CN114810986A - Speed reduction device and bicycle - Google Patents

Abstract

The speed reducer includes a motor and a speed reducer. The motor has a motor body, a rotating shaft, a first bearing and a second bearing. The decelerator is provided with a wave generator, a flexible member and an annular member. The wave generator has different outer diameters according to the position in the circumferential direction. The flexible member has a flexible cylindrical portion to which the wave generator is contacted from the radially inner side. The cylindrical portion contacts the annular member from the radially inner side. The flexible member relatively rotates with respect to the annular member in accordance with the rotation of the wave generator. The wave generator is connected to the rotating shaft at a position different from a position of the rotor to which the motor 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 inward of the cylindrical portion of the flexible member and rotatably supports the rotating shaft.

Description

Speed reduction device and bicycle

Technical Field

The invention relates to a speed reducing device and a bicycle.

Background

The conventional drive module has a first drive shaft (for example, japanese laid-open publication No. 2018-507140). The first drive shaft is provided for the input drive of the drive module. Furthermore, a second drive shaft is provided. The second drive shaft is coupled to a rotor of an electric auxiliary drive device in a non-rotatable manner. The electric auxiliary drive also has a stator.

In this manner, the rotor may also be coupled with the wave gear device via the second drive shaft. The wave gear device has an inner bushing, a wave generator, and an outer bushing.

However, in the conventional drive module, the wave gear device and the electric auxiliary drive device are arranged to be separated in the axial direction. Therefore, the axial length of the drive module (reduction gear) becomes large.

Disclosure of Invention

The present invention has been made in view of the above-described problems, and an object thereof is to provide a reduction gear device capable of reducing the axial length.

An exemplary reduction gear of the present invention includes a motor and a reduction gear. The speed reducer reduces the rotational speed of the motor. The motor includes a motor main body, a rotating shaft that rotates about a central axis, a first bearing, and a second bearing. The decelerator is provided with a wave generator, a flexible component and an annular component. The wave generator has different outer diameters according to positions in the circumferential direction and rotates about the central axis. The flexible member has a flexible cylindrical portion with which the wave generator is contacted from the radially inner side. The cylindrical portion contacts the annular member from the radially inner side. The flexible member relatively rotates with respect to the annular member in accordance with the rotation of the wave generator. The motor main body has a rotor connected to the rotating 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 the opposite side of the wave generator with respect to the rotor, and rotatably supports the rotating shaft. The second bearing is disposed radially inward of the cylindrical portion and rotatably supports the rotating shaft.

An exemplary bicycle of the present invention has the above-described reduction gear, pedals, a crank shaft, and a sprocket. The crank shaft penetrates the rotating shaft of the speed reducer along the axial direction and is driven by the pedaling force from the pedals. The chain wheel is connected with an output shaft of the speed reducing device.

According to the exemplary invention, a reduction gear and a bicycle capable of reducing the axial length can be provided.

The above and other features, elements, steps, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a longitudinal sectional view showing a reduction gear transmission according to embodiment 1 of the present invention.

Fig. 2 is a cross-sectional view showing a motor of embodiment 1.

Fig. 3 is a cross-sectional view showing a reduction gear according to embodiment 1.

Fig. 4 is a perspective view showing a rotating shaft of the motor of embodiment 1.

Fig. 5 is a longitudinal sectional view showing a part of the reduction gear transmission according to embodiment 1 in an enlarged manner.

Fig. 6A is a vertical sectional view showing a seal portion of the reduction gear transmission according to embodiment 1 in an enlarged manner.

Fig. 6B is a longitudinal sectional view showing another example of the seal portion of the reduction gear transmission according to embodiment 1 in an enlarged manner.

Fig. 6C is an enlarged longitudinal sectional view showing still another example of the seal portion of the reduction gear transmission according to embodiment 1.

Fig. 6D is a longitudinal sectional view showing still another example of the seal portion of the reduction gear transmission according to embodiment 1 in an enlarged manner.

Fig. 7 is a plan view showing a non-circular cam of the reduction gear transmission according to embodiment 1.

Fig. 8 is a diagram showing a bicycle according to embodiment 2 of the present invention.

Fig. 9 is a longitudinal sectional view showing a reduction gear mounted to a bicycle according to embodiment 2.

Detailed Description

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated. In the drawings, for the sake of easy understanding, the X axis, the Y axis, and the Z axis of the three-dimensional rectangular coordinate system are appropriately described.

In the present specification, a direction parallel to the central axis AX of the reduction gear transmission is referred to as an "axial direction AD", a direction orthogonal to the central axis AX is referred to as a "radial direction RD", and a direction along an arc centered on the central axis AX is referred to as a "circumferential direction CD". In addition, "parallel direction" includes a substantially parallel direction, and "orthogonal direction" includes a substantially orthogonal direction. The "plan view" indicates that the object is viewed in the axial direction AD.

(embodiment mode 1)

A reduction gear SR according to embodiment 1 of the present invention will be described with reference to fig. 1 to 7. Fig. 1 is a longitudinal sectional view showing a reduction gear SR according to embodiment 1. Fig. 2 is a cross-sectional view showing the motor 100 of the reduction gear SR. Fig. 2 corresponds to a section along the line ii-ii of fig. 1. Fig. 3 is a cross-sectional view showing the reduction gear 200 of the reduction gear SR. Fig. 3 corresponds to a cross section along the line iii-iii of fig. 1.

The reduction gear SR shown in fig. 1 reduces the rotation speed. The rotation speed means, for example, a rotation speed per unit time. Specifically, reduction gear SR converts a rotational motion at a first rotational speed into a rotational motion at a second rotational speed lower than the first rotational speed.

As shown in fig. 1, the reduction gear SR has a motor 100 and a reduction gear 200. The motor 100 drives the decelerator 200. The decelerator 200 decelerates the rotation speed of the motor 100. Specifically, reducer 200 converts a rotational motion at a first rotational speed generated by motor 100 into a rotational motion at a second rotational speed lower than the first rotational speed.

The motor 100 includes a motor main body 10, a rotating shaft 25, a first bearing 30, and a second bearing 35. In the present embodiment, the motor 100 includes a motor body 10, a rotating shaft 25 that rotates about 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 passing through the center of the rotating shaft 25 along the longitudinal direction of the rotating shaft 25. The motor main body 10 rotates the rotation shaft 25. As shown in fig. 1 and 2, the motor main body 10 has a rotor 15.

As shown in fig. 1 and 3, the speed reducer 200 includes a rigid internally-toothed gear 40, a flexible externally-toothed gear 50, and a wave generator 60.

The flexible externally toothed gear 50 corresponds to an example of a "flexible member". The rigid internally-toothed gear 40 corresponds to an example of the "annular member".

The wave generator 60 has different outer diameters according to the position in the circumferential direction CD. The wave generator 60 rotates about the central axis AX. In the example of fig. 3, the wave generator 60 is generally elliptical in shape. The wave generator 60 is a mechanism that causes the flexible externally toothed gear 50 to flex. The flexible externally toothed gear 50 has a cylindrical portion 51. The cylindrical portion 51 has flexibility. The wave generator 60 contacts the cylindrical portion 51 from the radially inner side. That is, the flexible externally toothed gear 50 has a flexible cylindrical portion 51 with which the wave generator 60 comes into contact from the radially inner side. The cylindrical portion 51 has a substantially cylindrical shape. The rigid internally toothed gear 40 is substantially annular. In the example of fig. 3, the rigid internally toothed gear 40 has a substantially annular shape. The cylindrical portion 51 of the flexible externally toothed gear 50 contacts the rigid internally toothed gear 40 from the radially inner side RD. That is, the rigid internally toothed gear 40 is annular in shape with the cylindrical portion 51 contacting from the radially inner side. The flexible externally toothed gear 50 rotates relative to the rigid internally toothed gear 40 in accordance with the rotation of the wave generator 60.

As shown in fig. 1, in the motor 100, the rotor 15 of the motor main 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 decelerator 200, the wave generator 60 is connected to the rotation 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 disposed on the opposite side of the wave generator 60 with the rotor 15 interposed therebetween. That is, the first bearing 30 is disposed on the opposite side of the wave generator 60 from the rotor 15. The second bearing 35 of the motor 100 rotatably supports the rotary shaft 25. The second bearing 35 is disposed radially inside RD of the cylindrical portion 51 of the flexible externally toothed gear 50. That is, the second bearing 35 of the motor 100 is disposed inside the reducer 200. Therefore, according to embodiment 1, the length of the reduction gear SR in the axial direction AD can be reduced as compared with the case where the second bearing 35 of the motor 100 is disposed outside the reduction gear 200. That is, the axial direction AD of the reduction gear SR can be made shorter.

Specifically, in embodiment 1, the second bearing 35 of the motor 100 is disposed on the opposite side of the rotor 15 with the wave generator 60 interposed therebetween. That is, the second bearing 35 is disposed on the opposite side of the rotor 15 from the wave generator 60. Therefore, according to embodiment 1, the motor main body 10 can be disposed further toward the reduction gear 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 embodiment 1, the rotating shaft 25 of the motor 100 is preferably hollow. According to this preferred example, mechanical parts such as a shaft can be disposed inside the rotating shaft 25. As a result, the range of application of the reduction gear SR is expanded. Specifically, the rotating shaft 25 has a substantially cylindrical inner space SP. In addition, the rotating shaft 25 may not be hollow.

Next, details of the motor 100 will be described with reference to fig. 1 and 2. As shown in fig. 1, the motor 100 further includes a fixing member R1, a spacer R10, a spacer R11, and a fixing member R2. The motor body 10 further includes a stator 11 and a flange 18.

The stator 11 is a stator of the motor 100. The stator 11 is disposed centering on the central axis AX. Specifically, the stator 11 includes a stator core 12, an insulator 13, and a plurality of coils 14.

The stator core 12 is disposed centering on the central axis AX. The stator core 12 is disposed so as to surround the center axis AX and has a substantially annular shape. The stator core 12 is made of, for example, laminated steel sheets obtained by laminating thin electromagnetic steel sheets in the axial direction AD. The insulator 13 electrically insulates the stator core 12 and the coil 14. The insulator 13 is made of an insulating material. The insulator 13 covers at least a part of the stator core 12. The insulator 13 is disposed in a substantially annular shape so as to surround the central axis AX. The insulator 13 may be constituted by a plurality of different members or may be constituted by a single member. The coil 14 is formed by winding a conductive wire around the stator core 12 with an insulator 13 interposed therebetween.

As shown in fig. 2, the stator core 12 has a substantially annular core back 121 and a plurality of pole teeth 122. A plurality of pole teeth 122 project from the core back 121 toward the radially RD inner side. The coil 14 is formed by winding a wire around the teeth 122. The plurality of coils 14 are arranged along the circumferential direction CD. As an example, the stator core 12 has 18 slots. Thus, in the example of fig. 2, the stator 11 has 18 coils 14.

Returning to fig. 1, the rotor 15 is a rotor of the motor 100. That is, the rotor 15 rotates about the central axis AX. The rotor 15 is connected to a rotating shaft 25. Therefore, when the rotor 15 rotates, the rotation shaft 25 rotates. That is, the rotation shaft 25 rotates together with the rotor 15. The rotor 15 is disposed centering on the central axis AX. The rotor 15 is disposed radially inside RD of the stator 11. That is, the motor 100 is an inner rotor type motor. Further, 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 having a substantially annular shape. The rotor core 16 is made of, for example, laminated steel sheets in which electromagnetic steel sheets are laminated in the axial direction AD. The magnets 17 are fixed to the radially RD outer surface of the rotor core 16. That is, the motor 100 is an SPM (Surface Permanent Magnet) motor. The magnet 17 may be fixed inside the rotor core 16. That is, the motor 100 may be a so-called IPM (Interior Permanent Magnet) motor. The magnets 17 and the stator core 12 are opposed at a space in the radial direction RD.

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

As shown in fig. 2, the rotor 15 has N magnets 17. Therefore, the number of poles of the motor 100 is "N". N is an integer of 2 or more. In the example of fig. 2, N is 20. The rotor 15 has a first connection portion 161. Specifically, the rotor core 16 is disposed centering on the central axis AX. The rotor core 16 is disposed so as to surround the central axis AX and has a substantially annular shape. Also, the rotor core 16 has a first connection portion 161. The first connection portion 161 is connected to the rotation shaft 25. Specifically, the first connection portion 161 has N first recesses 162 connected in the circumferential direction CD. The N first recesses 162 are each recessed outward in the radial direction RD and extend in the axial direction AD.

The N first recesses 162 are opposed to the N magnets 17 in the radial direction RD, respectively. The shape of the N first recesses 162 is set so as to optimize the magnetic field of the N magnets 17. The "optimized magnetic field" refers to a magnetic field that can most smoothly rotate the rotor 15 with respect to the stator 11. The N first recesses 162 are provided on the inner circumferential 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 are fitted to the N first concave portions 162, respectively. As a result, the rotor core 16 is connected to the rotating shaft 25. That is, the rotor 15 is connected to the rotating shaft 25. In addition, the rotating shaft 25 having the convex portion 250 and the rotor core 16 having the first concave portion 162 constitute 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 disposed substantially annularly about the center axis AX. Specifically, the flange 18 includes a first flange 19 and a second flange 20. The first flange 19 has a substantially annular shape. The second flange portion 20 has a substantially annular shape. The first flange 19 covers the stator 11 from the 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 19 and the second flange 20 sandwich the stator 11 in the axial direction AD, thereby holding the stator 11. As a result, the stator 11 is fixed to the flange 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 rotatably supports the rotating shaft 25 with respect to the stator 11 and the flange 18. The first bearing 30 is, for example, a ball bearing. The first bearing 30 has an inner race 31, a plurality of balls 32, and an outer race 33. The inner race 31 is fixed to the outer peripheral surface of the rotating shaft 25. The plurality of balls 32 are interposed between the inner race 31 and the outer race 33, and are arranged in the circumferential direction CD. The outer race 33 is fixed to the inner circumferential surface of the first flange portion 19 in the radial direction RD.

A substantially annular spacer R11 is disposed between the inner race 31 of the first bearing 30 and the rotor 15. Further, a substantially annular spacer R10 is disposed on the opposite side of the spacer R11 with respect to the inner race 31. The inner ring 31 is sandwiched between the spacer R11 and the fixing member R1 via the spacer R10, and is positioned in the axial direction AD.

The second bearing 35 is disposed at the other end portion in the axial direction AD of the rotating shaft 25. The second bearing 35 rotatably supports the rotating shaft 25 with respect to the stator 11 and the flange 18. The second bearing 35 is, for example, a ball bearing. The second bearing 35 has an inner race 36, a plurality of balls 37, and an outer race 38. The inner race 36 is fixed to the outer peripheral surface of the rotating shaft 25. A plurality of balls 37 are interposed between the inner race 36 and the outer race 38, and are arranged in the circumferential direction CD. The outer race 38 is fixed to an output rotary body 55 described later. Although not shown in fig. 1, the inner race 36 is actually separated from the output rotary body 55 by a gap.

Next, details of the reduction gear 200 and the rotation shaft 25 will be described with reference to fig. 3 and 4. As shown in fig. 3, the wave generator 60 has a second connection portion 66. Specifically, the wave generator 60 includes a wave bearing 61 and a non-circular cam 65. The wave bearing 61 has flexibility. The wave bearing 61 is located inside the cylindrical portion 51 of the flexible externally toothed gear 50 in the radial direction RD. The non-circular cam 65 extends annularly around the center axis AX. In the example of fig. 3, the non-circular cam 65 is substantially elliptical. The wave bearing 61 is disposed along the outer peripheral surface of the non-circular cam 65 and is deflected in a substantially elliptical shape. The non-circular cam 65 has a second connecting portion 66.

The second connecting portion 66 is connected to the rotating shaft 25. Specifically, the second connection portion 66 has N second concave portions 67 connected in the circumferential direction CD. The N second recesses 67 are each recessed outward in the radial direction RD and extend in the axial direction AD. The N second recesses 67 are provided on the inner circumferential surface of the non-circular cam 65. 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 in a plan view.

The N second recesses 67 correspond to the N first recesses 162 shown in fig. 2, respectively. The N second recesses 67 are respectively opposed to the N first recesses 162 in the axial direction AD. That is, the first recess 162 and the second recess 67 are aligned on a straight line along the axial direction AD.

On the other hand, the N convex portions 250 of the rotation shaft 25 are fitted to the N second concave portions 67, respectively. As a result, the non-circular cam 65 is connected to the rotating shaft 25. That is, the wave generator 60 is connected to the rotating shaft 25. The rotating shaft 25 functions as an input shaft of the speed reducer 200. In addition, the rotating shaft 25 having the convex portion 250 and the non-circular cam 65 having the second concave portion 67 constitute a spline.

Fig. 4 is a perspective view showing the rotating shaft 25 of the motor 100. As shown in fig. 4, in the rotating shaft 25, N convex portions 250 extend in the axial direction AD. The N projections 250 are arranged at intervals in the circumferential direction CD. As long as the first concave portion 162 (fig. 2) and the second concave portion 67 (fig. 3) are fitted to the convex portion 250, each convex portion 250 may be cut in the axial direction AD or may be continuous in the axial direction AD.

The rotating shaft 25 also has fixing member arrangement portions 251, 252, 253, 254. The fixing member arrangement portions 251 to 254 pass through the N projections 250 in the circumferential direction CD, respectively. The fixing member arrangement portions 251-254 are arranged at intervals in the axial direction AD. The fixing member arrangement portions 251 to 254 are recessed inward in the radial direction RD. The fixing members R1, R2, R3, and R4 in fig. 1 are disposed in the fixing member arrangement portions 251, 252, 253, and 254, respectively.

As described above with reference to fig. 2 to 4, according to embodiment 1, the protruding portion 250 provided on the rotating shaft 25 extends in the axial direction AD, and thereby the protruding portion 250 fits both the first recessed portion 162 of the rotor 15 and the second recessed portion 67 of the wave generator 60. Therefore, the rotational force of the motor 100 can be transmitted to the decelerator 200 using the rotation shaft 25 having a simple structure.

Next, a sealing structure between the motor body 10 and the reduction gear 200 will be described with reference to fig. 5, 6A, and 7. Fig. 5 is a longitudinal sectional view showing a part of the reduction gear SR of fig. 1 in an enlarged manner. In fig. 5, for the sake of simplicity, the fixing members R3 and R4 in fig. 1 are omitted.

Fig. 5 shows the inside of the speed reducer 200 in which grease is present. That is, the grease is filled in the interior of the speed reducer 200. For example, the decelerator 200 has spaces SP1, SP2, and SP 3. The grease filled the spaces SP1, SP2, and SP 3. Therefore, it is necessary to prevent grease of the speed reducer 200 from entering the motor main body 10. Because, in embodiment 1 in particular, the motor main body 10 and the reduction gear 200 are close to each other in the axial direction AD.

The second flange portion 20 of the motor main body 10 is located between the reduction gear 200 and the stator 11 and the rotor 15 of the motor main body 10. The second flange portion 20 faces the stator 11 and the rotor 15 of the motor main body 10 in the axial direction AD. The second flange portion 20 faces the rigid internally-toothed gear 40, the flexible externally-toothed gear 50, and the wave generator 60 of the reduction gear 200 in the axial direction AD.

Specifically, the second flange portion 20 includes a first ring portion 191 and a second ring portion 192. The first ring portion 191 is substantially annular. The first ring portion 191 is opposed to the rigid internally toothed gear 40 in the axial direction AD. The first ring portion 191 is fixed to the rigid internally toothed gear 40 in the axial direction AD. The first ring portion 191 contacts the rigid internally toothed gear 40 from the axial direction AD.

The second ring portion 192 is located radially inward of 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 internally toothed gear 40, the flexible externally toothed gear 50, and the wave generator 60 in the axial direction AD. The second ring portion 192 faces the stator 11 and the rotor 15 in the axial direction AD. The second ring portion 192 is separated from the rotor 15 in the axial direction AD. The second ring portion 192 extends from the first ring portion 191 inward in the radial direction RD. The front end portion of the second ring portion 192 is spaced apart from and opposed to the rotation shaft 25 in the radial direction RD.

The reduction gear SR also has a seal portion 90. The seal portion 90 seals between the reduction gear 200 and the motor main body 10 outside in the radial direction RD of the rotation shaft 25. Therefore, according to embodiment 1, grease of the speed reducer 200 can be prevented from entering the motor main body 10.

Fig. 6A is an enlarged longitudinal sectional view of the seal portion 90. That is, fig. 6A shows the region a of fig. 5 in an enlarged manner. As shown in fig. 6A, the seal portion 90 has a labyrinth structure. Specifically, the seal portion 90 includes a first labyrinth portion 91 and a second labyrinth portion 92. The first labyrinth portion 91 is provided on the axial direction AD side surface of the non-circular cam 65. The first labyrinth portion 91 has a convex-concave shape. On the other hand, the second labyrinth portion 92 is provided at the radial direction RD leading end portion of the second ring portion 192. The second labyrinth portion 92 is opposed to the first labyrinth portion 91 in the axial direction AD. The second labyrinth portion 92 has a convex-concave shape.

The convexo-concave shape of the first labyrinth portion 91 is engaged with the convexo-concave shape of the second labyrinth portion 92, thereby sealing between the decelerator 200 and the motor main body 10.

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

Next, another example of the seal portion 90 will be described with reference to fig. 6B to 6D. Fig. 6B is an enlarged longitudinal sectional view showing another example of the seal 90 (hereinafter, the seal 90A). As shown in fig. 6B, the seal portion 90A is constituted by an oil seal. The seal portion 90A is substantially annular surrounding the central axis AX. On the other hand, the second ring portion 192 is bent toward the axial direction AD at the front end 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 end portion 193 of the second ring portion 192. As a result, the space between the speed reducer 200 and the motor main body 10 is sealed by the sealing portion 90A.

Fig. 6C is an enlarged longitudinal sectional view showing still another example of the seal 90 (hereinafter, the seal 90B). As shown in fig. 6C, the seal portion 90B is formed of a V-ring. The seal portion 90B is substantially annular 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 leading end portion of the second ring portion 192. As a result, the space between the speed reducer 200 and the motor main body 10 is sealed by the sealing portion 90B.

Fig. 6D is an enlarged longitudinal sectional view showing still another example of the seal 90 (hereinafter, the seal 90C). As shown in fig. 6D, the sealing portion 90C is formed of an O-ring. The seal portion 90C is substantially annular 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 leading end portion of the second ring portion 192. As a result, the space between the speed reducer 200 and the motor main body 10 is sealed by the sealing portion 90C.

The structure of the sealing portions 90, 90A to 90C is not particularly limited as long as the sealing between the speed reducer 200 and the motor main body 10 can be achieved. In fig. 6A to 6D, the fixing member R3 of fig. 1 is omitted for the sake of simplicity.

Next, the reducer 200 will be described in detail with reference to fig. 1 and 3. The speed reducer 200 shown in fig. 1 and 3 is a device for reducing rotational motion input by a differential pair of the rigid internally-toothed gear 40 and the flexible externally-toothed gear 50. The reduction gear SR having the reduction gear 200 is incorporated in, for example, a bicycle, a joint of a small robot, an auxiliary set, a turntable, a dividing head of a machine tool, a wheelchair, or an unmanned carrier. However, the object in which the reduction gear SR is incorporated is not particularly limited.

As shown in fig. 1 and 3, the reduction gear 200 further includes an output rotary body 55, a housing 70, a bearing 80, a seal member 85, a fixed member R3, and a fixed member R4. Also, an input shaft of the decelerator 200 is the rotation shaft 25 of the motor 100. The output shaft of the reduction gear 200 is the output rotating body 55. The output rotary body 55 is, for example, a bushing.

The rigid internally-toothed gear 40 is a member that extends in a substantially annular shape around the central axis AX. The rigidity of the rigid internally-toothed gear 40 is higher than the rigidity of the cylindrical portion 51 of the flexible externally-toothed gear 50. Therefore, the rigid internally-toothed gear 40 can be regarded as a substantially rigid body. The rigid internally-toothed gear 40 has a plurality of internal teeth 41 on the inner peripheral surface. The plurality of internal teeth 41 are arranged at a constant pitch in the circumferential direction CD.

The flexible externally toothed gear 50 includes a flat plate portion 52 in addition to the cylindrical portion 51. The cylindrical portion 51 is a portion extending cylindrically in the axial direction AD around the central axis AX. The cylindrical portion 51 is a flexible cylindrical portion that can flex in the radial direction RD. One end portion in the axial direction AD of the cylindrical portion 51 is disposed inside the rigid internally-toothed gear 40 in the radial direction RD. The flat plate portion 52 is a flat plate-like portion that is less likely to flex than the cylindrical portion 51. The flat plate portion 52 is a portion that expands from the other end portion in the axial direction AD of the cylindrical portion 51 toward the inside in the radial direction RD.

The flexible externally toothed gear 50 has a plurality of external teeth 511 on the outer peripheral surface near one end. The plurality of external teeth 511 are arranged at a constant pitch in the circumferential direction CD. An output rotating body 55, which is an output shaft for extracting the decelerated power, is fixed to the flat plate portion 52.

In the wave generator 60, the non-circular cam 65 is a member annularly expanded centering on the central axis AX. The non-circular cam 65 is connected to the rotating shaft 25 as an input shaft. Therefore, the non-circular cam 65 rotates around the central axis AX at the rotation speed before deceleration by the rotation of the rotating shaft 25. In embodiment 1, the non-circular cam 65 has an elliptical cam profile. In other words, the non-circular cam 65 has different outer diameters according to the position in the circumferential direction CD. In other words, the outer edge of the non-circular cam 65 is substantially elliptical.

The non-circular cam 65 is sandwiched between the fixing member R3 and the fixing 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 inside the cylindrical portion 51 of the flexible externally toothed gear 50 in the radial direction RD. The wave bearing 61 is substantially annular. The wave bearing 61 is, for example, a ball bearing. The wave bearing 61 has an inner race 62, a plurality of balls 63, and an elastically deformable outer race 64. The inner race 62 is fixed to the outer peripheral surface of the non-circular cam 65. A plurality of balls 63 are interposed between the inner race 62 and the outer race 64, and are arranged in the circumferential direction CD. The outer race 64 is elastically deformed (flexural deformation) via the inner race 62 and the balls 63 so as to reflect the cam profile of the rotating non-circular cam 65. The outer race 64 is in contact with the inner peripheral surface of the cylindrical portion 51 of the flexible externally toothed gear 50 at the site having the external teeth 511. Specifically, the outer ring 64 is fixed to the inner circumferential surface of the cylindrical portion 51 at the portion having the external teeth 511. The wave generator 60 has different outer diameters according to the position in the circumferential direction CD, and rotates at the rotation speed before deceleration centering on the central axis AX inside the radial direction RD of the rigid internally-toothed gear 40.

The output rotary body 55 is fixed to the outer race 38 of the second bearing 35. Specifically, the second bearing 35 includes a cylindrical body 551 and a bearing holding portion 552. The bearing holding portion 552 holds the second bearing 35. Specifically, the outer ring 38 of the second bearing 35 is fixed to the inner circumferential surface of the bearing holding portion 552 in the radial direction RD. The cylindrical body 551 has a substantially cylindrical shape surrounding the central axis AX in the circumferential direction CD. The cylindrical body 551 extends in the axial direction AD.

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

Specifically, the housing 70 includes a substantially cylindrical first cylindrical portion 71, a substantially annular flat plate portion 72, and a substantially cylindrical second cylindrical portion 73. One end portion in the axial direction AD of the first cylindrical portion 71 faces the rigid internally-toothed gear 40 in the axial direction AD, and is fixed to the rigid internally-toothed gear 40. The first cylindrical portion 71 surrounds the central axis AX and extends in 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 center axis AX. The second cylindrical portion 73 extends in the axial direction AD from the inner end portion in the radial direction RD of the flat plate portion 72. The second cylindrical portion 73 surrounds the central axis AX and extends in the axial direction AD.

The seal member 85 has a substantially annular shape. The seal member 85 is disposed between the inner circumferential surface of the second cylindrical portion 73 and the outer circumferential surface of the cylindrical body 551. The sealing member 85 seals between the inner circumferential surface of the second cylindrical portion 73 and the outer circumferential surface of the cylindrical body 551. The seal member 85 is, for example, an oil seal. The sealing member 85 prevents grease present inside the speed reducer 200 from leaking to the outside.

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

In the reduction gear 200 configured as described above, when the rotation shaft 25 of the motor 100 rotates at the rotation speed before reduction, the non-circular cam 65 rotates at the rotation speed before reduction. That is, the non-circular cam 65 rotates at the same rotational speed as that of the rotating shaft 25. Then, as the non-circular cam 65 rotates, the inner peripheral surface of the portion having the external teeth 511 of the cylindrical portion 51 of the flexible externally toothed gear 50 is pressed via the wave bearing 61, whereby the cylindrical portion 51 is deformed in an elliptical shape by flexing. 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) in the vicinity of two positions in the radial direction RD on the outer side of the two ends of the major axis of the ellipse formed by the non-circular cam 65. As a result, the external teeth 511 mesh with the internal teeth 41 in the vicinity of two radially outer sides RD at both ends of the major axis of the ellipse.

When the non-circular cams 65 rotate, the positions of both ends of the major axis of the ellipse formed by the non-circular cams 65 move in the circumferential direction CD, and the meshing portions of the external teeth 511 and the internal teeth 41 also move in the circumferential direction CD. Here, the number of teeth of the internal teeth 41 of the rigid internally-toothed gear 40 is slightly different from the number of teeth of the external teeth 511 of the flexible externally-toothed gear 50. Therefore, the meshing portion of the internal teeth 41 and the external teeth 511 slightly changes every time the non-perfectly circular cam 65 rotates one revolution. As a result, the flexible externally toothed gear 50 and the output rotary body 55 rotate at the reduced rotation speed with respect to the rigid internally toothed gear 40. That is, the flexible externally toothed gear 50 and the output rotor 55 rotate relative to the rigid internally toothed 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 externally toothed gear 50 and the internal teeth 41 of the rigid internally toothed gear 40 in the circumferential direction CD.

In the reduction gear 200 described with reference to fig. 1 and 3, the flexible externally toothed gear 50 is described as an example of the "flexible member", and the rigid internally toothed gear 40 is described as an example of the "annular member". However, the "flexible member" and the "annular member" are not particularly limited as long as the rotational motion at the first rotational speed can be converted into the rotational motion at the second rotational speed lower than the first rotational speed. For example, when the reduction gear 200 performs reduction using traction (friction), the "flexible member" may have flexibility but may not have external teeth, and the "annular member" may have elasticity but may not have internal teeth. In this case, the outer peripheral surface of the "flexible member" and the inner peripheral surface of the "annular member" are in contact with each other via an oil film of lubricating oil.

(embodiment mode 2)

A bicycle 300 according to embodiment 2 of the present invention will be explained with reference to fig. 8 and 9. The bicycle 300 according to embodiment 2 is equipped with the reduction gear SR described with reference to fig. 1. Therefore, the description of the reduction gear SR will be appropriately omitted below.

Fig. 8 is a diagram showing a bicycle 300 of embodiment 2. As shown in fig. 8, the bicycle 300 has a front wheel 310, a rear wheel 320, pedals 330, crank arms 340, a roller chain 350, and a reduction gear SR. The pedals 330 are respectively disposed on both sides of the bicycle 300. The crank arms 340 are respectively disposed on both side surfaces of the bicycle 300. The pedal 330 is rotatably attached to a crank arm 340. Hereinafter, one of the rotation directions of the pedal 330 is referred to as "forward direction". When the user pedals the pedal 330 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 travels forward by 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 side surfaces of the bicycle 300. The reduction gear SR is disposed inside a chain cover 351 that covers the roller chain 350. For example, when the load on pedal 330 is large at the time of departure or traveling on an uphill road, reduction gear SR supplies a forward rotational driving force to pedal 330. That is, the reduction gear SR functions as an electric assist device. Therefore, the force of the user pedaling the pedal 330 is reduced. As a result, the user can easily drive the bicycle 300.

In the present embodiment, since the bicycle 300 is provided with the reduction gear SR capable of reducing the length in the axial direction AD, the length in the axial direction of the bicycle 300 can be reduced. In particular, according to embodiment 2, the bicycle 300 is provided with the reduction gear SR capable of reducing the length in the axial direction AD, and therefore, an increase in weight of the bicycle 300 can be suppressed. Further, since the axial direction AD of the reduction gear SR is short, the reduction gear SR does not interfere with the operation, and the user can easily step on the pedal 330.

Fig. 9 is a longitudinal sectional view showing the reduction gear SR mounted to the bicycle 300. Bicycle 300 has a reduction gear SR, pedals 330, crank axle 360, and sprocket 370. In this embodiment, as shown in fig. 9, the bicycle 300 further includes a crank axle 360, a sprocket 370, a one-way clutch 380, a bearing 385 and a bearing 390. In addition, the crank shaft 360 is shown in white for ease of viewing the drawings.

The crankshaft 360 is a substantially cylindrical member extending along the central axis AX. The crank shaft 360 penetrates the rotation shaft 25 of the reduction gear SR in the axial direction AD. Crank shaft 360 passes through rotary shaft 25 and output rotary body 55 of reduction gear SR in axial direction AD. Crank shaft 360 is driven by a pedaling force from pedal 330 (fig. 8).

Both ends of crankshaft 360 in axial direction AD protrude outward of reduction gear SR. Crank arms 340 are fixed to both ends of the crank shaft 360 in the axial direction AD. When a user of the bicycle 300 pedals 330 (fig. 8) connected to the crank arm 340, the pedal force (manual force) causes the pedals 330, the crank arm 340, and the crank shaft 360 to rotate about the central axis AX.

An output shaft of the reduction gear SR is connected to the sprocket 370. The sprocket 370 is connected to the output rotary body 55, which is the output shaft of the reduction gear 200. Specifically, the sprocket 370 is fixed to the output rotating body 55, which is the output shaft of the reduction gear 200. The sprocket 370 is substantially orthogonal to the axial direction AD. The sprocket 370 transmits the rotation of the crankshaft 360, which is transmitted through the one-way clutch 380 and the output rotary body 55, to the roller chain 350. The sprocket 370 has a substantially disc shape centered on the central axis AX. The sprocket 370 has a plurality of outer teeth on the outer peripheral portion. The sprocket 370 engages with the roller chain 350 of the bicycle 300 via a plurality of external teeth. When crankshaft 360 is rotated by the depression force from pedal 330, sprocket 370 is rotated about central axis AX via one-way clutch 380 and output rotary body 55. As a result, the roller chain 350 rotates between the sprocket 370 and the rear wheel 320.

A bearing 385 and a bearing 390 are disposed 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 in the axial direction AD. The bearings 385 and 390 rotatably support the crank shaft 360. Bearing 385 has an inner race 386, a plurality of balls 387, and an outer race 388. Inner race 386 is fixed to the outer peripheral surface of crank shaft 360. A plurality of balls 387 are interposed between inner race 386 and outer race 388 and are arranged in circumferential direction CD. The outer race 388 is fixed to the inner peripheral surface of the rotary shaft 25. Bearing 390 has an inner race 391, a plurality of balls 392, and an outer race 393. The inner race 391 is fixed to the outer peripheral surface of the crank shaft 360. A plurality of balls 392 are interposed between the inner race 391 and the outer race 393 and arranged in the circumferential direction CD. The outer race 393 is fixed to the inner peripheral surface of the rotating shaft 25.

The one-way clutch 380 is a mechanism that allows only the relative rotation of the output rotary body 55 with respect to the crank shaft 360 to be oriented in 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 peripheral surface of the output rotary body 55 and the outer peripheral surface of the crank shaft 360 in the radial direction RD.

The one-way clutch 380 allows rotation of the crankshaft 360 in the case where the forward rotational speed of the crankshaft 360 is greater than the forward rotational speed of the output rotary body 55. Therefore, when the motor 100 of the reduction gear SR is not driven, the user of the bicycle 300 can rotate the crank shaft 360 via the pedal 330 without receiving resistance of the motor 100. In this case, the sprocket 370 is rotated only by the rotational force of the crank shaft 360.

However, the one-way clutch 380 prohibits the forward rotational speed of the output rotary body 55 from being 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 rotary body 55 follows the forward rotational speed of the crankshaft 360, the crankshaft 360 rotates in the forward direction at the same rotational speed as the output rotary body 55.

The motor also has a controller 400 and a torque sensor 410. The torque sensor 410 detects strain of the crank shaft 360 in a non-contact manner, and converts the amount of strain into a torque value. The torque sensor 410 inputs a detection signal showing a torque value of the crank shaft 360 to the controller 400.

The controller 400 is mounted with a circuit for supplying a driving 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 showing the torque of the crank shaft 360 from the torque sensor 410. A preset torque threshold value is stored in the memory of the controller 400. The controller 400 does not supply the driving current to the coil 14 when the torque value indicated by the detection signal received from the torque sensor 410 is smaller than the threshold value. Therefore, the motor 100 is not driven. On the other hand, when the torque value indicated by the detection signal received from the torque sensor 410 becomes equal to or greater than the threshold value, the controller 400 generates a drive current corresponding to the torque value using the electric power supplied from the battery and supplies the drive current to the coil 14. As a result, the motor 100 is driven.

When the motor 100 is driven and the forward rotational speed of the output rotary body 55 is smaller than the forward rotational speed of the crank shaft 360, the rotational force decelerated based on the rotational force of the motor 100 is transmitted to the output rotary body 55. As a result, the sprocket 370 is rotated by the rotational force decelerated based on the rotational force of the motor 100 and the rotational force of the crank shaft 360 generated by the pedaling force of the user.

On the other hand, in the case where the motor 100 is driven and the forward rotational speed of the output rotary body 55 is greater than the forward rotational speed of the crank shaft 360, the one-way clutch 380 acts so that the sprocket 370 is rotated only by the rotational force of the crank shaft 360 generated by the pedaling force of the user.

The embodiments of the present invention have been described above 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 scope of the invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, several constituent elements may be removed from all the constituent elements shown in the embodiments. For example, the constituent elements in the different embodiments may be appropriately combined. For convenience of understanding, the drawings schematically show the main body of each component, and for convenience of drawing, the thickness, length, number, interval, and the like of each component shown in the drawings may be different from those of the actual drawings. The material, shape, size, and the like of each component shown in the above embodiments are examples and are not particularly limited, and various modifications can be made within a range not substantially departing from the effect of the present invention.

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

Claims (6)

1. A reduction gear unit comprising:

a motor; and

a decelerator decelerating a rotation speed of the motor,

the motor includes a motor main body, a rotating shaft rotating around a central axis, a first bearing and a second bearing,

the speed reducer has:

a wave generator having different outer diameters according to positions in a circumferential direction and rotating around the central axis;

a flexible member having a flexible cylindrical portion with which the wave generator is contacted from a radially inner side; and

an annular ring member, the cylindrical portion contacting the ring member from a radially inner side,

the flexible member relatively rotates with respect to the ring-shaped member in accordance with the rotation of the wave generator,

the motor main body has a rotor connected to the rotating shaft,

the wave generator is connected to the rotating shaft at a position different from a position where 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 inward of the cylindrical portion and rotatably supports the rotating shaft.

2. A reduction gear unit according to claim 1,

the number of poles of the motor is N, N is an integer of 2 or more,

the rotor has a first connection portion connected with the rotation shaft,

the first connecting portion has N first recesses connected in the circumferential direction,

the N first concave parts are respectively concave towards the radial outer side and extend along the axial direction,

the wave generator has a second connecting portion connected to the rotary shaft,

the second connecting portion has N second recesses connected in the circumferential direction,

the N second concave parts are respectively concave towards the radial outer side and extend along the axial direction,

the first recess and the second recess are aligned in a straight line in the axial direction,

the rotating shaft has N convex parts protruding towards the radial outside,

the N convex parts extend along the axial direction, are embedded with the N first concave parts and are embedded with the N second concave parts.

3. A reduction gear unit according to claim 1 or 2,

the second bearing is disposed on an opposite side of the rotor with respect to the wave generator.

4. A reduction gear unit according to any one of claims 1 to 3,

further has a seal portion that seals between the speed reducer and the motor main body on a radially outer side of the rotating shaft,

grease exists in the speed reducer.

5. A reduction gear unit according to any one of claims 1 to 4,

the rotating shaft is hollow.

6. A bicycle, having:

a reduction device as claimed in any one of claims 1 to 5;

a pedal;

a crank shaft axially penetrating the rotating shaft of the reduction gear and driven by a pedaling force from the pedals; and

and the chain wheel is connected with an output shaft of the speed reducing device.

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