Low-speed large-torque efficient energy-saving compact wheel core electric driving system

Abstract

The utility model discloses a low-speed large-torque efficient energy-saving compact wheel core electric drive system, which comprises a box body, a motor, a speed reducing mechanism and a first support shaft, the speed reducing mechanism comprises a first auxiliary shaft and a second auxiliary shaft which are parallel to a motor shaft, and the first auxiliary shaft and the second auxiliary shaft are distributed around the motor shaft along the circumferential direction. Therefore, a third-stage gear transmission pair and a fourth-stage gear transmission pair are added, large-torque output of a small-power motor under the low-speed working condition is achieved through the four-stage speed reduction transmission design, the new national standard requirement of the electric bicycle can be particularly met, and under the new national standard condition of the electric bicycle, the electric bicycle can run at the running speed of 5 kilometers, and the electric bicycle can run stably. The vehicle can easily and stably run on a 30% slope, and the dynamic property and the energy-saving property are both good; moreover, the first auxiliary shaft and the second auxiliary shaft are distributed around the motor shaft in the circumferential direction, so that the overall radial size is not increased compared with an existing wheel core electric driving system, and the overall structure is extremely compact.

Description

Technical Field

[0001] The utility model relates to the technical field of electric drive devices, in particular to a low-speed, high-torque, high-efficiency, energy-saving and compact wheel core electric drive system. Background Art

[0002] An electric two-wheeled vehicle is a mechatronic personal transportation device based on a two-wheeled vehicle, powered by a battery. These vehicles are equipped with a motor, controller, and instrumentation system. They are not only a means of transportation but also a new type of leisure and entertainment device for green travel. They can also meet fitness, personal expression, and social needs, offering significant advantages in cost-effectiveness and convenience.

[0003] Please refer to the Chinese utility model patent with publication number CN218868049U and the Chinese utility model patent application numbers CN202420807200.7 and CN202421717699.9. The applicant in this case has designed a series of wheel core electric drive systems. By integrating the high-speed motor and reducer into the wheel hub, they have obvious advantages in structural compactness, torque transmission capability, and motor efficiency.

[0004] With the introduction and popularization of the new national standards for electric motorcycles and electric bicycles, the above-mentioned wheel core electric drive system is still well-suited for high-speed electric motorcycles, but is not well-suited for low-speed electric bicycles. This is mainly reflected in the new national standard requirements for electric bicycles: the maximum current does not exceed 25A, the rated voltage is 48V, the rated power is 400W, and the peak power does not exceed 1200W. However, the reducers of the above-mentioned wheel core electric drive systems designed by the applicants only have two-stage reduction. Under the conditions of meeting the new national standard for electric bicycles, the above-mentioned wheel core electric drive systems cannot stably travel on a 30% slope at a speed of 5 kilometers. Therefore, the applicants are in urgent need of optimizing and adjusting the structure of the existing wheel core electric drive system. Utility Model Content

[0005] In order to solve the technical problem that the existing wheel core electric drive system is not well adapted to the new national standard for electric bicycles, the utility model provides a low-speed, high-torque, high-efficiency, energy-saving and compact wheel core electric drive system.

[0006] The technical solution is as follows:

[0007] The first aspect of the present application relates to a low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system, comprising a housing, a motor and a reduction mechanism all arranged in the housing, and a first support shaft coaxially arranged with the motor shaft of the motor, the first support shaft is sleeved with a wheel hub drive sleeve that can rotate relative to it, the wheel hub drive sleeve and the first support shaft both partially pass through the housing, the reduction mechanism comprises a first secondary shaft arranged parallel to the motor shaft and a primary driving gear sleeved on the motor shaft in synchronous rotation, the first secondary shaft has a primary driven gear and a secondary driving gear that both rotate synchronously with it The first-stage driving gear is meshed with the first-stage driven gear, and the reduction mechanism further includes a double gear capable of rotating relative to the motor shaft and a second countershaft arranged parallel to the motor shaft. The first countershaft and the second countershaft are circumferentially distributed around the motor shaft. The second countershaft is provided with a third-stage driven gear and a fourth-stage driving gear that rotate synchronously therewith. The double gear has a second-stage driven tooth meshed with the second-stage driving gear and a third-stage driving tooth meshed with the third-stage driven gear. The wheel hub drive sleeve is synchronously rotated with a fourth-stage driven gear meshed with the fourth-stage driving gear.

[0008] The above low-speed, high-torque, high-efficiency, energy-saving and compact wheel core electric drive system is adopted. By adding a second countershaft, a third-stage gear transmission pair and a fourth-stage gear transmission pair are added. The four-stage reduction transmission design is utilized to achieve high torque output of a small-power motor under low-speed conditions, and in particular, it can meet the requirements of the new national standard for electric bicycles. Under the new national standard conditions for electric bicycles, it can travel easily and stably on a 30% slope at a speed of 5 kilometers, with excellent power and energy saving. Moreover, since the first countershaft and the second countershaft are distributed circumferentially around the motor shaft, the overall radial size does not increase compared to the existing wheel core electric drive system, and the overall structure is extremely compact.

[0009] In some embodiments, the outer end of the motor shaft is coaxially fitted with a semi-hollow shaft, the end of the semi-hollow shaft away from the motor shaft is rotatably mounted on the housing via a bearing, and the duplex gear is rotatably fitted outside the semi-hollow shaft via a needle bearing.

[0010] In some embodiments, the housing includes a motor housing and a reducer housing fixedly connected as one, the reducer housing being divided into a first mounting cavity and a second mounting cavity by an intermediate partition, the motor being mounted in the motor housing, the outer end of the motor shaft extending into the first mounting cavity, the intermediate partition having a partition bearing mounting seat protruding toward the first support shaft, the end of the semi-hollow shaft away from the motor shaft being rotatably mounted on the partition bearing mounting seat through a bearing, a first bearing mounting seat adapted for the first secondary shaft and a second bearing mounting seat adapted for the second secondary shaft being provided on a side wall of the first mounting cavity close to the motor housing, a third bearing mounting seat adapted for the second secondary shaft being provided on a side wall of the second mounting cavity away from the first mounting cavity, the two ends of the first secondary shaft being rotatably mounted on the first bearing mounting seat and the partition bearing mounting seat respectively through bearings, one end of the second secondary shaft being rotatably mounted on the second bearing mounting seat through a bearing, and the other end being rotatably mounted on the third bearing mounting seat through a bearing after passing through the intermediate partition.

[0011] In some embodiments, the inner end of the first support shaft is enlarged to form a support shaft mounting seat, and the support shaft mounting seat is fixedly connected to the middle partition by bolts. The support shaft mounting seat is recessed on one side close to the middle partition to form a first clearance groove that is compatible with the partition bearing mounting seat. The partition bearing mounting seat extends into the first clearance groove, and the support shaft mounting seat is provided with a support shaft bearing mounting seat on the side away from the middle partition. The inner end of the wheel hub drive sleeve is rotatably supported on the support shaft bearing mounting seat through a bearing, and the outer end of the wheel hub drive sleeve is rotatably supported on the first support shaft through a bearing.

[0012] In some embodiments, the fourth-stage driven gear has a second clearance groove on a side close to the middle partition plate, which is adapted to the support shaft bearing mounting seat, and the support shaft bearing mounting seat extends into the second clearance groove.

[0013] In some embodiments, the root of the fourth-stage driven gear has a gear mounting sleeve extending away from the middle partition, the inner circumferential surface of the gear mounting sleeve is spline-matched with the outer circumferential surface of the hub drive sleeve, and the outer circumferential surface of the gear mounting sleeve is rotatably supported on the inner end of the through-hole of the second mounting cavity through a bearing, and a first oil seal is also provided between the outer end of the through-hole and the outer circumferential surface of the gear mounting sleeve.

[0014] In some embodiments, a second support shaft is fixedly installed on the side of the motor housing away from the reducer housing. The second support shaft is coaxially arranged with the first support shaft, and the two flat fork arms of the flat fork are respectively locked on the first support shaft and the second support shaft through two corresponding locking nuts.

[0015] In some embodiments, a wheel hub is mounted on the wheel hub driving sleeve in a synchronously rotatable manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of the low-speed, high-torque, high-efficiency, energy-saving and compact wheel core electric drive system;

[0017] Figure 2 A cross-sectional view of a low-speed, high-torque, energy-efficient, compact wheel core electric drive system;

[0018] Figure 3 Schematic diagram of the coordination relationship among the motor, the reduction mechanism and the first support shaft;

[0019] Figure 4 It is a structural schematic diagram of a portion of the reducer housing with a middle partition;

[0020] Figure 5 is a structural schematic diagram of the first support shaft;

[0021] Figure 6 It is a structural diagram of the four-stage driven gear. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0023] like Figures 1-6 The figure shows a low-speed, high-torque, high-efficiency, energy-saving, and compact wheel core electric drive system. The system primarily comprises a housing 1, a first support shaft 3, and a motor 2 and a reduction mechanism, all housed within the housing 1. The inner end of the first support shaft 3 extends into the housing 1 and is coaxial with the motor shaft 2a of the motor 2. A wheel hub drive sleeve 5 is mounted on the first support shaft 3, rotatable relative to the first support shaft 3 and configured to drive the wheel hub 21.

[0024] Specifically, the wheel hub drive sleeve 5 partially extends out of the housing 1. After extending out of the housing 1, the wheel hub drive sleeve 5 is fixedly connected to the wheel hub 21, thereby enabling the wheel hub drive sleeve 5 to drive the wheel hub 21 to rotate synchronously therewith. Furthermore, after extending out of the housing 1, the wheel hub drive sleeve 5 has a flange structure that matches the wheel hub 21, thereby enabling a reliable connection to the wheel hub 21 via multiple bolts.

[0025] See Figure 2 and Figure 3 The reduction mechanism not only includes a first countershaft 6 arranged parallel to the motor shaft 2a and a first-stage driving gear 7 mounted on the motor shaft 2a and rotating synchronously, but also includes a double gear 10 that can rotate relative to the motor shaft 2a and a second countershaft 11 arranged parallel to the motor shaft 2a. Moreover, the first countershaft 6 and the second countershaft 11 are distributed circumferentially around the motor shaft 2a, thereby effectively utilizing the radial space. The overall radial size does not increase at all compared with the existing wheel core electric drive system, and the overall structure is extremely compact.

[0026] The first countershaft 6 has a first-stage driven gear 8 and a second-stage driving gear 9, both of which rotate synchronously therewith. The first-stage driving gear 7 meshes with the first-stage driven gear 8. The second countershaft 11 has a third-stage driven gear 12 and a fourth-stage driving gear 13, both of which rotate synchronously therewith. The duplex gear 10 has a second-stage driven tooth 10a meshing with the second-stage driving gear 9 and a third-stage driving tooth 10b meshing with the third-stage driven gear 12. The hub drive sleeve 5 is fitted with a fourth-stage driven gear 14, which meshes with the fourth-stage driving gear 13, for synchronous rotation. The outer diameter of the first-stage driving gear 7 is smaller than the outer diameter of the first-stage driven gear 8, the outer diameter of the second-stage driving gear 9 is smaller than the outer diameter of the second-stage driven tooth 10a, the outer diameter of the third-stage driving tooth 10b is smaller than the outer diameter of the third-stage driven gear 12, and the outer diameter of the fourth-stage driving gear 13 is smaller than the outer diameter of the fourth-stage driven gear 14.

[0027] Therefore, by adding a second countershaft 11, a third-stage gear transmission pair and a fourth-stage gear transmission pair are added to the existing wheel core electric drive system. The four-stage reduction transmission design is utilized to achieve high torque output of a small-power motor under low-speed conditions, and in particular, it can meet the requirements of the new national standard for electric bicycles. Under the conditions of the new national standard for electric bicycles, it can travel easily and stably on a 30% slope at a speed of 5 kilometers, with excellent power and energy saving.

[0028] See Figure 2 and Figure 3 A semi-hollow shaft 15 is coaxially mounted on the outer end of the motor shaft 2a. The end of the semi-hollow shaft 15, which is away from the motor shaft 2a, is rotatably mounted on the housing 1 via a bearing. The duplex gear 10 is rotatably mounted on the outer side of the semi-hollow shaft 15 via a needle roller bearing 16. This design not only improves the reliability of the installation of the motor shaft 2a but also facilitates the installation of the duplex gear 10. Furthermore, the outer end face of the first-stage driving gear 7 abuts the inner end face of the needle roller bearing 16, ensuring the reliability and convenience of the installation of the first-stage driving gear 7.

[0029] See Figure 2 and Figure 4 The housing 1 includes a motor housing 1a and a reducer housing 1b fixedly connected as one body. The reducer housing 1b is divided into a first installation cavity 1b2 and a second installation cavity 1b3 by a middle partition 1b1. The motor 2 is installed in the motor housing 1a, and the outer end of the motor shaft 2a extends into the first installation cavity 1b2. In addition, a bearing and a second oil seal 22 are provided at the connection between the motor housing 1a and the reducer housing 1b, which not only ensures the reliability of the installation of the motor shaft 2a, but also prevents the oil in the reducer housing 1b from leaking out.

[0030] Furthermore, the motor housing 1a and the reducer housing 1b are both provided with end covers that can be opened and closed at their ends away from each other, so as to facilitate the assembly, maintenance and replacement of internal components.

[0031] In order to reduce the thickness of the middle partition 1b1 as much as possible, thereby reducing the overall axial size, the middle partition 1b1 has a partition bearing mounting seat 1b4 protruding toward the first support shaft 3, and the end of the semi-hollow shaft 15 away from the motor shaft 2a is rotatably mounted on the partition bearing mounting seat 1b4 through a bearing. The first mounting cavity 1b2 is provided with a first bearing mounting seat 1b5 adapted to the first auxiliary shaft 6 and a second bearing mounting seat 1b6 adapted to the second auxiliary shaft 11 on the side wall of the cavity close to the motor housing 1a. The second mounting cavity 1b3 is away from the first mounting cavity 1b2. A third bearing mount 1b7, compatible with the second countershaft 11, is provided on the side cavity wall. The first countershaft 6 is rotatably mounted on the first bearing mount 1b5 and the partition bearing mount 1b4 at both ends via bearings. A countershaft through-hole 1b8, compatible with the second countershaft 11, is provided in the intermediate partition 1b1. The second countershaft 11 passes through this through-hole 1b8. One end of the second countershaft 11 is rotatably mounted on the second bearing mount 1b6 via a bearing, while the other end passes through the intermediate partition 1b1 and is rotatably mounted on the third bearing mount 1b7 via a bearing. This structure ensures reliable installation of the reduction mechanism while minimizing the impact on the overall axial dimensions, further enhancing the versatility of the wheel core electric drive system.

[0032] See Figure 2-Figure 4 The inner end of the first support shaft 3 is expanded to form a support shaft mounting seat 3a, which is fixedly connected to the middle partition 1b1 by bolts. The support shaft mounting seat 3a is recessed on one side close to the middle partition 1b1 to form a first clearance groove 3a1 that is compatible with the partition bearing mounting seat 1b4. The partition bearing mounting seat 1b4 extends into the first clearance groove 3a1, further improving the utilization of the axial space and reducing the impact on the overall axial size.

[0033] Furthermore, two shaft mounting platforms 1b9 are protruded on one side of the middle partition 1b1 close to the first support shaft 3, and are relatively arranged on both sides of the partition bearing mounting seat 1b4. The shaft mounting platforms 1b9 are each provided with at least one positioning pin hole 1b10 and multiple partition bolt holes 1b11, and the support shaft mounting seat 3a is provided with mounting seat through holes 3a3 that correspond one-to-one to each positioning pin hole 1b10 and each partition bolt hole 1b11. When installing the first support shaft 3, first position it by passing the positioning pin through the positioning pin hole 1b10 and the mounting seat through hole 3a3, and then lock it by passing the bolt through the partition bolt hole 1b11 and the mounting seat through hole 3a3. This is simple and reliable.

[0034] At the same time, the support shaft mounting seat 3a has a support shaft bearing mounting seat 3a2 on the side away from the middle partition 1b1. The inner end of the wheel hub drive sleeve 5 is rotatably supported on the support shaft bearing mounting seat 3a2 through a bearing, and the outer end of the wheel hub drive sleeve 5 is rotatably supported on the first support shaft 3 through a bearing, ensuring the reliable installation of the wheel hub drive sleeve 5.

[0035] Further, see Figure 2 、 Figure 3 and Figure 6 The fourth-stage driven gear 14 has a second clearance groove 14a on its side near the middle partition 1b1, which is compatible with the support shaft bearing mount 3a2. The support shaft bearing mount 3a2 extends into the second clearance groove 14a, further improving the utilization of axial space and reducing the impact on the overall axial dimensions. Specifically, through the ultra-thin middle partition 1b1, the first clearance groove 3a1 cooperates with the partition bearing mount 1b4, and the second clearance groove 14a cooperates with the support shaft bearing mount 3a2, the axial dimensions of this wheel core electric drive system are equal to those of existing wheel core electric drive systems, completely without affecting the installation and application of this wheel core electric drive system in various traditional usage scenarios.

[0036] The root of the four-stage driven gear 14 has a gear mounting sleeve 14b extending in a direction away from the middle partition 1b1. The inner circumference of the gear mounting sleeve 14b is spline-fitted with the outer circumference of the hub drive sleeve 5. The outer circumference of the gear mounting sleeve 14b is rotatably supported on the inner end of the through hole 1b8 of the second mounting cavity 1b3 through a bearing. A first oil seal 17 is also provided between the outer end of the through hole 1b8 and the outer circumference of the gear mounting sleeve 14b, thereby ensuring reliable installation of the four-stage driven gear 14 and avoiding oil leakage.

[0037] Further, see Figure 2 A third oil seal 23 is further provided between the inner circumference of the outer end of the hub drive sleeve 5 and the first support shaft 3. The third oil seal 23 is located on the outside of the adjacent bearing, thereby further avoiding the problem of oil leakage.

[0038] See Figure 1 and Figure 2 A second support shaft 18 is fixedly installed on the side of the motor housing 1a away from the reducer housing 1b. The second support shaft 18 is coaxially arranged with the first support shaft 3. The two flat fork arms of the flat fork 19 are respectively locked on the first support shaft 3 and the second support shaft 18 through two corresponding locking nuts 20, which is simple and reliable.

[0039] Furthermore, a disc brake 24 (or a drum brake) is provided between the wheel hub 21 and the first support shaft 3, thereby realizing the integration and installation of the brake.

[0040] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention. Such changes fall within the scope of protection of the present invention.

Claims

1. A low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system, comprising a housing (1), a motor (2) and a reduction mechanism both arranged in the housing (1), and a first support shaft (3) coaxially arranged with a motor shaft (2a) of the motor (2), wherein the first support shaft (3) is provided with a wheel hub drive sleeve (5) capable of rotating relative thereto, and the wheel hub drive sleeve (5) and the first support shaft (3) both partially extend out of the housing (1), the reduction mechanism comprises a first countershaft (6) arranged parallel to the motor shaft (2a) and a primary driving gear (7) synchronously rotated and mounted on the motor shaft (2a), the first countershaft (6) having a primary driven gear (8) and a secondary driving gear (9) both rotating synchronously therewith, the primary driving gear (7) meshing with the primary driven gear (8), and the system is characterized in that: The speed reduction mechanism further comprises a double gear (10) capable of rotating relative to the motor shaft (2a) and a second secondary shaft (11) arranged parallel to the motor shaft (2a); the first secondary shaft (6) and the second secondary shaft (11) are circumferentially distributed around the motor shaft (2a); the second secondary shaft (11) is provided with a three-stage driven gear (12) and a four-stage driving gear (13) which rotate synchronously therewith; the double gear (10) is provided with a two-stage driven tooth (10a) meshing with the two-stage driving gear (9) and a three-stage driving tooth (10b) meshing with the three-stage driven gear (12); and the hub drive sleeve (5) is provided with a four-stage driven gear (14) meshing with the four-stage driving gear (13) which rotates synchronously therewith.

2. The low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system according to claim 1 is characterized by: The outer end of the motor shaft (2a) is coaxially fitted with a semi-hollow shaft (15); the end of the semi-hollow shaft (15) away from the motor shaft (2a) is rotatably mounted on the housing (1) via a bearing; and the double gear (10) is rotatably fitted outside the semi-hollow shaft (15) via a needle bearing (16).

3. The low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system according to claim 2 is characterized by: The housing (1) comprises a motor housing (1a) and a reducer housing (1b) fixedly connected as one body, the reducer housing (1b) being divided into a first installation cavity (1b2) and a second installation cavity (1b3) by a middle partition (1b1), the motor (2) being installed in the motor housing (1a), the outer end of the motor shaft (2a) extending into the first installation cavity (1b2), the middle partition (1b1) having a partition bearing mounting seat (1b4) protruding toward the first support shaft (3), the end of the semi-hollow shaft (15) away from the motor shaft (2a) being rotatably mounted on the partition bearing mounting seat (1b4) via a bearing, the first installation cavity (1b2) being adjacent to a side cavity of the motor housing (1a) A first bearing mounting seat (1b5) adapted to the first secondary shaft (6) and a second bearing mounting seat (1b6) adapted to the second secondary shaft (11) are provided on the wall; a third bearing mounting seat (1b7) adapted to the second secondary shaft (11) is provided on the cavity wall of the second mounting cavity (1b3) away from the first mounting cavity (1b2); both ends of the first secondary shaft (6) are rotatably mounted on the first bearing mounting seat (1b5) and the partition bearing mounting seat (1b4) respectively through bearings; one end of the second secondary shaft (11) is rotatably mounted on the second bearing mounting seat (1b6) through a bearing, and the other end passes through the middle partition (1b1) and is rotatably mounted on the third bearing mounting seat (1b7) through a bearing.

4. The low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system according to claim 3 is characterized by: The inner end of the first support shaft (3) is enlarged to form a support shaft mounting seat (3a), and the support shaft mounting seat (3a) is fixedly connected to the middle partition (1b1) by bolts. The support shaft mounting seat (3a) is recessed on one side close to the middle partition (1b1) to form a first clearance groove (3a1) adapted to the partition bearing mounting seat (1b4), and the partition bearing mounting seat (1b4) extends into the first clearance groove (3a1). The support shaft mounting seat (3a) is provided with a support shaft bearing mounting seat (3a2) on the side away from the middle partition (1b1). The inner end of the wheel hub drive sleeve (5) is rotatably supported on the support shaft bearing mounting seat (3a2) through a bearing, and the outer end of the wheel hub drive sleeve (5) is rotatably supported on the first support shaft (3) through a bearing.

5. The low-speed, high-torque, high-efficiency, energy-saving, and compact wheel core electric drive system according to claim 4 is characterized by: The fourth-stage driven gear (14) has a second clearance groove (14a) on one side close to the middle partition (1b1) and adapted to the support shaft bearing mounting seat (3a2), and the support shaft bearing mounting seat (3a2) extends into the second clearance groove (14a).

6. The low-speed, high-torque, high-efficiency, energy-saving, and compact wheel core electric drive system according to claim 5 is characterized by: The root of the four-stage driven gear (14) has a gear mounting sleeve (14b) extending in a direction away from the middle partition (1b1). The inner peripheral surface of the gear mounting sleeve (14b) is spline-matched with the outer peripheral surface of the hub drive sleeve (5). The outer peripheral surface of the gear mounting sleeve (14b) is rotatably supported on the inner end of the through hole (1b8) of the second mounting cavity (1b3) through a bearing. A first oil seal (17) is also provided between the outer end of the through hole (1b8) and the outer peripheral surface of the gear mounting sleeve (14b).

7. The low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system according to claim 3 is characterized by: A second support shaft (18) is fixedly mounted on a side of the motor housing (1a) away from the reducer housing (1b), and the second support shaft (18) is coaxially arranged with the first support shaft (3). The two flat fork arms of the flat fork (19) are locked on the first support shaft (3) and the second support shaft (18) respectively through two corresponding locking nuts (20).

8. The low-speed, high-torque, high-efficiency, energy-saving, compact wheel core electric drive system according to claim 1 is characterized by: The wheel hub drive sleeve (5) is sleeved with a wheel hub (21) for synchronous rotation.

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