TW202434489A - Mid drive inner rotor motor and drive device for pedal assisted bicycle - Google Patents

Abstract

The present invention is a pedal assisted driving device for an electric bicycle. The device of the present invention includes a housing, a crankshaft, an inner-rotor motor, a cycloid gear reduction mechanism, an output shaft assembly, a Hall sensor assembly, and a spider chainring seat assembly. The crankshaft, the hollow shaft of the inner rotor, the center of the annular gear seat, the low rpm output shaft, the one-way output shaft, and the one-way bearing are all located on the same axis, and the outer diameter of the crankshaft is smaller than all other rotation shafts. One end of the hollow shaft of the inner rotor is provided with an eccentric shaft, a bearing is provided on the eccentric shaft, a cycloidal disc is provided on the outer diameter of the bearing, and an annular gear seat is provided on the outer circumference of the cycloidal disc. The outer diameter of the cycloidal disc is smaller than the inner diameter of the annular gear. Therefore, the cycloid disc rotates on the eccentric shaft and at the same time, revolves around the center of the annular gear seat. The device of the invention drives the output shaft and the spider chainring through the cycloid disc and has the effects of small size, lightweight, high reduction ratio, high torque, and low cost.

Description

Inboard rotor motor and drive device for electric bicycle

The present invention relates to a power transmission device for an electric-assisted bicycle.

At present, the power transmission methods of electric assisted bicycles include front wheel hub motor, rear wheel hub motor, mid-mounted motor, and tubular motor. Among them, the transmission efficiency of the mid-mounted motor is the best, so the electric assisted bicycle tends to be mainly mid-mounted motor. The known mid-mounted motor device needs to be reduced from high speed to low speed. The output torque will increase after the speed reduction, which is beneficial for riding on steep mountain slopes. Due to the spatial position limitation of the mid-mounted motor device, the motor output shaft and the pedal crankshaft cannot be on the same axis. Usually, they are two parallel axis. The motor power transmission is transmitted through the reduction gear set or the planetary gear set, and then transmitted to the star chain plate seat or chain plate after reduction. The conventional mid-mounted motor has the disadvantages of large size, heavy weight, low transmission efficiency of the compound gear system, complex mechanism, high price, and high rotation noise. The mid-mounted motor designed by the present invention abandons the compound gear system transmission mode and uses a small and light cycloidal gear reduction mechanism instead. All transmission parts are arranged on the same axis, with high transmission efficiency, compact structure, low rotation noise, etc., which can effectively improve the conventional technical shortcomings.

The device of the present invention comprises a housing, a crankshaft assembly, an inner rotor motor, a cycloidal gear reduction mechanism, an output shaft assembly, a Hall sensor assembly, and a star chain gear seat assembly. The housing comprises a left housing and a right housing; the crankshaft assembly comprises a crankshaft and two-end crank joints; the inner rotor motor comprises a hollow stator coil, an inner rotor comprising a hollow eccentric shaft; the cycloidal gear reduction mechanism comprises a cycloidal gear plate, an annular inner gear seat, and a bearing; the output shaft assembly It includes a reduction output shaft, a unidirectional output shaft, and a unidirectional bearing; the Hall sensor assembly includes a Hall sensor, a magnet ring seat, and a plurality of circular magnets; the star chain gear seat assembly includes a star chain gear seat, or a star chain gear seat including chain gears, or an integrated star chain gear.

The crankshaft, inner rotor hollow shaft, inner gear housing center, reduction output shaft, one-way output shaft, and one-way bearing are all located on the same axis, but the outer diameter of the crankshaft is smaller than the inner diameter of the inner rotor hollow shaft, the inner diameter of the reduction output shaft, the inner diameter of the one-way output shaft, and the inner diameter of the one-way bearing.

An eccentric shaft is arranged at one end of the hollow shaft of the inner rotor, a bearing is arranged on the eccentric shaft, a cycloid gear is arranged on the outer diameter of the bearing, an annular inner gear seat is arranged on the outer circumference of the cycloid gear, the outer diameter of the cycloid gear is smaller than the annular inner gear seat, the cycloid gear rotates with the eccentric shaft as the center, and revolves around the center of the annular inner gear seat. There are two ways of power output of the present invention: the first way is pedal crank → crank shaft → one-way bearing → one-way output shaft → star chain gear seat, or chain gear. The second approach is: motor inner rotor shaft → eccentric shaft → cycloidal gear disc → speed reduction output shaft → unidirectional output shaft → star chain gear seat or chain gear. The present invention has a reasonable and compact structure, small size, light weight, low noise, and no bulky and complex gear set or planetary gear set.

The design principle of the cycloid gear reduction mechanism is that when the number of cycloid teeth is N, the number of teeth of the annular internal gear seat is N+1. When the cycloid gear rotates N times, it also orbits the annular internal gear seat once. At this time, the output shaft rotates once, so the speed reduction ratio is N:1. A single set of cycloid gear reduction mechanisms can easily achieve a high speed reduction ratio. Although harmonic reduction gears can also achieve a high speed reduction ratio, the harmonic reduction gear design uses pointed teeth, which have a very low torque transmission value, and the tooth tips are easily damaged and broken, leading to mechanism damage problems. The cycloid teeth are continuous cycloids without sharp teeth, which can transmit very high torque. The engagement between the cycloid teeth and the annular inner gear seat is continuous contact, so there is relatively no instantaneous contact and collision. The operating noise is very low, and compared with the compound reduction gear system, it is less likely to cause space configuration difficulties.

The present invention uses an inner rotor brushless DC motor. Compared with an outer rotor motor, under the same outer frame size and outer frame diameter, the inner rotor motor can be designed with a thicker silicon steel sheet thickness and winding copper wire length, so that the torque output of the inner rotor motor is greater than that of the outer rotor motor of the same volume, and the inner rotor has better balance at high speed and is easy to install. Compared with the bulky and complex compound gear system, the use of the inner rotor motor can achieve the effect of increasing the output torque in consideration of the configuration in a limited space and reducing the total volume and weight.

The present invention uses only one one-way bearing (or one-way ratchet), while conventional devices mostly use two one-way bearings, which are respectively mounted on the pedal crank shaft and the motor through the speed reduction mechanism to the output shaft. The present invention only mounts one one-way bearing on the pedal crank shaft, and the motor through the speed reduction mechanism to the output shaft is directly connected to the one-way output shaft, thus reducing the use of one one-way bearing, making the structure compact and reducing the weight of the structure.

The present invention can be installed at the bottom bracket axle of a bicycle to directly replace the bottom bracket axle.

1: Motor transmission mechanism housing

2: Crankshaft assembly

21: Crankshaft

22: Crank joint

3: Inner rotor brushless DC motor

31: Motor stator

32: Madane Rotor

33: Inner rotor hollow eccentric shaft

4: Swinging gear speed reduction mechanism

41: Swinging gear plate

42: Ring internal gear seat

43: Bearings

5: Output shaft assembly

51: Speed reduction output shaft

52: One-way output shaft

53: One-way bearing

6: Hall sensor set

61: Hall sensor

62: Magnetic ring seat

63: Multiple circular magnets

7: Star-shaped chain gear seat assembly

Figure 1 is a schematic diagram of the installation position of the present invention on an electric-assisted bicycle.

Figure 2 is a cross-sectional view of an embodiment of the present invention.

Figure 3 is a schematic diagram of the inner rotor including the eccentric shaft.

Figure 4 is a schematic diagram of the configuration of the cycloid gear plate and the annular internal gear seat.

Figure 5 is a schematic diagram of the configuration of the speed reduction output shaft and the one-way output shaft.

Figure 6 is a schematic diagram of the Hall sensor group configuration.

The diagrams used to illustrate the present invention only show the technical features and best implementation of the present invention. The diagrams are drawn as much as possible in accordance with the true proportions and accurate configuration positions. Although they are not perfect, they are not used to limit or restrict the technical features and best implementation of the present invention.

Please refer to Figures 1 and 2. Figure 1 is a schematic diagram of the installation position of the present invention used on an electric-assisted bicycle. The present invention is designed to replace the bottom bracket and can directly drive the chain gear plate through a control circuit and a battery pack, or the rider can drive the chain gear plate through a one-way bearing by pedaling with both feet. Figure 2 is a cross-sectional view of the present invention. The device of the present invention includes a housing 1, a crankshaft assembly 2, an inner rotor motor 3, a cycloidal gear reduction mechanism 4, an output shaft assembly 5, a Hall sensor assembly 6, and a star-shaped chain gear seat assembly 7. The housing 1 includes a left housing and a right housing 1; the crankshaft assembly 2 includes a crankshaft 21 and two crank joints 22; the inner rotor brushless DC motor 3 includes a hollow stator coil 31, an inner rotor 32 including a hollow eccentric shaft 33; the cycloidal reduction mechanism 4 includes a cycloidal gear disc 41, an annular inner gear seat 42, and a bearing 43; the output The output shaft assembly 5 includes a reduction output shaft 51, a one-way output shaft 52, and a one-way bearing 53; the Hall sensor assembly 6 includes a Hall sensor 61, a magnet ring seat 62, and a plurality of circular magnets 63; the star chain gear seat assembly 7 includes a star chain gear seat, or a star chain gear seat including chain gears, or an integrated star chain gear.

The crankshaft 21, the inner rotor hollow shaft 33, the center of the annular inner gear seat 42, the speed reduction output shaft 51, the one-way output shaft 52, and the one-way bearing 53 are all located on the same axis, and the outer diameter of the crankshaft 21 is smaller than the inner diameter of the inner rotor hollow shaft, the inner diameter of the speed reduction output shaft, the inner diameter of the one-way output shaft, and the inner diameter of the one-way bearing.

Please refer to Figure 3. An eccentric shaft 33 is provided at one end of the hollow shaft of the inner rotor 32. A bearing 43 is provided on the eccentric shaft. A cycloid gear 41 is provided on the outer diameter of the bearing. An annular inner gear seat 42 is provided on the outer circumference of the cycloid gear. The outer diameter of the cycloid gear is smaller than the annular inner gear seat, so the cycloid gear rotates with the eccentric shaft as the center and revolves around the center of the annular inner gear seat. When the inner rotor rotates, the eccentric shaft rotates at the same time. The bearing 43 and the cycloid gear 41 are installed on the eccentric shaft. The design of the eccentric shaft and the cycloid gear makes the cycloid gear only rotate in the opposite direction and move forward one tooth when the inner rotor rotates one circle.

21 in FIG. 2 is a crankshaft, which runs through the entire transmission mechanism. Crank joints 22 are installed at both ends of the crankshaft 21 to respectively connect the left crank and the right crank. By stepping on the left and right cranks, the power can be transmitted to the one-way output shaft 52 through the one-way bearing 53, and then to the chain gear seat 7. There are two ways to output power in the present invention: the first way is to step on the crank → crankshaft 21 → one-way bearing 53 → one-way output shaft 52 → star-shaped chain gear seat, or chain gear 7. The second path is: the motor inner rotor 32 → eccentric shaft 33 → cycloidal gear 41 → speed reduction output shaft 51 → unidirectional output shaft 52 → star chain gear seat or chain gear 7. The present invention has a reasonable and compact structure, small size, light weight, low noise, and no bulky and complex gear set or planetary gear set.

Please refer to Figure 4, the configuration diagram of the cycloid gear disc 41 and the annular internal gear seat 42. The design principle of the cycloid gear reduction mechanism is that when the number of cycloid teeth is N, the number of teeth of the annular internal gear seat is N+1. When the cycloid teeth rotate 1 circle, the cycloid teeth only rotate in the opposite direction and advance 1 tooth in the annular internal gear seat. Therefore, when the cycloid gear disc rotates N circles, it also revolves in the opposite direction around the annular internal gear seat and advances N teeth. At this time, the output shaft rotates 1 circle in the opposite direction, so the speed reduction ratio is N:1.

Please refer to Figure 5. The reduction output shaft 51 can convert the circular rotation and revolution of the cycloid gear 41 into simple rotational motion. The speed of the reduction output shaft is 1/N times the design value. For example, when the design value N=30, the speed of the reduction output shaft will be reduced to 1/30 times. When the motor output speed is 3000rpm, the speed of the reduction output shaft is reduced to 100rpm (3000/30=100). A single set of cycloid reducers can easily achieve a reduction ratio of 1/30. After deceleration, the speed reduction output shaft 51 is directly connected to the one-way output shaft 52, and the star chain gear seat 7 is directly engaged and connected to the one-way output shaft without passing through any gear system in between.

The present invention uses a brushless DC motor. Since the rotation speed is too high to be used for direct transmission, a speed reduction mechanism is required to reduce the rotation speed. By using a single set of cycloid gear speed reduction mechanism, a high speed reduction ratio can be easily achieved. The cycloid gear shape is a continuous cycloid without sharp teeth, which can transmit high torque. The cycloid gear and the annular inner gear seat are in continuous contact, which is less likely to cause instantaneous contact and collision problems. The operating noise is very low. Compared with the compound reduction gear system, it is less likely to cause space configuration difficulties. The single-set pendulum deceleration mechanism designed and used in the present invention has its internal teeth directly manufactured into a roller shape. Whether a pinwheel is used on the annular internal gear seat or not, both designs will not affect the transmission effect and torque transmission efficiency.

Please refer to Figure 6. The present invention installs a Hall sensor assembly on the one-way output shaft, which includes a Hall sensor 61, a magnet ring seat 62, and a plurality of circular magnets 63. The Hall sensor is an ON/OFF type. Its main function is that when the crank is pedaled and the crank shaft 21 is rotated, the crank shaft 21 engages with the one-way bearing 53, the one-way bearing 53 engages with the one-way output shaft 52, and the one-way output shaft 52 engages with the star-shaped chain gear seat 7, thereby driving the transmission chain. The magnet ring seat 62 is mounted on the one-way output shaft 52 and rotates with the one-way output shaft. A plurality of circular magnets 63 are mounted on the magnet ring seat. When the circular magnet approaches the Hall sensor and triggers an ON state output, the controller conducts the DC power to the motor, causing the motor to rotate and generate electric power transmission. When the crankshaft 21 continues to rotate, causing the circular magnet to move away from the Hall sensor, the Hall sensor output is OFF, and the controller will turn off the power supply to the motor, and the motor stops transmitting. In this way, the two feet step on the crank alternately, the magnetic ring seat continues to rotate, the Hall sensor continues to turn on/off, and the motor can continue to provide assistance, helping the pedaler to ride in a more labor-saving way.

The present invention only installs a one-way bearing 53 (also called a one-way ratchet) on the pedal crank shaft 21, and the motor is directly connected to the one-way output shaft 52 via the speed reduction mechanism to the output shaft 51, thereby reducing the use of a one-way bearing, making the structure compact and reducing the weight of the structure. During the riding process, the inertial force of the bicycle forward, plus the rotational inertial force of the motor's inner rotor, can be used to offset the rotational inertia of the inner rotor while the two feet continue to pedal the cranks.

1: Motor transmission mechanism housing

2: Crankshaft assembly

21: Crankshaft

22: Crank joint

3: Inner rotor brushless DC motor

31: Motor stator

32: Inner rotor

33: Inner rotor hollow eccentric shaft

4: Swinging gear speed reduction mechanism

41: Swinging gear plate

42: Ring type internal gear seat

43: Bearings

5: Output shaft assembly

51: Speed reduction output shaft

52: One-way output shaft

53: One-way bearing

6: Hall sensor set

62: Magnetic ring seat

7: Star-shaped chain gear seat assembly

Claims (8)

An electric assisted bicycle driving device comprises: a housing, a crankshaft assembly, an inner rotor motor, a cycloidal gear reduction mechanism, an output shaft assembly, a Hall sensor assembly, and a star-shaped chain gear seat assembly. The housing includes a left housing and a right housing; the crankshaft assembly includes a crankshaft and two-end crank joints; the inner rotor motor includes a hollow stator coil and an inner rotor including a hollow eccentric shaft; the cycloid reduction mechanism includes a cycloid gear, an annular inner gear seat, and a bearing; the output shaft assembly includes a reduction output shaft, a one-way output shaft, and a one-way bearing; the Hall sensor assembly includes a Hall sensor, a magnet ring seat, and a plurality of circular magnets; the star chain gear seat assembly includes a star chain gear seat, or a star chain gear seat including chain gears, or an integrated star chain gear seat. As described in item 1 of the patent application scope, the electric power-assisted bicycle drive device, wherein the inner rotor motor is an inner rotor brushless DC motor. As described in item 1 of the patent application scope, the electric-assisted bicycle drive device, wherein the crankshaft, the inner rotor hollow shaft, the inner gear seat center, the reduction output shaft and the one-way output shaft are all located on the same axis, and the outer diameter of the crankshaft is smaller than the inner diameter of the inner rotor hollow shaft, the inner diameter of the reduction output shaft, the inner diameter of the one-way output shaft, and the inner diameter of the one-way bearing. As described in item 1 of the patent application scope, the electric-assisted bicycle drive device, wherein an eccentric shaft is provided at one end of the hollow shaft of the inner rotor, a bearing is provided on the eccentric shaft, a cycloid gear is provided on the outer diameter of the bearing, and an annular inner gear seat is provided on the outer circumference of the cycloid gear. The outer diameter of the cycloid gear is smaller than the annular inner gear seat, so the cycloid gear rotates with the eccentric shaft as the center and revolves around the center of the annular inner gear seat. As described in item 1 of the patent application scope, the electric-assisted bicycle drive device, wherein the cycloid gear can be one cycloid gear, or a plurality of cycloid gears of more than two. As described in item 1 of the patent application scope, the annular inner gear seat in the oscillating deceleration mechanism can be a needle wheel, a needle roller, a needle bearing, or a roller shape is directly manufactured on the annular inner gear seat. As described in item 1 of the patent application scope, the electric-assisted bicycle drive device, wherein the reduction output shaft is driven to rotate by the cycloidal gear disc, the reduction output shaft is directly engaged with the one-way output shaft to rotate together, and the one-way output shaft is directly engaged with the star-shaped chain gear seat assembly to rotate together. As described in item 1 of the patent application scope, an electric assisted bicycle driving device is provided on the unidirectional output shaft, wherein a Hall sensor assembly is provided, which includes a Hall sensor, a magnetic ring seat, and a plurality of circular magnets.

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