Wave gear device

Abstract

The present invention provides a wave gear device. The wave generator includes: a first member having a first inner circumferential surface surrounding a central axis; a second member having an outer circumferential surface opposing the first inner circumferential surface, the second member being connected to an input member; a slider that allows the first member to slide radially relative to the second member while rotating together with the second member; and a rolling bearing located radially outside the first member and radially inside the flexible externally toothed gear, wherein one of two members selected from the first member, the second member, and the slider has a first opposing surface, and the other has a second opposing surface opposing the first opposing surface, the first opposing surface having a contact surface capable of contacting the second opposing surface and a separation surface located farther from the second opposing surface than the contact surface.

Description

Technical Field

[0001] The present invention relates to a wave gear device. Background Art

[0002] Conventionally, wave gear devices comprising a rigid internal gear and a flexible external gear are known. Such wave gear devices are primarily used as speed reducers. For example, Japanese Utility Model Registration No. 2535495 discloses a conventional speed reducer. The speed reducer disclosed in Japanese Utility Model Registration No. 2535495 comprises an annular rigid member; an annular flexible member disposed inside the rigid member; and a wave generator embedded within the flexible member, causing the flexible member to bend radially and engage with the rigid member at multiple locations, with these engagement locations moving circumferentially.

[0003] The wave generator described in Japanese Utility Model Registration No. 2535495 includes a cam component. This cam component comprises an outer cylindrical component, an intermediate cylindrical component slidably inserted into the inner side of the outer cylindrical component in the axial direction, and an inner cylindrical component slidably inserted into the inner side of the intermediate cylindrical component in the axial direction. These outer, intermediate, and inner cylindrical components are combined to form a so-called Oldham coupling structure. The reducer described in Japanese Utility Model Registration No. 2535495, by having this Oldham coupling structure, can absorb eccentricity in the power input portion.

[0004] Patent Document 1: Japanese Utility Model Registration No. 2535495

[0005] However, in conventional technology, lubricant is applied to reduce friction between the components that make up the cam assembly. When the components come into contact through the lubricant, viscous resistance is generated between them. Consequently, the viscous resistance between the opposing surfaces of the lubricant can sometimes inhibit separation of the opposing surfaces. If the viscous resistance increases, separation between the opposing surfaces may not occur smoothly, making it difficult to absorb eccentricity. Summary of the Invention

[0006] An object of the present invention is to provide a technology for satisfactorily absorbing eccentricity on the input side in a wave generator.

[0007] To address the above-mentioned issues, a wave gear device comprises: a wave generator that rotates about a central axis; a flexible externally toothed gear, cylindrical in shape, surrounding the central axis and positioned radially outward from the wave generator, which is bent into a non-perfect circular shape by the wave generator; and an internally toothed gear, positioned radially outward from the flexible externally toothed gear and partially meshing with the flexible externally toothed gear. The flexible externally toothed gear and the internally toothed gear rotate relative to each other due to their different tooth numbers. The rotation of the wave generator changes the radial length of the flexible externally toothed gear, and the meshing position of the flexible externally toothed gear and the internally toothed gear changes circumferentially about the central axis. The wave generator comprises: a first member having a first inner circumferential surface surrounding the central axis; a second member having an outer circumferential surface opposing the first inner circumferential surface, the second member being connected to an input member; a slider that allows the first member to slide radially relative to the second member while rotating together with the second member; and a rolling bearing positioned radially outward from the first member and radially inward from the flexible externally toothed gear. One of two members selected from the first member, the second member, and the slider has a first opposing surface, and the other has a second opposing surface opposing the first opposing surface. The first opposing surface includes a contact surface capable of contacting the second opposing surface and a separation surface located farther from the second opposing surface than the contact surface.

[0008] In the first embodiment of the wave gear device, the first member, the second member, or the slider have a first opposing surface and a second opposing surface that face each other, and the first opposing surface has a separation surface that is spaced apart from the second opposing surface. Therefore, when lubricant is interposed between the first and second opposing surfaces and they come into contact, the separation surface reduces the viscous resistance between the two surfaces caused by the lubricant. This allows the second member to slide smoothly in the radial direction relative to the first member. Consequently, eccentricity on the input side can be effectively absorbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a longitudinal sectional view of the wave gear device according to the first embodiment.

[0010] Figure 2 The diagram shows a perspective view (upper stage) and an exploded perspective view (lower stage) of the Oldham coupling viewed from one axial side.

[0011] Figure 3 It is a perspective view showing the Oldham coupling viewed from the other side in the axial direction.

[0012] Figure 4 It is a perspective view showing the cam viewed from the other side in the axial direction.

[0013] Figure 5It is a perspective view showing a cam according to the second embodiment.

[0014] Figure 6 1 and 2 are a perspective view (upper stage) and an exploded view (lower stage) showing a cam according to a third embodiment.

[0015] Figure 7 This is an enlarged longitudinal sectional view showing the inner portion of the cam according to the third embodiment.

[0016] Figure 8 This is an enlarged longitudinal sectional view showing the inner portion of the cam according to the fourth embodiment.

[0017] Figure 9 It is a perspective view showing a cam according to a fifth embodiment.

[0018] Figure 10 It is a perspective view showing a cam according to a sixth embodiment.

[0019] Figure 11 It is a perspective view showing a cam according to a seventh embodiment.

[0020] Figure 12 It is a perspective view showing a cam according to an eighth embodiment.

[0021] Figure 13 It is a diagram showing a cam according to a ninth embodiment.

[0022] Figure 14 It is a side view showing a wheel hub according to a tenth embodiment.

[0023] Figure 15 It is a perspective view showing a plurality of modified examples of the slider. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The components described in these embodiments are merely illustrative, and the scope of the present invention is not limited thereto. In the accompanying drawings, the dimensions and numbers of various components may be exaggerated or simplified as necessary for ease of understanding.

[0025] In the following description, directions parallel to the central axis of the wave gear device are referred to as "axial directions," directions perpendicular to the central axis of the wave gear device are referred to as "radial directions," and directions along an arc centered on the central axis of the wave gear device are referred to as "circumferential directions." However, the term "parallel directions" also includes substantially parallel directions. Furthermore, the term "perpendicular directions" also includes substantially perpendicular directions.

[0026] <1. First embodiment>

[0027] Figure 11 is a longitudinal sectional view of the wave gear device 1 according to the first embodiment. The wave gear device 1 includes a rigid internally toothed gear 11 , a flexible externally toothed gear 13 , and a wave generator 20 .

[0028] The wave gear device 1 changes the speed of input rotary power by utilizing the differential (relative rotation) between a rigid internally toothed gear 11 and a flexible externally toothed gear 13. The wave gear device 1 is incorporated into, for example, the joints of a small robot. It functions as a speed reduction device that reduces the power received from a motor.

[0029] The rigid internal gear 11 is Figure 1 The rigid internally toothed gear 11 is an annular member centered on the central axis C shown. The rigidity of the rigid internally toothed gear 11 is higher than the rigidity of the flexible tooth portion 133 of the flexible externally toothed gear 13, described later. Therefore, the rigid internally toothed gear 11 is substantially rigid. The rigid internally toothed gear 11 has a plurality of internal teeth 111 on its inner circumferential surface. The plurality of internal teeth 111 are arranged at regular intervals along the circumferential direction. The rigid internally toothed gear 11 is fixed, for example, to the frame of the device in which the wave gear device 1 is mounted.

[0030] The flexible externally toothed gear 13 is cup-shaped and comprises a flat plate portion 141 and a cylindrical main body portion 131. The main body portion 131 has a flexible tooth portion 133 on its outer circumference at one axial end. The flexible tooth portion 133 has external teeth 135 (flexible external teeth) on its outer circumference. The flexible tooth portion 133 is located radially inward of the rigid internally toothed gear 11. The flat plate portion 141 is connected to the other axial end of the main body portion 131.

[0031] The flat plate portion 141 is a portion extending radially perpendicular to the central axis C. The flat plate portion 141 includes a diaphragm portion 143 and a circular plate portion 145 in the shape of an annular plate. The diaphragm portion 143 is located closer to the main body portion 131 than the circular plate portion 145, and is located radially outward of the circular plate portion 145. The axial wall thickness of the diaphragm portion 143 is thinner than that of the circular plate portion 145. The diaphragm portion 143 is annular. The circular plate portion 145 is located radially inward of the diaphragm portion 143 and has a certain wall thickness. An output shaft for extracting the decelerated power is fixed in the center of the circular plate portion 145.

[0032] The wave generator 20 includes a ball bearing 21 and an Oldham coupling 23. The ball bearing 21 is embedded inside the flexible tooth portion 133 of the flexible externally toothed gear 13. The Oldham coupling 23 is attached to the inner ring of the ball bearing 21. The ball bearing 21 is an example of a rolling bearing located radially outside the Oldham coupling 23 (specifically, the cam 30 described later) and radially inside the flexible externally toothed gear 13 (specifically, the flexible tooth portion 133).

[0033] The crosshead coupling 23 of the wave generator 20 is connected to the input member 90. The input member 90 rotates about the center axis C. The wave generator 20 rotates about the center axis C at the rotational speed of the input member 90. The flexible tooth portion 133 of the flexible external gear 13 is cylindrical and surrounds the center axis C. It is arranged radially outside the wave generator 20 and is bent into a non-circular shape by the rotating wave generator 20. The rigid internal gear 11 is arranged radially outside the flexible external gear 13 and partially meshes with the flexible tooth portion 133 of the flexible external gear 13. The rigid internal gear 11 and the flexible external gear 13 rotate relative to each other due to the difference in the number of teeth. The radial length of the flexible external gear 13 changes due to the rotation of the wave generator 20, and the meshing position of the flexible external gear 13 and the rigid internal gear 11 changes in the circumferential direction about the center axis C.

[0034] <Structure of the Oldham coupling>

[0035] Figure 2 1 and 2 , which are a perspective view (upper stage) and an exploded perspective view (lower stage) of the Oldham coupling 23 as viewed from one axial side. Figure 3 1 is a perspective view showing the Oldham coupling 23 viewed from the other side in the axial direction. Figure 4 1 is a perspective view showing the cam 30 viewed from the other side in the axial direction.

[0036] The crosshead coupling 23 has a cam 30, a hub 40 and a slider 50. The cam 30 is annular. Figure 1 As shown, the cam 30 is embedded in the inner ring of the ball bearing 21. The cam 30 has a first inner peripheral surface 31 surrounding the central axis C. The first inner peripheral surface 31 is formed with a through hole 311 that penetrates the cam 30 in the axial direction. Figure 1 and Figure 4 As shown, the cam 30 has a side surface 33 (third side surface) facing the other side in the axial direction.

[0037] like Figure 1 and Figure 2 As shown, the hub 40 includes a cylindrical portion 41 and an opposing portion 43. The cylindrical portion 41 is cylindrical and surrounds the central axis C. An input member 90 is inserted into the inner side of the cylindrical portion 41. The cylindrical portion 41 is coupled to the input member 90 via a key. In other words, the wave generator 20 is coupled to the input member 90 via the hub 40. Rotation of the input member 90 causes the hub 40 to rotate about the central axis C.

[0038] The cylindrical portion 41 of the hub 40 has an outer circumferential surface 411 facing radially outward. The cylindrical portion 41 is inserted into the through-hole 311 of the cam 30. As a result, the outer circumferential surface 411 faces the first inner circumferential surface 31 of the cam 30. The outer diameter of the cylindrical portion 41 is slightly smaller than the inner diameter of the through-hole 311 of the cam 30. Consequently, a slight radial gap is formed between the first inner circumferential surface 31 and the outer circumferential surface 411.

[0039] The facing portion 43 of the hub 40 is a flange-shaped portion extending radially outward from the other axial end of the cylindrical portion 41. Figure 1 and Figure 2 As shown, the opposing portion 43 of the hub 40 has a side surface 45 (fourth side surface) facing one side in the axial direction.

[0040] The slider 50 is a component for allowing the cam 30 to slide radially relative to the hub 40 while rotating together with the hub 40 about the central axis C. The slider 50 includes an annular slider body 51. The slider body 51 is axially located between the cam 30 and the opposing portion 43 of the hub 40. The slider body 51 has a second inner circumferential surface 511 surrounding the central axis C. The second inner circumferential surface 511 is formed with a through-hole 513 that axially penetrates the slider body 51. The cylindrical portion 41 of the hub 40 is inserted into the through-hole 513. As a result, the second inner circumferential surface 511 and the outer circumferential surface 411 of the cylindrical portion 41 are radially opposed to each other.

[0041] The outer diameter of the cylindrical portion 41 of the hub 40 is slightly smaller than the inner diameter of the through hole 513 of the slider 50. Therefore, a small gap in the radial direction is formed between the outer peripheral surface 411 and the second inner peripheral surface 511.

[0042] The slider body 51 has a side surface 53 (first side surface) facing one axial direction. A pair of first protrusions 54, 54 are provided on the side surface 53, protruding axially to one side. The pair of first protrusions 54, 54 are located radially outward from the center axis C and are disposed at opposing positions across the center axis C.

[0043] The side surface 53 (first side surface) of the slider body 51 faces the side surface 33 (third side surface) of the cam 30. A pair of sliding grooves 55, 55 (first sliding grooves) are provided on the side surface 33, recessed axially toward one side. These sliding grooves 55, 55 are positioned at opposing positions across the center axis C and extend radially parallel to each other. The sliding grooves 55 are provided in a one-to-one correspondence with the first protrusions 54. The circumferential width of the first protrusions 54 is slightly smaller than the width of the corresponding sliding grooves 55.

[0044] like Figure 1As shown, the slider body 51 has a side surface 57 (second side surface) facing the other axial side. A pair of second protrusions 58, 58 are provided on the side surface 57, protruding toward the other axial side. The pair of second protrusions 58, 58 are located radially outward from the center axis C and are provided at opposing positions across the center axis C.

[0045] The side surface 57 (second side surface) of the slider body 51 faces the side surface 45 (fourth side surface) of the opposing portion 43 in the hub 40. A pair of sliding grooves 59, 59 (second sliding grooves) are provided on the side surface 45 and are recessed toward the other axial side. Figure 2 In the illustrated example, the sliding grooves 59 are notches extending axially through the opposing portion 43. The pair of sliding grooves 59, 59 are positioned at opposing positions across the center axis C and extend radially parallel to each other. The sliding grooves 59 are provided in a one-to-one correspondence with the second protrusions 58. The circumferential width of the second protrusions 58 is slightly smaller than the groove width of the corresponding sliding groove 59.

[0046] The first protrusion 54 of the slider 50 is inserted into the corresponding sliding groove 55 of the cam 30. As a result, the cam 30 and the slider 50 are circumferentially engaged, and the cam 30 rotates together with the slider 50. Furthermore, the first protrusion 54, while being guided by the sliding groove 55, slides slightly radially inside the sliding groove 55. Therefore, the cam 30 can slide slightly relative to the slider 50 in the direction in which the sliding groove 55 extends. The axial length of the first protrusion 54 is shorter than the axial depth of the corresponding sliding groove 55. When the first protrusion 54 of the slider 50 is inserted into the sliding groove 55 of the cam 30, the side surface 53 of the slider 50 contacts the side surface 33 of the cam 30.

[0047] In addition, the second protrusion 58 of the slider 50 is inserted into the corresponding sliding groove 59. As a result, the wheel hub 40 and the slider 50 are engaged in the circumferential direction. That is, when the wheel hub 40 rotates about the center axis C, the slider 50 also rotates about the center axis C. In addition, the second protrusion 58 is guided by the sliding groove 59 while sliding slightly in the radial direction inside the sliding groove 55. Therefore, the cam 30 can slide slightly relative to the slider 50 in the direction in which the sliding groove 59 extends. The axial length of the second protrusion 58 is shorter than the axial depth of the corresponding sliding groove 59. When the second protrusion 58 of the slider 50 is inserted into the sliding groove 59 of the wheel hub 40, the side surface 57 of the slider 50 contacts the side surface 45 of the wheel hub 40.

[0048] The direction in which the pair of sliding grooves 59, 59 extends is perpendicular to the direction in which the pair of sliding grooves 55, 55 extends. Therefore, the cam 30 can be slightly slidably moved in all radial directions relative to the hub 40 via the slider 50. Alternatively, the first protrusion 54 may be provided on the side surface 33 of the cam 30, and the sliding groove 55 may be provided on the side surface 53 of the slider 50. Alternatively, the second protrusion 58 may be provided on the side surface 45 of the hub 40, and the sliding groove 59 may be provided on the side surface 57 of the slider 50.

[0049] The first inner circumferential surface 31 of the cam 30 is provided with three inner grooves 35 that are recessed radially outward. The number of inner grooves 35 is not limited to three and may be one, two, or four or more. The inner grooves 35 are annular and extend circumferentially. The three inner grooves 35 are spaced apart in the axial direction.

[0050] like Figure 4 As shown, a pair of sliding grooves 55 are provided so as to radially cross the side surface 33. Therefore, each sliding groove 55 is connected to the inner groove 35 that is closest to the other side in the axial direction among the three inner grooves 35.

[0051] Lubricant is present between the mutually opposing surfaces of the cam 30, the hub 40, and the slider 50. For example, lubricant is present between the first inner circumferential surface 31 of the cam 30 and the outer circumferential surface 411 of the hub 40. Therefore, the surface of the first inner circumferential surface 31, excluding the inner groove 35, serves as a contact surface with the outer circumferential surface 411 of the hub 40 via the lubricant. Meanwhile, the inner surface of the inner groove 35 serves as a separation surface located farther from the outer circumferential surface 411 than the contact surface. The first inner circumferential surface 31 is an example of a first opposing surface, and the outer circumferential surface 411 is an example of a second opposing surface.

[0052] The inner groove 35 interrupts contact between the first inner circumferential surface 31 and the outer circumferential surface 411. This reduces the viscous resistance caused by the lubricant between the first inner circumferential surface 31 and the outer circumferential surface 411. This allows the first inner circumferential surface 31 to be easily separated radially from the outer circumferential surface 411, allowing the hub 40 to slide smoothly radially relative to the cam 30.

[0053] like Figure 2 As shown, four protrusions 531 are provided on the side surface 53 of the slider 50, slightly protruding toward one side in the axial direction. Each protrusion 531 has a flat contact surface 533 facing toward one side in the axial direction. The contact surface 533 is located axially toward the other side of the end of the first protrusion 54 on one side. The four contact surfaces 533 are located in the same plane perpendicular to the axial direction and are arranged at equal intervals in the circumferential direction around the central axis C. In other words, the four contact surfaces 533 are separated in the circumferential direction.

[0054] The side surface 53 of the slider 50 has a separation surface 535. The separation surface 535 is located around the contact surface 533 on the side surface 53 and is positioned axially away from the side surface 33 of the cam 30 relative to the contact surface 533. Thus, by providing mutually separated contact surfaces 533 on the side surface 53, the separation surface 535 is provided between circumferentially adjacent contact surfaces 533, 533. The side surface 53 is an example of a first opposing surface. Furthermore, the side surface 33 of the cam 30 that opposes the side surface 53 is an example of a second opposing surface.

[0055] The side surface 53 of the slider 50 contacts the side surface 33 of the cam 30 at four contact surfaces 533. Furthermore, while the four contact surfaces 533 are in contact with the side surface 33, the separation surface 535 is separated from the side surface 33. Therefore, if lubricant is present between the side surfaces 53 and 33, the separation surfaces 535 interrupt the contact between the side surfaces 53 and 33 via the lubricant. This reduces the viscous resistance between the side surfaces 53 and 33 caused by the lubricant, allowing the slider 50 to slide smoothly in the radial direction relative to the cam 30. Consequently, the Oldham coupling 23 can effectively absorb eccentricity of the input member 90.

[0056] The side surface 53 of the slider 50 contacts the side surface 33 of the cam 30 at four separate contact surfaces 533. This prevents the side surface 53 from tilting in the axial direction while in contact with the side surface 33.

[0057] Although not shown, multiple protrusions 531 may be provided on the side surface 57 on the other axial side of the slider 50, similar to the side surface 53. Providing multiple protrusions 531 on the side surface 57 allows for a separation surface to be formed on the side surface 57 that is away from the side surface 45 of the hub 40. This reduces the viscous resistance caused by the lubricant between the side surface 57 and the side surface 45. This allows the hub 40 to slide smoothly in the radial direction relative to the slider 50.

[0058] <2. Second embodiment>

[0059] In the following description, elements having the same functions as those already described are denoted by the same reference numerals or reference numerals with additional alphabetical characters, and detailed descriptions thereof may be omitted.

[0060] Figure 5 The sliding groove 55a provided on the side surface 33 of the cam 30a of the second embodiment has a wall portion 551 on the radial inner side, which is similar to the Figure 4The cam 30 shown is different. The cam 30a has three inner grooves 35 like the cam 30. Among the three inner grooves 35, the inner groove 35 located furthest to the other side in the axial direction is annular like the other inner grooves 35 and is not connected to the sliding groove 55a.

[0061] When the cam 30a is applied to the Oldham coupling 23, similarly to the case of the cam 30, the inner groove 35 reduces the viscous resistance caused by the lubricant between the first inner circumferential surface 31 and the outer circumferential surface 411 of the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30.

[0062] <3. Third embodiment>

[0063] Figure 6 1 and 2 are a perspective view (upper stage) and an exploded view (lower stage) showing a cam 30 b according to a third embodiment. Figure 7 : is an enlarged longitudinal sectional view showing the inner portion of the cam 30b of the third embodiment. Figure 6 As shown, the cam 30b includes a ring member 37 and a cam body 39. The ring member 37 is annular and has a third inner circumferential surface 371 surrounding the central axis C. The cam body 39 is annular and has an annular recess 391 at its center on the other axial side, which is recessed toward one axial side. The annular recess 391 is where the ring member 37 is mounted.

[0064] The cam body 39 has a side surface 392 facing the other axial side. Side surface 392 constitutes the side surface 33 of the cam 30b that faces the side surface 53 of the slider 50. The outer diameter of the ring member 37 is, for example, slightly larger than the inner diameter of the annular recess 391. The ring member 37 is retained in the cam body 39 by, for example, being press-fitted into the annular recess 391. Alternatively, the ring member 37 may be secured to the cam body 39 using another component.

[0065] The inner diameter of the ring member 37 is substantially the same as the inner diameter of the cam body portion 39 on the axial side closer to the annular recess 391. Figure 6 and Figure 7 As shown, the third inner peripheral surface 371 of the ring member 37 and the inner peripheral surface 393 of the cam body portion 39 together constitute the first inner peripheral surface 31 of the cam 30 b.

[0066] like Figure 6 As shown, the cam 30b has an inner groove 35. The inner groove 35 is annular and extends in the circumferential direction. Figure 7As shown, the shape of the inner groove 35 when cut along a plane perpendicular to the axial direction (hereinafter referred to as the "cross-sectional shape") is a triangular shape whose width gradually narrows radially outward. Specifically, the inner groove 35 is formed by the inclined surface 373 of the ring member 37 and the inclined surface 395 of the cam body 39. The inclined surface 373 is provided at one axial end of the third inner circumferential surface 371 of the ring member 37 and is inclined radially outward toward the one axial end. The inclined surface 395 of the cam body 39 is provided at the other axial end of the inner circumferential surface 393 and is inclined radially outward toward the other axial end.

[0067] The ring member 37 has an inclined surface 375. The inclined surface 375 is provided at the end portion on the other axial side of the third inner circumferential surface 371 and is inclined radially outward toward the other axial side. The inclined surfaces 373 and 375 are symmetrical about a plane passing through the axial center of the ring member 37 and perpendicular to the central axis C. Therefore, when the ring member 37 is mounted on the cam body 39, either of the inclined surfaces 373 and 375 can face the cam body 39.

[0068] Even when the cam 30b is used in the Oldham coupling 23, as with the cam 30, the inner groove 35 reduces the viscous resistance caused by the lubricant between the first inner circumferential surface 31 and the outer circumferential surface 411 of the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30b.

[0069] like Figure 7 As shown, the axial width of the ring member 37 is smaller than the width of the annular recess 391 of the cam body 39. Therefore, when the ring member 37 is mounted in the annular recess 391, the end face of the ring member 37 on the other axial side is located radially further away from the side face 392 of the cam body 39. Consequently, in the Oldham coupling 23, the end face of the ring member 37 is spaced away from the side face 53 of the slider 50. This separation of the end face of the ring member 37 from the slider 50 reduces the contact area between the cam 30b and the slider 50. This reduces the viscous resistance of the lubricant between the cam 30b and the slider 50. Consequently, the hub 40 can slide smoothly in the radial direction relative to the cam 30b.

[0070] <4. Fourth embodiment>

[0071] Figure 8 This is an enlarged longitudinal sectional view showing the inner portion of the cam 30 c according to the fourth embodiment.

[0072] The cam 30c of the fourth embodiment has a ring member 37 and a cam body 39 in the same manner as the cam 30b of the third embodiment. However, the ring member 37 has an inner groove 35 on the third inner peripheral surface 371. In addition, the cam body 39 has an inner groove 35 on the inner peripheral surface 393. Therefore, Figure 8 As shown, the cam 30c has three inner grooves 35. In the case of the cam 30c, since it has a plurality of inner grooves 35, the viscous resistance of the lubricant between the cam 30 and the hub 40 is further reduced compared to the cam 30b.

[0073] <5. Fifth embodiment>

[0074] Figure 9 30d is a perspective view showing a cam 30d according to the fifth embodiment. Figure 4 Cam 30d has the same structure as cam 30 shown in FIG. However, cam 30d differs from cam 30 in that it has four inner grooves 35a extending in the axial direction on its first inner circumferential surface 31. These four inner grooves 35a are circumferentially spaced evenly apart. The width of each inner groove 35a is the same as that of the sliding groove 55. Furthermore, the cross-section of each inner groove 35a is a generally rectangular shape with rounded corners on both sides of the bottom.

[0075] When the cam 30d is used in the Oldham coupling 23, similarly to the cam 30, the plurality of inner grooves 35a reduce the viscous resistance of the lubricant between the cam 30d and the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30d.

[0076] <6. Sixth embodiment>

[0077] Figure 10 The cam 30e of the sixth embodiment is shown in a perspective view. The cam 30e has an inner groove 35b extending in the axial direction on the first inner peripheral surface 31. Figure 9 The cam 30e is similar to the cam 30d shown in FIG. However, the cam 30e has eight inner grooves 35b arranged at equal intervals in the circumferential direction. In addition, the cross-sectional shape of the inner grooves 35b is a quadrilateral.

[0078] When the cam 30e is used in the Oldham coupling 23, similarly to the cam 30d, the plurality of inner grooves 35b reduce the viscous resistance of the lubricant between the cam 30e and the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30e.

[0079] <7. Seventh embodiment>

[0080] Figure 11 The cam 30f has an inner groove 35c extending in the axial direction on the first inner peripheral surface 31. Figure 9 The cam 30d shown is similar to the cam 30f. However, the cam 30f has 16 inner grooves 35c arranged at equal intervals in the circumferential direction. In addition, the cross-sectional shape of the inner groove 35c is triangular. The inner groove 35c is smaller than the inner groove 35c. Figure 9 The inner groove 35a shown or Figure 10 The inner groove 35b is shown to be shallow.

[0081] When the cam 30f is used in the Oldham coupling 23, similarly to the case of the cam 30d, the plurality of inner grooves 35b reduce the viscous resistance caused by the lubricant between the cam 30f and the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30f.

[0082] <8. Eighth embodiment>

[0083] Figure 12 The cam 30g is a perspective view showing the cam 30g of the eighth embodiment. The cam 30g has a plurality of inner grooves 35d having a triangular cross-sectional shape on the first inner peripheral surface 31. Figure 11 The cam 30f shown is similar. However, the direction in which the inner groove 35d of the cam 30g extends has two components, circumferential and axial. That is, the inner groove 35d extends in both the circumferential and axial directions.

[0084] When the cam 30g is used in the Oldham coupling 23, similarly to the cam 30f, the plurality of inner grooves 35c reduce the viscous resistance caused by the lubricant between the cam 30g and the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30g.

[0085] <9. Ninth embodiment>

[0086] Figure 13 : is a diagram showing a cam 30h according to a ninth embodiment. Figure 6 The cam 30b shown is similar. Specifically, the cam 30h has two ring members 37, 37 and a cam body portion 39a. The ring member 37 is connected to the cam body portion 39a. Figure 6 and Figure 7 The cam body 39a is an annular member. Two ring members 37, 37 are mounted inside the cam body 39a. The cam 30h has an annular inner groove 35 extending circumferentially on the first inner circumferential surface 31. The inner groove 35 is formed by the two ring members 37, 37 being adjacent in the axial direction and is located at the boundary between the ring members 37, 37. Specifically, the inner groove 35 is formed by an inclined surface 375 of the ring member 37 on one axial side and an inclined surface 373 of the ring member 37 on the other axial side.

[0087] When the cam 30h is used in the Oldham coupling 23, similarly to the cam 30b, the inner groove 35 reduces the viscous resistance caused by the lubricant between the cam 30h and the hub 40. Therefore, the hub 40 can slide smoothly in the radial direction relative to the cam 30h.

[0088] <10. Tenth embodiment>

[0089] Figure 14 It is a side view showing a hub 40a according to a tenth embodiment.

[0090] The hub 40a has three outer grooves 47 on its outer peripheral surface 411. The three outer grooves 47 are provided at intervals in the axial direction. The outer grooves 47 are annular circumferential grooves extending in the circumferential direction.

[0091] In the Oldham coupling 23, the two outer grooves 47 on the axial side of the three outer grooves 47 are located opposite the first inner circumferential surface 31 of the cam 30. In other words, the inner surfaces of the two outer grooves 47 serve as separation surfaces of the Oldham coupling 23 that are separated from the first inner circumferential surface 31. Therefore, similar to the inner grooves 35, the two outer grooves 47 on the axial side can reduce the viscous resistance caused by the lubricant between the outer circumferential surface 411 and the first inner circumferential surface 31.

[0092] Furthermore, in the Oldham coupling 23, the outer groove 47 located furthest to the other side in the axial direction of the three outer grooves 47 faces the second inner circumferential surface 511 of the slider 50. Specifically, the inner surface of the outer groove 47 located furthest to the other side in the axial direction serves as a separation surface in the Oldham coupling 23 that is away from the second inner circumferential surface 511. Therefore, the outer groove 47 located furthest to the other side in the axial direction reduces the viscous resistance between the outer circumferential surface 411 and the second inner circumferential surface 511 caused by the lubricant.

[0093] <11. Modifications>

[0094] Figure 15 It is a perspective view showing a plurality of modified examples of the slider 50 . Figure 15 The shapes of the protrusions included in the five sliders 50 a to 50 e shown are different from the protrusion 531 included in the slider 50 .

[0095] Specifically, slider 50a has four protrusions 531a. Each protrusion 531a has a contact surface 533a with a constant circumferential width. Slider 50b has four protrusions 531b arranged at equal intervals in the circumferential direction. Protrusions 531b have substantially circular contact surfaces 533b. Slider 50c has six protrusions 531c. Protrusions 531c have rectangular contact surfaces 533c. Contact surfaces 533b and 533c are much smaller than contact surface 533 and smaller than the surface of first protrusion 54 facing the other axial side. By reducing the size of contact surface 533 in this way, the contact area between side surface 53 and side surface 33 of cam 30 can be reduced. Consequently, the viscous resistance between side surface 53 and side surface 33 caused by the lubricant can be reduced.

[0096] Slider 50d has six protrusions 531d. The contact surfaces 533d of protrusions 531d are elongated and extend circumferentially. Slider 50e has one protrusion 531e and two protrusions 531f. The contact surface 533e of protrusion 531e is longer and larger in area than the contact surface 533f of protrusion 531f in the circumferential direction.

[0097] In any of the sliders 50a to 50e, the separation surface 535 is formed by providing the protrusions 531a to 531f on the side surface 53. Therefore, regardless of which of the sliders 50a to 50e is used in the Oldham coupling 23, the separation surface 535 reduces the viscous resistance between the side surface 53 and the side surface 33 caused by the lubricant, as in the case of the slider 50.

[0098] While the present invention has been described in detail above, the foregoing description is illustrative in all respects and the present invention is not limited thereto. It will be understood that numerous variations not illustrated are contemplated without departing from the scope of the present invention. The various structures described in the above embodiments and variations may be appropriately combined or omitted as long as they do not conflict with each other.

[0099] Industrial applicability

[0100] The present invention can be utilized in a wave gear device.

Claims

1. A wave gear device comprising: a wave generator that rotates about a central axis; a flexible externally toothed gear in a cylindrical shape surrounding a central axis, located radially outside the wave generator, and bent into a non-perfect circular shape by the wave generator; and an internal gear disposed radially outside the flexible external gear and partially meshing with the flexible external gear; The flexible external gear and the internal gear rotate relative to each other due to the difference in the number of teeth. By the rotation of the wave generator, the radial length of the flexible externally toothed gear changes, and the meshing position of the flexible externally toothed gear and the internally toothed gear changes in the circumferential direction around the central axis. The wave generator has: a first component having a first inner peripheral surface surrounding a central axis; a second member having an outer peripheral surface opposite to the first inner peripheral surface and connected to the input member; a slider that allows the first member to rotate together with the second member while being able to slide in a radial direction relative to the second member; and a rolling bearing located radially outside the first component and radially inside the flexible externally toothed gear, One of two members selected from the first member, the second member, and the slider has a first opposing surface, and the other has a second opposing surface facing the first opposing surface. The first opposing surface includes a contact surface capable of contacting the second opposing surface and a separation surface located farther from the second opposing surface than the contact surface. At least one of the first inner peripheral surface and the outer peripheral surface has the contact surface and the separation surface.

2. The wave gear device according to claim 1, wherein: The separation surface includes an inner surface of a groove provided in at least one of the first inner peripheral surface and the outer peripheral surface.

3. The wave gear device according to claim 2, wherein: One or more of the grooves may include an annular groove extending in a circumferential direction.

4. The wave gear device according to claim 3, wherein: One or more of the grooves include a plurality of the annular grooves.

5. The wave gear device according to any one of claims 2 to 4, wherein: The first component has: one or more ring members in an annular shape having a third inner peripheral surface surrounding the central axis; and a cam body portion that holds the one or more ring members, The first inner circumferential surface includes the third inner circumferential surface of the one or more ring members.

6. The wave gear device according to claim 5, wherein: The one or more grooves include grooves provided on the third inner peripheral surface and extending in the axial direction or the circumferential direction.

7. The wave gear device according to claim 5, wherein: The one or more ring members include two ring members adjacent to each other in the axial direction, The one or more grooves include grooves located at boundaries of the two ring members.

8. The wave gear device according to any one of claims 1 to 4, wherein: The slider has: a slider body portion located axially between the first member and the second member, having a second inner peripheral surface surrounding the central axis and facing the outer peripheral surface of the second member; a first protrusion protruding from a position away from the central axis toward one side in the axial direction on a first side surface of the slider body; and a second convex portion, which protrudes from a position away from the central axis toward the other axial side on the second side of the slider body portion in the axial direction; The first component has a first sliding groove extending in the radial direction and for the first protrusion to be inserted into. The second component has: an opposing portion that is opposed to the slider main body on the other axial side of the slider main body; and The second sliding groove is provided in the opposing portion and extends along a radial direction intersecting with the first sliding groove, and is for the second protrusion to be inserted into.

9. The wave gear device according to claim 8, wherein: The first member has a third side surface facing the first side surface of the slider in the axial direction, and at least one of the first side surface and the third side surface has the contact surface and the separation surface.

10. The wave gear device according to claim 8, wherein The second member has a fourth side surface facing the second side surface of the slider in the axial direction, and at least one of the second side surface and the fourth side surface has the contact surface and the separation surface.

11. The wave gear device according to claim 9, wherein: The contact surface includes at least three surfaces separated from each other.

12. The wave gear device according to claim 8, wherein: The first inner circumferential surface of the first member has an axial width greater than the axial width of the second inner circumferential surface of the slider body, and at least one of the first inner circumferential surface and the outer circumferential surface has the contact surface and the separation surface.

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