Rotor assembly and motor having the same

Abstract

The present invention provides a rotor assembly and a motor having the same, wherein the rotor assembly includes: a permanent magnet sleeve divided into an even number of regions, each region being constructed with a first permanent magnet slot and a permanent magnet slot group surrounding the first permanent magnet slot; the first permanent magnet slot is filled with a first permanent magnet, and the permanent magnet slot group is filled with multiple permanent magnets; the first permanent magnet has stronger magnetic properties than the permanent magnets in the permanent magnet slot group, and the permanent magnets in the permanent magnet slot group have stronger high-temperature demagnetization resistance than the first permanent magnet. According to the present invention, by filling the first permanent magnet slot with the stronger first permanent magnet and filling the permanent magnet slot group with multiple permanent magnets with stronger high-temperature demagnetization resistance, the permanent magnets in the permanent magnet slot group provide peripheral protection for the first permanent magnet. This arrangement maximizes the use of the first permanent magnet to improve the magnetic properties of the rotor and the use of the peripheral permanent magnets to improve the rotor's demagnetization resistance, thereby shortening the axial length of the rotor.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and in particular relates to a rotor assembly and a motor having the same. Background Art

[0002] At present, the rare earth permanent magnet materials mainly used in the field of high-speed motors include samarium cobalt permanent magnets and neodymium iron boron permanent magnets. In practical applications, these two types of permanent magnets are usually used alone in high-speed motors. Compared with neodymium iron boron permanent magnets, samarium cobalt permanent magnets have the advantage of strong anti-demagnetization ability at high temperatures. The temperature coefficient of Br is usually -0.03%K. -1 , the temperature coefficient of Hci is -0.2%K -1 Therefore, samarium cobalt permanent magnets are particularly suitable for high-speed motors with high loss density, small size, and difficult heat dissipation. However, the magnetic properties of samarium cobalt permanent magnets are weaker than those of neodymium iron boron, and the remanence Br is generally 1.08-1.12T. Therefore, under the same magnetic field requirements, if neodymium iron boron permanent magnets are used alone, it will make it difficult to reduce the axial size of the motor rotor, which will lead to insufficient rotor fixed frequency margin. If a certain amount of neodymium iron boron permanent magnets can be added to the rotor equipped with samarium cobalt permanent magnets, and the samarium cobalt permanent magnets and neodymium iron boron permanent magnets are reasonably arranged, the high-speed motor equipped with these two permanent magnets can have strong high-temperature anti-demagnetization ability and better magnetic properties. Therefore, the improvement of magnetic properties can effectively reduce the axial size of the motor rotor. Although the prior art uses a combination of samarium cobalt permanent magnets and neodymium iron boron permanent magnets in motors, the starting point is not to reduce the axial size of the motor rotor, nor does it consider how to reasonably arrange the two permanent magnets. Summary of the Invention

[0003] Therefore, the present invention provides a rotor assembly that can overcome the disadvantage that when samarium cobalt permanent magnets are used alone in high-speed motors, the axial size of the motor rotor is difficult to reduce due to the weak magnetic properties of the samarium cobalt permanent magnets.

[0004] In order to solve the above problems, the present invention provides a rotor assembly, comprising: a permanent magnet sleeve, the interior of the permanent magnet sleeve is divided into an even number of areas, each of the areas is respectively constructed with a first permanent magnet slot and a permanent magnet slot group surrounding the first permanent magnet slot, the first permanent magnet slot and the permanent magnet slot group both penetrate the axial direction of the permanent magnet sleeve, the first permanent magnet slot is filled with a first permanent magnet, the permanent magnet slot group is filled with a plurality of permanent magnets, the magnetic properties of the first permanent magnet are stronger than the magnetic properties of each permanent magnet in the permanent magnet slot group, and the high-temperature anti-demagnetization capability of each permanent magnet in the permanent magnet slot group is stronger than the high-temperature anti-demagnetization capability of the first permanent magnet.

[0005] In some embodiments, the permanent magnet slot group includes a second permanent magnet slot, which is located outside the first permanent magnet slot along the radial direction of the permanent magnet sleeve, and is filled with a second permanent magnet.

[0006] In some embodiments, the permanent magnet slot group further includes a third permanent magnet slot. Along the radial direction of the permanent magnet sleeve, the third permanent magnet slot is located on the inner side of the first permanent magnet slot, and the third permanent magnet slot is filled with a third permanent magnet.

[0007] In some embodiments, the permanent magnet slot group further includes a fourth permanent magnet slot, which is located on one side of the first permanent magnet slot along the circumferential direction of the permanent magnet sleeve, and is filled with a fourth permanent magnet.

[0008] In some embodiments, the permanent magnet slot group further includes a fifth permanent magnet slot. Along the circumferential direction of the permanent magnet sleeve, the fifth permanent magnet slot is located on the side of the first permanent magnet slot away from the fourth permanent magnet slot, and the fifth permanent magnet slot is filled with a fifth permanent magnet.

[0009] In some embodiments, the fourth permanent magnet slot and the fifth permanent magnet slot are symmetrical with respect to the first permanent magnet slot.

[0010] In some embodiments, the second permanent magnet, the third permanent magnet, the fourth permanent magnet, and the fifth permanent magnet are made of the same material.

[0011] In some embodiments, the first permanent magnet is a neodymium iron boron permanent magnet, and the second permanent magnet, the third permanent magnet, the fourth permanent magnet, and the fifth permanent magnet are all samarium cobalt permanent magnets.

[0012] In some embodiments, the volume of the first permanent magnet is V1, the sum of the volumes of the second permanent magnet, the third permanent magnet, the fourth permanent magnet, and the fifth permanent magnet is V2, and the ratio of V1 to V2 is 1:3 to 1:2.

[0013] In some embodiments, a thermal conductive coating is sprayed on each side wall of the first permanent magnet slot, the second permanent magnet slot, the third permanent magnet slot, the fourth permanent magnet slot, and the fifth permanent magnet slot, as well as the outer peripheral side wall of the permanent magnet sleeve.

[0014] In some embodiments, the thickness of the thermal conductive coating is 10-20 μm.

[0015] In some embodiments, a rotating shaft is further included, and the permanent magnet sleeve is further configured with a through hole that penetrates the axial direction thereof and is used to install the rotating shaft, and each of the third permanent magnet slots surrounds the periphery of the through hole.

[0016] In some embodiments, a rotor sleeve is sleeved on the outer peripheral side of the permanent magnet sleeve.

[0017] The present invention also provides a motor comprising the above-mentioned rotor assembly.

[0018] The present invention provides a rotor assembly and a motor having the same. A first permanent magnet slot and a permanent magnet slot group surrounding the first permanent magnet slot are constructed in each region of a permanent magnet sleeve. The first permanent magnet slot is filled with a first permanent magnet, and the permanent magnet slot group is filled with multiple permanent magnets. This allows each permanent magnet in the permanent magnet slot group to surround the first permanent magnet, protecting the first permanent magnet. When the permanent magnets of different properties are arranged in this manner, not only can the permanent magnets surrounding the first permanent magnet improve the rotor's high-temperature demagnetization resistance, but the first permanent magnet's strong magnetic properties can also be maximized to improve the rotor's magnetic properties. This significantly improves the rotor's magnetic properties, effectively shortening its axial length and increasing its fixed frequency while maintaining excellent high-temperature demagnetization resistance. Furthermore, a high-speed motor equipped with the rotor has both superior electromagnetic performance and strong demagnetization resistance, thereby miniaturizing the high-speed motor and further improving its power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the rotor assembly according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the structure of the permanent magnet sleeve of the rotor assembly according to an embodiment of the present invention.

[0021] The reference numerals indicate:

[0022] 1. Permanent magnet sleeve; 2. First permanent magnet slot; 3. Second permanent magnet slot; 4. Third permanent magnet slot; 5. First permanent magnet; 6. Second permanent magnet; 7. Third permanent magnet; 8. Fourth permanent magnet slot; 9. Fifth permanent magnet slot; 10. Fourth permanent magnet; 11. Fifth permanent magnet; 12. Rotating shaft; 13. Through hole; 14. Rotor sleeve. DETAILED DESCRIPTION

[0023] See also Figure 1 and Figure 2As shown, according to an embodiment of the present invention, a rotor assembly is provided, comprising: a permanent magnet sleeve 1, the interior of the permanent magnet sleeve 1 being divided into an even number of regions, each region being respectively constructed with a first permanent magnet slot 2 and a permanent magnet slot group surrounding the first permanent magnet slot 2, the first permanent magnet slot 2 and the permanent magnet slot group both running through the axial direction of the permanent magnet sleeve 1, the first permanent magnet slot 2 being filled with a first permanent magnet 5, the permanent magnet slot group being filled with a plurality of permanent magnets, the magnetic properties of the first permanent magnet 5 being stronger than the magnetic properties of each permanent magnet in the permanent magnet slot group, and the high-temperature demagnetization resistance of each permanent magnet in the permanent magnet slot group being stronger than the high-temperature demagnetization resistance of the first permanent magnet 5. In this technical solution, a first permanent magnet slot 2 and a permanent magnet slot group surrounding the outside of the first permanent magnet slot 2 are constructed in each area of the permanent magnet sleeve 1, and the first permanent magnet 5 is filled in the first permanent magnet slot 2, and multiple permanent magnets are filled in the permanent magnet slot group. This allows the permanent magnets in the permanent magnet slot group to surround the periphery of the first permanent magnet 5, thus providing protection for the first permanent magnet 5. Because the permanent magnets in the permanent magnet slot group have strong high-temperature demagnetization resistance, the stator magnetic field has little effect on the magnetic properties of these permanent magnets. Since these permanent magnets surround the periphery of the first permanent magnet 5, these permanent magnets have a suppressive effect on the demagnetization of the first permanent magnet 5, allowing the first permanent magnet 5 to maintain its excellent magnetic properties. When the permanent magnets of different properties are arranged in this way, not only can the high-temperature anti-demagnetization ability of the rotor be improved by utilizing the permanent magnets surrounding the periphery of the first permanent magnet 5, but also the strong magnetic properties of the first permanent magnet 5 can be maximized to improve the magnetic properties of the rotor, so that the rotor can effectively shorten the axial length of the rotor due to the significant improvement in magnetic properties while having better high-temperature anti-demagnetization ability, thereby improving the fixed frequency of the rotor, and also making the high-speed motor equipped with the rotor not only have superior electromagnetic properties, but also have strong anti-demagnetization ability, thereby realizing the miniaturization of the structure of the high-speed motor and further improving its power density. Among them, the permanent magnet sleeve is made of a material with good magnetic and thermal conductivity. In this application, the interior of the permanent magnet sleeve 1 is evenly divided into four rotor poles, each rotor pole represents an area. Magnetic properties refer to the magnetic properties of the permanent magnet, which are closely related to the magnetic energy product of the permanent magnet.

[0024] As a specific embodiment, the permanent magnet slot group includes a second permanent magnet slot 3 . Along the radial direction of the permanent magnet sleeve 1 , the second permanent magnet slot 3 is located outside the first permanent magnet slot 2 . The second permanent magnet slot 3 is filled with a second permanent magnet 6 .

[0025] In this embodiment, due to the influence of the stator magnetic field, demagnetization is most serious in the radial direction of the permanent magnet sleeve 1, close to the radial outer side of the permanent magnet sleeve 1. Therefore, it is necessary to assemble a second permanent magnet 6 with strong high-temperature anti-demagnetization ability on the outer side of the first permanent magnet 5, thereby forming a protection for the first permanent magnet 5 on the outermost side.

[0026] As a specific embodiment, the permanent magnet slot group further includes a third permanent magnet slot 4 . Along the radial direction of the permanent magnet sleeve 1 , the third permanent magnet slot 4 is located inside the first permanent magnet slot 2 . The third permanent magnet slot 4 is filled with a third permanent magnet 7 .

[0027] In this embodiment, the end face of the first permanent magnet 5 close to the radial inner side of the permanent magnet sleeve 1 is also a place where magnetic flux leakage is more likely to occur. Therefore, a second permanent magnet 6 with strong high-temperature anti-demagnetization ability is also required to protect this end face of the first permanent magnet 5, thereby suppressing magnetic flux leakage from the end face and allowing the first permanent magnet 5 to better maintain its magnetic properties.

[0028] As a specific embodiment, the permanent magnet slot group further includes a fourth permanent magnet slot 8 . Along the circumferential direction of the permanent magnet sleeve 1 , the fourth permanent magnet slot 8 is located on one side of the first permanent magnet slot 2 . The fourth permanent magnet slot 8 is filled with a fourth permanent magnet 10 .

[0029] In this embodiment, because the side surface of the first permanent magnet 5 along the circumferential direction of the permanent magnet sleeve 1 is also an area where demagnetization is relatively easy to occur, it is also necessary to construct a fourth permanent magnet slot 8 on the outer side of the first permanent magnet slot 2 along the circumferential direction of the permanent magnet sleeve 1, and fill the fourth permanent magnet slot 8 with a fourth permanent magnet 10 whose high-temperature anti-demagnetization ability is stronger than that of the first permanent magnet 5. In this way, the first permanent magnet 5 will be protected by the permanent magnets on three sides, which can further prevent the first permanent magnet 5 from leaking magnetic flux.

[0030] As a specific embodiment, the permanent magnet slot group also includes a fifth permanent magnet slot 9. Along the circumferential direction of the permanent magnet sleeve 1, the fifth permanent magnet slot 9 is located on the side of the first permanent magnet slot 2 away from the fourth permanent magnet slot 8, and the fifth permanent magnet slot 9 is filled with a fifth permanent magnet 11.

[0031] In this embodiment, by providing a fifth permanent magnet slot 9 and filling the fifth permanent magnet slot 9 with a fifth permanent magnet 11 having a higher high-temperature demagnetization resistance than the first permanent magnet 5, the first permanent magnet 5 is protected from all four sides. That is, the first permanent magnet 5 is centered, and the remaining permanent magnets surround the centered first permanent magnet 5 without blind spots. Since the end faces and corners of the first permanent magnet 5 are the areas most susceptible to demagnetization, this four-sided, no-blind-spot surround of the first permanent magnet 5 can minimize demagnetization of the first permanent magnet 5, thereby allowing the first permanent magnet 5 to more fully exert its excellent magnetic properties, which helps to minimize the axial length of the rotor.

[0032] As a specific implementation, the fourth permanent magnet slot 8 and the fifth permanent magnet slot 9 are symmetrical with respect to the first permanent magnet slot 2 .

[0033] In this embodiment, when the fourth permanent magnet slot 8 and the fifth permanent magnet slot 9 are symmetrical relative to the first permanent magnet slot 2, the fourth permanent magnet 10 filled in the fourth permanent magnet slot 8 and the fifth permanent magnet 11 filled in the fifth permanent magnet slot 9 can also be symmetrical relative to the first permanent magnet slot 2, which is conducive to uniform distribution of the magnetic field in the motor, thereby facilitating the operation of the motor.

[0034] As a specific implementation, the second permanent magnet 6 , the third permanent magnet 7 , the fourth permanent magnet 10 and the fifth permanent magnet 11 are made of the same material.

[0035] In this embodiment, when the second permanent magnet 6, the third permanent magnet 7, the fourth permanent magnet 10 and the fifth permanent magnet 11 are made of the same material, the four permanent magnets have the same demagnetization suppression effect on the four end faces and corners of the first permanent magnet 5, thereby ensuring the stability of the overall magnetic properties of the first permanent magnet 5 and ensuring the stable operation of the motor.

[0036] As a specific implementation, the first permanent magnet 5 is a neodymium iron boron permanent magnet, and the second permanent magnet 6 , the third permanent magnet 7 , the fourth permanent magnet 10 and the fifth permanent magnet 11 are all samarium cobalt permanent magnets.

[0037] In this embodiment, the primary permanent magnets used in high-speed motors are samarium cobalt (SmCo) and neodymium iron boron (NdFeB). SmCo has the advantage of greater resistance to demagnetization at high temperatures compared to NdFeB, but its magnetic properties are weaker than those of NdFeB. Therefore, using SmCo alone results in a larger rotor axial dimension under the same magnetic field requirements. However, combining NdFeB and SmCo in the aforementioned arrangement allows the high-speed motor to possess both superior high-temperature demagnetization resistance and improved magnetic properties, significantly reducing the axial dimension of the high-speed motor compared to using SmCo alone. For ordinary motors other than high-speed motors, if it is also necessary to use a combination of permanent magnets with different properties to reduce the axial length of the motor rotor and improve the performance of the motor, in addition to filling the first permanent magnet slot 2 with neodymium iron boron permanent magnets and filling the second permanent magnet slot 3, the third permanent magnet slot 4, the fourth permanent magnet slot 8 and the fifth permanent magnet slot 9 with samarium cobalt permanent magnets, other commonly used permanent magnets can also be filled in these permanent magnet slots. As long as the magnetic properties of the permanent magnet filled in the first permanent magnet slot 2 are stronger than those in the other permanent magnet slots and its high-temperature demagnetization resistance is weaker than that of the permanent magnets in the other permanent magnet slots, that is, as long as the arrangement of the present application can be used. Among them, the second permanent magnet 6, the third permanent magnet 7, the fourth permanent magnet 10 and the fifth permanent magnet 11 can be the same permanent magnet or different permanent magnets. When assembling the permanent magnets in their slots, each permanent magnet is fitted with a clearance between the slot and the corresponding permanent magnet, with a clearance of 0.05-0.08mm on each side. To enhance rotor frequency retention and secure the permanent magnets more firmly within their slots, resin glue is applied to the outer surface of the permanent magnets before assembly.

[0038] As a specific implementation, the volume of the first permanent magnet 5 is V1, the sum of the volumes of the second permanent magnet 6, the third permanent magnet 7, the fourth permanent magnet 10 and the fifth permanent magnet 11 is V2, and the ratio of V1 to V2 is 1:3 to 1:2.

[0039] In this embodiment, in order to make the central first permanent magnet 5, i.e., the NdFeB permanent magnet, and the second permanent magnet 6, the third permanent magnet 7, the fourth permanent magnet 10 and the fifth permanent magnet 11, i.e., the SmCo permanent magnets surrounding the first permanent magnet 5, be combined to achieve the best performance, that is, to maximize the comprehensive utilization of the high-quality magnetic properties of the NdFeB permanent magnet and the superior high-temperature magnetic stability of the SmCo permanent magnet, there are certain requirements for the volume ratio of the NdFeB permanent magnet and the SmCo permanent magnet. In this application, when the ratio of the volume V1 of the NdFeB permanent magnet to the sum of the volumes V2 of each SmCo permanent magnet is 1:3 to 1:2, the performance of the combination of the two permanent magnets is best, which can further reduce the axial length of the motor rotor.

[0040] As a specific implementation, thermal conductive coating is sprayed on each side wall of the first permanent magnet slot 2 , the second permanent magnet slot 3 , the third permanent magnet slot 4 , the fourth permanent magnet slot 8 and the fifth permanent magnet slot 9 and the outer peripheral side wall of the permanent magnet sleeve 1 .

[0041] In this embodiment, the spraying of a thermally conductive coating achieves efficient heat transfer within the rotor, rapidly transferring heat from the rotor's interior to its outer surface, preventing heat accumulation within the permanent magnet sleeve 1 and thus avoiding high-temperature demagnetization of the centrally located NdFeB permanent magnets. The thermally conductive coating is made of materials such as graphene and highly thermally conductive resin.

[0042] As a specific implementation, the thickness of the thermal conductive coating is 10-20 um.

[0043] In this embodiment, in order to balance thermal conductivity and material saving, the appropriate thickness of the thermal conductive coating is 10-20 μm.

[0044] As a specific embodiment, it further includes a rotating shaft 12 . The permanent magnet sleeve 1 is further configured with a through hole 13 that penetrates the axial direction thereof and is used to install the rotating shaft 12 . The third permanent magnet slots 4 are respectively surrounded by the periphery of the through hole 13 .

[0045] In this embodiment, after the permanent magnet sleeve 1 is provided with a through hole 13 for mounting the rotating shaft 12, the third permanent magnets 7 filled in each third permanent magnet slot 4 are combined into a non-cylindrical permanent magnet. This avoids the high eddy current and low utilization rate issues associated with cylindrical permanent magnets. The rotating shaft 12 is inserted into the through hole 13 of the permanent magnet sleeve 1 with an interference fit. The rotating shaft is made of materials such as SUS304 or 40CrNiMoA. The specific material used for the rotating shaft is determined by the rotor strength and magnetic isolation requirements.

[0046] As a specific implementation, a rotor sleeve 14 is sleeved on the outer peripheral side of the permanent magnet sleeve 1 .

[0047] In this embodiment, the rotor sheath 14 and the permanent magnet sheath 1 are sleeved together using an interference fit. Since high-speed motors operate at high speeds and experience significant centrifugal stress, the rotor's structural strength is required to be high. The rotor sheath 14 improves the rotor's structural strength. Depending on the speed rating and performance requirements of the high-speed motor rotor, the rotor sheath can be made of alloy or composite materials such as carbon fiber.

[0048] According to an embodiment of the present invention, there is further provided a motor comprising the above-mentioned rotor assembly.

[0049] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A rotor assembly, characterized in that: The invention comprises a permanent magnet sleeve (1), wherein the interior of the permanent magnet sleeve (1) is divided into an even number of regions, each of the regions is respectively constructed with a first permanent magnet slot (2) and a permanent magnet slot group surrounding the first permanent magnet slot (2), the first permanent magnet slot (2) and the permanent magnet slot group both pass through the axial direction of the permanent magnet sleeve (1), the first permanent magnet slot (2) is filled with a first permanent magnet (5), the permanent magnet slot group is filled with a plurality of permanent magnets, the magnetic properties of the first permanent magnet (5) are stronger than the magnetic properties of each permanent magnet in the permanent magnet slot group, and the high-temperature demagnetization resistance of each permanent magnet in the permanent magnet slot group is stronger than the high-temperature demagnetization resistance of the first permanent magnet (5); The permanent magnet slot group comprises a second permanent magnet slot (3), wherein the second permanent magnet slot (3) is located outside the first permanent magnet slot (2) along the radial direction of the permanent magnet sleeve (1), and the second permanent magnet slot (3) is filled with a second permanent magnet (6); The permanent magnet slot group further comprises a third permanent magnet slot (4), which is located on the inner side of the first permanent magnet slot (2) along the radial direction of the permanent magnet sleeve (1), and is filled with a third permanent magnet (7).

2. The rotor assembly according to claim 1, wherein: The permanent magnet slot group further includes a fourth permanent magnet slot (8), which is located on one side of the first permanent magnet slot (2) along the circumferential direction of the permanent magnet sleeve (1), and is filled with a fourth permanent magnet (10).

3. The rotor assembly according to claim 2, wherein: The permanent magnet slot group further includes a fifth permanent magnet slot (9). Along the circumferential direction of the permanent magnet sleeve (1), the fifth permanent magnet slot (9) is located on a side of the first permanent magnet slot (2) away from the fourth permanent magnet slot (8), and the fifth permanent magnet slot (9) is filled with a fifth permanent magnet (11).

4. The rotor assembly according to claim 3, wherein: The fourth permanent magnet slot (8) and the fifth permanent magnet slot (9) are symmetrical with respect to the first permanent magnet slot (2).

5. The rotor assembly according to claim 3, wherein: The second permanent magnet (6), the third permanent magnet (7), the fourth permanent magnet (10) and the fifth permanent magnet (11) are made of the same material.

6. The rotor assembly according to claim 5, wherein: The first permanent magnet (5) is a neodymium iron boron permanent magnet, and the second permanent magnet (6), the third permanent magnet (7), the fourth permanent magnet (10) and the fifth permanent magnet (11) are all samarium cobalt permanent magnets.

7. The rotor assembly according to claim 3, wherein: The volume of the first permanent magnet (5) is V1, the sum of the volumes of the second permanent magnet (6), the third permanent magnet (7), the fourth permanent magnet (10) and the fifth permanent magnet (11) is V2, and the ratio of V1 to V2 is 1:3 to 1:

2.

8. The rotor assembly according to claim 3, wherein: The side walls of the first permanent magnet slot (2), the second permanent magnet slot (3), the third permanent magnet slot (4), the fourth permanent magnet slot (8) and the fifth permanent magnet slot (9) as well as the outer peripheral side wall of the permanent magnet sleeve (1) are sprayed with a thermal conductive coating.

9. The rotor assembly according to claim 8, wherein: The thickness of the thermal conductive coating is 10-20 μm.

10. The rotor assembly according to claim 1, wherein: It also includes a rotating shaft (12), and the permanent magnet sleeve (1) is also configured with a through hole (13) that runs through its axial direction and is used to install the rotating shaft (12), and each of the third permanent magnet slots (4) surrounds the periphery of the through hole (13).

11. The rotor assembly according to claim 1, wherein: A rotor sleeve (14) is sleeved on the outer peripheral side surface of the permanent magnet sleeve (1).

12. A motor, characterized in that: A rotor assembly comprising the rotor assembly according to any one of claims 1 to 11.

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