A harmonic drive system and an electric power-assisted vehicle

Abstract

The present invention relates to the technical field of power-assisted bicycle transmission technology, and in particular to a harmonic drive system and an electric power-assisted bicycle. The present invention connects a rotation drive mechanism with a chain plate and a central shaft through a transmission gear device. The transmission gear device includes a wave generator, a flexible pulley and a rigid pulley to form a harmonic reducer, which can reduce the volume and weight of the reducer used in the electric power-assisted bicycle. In addition, the harmonic drive system can be installed in the frame, which can improve the aesthetic design of the appearance. In addition, the harmonic reducer formed by the wave generator, the flexible pulley and the rigid pulley has the advantages of high reduction ratio, high meshing rate, small size, light weight, low noise and high transmission accuracy, which can effectively improve the battery life of the electric power-assisted bicycle and ensure the smooth operation of the harmonic drive system, thereby improving the comfort of riding the electric power-assisted bicycle.

Description

Technical Field

[0001] The present invention relates to the technical field of power-assisted bicycle transmission technology, and in particular to a harmonic drive system and an electric power-assisted bicycle. Background Art

[0002] Power-assisted bicycles are a new type of two-wheeled vehicle, a type of bicycle. They use batteries as an auxiliary power source, are equipped with an electric motor, and feature a power-assist system, enabling them to integrate human power and motor assistance. Torque sensors are a core component of power-assisted bicycles' electric power systems, allowing them to understand the rider's intentions. The torque sensor allows the motor output of the e-bike to be adjusted based on the measured torque during riding, improving riding comfort.

[0003] Currently, the planetary gear transmission device of power-assisted bicycles has the following disadvantages: low deceleration ratio, heavy weight, large size, high noise and low transmission accuracy. Due to its low deceleration ratio and heavy weight, it requires a large power of the electric motor, which in turn affects the battery life. Summary of the Invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides: a harmonic transmission system of an electric power-assisted bicycle, which is installed in a frame and includes a transmission gear device and a rotation drive mechanism, wherein the transmission gear device includes: a wave generator, including a flexible bearing and an elliptical cam, the elliptical cam is arranged in the flexible bearing and causes the flexible bearing to be deformed into an elliptical shape, the rotation drive is connected to the elliptical cam and drives the elliptical cam to rotate; a flexible wheel, having an outer ring gear, the flexible bearing is sleeved in the flexible wheel and causes the flexible wheel to be deformed into an elliptical shape; a rigid wheel, having an inner ring gear meshing with the outer ring gear, the flexible wheel is driven by the elliptical cam to rotate relative to the rigid wheel; a steering gear set, having a first input part, a second input part and an output part, wherein the first input part is connected to the flexible wheel and rotates with the flexible wheel, and the output part is connected to the chain disc and drives the chain disc to rotate; a first one-way clutch, used to connect the second input part and the middle shaft.

[0005] Furthermore, the first input part includes a first connecting shaft and a first gear arranged at one end of the first connecting shaft, the second input part includes a second connecting shaft and a second gear arranged at one end of the second connecting shaft, and the first gear is meshed with the second gear.

[0006] Furthermore, at least one transmission gear set is provided between the output portion and the chain disc, and at least one transmission gear set is one or more of a spur gear, a bevel gear, a planetary gear train or a cycloid gear.

[0007] Furthermore, the rotation drive mechanism is a brushless DC motor or a brushed DC motor, and the rated speed of the rotation drive mechanism is greater than or equal to 4000 RPM and less than or equal to 10000 RPM.

[0008] Furthermore, a bearing pre-load device is included. A bearing is provided on one end of the flexible wheel away from the first input part. The bearing pre-load device is provided between the bearing and the housing of the rotation drive mechanism.

[0009] Furthermore, the bearing preload device is a wave spring.

[0010] Furthermore, it also includes a shell, the transmission gear device is arranged in the shell, and the rigid wheel is threadedly fixed to the shell.

[0011] Furthermore, it includes at least one first bearing, and one end of the first connecting shaft is sleeved in the first bearing and connected to the flexible spline.

[0012] Furthermore, the first gear and the first connecting shaft are connected via a second one-way clutch.

[0013] The first gear has a sleeve end, the second one-way clutch is arranged in the sleeve end, and one end of the first connecting shaft is inserted into the inner ring of the second one-way clutch.

[0014] Furthermore, the elliptical cam is connected to the output end of the rotation drive mechanism via a third one-way clutch.

[0015] The present invention also provides an electric power-assisted vehicle, comprising a frame, wherein the frame is provided with a high reduction ratio system, wherein the high reduction ratio system comprises a harmonic transmission system as in the above embodiment, and further comprises a cycloid gear and a small tooth difference transmission system, wherein the total reduction ratio of the high reduction ratio system is greater than or equal to 50 and less than or equal to 100.

[0016] The present invention mainly has the following beneficial effects:

[0017] The present invention connects the rotation drive mechanism with the chain plate and the central shaft through a transmission gear device. The transmission gear device includes a wave generator, a flexible pulley and a rigid pulley to form a harmonic reducer, which can reduce the volume and weight of the reducer used in the electric power-assisted bicycle, and the harmonic transmission system can be installed in the frame, which can improve the aesthetic design of the appearance. In addition, the harmonic reducer formed by the wave generator, the flexible pulley and the rigid pulley has the advantages of high reduction ratio, high meshing rate, small size, light weight, low noise and high transmission accuracy, which can effectively improve the battery life of the electric power-assisted bicycle and ensure the smooth operation of the harmonic transmission system, so as to improve the comfort of riding the electric power-assisted bicycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the harmonic drive system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Reference Figure 1 The harmonic drive system of an electric power-assisted bicycle shown in the figure includes a shell 101, a transmission gear device and a rotation drive mechanism 100, the shell 101 is installed on the frame, the transmission gear device is accommodated in the shell 101, the rotation drive mechanism 100 can be a brushless DC motor or a brushed DC motor, specifically, the transmission gear device includes a wave generator, a flexible wheel 203, a rigid wheel 204 and a steering gear set, the wave generator further includes a flexible bearing 201 and an elliptical cam 202, the steering gear set includes a first input part, a second input part and an output part, wherein the first input part is connected to the flexible wheel 203 and rotates with the flexible wheel 203 to drive the output part to output harmonic rotation, and the output part is connected to the chain disk of the electric power-assisted bicycle, and the second input part is connected to the middle shaft for transmitting the power of the middle shaft to the chain disk; in some embodiments, the flexible bearing 201 has The inner ring is used to accommodate the elliptical cam 202. When the elliptical cam 202 is placed in the inner ring, the flexible bearing 201 is deformed into an elliptical shape, whereby the elliptical cam 202 and the flexible bearing 201 are combined into a wave generator. The flexible wheel 203 has a first end and a second end, and the flexible wheel 203 is cup-shaped. The first end of the flexible wheel 203 is called the cup mouth, and the second end is called the cup bottom. The first end of the flexible wheel 203 has an outer gear ring. The wave generator is arranged in the first end and deforms the first end of the flexible wheel 203 into an elliptical shape. The rigid wheel 204 has an inner gear ring meshing with the outer gear ring, and the rigid wheel 204 is fixed to the housing 101; the wave generator, the flexible wheel 203 and the rigid wheel 204 are combined to form a harmonic reducer. The rotation drive mechanism 100 drives the elliptical cam 202 to drive the flexible wheel 203 to rotate in the rigid wheel 204 and relative to the rigid wheel 204, and can significantly reduce the output speed.

[0021] In some embodiments, the first input part includes a first connecting shaft 301 and a first gear 302 arranged at one end of the first connecting shaft 301. Specifically, the first gear 302 has an inner ring, and the first gear 302 is sleeved on one end of the first connecting shaft 301. Furthermore, a second one-way clutch 305 is arranged between the first gear 302 and the first connecting shaft 301. The first gear 302 has a sleeve end, and the second one-way clutch 305 is arranged in the sleeve end. One end of the first connecting shaft 301 is inserted into the inner ring of the second one-way clutch 305. The second one-way clutch 305 can be a conventional roller-type one-way clutch or a support-type one-way clutch. The end of the first connecting shaft 301 away from the first gear 302 is fixedly connected to the flexible wheel 203 and the first connecting shaft 301 rotates with the flexible wheel 203.

[0022] In some other embodiments, the sleeve ends of the first connecting shaft 301 and the first gear 302 for sleeve-engaging the second one-way clutch 305 are respectively sleeved in bearings.

[0023] The second input portion includes a second connecting shaft 303 and a second gear 304 disposed at one end of the second connecting shaft 303. The first gear 302 meshes with the second gear 304, and the second connecting shaft 303 is connected to the central shaft via a first one-way clutch 300. It should be noted that the output portion is located on the end of the second connecting shaft 303 relatively far from the second gear 304, that is, the second input portion and the output portion are both the second connecting shaft 303. In some embodiments, the output portion further includes a torque sensor 103, which is housed in the first one-way clutch 300 and is sleeved on the central shaft. The rotational axis of the first input portion and the second input portion is at 90°, that is, the first gear 302 and the second gear 304 can be connected by bevel gear meshing, or can be two halberd gears meshing, or an external gear meshing with a face gear, or a worm gear and a drum worm drive, or a turbine and a cylindrical worm drive, etc.

[0024] In some embodiments, at least one transmission gear set is further provided between the output portion and the chain disc, and at least one of the transmission gear sets is one or more of a spur gear, a bevel gear, a planetary gear system or a cycloid gear. Specifically, the wave generator, the flexible wheel 203 and the rigid wheel 204 form a harmonic reducer, that is, the harmonic transmission system of the present invention includes not only a first-order harmonic reducer and a second-order steering gear set, but also at least one third-order transmission gear set, as long as the total reduction ratio is greater than or equal to 50 and less than or equal to 100.

[0025] In some embodiments, the rated rotation speed of the rotary drive mechanism 100 is greater than or equal to 4000 RPM and less than or equal to 10000 RPM.

[0026] In some embodiments, a bearing preload device 102 is further included. A bearing is provided on the end of the flexible wheel 203 away from the first input part. The bearing preload device 102 is provided between the bearing and the housing of the rotation drive mechanism 100 to limit the movement of the flexible wheel 203 in the axial direction. Specifically, the bearing preload device 102 can be a wave spring.

[0027] In some embodiments, at least one first bearing is further included. One end of the first connecting shaft 301 is sleeved in the first bearing and connected to the flexible wheel 203. The first bearing can be a ball bearing or a needle bearing, wherein the ball bearing can be a deep groove ball bearing.

[0028] In some embodiments, a third one-way clutch (not shown) is further provided between the elliptical cam 202 and the rotation drive mechanism 100 . The third one-way clutch may be a one-way roller bearing.

[0029] The present invention also proposes an electric power-assisted vehicle, which includes a frame, and the frame has a high reduction ratio system. The high reduction ratio system includes a harmonic transmission system as in the above embodiment, and also includes a cycloid gear and a small tooth difference transmission system. The total reduction ratio of the high reduction ratio system is greater than or equal to 50 and less than or equal to 100. In some embodiments, the small tooth difference transmission system can be a small tooth difference meshing pair, a small tooth difference planetary gear transmission, or other structures.

[0030] In some embodiments, the electric power-assisted bicycle includes a frame, a bottom bracket and a chain plate, wherein the frame further includes an oblique tube, a middle tube and a bottom bracket tube. The end of the harmonic transmission system close to the wave generator is placed in the middle tube, and the end away from the wave generator is arranged in the bottom bracket tube. The rotation drive mechanism 100 is arranged in the middle tube close to the wave generator.

[0031] In some embodiments, the harmonic drive system further includes a battery, which may be a rechargeable battery and may be installed in the middle tube or the inclined tube. The battery is electrically connected to the rotary drive mechanism to provide the electrical energy required for the rotary drive mechanism 100 to operate.

[0032] It should be noted that the transmission chain of the harmonic drive system of the present invention is that the rotation drive mechanism 100 drives the elliptical cam 202 to rotate, and then drives the flexible spline 203 to rotate. One end of the first connecting shaft 301 is fixedly connected to the flexible spline 203, and the other end is provided with a first gear 302. The first connecting shaft 301 rotates with the flexible spline 203. One end of the second connecting shaft 303 is provided with a second gear 304, which meshes with the first gear 302. The other end is an output part, and the output part is connected to the chain disk; the second connecting shaft 303 is also sleeved with a first one-way clutch 300, and the first one-way clutch 300 is provided with a torque sensor 103. The torque sensor 103 has an inner ring that can accommodate the central shaft, and then the second connecting shaft 303 is connected to the central shaft through the first one-way clutch 300; the first connecting shaft 301 and the first gear 302 are connected by a second one-way clutch 305, and the elliptical cam 202 is connected to the output end of the rotation drive mechanism 100 by a third one-way clutch.

[0033] The harmonic drive system of the present invention uses a steering gear set and a harmonic reducer to reduce the volume and weight of the harmonic drive device, so that the harmonic drive system can be installed inside the frame, thereby improving the flexibility of the design and configuration of other parts. Compared with the traditional harmonic drive system structure that is hung on the outside of the frame, the harmonic drive system of the present invention can be hidden in the frame, which can improve the aesthetic design of the appearance. In addition, the harmonic reduction has the characteristics of high reduction ratio, high meshing rate, small size, light weight, low noise and high transmission accuracy, which can effectively improve the battery life and the smooth operation of the electric power-assisted bicycle, and enhance the riding comfort.

[0034] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A harmonic drive system, installed in a vehicle frame, characterized in that: It includes a transmission gear device and a rotation drive mechanism, wherein the transmission gear device includes: The wave generator includes a flexible bearing and an elliptical cam, wherein the elliptical cam is disposed in the flexible bearing and deforms the flexible bearing into an elliptical shape, and the rotation driving motor is connected to the elliptical cam and drives the elliptical cam to rotate; The flexible wheel is cup-shaped and has a first end and a second end. The first end of the flexible wheel is a cup mouth and the second end is a cup bottom. The first end of the flexible wheel has an outer gear ring. The flexible bearing is sleeved in the flexible wheel and makes the flexible wheel elliptical. A rigid wheel having an inner gear ring meshing with the outer gear ring, wherein the flexible wheel is driven by the elliptical cam to rotate relative to the rigid wheel; A steering gear set having a first input portion, a second input portion, and an output portion, wherein the first input portion is connected to the flexible spline and rotates with the flexible spline, and the output portion is connected to the chain disc and drives the chain disc to rotate; a first one-way clutch, configured to connect the second input portion and the middle shaft; At least one transmission gear set is further provided between the output portion and the chain disc, and at least one transmission gear set is one or more of a spur gear, a bevel gear, a planetary gear train or a cycloid gear; It also includes a bearing pre-load device. A bearing is provided on one end of the flexible wheel away from the first input part. The bearing pre-load device is provided between the bearing and the housing of the rotation drive mechanism.

2. A harmonic drive system according to claim 1, characterized in that: The first input part includes a first connecting shaft and a first gear arranged at one end of the first connecting shaft. The second input part includes a second connecting shaft and a second gear arranged at one end of the second connecting shaft. The first gear is meshed with the second gear.

3. The harmonic drive system according to claim 1, characterized in that: The rotation drive mechanism is a brushless DC motor or a brushed DC motor, and a rated speed of the rotation drive mechanism is greater than or equal to 4000 RPM and less than or equal to 10000 RPM.

4. The harmonic drive system according to claim 1, characterized in that: It also includes a shell, the transmission gear device is arranged in the shell, and the rigid wheel is threadedly fixed to the shell.

5. The harmonic drive system according to claim 2, characterized in that: The first gear is connected to the first connecting shaft via a second one-way clutch.

6. A harmonic drive system according to claim 5, characterized in that: The first gear has a sleeve end, the second one-way clutch is arranged in the sleeve end, and one end of the first connecting shaft is inserted into the inner ring of the second one-way clutch.

7. The harmonic drive system according to claim 2, characterized in that: The elliptical cam is connected to the output end of the rotation drive mechanism via a third one-way clutch.

8. An electric power-assisted vehicle, comprising a frame, characterized in that: The frame is provided with a high reduction ratio system, which includes the harmonic drive system according to any one of claims 1 to 7, and also includes a cycloid gear and a small tooth difference drive system. The total reduction ratio of the high reduction ratio system is greater than or equal to 50 and less than or equal to 100.

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