Rotor assembly and electric machine

Abstract

This invention relates to a rotor assembly for an electric motor, comprising a rotor shaft (1), a rotor lamination assembly (2), and a tensioned fiber sleeve (5) wound around the outer periphery of the rotor lamination assembly (2). The rotor lamination assembly (2) has a groove (23) for accommodating a magnet (3), wherein an adhesive (4) is provided within the groove (23) for securing the magnet (3) within the groove (23). Furthermore, this invention also relates to an electric motor having such a rotor assembly.

Description

Rotor assembly and motor Technical Field

[0001] The present invention relates to the field of vehicle technology, and more specifically, to a motor and rotor assembly for new energy vehicles, wherein the motor is particularly a permanent magnet synchronous motor (PMSM). Background Art

[0002] With the development of electric vehicles, motor design has become increasingly important. The trend in motor design is to accommodate high-speed rotation, enabling use in vehicles with faster acceleration. However, as speeds increase, the rotor laminations are subjected to very high centrifugal forces, leading to deformation and damage. Traditional permanent magnet synchronous motor designs typically require thicker rotor bridges to withstand the very high centrifugal forces at high speeds. When rotor speeds increase above 20,000 rpm, the bridges must be designed to be extremely strong and thick to account for rotor deformation at high speeds. However, thicker bridges can lead to magnetic flux leakage, reducing rotor magnet utilization and overall motor efficiency.

[0003] To address this issue, CN 115917927 A discloses an electric motor comprising a stator and a rotor. The stator is configured to generate a magnetic field and accommodate a rotor within a central opening. The rotor is sized to fit within the central opening. The rotor includes a plurality of magnets and is wrapped around its outer circumference with a fiber sleeve that holds the magnets in the rotor under tension. However, the magnets are subjected to very high stress during the carbon fiber winding process and high-speed rotation. The magnets themselves are brittle materials and are easily broken by external forces. In particular, if the magnets are not fully secured within the rotor laminations, they may collide with the grooves that accommodate them, causing them to break easily.

[0004] Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an improved rotor assembly which can adapt to ultra-high-speed rotation and significantly improve the service life of the magnets and rotor laminations.

[0006] The technical problem is solved by a rotor assembly for an electric motor. The rotor assembly includes a rotor shaft, a rotor lamination group, and a tensioned fiber sleeve wound around the outer periphery of the rotor lamination group. A groove is provided on the rotor lamination group, and an adhesive is filled in the groove. The adhesive is used to fix the magnet in the groove. According to the design scheme of the present invention, the outer layer of the rotor lamination group is wrapped with carbon fiber, and the carbon fiber is wound into a sleeve around the rotor. The high-strength carbon fiber sleeve provides protection for the rotor laminations and magnets. The adhesive is used to fill it into the magnetic groove, which not only acts as an adhesive filler to fix the magnet, but also combines the rotor laminations and magnets into a whole. The magnet is fixed in the groove immovably by the adhesive, which can reduce the stress on the magnet when the motor runs at high speed, creating a sturdy design with better performance.

[0007] According to a preferred embodiment of the present invention, the adhesive is formed by injection molding in the groove. This injection molding method makes the bond between the adhesive and the groove more secure, helps to improve the durability and reliability of the rotor assembly, and the injection molding process is low-cost and easy to implement. It is further preferred that the adhesive covers the axial end face of the rotor lamination stack, that is, the adhesive fills the groove and covers the groove in the axial direction. This covering method ensures a close connection between the magnet and the rotor, reduces possible loosening or falling off, and thus improves the performance and stability of the motor. In addition, the adhesive cannot cover the entire axial end face to avoid stress concentration. This laying on the axial end face can be simply formed by demolding. It is further preferred that the adhesive is a polymer material. The polymer material has excellent adhesion and durability, and can effectively bond the magnet and the rotor lamination stack, thereby providing a reliable fixing effect.

[0008] According to a preferred embodiment of the present invention, the rotor lamination stack is evenly divided circumferentially into multiple magnet placement areas. Within each magnet placement area, three magnets are arranged in a triangular pattern and spaced apart from each other. This triangular arrangement of the magnets creates a stable structure, and the spacing between the magnets provides space for injection molding adhesive, thereby better securing the magnets. Furthermore, preferably, the rotor lamination stack comprises a first component and a second component, wherein the first component is torque-proof connected to the rotor shaft, and the second component is used for magnetic conduction. This design helps optimize the rotor structure and improves the efficiency and performance of the motor. A groove is formed between the first and second components, simplifying the groove processing and assembly processes. Further preferably, the first component restricts radial outward movement of the second component. This restriction helps maintain the stable position of the second component, ensuring accurate installation of the magnets and normal operation of the rotor. This restriction can be achieved through form-fitting. For example, if the second component is designed to be triangular and the first component is designed to accommodate the triangle, during high-speed rotation, the first component can restrict radial outward movement of the second component due to centrifugal force, thereby creating a more stable structure. The second component is inserted into the first component, which is in contact with the rotor shaft. During high-speed rotation, the forces caused by the weight of the second component are not directly transmitted to the outer fiber sleeve. This not only reduces stress on the carbon fiber sleeve but also minimizes the risk of rotor deformation. More preferably, gaps exist at the outer edges of the rotor laminations, and the adhesive can evenly fill these gaps. Thus, the adhesive, made of an injection-molded polymer material, replaces the traditional ferromagnetic bridges between the magnets, thereby reducing magnetic flux leakage.

[0009] According to a preferred embodiment of the present invention, the fiber sleeve has a thickness of 0.5 to 3 mm, particularly 0.5 to 1 mm. The use of adhesive to secure the magnets reduces stress on the fiber sleeve from the rotor laminations and magnets, allowing the sleeve's thickness to be reduced. This helps reduce the size and weight of the rotor assembly while maintaining sufficient strength to meet the motor's performance requirements.

[0010] In summary, the present invention provides a rotor assembly for an electric motor whose optimized design and structure contribute to improved motor performance, efficiency, and reliability. By improving the magnet fixing method and utilizing adhesives to provide additional holding force for the magnets, the rotor laminations form a self-locking structure capable of withstanding centrifugal forces at ultra-high speeds.

[0011] In addition, the technical problem to be solved by the present invention can also be solved by an electric motor having a rotor assembly with the above-mentioned features. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The preferred embodiments of the present invention are further described below with reference to the accompanying drawings.

[0013] FIG1 shows a perspective view and an exploded view of a rotor assembly designed according to the present invention;

[0014] FIG2 shows a cross-sectional view of a rotor assembly and its components designed according to the present invention;

[0015] FIG3 shows a structural diagram of a rotor assembly designed according to the present invention.

[0016] Unless otherwise specified, the “axial direction”, “radial direction” and circumferential direction mentioned in the present invention are all relative to the rotor axis. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings. The following detailed description and the accompanying drawings are used to illustrate the principles of the present invention by way of example. The present invention is not limited to the preferred embodiments described, and the scope of the present invention is defined by the claims. The present invention will now be described in detail with reference to exemplary embodiments, some of which are illustrated in the accompanying drawings. The following description is made with reference to the accompanying drawings, and unless otherwise indicated, the same reference numerals in different drawings represent the same or similar elements. The schemes described in the following exemplary embodiments do not represent all schemes of the present invention. On the contrary, these schemes are merely examples of systems and methods of various aspects of the present invention involved in the appended claims.

[0018] As shown in Figure 1, the rotor assembly comprises a rotor shaft 1 and a rotor lamination stack 2. A fiber sheath 5, preferably made of carbon fiber, is wound around the outer periphery of the rotor lamination stack 2 to limit deformation of the rotor laminations at high speeds. During the winding process, the fiber sheath 5 is pre-tensioned and wound around the outside of the rotor lamination stack 2. The thickness of the fiber sheath 5 can range from 0.5 mm to 3 mm, depending on the calculated centrifugal force. To reduce the thickness of the fiber sheath 5, it can be wound around the rotor lamination stack under pre-tensioning and at a low temperature (-20 degrees Celsius).

[0019] Figure 2 is a cross-sectional view of the components shown in Figure 1. As can be seen, the rotor lamination stack 2 has a central hole in the center for receiving the rotor shaft 1. Multiple lightening holes 24 are arranged around the periphery of the central hole to reduce the overall weight of the rotor lamination stack 2. The circular area extending from the periphery of the lightening holes 24 to the edge is evenly divided into several magnet placement areas 25. Each magnet security area 25 is provided with multiple grooves 23. According to this embodiment, the grooves within each magnet placement area 25 are arranged in a triangular shape, with a magnet 3 positioned on each of the three sides. The three magnets 3 are spaced apart and do not touch each other. According to the design of the present invention, the grooves are injection molded to fill the gaps left by the magnets 3 and thereby secure the magnets 3 within the grooves. The injection molding material can be PPS, PA, or other polymer materials, and this is not strictly limited in the present invention, as long as they achieve the same function. During the injection molding process, all grooves 23 are filled with these polymer materials to ensure that there are no gaps or pores. These injection molding materials act as both an adhesive and bind the rotor laminations and magnets together, improving the stability of the rotor lamination stack 2. These features create a more robust design and improved performance, especially at ultra-high speeds. As shown in the left image of Figure 1 , the adhesive material after injection molding will cover the axial end surface of the groove 23, but will not completely cover the entire axial end surface to avoid stress concentration. This covering shape can be achieved through demolding.

[0020] Figure 3 illustrates a specific embodiment of a rotor lamination. In this embodiment, the rotor lamination 2 is not a single unit, but rather consists of two components: a first component 21 and a second component 22. Besides magnetic induction, the first component 21 primarily supports the rotor and is connected to the rotor shaft 1. The second component 2 serves as the critical path for magnetic flux from the rotor to the stator. As shown in the figure, the second component 22 is generally triangular in shape. After being assembled onto the first component 21, its radially outward movement is restricted by the first component 21. Therefore, during high-speed rotation, the forces generated by the second component 22 are not directly transmitted to the outer fiber sleeve 5. This not only reduces stress on the fiber sleeve 5 but also reduces the risk of rotor deformation. By filling the grooves 23 with injection molding material, the magnets 3 are integrated with the first and second components 21, 22, creating a self-locking structure for the rotor lamination that can withstand centrifugal forces at high speeds. Furthermore, as shown in the figure, after assembly, the first and second components 21, 22 do not completely enclose the outer circumference of the rotor lamination. Instead, the traditional ferromagnetic bridge is replaced with injection-molded polymer material 4. Since polymer materials do not conduct magnetic flux, there is no flux leakage within the rotor laminations.

[0021] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the configurations and methods of the above-described embodiments. On the contrary, the present invention is intended to cover various modifications and equivalent configurations. In addition, although the various elements and method steps of the disclosed invention are shown in various exemplary combinations and configurations, other combinations including more or fewer elements or methods also fall within the scope of the present invention.

[0022] LIST OF REFERENCE NUMERALS 1 Rotor shaft 2 Rotor lamination stack 21 First component 22 Second component 23 Recess 24 Lightening hole 25 Magnet receiving area 3 Magnet 4 Adhesive element 5 Fiber sleeve

Claims

1. A rotor assembly for an electric machine, having a rotor shaft (1), a rotor lamination stack (2) and a tensioned fiber sleeve (5) wound around the outer periphery of the rotor lamination stack (2), the rotor lamination stack (2) having grooves (23) for receiving magnets (3), wherein, A bonding member (4) is further provided in the groove (23) for fixing the magnet (3) in the groove (23).

2. The rotor assembly according to claim 1, characterized in that, The bonding member (4) is formed by injection molding in the groove (23).

3. The rotor assembly according to claim 2, characterized in that, The bonding member (4) covers the groove (23) on the axial end face of the rotor lamination stack (2).

4. The rotor assembly according to claim 2, characterized in that, The bonding member (4) is made of a polymer material.

5. The rotor assembly according to any one of claims 1 to 4, characterized in that, The rotor lamination stack (2) is evenly divided into a plurality of magnet placement areas (25) in the circumferential direction, and three magnets (3) arranged in a triangle and spaced apart from each other are provided in each magnet placement area (25).

6. The rotor assembly according to claim 5, characterized in that, The rotor lamination stack (2) has a first component (21) and a second component (22), and the gap between the first component (21) and the second component (22) forms the groove (23). Among them, the first component (21) is torsionally connected to the rotor shaft (1), and the second component (22) is used for magnetic conduction.

7. The rotor assembly according to claim 6, characterized in that, The first component (21) restricts the second component (22) from moving radially outward.

8. The rotor assembly according to claim 7, characterized in that, There is a gap between the first component (21) and the second component (22) on the outer edge of the rotor lamination stack (2).

9. The rotor assembly according to any one of claims 1 to 4, characterized in that, The thickness of the fiber sleeve (5) is 0.5 to 3 millimeters.

10. A motor, characterized in that, The motor has a rotor assembly according to any one of claims 1 to 9.

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