Rotor assembly, method for manufacturing rotor assembly, and motor

Abstract

A rotor assembly, having a circumferentially symmetrical structure, and comprising a shaft (1), a main magnetic ring (2), a Hall magnetic ring (3), and an injection molding structure (4), wherein the shaft (1) and the injection molding structure (4) are fixed to each other, and by means of a slot-key structure, the main magnetic ring (2) and the Hall magnetic ring (3) are fixedly connected to the shaft (1) by means of the injection molding structure in a spaced manner. The rotor assembly of the present application has a simple structure, a small number of parts and low costs, and involves simple assembly steps, thereby facilitating mass production. Moreover, the rotor assembly of the present application has high production stability and light rotor weight, thereby facilitating lightweight design. The present application further relates to a method for manufacturing a rotor assembly and a motor.

Description

Rotor assembly, method for manufacturing rotor assembly, and electric motor

[0001] This application is based on and claims priority to the Chinese patent application with Chinese application number 202311615203.7 and application date November 29, 2023, the Chinese patent application with Chinese application number 202323238389.7 and application date November 29, 2023, the Chinese patent application with Chinese application number 202311673387.2 and application date December 7, 2023, and the Chinese patent application with Chinese application number 202323334102.0 and application date December 7, 2023. The disclosed contents of the above Chinese patent applications are hereby introduced as a whole into this application. Technical Field

[0002] The present application relates to the field of electric motors, and more particularly to a rotor assembly, a method for manufacturing a rotor assembly, and an electric motor. Background Art

[0003] Currently, the rotor assembly of most brushless motors on the market uses silicon steel laminations as the core, sintered NdFeB magnets as permanent magnets, and is assembled using glue. This rotor assembly uses a large amount of metal and rare earth materials, which is very expensive. The glue bonding process has a long cycle time and is difficult to ensure process consistency. Furthermore, dynamic balancing requires counterweights after assembly. The large amount of metal in the rotor assembly hinders lightweight design, increases the rotor's moment of inertia, and increases the motor's response time. Summary of the Invention

[0004] The object of the present application is to provide a rotor assembly, a method for manufacturing a rotor assembly, and an electric machine, which can overcome at least one disadvantage of the prior art.

[0005] In particular, in order to solve the problems such as high cost in the above-mentioned prior art, the first aspect of the present application provides a rotor assembly.

[0006] According to the rotor assembly of the present application, it has a circumferentially symmetrical structure, including a shaft, a main magnetic ring, a Hall magnetic ring and an injection molding structure, wherein the shaft and the injection molding structure are fixed to each other, and the main magnetic ring and the Hall magnetic ring are fixedly connected to the shaft through the injection molding structure by means of a slot key structure and are spaced apart from each other.

[0007] In some embodiments, the shaft has knurling, and the injection-molded structure is coupled to the shaft via the knurling.

[0008] In some embodiments, the shaft is an axially extending flat metal shaft.

[0009] In some embodiments, the shaft is configured with protrusions and / or recesses on an outer circumferential surface, and the shaft is cooperatively connected to the injection molding structure via the protrusions and / or recesses.

[0010] In some embodiments, the magnetic fields of the main magnetic ring and the Hall magnetic ring are circumferentially aligned.

[0011] In some embodiments, the main magnetic ring and the Hall magnetic ring respectively have circumferentially symmetrically designed sink grooves, the injection molding structure has a key structure, and the sink grooves are cooperatively connected with the key structure.

[0012] In some embodiments, the key structures are circumferentially aligned.

[0013] In some embodiments, the sink is a square sink, which may be understood as having a substantially rectangular or square cross section.

[0014] In some embodiments, the main magnetic ring and the Hall magnetic ring each have an inner ring structure, and the recessed grooves are provided on two axial end faces of the inner ring structure.

[0015] In some embodiments, the main magnetic ring and the Hall magnetic ring respectively have an outer ring structure integrally formed with the inner ring structure, wherein the outer ring structure is located outside the inner ring structure and extends beyond two axial end faces of the inner ring structure.

[0016] In some embodiments, the injection molded structure includes an integrally formed main body and two convex ring structures, wherein the main body is wrapped around the outside of the shaft and is connected to the shaft in a mating manner, in particular through a knurling mating manner, and the convex ring structures extend radially from the main body to connect the main magnetic ring and the Hall magnetic ring.

[0017] In some embodiments, the raised ring structures each have two flanges, the key structures extend from the two flanges toward each other, and a portion of the outer ring structure that extends beyond the inner ring structure cooperates with the flanges.

[0018] In some embodiments, the injection molded structure is provided by polyphenylene sulfide.

[0019] The second aspect of the present application relates to a method for manufacturing the rotor assembly according to the first aspect of the present application. In the method, the shaft, the main magnetic ring, and the Hall magnetic ring are connected together using an injection molding structure.

[0020] In some embodiments, the shaft, the main magnetic ring, and the Hall magnetic ring are connected together using an injection molding structure through an injection molding process, particularly an insert injection molding process.

[0021] The third aspect of the present application relates to an electric motor, which includes the rotor assembly described in the first aspect of the present application.

[0022] In some embodiments, the electric motor is a motor for a seat, in particular a seat of a vehicle.

[0023] The rotor assembly of this application boasts a simple structure, a small number of parts, low cost, and simplified assembly steps, making it suitable for mass production. Furthermore, the rotor assembly of this application offers high production stability and a lightweight rotor, facilitating lightweight design. Furthermore, the rotor assembly of this application boasts a high level of dynamic balancing through integral injection molding, which improves motor noise performance and enhances the competitiveness of seat motors.

[0024] The details, embodiments and advantages described above in conjunction with the rotor assembly of the first aspect of the present application are similarly applicable to the method for manufacturing the rotor assembly according to the second aspect of the present application and the electric machine according to the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic assembly diagram of a rotor assembly according to an embodiment of the present application.

[0026] FIG. 2 is a schematic cross-sectional view of the rotor assembly of FIG. 1 .

[0027] FIG3 is a schematic structural diagram of the shaft of FIG1 .

[0028] FIG. 4 is a schematic diagram looking toward the end side of the shaft of FIG. 3 .

[0029] FIG. 5 is a schematic cross-sectional view of the shaft of FIG. 3 along the section line AA in FIG. 2 .

[0030] FIG6 is a schematic structural diagram of the main magnetic ring of FIG1 .

[0031] FIG7 is a schematic structural diagram of the Hall magnetic ring in FIG1 .

[0032] FIG8 is a schematic structural diagram of the injection molding structure of FIG1 .

[0033] FIG9 is a schematic structural diagram of a shaft of a rotor assembly according to another embodiment of the present application.

[0034] FIG10 is a schematic structural diagram of a shaft of a rotor assembly according to yet another embodiment of the present application. DETAILED DESCRIPTION

[0035] The following exemplary embodiments of the present application are given in conjunction with the accompanying drawings and described in detail. Note that the specific embodiments described below are only exemplary illustrations of the technical solutions of the present application and do not constitute a limitation on the scope of protection of the present application as defined by the claims.

[0036] As shown in Figures 1 and 2, the rotor assembly according to an embodiment of the present application has a circumferentially symmetrical structure. The circumferentially symmetrical structure of the rotor assembly can be understood in particular as that the rotor assembly is rotationally symmetrical around its axis of rotation. Specifically, the rotor assembly includes a shaft 1, a main magnetic ring 2, a Hall magnetic ring 3 and an injection molding structure 4. Among them, the main magnetic ring 2 and the Hall magnetic ring 3 are spaced apart from each other (axially) and fixedly connected to the shaft 1 by the injection molding structure 4. That is to say, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 are fixedly connected to each other by means of the injection molding structure 4, and can in particular form a one-piece rotor assembly, as shown in the lower half of Figure 1 and Figure 2.

[0037] When manufacturing the rotor assembly, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 can be pre-manufactured or provided independently of each other. Subsequently, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 can be connected together using the injection molding structure 4. In some exemplary specific production processes, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 can be connected together using the injection molding structure 4 by injection molding, in particular by an insert injection molding process. Here, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 can be placed in the mold as an insert, for example. While manufacturing the injection molding structure 4 by the injection molding process, the material of the injection molding structure 4 can form a form-locking connection with the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3, respectively, so that the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 are fixed to each other by means of the injection molding structure 4 and form a one-piece rotor assembly. That is to say, the shaft 1 can be fixed to the plastic of the injection molding structure 4, especially connected to each other in a form-locked manner, the main magnetic ring 2 can be fixed to the plastic of the injection molding structure 4, especially connected to each other in a form-locked manner, and the Hall magnetic ring 3 can be fixed to the plastic of the injection molding structure 4, especially connected to each other in a form-locked manner. The overall structure of the rotor assembly thus produced is stable. In this way, the production process of the rotor assembly according to the present application has only one injection molding step, the production cycle is fast, and the process consistency is high. In the present application, the shaft 1, the main magnetic ring 2 and the Hall magnetic ring 3 can be fixed to each other and simultaneously made into a rotor assembly in only one production process with the help of the injection molding structure 4, which can advantageously omit processes such as gluing, thereby shortening the process cycle time while improving process consistency.

[0038] In particular, according to the circumferentially symmetrical structure of the rotor assembly of the present application, the dynamic balance of the rotor can be ensured, and there is no need for subsequent correction of the dynamic balance work, and there is no need to add counterweights to correct the dynamic balance. The production cycle is fast and the process cost is low. Moreover, according to the rotor assembly of the present application, the dual magnetic ring (main magnetic ring 2 and Hall magnetic ring 3) structure is applicable to both inductive and inductive brushless motors. Specifically, the magnetic fields of the main magnetic ring 2 and the Hall magnetic ring 3 can be circumferentially aligned to meet the envelope requirements of the motor design. Generally speaking, the main magnetic ring 2 and the Hall magnetic ring 3 can have N poles and S poles that alternate with each other in the circumferential direction, for example. The circumferential alignment of the magnetic fields of the main magnetic ring 2 and the Hall magnetic ring 3 can be understood as the N poles of the main magnetic ring 2 and the Hall magnetic ring 3 having the same angular position and therefore aligned with each other in the axial direction, and the S poles of the main magnetic ring 2 and the Hall magnetic ring 3 also having the same angular position and therefore aligned with each other in the axial direction. Advantageously, the geometric bisectors of the axial extensions of the poles of the main magnetic ring 2 and the geometric bisectors of the axial extensions of the poles of the Hall magnetic ring 3 can be aligned with each other in the axial direction.

[0039] Compared with the existing technology of silicon steel laminated core, the rotor assembly according to the present application has a small number of parts, and a plastic injection molding structure 4 can be used to replace, for example, the silicon steel laminates in the prior art. It is light in weight and low in cost, which is conducive to the lightweight design of the motor and helps to optimize the motor response time. Specifically, in some embodiments, the injection molding structure 4 can be provided by polyphenylene sulfide (PPS). Generally speaking, the materials of the main magnetic ring 2 and the Hall magnetic ring 3 may be relatively brittle, which is prone to bumps and cracking. Polyphenylene sulfide has relatively stable physical and chemical properties, and the mechanical stability provided by it can advantageously avoid the problem that the plastic deforms under high temperature, low temperature, humidity, etc., such as thermal expansion and contraction, which produces undesirable stress on the magnetic ring, i.e., the main magnetic ring 2 and the Hall magnetic ring 3, and causes the magnetic ring to crack. This ensures the functional stability of the rotor assembly and the motor including the rotor assembly under various environmental conditions.

[0040] As shown in Figure 3, the shaft 1 can be a flat shaft extending axially. Compared with a stepped shaft, the flat shaft of the present application has a simpler shaft structure, is more lightweight, and has a low manufacturing process and cost. Specifically, the shaft 1 can be a metal shaft and have a knurling 11. The knurling 11 can be located on the outer peripheral surface of the shaft 1, in particular, on the axial section of the shaft 1 corresponding to the injection molding structure 4. The injection molding structure 4 can be connected to the shaft 1 through the knurling 11. During the injection molding process, the material of the injection molding structure 4 can flow into and fill the knurling 11 of the shaft 1, and after cooling, a filling fit is achieved between the plastic of the injection molding structure 4 and the knurling 11 for axial and circumferential limiting. In this way, the structure of the knurling 11 is tightly fastened and adhered to the plastic of the injection molding structure 4, providing axial holding force and circumferential holding force.

[0041] In particular, in some embodiments, the knurling 11 can have a circumferentially or rotationally symmetrical design. This helps reduce dynamic imbalance. Compared to existing threaded connections, which can increase dynamic imbalance, the rotor assembly according to this embodiment can achieve greater operational stability.

[0042] In the embodiment shown in Figure 3, the knurling 11 may be a 10 mm long reticulated knurling. In other embodiments, the knurling 11 may also be a straight knurling, a diagonal knurling, a left-right knurling, a cross knurling, a diamond knurling, a dot knurling, a wave knurling, etc.

[0043] Naturally, the axial length, position and type of the knurling 11 can be selected as required. For example, the shaft 1 can also have a plurality of knurling sections axially spaced apart from each other or axially adjacent to each other, and these knurling sections can have the same type or different types of knurling.

[0044] Alternatively or additionally, in some embodiments, as shown in FIG9 , the shaft 1 may be configured with a protrusion 18 on its outer circumference, particularly in the section corresponding to the injection molded structure 4. The shaft 1 may be connected to the injection molded structure 4 in a form-locked manner by means of the protrusion 18. In FIG9 , the protrusion 18 may be a circumferential flange. Knurling 11 may also be provided on the outer circumference of the flange to further enhance the engagement force between the shaft 1 and the injection molded structure 4. In other embodiments, the protrusion 18 may have any suitable configuration, such as multiple axially spaced flanges and / or discrete radial protrusions.

[0045] Alternatively or additionally, in some embodiments, as shown in FIG10 , the shaft 1 may be configured with a recessed portion 19 on its outer circumference, particularly in the section corresponding to the injection molded structure 4. The shaft 1 can be positively connected to the injection molded structure 4 by means of this recessed portion 19. In FIG10 , the recessed portion 19 may be a flattened portion that extends partially in the axial direction, particularly in the section configured with the knurling 11. In other embodiments, the recessed portion 19 may have any suitable configuration, such as an annular groove, an axial groove, a hole, etc.

[0046] Furthermore, as shown in Figures 3 to 5 , the shaft 1 may have a counterbore 12 for external connection, thereby outputting torque. In this embodiment, the counterbore 12 may be a square hole. Referring to Figures 4 and 5 , the counterbore 12 may have a cylindrical basic shape 13 when viewed in cross-section. As shown in Figure 2 , this cylindrical basic shape 13 may extend rightward from the open end 14 of the shaft 1 to the end of the counterbore 12 within the shaft 1. In other words, the cylindrical basic shape 13 may extend substantially along the entire length of the counterbore. In addition to the cylindrical basic shape 13, in a partial axial section of the counterbore 12 facing the open end 14, the counterbore 12 may have a square hole portion 15 in cross-section (see Figures 4 and 5 ). The geometric centers of the cylindrical basic shape 13 and the square hole portion 15 may coincide. This geometric center also defines the axis of rotation and the circumferential or rotational symmetry axis of the shaft 1 and the entire rotor assembly. It can be seen that the side length of the square hole portion 15 can be smaller than the diameter of the cylindrical basic shape 13, so that a partial arc length 16 of the cylindrical basic shape 13 can still be reflected on the four sides of the square hole portion 15. In addition, the square hole portion 15 can have chamfers or bevels 17 at each of the four corners.

[0047] It should be understood that the counterbore 12 can have any suitable shape. Other shapes such as hexagonal holes are also possible, but the processing difficulty of the corresponding shaft 1 and the connecting shaft matched with the shaft 1 may make it more expensive.

[0048] As shown in Figure 6, the main magnetic ring 2 can include an integrally formed first inner ring structure 21 and a first outer ring structure 22. The first outer ring structure 22 is located outside the first inner ring structure 21 and extends beyond both axial end faces of the first inner ring structure 21. Specifically, each axial end face of the first inner ring structure 21 can have four first recesses 211. The injection molding structure 4 can be coupled to the main magnetic ring 2 via the first recesses 211, achieving circumferential and axial position retention. During the injection molding process, the plastic of the injection molding structure 4 fills and fits with the first recesses 211, providing axial and circumferential position retention. This ensures that the first recesses 211 and the plastic of the injection molding structure 4 are tightly interlocked and bonded, providing both axial and circumferential retention. In particular, each first recess 211 can have a circumferentially or rotationally symmetrical design, which helps reduce dynamic unbalance. In this embodiment, the first recesses 211 can be square, providing a maximum torque of 0.6 Nm. Square recesses are the simplest and most cost-effective to manufacture.

[0049] As shown in Figure 7, the Hall effect magnet 3 may include an integrally formed second inner ring structure 31 and second outer ring structure 32. The second outer ring structure 32 is located outside the second inner ring structure 31 and extends beyond both axial end faces of the second inner ring structure 31. Specifically, each axial end face of the second inner ring structure 31 may have four second recessed grooves 311. The injection molding structure 4 can be coupled to the Hall effect magnet 3 via the second recessed grooves 311, achieving circumferential and axial position retention. During the injection molding process, the plastic of the injection molding structure 4 fills and fits with the second recessed grooves 311, providing axial and circumferential position retention. This allows the second recessed grooves 311 to tightly interlock with the plastic of the injection molding structure 4, providing both axial and circumferential retention. In particular, each second recessed groove 311 may have a circumferentially or rotationally symmetrical design, which helps reduce dynamic imbalance. In this embodiment, the second recessed grooves 311 may be square, providing a maximum torque of 0.6 Nm. Square grooves are simpler to manufacture and process, and offer the lowest cost.

[0050] Advantageously, the number of the first recessed grooves 211 of the main magnetic ring 2 can be the same as the number of the second recessed grooves 311 of the Hall magnetic ring 3. This can reduce the dynamic unbalance.

[0051] As shown in FIG8 , the injection molded structure 4 may include an integrally formed main body 41, a first flange structure 42, and a second flange structure 43. In the completed rotor assembly, the main body 41 wraps around the exterior of the shaft 1 and may be matingly connected to the shaft 1, for example, via knurling 11 (see FIG3 ). The first flange structure 42 radially extends from a first position of the main body 41 to connect to the main magnetic ring 2 (see FIG2 ), and the second flange structure 43 radially extends from a second position of the main body 41 to connect to the Hall magnetic ring 3 (see FIG2 ).

[0052] As shown in Figure 8 , the first protruding ring structure 42 may include a third inner ring structure 421, connecting ribs 422, and a first flange 423. The inner side of the third inner ring structure 421 may be fixedly connected to the main body 41 via, for example, four circumferentially spaced connecting ribs 422. The two axial end surfaces of the outer side of the third inner ring structure 421 may each extend radially outward to form a first flange 423. The two first flanges 423 may have first key structures 424 extending toward each other, with eight first key structures 424 in total. Referring to Figure 6 , in the completed rotor assembly, the first inner ring structure 21 of the main magnetic ring 2 mates with the third inner ring structure 421, the portion of the first outer ring structure 22 extending beyond the first inner ring structure 21 mates with the first flange 423, and the first recess 211 mates with the first key structures 424. In this embodiment, the connecting ribs 422 and the first key structures 424 are circumferentially aligned. That is, the connecting rib 422 and the first key structure 424 (particularly the midpoints of their respective circumferential lengths) have the same angular position and are therefore aligned with each other in the axial direction, thereby reducing dynamic unbalance and improving the operational stability of the rotor.

[0053] As shown in Figure 8 , the second flange structure 43 may include a fourth inner ring structure 431 and a second flange 432. The inner side of the fourth inner ring structure 431 may be directly fixedly connected to the main body 41. The two axial end surfaces of the outer side of the fourth inner ring structure 431 may each extend radially outward to form a second flange 432. The two second flanges 432 may have second key structures 433 extending toward each other, with eight second key structures 433 in total. In conjunction with Figure 7 , in the completed rotor assembly, the second inner ring structure 31 of the Hall magnet 3 mates with the fourth inner ring structure 431, the portion of the second outer ring structure 32 extending beyond the second inner ring structure 31 mates with the second flange 432, and the second recess 311 mates with the second key structures 433. In this embodiment, the first key structure 424 and the second key structure 433 are circumferentially aligned. That is, the first key structure 424 and the second key structure 433 (particularly the midpoints or geometric bisectors of the circumferential lengths of the first key structure 424 and the second key structure 433) have the same angular position and are therefore aligned with each other in the axial direction. This can reduce dynamic unbalance and improve the operational stability of the rotor.

[0054] In addition, the present application also relates to an electric motor comprising the rotor assembly described above, which can be used for a seat, in particular a seat of a vehicle.

[0055] It should be noted that the terms used herein are for the purpose of describing specific aspects only and are not intended to limit the disclosure. As used herein, the singular forms "a" and "the one" shall include the plural forms unless the context clearly indicates otherwise. It will be understood that the terms "include" and "comprise" and other similar terms, when used in the application documents, specify the presence of the stated operations, elements and / or parts, and do not exclude the presence or addition of one or more other operations, elements, parts and / or combinations thereof. As used herein, the term "and / or" includes all arbitrary combinations of one or more related enumerated items. In the description of the drawings, similar reference numerals always represent similar elements.

[0056] The thickness of the elements in the accompanying drawings can be exaggerated for the sake of clarity. It will also be understood that if an element is referred to as being on, coupled to, or connected to another element, then the element can be formed directly on, coupled to, or connected to the other element, or one or more intervening elements can be present between them. On the contrary, if the expressions "directly on...", "directly coupled to...", and "directly connected to..." are used herein, then there is no intervening element. Other words used to illustrate the relationship between elements should be interpreted similarly, such as "between..." and "directly between...", "attached to," and "directly attached to," "adjacent to," and "directly adjacent to," etc.

[0057] Terms such as "top," "bottom," "above," "below," "upper," "below," etc., are used herein to describe the relationship of one element, layer, or region to another element, layer, or region as illustrated in the figures. It will be understood that these terms are intended to encompass orientations of the device in addition to the orientation depicted in the figures.

[0058] It will be understood that although the terms "first," "second," etc. may be used herein to describe different elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another. Thus, a first element may be referred to as a second element without departing from the teachings of the inventive concept of this application.

[0059] It is also conceivable that all exemplary embodiments disclosed herein can be combined with one another in any desired manner.

[0060] The above description is merely a preferred embodiment of the present application and is not intended to limit the scope of the present application. Various modifications are possible to the above embodiments of the present application. In other words, any simple, equivalent changes and modifications made in accordance with the claims and description of the present application fall within the scope of protection of the claims of the present application. Anything not fully described in this application is conventional technology.

Claims

1. A rotor assembly, characterized in that: The rotor assembly has a circumferentially symmetrical structure, including a shaft, a main magnetic ring, a Hall magnetic ring and an injection molding structure, wherein the shaft and the injection molding structure are fixed to each other, and the main magnetic ring and the Hall magnetic ring are fixedly connected to the shaft through the injection molding structure by means of a slot key structure and are spaced apart from each other.

2. The rotor assembly according to claim 1, characterized in that: The shaft has knurling, and the injection molding structure is connected with the shaft through the knurling.

3. The rotor assembly according to claim 2, characterized in that: The shaft is an axially extending metal flat shaft.

4. The rotor assembly according to claim 1 or 2, characterized in that: The shaft is configured with protrusions and / or recesses on an outer peripheral surface, and the shaft is cooperatively connected with the injection-molded structure via the protrusions and / or recesses.

5. The rotor assembly according to any one of claims 1 to 4, characterized in that: The magnetic fields of the main magnetic ring and the Hall magnetic ring are aligned circumferentially.

6. The rotor assembly according to any one of claims 1 to 5, characterized in that: The main magnetic ring and the Hall magnetic ring are respectively provided with circumferentially symmetrically designed sink grooves, the injection molding structure is provided with a key structure, and the sink grooves are cooperatively connected with the key structure.

7. The rotor assembly according to claim 6, characterized in that: The key structures are aligned in the circumferential direction.

8. The rotor assembly according to claim 6 or 7, characterized in that: The trough is a square trough.

9. The rotor assembly according to any one of claims 6 to 8, characterized in that: The main magnetic ring and the Hall magnetic ring respectively have inner ring structures, and the sink grooves are arranged on two axial end faces of the inner ring structures.

10. The rotor assembly according to claim 9, characterized in that: The main magnetic ring and the Hall magnetic ring respectively have an outer ring structure integrally formed with the inner ring structure, wherein the outer ring structure is located outside the inner ring structure and extends beyond two axial end faces of the inner ring structure.

11. The rotor assembly according to any one of claims 1 to 10, characterized in that: The injection molding structure includes an integrally formed main body and two convex ring structures, wherein the main body is wrapped around the outside of the shaft and is connected to the shaft in a cooperative manner, especially through a knurling cooperation, and the convex ring structures extend radially from the main body to connect the main magnetic ring and the Hall magnetic ring.

12. The rotor assembly according to claim 11, characterized in that: The convex ring structure has two flanges respectively, the key structure extends from the two flanges toward each other, and the part of the outer ring structure exceeding the inner ring structure is matched with the flanges.

13. The rotor assembly according to any one of claims 1 to 12, characterized in that: The injection molded structure is provided by polyphenylene sulfide.

14. A method for manufacturing a rotor assembly according to any one of claims 1 to 13, characterized in that: In the method, the shaft, the main magnetic ring and the Hall magnetic ring are connected together by using an injection molding structure.

15. The method according to claim 14, characterized in that The shaft, the main magnetic ring and the Hall magnetic ring are connected together by an injection molding structure through an injection molding process, in particular, an insert injection molding process.

16. A motor, characterized in that: The electric machine comprises a rotor assembly according to any one of claims 1 to 13.

17. The electric machine according to claim 16, characterized in that The electric motor is an electric motor for a seat, in particular a seat of a vehicle.

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