Rotor assembly, assembly method, and hub motor

Abstract

Disclosed in the present invention are a rotor assembly, an assembly method, and a hub motor, for solving the technical problem in the prior art that a rotor assembly is prone to nonconforming assembly. The rotor assembly comprises a rotor shell and a rotor iron core. Positioning ribs are provided on the inner side wall of the rotor shell, positioning grooves having one-to-one correspondence to the positioning ribs are formed on the outer wall of the rotor iron core in the axial direction, and circumferential positioning and fixing between the rotor shell and the rotor iron core can be achieved by directly inserting the positioning ribs into the positioning grooves. Compared with the method in the prior art of aligning first and then fixing by means of positioning pins, there will be no nonconforming assembly due to circumferential assembly angle error, the assembly process is simple, and the assembly time is reduced.

Description

Rotor assembly, assembly method, and hub motor Technical Field

[0001] The present application belongs to the technical field of hub motors, and specifically relates to a rotor assembly, an assembly method, and a hub motor. Background Art

[0002] As the ultimate form of electric vehicle, in-wheel motors offer advantages such as simple structure, high efficiency, and ample vehicle space. They are a major trend in future automotive development. Generally speaking, an in-wheel motor consists of a rotor assembly and a stator. The rotor assembly consists of a rotor housing and a rotor core. Assembly requires sequentially installing the rotor core into the rotor housing and connecting the two.

[0003] In the prior art, circumferential positioning between the rotor housing and the rotor core is generally achieved by providing locating pins on the mating surfaces of the rotor housing and the rotor core. Specifically, the rotor housing and the rotor core are first assembled, during which the pin holes of the rotor housing and the rotor core need to be aligned before the locating pins are inserted into the pin holes. However, due to the circumferential assembly angle error between the rotor housing and the rotor core, the locating pins are difficult to assemble, which can easily lead to assembly failures. Furthermore, the assembly process is complex and requires a long time.

[0004] Summary of the Invention

[0005] In order to solve the technical problems that the current rotor assembly uses circumferential limitation between the rotor shell and the rotor core through locating pins, the circumferential assembly angle error between the rotor shell and the rotor core in the circumferential direction makes the locating pins difficult to assemble, and assembly failures are likely to occur. In addition, the assembly process is complicated and the working hours required are long. The present application provides a rotor assembly, an assembly method and a hub motor.

[0006] In a first aspect of the present application, a rotor assembly is provided, comprising:

[0007] A rotor housing, wherein the inner side wall of the rotor housing is provided with a plurality of positioning ribs along the axial direction;

[0008] The rotor core has an outer wall axially provided with positioning grooves corresponding to the positioning ribs one by one, and the positioning grooves are configured to be inserted into the positioning ribs.

[0009] In some embodiments, the rotor core includes multiple rotor punchings stacked axially, multiple positioning holes are provided on the outer walls of the rotor punchings, the positioning holes of the multiple rotor punchings are aligned to form the positioning grooves, and a through hole configured to install the stator assembly is provided in the middle of the rotor punchings.

[0010] In some embodiments, the positioning rib and the positioning groove are interference fit.

[0011] In some embodiments, the rotor core further includes a plurality of magnets, a plurality of magnet slots are provided on the rotor core, the magnets are installed in the magnet slots, two of the magnet slots form a magnet slot group, the number of the positioning slots is a common divisor of the number of the magnet slot groups; the positioning slot is located in the middle of two of the magnet slots in the magnet slot group, or the positioning slot is located between two adjacent magnet slot groups.

[0012] In some embodiments, a plurality of reinforcing ribs are radially provided on the inner end surface of the rotor housing; and an extension line of the reinforcing ribs intersects with an extension line of the positioning ribs.

[0013] In a second aspect of the present application, there is provided an assembly method for the rotor assembly according to the first aspect, comprising the following steps:

[0014] stacking a plurality of rotor blanks and punching them out as a whole to obtain a plurality of rotor punching sheets;

[0015] A plurality of rotor punchings are installed in the rotor housing in a posture where two adjacent rotor punchings are rotated by a preset angle.

[0016] In some embodiments, the step of installing the plurality of rotor punchings in the rotor housing with two adjacent rotor punchings rotated by a preset angle specifically includes:

[0017] Rotating at least part of the rotor punchings by a preset angle so that any two adjacent rotor punchings are staggered by a preset angle and the positioning holes on the rotor punchings are aligned to form the positioning grooves;

[0018] Align the positioning grooves of the plurality of rotor punchings with the positioning ribs, and move the plurality of rotor punchings relative to the rotor housing so that the positioning ribs are inserted into the positioning grooves until the plurality of rotor punchings are integrally installed in the rotor housing.

[0019] In some embodiments, the step of installing the plurality of rotor punches in the rotor housing with two adjacent rotor punches rotated by a preset angle specifically includes: rotating the rotor punch by a preset angle relative to the previous rotor punch, and fitting the positioning holes of the rotor punches onto the positioning ribs, so that each rotor punch is installed in the rotor housing in sequence.

[0020] In some embodiments, the preset angle is an integer multiple of the angle between two adjacent positioning ribs.

[0021] In a third aspect of the present application, a hub motor is provided, comprising a stator assembly and the rotor assembly described in the first aspect, wherein the stator assembly is installed inside the rotor core.

[0022] A rotor assembly provided according to one or more embodiments of the present application has the following beneficial effects compared to the prior art:

[0023] Positioning ribs are provided on the inner wall of the rotor shell, and positioning grooves corresponding to the positioning ribs are provided on the outer wall of the rotor core in the axial direction. The circumferential positioning and fixation between the rotor shell and the rotor core can be achieved by directly inserting the positioning ribs into the positioning grooves. Compared with the existing technology of first aligning and then fixing with positioning pins, there will be no assembly failure due to circumferential assembly angle error, and the assembly process is simple, reducing assembly time. Moreover, the rotor shell and the rotor core are assembled by cooperating with the positioning ribs and the positioning grooves, without the need for limit pins, reducing the number of parts, simplifying the structure of the rotor assembly, reducing the cost of the rotor assembly, and the positioning ribs can also increase the strength of the rotor shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 shows a schematic structural diagram of a rotor assembly in an embodiment of the present application.

[0025] FIG2 shows a schematic structural diagram of a rotor housing of a rotor assembly in an embodiment of the present application.

[0026] FIG3 shows a schematic structural diagram of a rotor core of a rotor assembly in an embodiment of the present application.

[0027] Explanation of the accompanying numbers: 100-rotor housing, 110-inner wall, 1101-positioning rib, 120-inner end face, 1201-reinforcement rib; 200-rotor core, 201-positioning groove, 202-magnetic steel groove, 203-magnetic steel groove group, 210-rotor punching, 2101-positioning hole, 2102-through hole, 220-magnetic steel. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to understand the present application more clearly, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of this application.

[0029] 1 to 3 , an embodiment of a first aspect of the present application provides a rotor assembly, including a rotor housing 100 and a rotor core 200 . The rotor core 200 includes a plurality of rotor punchings 210 stacked in an axial direction.

[0030] The inner sidewall 110 of the rotor housing 100 is axially provided with a number of positioning ribs 1101. The rotor housing 100 is shaped like a cylinder with an open top, and the positioning ribs 1101 protrude from the inner sidewall 110 of the rotor housing 100. The positioning ribs 1101 are provided axially along the rotor housing 100 to increase the strength of the inner sidewall 110 of the rotor housing 100. The cross-sectional shape of the positioning ribs can be semicircular, elliptical, or rounded rectangular. Semicircular and elliptical shapes are more tolerant of dimensional errors and provide better axial guidance, thereby improving the stability and reliability of the device.

[0031] The outer wall of the rotor core 200 is provided with positioning grooves 201 along the axial direction, corresponding one-to-one with the positioning ribs 1101. The positioning grooves 201 are configured to be inserted into the positioning ribs 1101. The cross-section of the rotor core 200 is annular. The positioning grooves 201 are provided on the outer wall of the rotor core 200 and are arranged along the axial direction of the rotor core 200. When the rotor core 200 is placed in the rotor housing 100, after the positioning grooves 201 and the positioning ribs 1101 are inserted and matched, and the bottom surface of the rotor core 200 and the bottom surface of the rotor housing 100 are in contact, the rotor core 200 and the rotor housing 100 are fixedly connected and mutually limited in the circumferential direction.

[0032] The raised height of the positioning rib 1101 can be equal to the recessed depth of the positioning groove 201, so that the positioning rib 1101 can be just stuck in the positioning groove 201. The raised height of the positioning rib 1101 can be smaller than the recessed depth of the positioning groove 201, which facilitates the insertion of the positioning rib 1101 into the positioning groove and leaves a certain radial gap between the positioning rib 1101 and the positioning groove 201. The radial gap can compensate for the axial error between the positioning groove 201 and the positioning rib 1101, and the positioning groove 201 can also limit the circumferential position of the positioning rib 1101.

[0033] The rotor assembly provided in the embodiment of the present application is provided with a positioning rib 1101 on the inner side wall 110 of the rotor housing 100, and a positioning groove 201 corresponding to the positioning rib 1101 is provided on the outer wall of the rotor core 200 along the axial direction. The circumferential positioning and fixation between the rotor housing 100 and the rotor core 200 can be achieved by directly inserting the positioning rib 1101 into the positioning groove 201. Compared with the prior art method of aligning first and then fixing with a positioning pin, the rotor housing 100 and the rotor core 200 will not be unable to be fixed due to circumferential assembly angle error, and the assembly process is simple, reducing assembly time. Moreover, by cooperating with the positioning rib 1101 and the positioning groove 201, the rotor housing 100 and the rotor core 200 are assembled, without the need for a limit pin, reducing the number of parts, simplifying the structure of the rotor assembly, and reducing the cost of the rotor assembly. The positioning rib 1101 can also play a role in enhancing the strength of the rotor housing.

[0034] In some embodiments, multiple positioning holes 2101 are provided on the outer wall of the rotor punching 210. The positioning holes 2101 of multiple rotor punchings 210 are aligned to form a positioning groove 201. A through hole 2102 is provided in the center of the rotor punching 210 for mounting the stator assembly, so that the stator assembly is located inside the rotor assembly, forming an outer rotor structure. The rotor punching 210 has a circular cross-section. The positioning holes 2101 are provided on the outer wall of the rotor punching 210. When the rotor core 200 is installed, the positioning ribs 1101 engage with the positioning grooves 201 to limit the circumferential rotation of the rotor punching 210.

[0035] In some embodiments, an interference fit is employed between the locating rib 1101 and the locating groove 201. The interference fit of the locating rib 1101 and the locating groove 201 generates elastic pressure between the surfaces of the parts after assembly, thereby achieving a secure connection. The interference fit has a simple structure, good coaxiality, and can withstand large axial forces, torques, and dynamic loads. The interference fit achieves a secure connection between the locating groove 201 and the locating rib 1101, resulting in better coaxiality between the two, reducing circumferential assembly angle errors between the two, reducing assembly difficulty, and improving the reliability and stability of the device.

[0036] In some other embodiments, the positioning groove 201 and the positioning rib 1101 can also be connected and fixed in other ways, such as using a transition fit between the two, and using a pressure plate above the rotor core 200 to connect with the rotor shell 100, to press the rotor punching 210, limit the circumferential rotation of the positioning rib 1101, and also limit the axial movement of the positioning rib 1101, so that the connection between the rotor shell 100 and the rotor core 200 is more firmly, thereby improving the reliability and stability of the device.

[0037] In some embodiments, the rotor core 200 further includes a plurality of magnets 220 , and a plurality of magnet slots 202 are provided on the rotor core 200 . The magnets 220 are installed in the magnet slots 202 , and two magnet slots 202 form a magnet slot group 203 . The number of positioning slots 201 is a common divisor of the number of magnet slot groups 203 ; the positioning slot 201 is located in the middle of two magnet slots 202 in a magnet slot group 203 , or the positioning slot 201 is located between two adjacent magnet slot groups 203 .

[0038] In this embodiment, as shown in Figure 3, the magnetic steel slot 202 is a blind hole, the magnetic steel 220 is installed in the magnetic steel slot 202, and the positioning slots 201 are evenly distributed. By setting the number of positioning slots 201 to a common divisor of the number of magnetic steel slot groups 203, since the positioning slots 201 and the positioning ribs 1101 are one-to-one corresponding, the number of positioning ribs 1101 is also a common divisor of the number of magnetic steel slot groups 203. The number of magnetic steel slot groups 203 can divide the number of positioning ribs 1101, so that the magnetic steel 220 in the magnetic steel slot group 203 (that is, the pole pairs of the rotor assembly) can be evenly distributed between two adjacent positioning ribs 1101, so that the positioning ribs 1101 will not affect the magnetic lines of force of the magnetic steel 220 in the magnetic steel slot group 203. Optimally, the number of positioning slots 201 is the greatest common divisor of the number of magnetic steel slot groups 203 , that is, the number of positioning ribs 1101 is the same as the number of magnetic steel slot groups 203 , which facilitates uniform distribution between the pole pairs of the rotor assembly and the positioning ribs 1101 .

[0039] In some embodiments, as shown in FIG3 , there are 16 magnetic steel slot groups 203 and 16 positioning slots 201 . The positioning slot 201 is located between two magnetic steel slots 202 of the magnetic steel slot group 203 . A magnet 220 is inserted into the magnetic steel slot 202 to ensure that after the positioning rib 1101 is inserted into the positioning slot 201 , the positioning rib 1101 will not interfere with the magnetic lines of force generated by the magnet 220 , thereby ensuring the stability and reliability of the rotor.

[0040] In other embodiments, there are 16 magnetic steel slot groups 203 and 8 positioning slots 201. The positioning slot 201 is located between two adjacent magnetic steel slot groups 203. The magnetic steel slot group 203 includes two magnetic steel slots 202. Magnets 220 are inserted into the magnetic steel slots 202 to ensure that after the positioning rib 1101 is inserted into the positioning slot 201, the positioning rib 1101 will not interfere with the magnetic lines of force generated by the magnet 220, thereby ensuring the stability and reliability of the rotor.

[0041] In some embodiments, the inner end surface 120 of the rotor housing 100 is radially provided with a number of reinforcing ribs 1201, the extension lines of which intersect with the extension lines of the positioning ribs 1101. By providing the radial reinforcing ribs 1201 on the inner end surface 120 of the rotor housing 100, the inner end surface 120 of the rotor housing 100 is strengthened, further improving the overall strength of the rotor housing 100. During operation, the reinforcing ribs 1201 rotate with the rotor, thereby accelerating air flow within the motor and cooling its internal components. The extension lines of the reinforcing ribs 1201 intersect with the extension lines of the positioning ribs 1101, preventing interference with the magnetic field lines generated by the magnets 220 and ensuring the stability and reliability of the rotor.

[0042] The working principle of the rotor assembly is as follows: the inner side wall 110 of the rotor housing 100 is provided with a number of positioning ribs 1101 along the axial direction, and the outer wall of the rotor core 200 is provided with positioning grooves 201 corresponding to the positioning ribs 1101 along the axial direction. The rotor core 200 is placed in the rotor housing 100, and after the positioning grooves 201 are plugged into the positioning ribs 1101 and the bottom surface of the rotor core 200 is in contact with the bottom surface of the rotor housing 100, the rotor core 200 and the rotor housing 100 are fixedly connected and mutually limited in the circumferential direction. Compared with the prior art method of aligning first and then fixing with positioning pins, there will be no situation where the rotor cannot be fixed due to circumferential assembly angle error. The assembly process is simple, the assembly time is reduced, and there is no need to use limit pins, the number of parts is reduced, the structure of the rotor assembly is simplified, and the cost of the rotor assembly is reduced.

[0043] In a second embodiment of the present application, there is provided a method for assembling the rotor assembly according to the first aspect, comprising the following steps:

[0044] Step S1: stack multiple rotor blanks and punch them out as a whole to obtain multiple rotor punching sheets 210.

[0045] Step S2: installing the plurality of rotor punchings 210 in the rotor housing 100 with the two adjacent rotor punchings 210 rotated by a preset angle.

[0046] The assembly method of the rotor assembly proposed in this embodiment is to punch out each rotor punching sheet 210 as a whole, and install multiple rotor punching sheets 210 in the rotor housing 100 with two adjacent rotor punching sheets 210 rotated by a preset angle. The overall punching results in the same shape error of each rotor punching sheet 210 at the same angle. By rotating a certain angle, the processing error can be evenly distributed, thereby effectively improving the dynamic balance level of the rotor. This error is mainly uneven mass distribution, but is not limited to uneven mass distribution.

[0047] In some embodiments, in step S2, the step of installing the plurality of rotor punchings 210 in the rotor housing 100 with two adjacent rotor punchings 210 rotated by a preset angle specifically includes:

[0048] Rotating at least some of the rotor punchings 210 by a preset angle so that any two adjacent rotor punchings 210 are staggered by the preset angle, and the positioning holes 2101 on each rotor punching 210 are aligned to form the positioning grooves 201; for example, the rotor punchings 210 of the previous layer of rotor punchings 210 can be rotated clockwise by a preset angle, and the rotor punchings 210 of the next layer of rotor punchings 210 can be rotated counterclockwise by a preset angle, so that any two adjacent rotor punchings 210 are staggered by the preset angle;

[0049] Align the positioning grooves 201 of the plurality of rotor punchings 210 with the positioning ribs 1101 , and move the plurality of rotor punchings 210 relative to the rotor housing 100 so that the positioning ribs 1101 are inserted into the positioning grooves 201 until the plurality of rotor punchings 210 are integrally installed in the rotor housing 100 .

[0050] In this embodiment, during the assembly process, after the integral punching obtains multiple rotor punchings 210, the adjacent rotor punchings 210 can be rotated by a preset angle. The integral punching results in the same shape error of each rotor punching 210 at the same angle. By rotating a certain angle, the processing error can be evenly distributed, thereby effectively improving the dynamic balance level of the rotor. The adjacent rotor punchings 210 are connected and fixed, so that the multiple rotor punchings 210 are pre-assembled into a whole. The positioning holes 2101 on each layer of rotor punchings 210 are aligned to form positioning grooves 201. The whole is then placed into the rotor housing 100. The positioning ribs 1101 are plugged into the positioning grooves 201 to achieve the assembly of the rotor core 200 and the rotor housing 100. This assembly method is relatively fast and can improve assembly efficiency. The connection and fixation between the adjacent rotor punchings 210 can be achieved by adhesive, or by inserting a positioning mold of the same size as the positioning ribs 1101 into the positioning grooves 201. During the assembly of the rotor punching 210 assembly, the positioning mold is pushed out by the positioning ribs 1101.

[0051] In other embodiments, in step S2, the step of installing the plurality of rotor punchings 210 in the rotor housing 100 with two adjacent rotor punchings 210 rotated by a preset angle specifically includes: rotating the rotor punching 210 by a preset angle relative to the previous rotor punching 210, and fitting the positioning holes 2101 of the rotor punchings 210 onto the positioning ribs 1101, so that each rotor punching 210 is sequentially installed in the rotor housing 100. By installing the rotor punchings 210 one by one in the rotor housing, the dimensional error between the positioning slots 201 and the positioning ribs 1101 can be eliminated. When the current rotor punching 210 is rotated by a preset angle relative to the previous rotor punching 210, the overall punching results in the same shape error of each rotor punching 210 at the same angle. By rotating the rotor punching 210 by a certain angle, the machining error can be evenly distributed, thereby effectively improving the dynamic balance level of the rotor.

[0052] In some embodiments, the preset angle is an integer multiple of the angle between two adjacent positioning ribs 1101. A number of positioning ribs 1101 are evenly distributed around the inner circumference of the inner sidewall 110 of the rotor housing 100, with the angle between two adjacent positioning ribs 1101 being the same. During installation, two adjacent layers of rotor punchings 210 are staggered by a preset angle, which is an integer multiple of the angle between two adjacent positioning ribs 1101. This allows the positioning holes 2101 on two adjacent rotor punchings 210 to align, improving the stability and reliability of the device. For example, the number of positioning ribs 1101 is n, and the n positioning ribs 1101 are evenly distributed on the circumference of the inner side wall 110 of the rotor housing 100. The angle K between two adjacent positioning ribs 1101 is 360° / n. Before two adjacent layers of rotor punchings 210 are placed in the rotor housing 100, they are staggered by a preset angle. The preset angle is an integer multiple of K, which can eliminate the defect of uneven mass distribution of the rotor punchings 210 during the punching process, thereby effectively improving the dynamic balance level of the rotor.

[0053] A third embodiment of the present application provides a hub motor, comprising a stator assembly and the rotor assembly of the first aspect, wherein the stator assembly is installed inside the rotor core 200 .

[0054] In a hub motor provided by an embodiment of the present application, during the assembly of the rotor assembly, the circumferential positioning and fixation between the rotor housing 100 and the rotor core 200 can be achieved by directly inserting the positioning rib 1101 into the positioning groove 201. Compared with the prior art method of first aligning and then fixing with a positioning pin, there will be no situation where the rotor cannot be fixed due to circumferential assembly angle error, and the assembly process is simple, which reduces the assembly time. In addition, the positioning rib 1101 can cooperate with the positioning groove 201 while retaining its original strength-increasing function to achieve assembly of the rotor housing 100 and the rotor core 200. There is no need to use a limit pin, which reduces the number of parts, simplifies the structure of the rotor assembly, and reduces the cost of the rotor assembly.

[0055] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a feature may include the first feature being in direct contact with the feature, or may include the first feature being in contact with the feature through another feature between them. Moreover, a first feature being "above," "above," and "above" a feature includes the first feature being directly above or obliquely above the feature, or may simply mean that the first feature is higher in level than the feature. A first feature being "below," "below," and "below" a feature includes the first feature being directly below or obliquely below the feature, or may simply mean that the first feature is lower in level than the feature.

[0056] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0057] In this application, unless otherwise specified or limited, the terms "connect," "fix," etc. should be understood broadly. For example, "fix" can mean fixed connection, detachable connection, or integration; it can mean mechanical connection or electrical connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0058] In addition, the terms "first," "second," and so on, used in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0059] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A rotor assembly, characterized in that: include: A rotor housing, wherein the inner side wall of the rotor housing is provided with a plurality of positioning ribs along the axial direction; The rotor core comprises a plurality of rotor punchings stacked in the axial direction, and the outer wall of the rotor core is provided with positioning grooves corresponding to the positioning ribs in the axial direction, and the positioning grooves are configured to be inserted into the positioning ribs.

2. The rotor assembly according to claim 1, characterized in that: A plurality of positioning holes are arranged on the outer wall of the rotor punching, and the positioning holes of a plurality of rotor punchings are aligned to form the positioning groove. A through hole configured to install the stator assembly is arranged in the middle of the rotor punching.

3. The rotor assembly according to claim 1, characterized in that: The positioning rib is interference fit with the positioning groove.

4. The rotor assembly according to claim 1, characterized in that: The rotor core also includes a plurality of magnetic steels, a plurality of magnetic steel slots are arranged on the rotor core, the magnetic steels are installed in the magnetic steel slots, two of the magnetic steel slots form a magnetic steel slot group, the number of the positioning slots is a common divisor of the number of the magnetic steel slot groups; the positioning slot is located in the middle of two of the magnetic steel slots in the magnetic steel slot group, or the positioning slot is located between two adjacent magnetic steel slot groups.

5. The rotor assembly according to claim 2, characterized in that: The rotor core also includes a plurality of magnetic steels, a plurality of magnetic steel slots are arranged on the rotor core, the magnetic steels are installed in the magnetic steel slots, two of the magnetic steel slots form a magnetic steel slot group, the number of the positioning slots is a common divisor of the number of the magnetic steel slot groups; the positioning slot is located in the middle of two of the magnetic steel slots in the magnetic steel slot group, or the positioning slot is located between two adjacent magnetic steel slot groups.

6. The rotor assembly according to claim 3, characterized in that: The rotor core also includes a plurality of magnetic steels, a plurality of magnetic steel slots are arranged on the rotor core, the magnetic steels are installed in the magnetic steel slots, two of the magnetic steel slots form a magnetic steel slot group, the number of the positioning slots is a common divisor of the number of the magnetic steel slot groups; the positioning slot is located in the middle of two of the magnetic steel slots in the magnetic steel slot group, or the positioning slot is located between two adjacent magnetic steel slot groups.

7. The rotor assembly according to claim 1, characterized in that: The inner end surface of the rotor housing is provided with a plurality of reinforcing ribs in the radial direction; the extension lines of the reinforcing ribs intersect with the extension lines of the positioning ribs.

8. The rotor assembly according to claim 2, characterized in that: The inner end surface of the rotor housing is provided with a plurality of reinforcing ribs in the radial direction; the extension lines of the reinforcing ribs intersect with the extension lines of the positioning ribs.

9. The rotor assembly according to claim 3, characterized in that: The inner end surface of the rotor housing is provided with a plurality of reinforcing ribs in the radial direction; the extension lines of the reinforcing ribs intersect with the extension lines of the positioning ribs.

10. An assembly method for a rotor assembly according to any one of claims 1 to 9, characterized in that: The steps include: Stacking a plurality of rotor blanks and punching them as a whole to obtain a plurality of rotor punching sheets; A plurality of rotor punching sheets are installed in the rotor housing in a posture where two adjacent rotor punching sheets are rotated by a preset angle.

11. The method for assembling a rotor assembly according to claim 10, characterized in that: The step of installing the plurality of rotor punchings in the rotor housing with two adjacent rotor punchings rotated by a preset angle specifically includes: Rotating at least part of the rotor punchings by a preset angle so that any two adjacent rotor punchings are staggered by a preset angle and the positioning holes on the rotor punchings are aligned to form the positioning grooves; The positioning grooves of the plurality of rotor punchings are aligned with the positioning ribs, and the plurality of rotor punchings and the rotor housing are relatively moved so that the positioning ribs are inserted into the positioning grooves until the plurality of rotor punchings are integrally installed in the rotor housing.

12. The method for assembling a rotor assembly according to claim 10, characterized in that: The method of installing the plurality of rotor punchings in the rotor housing with two adjacent rotor punchings rotated by a preset angle specifically includes: rotating the rotor punching relative to the previous rotor punching by a preset angle, and sleeve the positioning holes of the rotor punching on the positioning ribs, so that each rotor punching is installed in the rotor housing in sequence.

13. The method for assembling a rotor assembly according to claim 11 or 12, characterized in that: The preset angle is an integral multiple of the included angle between two adjacent positioning ribs.

14. A hub motor, characterized in that: It comprises a stator assembly and the rotor assembly according to any one of claims 1 to 9, wherein the stator assembly is installed inside the rotor core.

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