Middle motor for electric bicycle

Abstract

The utility model provides a middle motor for an electric bicycle, and relates to the technical field of middle motors. The cycloidal-pin gear speed reduction device comprises a machine shell, a transmission shaft, an output shaft, a motor assembly, a cycloidal-pin gear speed reduction assembly, a driving bevel gear and a driven bevel gear, the transmission shaft is arranged in the machine shell in the length direction of a vehicle frame, and the output shaft is arranged in the machine shell in the width direction of the vehicle frame; the motor assembly is in transmission connection with the end, away from the output shaft, of the transmission shaft and can drive the transmission shaft to rotate, the end, close to the output shaft, of the transmission shaft is in transmission connection with the power input end of the cycloidal-pin wheel speed reduction assembly, and the power output end of the cycloidal-pin wheel speed reduction assembly is in transmission connection with a driving bevel gear. The driven bevel gear is arranged on a shaft body of the output shaft and meshed with the driving bevel gear, one end of the output shaft extends out of the machine shell and is provided with a chain wheel, and the chain wheel can be in transmission connection with a wheel of the electric bicycle through a chain. According to the invention, the electric bicycle with the built-in motor is beautiful and light.

Description

Technical Field

[0001] This application relates to the technical field of mid-mounted motors, and in particular, to a mid-mounted motor for an electric bicycle. Background Art

[0002] A mid-mounted motor is a power source device commonly used in vehicles such as electric bicycles.

[0003] Existing mid-mounted motors generally include a housing, a motor assembly, a gear reduction box, a transmission shaft, and an output shaft. The transmission shaft and the output shaft are both arranged inside the housing along the width direction of the electric bicycle. The motor assembly is drivingly connected to one end of the transmission shaft, and the power input end of the gear reduction box is drivingly connected to the other end of the transmission shaft, so that the motor assembly can transmit power into the gear reduction box by driving the transmission shaft to rotate; one end of the output shaft extends out of the housing and is provided with a sprocket for connecting with a wheel through a chain. A driven gear is fixedly connected to the middle of the output shaft, and a driving gear is provided at the power output end of the gear reduction box. The driving gear and the driven gear are connected in a transmission manner by directly meshing or by arranging an intermediate gear between the two, so that the driving gear can drive the driven gear and the output shaft to rotate, and thus the output shaft can drive the sprocket and the wheel to rotate.

[0004] However, since most electric bicycles can only install the mid-mounted motor inside their own frames, and the gear reduction box and the motor assembly are relatively large in volume, the size of the mid-mounted motor in the width direction of the electric bicycle is relatively large. As a result, the frame must be designed very wide to meet the installation requirements of the mid-mounted motor, which makes these electric bicycles neither beautiful nor very cumbersome.

[0005] In view of this, there is a need to provide a mid-mounted motor for an electric bicycle. Summary of the Utility Model

[0006] In order to solve the problem that the existing mid-mounted motor is relatively large in size in the width direction of the frame, resulting in an overly wide frame of the electric bicycle using the mid-mounted motor, and thus making the electric bicycle neither beautiful nor very cumbersome, this application provides a mid-mounted motor for an electric bicycle.

[0007] This application provides a mid-mounted motor for an electric bicycle, adopting the following technical solutions: including a housing, a transmission shaft, an output shaft, a motor assembly, a cycloidal pinwheel reduction assembly, a driving bevel gear, and a driven bevel gear. The transmission shaft is arranged inside the housing along the length direction of the frame, and the output shaft is arranged inside the housing along the width direction of the frame;

[0008] The motor assembly is drivingly connected to one end of the transmission shaft away from the output shaft and can drive the transmission shaft to rotate. One end of the transmission shaft close to the output shaft is drivingly connected to the power input end of the cycloidal pinwheel reduction assembly. A driving bevel gear is drivingly connected to the power output end of the cycloidal pinwheel reduction assembly;

[0009] The driven bevel gear is arranged on the shaft body of the output shaft and meshes with the driving bevel gear. One end of the output shaft extends out of the machine shell through a relief hole opened on the machine shell and is provided with a sprocket, and this sprocket can be drivingly connected to the wheel of the electric bicycle through a chain.

[0010] By adopting the above technical solution, the cooperation of the driving bevel gear and the driven bevel gear not only realizes the driving connection between the cycloidal pinwheel reduction assembly and the output shaft, but also enables the transmission shaft to be arranged along the length direction of the vehicle frame. Subsequently, the cycloidal pinwheel reduction assemblies and the motor assemblies on both sides of the transmission shaft do not need to be arranged along the width direction of the vehicle frame. Coupled with the relatively small overall volume of the cycloidal pinwheel reduction assembly, the overall size of the mid-mounted motor for the electric bicycle in the width direction of the vehicle frame is relatively small, so that the electric bicycle adopting this mid-mounted motor does not need to design a wide vehicle frame, thus making the electric bicycle adopting this mid-mounted motor both beautiful and lightweight.

[0011] Further, the motor assembly includes a rotor and a stator. The rotor is connected to the transmission shaft, and a magnetic steel is arranged on the outer side of the rotor;

[0012] The stator is sleeved on the rotor and fixedly connected to the inner wall of the machine shell, and a coil adapted to the magnetic steel is arranged on the stator.

[0013] By adopting the above technical solution, the stator can drive the rotor to rotate through the coil, so as to drive the transmission shaft to rotate through the rotor, and then transmit the power to the cycloidal pinwheel reduction assembly through the transmission shaft.

[0014] Further, the motor assembly further includes a control board. An installation hole is opened at one end of the machine shell close to the motor assembly, and the control board is arranged in the installation hole and electrically connected to the stator.

[0015] By adopting the above technical solution, the controller on the electric bicycle can control the mid-mounted motor for the electric bicycle by being electrically connected to the control board.

[0016] Further, a jack for electrically connecting to the electric bicycle is arranged on the side of the control board facing away from the motor assembly.

[0017] By adopting the above technical solution, the wires of the controller on the electric bicycle can be electrically connected to the control board through the jacks, so that the controller can control the mid-mounted motor of the electric bicycle.

[0018] Furthermore, a magnetic member is provided at one end of the transmission shaft close to the control board, and a Hall sensor adapted to the magnetic member is provided on the control board.

[0019] By adopting the above technical solution, the Hall sensor can judge the position and speed of the rotor by sensing the magnetic poles on the magnetic member, so that the detection end of the Hall sensor does not need to extend between the stator and the rotor, thus facilitating the installation of the Hall plate sensor.

[0020] Specifically, the cycloid pinwheel reduction assembly includes an eccentric bushing, an external gear, an internal gear and an output sleeve. The eccentric bushing is press-fitted on the transmission shaft. The external gear is sleeved on the eccentric bushing, and a bearing is provided between the external gear and the eccentric bushing;

[0021] The internal gear is sleeved on the external gear and fixedly connected to the inner wall of the machine shell, and the internal teeth of the internal gear mesh with the external teeth of the external gear;

[0022] The output sleeve is rotatably sleeved on the transmission shaft. One side of the output sleeve away from the motor assembly is connected to the driving bevel gear. A connecting shaft is provided on one side of the output sleeve close to the motor assembly. A transmission hole is provided on the external gear. One end of the connecting shaft away from the output sleeve is inserted into the transmission hole and can slide along the inner wall of the transmission hole;

[0023] When the transmission shaft rotates, the eccentric bushing can drive the external gear to perform planetary rotation around the transmission shaft through rotation, so that the external gear drives the output sleeve and the driving bevel gear to rotate around the transmission shaft through the connecting shaft.

[0024] By adopting the above technical solution, when the transmission shaft rotates, the transmission shaft will drive the eccentric bushing to rotate together, so that the eccentric bushing can drive the external gear to perform a revolution around the transmission shaft. When the external gear performs a revolution in the clockwise or counterclockwise direction, the internal teeth of the internal gear will mesh with the external teeth of the external gear and drive the external gear to perform a self-rotation around its own rotation axis. The rotation direction of the self-rotation is opposite to the rotation direction of the revolution, so that the eccentric bushing drives the external gear to perform a planetary motion around the transmission shaft, and drives the output sleeve and the driving bevel gear to rotate through the cooperation of the transmission hole and the connecting shaft. Then, the power is transmitted to the driven bevel gear through the driving bevel gear, and finally the output shaft and the chain wheel are driven to rotate by the driven bevel gear.

[0025] Further, the output sleeve includes a large-diameter end and a small-diameter end. The transmission shaft is connected to the end of the large-diameter end. The driving bevel gear is sleeved on the small-diameter end, and a one-way bearing is provided between the driving bevel gear and the output sleeve.

[0026] By adopting the above technical solution, taking the forward direction of the wheel of the electric bicycle as the positive direction, when the output sleeve rotates in the positive direction, the outer ring and the inner ring of the first one-way bearing will be locked and rotate in the positive direction together, so that the output sleeve can drive the driving bevel gear to rotate in the positive direction together, and thus can drive the chain wheel and the wheel to rotate in the positive direction together.

[0027] Further, the output shaft includes a foot pedal shaft and an outer sleeve. Both ends of the foot pedal shaft extend out of the machine shell through the relief holes opened on the machine shell and can be connected to the foot pedals of the electric bicycle;

[0028] The outer sleeve is sleeved on the foot pedal shaft. One end of the outer sleeve is connected to the chain wheel, the other end of the outer sleeve is connected to the driven bevel gear, and a clutch is provided between the outer sleeve and the foot pedal shaft.

[0029] By adopting the above technical solution, the user can drive the foot pedal shaft to rotate in the positive direction by stepping on the foot pedal. At this time, the clutch between the outer sleeve and the foot pedal shaft will be locked, so that the foot pedal shaft can drive the outer sleeve and the chain wheel to rotate in the positive direction together, and thus can drive the wheel to rotate in the positive direction; when the user drives the foot pedal shaft to rotate in the reverse direction by stepping on the foot pedal, the clutch between the outer sleeve and the foot pedal shaft will be unlocked, so that the outer sleeve will not rotate in the reverse direction along with the foot pedal shaft.

[0030] In summary, the present application includes the following beneficial technical effects:

[0031] It includes a housing, a transmission shaft, an output shaft, a motor assembly, a cycloidal pinwheel reduction assembly, a driving bevel gear and a driven bevel gear. The transmission shaft is arranged in the housing along the length direction of the frame, and the output shaft is arranged in the housing along the width direction of the frame; the motor assembly is drivingly connected to one end of the transmission shaft far from the output shaft and can drive the transmission shaft to rotate. One end of the transmission shaft close to the output shaft is drivingly connected to the power input end of the cycloidal pinwheel reduction assembly, and a driving bevel gear is drivingly connected to the power output end of the cycloidal pinwheel reduction assembly; the driven bevel gear is arranged on the shaft body of the output shaft and meshes with the driving bevel gear. One end of the output shaft extends out of the housing through a relief hole provided on the housing and is provided with a sprocket, and the sprocket can be drivingly connected to the wheel of the electric bicycle through a chain; the cooperation of the driving bevel gear and the driven bevel gear enables the cycloidal pinwheel reduction assemblies and the motor assembly on both sides of the transmission shaft to be arranged along the length direction of the frame, so that the overall size of the mid-mounted motor for the electric bicycle in the width direction of the frame is smaller, so that the electric bicycle using this mid-mounted motor does not need to be designed with a wide frame, so that the electric bicycle using this mid-mounted motor is both beautiful and light. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a perspective view of a mid-mounted motor for an electric bicycle according to the present application;

[0033] Figure 2 is a schematic cross-sectional view taken along the central axis of the transmission shaft in a mid-mounted motor for an electric bicycle according to the present application.

[0034] Reference numerals: 1, housing; 2, transmission shaft; 3, output shaft; 31, sprocket; 32, pedal shaft; 33, outer sleeve; 4, motor assembly; 41, rotor; 42, stator; 43, control board; 431, jack; 432, magnetic part; 5, cycloidal pinwheel reduction assembly; 51, eccentric bushing; 52, outer gear; 53, inner gear; 54, output sleeve; 55, connecting shaft; 56, eccentric counterweight block; 6, driving bevel gear; 7, driven bevel gear; 8, one-way bearing; 9, clutch. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Figure 1 is a perspective view of a mid-mounted motor for an electric bicycle according to the present application, Figure 2 is a schematic cross-sectional view taken along the central axis of the transmission shaft in a mid-mounted motor for an electric bicycle according to the present application. See Figure 1 and Figure 2, a mid-mounted motor for an electric bicycle provided by the present application includes: a housing 1, a drive shaft 2, an output shaft 3, a motor assembly 4, a cycloid pinwheel reduction assembly 5, a driving bevel gear 6 and a driven bevel gear 7. The drive shaft 2 is arranged in the housing 1 along the length direction of the frame, and the output shaft 3 is arranged in the housing 1 along the width direction of the frame; the motor assembly 4 is drivingly connected to one end of the drive shaft 2 far from the output shaft 3 and can drive the drive shaft 2 to rotate. One end of the drive shaft 2 close to the output shaft 3 is drivingly connected to the power input end of the cycloid pinwheel reduction assembly 5, and a driving bevel gear 6 is drivingly connected to the power output end of the cycloid pinwheel reduction assembly 5; the driven bevel gear 7 is arranged on the shaft body of the output shaft 3 and meshes with the driving bevel gear 6. One end of the output shaft 3 extends out of the housing 1 through a relief hole opened on the housing 1 and is provided with a sprocket 31, and the sprocket 31 can be drivingly connected to the wheel of the electric bicycle through a chain.

[0036] Through the above settings, the cooperation of the driving bevel gear 6 and the driven bevel gear 7 not only realizes the driving connection between the cycloid pinwheel reduction assembly 5 and the output shaft 3, but also enables the drive shaft 2 to be arranged along the length direction of the frame. Subsequently, the cycloid pinwheel reduction assembly 5 and the motor assembly 4 on both sides of the drive shaft 2 do not need to be arranged along the width direction of the frame. Coupled with the relatively small overall volume of the cycloid pinwheel reduction assembly 5, the overall size of the mid-mounted motor for the electric bicycle in the width direction of the frame is relatively small, so that the electric bicycle using this mid-mounted motor does not need to be designed with a wide frame, making the electric bicycle using this mid-mounted motor both beautiful and lightweight.

[0037] See Figure 1 and Figure 2 , the motor assembly 4 includes a rotor 41, a stator 42 and a control board 43. The rotor 41 is connected to the drive shaft 2, and a permanent magnet is arranged outside the rotor 41. The stator 42 is sleeved on the rotor 41 and fixedly connected to the inner wall of the housing 1, and a coil adapted to the permanent magnet is arranged on the stator 42, so that the stator 42 can drive the rotor 41 to rotate through the coil, thereby driving the drive shaft 2 to rotate through the rotor 41, and then transmitting power to the cycloid pinwheel reduction assembly 5 through the drive shaft 2; an installation hole is opened at one end of the housing 1 close to the motor assembly 4, the control board 43 is arranged in the installation hole and electrically connected to the stator 42, and a jack 431 for electrically connecting to the electric bicycle is arranged on the side of the control board 43 facing away from the motor assembly 4, so that the wire of the controller on the electric bicycle can be electrically connected to the control board 43 through the jack 431, thereby enabling the controller to control the mid-mounted motor for the electric bicycle.

[0038] See Figure 1 and Figure 2, a magnetic member 432 is provided at one end of the transmission shaft 2 close to the control board 43. A Hall sensor (not shown in the figure) adapted to the magnetic member 432 is provided on the control board 43. The Hall sensor can judge the position and speed of the rotor 41 by sensing the magnetic poles on the magnetic member 432, so that the detection end of the Hall sensor does not need to extend between the stator 42 and the rotor 41, thus facilitating the installation of the Hall plate sensor.

[0039] See Figure 1 and Figure 2 , the cycloid pinwheel reduction assembly 5 includes an eccentric bushing 51, an external gear 52, an internal gear 53, an output sleeve 54, a connecting shaft 55 and an eccentric counterweight 56. The eccentric bushing 51 is press-fitted on the transmission shaft 2. The external gear 52 is sleeved on the eccentric bushing 51, and a bearing is provided between the external gear 52 and the eccentric bushing 51; the internal gear is sleeved on the external gear 52 and fixedly connected to the inner wall of the machine housing 1, and the internal teeth of the internal gear 53 mesh with the external teeth of the external gear 52. The output sleeve 54 is rotatably sleeved on the transmission shaft 2 through a bearing. The output sleeve 54 includes a large-diameter end and a small-diameter end. The driving bevel gear 6 is sleeved on the small-diameter end. A connecting hole is opened on the end face of the large-diameter end. One end of the connecting shaft 55 is inserted into the connecting hole and there is an interference fit between the shaft body of the connecting shaft 55 and the connecting hole. A transmission hole is opened on the external gear 52. One end of the connecting shaft 55 away from the output sleeve 54 is inserted into the transmission hole and can slide along the inner wall of the transmission hole; the eccentric counterweight 56 is press-fitted on the transmission shaft 2. Regarding the eccentric bushing 51 and the external gear 52 and the bearing sleeved on the eccentric bushing 51 as an eccentric whole, the eccentric distance of this eccentric whole is equal to that of the eccentric counterweight 56 and the phase difference is 180°, so that no eccentric force is generated when the eccentric bushing 51 rotates.

[0040] With the above settings, when the transmission shaft 2 rotates, the transmission shaft 2 will drive the eccentric bushing 51 to rotate together, so that the eccentric bushing 51 can drive the external gear 52 to revolve around the transmission shaft 2. When the external gear 52 revolves clockwise or counterclockwise, the internal teeth of the internal gear 53 will mesh with the external teeth of the external gear 52 and drive the external gear 52 to rotate around its own rotation axis. The rotation direction of this self-rotation movement is opposite to the rotation direction of the revolution movement, so that the eccentric bushing 51 drives the external gear 52 to perform a planetary motion around the transmission shaft 2, and drives the output sleeve 54 and the driving bevel gear 6 to rotate through the cooperation of the transmission hole and the connecting shaft 55. Then, the power is transmitted to the driven bevel gear 7 through the driving bevel gear 6, and finally the output shaft 3 and the sprocket 31 are driven to rotate through the driven bevel gear 7.

[0041] See Figure 1 and Figure 2A one-way bearing 8 is provided between the driving bevel gear 6 and the output sleeve 54. With the forward direction of the wheel of the electric bicycle as the positive direction, when the output sleeve 54 rotates in the positive direction, the outer ring and the inner ring of the first one-way bearing 8 will be stuck and rotate in the positive direction together, so that the output sleeve 54 can drive the driving bevel gear 6 to rotate in the positive direction together, thereby driving the sprocket wheel 31 and the wheel to rotate in the positive direction together.

[0042] See also Figure 1 and Figure 2 The output shaft 3 includes a pedal shaft 32 and a sleeve 33. Both ends of the pedal shaft 32 extend from the clearance holes provided on the casing 1 to the outside of the casing 1 and can be connected to the pedals of the electric bicycle; the sleeve 33 is sleeved on the pedal shaft 32, one end of the sleeve 33 is connected to the sprocket 31, and the other end of the sleeve 33 is connected to the driven bevel gear 7, and a clutch 9 is provided between the sleeve 33 and the pedal shaft 32. The clutch 9 can be a wedge-type clutch 9, so that the user can drive the pedal shaft 32 to rotate forward by pedaling. At this time, the clutch 9 between the sleeve 33 and the pedal shaft 32 will be stuck, so that the pedal shaft 32 can drive the sleeve 33 and the sprocket 31 to rotate forward together, thereby driving the wheel to rotate forward; and when the user drives the pedal shaft 32 to rotate in the opposite direction by pedaling, the clutch 9 between the sleeve 33 and the pedal shaft 32 will be unlocked, so that the sleeve 33 will not rotate in the opposite direction with the pedal shaft 32.

[0043] The working principle of a mid-mounted motor for an electric bicycle in the present application when in use is as follows:

[0044] The invention comprises a casing 1, a transmission shaft 2, an output shaft 3, a motor assembly 4, a cycloid pinwheel reduction assembly 5, a driving bevel gear 6 and a driven bevel gear 7. The transmission shaft 2 is arranged in the casing 1 along the length direction of the frame, and the output shaft 3 is arranged in the casing 1 along the width direction of the frame; the motor assembly 4 is transmission-connected with an end of the transmission shaft 2 away from the output shaft 3 and can drive the transmission shaft 2 to rotate, and an end of the transmission shaft 2 close to the output shaft 3 is transmission-connected with the power input end of the cycloid pinwheel reduction assembly 5, and the power output end of the cycloid pinwheel reduction assembly 5 is transmission-connected with the driving bevel gear 6; the driven bevel gear 7 is arranged on the shaft body of the output shaft 3 and is connected to the driving bevel gear 6. The moving bevel gear 6 is meshed, and one end of the output shaft 3 extends out of the casing 1 from the clearance hole opened on the casing 1 and is provided with a sprocket wheel 31, which can be connected to the wheel of the electric bicycle through a chain; the cooperation of the driving bevel gear 6 and the driven bevel gear 7 allows the cycloid pinwheel reduction assembly 5 and the motor assembly 4 on both sides of the transmission shaft 2 to be arranged along the length direction of the frame, so that the overall size of the mid-mounted motor for the electric bicycle in the width direction of the frame is smaller, so that the electric bicycle using this mid-mounted motor does not need to be designed with a wide frame, so that the electric bicycle using this mid-mounted motor is both beautiful and light.

[0045] It should be noted that the above are all preferred embodiments of the present application, and do not limit the protection scope of the present application. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A mid-mounted motor for an electric bicycle, used to be installed on the frame of the electric bicycle, characterized in that: The vehicle comprises a housing (1), a transmission shaft (2), an output shaft (3), a motor assembly (4), a cycloidal pinwheel reduction assembly (5), a driving bevel gear (6) and a driven bevel gear (7), wherein the transmission shaft (2) is arranged in the housing (1) along the length direction of the vehicle frame, and the output shaft (3) is arranged in the housing (1) along the width direction of the vehicle frame; The motor assembly (4) is in driving connection with an end of the transmission shaft (2) away from the output shaft (3) and is capable of driving the transmission shaft (2) to rotate; an end of the transmission shaft (2) close to the output shaft (3) is in driving connection with a power input end of the cycloid pinwheel reduction assembly (5); and the power output end of the cycloid pinwheel reduction assembly (5) is in driving connection with the driving bevel gear (6); The driven bevel gear (7) is arranged on the shaft body of the output shaft (3) and meshes with the driving bevel gear (6); one end of the output shaft (3) extends out of the housing (1) from a clearance hole provided on the housing (1) and is provided with a chain wheel (31); the chain wheel (31) can be connected to the wheel of the electric bicycle through a chain.

2. The mid-mounted motor for an electric bicycle according to claim 1, characterized in that: The motor assembly (4) comprises a rotor (41) and a stator (42); the rotor (41) is connected to the transmission shaft (2), and a magnetic steel is provided on the outer side of the rotor (41); The stator (42) is sleeved on the rotor (41) and fixedly connected to the inner wall of the casing (1), and a coil matched with the magnetic steel is provided on the stator (42).

3. The mid-mounted motor for an electric bicycle according to claim 2, characterized in that: The motor assembly (4) further comprises a control board (43); a mounting hole is provided on the housing (1) at one end close to the motor assembly (4); the control board (43) is arranged in the mounting hole and is electrically connected to the stator (42).

4. The mid-mounted motor for an electric bicycle according to claim 3, characterized in that: A socket (431) for electrical connection with an electric bicycle is provided on a side of the control panel (43) facing away from the motor assembly (4).

5. The mid-mounted motor for an electric bicycle according to claim 3, characterized in that: A magnetic component (432) is provided at one end of the transmission shaft (2) close to the control board (43), and a Hall sensor matched with the magnetic component (432) is provided on the control board (43).

6. The mid-mounted motor for an electric bicycle according to claim 1, characterized in that: The cycloid pinwheel reduction assembly (5) comprises an eccentric shaft sleeve (51), an external gear (52), an internal gear (53) and an output sleeve (54); the eccentric shaft sleeve (51) is sleeved on the transmission shaft (2); the external gear (52) is sleeved on the eccentric shaft sleeve (51); and a bearing is provided between the external gear (52) and the eccentric shaft sleeve (51); The internal gear (53) is sleeved on the external gear (52) and fixedly connected to the inner wall of the housing (1), and the internal teeth of the internal gear (53) mesh with the external teeth of the external gear (52); The output sleeve (54) is rotatably sleeved on the transmission shaft (2); a side of the output sleeve (54) away from the motor assembly (4) is connected to the driving bevel gear (6); a connecting shaft (55) is provided on a side of the output sleeve (54) close to the motor assembly (4); a transmission hole is provided on the external gear (52); an end of the connecting shaft (55) away from the output sleeve (54) is inserted into the transmission hole and can slide along the inner wall of the transmission hole; When the transmission shaft (2) rotates, the eccentric shaft sleeve (51) can drive the external gear (52) to perform planetary rotation around the transmission shaft (2) through rotation, so that the external gear (52) drives the output sleeve (54) and the driving bevel gear (6) to rotate around the transmission shaft (2) via the connecting shaft (55).

7. The mid-mounted motor for an electric bicycle according to claim 6, characterized in that: The output sleeve (54) comprises a large diameter end and a small diameter end, the transmission shaft (2) is connected to the end of the large diameter end, the driving bevel gear (6) is sleeved on the small diameter end, and a one-way bearing (8) is provided between the driving bevel gear (6) and the output sleeve (54).

8. The mid-mounted motor for an electric bicycle according to claim 7, characterized in that: The output shaft (3) comprises a pedal shaft (32) and a sleeve (33); both ends of the pedal shaft (32) extend out of the housing (1) from a clearance hole provided on the housing (1) and are both capable of being connected to the pedals of the electric bicycle; The outer sleeve (33) is sleeved on the pedal shaft (32), one end of the outer sleeve (33) is connected to the chain wheel (31), the other end of the outer sleeve (33) is connected to the driven bevel gear (7), and a clutch (9) is provided between the outer sleeve (33) and the pedal shaft (32).

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