TWI867442B - Mid drive out rotor motor and drive device for pedal assisted bicycle - Google Patents

Abstract

The present invention is a driving device for a pedal assisted electric bicycle. The device of the present invention includes a housing, a crankshaft, an out-rotor motor, a cycloid gear reduction mechanism, an output shaft assembly, a Hall sensor assembly, and a chainring seat assembly. The crankshaft, the hollow shaft of the out 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 out 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 chainring through the cycloid disc and has the effects of small size, lightweight, high reduction ratio, high torque, and low cost.

Description

Electric bicycle center-mounted external rotor motor and drive device

The present invention relates to a power transmission device for an electric power-assisted bicycle with a centrally mounted external rotor motor.

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 mid-mounted motor has the best transmission efficiency, 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 chain plate seat set after deceleration. 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 present invention is used to replace the bottom bracket shaft. The device of the present invention comprises an outer housing, a crankshaft assembly, an outer rotor motor, a cycloidal gear reduction mechanism, an output shaft assembly, a Hall sensor assembly, and a chain gear seat assembly. The outer shell is used to fix and support the components contained therein; the crankshaft assembly includes a crankshaft and two-end crank joints; the outer rotor motor includes a hollow stator coil, an outer rotor including a hollow eccentric shaft, and the outer diameter of the outer rotor is smaller than the inner diameter of the outer shell so that there is no interference when the outer rotor rotates; 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; and a chain gear seat assembly.

The crankshaft, outer rotor including the hollow eccentric shaft, the center of the annular inner gear seat, the reduction output shaft, the one-way output shaft, and the 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 outer rotor, 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.

One end of the outer rotor is provided with a hollow eccentric shaft, a bearing is provided on the hollow eccentric shaft, a cycloid gear is provided on the outer diameter of the bearing, an annular inner gear seat is provided on the outer circumference of the cycloid gear, and the annular inner gear seat is fixed on the inner side of the outer shell. According to the cycloid gear reduction mechanism design equation, when the number of teeth of the annular inner gear seat is N+1, the number of teeth of the cycloid gear plate that engages with the annular inner gear seat must be N. According to the cycloid gear design equation, the reduction ratio generated when the two engage and rotate must be N. Therefore, the outer diameter of the cycloid gear plate is smaller than the annular inner gear seat. The cycloid gear plate rotates with the hollow eccentric shaft as the center, and revolves around the center of the annular inner gear seat. The power output of the present invention has two ways: the first way is when there is no power source (for example, when the power is exhausted or there is no battery power), the pedal crank → crank shaft → one-way bearing → one-way output shaft → chain gear seat assembly. The second way is when there is a power source, the pedal crank → crank shaft → one-way bearing → one-way output shaft → Hall sensor assembly → outer rotor → hollow eccentric shaft → cycloidal gear → reduction output shaft → one-way output shaft → chain gear seat assembly. The present invention has a reasonable and compact structure, small size, light weight, low noise, and no bulky and complicated gear set or planetary gear set.

According to the design equation of the cycloid gear reduction mechanism, when the number of teeth of the annular internal gear seat is N+1, the number of cycloid teeth is N. 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 outer rotor (brushless DC) motor. Compared with an inner rotor motor, under the same size, outer diameter of the outer shell, thickness of the silicon steel sheet, and winding conditions, the outer diameter of the outer rotor must be larger than that of the inner rotor. Therefore, the outer rotor motor can output a higher torque (torque value is force x radius). Therefore, considering the configuration in a limited space, the use of an outer rotor motor can achieve the effect of increasing the output torque.

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 installed on the pedal crankshaft and the motor through the speed reduction mechanism to the output shaft. The present invention only installs one one-way bearing on the pedal crankshaft, and the motor is directly connected to the one-way output shaft through the speed reduction mechanism to the output shaft, so the use of one one-way bearing is reduced, making the structure compact and reducing the weight of the structure. As the name suggests, the one-way bearing can only transmit power when rotating in the forward direction, and will idle when rotating in the reverse direction and will not output power. The installation method is set to the forward direction of the bicycle. This one-way bearing has two functions: the first function is that when the outer rotor motor has no output power, the two feet step on the crank and drive the crank shaft to rotate in the positive direction. The positive rotation of the crank shaft drives the one-way bearing to drive the one-way output shaft and the chain gear seat assembly; the second function is that when the outer rotor motor has output power, the output power is transmitted to the reduction output shaft, the one-way output shaft, and the chain gear seat assembly in sequence, and when the speed of the one-way output shaft is greater than the speed of the pedal crank shaft, the one-way bearing causes the crank shaft to disengage in the reverse direction.

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

100: Electric bicycle

101: Center-mounted outer rotor brushless DC motor and drive device

102: Complete bicycle

103: Original bicycle bottom bracket axle position

1: Shell

2: Crankshaft assembly

21: Crankshaft

22: Crank joint

3: External rotor motor

31: External rotor

32:Hollow stator coil

33: Hollow eccentric shaft

4: Swinging gear speed reduction mechanism

41: Swinging gear plate

42: Ring-shaped internal gear seat

421: The inner teeth of the annular inner gear seat are liquid

422: Roller

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: Chain and 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 outer rotor with a hollow 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 reduction output shaft and the one-way output shaft.

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

Figure 7 is a schematic diagram of the direct machining of the roller of the annular internal gear seat.

Figure 8 is a schematic diagram of an odd-numbered pendulum gear.

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 power-assisted bicycle. The centrally mounted external rotor (brushless DC) motor and drive device 101 are designed to replace the bottom bracket shaft, and can directly drive the chain gear seat assembly through the control circuit and battery pack, or the rider can drive the chain gear seat assembly 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 an outer housing 1, a crankshaft assembly 2, an external rotor motor 3, a cycloidal gear reduction mechanism 4, an output shaft assembly 5, a Hall sensor assembly 6, and a chain gear seat assembly 7. The center of the outer shell 1 is concentric with the crankshaft; the crankshaft assembly 2 includes a crankshaft 21 and two-end crank joints 22; the outer rotor motor 3 includes a hollow stator coil 32, and an outer rotor 31 includes a hollow eccentric shaft 33; the cycloid reduction mechanism 4 includes a cycloid gear 41, an annular inner gear seat 42, and a bearing 43; 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; and a chain gear seat assembly 7. The center of the outer shell is the crankshaft axis, and the hollow stator coil, outer rotor including the hollow eccentric shaft, cycloid gear, annular inner gear seat, speed reduction output shaft, one-way output shaft, one-way bearing, magnet ring seat, multiple circular magnets, chain gear seat assembly, etc. all rotate around the crankshaft axis. The outer rotor motor is installed on the left side of the outer shell, and the cycloid gear reduction mechanism, output shaft assembly, Hall sensor assembly, chain gear seat assembly are installed from left to right, and the crankshaft passes through the axis of the drive device.

Among them, both feet must step on the crankshaft to drive the one-way output shaft and the magnetic ring seat at the same time, so that the Hall sensor triggers the ON/OFF signal to the external controller, and the external controller provides power to the outer rotor motor to output the speed and torque. When both feet stop stepping on the crankshaft, the controller immediately turns off the power supply, and the outer rotor motor immediately loses the power source.

Please refer to Figure 2. The crankshaft 21, the outer rotor 31, the hollow eccentric shaft 33, the center of the annular inner gear seat 42, the 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 outer rotor, 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.

Please refer to FIG. 3 . In this embodiment, the outer diameter of the outer rotor is smaller than the inner diameter of the outer shell by more than 1 mm to avoid interference caused by the outer rotor contacting the outer shell during rotation. In this embodiment, a hollow eccentric shaft 33 is provided at one end of the special rotor 31, a bearing 43 is provided on the hollow eccentric shaft, and a cycloid gear 41 (designed number of teeth is N) is provided on the outer diameter of the bearing. According to the design equation of the cycloid gear reduction mechanism, an annular inner gear seat 42 (designed number of teeth is N+1) is provided on the outer circumference of the cycloid gear 41 and fixed to the inner side of the outer shell. Therefore, the outer diameter of the cycloid gear 41 is smaller than the annular inner gear seat 42, so the cycloid gear rotates with the hollow eccentric shaft as the center and revolves around the center of the annular inner gear seat. When the outer rotor rotates, the hollow eccentric shaft rotates at the same time; the bearing 43 and the cycloid gear 41 are installed on the hollow eccentric shaft. The design of the hollow eccentric shaft and the cycloid gear makes the cycloid gear only rotate in the opposite direction and move forward one tooth when the outer rotor rotates one circle.

Please refer to the crankshaft 21 in Figure 2, 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 assembly 7. There are two ways to output power in the present invention: the first way is when there is no power source (for example, when the power is exhausted or there is no battery power), stepping on the crank → crankshaft 21 → one-way bearing 53 → one-way output shaft 52 → chain gear seat assembly 7. Path 2 is when there is a power source (sufficient battery power), pedal crank → crank shaft 21 → one-way bearing 53 → one-way output shaft 52 → Hall sensor 61 → outer rotor 31 → hollow eccentric shaft 33 → cycloidal gear 41 → reduction output shaft 51 → one-way output shaft 52 → chain gear seat assembly 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 plate 41 and the annular inner gear seat 42. The cycloid gear shape of the cycloid gear reduction mechanism is based on the cycloid gear design equation. The design principle is that when the number of teeth on the cycloid gear plate is N, the number of teeth on the annular inner gear seat is N+1. The annular inner gear seat is fixed to the inner side of the outer shell without When the cycloid gear plate rotates 1 circle, the cycloid gear plate only rotates in the opposite direction and advances 1 tooth in the annular inner gear seat. Therefore, when the cycloid gear plate rotates N circles, it also revolves in the opposite direction around the annular inner 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 a simple rotational motion. The speed of the reduction output shaft is 1/N times the design value. In this embodiment, the design value N=20 teeth, then the speed of the reduction output shaft will be reduced to 1/20 times. When the motor output speed is 2000rpm, the speed of the reduction output shaft is reduced to 100rpm (2000/20=100). A single set of cycloid reducers can easily achieve a reduction ratio of 1/20 or higher. After deceleration, the deceleration output shaft 51 is directly connected to the one-way output shaft 52, and the chain gear seat assembly 7 is directly engaged and connected to the one-way output shaft without passing through any gear system in between.

The present invention adopts an outer rotor (brushless DC) motor. Since the rotation speed is relatively high and cannot be used for direct transmission, a speed reduction mechanism needs to be installed 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 has a continuous cycloid shape without sharp teeth and can transmit high torque. The cycloid gear plate and the annular inner gear seat are in continuous contact, and there is relatively no problem of instantaneous contact and collision. The operating noise is very low. Compared with the compound reduction gear system, it is relatively unlikely to cause space configuration difficulties. Please refer to FIG7. The single-set pendulum deceleration mechanism used in the present embodiment has the inner teeth of the annular inner gear seat directly manufactured into a roller shape, see the annular inner gear seat 42. Generally, N+1 rollers 422 are placed in a concave hole in an annular configuration and fixed, and finally form an annular inner gear seat 421. In order to reduce the number of parts used, the present invention directly cuts all roller positions into a roller shape such as 42 by machining, so that in addition to reducing costs, it can also save maintenance time and expenses. The present invention does not use parts such as needle wheels, needle rollers, and needle bearings to simplify the design, reduce costs, and save maintenance costs. Please refer to Figure 8, this embodiment uses a single-number swing line gear 41.

Please refer to Figure 6 and Figure 2. The present invention installs a Hall sensor assembly on the one-way output shaft, which includes a Hall sensor 61, a magnetic ring seat 62, and a plurality of circular magnets 63. The Hall sensor is an ON/OFF type, and its main function is to detect whether there is double-foot stepping and the stepping frequency, and to send the ON/OFF message to the external controller. When the crank is stepped on by both feet and the crank shaft 21 is rotated, the crank shaft 21 is engaged with the one-way bearing 53, the one-way bearing 53 is engaged with the one-way output shaft 52, and the one-way output shaft 52 is engaged with the magnetic ring seat 62 and the chain gear seat assembly 7 at the same time, 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 61 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.

1: Shell

2: Crankshaft assembly

21: Crankshaft

22: Crank joint

3: External rotor motor

31: External rotor

32:Hollow stator coil

33: 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

61: Hall sensor

62: Magnetic ring seat

63: Multiple circular magnets

7: Chain and gear seat assembly

Claims (8)

A mid-mounted external rotor motor and drive device for an electric power-assisted bicycle comprises: an outer housing; a crankshaft assembly comprising a crankshaft and two crank joints; an external rotor motor comprising a hollow stator coil, an external rotor comprising a hollow eccentric shaft, the external rotor motor being arranged on the left side of the outer housing and being coaxial with the crankshaft; a cycloidal reduction mechanism comprising a cycloidal gear plate, an annular inner gear seat, and a bearing, the cycloidal reduction mechanism being arranged on the right side of the external rotor motor and being coaxial with the crankshaft. The crankshaft is coaxial with the crankshaft; an output shaft assembly includes a reduction output shaft, a unidirectional output shaft, and a unidirectional bearing. The output shaft assembly is installed on the right side of the cycloidal reduction mechanism and is coaxial with the crankshaft; a Hall sensor assembly includes a Hall sensor, a magnet ring seat, and a plurality of circular magnets, wherein the magnet ring seat and the plurality of circular magnets are installed on the outer circumference of the unidirectional output shaft and are coaxial with the crankshaft; a chain gear seat assembly is installed on the right side of the outer shell and is coaxial with the crankshaft. As described in Item 1 of the patent application scope, the mid-mounted outboard motor and drive device for an electric-assisted bicycle, wherein the outboard motor is an outboard brushless DC motor, the outer diameter of the outboard motor is slightly smaller than the inner diameter of the outer casing, and the outboard motor is placed on the left side of the outer casing. As described in Item 1 of the patent application scope, the mid-mounted external rotor motor and drive device for an electric-assisted bicycle, wherein the crankshaft, external rotor, hollow eccentric shaft, annular inner gear seat center, reduction output shaft and 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 external rotor and the hollow eccentric 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, the mid-mounted outer rotor motor and driving device of an electric assisted bicycle, wherein a hollow eccentric shaft is provided at one end of the outer rotor, a bearing is provided on the hollow eccentric shaft, and a cycloidal gear plate is provided on the outer diameter of the bearing. According to the design equation of the cycloidal gear reduction mechanism, when the number of teeth of the annular inner gear seat is N+1, then The number of teeth of the meshing cycloid gear must be N. According to the cycloid gear design equation, the reduction ratio generated when the meshing gears rotate must be N. Since the number of teeth N of the cycloid gear is less than the number of teeth N+1 of the annular inner gear seat, the outer diameter of the cycloid gear is smaller than the annular inner gear seat. The cycloid gear rotates around the hollow eccentric shaft and revolves around the center of the annular inner gear seat. As described in item 1 of the patent application scope, the mid-mounted external rotor motor and drive device for an electric-assisted bicycle, wherein the cycloid gear is a single cycloid gear. As described in Item 1 of the patent application scope, the mid-mounted external rotor motor and drive device for an electric assisted bicycle, wherein the roller shape is directly manufactured on the annular inner gear seat to reduce the number of parts, and is fixed to the inner side of the outer casing. As described in Item 1 of the patent application scope, the mid-mounted external rotor motor and driving device for an electric-assisted bicycle, wherein the reduction output shaft is driven to rotate by the cycloidal gear plate, 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 chain gear seat assembly to rotate together. As described in Item 1 of the patent application, the mid-mounted external rotor motor and drive device for an electric assisted bicycle, wherein a Hall sensor assembly is installed on the unidirectional output shaft, including a Hall sensor, a magnetic ring seat, and a plurality of circular magnets. The Hall sensor functions to detect whether both feet are pedaling and the pedaling frequency, and transmits ON/OFF information to an external controller.