CN114132422A

CN114132422A - Stable high-power plug-in type middle-placed motor

Info

Publication number: CN114132422A
Application number: CN202111643344.0A
Authority: CN
Inventors: 沈国栋
Original assignee: Suzhou Tongsheng Electric Appliance Co ltd
Current assignee: Suzhou Tongsheng Electric Appliance Co ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-03-04

Abstract

The invention provides a stable high-power plug-in mid-mounted motor, which includes a main casing, the main casing includes a shaft sleeve inserted into the bicycle bottom bracket assembly, and an assembly shell fixed on the upper part of the shaft sleeve, the assembly shell An electric module is assembled on the left side of the assembly shell; a through hole is processed in the middle of the assembly shell, the output shaft of the electric module extends from the left side of the assembly shell to the right side, and the right side of the assembly shell is fixedly assembled with a fixing frame, Two or more planetary shafts that are evenly distributed in the circumferential direction relative to the output shaft are assembled between the assembling shell and the fixing frame, the planetary shafts are assembled with planetary gears, and the outside of the planetary gears is equipped with a sun gear for meshing transmission, and the transmission on the sun gear A transition module is connected, and the transition module is drivingly connected with the crankset. The inner part of the motor adopts a planetary transmission structure, which makes the transmission more stable and can greatly improve the output power of the motor under the same volume.

Description

Stable high-power plug-in type middle-placed motor

Technical Field

The invention belongs to the technical field of motors, and particularly relates to a stable high-power plug-in type middle motor.

Background

The electric bicycle is generally divided into a hub motor and a middle motor, the middle motor can be divided into a plug-in middle motor and an integrated middle motor, and the plug-in middle motor generally adopts a secondary transmission structure to connect an output shaft and a chain wheel of the motor and simultaneously realizes a speed reduction function. Such as an electric bicycle dual-purpose actuating device disclosed in the patent with publication number CN2541317Y, and an electric auxiliary transmission of a bicycle disclosed in the patent with publication number CN 2561697Y; such a structure is used. The motor structure can be directly inserted into a bicycle five-way, so that people can greatly improve and install common bicycles directly, the traditional bicycle has auxiliary power, and people can ride the bicycle conveniently.

However, in the transmission structure, a structure of direct engagement of a single gear set is usually adopted for speed reduction transmission, in the structure, the transmission speed ratio is low, single gear engagement is adopted in the transmission, all transmission forces are directly transmitted between two independent gears, the stress is unbalanced, and vibration is easily generated. The whole motor transmission stability is influenced, the stress of the gear is larger due to the transmission of the other two independent gears, particularly the rotating speed of the gear in transmission connection is larger when the power is directly output, so that the friction of the gear directly meshed with the electric module is severe, the gear is easy to wear, particularly, the gear with a smaller module and a smaller number of teeth is worn particularly severely, and the speed reduction ratio of the traditional plug-in type middle-placed motor structure is lower in the design of the same volume gear module. Therefore, in the traditional plug-in type middle-placed motor, the power of the motor is generally designed to be lower, the service life of the motor is shorter, and especially when the traditional motor is used in a severe impact state, not only enough auxiliary power cannot be obtained, but also the damage condition of the motor is greatly aggravated. In order to minimize the influence on the portability of the bicycle, the plug-in motor needs to be compact and as small as possible.

In conclusion, due to various factors, the power of the traditional plug-in type middle-mounted motor is low, the vibration is large, and the service life is short. The helping hand condition of the electric motor car helping hand bicycle of putting the motor in the use has greatly been restricted for when people used this motor as auxiliary power, the experience effect of riding was relatively poor, for example adopt the electric power bicycle of putting the motor in traditional bayonet, the motor normal power that uses this traditional structure is lower, the helping hand of can't riding fast, also can't provide sufficient helping hand under ramp or mountain road conditions.

In addition, when the traditional plug-in type middle-arranged motor is used for transmission between a motor output shaft and a middle-arranged bicycle axle, a transition transmission gear generally adopts a cantilever structure, so that the whole transmission process is not stable enough, and the service life of the motor can be influenced.

Disclosure of Invention

Aiming at the problems, the invention provides the stable high-power plug-in type middle motor which is compact in structure, adopts a planetary transmission structure in the motor, can greatly improve the output power of the motor under the same volume and can provide stronger power for a modified bicycle.

The technical scheme adopted by the invention for solving the technical problems is as follows: the stable high-power plug-in type middle-placed motor comprises a main shell, wherein the main shell comprises a shaft sleeve and an assembly shell, the shaft sleeve is inserted into a five-way assembly of a bicycle, the assembly shell is fixed to the upper portion of the shaft sleeve, a middle shaft is assembled inside the shaft sleeve, a pedal rod is assembled on the middle shaft, and an electric module is assembled on the left side of the assembly shell; the assembly shell is provided with a through hole in the middle, the output shaft of the electric module extends out of the left side of the assembly shell to the right side, the right side of the assembly shell is fixedly provided with a fixing frame, more than two planetary shafts which are circumferentially and uniformly distributed relative to the output shaft are arranged between the assembly shell and the fixing frame, each planetary shaft is respectively provided with a planetary wheel which is meshed with the gear on the output shaft, the external part of the planetary wheel is provided with a sun wheel which is meshed with the gear, the sun wheel is in transmission connection with a transition module, and the transition module is in transmission connection with a chain wheel.

Preferably, the sun gear is provided with two outer gears and two inner gears which are coaxial and have different diameters, the inner gear on the sun gear is meshed with the outer gear of the planet gear, the diameter of the inner gear on the sun gear is larger than that of the outer gear, and the outer gear on the sun gear is meshed with the transition module for transmission.

Preferably, two external gears with the same shaft and different diameters are machined on the planet wheel, the external gear with the large diameter on the planet wheel is meshed with the gear on the output shaft, and the external gear with the small diameter on the planet wheel is meshed with the internal gear of the sun gear.

Preferably, three planet shafts which are uniformly distributed around the axial direction are designed between the assembling shell and the fixed frame.

Preferably, the transition module comprises a transition gear shaft, an integrated external gear is machined on the transition gear shaft, the transition gear shaft is assembled on the assembly shell through a rotating piece, and an external gear in meshing transmission with the sun gear is fixedly assembled on the transition gear shaft.

Preferably, the transition module is in transmission connection with the chain wheel through a resultant force bearing, the resultant force bearing comprises an annular inner sleeve, an outer sleeve and a middle sleeve which are coaxially assembled, rolling bodies are respectively assembled between the inner sleeve and the outer sleeve and between the inner sleeve and the middle sleeve, and an assembly structure is respectively designed on the inner wall of the inner sleeve, the outer wall of the outer sleeve and the end part of the middle sleeve; the clutch member is assembled between the inner sleeve or the outer sleeve and the middle sleeve, the clutch member and the annular sleeve assembled with the clutch member form a one-way transmission structure, the chain wheel is assembled on the middle sleeve, and the inner sleeve is fixedly assembled with the middle shaft.

Preferably, an external gear is integrally formed on an outer sleeve of the resultant force bearing, and the external gear on the outer sleeve is in transmission connection with the transition module.

Preferably, the right side of the assembly shell is fixedly assembled with a right shell, the left side of the right shell is fixedly assembled with the fixed frame, the right side of the transition gear shaft is assembled and connected with the right shell through a rotating part, and the right shell is fixed with the main shell through a pin.

Preferably, the main housing and the right housing are internally equipped with magnetic encoders.

Preferably, the right side of the main shell is provided with a left shell wrapping the electric module, and the lower part inside the left shell is provided with a glue-sealed controller.

Preferably, the transition module is in transmission connection with a toothed disc through an auxiliary gear, the auxiliary gear is integrally machined, the auxiliary gear is coaxially assembled on the middle shaft, the toothed disc is fixed on the right side of the auxiliary gear, the auxiliary gear is designed to be of a stepped structure, a shaft shoulder structure is machined outside the auxiliary gear, and the inner wall of the auxiliary gear and the outer shaft shoulder are assembled through rotating parts respectively.

The invention has the beneficial effects that: the stable high-power plug-in central motor is mainly used at the central shaft position of a bicycle and can be used for directly replacing the central shaft part of the original bicycle, the motor drives a chain wheel to move through an electric module to provide auxiliary power for people riding, the motor is assembled with a planetary transmission structure through the matching of an assembly shell of a main shell body and a fixing frame, and the power is further transmitted downwards by utilizing a sun wheel in the planetary transmission structure, so that the whole transmission structure is compactly assembled in the shell body, in the traditional plug-in central motor, the transmission part corresponding to the planetary transmission structure directly supports the output transmission of the electric module, and is a main abrasion part and a force bearing part in the whole electric module, because of the application of the planetary structure, a plurality of planetary wheels are used for simultaneous transmission, each planetary wheel can effectively share the power output by the electric module, and simultaneously because the stress is uniformly output to the annular sun wheel through the circumferential planetary wheels, more stability during making the transmission, vibrations are littleer, the power of sun gear output is also bigger, and planetary transmission structure in addition for electric module can have higher transmission velocity ratio to the final auxiliary output part of chain wheel, makes the whole higher power that can be suitable for of motor, and the motor can provide higher power output when using like this, and the material of planet wheel selects more extensively simultaneously, and wearing and tearing are lower simultaneously.

Planetary drive structure is in with the assembly of electronic module in this motor the both sides of assembly shell on the main casing body, overall layout is more reasonable, can effectively reduce the vibrations of motor, reduce transmission part's wearing and tearing, improve the motor life-span, make the passerby's of riding that uses this motor more comfortable, the more powerful design of motor simultaneously, can provide higher power take off when needing, make people can be suitable for more in service behavior when riding the bicycle, for example, can climb the slope of higher slope, can provide higher automatic speed of traveling when needing.

Drawings

Fig. 1 is a schematic sectional structure diagram of a stable high-power plug-in mid-motor in embodiment 1.

Fig. 2 is a perspective view of the internal transmission structure of the stable high-power plug-in mid-motor in embodiment 1.

Fig. 3 is a schematic structural view in the cross-sectional direction of the sun gear.

Fig. 4 is a schematic structural view in the cross section direction of the planet wheel.

Fig. 5 is a schematic sectional structure diagram of a stable high-power plug-in mid-motor in embodiment 2.

Detailed Description

The invention is further illustrated by the following examples:

as used in this patent, directional terms, such as orientation or positional relationship, are used with respect to the drawings only for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the present application.

In example 1

As shown in embodiment 1 in fig. 1 and 2, the stable high-power plug-in mid-motor comprises a main housing 1, wherein the main housing 1 comprises a shaft sleeve 11 inserted into a five-way assembly of a bicycle and an assembly housing 12 fixed on the upper part of the shaft sleeve 11, a middle shaft 2 is assembled in the shaft sleeve 11, a pedal rod 3 is assembled on the middle shaft 2, and the pedal rod 3 is used for providing pedal force for people through pedals. The left side of the assembly housing 12 is assembled with the electric module 4; in the present embodiment, the structure of the shaft sleeve 11 is similar to the conventional structure and will not be described in detail again, and the electric module 4 also adopts a common electromagnetic power structure, specifically, an inner rotor transmission structure is adopted in the present embodiment to output power.

In this patent, a through hole is formed in the middle of the assembly housing 12, the output shaft 41 of the electric module 4 extends from the left side of the assembly housing 12 to the right side through the through hole, the right side of the assembly housing 12 is fixedly provided with a fixed frame 5, three planetary shafts 51 are arranged between the assembly housing 12 and the fixed frame 5 and are circumferentially and uniformly distributed relative to the output shaft 41, each planetary shaft 51 is provided with a planetary gear 52 meshed with a fixed gear on the output shaft 41, in this embodiment, the output shaft 41 and a gear thereon are integrally formed, that is, the output shaft 41 and the gear thereon form a gear shaft. The planet wheel 52 is externally provided with a sun wheel 53 in meshing transmission, the sun wheel 53 is in transmission connection with a transition module 6, and the transition module 6 is in transmission connection with the chain wheel 3.

This stable form is high-power to put motor in bayonet mainly uses the axis position at the bicycle, can be used for the axis part of direct replacement original bicycle, and this motor drives chain wheel 3 through electric module and moves and provide auxiliary power for the people in riding, and this motor assembles planetary drive structure through the cooperation of the assembly shell 12 of main casing body 1 and mount 5 to sun gear 53 further drives power down in utilizing planetary drive structure, makes the assembly of whole transmission compact structure in the casing like this. In the traditional plug-in type middle-placed motor, the transmission part corresponding to the planetary transmission structure directly supports the output transmission of the electric module 4, which is the main wear and bearing part in the whole electric module, in the embodiment, due to the application of the planetary structure, three planet wheels 52 are used for simultaneous transmission, so that each planet wheel 52 can effectively share the power output by the electric module 4, and simultaneously, due to the fact that the stress is uniformly output to the annular sun wheel 53 through the circumference of the planet wheel 52, the transmission is more stable, the vibration is smaller, the power output by the sun wheel 53 is also larger, in addition, the planetary transmission structure is used, so that the final auxiliary output part from the electric module 4 to the dental disc 3 can have a higher transmission speed ratio, the motor can be suitable for higher power integrally, and under the condition that the motor is small and exquisite, the motor structure can greatly output the power, meanwhile, due to the fact that the plurality of planet wheels 52 are used for force transmission, the material selection is wider, and meanwhile, the abrasion is lower.

Planetary drive structure is in with electronic module 4 assembly in this motor the both sides of assembly shell 12 on the main casing body, overall layout is more reasonable, can effectively reduce the vibrations of motor, reduce the wearing and tearing of transmission part, the motor life-span is prolonged, make the more comfortable of passerby of riding that uses this motor, the more powerful design of motor simultaneously, can provide higher power take off when needing, make people can be suitable for more in service behavior when riding the bicycle, for example, can climb the slope of higher slope, can provide higher automatic speed of traveling when needing. And the design of the planetary transmission structure can ensure that the motor has larger transmission ratio in the same space, further improves the design performance of the motor, and greatly improves the service performance of the motor.

In practical implementation, as shown in fig. 1, 2 and 3, the sun gear 53 is designed with two external gears and an internal gear which are coaxial and have different diameters, the internal gear on the sun gear 53 is meshed with the external gear on the planet gears 52, the internal gear on the sun gear 53 has a larger diameter than the external gear, and the external gear 53 on the sun gear 53 is meshed with the transition module 6 for transmission. The design of the large inner gear on the sun gear 53 ensures that the two gears on the sun gear 53 are not on the same plane perpendicular to the axis and are stepped gears, the improved structure has better combination with the original middle motor structure by the design of the stepped structure, and meanwhile, the speed reduction transmission is realized.

As shown in fig. 1, 2 and 4, the planetary gear 52 is formed with two external gears of different diameters coaxially, the external gear of large diameter on the planetary gear 52 meshes with the gear on the output shaft 41, and the external gear of small diameter on the planetary gear 52 meshes with the internal gear of the sun gear 53. Because sun gear 53 wraps up outside planet wheel 52, the size of sun gear can effectively be reduced in this kind of stair structure's design, simultaneously, the stair structure design of big or small external tooth on planet wheel 52 can further reduce the speed to the motor, can effectively improve the reduction ratio of motor, combines the use of a plurality of planet wheels 52 of this planetary transmission like this for in finite space, under the condition of realizing big reduction ratio, guaranteed that the transmission of motor overall structure is stable.

As shown in fig. 1, the transition module 6 includes a transition gear shaft 61, an integral external gear is machined on the transition gear shaft 61, the transition gear shaft 62 is assembled on the assembly housing 12 through a rotating member, and the external gear 62 in meshing transmission with the sun gear 53 is fixedly assembled on the transition gear shaft 61.

As shown in fig. 1 and 2, the transition module 6 is in transmission connection with the chain wheel 7 through a resultant force bearing 8, the resultant force bearing 8 includes an annular inner sleeve 81, an outer sleeve 82 and a middle sleeve 83 which are coaxially assembled, rolling bodies 84 are respectively assembled between the inner sleeve 81 and the outer sleeve 82 and between the middle sleeve 83, and an assembly structure is respectively designed on an inner wall of the inner sleeve 81, an outer wall of the outer sleeve 82 and an end of the middle sleeve 83; a clutch piece is assembled between the inner sleeve or the outer sleeve and the middle sleeve 83, the clutch piece and an annular sleeve assembled with the clutch piece form a one-way transmission structure, the chain wheel 7 is assembled on the middle sleeve 83, and the inner sleeve 81 is fixedly assembled with the middle shaft. In the present embodiment, an external gear is integrally formed on the outer casing 82 of the resultant bearing 8, and the external gear on the outer casing 82 is in meshing transmission with the external gear 62 on the transition module 6. When the motor is used for assisting power on a bicycle, the power on the electric module 4 is transmitted to the outer sleeve 82 of the resultant force bearing 8 through the planetary transmission structure and the transition module 6, then the outer sleeve transmits the power to the chain wheel 7 in a one-way mode, so that the electric drive of the modified assisted bicycle is realized, when the modified assisted bicycle is subjected to pedal drive by oneself, the pedal force is transmitted to the inner sleeve 81 through the middle shaft 2, and the inner sleeve 81 transmits the pedal force to the chain wheel of the middle sleeve 83 in a one-way mode. Therefore, resultant force output of electric power and pedal power is realized, and the pedal power and the power are driven in a unidirectional mode when the pedal power and the power transmit power to the chain wheel 7 in the resultant force bearing 8, so that the motor, the pedal power and the electric power cannot be directly influenced mutually, when the electric module 4 moves fast, the connecting middle shaft 2 and the pedal inner sleeve 81 directly separate from movement, full electric drive is realized, and when the pedal driving speed is higher than that of the electric module 4, the transition module 6, the outer sleeve 82 and the chain wheel connected with the middle sleeve 83 separate from movement, and independent pedal drive is realized. The resultant force bearing is used, so that the whole transmission structure is greatly simplified, a clutch structure is not required to be additionally designed, the number of parts is greatly reduced, and the assembly is more convenient.

As shown in fig. 1, a right housing 13 is fixedly assembled on the right side of the assembly housing, the left side of the right housing is fixedly assembled with the fixed frame 5, the right side of the transition gear shaft 61 is assembled and connected with the right housing 13 through a rotating member, and the right housing 13 is fixed with the main housing 1 through a pin. Right side shell 13 with main casing body 1 uses the round pin to connect the back, and is fixed as an organic whole, like this transition gear shaft 61 all assembles through the rotating member in both sides respectively, compares with traditional cantilever structure, and transition gear shaft 61 moves stability more in this motor, and life is longer, and transmission effect is better.

As shown in fig. 1, the main housing 1 and the right housing 13 are internally equipped with a magnetic encoder 9. Specifically, the magnetic encoder 9 is a rotary magnetic encoder, and can be used to determine the change in the output magnetic force of the electromotive module 4, thereby determining the overall operating condition of the motor.

As shown in fig. 1, a left casing 14 for wrapping the electric module 4 is assembled on the right side of the main casing 1, and the controller 10 is assembled inside the left casing 14 at a lower position. Particularly, the lower part of the left shell 14, which is provided with the electric module 4, is provided with a special assembly cavity, the controller 10 is assembled inside, and thus the circuit structure is integrally assembled inside the shell, so that the appearance is more attractive, and meanwhile, the circuit board part of the controller 10 is designed by adopting a glue seal, so that the circuit structure can be better waterproof, and even if the motor is rain-drenched in the use process due to the integral stability of the circuit board in the use process, the motor cannot generate short circuit to cause danger.

Example 2

As shown in fig. 5, most of the structure of embodiment 2 is the same as that of embodiment 1, in embodiment 2, the transition module 6 is in transmission connection with the chain wheel 7 through an auxiliary gear 8a, specifically, the two are directly fixedly connected by using bolts, the auxiliary gear 8a is designed into a stepped structure, a shoulder structure is machined outside the auxiliary gear 8a, and the inner wall and the outer shoulder of the auxiliary gear 8a are respectively assembled through rotating members. The auxiliary gear 8a is assembled and designed in such a way that the transmission of the auxiliary gear 8a is more stable, in the embodiment, the auxiliary gear is integrally machined, the auxiliary gear 8a is coaxially assembled on the middle shaft, and the chain wheel is directly fixed on the right side of the auxiliary gear 8 a. In this way, the auxiliary gear 8a is directly connected with the chain wheel 7, and the chain wheel 7 is more stable when moving along with the auxiliary gear 8a through the additional double-rotation limit assembly of the auxiliary gear 8 a.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A stable high-power plug-in central motor includes a main casing, the main casing includes a shaft sleeve inserted into the bicycle bottom bracket assembly, and an assembly shell fixed on the upper part of the shaft sleeve, and the inside of the shaft sleeve is equipped with a The center shaft is equipped with a pedal rod, and the left side of the assembly shell is equipped with an electric module; it is characterized in that a through hole is machined in the middle of the assembly shell, and the output shaft of the electric module is The left side of the assembly shell protrudes to the right side, the right side of the assembly shell is fixedly assembled with a fixed frame, and between the assembly shell and the fixed frame, two or more planetary shafts that are evenly distributed in the circumferential direction relative to the output shaft are assembled. The shafts are respectively equipped with planetary gears that mesh with the gears on the output shaft. The planetary gears are equipped with a meshing transmission sun gear on the outside, and a transition module is connected to the sun gear, and the transition module is connected to the crankset. .

2. The stable high-power plug-in mid-mounted motor according to claim 1, characterized in that: the sun gear is designed with two coaxial external gears and internal gears of different diameters, and the internal gear on the sun gear The gear meshes with the outer gear of the planetary gear, the diameter of the inner gear of the sun gear is larger than that of the outer gear, and the upper outer gear of the sun gear meshes with the transition module for transmission.

3 . The stable high-power plug-in mid-mounted motor according to claim 2 , wherein two coaxial external gears with different diameters are machined on the planetary wheel, and a large-diameter external gear on the planetary wheel is 3. 4 . It meshes with the gear on the output shaft, and the small-diameter external gear on the planetary gear meshes with the internal teeth of the sun gear.

4. The stable high-power plug-in mid-mounted motor according to any one of claims 1 to 3, wherein three planetary shafts evenly distributed around the axial direction are designed between the assembly shell and the fixing frame.

5 . The stable high-power plug-in mid-mounted motor according to claim 1 , wherein the transition module includes a transition gear shaft, and an integral external gear is machined on the transition gear shaft. 6 . , the transition gear shaft is assembled on the assembly shell through a rotating piece, and an external gear that meshes and drives with the sun gear is fixedly assembled on the transition gear shaft.

6. The stable high-power plug-in mid-mounted motor according to any one of claims 1-3, wherein the transition module is connected to the crankset through a resultant bearing, and the resultant bearing includes an annular The inner sleeve, outer sleeve and middle sleeve of the shaft assembly, rolling elements are respectively assembled between the inner sleeve and outer sleeve and the middle sleeve, and the inner wall of the inner sleeve, the outer wall of the outer sleeve, and the end of the middle sleeve are respectively designed to be assembled structure; a clutch member is assembled between the inner sleeve or the outer sleeve and the middle sleeve, the clutch member and the annular sleeve on which the clutch member is assembled form a one-way transmission structure, the crankset is assembled on the middle sleeve, and the inner sleeve is connected to the middle sleeve. Central axle fixed assembly.

7 . The stable high-power plug-in mid-mounted motor according to claim 6 , wherein an outer gear is integrally processed on the outer casing of the resultant bearing, and the outer gear on the outer casing is drive-connected with the transition module. 8 .

8. The stable high-power plug-in mid-mounted motor according to any one of claims 1-3, characterized in that: the right side of the assembly case is fixedly assembled with a right case, and the left side of the right case is connected to the The fixing frame is fixedly assembled, the right side of the transition gear shaft is assembled and connected to the right casing through a rotating piece, and the right casing and the main casing are fixed by pins.

9. The stable high-power plug-in mid-mounted motor according to any one of claims 1-3, wherein the main casing and the right casing are equipped with a magnetic encoder; the right side of the main casing is equipped with a magnetic encoder. The left shell of the electric module is wrapped, and the inner lower part of the left shell is equipped with a rubber-sealed controller.

10. The stable high-power plug-in mid-mounted motor according to any one of claims 1-3, characterized in that: the transition module is connected to the crankset through an auxiliary gear, the auxiliary gear is integrally processed, and the The auxiliary gear is coaxially assembled on the central axle, the crankset is fixed on the right side of the auxiliary gear, the auxiliary gear is designed as a stepped structure, and a shoulder structure is processed on the outside of the auxiliary gear. The inner wall and the outer shoulder are respectively assembled by rotating parts.