV700, and may be, for example, HV600, HV610, HV620, HV630, HV640, HV650, HV660, HV670, HV680, or HV690. Similarly, the upper limit value of the surface hardness of the outer ring 421 is not limited to HV770, and may be, for example, HV780, HV790, HV800, HV810, HV820, HV830, HV840, HV850, HV860 or HV870.

[0159] By setting the surface hardness as described above, the hardness difference (difference in hardness) between the inner circumferential surface 301 of the flexible external gear 3 and the outer ring 421 becomes HV250 or more and HV370 or less. That is, the surface hardness of the outer ring 421 is set to be higher than the surface hardness of the inner circumferential surface 301 of the flexible external gear 3 by HV250 or more. In this way, there is a sufficient hardness difference between the inner circumferential surface 301 of the flexible external gear 3 and the outer ring 421, so that when the flexible external gear 3 and the outer ring 421 come into contact, the inner circumferential surface 301 of the flexible external gear 3 with relatively low hardness wears, while the wear of the outer ring 421 is suppressed.

[0160] The surface hardness of the flexible externally toothed gear 3 and the outer ring 421 does not necessarily need to be specified by Vickers hardness (HV), and the surface hardness of the inner teeth 21 and the outer teeth 31 may be specified by other hardnesses such as Rockwell hardness (HRC), Brinell hardness (HB) or Shore hardness (Hs). As an example, when the surface hardness is specified by Rockwell hardness, the surface hardness of the outer ring 421 is preferably selected within the range of HRC60 or more and HRC63 or less.

[0161] Furthermore, such a hardness difference is set not only between the flexible externally-toothed gear 3 and the outer wheel 421 , but also, for example, between the internal teeth 21 and the external teeth 31 .

[0162] (4.5) Tooth line trimming

[0163] Next, the tooth line trimming of the internal teeth 21 and the external teeth 31 in the present embodiment will be described.

[0164] As a premise, the inner teeth 21 are Figure 1B As shown, it has a tooth root 212 and a tooth top 213. The internal teeth 21 are provided on the inner peripheral surface of the rigid internal gear 2, so the tooth root 212 of the internal teeth 21 is equivalent to the inner peripheral surface of the rigid internal gear 2, and the tooth top 213 protrudes from the inner peripheral surface of the rigid internal gear 2 toward the inside (the center of the rigid internal gear 2).

[0165] On the other hand, the outer teeth 31 are Figure 1B As shown, it has a tooth root 312 and a tooth top 313. The external teeth 31 are provided on the outer peripheral surface of the flexible external gear 3 (the main body 321), so the tooth root 312 of the external teeth 31 is equivalent to the outer peripheral surface of the flexible external gear 3 (the main body 321), and the tooth top 313 protrudes outward from the outer peripheral surface of the flexible external gear 3 (the main body 321).

[0166] In the meshing position of the internal teeth 21 and the external teeth 31, the internal teeth 21 and the external teeth 31 mesh in a manner such that the tooth top 313 of the external teeth 31 is inserted between a pair of adjacent tooth tops 213 of the internal teeth 21. At this time, the tooth top 313 of the external teeth 31 faces the tooth root 212 of the internal teeth 21, and the tooth top 213 of the internal teeth 21 faces the tooth root 312 of the external teeth 31. And, it is ideal to ensure a small gap between the tooth root 212 of the internal teeth 21 and the tooth top 313 of the external teeth 31, and between the tooth root 312 of the external teeth 31 and the tooth top 213 of the internal teeth 21. In this state, the tooth surfaces of the internal teeth 21 and the external teeth 31 facing each other in the tooth thickness direction are in contact with each other, and power transmission is performed between the rigid internal gear 2 and the flexible external gear 3.

[0167] Furthermore, the internal teeth 21 have chamfered portions 211 at both ends in the tooth trace direction D1. The chamfered portions 211 are C surfaces that reduce the amount of protrusion of the internal teeth 21 toward both sides in the tooth trace direction D1, and are portions that basically do not contribute to the meshing of the internal teeth 21 and the external teeth 31. That is, the chamfered portions 211 of the internal teeth 21 do not contact the external teeth 31 at the meshing position of the internal teeth 21 and the external teeth 31. Similarly, the external teeth 31 have chamfered portions 311 at both ends in the tooth trace direction D1. The chamfered portions 311 are C surfaces that reduce the amount of protrusion of the internal teeth 21 toward both sides in the tooth trace direction D1, and are portions that basically do not contribute to the meshing of the internal teeth 21 and the external teeth 31. That is, the chamfered portions 311 of the external teeth 31 do not contact the internal teeth 21 at the meshing position of the internal teeth 21 and the external teeth 31.

[0168] Here, in the present embodiment, the internal teeth 21 of the rigid internal gear 2 have a tooth trace trimming portion 210. That is, the harmonic gear device 1 performs tooth trace trimming on at least the internal teeth 21. The tooth trace trimming portion 210 of the internal teeth 21 is provided at least one end portion in the tooth trace direction D1. In other words, the internal teeth 21 have a tooth trace trimming portion 210 at least one end portion in the tooth trace direction D1 of the internal teeth 21. In the present embodiment, the tooth trace trimming portion 210 is provided at both ends of the internal teeth 21 in the tooth trace direction D1.

[0169] Moreover, in the present embodiment, the external teeth 31 of the flexible external gear 3 also have a tooth trace trimming portion 310. That is, the harmonic gear device 1 performs tooth trace trimming not only on the internal teeth 21 but also on the external teeth 31. The tooth trace trimming portion 210 of the external teeth is provided at at least one end portion in the tooth trace direction D1. In other words, the external teeth 31 have a tooth trace trimming portion 310 at at least one end portion in the tooth trace direction D1 of the external teeth 31. In the present embodiment, the tooth trace trimming portion 310 is provided at both ends of the tooth trace direction D1 of the external teeth 31.

[0170] Thus, in the harmonic gear device 1 of the present embodiment, at least one of the internal teeth 21 and the external teeth 31 has the tooth trace trimming portion 210, 310. The tooth trace trimming portion 210, 310 can reduce the stress concentration caused by excessive tooth collision between the internal teeth 21 and the external teeth 31, and as a result, the tooth collision between the internal teeth 21 and the external teeth 31 can be improved. Therefore, foreign matter caused by defects or wear caused by the contact between the internal teeth 21 and the external teeth 31 is less likely to be generated, and the harmonic gear device 1 that is less likely to suffer from a decrease in reliability can be realized.

[0171] (5) Function

[0172] Next, the operation of the wave gear device 1 according to the present embodiment will be described in further detail.

[0173] In the harmonic gear device 1 without the small diameter portion 305 and the large diameter portion 306, especially when used for a long time, the contact portion of the inner peripheral surface 301 of the flexible externally toothed gear 3 with the outer race 421 of the bearing 42 of the harmonic generator 4 may be worn along with the rotation of the harmonic generator 4 embedded in the inner side of the flexible externally toothed gear 3. Due to the wear, a step may be generated in the portion corresponding to the both ends (corners) of the outer race 421 in the width direction (rotation axis Ax1 direction) of the inner peripheral surface 301 of the flexible externally toothed gear 3. In a state where such a step is generated, the outer race 421 repeatedly collides with the step along with the deformation (bending) of the flexible externally toothed gear 3, thereby causing damage to the flexible externally toothed gear 3 or the harmonic generator 4 (bearing 42), etc., and thus the reliability of the harmonic gear device 1 may be affected.

[0174] The reason for the generation of such a step difference is that the flexible externally toothed gear 3 frequently and repeatedly deforms elastically. That is, during one rotation of the cam 41 of the harmonic generator 4, the flexible externally toothed gear 3 repeats two rotations in one direction (for example, Figure 2A Therefore, the flexible external gear 3 is repeatedly elastically deformed at high speed by the high-speed rotation of the cam 41, and the "collision" of the harmonic generator 4 with the inner peripheral surface 301 of the flexible external gear 3 becomes stronger with the repetition of the elastic deformation.

[0175] More specifically, when the flexible externally toothed gear 3 is elastically deformed, the end of the flexible externally toothed gear 3 on the side of the opening surface 35 in the direction of the rotation axis Ax1 is deformed more than the end on the side of the bottom 322, and becomes a shape closer to an ellipse. Therefore, when the flexible externally toothed gear 3 is elastically deformed, the inner circumferential surface 301 of the main body 321 of the flexible externally toothed gear 3 is as shown in FIG. Figure 7As shown in FIG. 1 , the tapered surface 302 is inclined at an inclination angle θ1 relative to the rotation axis Ax1. The inclination angle θ1 of the tapered surface 302 changes with the elastic deformation of the flexible externally toothed gear 3, with the inclination direction toward the opening surface 35 side being positive (+) and the inclination direction toward the opposite side of the opening surface 35 being negative (-). That is, when the flexible externally toothed gear 3 is viewed from the opening surface 35 side, the inclination angle θ1 of the tapered surface 302 reaches a maximum in the positive direction at both ends in the long axis direction of the elliptical shape ( Figure 7 At both ends of the elliptical shape in the direction of the short axis, the inclination angle θ1 of the tapered surface 302 reaches a maximum in the negative direction ( Figure 7 Therefore, on the major axis side of the elliptical shape, a strong “collision” may occur at the corner on the side of the opening surface 35 of the outer ring 421 with the inner peripheral surface 301 of the flexible externally toothed gear 3, and on the minor axis side of the elliptical shape, a strong “collision” may occur at the corner on the opposite side to the opening surface 35 of the outer ring 421 with the inner peripheral surface 301 of the flexible externally toothed gear 3.

[0176] In contrast, in the harmonic gear device 1 of the present embodiment, the inner circumferential surface 301 of the flexible externally toothed gear 3 is provided with a small diameter portion 305 and a large diameter portion 306, and the small diameter portion 305, which is the contact portion with the outer race 421, is narrower than the outer race 421 in the tooth line direction D1 of the external teeth 31. Figure 7 As shown, even if the flexible externally toothed gear 3 is repeatedly elastically deformed at high speed, the large diameter portion 306 of the small diameter portion 305 and the large diameter portion 306 does not contact the outer peripheral surface 424 of the outer race 421. Therefore, on the inner peripheral surface 301 of the flexible externally toothed gear 3, it is difficult to generate a "step difference" caused by the local wear (larger than other portions) of the portions hit by the two ends in the width direction of the outer race 421.

[0177] Therefore, in the harmonic gear device 1 of the present embodiment, the generation of the "step difference" caused by the local wear of the inner peripheral surface 301 of the flexible externally toothed gear 3 is suppressed, and the malfunction caused by the step difference is unlikely to occur, and the harmonic gear device 1 that is unlikely to be reduced in reliability can be provided. In addition, the harmonic gear device 1 of the present embodiment is unlikely to be reduced in reliability even when used for a long time, and thus contributes to the improvement of the transmission efficiency, the extension of the life, and the high performance of the harmonic gear device 1.

[0178] Furthermore, the harmonic gear device 1 of the present embodiment has the function of reducing the bending moment and bending stress acting on the outer ring 421 of the bearing 42. That is, the bending moment and bending stress acting on the outer ring 421 are determined by the distance between the contact position with the outer ring 421 on the long axis side of the elliptical shape and the contact position with the outer ring 421 on the short axis side of the elliptical shape in the inner peripheral surface 301 of the flexible externally toothed gear 3 in the tooth trace direction D1. In the present embodiment, the small diameter portion 305, which is the contact portion with the outer ring 421, is narrower than the outer ring 421 in the tooth trace direction D1 of the external teeth 31, and therefore the distance is also shortened to be narrower than the outer ring 421. The shorter the distance, the smaller the bending moment and bending stress acting on the outer ring 421 of the bearing 42. Therefore, in the present embodiment, the bending moment and bending stress acting on the outer ring 421 of the bearing 42 can be reduced.

[0179] Furthermore, when the harmonic gear device 1 is driven, the load acting on the flexible externally toothed gear 3 from the bearing 42 of the harmonic generator 4 is applied to the inner peripheral surface 301 of the flexible externally toothed gear 3 at the contact point with the outer race 421, that is, the small diameter portion 305. In addition, the small diameter portion 305 is narrower than the outer race 421 in the tooth line direction D1 (direction parallel to the rotation axis Ax1) of the external teeth 31, so the application point is located on a straight line connecting the rotation groove 427 of the inner race 422 of the bearing 42, the rotating body 423, and the rotation groove 426 of the outer race 421 (in the radial direction). Therefore, it is difficult for unreasonable forces other than the radial direction to act on the bearing 42 of the harmonic generator 4, which contributes to the extension of the life of the bearing 42.

[0180] Furthermore, in the harmonic gear device 1 of the present embodiment, the small diameter portion 305 and the large diameter portion 306 are provided on the inner peripheral surface 301 of the flexible externally toothed gear 3, thereby being able to suppress damage to the flexible externally toothed gear 3 and the harmonic generator 4 due to "galling". Specifically, when the flexible externally toothed gear 3 and the harmonic generator 4 are assembled or at the initial stage of use of the harmonic gear device 1, localized adhesion wear called "galling" may occur at the contact portion between the flexible externally toothed gear 3 and the harmonic generator 4. According to the harmonic gear device 1 of the present embodiment, when the flexible externally toothed gear 3 and the harmonic generator 4 are assembled, the large diameter portion 306 (particularly the second large diameter portion 306B) of the inner peripheral surface 301 of the flexible externally toothed gear 3 functions as a guide portion for the harmonic generator 4 to fit into the small diameter portion 305, and the occurrence of "galling" can be suppressed. As a result, the growth of micro wear due to "galling" can be suppressed, and damage to the flexible externally toothed gear 3 and the harmonic generator 4 can be suppressed.

[0181] (6) Application examples

[0182] Next, for application examples of the harmonic gear device 1, the actuator 100, and the robot joint device 130 of the present embodiment, refer to Figure 8 to explain.

[0183] Figure 8 1 is a cross-sectional view showing an example of a robot 9 using the wave gear device 1 of the present embodiment. The robot 9 is a horizontal multi-joint robot, that is, a so-called Selective Compliance Assembly Robot Arm (SCARA) type robot.

[0184] like Figure 8 As shown, the robot 9 includes two robot joint devices 130 (including the wave gear device 1) and a link 91. The two robot joint devices 130 are provided at two joints of the robot 9. The link 91 connects the two robot joint devices 130. Figure 8 In the example of , the harmonic gear device 1 includes a top-hat type harmonic gear device rather than a cup type. That is, Figure 8 In the illustrated wave gear device 1 , a flexible externally toothed gear 3 formed in a top-hat shape is used.

[0185] (7) Manufacturing method

[0186] When manufacturing the wave gear device 1 of the present embodiment, particularly when manufacturing the outer ring 421 , it is preferable to take measures to avoid a decrease in strength due to the provision of the through hole H1 .

[0187] As an example, it is preferred to perform a surface processing step after the hole-forming step of forming the through-hole H1, wherein the surface processing step performs surface processing of the outer wheel 421 (especially the inner peripheral surface 425 that becomes the rotating surface). That is, it is preferred to retain compressive residual stress around the through-hole H1 in the outer wheel 421 to prevent the through-hole H1 from becoming the starting point of the rupture of the outer wheel 421. For this reason, it is preferred to form the through-hole H1 before performing surface processing steps such as quenching on the outer wheel 421 to retain the compressive residual stress caused by the heat treatment. Alternatively, after the heat treatment, shot peening, etc., may be performed on the through-hole H1 in the outer wheel 421 to modify and harden the surface by spraying small spherical injection materials, thereby improving the fatigue strength of the outer wheel 421.

[0188] Furthermore, it is more preferable to form a concave-convex surface by shot peening or barrel grinding after grinding the outer peripheral surface 424 of the outer ring 421 to remove the grinding traces (grinding traces). Thus, the occurrence of "stuck" at the contact portion between the flexible external tooth gear 3 and the harmonic generator 4 is further suppressed at the initial stage of use of the harmonic gear device 1.

[0189] (8) Modification

[0190] Implementation 1 is only one of various implementations of the present disclosure. Implementation 1 may be modified in various ways according to design, etc., as long as the purpose of the present disclosure can be achieved. Moreover, the drawings referred to in the present disclosure are all schematic drawings, and the size and thickness ratios of the components in the drawings do not necessarily reflect the actual size ratios. The following lists the modified examples of Implementation 1. The modified examples described below can be appropriately combined and applied.

[0191] The through hole H1 may be located at a position deviated from the center of the plurality of rotating bodies 423 in the direction parallel to the rotation axis Ax1 (tooth trace direction D1). As an example, the through hole H1 is arranged at a position deviated from the center of the rotating body 423 toward the opening surface 35, that is, at a position between the center of the rotating body 423 and the opening surface 35 in the tooth trace direction D1. According to this structure, there is an advantage that even if a large load is applied from the rotating body 423 in the radial direction to the member (here, the outer ring 421) in which the through hole H1 is formed, the load is unlikely to act on the periphery of the through hole H1, and cracks or the like starting from the through hole H1 are unlikely to occur.

[0192] Furthermore, the through hole H1 may be provided at multiple locations in a direction parallel to the rotation axis Ax1 (tooth line direction D1). Furthermore, the through hole H1 may have an opening area on the gap X1 side that is smaller than an opening area on the opposite side to the gap X1 in the radial direction. That is, in the (first) through hole H1 provided in the outer ring 421, the opening area of ​​the through hole H1 on the outer peripheral surface 424 side on the gap X1 side is smaller than the opening area of ​​the through hole H1 on the inner peripheral surface 425 side that is opposite to the gap X1. Thus, the pressure of the lubricant Lb1 supplied to the gap X1 through the through hole H1 can be increased.

[0193] Furthermore, the through holes H1 and H2 may be provided in both the outer ring 421 and the outer teeth 31 of the flexible externally toothed gear 3. In this case, the lubricant Lb1 in the space between the outer ring 421 and the inner ring 422 of the bearing 42 can be supplied to the gap X1 between the outer ring 421 and the flexible externally toothed gear 3 through the through hole H1. Furthermore, the lubricant Lb1 in the space between the outer teeth 31 and the inner teeth 21 can be supplied to the gap X1 between the outer ring 421 and the flexible externally toothed gear 3 through the through hole H2. Therefore, the lubricant Lb1 can be supplied to the gap X1 from both sides (inside and outside) in the radial direction. Here, it is preferred that the positions of the inner teeth 21 in the tooth line direction D1 are different in the (first) through hole H1 and the (second) through hole H2.

[0194] Furthermore, performing tooth profile modification on the internal teeth 21 and the external teeth 31 is not necessarily a configuration required for the harmonic gear device 1. For example, tooth profile modification may not be performed on at least one of the internal teeth 21 and the external teeth 31.

[0195] Furthermore, it is not necessary for the harmonic gear device 1 to ensure a distance of a predetermined value or more between the tracks of the plurality of rotating bodies 423 and the opening surface of the (first) through hole H1 provided in the outer ring 421 in the radial direction. That is, when the rotating body 423 is located at a position corresponding to the through hole H1, no gap is generated between the opening surface of the through hole H1 and the rotating body 423, and the through hole H1 is blocked by the rotating body 423.

[0196] Furthermore, it is not necessary for the harmonic gear device 1 to have each rotating body 423 supported at four points in the bearing 42 , and for example, each rotating body 423 may be supported at two points.

[0197] Furthermore, the harmonic 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. For example, even a top-hat type harmonic gear device 1 has a cylindrical flexible externally toothed gear 3 having an opening surface 35 on one side of the tooth line direction D1, similarly to the cup type. That is, the top-hat-shaped flexible externally toothed gear 3 has a flange portion at the end on one side of the rotation axis Ax1, and has an opening surface 35 at the end on the opposite side to the flange portion. Even a top-hat-shaped flexible externally toothed gear 3 has external teeth 31 at the end on the side of the opening surface 35, and the harmonic generator 4 is embedded in the end on the side of the opening surface 35.

[0198] Furthermore, the structure of the actuator 100 is not limited to the structure described in the first embodiment, and can be appropriately changed. For example, the connection structure between the input portion 103 and the cam 41 is not limited to the spline connection structure, and an Oldham coupling or the like can also be used. By using the Oldham coupling as the connection structure between the input portion 103 and the cam 41, the eccentricity between the rotation axis Ax1 on the input side and the harmonic generator 4 (cam 41) can be offset, and the eccentricity between the rigid internal gear 2 and the flexible external gear 3 can be offset. Furthermore, the cam 41 may not be movable along the rotation axis Ax1 relative to the input portion 103.

[0199] Furthermore, the application examples of the harmonic gear device 1, the actuator 100, and the robot joint device 130 of the present embodiment are not limited to the horizontal multi-joint robot described above, and may be, for example, an industrial robot other than the horizontal multi-joint robot or a robot other than industrial use. For example, industrial robots other than the horizontal multi-joint robot include a vertical multi-joint robot or a parallel-link robot. For example, robots other than industrial use include a household robot, a nursing robot, or a medical robot.

[0200] Furthermore, the bearing 42 is not limited to a deep groove ball bearing, and may be, for example, an angled ball bearing. Furthermore, the bearing 42 is not limited to a ball bearing, and may be, for example, a roller bearing, a needle bearing, a tapered roller bearing, or other roller bearings in which the rotating body 423 includes a "roller" that is not spherical. Even if the rotating body 423 is not spherical (spherical), the rotating body 423 generates a pressure difference by rotating the rotating body 423, and the rotating body 423 also functions as a pump structure.

[0201] Furthermore, the material of each component of the strain wave gear device 1 , the actuator 100 , or the robot joint device 130 is not limited to metal, and may be, for example, resin such as engineering plastic.

[0202] Furthermore, the lubricant Lb1 is not limited to liquid substances such as lubricating oil (oil), but may be a gel substance such as grease.

[0203] Moreover, the number and arrangement of the through holes H1 are not limited to the number and arrangement described in Embodiment 1. For example, the through holes H1 may be provided with 1, 2, or 4 or more. Furthermore, in the case where a plurality of through holes H1 are provided, the interval P1 between the plurality of through holes H1 may be a multiple of the interval P2 between the plurality of rotating bodies 423, and it is not necessary to arrange the plurality of through holes H1 at equal intervals.

[0204] Furthermore, the small diameter portion 305 may be formed independently of the flexible external gear 3. For example, by attaching a shaped member to a portion of the tooth line direction D1 of the external teeth 31 on the inner peripheral surface 301 of the flexible external gear 3 over the entire circumference, the inner peripheral surface of the member may be formed as the small diameter portion 305. Furthermore, the outer ring 421 may have the same degree of hardness as the inner peripheral surface 301 of the flexible external gear 3, or may have a lower hardness than the inner peripheral surface 301 of the flexible external gear 3.

[0205] Moreover, it is not essential to provide the large diameter portion 306 on both sides of the small diameter portion 305 in the tooth trace direction D1 of the external teeth 31. That is, in the tooth trace direction D1, the large diameter portion 306 may be provided only on one side (the opening surface 35 side or the side opposite to the opening surface 35) of the small diameter portion 305. Furthermore, it is not essential that the large diameter portion 306 is located at least on the opening surface 35 side relative to the small diameter portion 305, and the large diameter portion 306 may be located only on the side opposite to the opening surface 35 relative to the small diameter portion 305.

[0206] (Implementation Method 2)

[0207] The harmonic gear device 1B of this embodiment is as follows Fig. 9 As shown, the shape of the inner peripheral surface 301 of the flexible externally toothed gear 3 is different from that of the wave gear device 1 of Embodiment 1. Hereinafter, the same components as those of Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted as appropriate. Fig. 9 and Figure 5Similarly, for the equivalent Figure 1B The scope enlarges the schematic cross-section of the main parts.

[0208] In this embodiment, an intermediate portion 307 whose diameter gradually decreases toward the small diameter portion 305 in the tooth line direction D1 of the external teeth 31 is provided between the small diameter portion 305 and the large diameter portion 306. That is, in Embodiment 1, a stepped intermediate portion 307 having a height difference of 5 μm or more and 30 μm or less is generated between the small diameter portion 305 and the large diameter portion 306, and the diameter (inner diameter) of the inner peripheral surface 301 changes discontinuously in the intermediate portion 307. In contrast, in this embodiment, the diameter (inner diameter) of the inner peripheral surface 301 changes continuously in the intermediate portion 307 between the small diameter portion 305 and the large diameter portion 306.

[0209] Specifically, for example, the middle portion 307 is set as an inclined surface like a general tooth line trimming (drum processing or chamfering), thereby processing the inner peripheral surface 301 of the flexible external tooth gear 3 into a shape that is gradually cut away from the outer ring 421 along the tooth line direction D1. Fig. 9 In the example of , the diameter changes continuously from the first large diameter portion 306A to the small diameter portion 305 and further to the second large diameter portion 306B, so that the cross section of the inner peripheral surface 301 is curved. Here, it is preferred that the length of the tooth trace direction D1 of the small diameter portion 305 and the intermediate portion 307 is substantially consistent with the width (dimension) of the outer ring 421.

[0210] According to this structure, stress concentration is less likely to occur on the inner peripheral surface 301 of the flexible externally toothed gear 3 , and damage to the flexible externally toothed gear 3 is further less likely to occur.

[0211] As a modification of the second embodiment, in the tooth trace direction D1, the intermediate portion 307 on only one side (the side of the opening surface 35 or the side opposite to the opening surface 35) viewed from the small diameter portion 305 is configured so that the diameter gradually decreases toward the small diameter portion 305. At this time, in the intermediate portion 307 on the other side, the diameter (inner diameter) of the inner peripheral surface 301 changes discontinuously.

[0212] The structure of the second embodiment (including modified examples) can be appropriately combined with the structure (including modified examples) described in the first embodiment and applied.

[0213] (Summarize)

[0214] As described above, the first form of the harmonic gear device (1, 1A, 1B) includes a rigid internal gear (2), a flexible external gear (3) and a harmonic generator (4). The rigid internal gear (2) is an annular component having internal teeth (21). The flexible external gear (3) is an annular component having external teeth (31) and arranged on the inner side of the rigid internal gear (2). The harmonic generator (4) includes a non-circular cam (41) that is driven to rotate around a rotating shaft (Ax1) and a bearing (42) mounted on the outer side of the cam (41). The harmonic generator (4) is arranged on the inner side of the flexible external gear (3) to cause the flexible external gear (3) to bend. The harmonic gear device (1, 1A, 1B) deforms the flexible external gear (3) as the cam (41) rotates, causing a portion of the external teeth (31) to mesh with a portion of the internal teeth (21), so that the flexible external gear (3) rotates relative to the rigid internal gear (2) according to the difference in the number of teeth with the rigid internal gear (2). The portion of the inner peripheral surface (301) of the flexible external gear (3) that faces the outer wheel (421) of the bearing (42) includes a small diameter portion (305) that is narrower than the outer wheel (421) in the tooth line direction (D1) of the external teeth (31) and a large diameter portion (306) that is larger in diameter than the small diameter portion (305).

[0215] According to this embodiment, the inner circumferential surface (301) of the flexible externally toothed gear (3) contacts the outer wheel (421) only at the small diameter portion (305) in the portion facing the outer wheel (421) of the bearing (42), and does not contact the outer wheel (421) at the large diameter portion (306). In addition, the small diameter portion (305) in the inner circumferential surface (301) of the flexible externally toothed gear (3) that contacts the outer wheel (421) is narrower than the outer wheel (421) in the tooth line direction (D1) of the outer teeth (31). Therefore, the two ends (corners) in the width direction of the outer wheel (421) are difficult to contact the inner circumferential surface (301) of the flexible externally toothed gear (3), and the outer wheel (421) contacts the small diameter portion (305) in the portion that contacts the outer wheel (421). Therefore, it is difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42), and it is possible to provide a harmonic gear device (1, 1A, 1B) that is unlikely to cause a decrease in reliability.

[0216] A second aspect of the harmonic gear device (1, 1A, 1B) is a device according to the first aspect, wherein the small diameter portion (305) is integrated with the flexible externally toothed gear (3).

[0217] According to this form, the positional accuracy of the small diameter portion (305) can be improved, and the small diameter portion (305) and the large diameter portion (306) can be easily formed.

[0218] A third form of the harmonic gear device (1, 1A, 1B) is a harmonic gear device in the first or second form, wherein an intermediate portion (307) is provided between the small diameter portion (305) and the large diameter portion (306), the diameter of which gradually decreases toward the small diameter portion (305) in the tooth line direction (D1) of the external teeth (31).

[0219] According to this form, it is difficult for stress concentration to occur on the inner peripheral surface (301) of the flexible externally toothed gear (3), and it is even more difficult for the flexible externally toothed gear (3) to be damaged.

[0220] A fourth form of the harmonic gear device (1, 1A, 1B) is a harmonic gear device in any one of the first to third forms, wherein the large diameter portion (306) includes a first large diameter portion (306A) and a second large diameter portion (306B) located on both sides of the small diameter portion (305) in the tooth line direction (D1) of the external tooth (31).

[0221] According to this form, it is more difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42).

[0222] A fifth aspect of the harmonic gear device (1, 1A, 1B) is characterized in that in any one of the first to fourth aspects, the hardness of the outer ring (421) is higher than the inner peripheral surface (301) of the flexible externally toothed gear (3).

[0223] According to this form, it is more difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42).

[0224] A sixth aspect of the harmonic gear device (1, 1A, 1B) is a device according to any one of the first to fifth aspects, wherein the flexible externally toothed gear (3) is cylindrical and has an opening surface (35) on one side of a tooth line direction (D1) of an external tooth (31). The large diameter portion (306) is located at least on the opening surface (35) side relative to the small diameter portion (305).

[0225] According to this aspect, contact between the inner peripheral surface of the flexible externally toothed gear (3) and the outer race (421) can be suppressed on the side of the opening surface (35) where the collision of the outer race (421) is particularly strong due to elastic deformation of the flexible externally toothed gear (3).

[0226] A seventh aspect of the harmonic gear device (1, 1A, 1B) is a device according to any one of the first to sixth aspects, wherein a difference between the radius of the small diameter portion (305) and the radius of the large diameter portion (306) is 5 μm or more and 30 μm or less.

[0227] According to this form, it is more difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42).

[0228] The eighth embodiment of the harmonic gear device (1, 1A, 1B) is a device in which, in any one of the first to seventh embodiments, the dimension (L1) of the small diameter portion (305) in the tooth line direction (D1) of the external tooth (31) is equal to the diameter of the rotating body (423) of the bearing (42). More than 1 / 2 of.

[0229] According to this form, it is more difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42).

[0230] The ninth form of the robot joint device (130) comprises: a harmonic gear device (1, 1A, 1B) of any one of the first to eighth forms; a first component (131) fixed to a rigid internal gear (2); and a second component (132) fixed to a flexible external gear (3).

[0231] According to this form, it is difficult to generate a step difference on the inner peripheral surface (301) of the flexible external gear (3) due to contact with the bearing (42), and a robot joint device (130) that is unlikely to cause a decrease in reliability can be provided.

[0232] A gear component according to a tenth aspect is used as a flexible externally toothed gear (3) of a harmonic gear device (1, 1A, 1B) according to any one of the first to eighth aspects.

[0233] According to this form, it is difficult to generate a step difference on the inner peripheral surface (301) of the flexible externally toothed gear (3) due to contact with the bearing (42), and a gear component that is unlikely to cause a decrease in reliability can be provided.

[0234] The structures of the second to eighth aspects are not essential structures of the harmonic gear device (1, 1A, 1B) and can be omitted as appropriate.

[0235] [Explanation of Symbols]

[0236] 1, 1A, 1B: Harmonic gear device

[0237] 2: Rigid internal gear

[0238] 3: Flexible external gear (gear parts)

[0239] 4: Harmonic Generator

[0240] 21: Internal teeth

[0241] 31: External teeth

[0242] 35: Opening surface

[0243] 41: Cam

[0244] 42: Bearings

[0245] 130: Joint device for robots

[0246] 131: Component 1

[0247] 132: Component 2

[0248] 301: Inner circumference (of flexible external gear)

[0249] 305: Trails

[0250] 306: Large diameter part

[0251] 306A: 1st large diameter part

[0252] 306B: 2nd large diameter part

[0253] 421: Outer wheel

[0254] 423: Rotating body

[0255] Ax1: Rotation axis

[0256] D1: Tooth line direction

[0257] L1: Dimension (small diameter part)

[0258] The diameter of the rotating body

Claims

1. A harmonic gear device, comprising: A ring-shaped rigid internally toothed gear having internal teeth; an annular flexible external gear having external teeth and arranged inside the rigid internal gear; as well as The harmonic generator includes a non-circular cam that is driven to rotate about a rotating shaft, and a bearing mounted on the outside of the cam, and is arranged on the inside of the flexible externally toothed gear to cause the flexible externally toothed gear to bend. The flexible externally-toothed gear is deformed as the cam rotates, so that a portion of the external teeth meshes with a portion of the internal teeth, and the flexible externally-toothed gear rotates relative to the rigid internally-toothed gear in accordance with a difference in the number of teeth between the flexible externally-toothed gear and the rigid internally-toothed gear, characterized in that: A portion of the inner peripheral surface of the flexible externally toothed gear that faces the outer ring of the bearing includes a small diameter portion narrower than the outer ring in the tooth line direction of the external teeth and a large diameter portion larger in diameter than the small diameter portion.

2. The harmonic gear device according to claim 1, characterized in that: The small diameter portion is integrated with the flexible externally-toothed gear.

3. The harmonic gear device according to claim 1 or 2, characterized in that: An intermediate portion whose diameter gradually decreases toward the small diameter portion in the tooth trace direction of the external teeth is provided between the small diameter portion and the large diameter portion.

4. The harmonic gear device according to claim 1 or 2, characterized in that: The large diameter portion includes a first large diameter portion and a second large diameter portion located on both sides of the small diameter portion in a tooth trace direction of the external teeth.

5. The harmonic gear device according to claim 1 or 2, characterized in that: The outer ring has a harder surface than the inner peripheral surface of the flexible externally-toothed gear.

6. The harmonic gear device according to claim 1 or 2, characterized in that: The flexible externally toothed gear is in the shape of a cylinder having an opening surface on one side of the tooth line direction of the external teeth. The large diameter portion is located at least on the opening surface side relative to the small diameter portion.

7. The harmonic gear device according to claim 1 or 2, characterized in that: There is a difference of 5 μm or more and 30 μm or less between the radius of the small diameter portion and the radius of the large diameter portion.

8. The harmonic gear device according to claim 1 or 2, characterized in that: The dimension of the small diameter portion in the tooth line direction of the external teeth is equal to or larger than 1 / 2 of the diameter of the rolling element of the bearing.

9. A joint device for a robot, characterized in that include: The harmonic gear device according to claim 1 or 2; A first member fixed to the rigid internal gear; as well as The second member is fixed to the flexible externally toothed gear.

10. A gear component, characterized in that: It is used as the flexible externally-toothed gear of the harmonic gear device described in claim 1 or 2.

Images