Light wheel hub motor

Abstract

The invention relates to a light hub motor. The light hub motor comprises a middle shaft, a shell assembly and a stator and rotor assembly, wherein the middle shaft is fixedly arranged; the shell assembly comprises a box body and a cover plate, the box body and the cover plate are combined to form a closed internal space, and the stator and rotor assembly is arranged in the internal space; the stator and rotor assembly comprises a stator and a rotor, the stator is fixedly connected with the center shaft, the rotor is fixedly connected with the shell assembly, and the stator and the rotor form an axial magnetic flux path. The stator and the rotor of the motor form an axial magnetic flux path, the overall mass is lighter, and the heat dissipation effect is good.

Description

Technical Field

[0001] The present application relates to the field of electric-assisted bicycles, and in particular to a lightweight hub motor. Background Art

[0002] The electric-assisted bicycle is a new type of transportation that integrates electric-assisted power with traditional bicycles. The electric-assisted power is provided by the motor. Hub motors and mid-mounted motors are the two major types of motors currently used in electric-assisted bicycles. The mid-mounted motor has better weight distribution because it is installed on the bicycle's bottom bracket, but it cannot occupy the mainstream market due to its complex structure and high cost. Based on economic considerations, the lower-cost hub motor is more popular in the market.

[0003] The hub motor is installed on the bicycle wheel hub, and the structure is simpler. The European invention patent with the publication number EP2921397B1 discloses a hub motor for an electric bicycle, which includes an internal stator, an external rotor, a reduction gear, etc. However, the hub motor increases the mass of the wheel, making the mass distribution of the front and rear wheels of the electric-assisted bicycle uneven, thus affecting the controllability and comfort of the electric-assisted bicycle. Summary of the invention

[0004] In order to solve the above problems, the present application provides a lightweight hub motor.

[0005] The present application provides a lightweight hub motor, which adopts the following technical solution: A lightweight hub motor comprises a central shaft, a shell assembly and a stator-rotor assembly; wherein the central shaft is fixedly arranged; the shell assembly comprises a box body and a cover plate, the box body and the cover plate together constitute a closed internal space, and the stator-rotor assembly is arranged in the internal space; the stator-rotor assembly comprises a stator and a rotor, the stator is fixedly connected to the central shaft, the rotor is fixedly connected to the shell assembly, and the stator and the rotor form an axial magnetic flux path.

[0006] Optionally, the internal space is virtually divided into an installation space and a heat dissipation space, and the installation space and the heat dissipation space are distributed along the axial direction, wherein the installation space is arranged close to the cover plate, and the axial length of the heat dissipation space is much larger than the axial length of the installation space; the stator and rotor assembly is arranged in the installation space.

[0007] Optionally, the axial length of the heat dissipation space is at least three times the axial length of the installation space.

[0008] Optionally, the stator is a printed circuit board stator, including a substrate, on which a plurality of winding groups are etched, and the plurality of winding groups are rotationally symmetrically arranged about a central axis of the substrate.

[0009] Optionally, the rotor is integrated with the cover plate, the rotor comprises a plurality of permanent magnets, the plurality of permanent magnets are rotationally symmetrically arranged about a central axis of the cover plate, and the permanent magnets are directly or indirectly fixedly connected to the cover plate.

[0010] Optionally, a heat sink is further included, wherein the heat sink is directly or indirectly fixedly connected to the central axis, the heat sink extends from the installation space to the heat dissipation space, and one end of the heat sink abuts against the stator.

[0011] Optionally, a radial length of the heat sink in the installation space is greater than a radial length of the heat sink in the heat dissipation space.

[0012] Optionally, the stator-rotor assembly includes two rotors, one of which is integrated with a cover plate; the other rotor is fixedly mounted on the housing; and the stator is located between the two rotors.

[0013] Optionally, the rotor includes a rotor disk and a permanent magnet, and an installation groove for installing the permanent magnet is opened on the end surface of the rotor disk, and the permanent magnet is fixedly installed in the installation groove.

[0014] Specifically, the box body includes an end plate, a side plate, a flange and a boss which are fixedly connected to each other; wherein, the end plate is used to shield one end surface of the motor as a whole, the side plate is used to shield the surrounding side surface of the motor as a whole, the boss is arranged on the end plate for the central axis to pass through, and the flange protrudes from the outer surface of the side plate to provide a limit for the wheel hub.

[0015] Specifically, the cover plate includes an end plate, an inner edge and a boss which are fixedly connected to each other; wherein the boss is arranged on the end plate for the central axis to pass through; the inner edge protrudes from the inner end surface of the cover plate, is annular and is used to fit with the inner circumference of the side plate.

[0016] Specifically, the winding is a combined winding, a circular winding, a trapezoidal winding or a rhombus winding.

[0017] Specifically, the permanent magnet is circular or rectangular.

[0018] Specifically, the stator is fixedly mounted on the central axis via a connecting assembly; wherein the connecting assembly comprises a connecting piece, a fixing piece and a gasket, the fixing piece is fixedly connected to the central axis, and the connecting piece passes through the gasket and the stator threadedly connected to the fixing piece in sequence.

[0019] Specifically, a mounting boss is fixedly provided on the inner circumference of the side plate, and the rotor disk is fixedly connected to the mounting boss.

[0020] In the present application, the stator and the rotor form an axial magnetic flux path, and the stator adopts a printed circuit board stator (PCB stator). Compared with the stator and rotor of the traditional hub motor (such as the inner stator and outer rotor in EP2921397B1, that is, the copper wire winding stator), the overall mass of the stator and rotor assembly in the present application is greatly reduced, and the overall mass of the hub motor is reduced accordingly. When the motor is applied to the wheel hub of an electric power-assisted bicycle, the mass difference between the wheel hub with the motor installed and the wheel hub without the motor installed is reduced, so that the mass distribution of the front and rear wheels of the electric power-assisted bicycle is more uniform, which is beneficial for the rider to operate and control the electric power-assisted bicycle.

[0021] In addition, the rotor of the present application can be integrated on the cover plate, saving raw materials while further reducing the mass of the stator-rotor assembly structure. The stator-rotor assembly is arranged in the installation space close to the cover plate, and a large amount of heat dissipation space is left inside the housing assembly, so that the heat dissipation effect of the stator-rotor assembly is better. In order to further improve the heat dissipation effect, a heat sink can also be provided, and the heat sink abuts against the stator to quickly conduct the heat on the stator to the heat dissipation space.

[0022] In addition, in order to provide greater auxiliary power, the stator-rotor assembly may also adopt a single-stator dual-rotor structure, that is, one rotor is integrated on the cover plate, the other rotor is fixedly connected to the casing, and the stator is arranged between the two rotors. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of a lightweight hub motor according to an embodiment of the present application.

[0024] Figure 2 This is a structural cross-sectional view of a lightweight hub motor according to an embodiment of the present application.

[0025] Figure 3 It is a schematic diagram of the overall structure of a box in a lightweight hub motor according to an embodiment of the present application.

[0026] Figure 4 It is a schematic diagram of the overall structure of a cover plate in a lightweight hub motor according to an embodiment of the present application.

[0027] Figure 5 This is a structural cross-sectional view of a lightweight hub motor according to an embodiment of the present application.

[0028] Figure 6 It is a schematic diagram of the overall structure of a stator in a lightweight hub motor according to an embodiment of the present application.

[0029] Figure 7 It is a schematic diagram of stator windings of different forms in a lightweight hub motor according to an embodiment of the present application.

[0030] Figure 8 yes Figure 2 A magnified view of the structure of part A.

[0031] Fig. 9 This is a structural cross-sectional view of a lightweight hub motor according to an embodiment of the present application.

[0032] Fig.10 This is a structural cross-sectional view of a lightweight hub motor according to an embodiment of the present application.

[0033] Fig.11 It is a schematic diagram of the overall structure of a rotor in a lightweight hub motor according to an embodiment of the present application.

[0034] Explanation of the reference numerals: 100, central axis; 200, housing assembly; 201, installation space; 202, heat dissipation space; 210, housing; 211, first end plate; 212, side plate; 213, first flange; 214, second flange; 215, first boss; 220, cover plate; 221, second end plate; 222, inner edge; 223, second boss; 300, stator-rotor assembly; 310, stator; 311, PCB substrate; 312, winding; 320, rotor; 321, rotor disk; 322, permanent magnet; 331, fixing member; 332, gasket; 340, heat sink. DETAILED DESCRIPTION

[0035] The following is combined with Figure 1-11 , further details of this application are given.

[0036] The embodiment of the present application discloses a lightweight hub motor, which is applied to the hub of an electric power-assisted bicycle to provide auxiliary power for the rider. Example 1

[0037] Reference Figure 1 and Figure 2 A lightweight hub motor includes a middle shaft 100, a housing assembly 200 and a stator-rotor assembly 300; the motor as a whole is generally cylindrical in structure. The middle shaft 100 is fixedly mounted on the frame of an electric power-assisted bicycle, the housing assembly 200 is fixedly connected to the wheel hub of the electric power-assisted bicycle, and the stator-rotor assembly 300 provides electric power for the motor as a whole.

[0038] Reference Figure 2 and Figure 3The housing assembly 200 includes a housing 210 and a cover plate 220. The housing 210 includes a first end plate 211, a side plate 212, a first flange 213, a second flange 214 and a first boss 215. In this embodiment, the first end plate 211, the side plate 212, the first flange 213, the second flange 214 and the first boss 215 are integrally formed. The first end plate 211 is used to shield one end face of the cylindrical structure of the motor. The side plate 212 is connected to the inner end face of the first end plate 211 and is used to shield the peripheral side face of the cylindrical structure of the motor. The first flange 213 is enclosed on the outer periphery of the first end plate 211 and protrudes from the outer surface of the side plate 212. The second flange 214 is enclosed on the outer periphery of the side plate 212 away from the first end plate 211 and protrudes from the outer surface of the side plate 212. The first flange 213 and the second flange 214 are relatively parallel and protrude from the overall outer surface of the motor, providing a limit for the wheel hub of the electric power-assisted bicycle. The first boss 215 is coaxial with the cylindrical structure of the motor and is disposed at the center of the first end plate 211 . The first boss 215 is hollow for the central shaft 100 to pass through.

[0039] Reference Figure 4 , the cover plate 220 includes a second end plate 221, an inner edge 222 and a second boss 223. In this embodiment, the second end plate 221, the inner edge 222 and the second boss 223 are integrally formed. The second end plate 221 is fitted with one end of the side plate 212 away from the first end plate 211, and is used to shield the other end face of the cylindrical structure of the motor. The inner edge 222 is annular, which is arranged on the inner end face of the second end plate 221, and the outer peripheral side of the inner edge 222 is fitted with the inner peripheral side of the side plate 212, providing better airtightness for the motor as a whole, and at the same time providing positioning for the connection between the cover plate 220 and the box body 210, ensuring the relative position of the cover plate 220 and the box body 210. The second boss 223 is coaxial with the cylindrical structure of the motor, and is arranged at the center of the second end plate 221. The second boss 223 is hollow for the central axis 100 to pass through.

[0040] Reference Figure 5 The housing assembly 200 composed of the box body 210 and the cover plate 220 encloses a closed internal space. In the present application, the internal space is virtually divided into an installation space 201 distributed along the axial direction of the motor (such as Figure 5 The shaded portion shown in the upper part) and the heat dissipation space 202 (such as Figure 5 The installation space 201 is arranged near the cover plate 220, and the heat dissipation space 202 is arranged near the first end plate 211; wherein the size of the heat dissipation space 202 is much larger than the size of the installation space 201. That is to say, in a similar Figure 5 In the axial cross section, the axial length of the heat dissipation space 202 is much greater than the axial length of the installation space 201. In actual design, the axial length of the heat dissipation space 202 is at least three times the axial length of the installation space 201.

[0041] Reference Figure 4 and Figure 6 , the stator-rotor assembly 300 includes a stator 310 and a rotor 320. The stator-rotor assembly 300 is located as a whole in the internal space of the housing assembly 200. More precisely, the stator-rotor assembly 300 is located as a whole in the installation space 201. In the present application, the stator 310 adopts a printed circuit board stator (PCB stator), that is, multiple groups of windings 312 are etched on the PCB substrate 311, and the multiple groups of windings 312 are rotationally symmetrically arranged about the central axis of the PCB substrate 311. The shape of the winding 312 can be a combined winding, a circular winding, a trapezoidal winding or a rhombus winding, such as Figure 7 It should be noted that the position, structure and number of the winding 312 shown in the drawings are only exemplary, and do not limit the position, structure and number of the winding protected in this application.

[0042] Reference Figure 4 In this embodiment, the rotor 320 is integrated with the cover plate 220, and the rotor 320 includes a plurality of permanent magnets 322, which are arranged rotationally symmetrically about the central axis of the cover plate 220. The shape of the permanent magnet 322 can be circular, rectangular, etc. It should be noted that the position, structure and number of the permanent magnets 322 shown in the drawings are only exemplary, and do not limit the position, structure and number of the permanent magnets protected in this application, nor do they limit the pole-slot ratio of the stator-rotor assembly 300 protected in this application.

[0043] The stator 310 and the rotor 320 in the present application are arranged at intervals along the axial direction of the motor, and the direction of the magnetic flux path formed is parallel to the axial direction of the motor and is closed along the axial and circumferential directions, forming an internal magnetic field of a three-dimensional structure as a whole, which greatly reduces the axial length of the stator-rotor assembly 300 compared to the prior art. In addition, the stator-rotor assembly 300 only occupies a small part of the internal space of the housing assembly 200, leaving a large amount of space for heat dissipation. For example, if the motor of the present application is applied to an electric power-assisted bicycle wheel hub with a gear opening of 135mm, then the distance between the first flange 213 and the second flange 214 is about 72mm, and the axial length of the internal space of the housing assembly 200 is about 80mm. Since the rotor 320 is directly integrated on the cover plate 220, the axial length of the internal space occupied by the rotor 320 is approximately the thickness of the permanent magnet, which is usually 3mm. The axial air gap between the stator 310 and the rotor 320 is about 1 mm, and the thickness of the PCB stator is about 4 mm. Therefore, the overall axial length of the stator-rotor assembly 300 is much smaller than the axial length of the internal space of the box 210, that is, the virtually divided heat dissipation space 202 is much larger than the installation space 201, and the stator-rotor assembly 300 provides better heat dissipation conditions. In addition, the overall weight of the stator-rotor assembly 300 is only the total weight of the PCB stator and the permanent magnet 322. Compared with the traditional copper wire winding motor, the motor in this application is lighter as a whole.

[0044] Reference Figure 7 , the stator 310 is fixedly mounted on the central shaft 100 through a connecting assembly. Specifically, the central shaft 100 is provided with a positioning step, and one end face of the stator 310 away from the rotor 320 abuts on the positioning step. The fixing member 331 is fixed to the central shaft 100 through a key connection, and one end face of the stator 310 away from the rotor 320 abuts on the end face of the fixing member 331; the gasket 332 is sleeved on the central shaft 100, and the gasket 332 abuts on one end face of the stator 310 close to the rotor 320. The screw passes through the gasket 332 in sequence, and the stator 310 is threadedly connected to the fixing member 331, so as to fix the stator 310.

[0045] The fixing method of the stator 310 and the central axis 100 is not limited to the above method. In another embodiment, the central axis 100 may be provided with a mounting step, and the screws pass through the gasket 332, the stator 310 and the mounting step in sequence to achieve the fixing of the stator 310. The structure omitting the gasket 332 may also be another alternative.

[0046] Reference Figure 4 The rotor 320 is fixedly connected to the cover plate 220. Specifically, the permanent magnet 322 can be directly bonded to the inner surface of the cover plate 220 by glue; or a positioning groove for installing the permanent magnet 322 can be provided on the inner surface of the cover plate 220, and the permanent magnet 322 can be bonded in the positioning groove. Example 2

[0047] Based on the solution of Example 1, a heat sink 340 is also installed in the internal space, and the heat sink 340 extends from the installation space 201 to the heat dissipation space 202; a plurality of heat sinks 340 can be provided, and the plurality of heat sinks 340 are rotationally symmetrically distributed along the central axis 100. Fig. 9 The cross section of the heat sink 340 is roughly trapezoidal, and it is clamped and fixed in the central axis 100 and the fixing member 331. In this embodiment, one end of the heat sink 340 abuts against the back side of the stator 310 (the side away from the rotor 320), and the heat generated by the stator 310 is quickly transferred to the heat dissipation space 202. In other embodiments, the heat sink 340 can also adopt other shapes, but its radial length in the installation space 201 must be greater than its radial length in the heat dissipation space 202, and its radial length can be continuously changed or discontinuously changed; that is, the side of the heat sink 340 away from the central axis 100 can be a continuous straight line or curve, or a stepped straight line or curve. Example 3

[0048] Based on the solution of embodiment 1, the stator-rotor assembly 300 includes a stator 310 and two rotors 320. Fig.10 , one rotor 320a is integrated with the cover plate 220, and the other rotor 320b is installed on the side of the stator 310 away from the cover plate 220. Specifically, refer to Fig.11The rotor 320 includes a rotor disk 321 and a permanent magnet 322. A mounting groove for mounting the permanent magnet 322 is provided on one end surface of the rotor disk 321, and the mounting groove does not penetrate the rotor disk 321. The permanent magnet 322 is bonded in the mounting groove by glue. The rotor disk 320a is fixedly mounted on the cover plate 220. A mounting boss is fixedly provided on the inner circumference of the side plate 212, and the rotor disk 320b is fixedly connected to the mounting boss. The fixed connection between the rotor disk 321 and the cover plate 220 / mounting boss can be achieved by screws, bolts, integral molding, gluing, etc.

[0049] It should be noted that ordinal numbers such as "first" and "second" cited in this application are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term "first component" itself does not imply the existence of a "second component", and the term "second component" itself does not imply the existence of a "first component".

[0050] The "coaxial" and "parallel" mentioned in this application are all allowed to have tolerances within a reasonable range. The term "axial" in this application refers to the direction of the central axis of rotation of the cylinder for cylindrical objects, that is, the direction common to the central axis; "radial" is perpendicular to the "axial", that is, the radius or diameter direction of the end circle of the cylinder; "circumferential" refers to the "circumferential direction", that is, the direction around the axis of the cylinder, which together with the "axial" and "radial" constitute the three orthogonal directions of the cylindrical coordinates.

[0051] In order to better demonstrate the invention of this application, some conventional structures inside the motor, such as bearings, wiring harnesses, etc., are omitted in the drawings and description of this application. These are features or structures known to those skilled in the art and are not described in detail in this application. In addition, in order to more clearly demonstrate the structure of this application, some structures in the drawings are enlarged in proportion. Therefore, the dimensional ratios shown in the drawings do not limit the scope of this application.

[0052] The "present embodiment", "another embodiment" or similar expressions quoted in the specification of this application mean that the features or structures related to the embodiment are included in at least one embodiment disclosed in this application. Therefore, those skilled in the art can obtain new alternatives by combining and transforming the features between different embodiments, and all alternatives should be included in the protection scope of this application.

Claims

1. A lightweight hub motor, characterized in that: It includes a central shaft, a housing assembly and a stator and rotor assembly; wherein, The central axis is fixedly arranged; The housing assembly comprises a box body and a cover plate, wherein the box body and the cover plate are combined to form a closed internal space, and the stator and rotor assembly is arranged in the internal space; The stator-rotor assembly comprises a stator and a rotor, wherein the stator is fixedly connected to the central shaft, the rotor is fixedly connected to the housing assembly, and the stator and the rotor form an axial magnetic flux path.

2. A lightweight hub motor according to claim 1, characterized in that: The internal space is virtually divided into an installation space and a heat dissipation space, which are distributed axially. The installation space is arranged close to the cover plate, and the axial length of the heat dissipation space is much larger than the axial length of the installation space. The stator and rotor assembly is arranged in the installation space.

3. A lightweight hub motor according to claim 2, characterized in that: The axial length of the heat dissipation space is at least three times the axial length of the installation space.

4. A lightweight hub motor according to claim 1 or 2, characterized in that: The stator adopts a printed circuit board stator, which includes a substrate; a plurality of winding groups are etched on the substrate, and the plurality of winding groups are rotationally symmetrically arranged about the central axis of the substrate.

5. A lightweight hub motor according to claim 4, characterized in that: The rotor is integrated with the cover plate, and the rotor comprises a plurality of permanent magnets, which are arranged rotationally symmetrically about a central axis of the cover plate, and the permanent magnets are directly or indirectly fixedly connected to the cover plate.

6. A lightweight hub motor according to claim 2, characterized in that: It also includes a heat sink, which is directly or indirectly fixedly connected to the central axis, and the heat sink extends from the installation space to the heat dissipation space, and one end of the heat sink abuts against the stator.

7. A lightweight hub motor according to claim 6, characterized in that: The radial length of the heat sink in the installation space is greater than the radial length of the heat sink in the heat dissipation space.

8. The lightweight hub motor according to claim 2, characterized in that: The stator-rotor assembly comprises two rotors, one of which is integrated with a cover plate; the other rotor is fixedly mounted on the housing; and the stator is located between the two rotors.

9. A lightweight hub motor according to claim 8, characterized in that: The rotor comprises a rotor disk and a permanent magnet. An installation groove for installing the permanent magnet is provided on the end surface of the rotor disk, and the permanent magnet is fixedly installed in the installation groove.

10. The lightweight hub motor according to claim 1, characterized in that: The box body includes an end plate, a side plate and two flanges fixedly connected to each other; the cover plate includes an end plate and an inner edge fixedly connected to each other; wherein the end plate is used to shield the end face of the motor as a whole, the side plate is used to shield the peripheral side face of the motor as a whole, the two flanges protrude from the outer surface of the side plate to provide a limit for the wheel hub; the inner edge protrudes from the inner end face of the cover plate to fit with the inner peripheral side of the side plate.

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