JP7629309B2 - Reduction gear and bicycle - Google Patents

Description

The present invention relates to a reduction gear and a bicycle.

A conventional drive module has a first drive shaft (for example, see JP 2003-233663 A). The first drive shaft is provided for manual driving of the drive module. A second drive shaft is also provided. The second drive shaft is non-rotatably connected to a rotor of an electric auxiliary drive. The electric auxiliary drive further has a stator. In this way, the rotor can be connected to a wave gear device via the second drive shaft. The wave gear device has an inner bush, a wave generator, and an outer bush.

Special table 2018-507140 publication

However, in conventional drive modules, the strain wave gear device and the electric auxiliary drive device are arranged at a distance from each other in the axial direction. This results in a large axial length of the drive module (reduction gear).

The present invention was made in consideration of the above problems, and its purpose is to provide a reduction gear that can have a relatively small axial length.

An exemplary reduction gear of the present invention includes a motor and a reducer. The reducer reduces the rotational speed of the motor. The motor includes a motor body, a rotating shaft that rotates around a central axis, a first bearing, and a second bearing. The reducer includes a wave generator, a flexible member, and an annular ring member. The wave generator has an outer diameter that varies depending on the circumferential position and rotates around the central axis. The flexible member has a flexible cylindrical portion with which the wave generator contacts from the radial inside. The cylindrical portion contacts the ring member from the radial inside. The flexible member rotates relative to the ring member in response to the rotation of the wave generator. The motor body includes a rotor connected to the rotating shaft. The wave generator is connected to the rotating shaft at a position different from the position at which the rotor is connected. The first bearing is disposed on the opposite side of the wave generator with respect to the rotor, and rotatably supports the rotating shaft. The second bearing is disposed radially inside the cylindrical portion and rotatably supports the rotating shaft.

An exemplary bicycle of the present invention has the above-mentioned reduction gear, pedals, a crankshaft, and a sprocket. The crankshaft passes axially through the rotating shaft of the reduction gear and is driven by the pedal force. The output shaft of the reduction gear is connected to the sprocket.

According to an exemplary embodiment of the present invention, a reduction gear and a bicycle can be provided that have a relatively small axial length.

FIG. 1 is a vertical cross-sectional view showing a reduction gear transmission according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the motor according to the first embodiment. FIG. 3 is a cross-sectional view showing the reducer according to the first embodiment. FIG. 4 is a perspective view showing a rotating shaft of the motor according to the first embodiment. FIG. 5 is an enlarged vertical cross-sectional view showing a portion of the reduction gear transmission according to the first embodiment. FIG. 6A is an enlarged vertical cross-sectional view showing a seal portion of the reduction gear transmission according to the first embodiment. FIG. 6B is an enlarged vertical cross-sectional view showing another example of the seal portion of the reduction gear transmission according to embodiment 1. FIG. 6C is an enlarged longitudinal sectional view showing still another example of the seal portion of the reduction gear transmission according to the first embodiment. FIG. 6D is an enlarged vertical cross-sectional view showing still another example of the seal portion of the reduction gear transmission according to embodiment 1. FIG. 7 is a plan view showing the non-circular cam of the reduction gear transmission according to the first embodiment. FIG. 8 is a diagram showing a bicycle according to a second embodiment of the present invention. FIG. 9 is a vertical cross-sectional view showing a reduction gear transmission mounted on a bicycle according to the second embodiment.

Below, exemplary embodiments of the present invention will be described with reference to the drawings. Note that in the drawings, the same or equivalent parts are given the same reference symbols and descriptions will not be repeated. Also, in the drawings, the X-axis, Y-axis, and Z-axis of a three-dimensional orthogonal coordinate system are appropriately indicated for ease of understanding.

In this specification, the direction parallel to the central axis AX of the reduction gear is referred to as the "axial direction AD", the direction perpendicular to the central axis AX is referred to as the "radial direction RD", and the direction along the arc centered on the central axis AX is referred to as the "circumferential direction CD". Note that "parallel direction" includes directions that are approximately parallel, and "orthogonal direction" includes directions that are approximately orthogonal. Furthermore, "planar view" refers to viewing an object from the axial direction AD.

(Embodiment 1)
A reduction gear transmission SR according to a first embodiment of the present invention will be described with reference to Figures 1 to 7. Figure 1 is a longitudinal sectional view showing the reduction gear transmission SR according to the first embodiment. Figure 2 is a transverse sectional view showing a motor 100 of the reduction gear transmission SR. Figure 2 corresponds to a cross section taken along line II-II in Figure 1. Figure 3 is a transverse sectional view showing a reducer 200 of the reduction gear transmission SR. Figure 3 corresponds to a cross section taken along line III-III in Figure 1.

The reduction gear SR shown in FIG. 1 reduces the rotational speed. The rotational speed indicates, for example, the number of rotations per unit time. Specifically, the reduction gear SR converts a rotational motion of a first rotational speed into a rotational motion of a second rotational speed that is lower than the first rotational speed.

As shown in FIG. 1, the reduction gear SR has a motor 100 and a reducer 200. The motor 100 drives the reducer 200. The reducer 200 reduces the rotational speed of the motor 100. Specifically, the reducer 200 converts the rotational motion of the motor 100 at a first rotational speed into rotational motion at a second rotational speed that is lower than the first rotational speed.

The motor 100 has a motor body 10, a rotating shaft 25 that rotates around a central axis AX, a substantially annular first bearing 30, and a substantially annular second bearing 35. The central axis AX is an imaginary line that passes through the center of the rotating shaft 25 along the longitudinal direction of the rotating shaft 25. The motor body 10 rotates the rotating shaft 25. As shown in Figures 1 and 2, the motor body 10 has a rotor 15.

As shown in Figures 1 and 3, the reducer 200 has a rigid internal gear 40, a flexible external gear 50, and a wave generator 60.

The flexible external gear 50 is an example of a "flexible member." The rigid internal gear 40 is an example of an "annular member."

The wave generator 60 has an outer diameter that varies depending on the position in the circumferential direction CD. The wave generator 60 rotates around the central axis AX. In the example of FIG. 3, the wave generator 60 is approximately elliptical. The wave generator 60 is a mechanism that flexibly deforms the flexible external gear 50. The flexible external gear 50 has a cylindrical portion 51. The cylindrical portion 51 is flexible. The cylindrical portion 51 is approximately cylindrical. The rigid internal gear 40 is approximately annular. In the example of FIG. 3, the rigid internal gear 40 is approximately annular. The cylindrical portion 51 of the flexible external gear 50 contacts the rigid internal gear 40 from the inside in the radial direction RD. The flexible external gear 50 rotates relative to the rigid internal gear 40 in response to the rotation of the wave generator 60.

As shown in FIG. 1, in the motor 100, the rotor 15 of the motor body 10 is connected to the rotating shaft 25. Specifically, the rotor 15 is fixed to the rotating shaft 25. On the other hand, in the reducer 200, the wave generator 60 is connected to the rotating shaft 25 at a position different from the position where the rotor 15 is connected. Specifically, the wave generator 60 is fixed to the rotating shaft 25. The first bearing 30 of the motor 100 rotatably supports the rotating shaft 25. The first bearing 30 is arranged on the opposite side of the rotor 15 to the wave generator 60. In other words, the first bearing 30 is arranged on the opposite side of the rotor 15 to the wave generator 60. The second bearing 35 of the motor 100 rotatably supports the rotating shaft 25. The second bearing 35 is arranged on the radially inner side RD of the cylindrical portion 51 of the flexible external gear 50. In other words, the second bearing 35 of the motor 100 is arranged inside the reducer 200. Therefore, according to the first embodiment, the length of the reduction gear SR in the axial direction AD can be made smaller than when the second bearing 35 of the motor 100 is disposed outside the reduction gear 200. In other words, the length of the reduction gear SR in the axial direction AD can be made relatively small.

Specifically, in the first embodiment, the second bearing 35 of the motor 100 is disposed on the opposite side of the rotor 15 with the wave generator 60 in between. In other words, the second bearing 35 is disposed on the opposite side of the rotor 15 with respect to the wave generator 60. Therefore, according to the first embodiment, the motor body 10 can be disposed closer to the reducer 200 in the axial direction AD. As a result, the length of the reduction gear SR in the axial direction AD can be further reduced.

In addition, in the first embodiment, the rotating shaft 25 of the motor 100 is preferably hollow. According to this preferred example, a mechanical element such as a shaft can be disposed inside the rotating shaft 25. As a result, the range of applications of the reduction gear SR is expanded. Specifically, the rotating shaft 25 has an internal space SP that is approximately cylindrical. Note that the rotating shaft 25 does not have to be hollow.

Next, the motor 100 will be described in detail with reference to Figures 1 and 2. As shown in Figure 1, the motor 100 further includes a fixed member R1, a spacer R10, a spacer R11, and a fixed member R2. The motor body 10 further includes a stator 11 and a flange portion 18.

The stator 11 is the fixed element of the motor 100. The stator 11 is disposed around the central axis AX. Specifically, the stator 11 has a stator core 12, an insulator 13, and a number of coils 14.

The stator core 12 is disposed around the central axis AX. The stator core 12 is disposed around the central axis AX and is generally annular. The stator core 12 is formed, for example, of laminated steel plates in which thin electromagnetic steel sheets are laminated in the axial direction AD. The insulator 13 electrically insulates the stator core 12 from the coil 14. The insulator 13 is formed of an insulating material. The insulator 13 covers at least a portion of the stator core 12. The insulator 13 is disposed in a generally annular shape around the central axis AX. The insulator 13 may be formed of multiple separate members or may be formed of a single member. The coil 14 is formed by winding a conductor around the stator core 12 via the insulator 13.

As shown in FIG. 2, the stator core 12 has a roughly annular core back 121 and multiple teeth 122. The multiple teeth 122 protrude inward from the core back 121 in the radial direction RD. The coils 14 are formed by winding a conductor around the teeth 122. The multiple coils 14 are arranged along the circumferential direction CD. As an example, the stator core 12 has 18 slots. Therefore, in the example of FIG. 2, the stator 11 has 18 coils 14.

Returning to FIG. 1, the rotor 15 is the rotor of the motor 100. That is, the rotor 15 rotates around the central axis AX. The rotor 15 is connected to the rotating shaft 25. Therefore, when the rotor 15 rotates, the rotating shaft 25 rotates. That is, the rotating shaft 25 rotates together with the rotor 15. The rotor 15 is disposed around the central axis AX. The rotor 15 is disposed inside the stator 11 in the radial direction RD. That is, the motor 100 is an inner rotor type motor. Note that the motor 100 may be an outer rotor type motor.

Specifically, the rotor 15 has a rotor core 16 and a magnet 17. The magnet 17 is, for example, a permanent magnet. For example, the rotor 15 may have a plurality of magnets 17 arranged in the circumferential direction CD, or may have a single magnet 17 in a substantially annular shape. The rotor core 16 is, for example, made of laminated steel plates in which electromagnetic steel plates are laminated in the axial direction AD. The magnet 17 is fixed to the outer surface of the rotor core 16 in the radial direction RD. In other words, the motor 100 is an SPM (Surface Permanent Magnet) motor. The magnet 17 may be fixed inside the rotor core 16. In other words, the motor 100 may be a so-called IPM (Interior Permanent Magnet) motor. The magnet 17 and the stator core 12 face each other with a gap in the radial direction RD.

The rotor 15 is sandwiched between a substantially annular fixed member R2 and a substantially annular spacer R11 and positioned in the axial direction AD.

2, the rotor 15 has N magnets 17. Therefore, the number of poles of the motor 100 is "N". N is an integer equal to or greater than 2. In the example of FIG. 2, N=20. The rotor 15 has a first connection portion 161. Specifically, the rotor core 16 is disposed around the central axis AX. The rotor core 16 is disposed around the central axis AX and has a substantially annular shape. The rotor core 16 has a first connection portion 161. The first connection portion 161 is connected to the rotating shaft 25. Specifically, the first connection portion 161 has N first recesses 162 connected in the circumferential direction CD. Each of the N first recesses 162 is recessed toward the outside in the radial direction RD and extends along the axial direction AD.

The N first recesses 162 each face the N magnets 17 in the radial direction RD. The shapes of the N first recesses 162 are set so that the magnetic fields of the N magnets 17 are optimized. The "optimized magnetic field" refers to a magnetic field that can most smoothly rotate the rotor 15 relative to the stator 11. The N first recesses 162 are provided on the inner peripheral surface of the rotor core 16.

On the other hand, the rotating shaft 25 has N convex portions 250. The N convex portions 250 protrude outward in the radial direction RD. The N convex portions 250 are connected in the circumferential direction CD. The N convex portions 250 are provided on the outer circumferential surface of the rotating shaft 25. The N convex portions 250 fit into the N first concave portions 162, respectively. As a result, the stator core 12 is connected to the rotating shaft 25. In other words, the stator 11 is connected to the rotating shaft 25. The rotating shaft 25 having the convex portions 250 and the rotor core 16 having the first concave portions 162 form a spline.

Returning to FIG. 1, the flange portion 18 holds the stator 11. Specifically, the flange portion 18 holds the stator core 12. The flange portion 18 is arranged in a substantially annular shape around the central axis AX. Specifically, the flange portion 18 has a first flange portion 19 and a second flange portion 20. The first flange portion 19 is substantially annular. The second flange portion 20 is substantially annular. The first flange portion 19 covers the stator 11 from one side in the axial direction AD. The second flange portion 20 covers the stator 11 and the rotor 15 from the other side in the axial direction AD. The first flange portion 19 and the second flange portion 20 hold the stator 11 by sandwiching the stator 11 in the axial direction AD. As a result, the stator 11 is fixed to the flange portion 18. Specifically, the stator core 12 is fixed to the flange portion 18.

The first bearing 30 is disposed at one end in the axial direction AD of the rotating shaft 25. The first bearing 30 supports the rotating shaft 25 rotatably relative to the stator 11 and the flange portion 18. The first bearing 30 is, for example, a ball bearing. The first bearing 30 has an inner ring 31, a plurality of balls 32, and an outer ring 33. The inner ring 31 is fixed to the outer peripheral surface of the rotating shaft 25. The plurality of balls 32 are interposed between the inner ring 31 and the outer ring 33 and are arranged along the circumferential direction CD. The outer ring 33 is fixed to the inner peripheral surface in the radial direction RD of the first flange portion 19.

A substantially annular spacer R11 is disposed between the inner ring 31 of the first bearing 30 and the rotor 15. A substantially annular spacer R10 is disposed on the opposite side of the inner ring 31 from the spacer R11. The inner ring 31 is then sandwiched between the spacer R11 and the fixed member R1 via the spacer R10, and positioned in the axial direction AD.

The second bearing 35 is disposed at the other end of the rotating shaft 25 in the axial direction AD. The second bearing 35 supports the rotating shaft 25 rotatably relative to the stator 11 and the flange portion 18. The second bearing 35 is, for example, a ball bearing. The second bearing 35 has an inner ring 36, a plurality of balls 37, and an outer ring 38. The inner ring 36 is fixed to the outer peripheral surface of the rotating shaft 25. The plurality of balls 37 are interposed between the inner ring 36 and the outer ring 38 and are arranged along the circumferential direction CD. The outer ring 38 is fixed to the output rotor 55, which will be described later. Although not shown in FIG. 1, in reality, the inner ring 36 is separated from the output rotor 55 with a gap therebetween.

Next, the details of the reducer 200 and the rotating shaft 25 will be described with reference to Figures 3 and 4. As shown in Figure 3, the wave generator 60 has a second connection part 66. Specifically, the wave generator 60 has a wave bearing 61 and a non-circular cam 65. The wave bearing 61 is flexible. The wave bearing 61 is located inside the cylindrical part 51 of the flexible external gear 50 in the radial direction RD. The non-circular cam 65 expands in an annular shape centered on the central axis AX. In the example of Figure 3, the non-circular cam 65 is approximately elliptical. The wave bearing 61 is arranged along the outer circumferential surface of the non-circular cam 65 and is bent in an approximately elliptical shape. The non-circular cam 65 has a second connection part 66.

The second connection portion 66 connects to the rotating shaft 25. Specifically, the second connection portion 66 has N second recesses 67 that are continuous in the circumferential direction CD. Each of the N second recesses 67 is recessed outward in the radial direction RD and extends along the axial direction AD. The N second recesses 67 are provided on the inner circumferential surface of the non-circular cam 65. In a plan view, the shape of the second connection portion 66 is substantially the same as the shape of the first connection portion 161 shown in FIG. 2.

The N second recesses 67 correspond to the N first recesses 162 shown in FIG. 2. The N second recesses 67 face the N first recesses 162 in the axial direction AD. In other words, the first recesses 162 and the second recesses 67 are aligned in a straight line along the axial direction AD.

Meanwhile, the N convex portions 250 of the rotating shaft 25 are fitted into the N second concave portions 67, respectively. As a result, the non-circular cam 65 is connected to the rotating shaft 25. In other words, the wave generator 60 is connected to the rotating shaft 25. The rotating shaft 25 functions as the input shaft of the reducer 200. The rotating shaft 25 having the convex portions 250 and the non-circular cam 65 having the second concave portions 67 form a spline.

Figure 4 is a perspective view showing the rotating shaft 25 of the motor 100. As shown in Figure 4, on the rotating shaft 25, N convex portions 250 extend along the axial direction AD. The N convex portions 250 are also arranged at intervals in the circumferential direction CD. As long as the first recess 162 (Figure 2) and the second recess 67 (Figure 3) fit into the convex portions 250, each convex portion 250 may be separated in the axial direction AD or may be continuous in the axial direction AD.

The rotating shaft 25 further has fixed member arrangement portions 251, 252, 253, and 254. Each of the fixed member arrangement portions 251 to 254 passes through N convex portions 250 in the circumferential direction CD. The fixed member arrangement portions 251 to 254 are arranged at intervals in the axial direction AD. Each of the fixed member arrangement portions 251 to 254 is recessed toward the inside in the radial direction RD. The fixed members R1, R2, R3, and R4 in FIG. 1 are arranged in the fixed member arrangement portions 251, 252, 253, and 254, respectively.

As described above with reference to Figures 2 to 4, according to the first embodiment, the protrusion 250 provided on the rotating shaft 25 extends along the axial direction AD, so that the protrusion 250 fits into both the first recess 162 of the rotor 15 and the second recess 67 of the wave generator 60. Therefore, the rotational force of the motor 100 can be transmitted to the reducer 200 by the rotating shaft 25 with a simple structure.

Next, the sealing structure between the motor body 10 and the reduction gear 200 will be described with reference to Figures 5, 6A, and 7. Figure 5 is an enlarged longitudinal cross-sectional view of a portion of the reduction gear SR in Figure 1. Note that, for simplicity, the fixing members R3 and R4 in Figure 1 are omitted in Figure 5.

Grease is present inside the reducer 200 shown in FIG. 5. In other words, the inside of the reducer 200 is filled with grease. For example, the reducer 200 has spaces SP1, SP2, and SP3. Spaces SP1, SP2, and SP3 are filled with grease. Therefore, it is necessary to prevent the grease in the reducer 200 from entering the motor body 10. This is because, particularly in embodiment 1, the motor body 10 and the reducer 200 are close to each other in the axial direction AD.

The second flange portion 20 of the motor body 10 is located between the reducer 200 and the stator 11 and rotor 15 of the motor body 10. The second flange portion 20 faces the stator 11 and rotor 15 of the motor body 10 in the axial direction AD. The second flange portion 20 also faces the rigid internal gear 40, flexible external gear 50, and wave generator 60 of the reducer 200 in the axial direction AD.

Specifically, the second flange portion 20 has a first ring portion 191 and a second ring portion 192. The first ring portion 191 is substantially annular. The first ring portion 191 faces the rigid internal gear 40 in the axial direction AD. The first ring portion 191 is fixed to the rigid internal gear 40 from the axial direction AD. The first ring portion 191 is in contact with the rigid internal gear 40 from the axial direction AD.

The second ring portion 192 is located radially inward in the RD than the first ring portion 191. The second ring portion 192 is a substantially annular flat plate member, and extends from the first ring portion 191 inward in the axial direction AD. The second ring portion 192 faces the rigid internal gear 40, the flexible external gear 50, and the wave generator 60 in the axial direction AD. The second ring portion 192 also faces the stator 11 and the rotor 15 in the axial direction AD. The second ring portion 192 is spaced apart from the rotor 15 in the axial direction AD. The second ring portion 192 extends radially inward in the RD from the first ring portion 191. The tip of the second ring portion 192 faces the radial direction RD with a gap from the rotating shaft 25.

The reduction gear SR further has a seal portion 90. The seal portion 90 seals between the reduction gear 200 and the motor body 10 on the radially outer side RD of the rotating shaft 25. Therefore, according to the first embodiment, it is possible to prevent the grease of the reduction gear 200 from entering the motor body 10.

Figure 6A is an enlarged longitudinal cross-sectional view of the seal portion 90. That is, Figure 6 shows an enlarged view of region A in Figure 5. As shown in Figure 6A, the seal portion 90 has a labyrinth structure. Specifically, the seal portion 90 has a first labyrinth portion 91 and a second labyrinth portion 92. The first labyrinth portion 91 is provided on the axial direction AD side of the non-circular cam 65. The first labyrinth portion 91 has an uneven shape. On the other hand, the second labyrinth portion 92 is provided at the tip portion of the second ring portion 192 in the radial direction RD. The second labyrinth portion 92 faces the first labyrinth portion 91 in the axial direction AD. The second labyrinth portion 92 has an uneven shape.

The uneven shape of the first labyrinth portion 91 meshes with the uneven shape of the second labyrinth portion 92 to form a seal between the reducer 200 and the motor body 10.

Figure 7 is a plan view showing the non-circular cam 65. As shown in Figure 7, the first labyrinth portion 91 provided in the non-circular cam 65 is provided in a substantially annular shape surrounding the central axis AX in a plan view. Although not shown, the second labyrinth portion 92 is also provided in a substantially annular shape surrounding the central axis AX in a plan view.

Next, with reference to Figs. 6B to 6D, another example of the seal portion 90 will be described. Fig. 6B is an enlarged longitudinal sectional view of another example of the seal portion 90 (hereinafter, seal portion 90A). As shown in Fig. 6B, the seal portion 90A is configured by an oil seal. The seal portion 90A is a substantially annular shape surrounding the central axis AX. Meanwhile, the second ring portion 192 bends in the axial direction AD at the tip portion 193 in the radial direction RD. The seal portion 90A is disposed between the axial direction AD side surface of the non-circular cam 65 and the tip portion 193 of the second ring portion 192. As a result, the seal portion 90A seals between the reducer 200 and the motor body 10.

Figure 6C is an enlarged longitudinal cross-sectional view of yet another example of the seal portion 90 (hereinafter, seal portion 90B). As shown in Figure 6C, the seal portion 90B is configured by a V-ring. The seal portion 90A is a substantially annular shape surrounding the central axis AX. The seal portion 90B is disposed between the axial direction AD side surface of the non-circular cam 65 and the radial direction RD tip end of the second ring portion 192. As a result, the seal portion 90B provides a seal between the reducer 200 and the motor body 10.

Figure 6D is an enlarged longitudinal cross-sectional view of yet another example of the seal portion 90 (hereinafter, seal portion 90C). As shown in Figure 6D, the seal portion 90C is configured by an O-ring. The seal portion 90C is a substantially annular shape surrounding the central axis AX. The seal portion 90C is disposed between the axial direction AD side surface of the non-circular cam 65 and the radial direction RD tip end of the second ring portion 192. As a result, the seal portion 90C provides a seal between the reducer 200 and the motor body 10.

The configuration of the seal parts 90, 90A to 90C is not particularly limited as long as they can seal between the reducer 200 and the motor body 10. For simplicity, the fixing member R3 in FIG. 1 is omitted in FIG. 6A to FIG. 6D.

Next, the reduction gear 200 will be described in detail with reference to Figs. 1 and 3. The reduction gear 200 shown in Figs. 1 and 3 is a device that uses the differential between the rigid internal gear 40 and the flexible external gear 50 to reduce the speed of the input rotational motion. A reduction gear SR having the reduction gear 200 is incorporated, for example, into bicycles, joints of small robots, assist suits, turntables, indexing plates of machine tools, wheelchairs, or automated guided vehicles. However, there is no particular limit to the objects into which the reduction gear SR is incorporated.

As shown in Figs. 1 and 3, the reducer 200 further includes an output rotor 55, a housing 70, a bearing 80, a seal member 85, a fixed member R3, and a fixed member R4. The input shaft of the reducer 200 is the rotating shaft 25 of the motor 100. The output shaft of the reducer 200 is the output rotor 55. The output rotor 55 is, for example, a bush.

The rigid internal gear 40 is a member that extends in a substantially circular ring shape around the central axis AX. The rigid internal gear 40 has a higher rigidity than the cylindrical portion 51 of the flexible external gear 50. Therefore, the rigid internal gear 40 can be considered to be a substantially rigid body. The rigid internal gear 40 has a plurality of internal teeth 41 on its inner peripheral surface. The multiple internal teeth 41 are arranged at a constant pitch along the circumferential direction CD.

The flexible external gear 50 has a flat plate portion 52 in addition to the cylindrical portion 51. The cylindrical portion 51 is a portion that extends cylindrically in the axial direction AD around the central axis AX. The cylindrical portion 51 is also a cylindrical portion that is flexible and can bend in the radial direction RD. One end of the cylindrical portion 51 in the axial direction AD is disposed inside the rigid internal gear 40 in the radial direction RD. The flat plate portion 52 is also a flat portion that is less likely to bend than the cylindrical portion 51. The flat plate portion 52 is a portion that extends inward in the radial direction RD from the other end of the cylindrical portion 51 in the axial direction AD.

The flexible external gear 50 has multiple external teeth 511 on its outer circumferential surface near one end. The multiple external teeth 511 are arranged at a constant pitch along the circumferential direction CD. An output rotor 55, which is an output shaft for extracting power after deceleration, is fixed to the flat plate portion 52.

In the wave generator 60, the non-circular cam 65 is a member that expands in an annular shape around the central axis AX. The non-circular cam 65 is connected to the rotating shaft 25 as the input shaft. Therefore, the non-circular cam 65 rotates around the central axis AX at the rotation speed before deceleration due to the rotation of the rotating shaft 25. In the first embodiment, the non-circular cam 65 has an elliptical cam profile. In other words, the non-circular cam 65 has an outer diameter that differs depending on the position in the circumferential direction CD. In further other words, the outer edge of the non-circular cam 65 is approximately elliptical.

The non-circular cam 65 is sandwiched between the fixed member R3 and the fixed member R4 in the axial direction AD. As a result, the non-circular cam 65 is positioned in the axial direction AD.

The wave bearing 61 is a flexible bearing located on the radially inner side RD of the cylindrical portion 51 of the flexible external gear 50. The wave bearing 61 is substantially annular. The wave bearing 61 is, for example, a ball bearing. The wave bearing 61 has an inner ring 62, a plurality of balls 63, and an elastically deformable outer ring 64. The inner ring 62 is fixed to the outer peripheral surface of the non-circular cam 65. The plurality of balls 63 are interposed between the inner ring 62 and the outer ring 64 and are arranged along the circumferential direction CD. The outer ring 64 elastically deforms (flexibly deforms) via the inner ring 62 and the balls 63 so as to reflect the cam profile of the rotating non-circular cam 65. In addition, the outer ring 64 contacts the inner peripheral surface of the portion of the cylindrical portion 51 having the external teeth 511 in the flexible external gear 50. Specifically, the outer ring 64 is fixed to the inner peripheral surface of the portion of the cylindrical portion 51 having the external teeth 511. The wave generator 60 has an outer diameter that varies depending on the position in the circumferential direction CD, and rotates around the central axis AX at the rotational speed before deceleration, inside the rigid internal gear 40 in the radial direction RD.

The output rotor 55 is fixed to the outer ring 38 of the second bearing 35. Specifically, the output rotor 55 has a cylindrical body 551 and a bearing holder 552. The bearing holder 552 holds the second bearing 35. Specifically, the outer ring 38 of the second bearing 35 is fixed to the inner peripheral surface of the bearing holder 552 in the radial direction RD. The cylindrical body 551 is substantially cylindrical and surrounds the central axis AX in the circumferential direction CD. The cylindrical body 551 extends along the axial direction AD.

The housing 70 accommodates a part of the cylindrical portion 51 and the flat portion 52 of the flexible external gear 50. The housing 70 is fixed to the rigid internal gear 40 at one end in the axial direction AD. At the other end in the axial direction AD of the housing 70, the inner surface in the radial direction RD of the housing 70 faces the outer peripheral surface of the cylindrical body portion 551 via the bearing 80 and the seal member 85.

Specifically, the housing 70 has a first cylindrical portion 71 having a substantially cylindrical shape, a flat plate portion 72 having a substantially annular shape, and a second cylindrical portion 73 having a substantially cylindrical shape. One end of the first cylindrical portion 71 in the axial direction AD faces the rigid internal gear 40 in the axial direction AD and is fixed to the rigid internal gear 40. The first cylindrical portion 71 surrounds the central axis AX and extends along the axial direction AD. The flat plate portion 72 expands in the radial direction RD from the other end of the first cylindrical portion 71 in the axial direction AD toward the central axis AX. The second cylindrical portion 73 extends in the axial direction AD from the inner end of the flat plate portion 72 in the radial direction RD. The second cylindrical portion 73 surrounds the central axis AX and extends along the axial direction AD.

The seal member 85 is generally annular. The seal member 85 is disposed between the inner peripheral surface of the second cylindrical portion 73 and the outer peripheral surface of the cylindrical body portion 551. The seal member 85 seals between the inner peripheral surface of the second cylindrical portion 73 and the outer peripheral surface of the cylindrical body portion 551. The seal member 85 is, for example, an oil seal. The seal member 85 can prevent grease present inside the reducer 200 from leaking to the outside.

The bearing 80 is substantially annular. The bearing 80 is disposed between the inner peripheral surface of the second cylindrical portion 73 and the outer peripheral surface of the cylindrical body portion 551. The bearing 80 is disposed closer to the flexible external gear 50 than the seal member 85. The bearing 80 is, for example, a ball bearing. The bearing 80 has an inner ring 81, a plurality of balls 82, and an outer ring 83. The inner ring 81 is fixed to the outer peripheral surface of the cylindrical body portion 551. The plurality of balls 82 are interposed between the inner ring 81 and the outer ring 83 and are arranged along the circumferential direction CD. The outer ring 83 is fixed to the inner peripheral surface of the second cylindrical portion 73 in the radial direction RD.

In the reducer 200 configured as described above, when the rotating shaft 25 of the motor 100 rotates at the rotational speed before deceleration, the non-circular cam 65 rotates at the rotational speed before deceleration. In other words, the non-circular cam 65 rotates at the same rotational speed as the rotating shaft 25. As the non-circular cam 65 rotates, the inner circumferential surface of the portion of the cylindrical portion 51 in the flexible external gear 50 having the external teeth 511 is pressed through the wave bearing 61, causing the cylindrical portion 51 to bend and deform into an ellipse. Furthermore, the cylindrical portion 51 is inclined in a direction in which the diameter increases toward one end (a direction in which the diameter decreases toward the other end) near the outer side in the radial direction RD at two locations on both ends of the long axis of the ellipse formed by the non-circular cam 65. As a result, the external teeth 511 and the internal teeth 41 mesh with each other near the outer side in the radial direction RD at two locations on both ends of the long axis of the ellipse.

When the non-circular cam 65 rotates, the positions of both ends of the major axis of the ellipse formed by the non-circular cam 65 move in the circumferential direction CD, so the meshing portion between the external teeth 511 and the internal teeth 41 also moves in the circumferential direction CD. Here, the number of teeth of the internal teeth 41 of the rigid internal gear 40 and the number of teeth of the external teeth 511 of the flexible external gear 50 are slightly different. For this reason, the meshing portion between the internal teeth 41 and the external teeth 511 changes slightly with each rotation of the non-circular cam 65. As a result, the flexible external gear 50 and the output rotor 55 rotate at a reduced rotation speed relative to the rigid internal gear 40. In other words, the flexible external gear 50 and the output rotor 55 rotate relative to the rigid internal gear 40 due to the difference in the number of teeth between the external teeth 511 and the internal teeth 41 while moving the meshing portion between the external teeth 511 of the flexible external gear 50 and the internal teeth 41 of the rigid internal gear 40 in the circumferential direction CD.

In the reduction gear 200 described with reference to Figures 1 and 3, the flexible external gear 50 has been described as an example of a "flexible member" and the rigid internal gear 40 has been described as an example of an "annular member". However, as long as the rotational motion of the first rotational speed can be converted into the rotational motion of the second rotational speed lower than the first rotational speed, the "flexible member" and the "annular member" are not particularly limited. For example, when the reduction gear 200 performs deceleration using traction (friction), the "flexible member" may be flexible but may not have external teeth, and the "annular member" may be elastic but may not have internal teeth. In this case, the outer peripheral surface of the "flexible member" contacts the inner peripheral surface of the "annular member" via an oil film of lubricating oil.

(Embodiment 2)
A bicycle 300 according to a second embodiment of the present invention will be described with reference to Figures 8 and 9. The bicycle 300 according to the second embodiment is equipped with the reduction gear SR described with reference to Figure 1. Therefore, in the following, a description of the reduction gear SR will be omitted as appropriate.

8 is a diagram showing a bicycle 300 according to the second embodiment. As shown in FIG. 8, the bicycle 300 has a front wheel 310, a rear wheel 320, a pedal 330, a crank arm 340, a roller chain 350, and a reduction gear SR. The pedal 330 is disposed on each of both sides of the bicycle 300. The crank arm 340 is disposed on each of both sides of the bicycle 300. The pedal 330 is rotatably attached to the crank arm 340. Hereinafter, one of the directions in which the pedal 330 rotates is referred to as the "forward direction". When the user pedals the pedal 130 in the forward direction, the rotational motion of the pedal 330 is transmitted to the rear wheel 320 via the roller chain 350. As a result, the rear wheel 320 rotates, and the bicycle 300 moves forward due to the rotation of the rear wheel 320 and the front wheel 310.

The reduction gear SR is disposed between the pedals 330 disposed on both sides of the bicycle 300. The reduction gear SR is disposed inside a chain cover 351 that covers the roller chain 350. For example, when starting or riding uphill, if the load on the pedal 330 is large, the reduction gear SR supplies a forward rotational driving force to the pedal 330. In other words, the reduction gear SR functions as an electric assist device. This reduces the force with which the user pedals the pedal 330. As a result, the user can ride the bicycle 300 with ease.

In particular, according to the second embodiment, the bicycle 300 is equipped with a reduction gear SR that can make the length in the axial direction AD relatively small, so that an increase in the weight of the bicycle 300 can be suppressed. In addition, because the length in the axial direction AD of the reduction gear SR is relatively small, the reduction gear SR does not get in the way, making it easier for the user to pedal the pedals 330.

Figure 9 is a vertical cross-sectional view showing the reduction gear SR mounted on the bicycle 300. As shown in Figure 9, the bicycle 300 further includes a crankshaft 360, a sprocket 370, a one-way clutch 380, a bearing 385, and a bearing 390. Note that the crankshaft 360 is shown in white to make the drawing easier to see.

The crankshaft 360 is a generally cylindrical member extending along the central axis AX. The crankshaft 360 passes through the rotating shaft 25 of the reduction gear SR and the output rotor 55 in the axial direction AD. The crankshaft 360 is driven by the pedal force from the pedal 330 (Figure 8).

Both ends of the crankshaft 360 in the axial direction AD protrude outside the reduction gear SR. A crank arm 340 is fixed to each end of the crankshaft 360 in the axial direction AD. When a user of the bicycle 300 pedals a pedal 330 (FIG. 8) connected to the crank arm 340, the pedal force (human power) causes the pedal 330, crank arm 340, and crankshaft 360 to rotate about the central axis AX.

The sprocket 370 is connected to the output rotor 55, which is the output shaft of the reduction gear 200. Specifically, the sprocket 370 is fixed to the output rotor 55, which is the output shaft of the reduction gear 200. The sprocket 370 is approximately perpendicular to the axial direction AD. The sprocket 370 transmits the rotation of the crankshaft 360, which is transmitted via the one-way clutch 380 and the output rotor 55, to the roller chain 350. The sprocket 370 is approximately disk-shaped with the central axis AX as its center. The sprocket 370 has multiple external teeth on its outer periphery. The sprocket 370 engages with the roller chain 350 of the bicycle 300 through the multiple external teeth. When the crankshaft 360 rotates due to the pedaling force from the pedal 330, the sprocket 370 rotates around the central axis AX via the one-way clutch 380 and the output rotor 55. As a result, the roller chain 350 rotates between the sprocket 370 and the rear wheel 320.

Bearings 385 and 390 are arranged on the inner peripheral surface of the rotating shaft 25. The bearings 385 and 390 are, for example, ball bearings. The bearings 385 and 390 are arranged at intervals along the axial direction AD. The bearings 385 and 390 rotatably support the crankshaft 360. The bearing 385 has an inner ring 386, a plurality of balls 387, and an outer ring 388. The inner ring 386 is fixed to the outer peripheral surface of the crankshaft 360. The plurality of balls 387 are interposed between the inner ring 386 and the outer ring 388 and are arranged along the circumferential direction CD. The outer ring 388 is fixed to the inner peripheral surface of the rotating shaft 25. The bearing 390 has an inner ring 391, a plurality of balls 392, and an outer ring 393. The inner ring 391 is fixed to the outer peripheral surface of the crankshaft 360. A number of balls 392 are interposed between the inner ring 391 and the outer ring 393 and are arranged along the circumferential direction CD. The outer ring 393 is fixed to the inner surface of the rotating shaft 25.

The one-way clutch 380 is a mechanism that allows the output rotor 55 to rotate relative to the crankshaft 360 in only one direction. The one-way clutch 380 is disposed between the output rotor 55 and the crankshaft 360 in the radial direction RD. Specifically, the one-way clutch 380 is disposed between the inner circumferential surface of the output rotor 55 and the outer circumferential surface of the crankshaft 360 in the radial direction RD.

When the forward rotation speed of the crankshaft 360 is greater than the forward rotation speed of the output rotor 55, the one-way clutch 380 allows the crankshaft 360 to rotate. Therefore, when the motor 100 of the reduction gear SR is not driven, the user of the bicycle 300 can rotate the crankshaft 360 via the pedals 330 without experiencing resistance from the motor 100. In this case, the sprocket 370 rotates only due to the rotational force of the crankshaft 360.

However, the one-way clutch 380 prohibits the forward rotational speed of the output rotor 55 from becoming greater than the forward rotational speed of the crankshaft 360. Therefore, when the motor 100 is driven and the forward rotational speed of the output rotor 55 catches up with the forward rotational speed of the crankshaft 360, the crankshaft 360 rotates in the forward direction at the same rotational speed as the output rotor 55.

The bicycle 300 further includes a controller 400 and a torque sensor 410. The torque sensor 410 detects the distortion of the crankshaft 360 in a non-contact manner and converts the amount of distortion into a torque value. The torque sensor 410 outputs a detection signal indicating the torque value of the crankshaft 360 to the controller 400.

The controller 400 implements an electrical circuit for supplying a drive current to the coil 14 of the stator 11. The controller 400 is electrically connected to the coil 14, the torque sensor 410, and a battery (not shown). The controller 400 has a microcomputer. The microcomputer has a processor and a memory.

The controller 400 receives a detection signal indicating the torque of the crankshaft 360 from the torque sensor 410. A preset torque threshold is stored in the memory of the controller 400. If the torque value indicated by the detection signal received from the torque sensor 410 is less than the threshold, the controller 400 does not supply a drive current to the coil 14. Therefore, the motor 100 does not drive. On the other hand, if the torque value indicated by the detection signal received from the torque sensor 410 is equal to or greater than the threshold, the controller 400 generates a drive current according to the torque value using power supplied from the battery and supplies it to the coil 14. As a result, the motor 100 drives.

When the motor 100 is driven and the forward rotation speed of the output rotor 55 is smaller than the forward rotation speed of the crankshaft 360, a reduced rotation force based on the rotation force of the motor 100 is transmitted to the output rotor 55. As a result, the sprocket 370 rotates due to the reduced rotation force based on the rotation force of the motor 100 and the rotation force of the crankshaft 360 due to the user's pedaling force.

On the other hand, when the motor 100 is driven and the forward rotation speed of the output rotor 55 is greater than the forward rotation speed of the crankshaft 360, the one-way clutch 380 acts to rotate the sprocket 370 only by the rotational force of the crankshaft 360 caused by the user's pedaling force.

Above, the embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the gist of the present invention. In addition, various inventions can be formed by appropriately combining multiple components disclosed in the above embodiments. For example, some components may be deleted from all components shown in the embodiments. For example, components from different embodiments may be appropriately combined. The drawings are mainly schematic views of each component for ease of understanding, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of drawing. In addition, the material, shape, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible within a range that does not substantially deviate from the effects of the present invention.

The present invention can be used, for example, in reduction gears and bicycles.

REFERENCE SIGNS LIST 10 Motor body 15 Rotor 25 Rotating shaft 30 First bearing 35 Second bearing 40 Rigid internal gear (annular member)
50 Flexible external gear (flexible member)
60 Wave generator 66 Second connection part 67 Second recess 90 Sealing part 100 Motor 161 First connection part 162 First recess 200 Speed reducer 250 Protrusion 300 Bicycle 330 Pedal 360 Crankshaft 370 Sprocket SR Speed reducer

Claims (6)

A motor;
a reducer for reducing the rotation speed of the motor;
The motor includes a motor body, a rotating shaft that rotates around a central axis, a first bearing, and a second bearing.
The reducer includes:
a wave generator having an outer diameter that varies depending on a circumferential position and rotating about the central axis;
a flexible member having a flexible cylindrical portion with which the wave generator comes into contact from a radially inner side;
an annular member with which the cylindrical portion comes into contact from a radially inner side ;
Output shaft and
having
the flexible member rotates relative to the annular member in response to rotation of the wave generator;
the motor body has a rotor connected to the rotary shaft,
the wave generator is connected to the rotating shaft at a position different from a position at which the rotor is connected;
the first bearing is disposed on an opposite side of the rotor from the wave generator and rotatably supports the rotating shaft;
The second bearing is disposed radially inside the cylindrical portion and rotatably supports the rotating shaft .
the flexible member further includes a flat plate portion extending radially inward from the other end of the cylindrical portion opposite to the one end that contacts the annular member,
The output shaft holds an outer ring of the second bearing and is fixed to the flat plate portion . A motor;
a reducer for reducing the rotational speed of the motor;
Equipped with
The motor includes a motor body, a rotating shaft that rotates around a central axis, a first bearing, and a second bearing.
The reducer includes:
a wave generator having an outer diameter that varies depending on a circumferential position and rotating about the central axis;
a flexible member having a flexible cylindrical portion with which the wave generator comes into contact from a radially inner side;
an annular member that is in contact with the cylindrical portion from the radially inner side;
having
the flexible member rotates relative to the annular member in response to rotation of the wave generator;
the motor body has a rotor connected to the rotary shaft,
the wave generator is connected to the rotating shaft at a position different from a position at which the rotor is connected;
the first bearing is disposed on an opposite side of the rotor from the wave generator and rotatably supports the rotating shaft;
The second bearing is disposed radially inside the cylindrical portion and rotatably supports the rotating shaft.
the number of poles of the motor is N (an integer equal to or greater than 2);
The rotor has a first connection portion that is connected to the rotating shaft,
The first connection portion has N first recesses arranged in a circumferential direction,
Each of the N first recesses is recessed radially outward and extends along the axial direction,
the wave generator has a second connection portion that is connected to the rotation shaft,
The second connection portion has N second recesses arranged in a circumferential direction,
Each of the N second recesses is recessed radially outward and extends along the axial direction,
The first recess and the second recess are aligned in a straight line along the axial direction,
The rotating shaft has N protrusions protruding radially outward,
The N protrusions extend along an axial direction, and are fitted into the N first recesses and are fitted into the N second recesses. The reduction gear according to claim 1 or 2, wherein the second bearing is disposed on the opposite side of the rotor from the wave generator. a seal portion for sealing between the reducer and the motor body on a radially outer side of the rotating shaft,
The reduction gear transmission according to claim 1 , wherein grease is present inside the reduction gear. The reduction gear according to any one of claims 1 to 4, wherein the rotating shaft is hollow. The reduction gear according to claim 5 ;
Pedals and
a crankshaft that axially passes through the rotating shaft of the reduction gear device and is driven by a pedal force from the pedal;
and a sprocket to which the output shaft of the reduction gear device is connected.

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