Motor rotors and permanent magnet motors

Abstract

The present invention proposes a motor rotor and a permanent magnet motor, characterized in that the motor rotor comprises: a rotating shaft; a magnetic layer, the magnetic layer is fixedly sleeved on the rotating shaft; a first heat diffusion layer, coated on the outer surface of the magnetic layer away from the rotating shaft, for preventing the shielding layer from local overheating; and a shielding layer, coated on the surface of the first heat diffusion layer away from the magnetic layer. The first heat diffusion layer is arranged between the shielding layer and the magnetic layer of the motor rotor, and the first heat diffusion layer can prevent the shielding layer and the magnetic layer from local overheating and improve the heat dissipation efficiency of the shielding layer.

Description

Technical Field

[0001] The present invention relates to the field of motors, and in particular to a motor rotor and a permanent magnet motor. Background Art

[0002] High-speed permanent magnet synchronous motors have many advantages, such as high power density, good dynamic response and simple structure, and have become one of the research hotspots in the international electrical engineering field. However, the permanent magnets in their rotors are generally made of sintered NdFeB permanent magnet materials, which are compression-resistant but not tensile-resistant. In order to ensure that the permanent magnets have sufficient strength at high speeds, a high-strength rotor sheath is generally wrapped around the permanent magnets. The rotor sheath and the permanent magnets are interference-fitted to ensure that the permanent magnets are still subject to a certain compressive stress during operation, thereby ensuring the safe operation of the high-speed motor.

[0003] There are two commonly used sheaths, one is a non-magnetic high-strength metal sheath, and the other is a carbon fiber binding sheath. Carbon fiber cannot shield the harmonic magnetic field entering the permanent magnet, so a large amount of eddy current loss will still be generated in the permanent magnet. When a metal sheath is used, the metal sheath will generate eddy current loss under the action of the high-frequency electromagnetic field, causing the sheath to heat up. Since the sheath is in close contact with the rotor permanent magnet, the heat in the sheath is easily transferred to the permanent magnet. When the temperature rise of the permanent magnet is too high, irreversible demagnetization will occur, which will reduce the performance of the motor or even damage it.

[0004] Therefore, it is an urgent problem to be solved in the art to improve the heat dissipation efficiency of the shielding layer while shielding the electromagnetic harmonics entering the permanent magnet and prevent the shielding layer from local overheating. Summary of the invention

[0005] The present invention provides a motor rotor and a permanent magnet motor, thereby shielding electromagnetic harmonics entering a permanent magnet and improving the heat dissipation efficiency of a shielding layer, thereby preventing the shielding layer from being locally overheated.

[0006] In order to solve the above problem, as one aspect of the present invention, a motor rotor is provided, comprising:

[0007] A rotating shaft; a magnetic layer, wherein the magnetic layer is fixedly sleeved on the rotating shaft;

[0008] A first heat diffusion layer is coated on the outer surface of the magnetic layer away from the rotating shaft and is used to prevent the shielding layer from being locally overheated;

[0009] The shielding layer is coated on the surface of the first heat diffusion layer which is away from the magnetic layer.

[0010] Optionally, a first thermal conductivity of the first heat diffusion layer along a thickness direction is smaller than a second thermal conductivity of the first heat diffusion layer along an extension direction.

[0011] Optionally, the first heat diffusion layer is a first carbon fiber layer, the radial direction of the first carbon fiber layer is parallel to the thickness direction of the first heat diffusion layer, and the fiber direction of the first carbon fiber layer is parallel to the extension direction of the first heat diffusion layer.

[0012] Optionally, it also includes: a second heat diffusion layer; the second heat diffusion layer is coated on the outer surface of the shielding layer away from the magnetic layer.

[0013] Optionally, the second heat diffusion layer is a second carbon fiber layer, the radial direction of the second carbon fiber layer is parallel to the thickness direction of the second heat diffusion layer, and the fiber direction of the second carbon fiber layer is parallel to the extension direction of the second heat diffusion layer.

[0014] Optionally, a plurality of metal heat-conducting members are provided in the second carbon fiber layer, and the metal heat-conducting members extend in a radial direction of the second carbon fiber layer, so as to improve the thermal conductivity of the second carbon fiber layer in the radial direction.

[0015] Optionally, the first heat diffusion layer and the second heat diffusion layer are made of the same material, and the thickness of the first heat diffusion layer is greater than the thickness of the second heat diffusion layer.

[0016] Optionally, the first heat diffusion layer and the magnetic layer are interference fit.

[0017] Optionally, it is characterized in that

[0018] The magnetic layer is a ring-shaped permanent magnet;

[0019] or,

[0020] The magnetic layer comprises a fixing device and a permanent magnet. The fixing device is fixedly sleeved on the rotating shaft. An installation groove is arranged on the outer surface of the fixing device away from the rotating shaft. The permanent magnet is installed in the installation groove.

[0021] Optionally, the magnetic layer includes a fixing device and a permanent magnet, and the fixing device is made of a heat storage material.

[0022] Optionally, the permanent magnets include neodymium iron boron magnets and / or samarium cobalt magnets.

[0023] Optionally, the thickness of the shielding layer is greater than 0.03 mm and less than 1.5 mm.

[0024] The present application also proposes a permanent magnet motor, which also includes any motor rotor proposed in the present application.

[0025] The present application proposes a motor rotor and a permanent magnet motor, wherein a first heat diffusion layer is arranged between the shielding layer and the magnetic layer of the motor rotor, and the first heat diffusion layer can prevent local overheating of the shielding layer and the magnetic layer and improve the heat dissipation efficiency of the shielding layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1is a schematic diagram of a motor rotor in an embodiment of the present invention;

[0027] Figure 2 FIG. 4 is a schematic diagram of another motor rotor in an embodiment of the present invention.

[0028] Reference numerals in the figure: 1, rotating shaft; 2, magnetic layer; 21, fixing device; 22, permanent magnet; 3, first heat diffusion layer; 4, shielding layer; 5, second heat diffusion layer. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or appliance that includes a series of steps or modules is not necessarily limited to those steps or modules that are clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products or appliances.

[0031] In the prior art, motor rotors, especially permanent magnet motor rotors, often need to be shielded by a shielding layer to shield the harmonic magnetic field entering the permanent magnet. However, the shielding layer itself will produce eddy current loss under the action of the high-frequency electromagnetic field, resulting in heat generation. Therefore, it is necessary to improve the heat dissipation efficiency of the shielding layer while shielding the harmonic magnetic field entering the permanent magnet. Based on this, the present application proposes a motor rotor, such as Figure 1 and Figure 2As shown, the motor rotor proposed in the present application includes: a rotating shaft 1, a magnetic layer 2, a first heat diffusion layer 3 and a shielding layer 4; wherein the magnetic layer 2 is fixedly sleeved on the rotating shaft 1; the magnetic layer 2 can be an annular structure, and a connecting hole can be opened in the middle, and the rotating shaft 1 passes through the connecting hole and is fixed on the rotating shaft 1. Specifically, the magnetic layer can be a magnetic steel, and a magnetic steel glue can be coated on the contact surface between the magnetic layer 2 and the rotating shaft 1 to fix it on the rotating shaft. The first heat diffusion layer 3 is coated on the outer surface of the magnetic layer 2 away from the rotating shaft 1 to prevent the shielding layer 4 from local overheating; the first heat diffusion layer 3 can be a circular ring structure so as to be sleeved on the outside of the magnetic layer 2, and the first heat diffusion layer 3 can be interference fit with the magnetic layer 2, so that the first heat diffusion layer 3 provides a certain pre-pressure for the magnetic layer 2. Generally, the magnetic layer 2 can be a permanent magnet, which is resistant to pressure but not to tension. The shielding layer 4 is coated on the surface of the first heat diffusion layer 3 away from the magnetic layer. The side of the shielding layer 4 away from the first heat diffusion layer 3 can be in direct contact with the surrounding environment, thereby accelerating the heat dissipation efficiency of the shielding layer to the surrounding environment. The shielding layer can be made of metal materials such as copper, which can shield harmonic magnetic fields and reduce eddy current losses in permanent magnets. The shielding layer itself will increase in temperature during use due to eddy current losses. Therefore, it is necessary to improve the heat dissipation efficiency of the shielding layer to improve the heat dissipation of the motor rotor itself and prevent the local temperature of the shielding layer from affecting the magnetic layer of the motor rotor. The excessive temperature of the magnetic layer will cause permanent demagnetization. Therefore, the present application sets a first heat diffusion layer, which is set between the magnetic layer and the shielding layer. The function of the first heat diffusion layer is to absorb the heat of the shielding layer and make the heat propagate along the extension direction of the first heat diffusion layer. The extension direction here refers to the direction parallel to the shielding layer and the magnetic layer. direction, thereby preventing heat from gathering locally in the shielding layer, so that the shielding layer as a whole is in a thermally uniform state, and by preventing the local temperature from being too high, the partial demagnetization of the magnetic layer is avoided. When the shielding layer is locally hot, the heat is diffused to the entire shielding layer, that is, the heat dissipation area of ​​the shielding layer is increased to improve the heat dissipation performance. In the present application, the first heat diffusion layer can be a whole, in contact with all surfaces of the shielding layer on the side close to the magnetic layer. Therefore, when the shielding layer has cracks or includes multiple parts separated from each other, the heat of one part of the shielding layer can be transferred to other parts through the first heat diffusion layer, so as to increase the heat dissipation area to promote heat dissipation and prevent local overheating of the shielding layer.

[0032] Optionally, a first thermal conductivity of the first heat diffusion layer 3 along the thickness direction is less than a second thermal conductivity of the first heat diffusion layer along the extension direction. Optionally, the first heat diffusion layer is a carbon fiber layer, i.e., made of carbon fiber, the radial direction of the first carbon fiber layer is parallel to the thickness direction of the first heat diffusion layer 3, and the fiber direction of the first carbon fiber layer is parallel to the extension direction of the first heat diffusion layer 3. The radial direction of the first carbon fiber layer is the direction from the magnetic layer to the shielding layer. The fiber direction of the first carbon fiber layer is parallel to the shielding layer. The thermal conductivity of the carbon fiber material in the fiber direction is relatively high, which can reach 700W / (mK). The thermal conductivity of the carbon fiber material in the radial direction is relatively low, which is about 6.5W / (mK). The thermal conductivity in the radial direction is relatively low but not heat-insulating, so that the first heat diffusion layer itself can have a certain heat absorption effect. In this case, when the heat of the magnetic layer 2 is too high, it will not be demagnetized because the first heat diffusion layer cannot transfer heat. At this time, the first heat diffusion layer 3 also serves as a protective cover for the magnetic layer, which can provide a certain pre-pressure for the magnetic layer. The carbon fiber material itself has a low electrical conductivity and will not cause eddy current loss. In addition, the carbon fiber material has the characteristics of high strength and small thermal expansion coefficient, which is conducive to saving shaft space.

[0033] Optional, such as Figure 1 and Figure 2As shown, the motor rotor also includes: a second heat diffusion layer 5; the second heat diffusion layer 5 is coated on the outer surface of the shielding layer 4 away from the magnetic layer 2. In the present application, the second heat diffusion layer 5 can further ensure uniform heat distribution of the shielding layer on the one hand, and on the other hand, the second heat diffusion layer 5 can directly contact the surrounding environment to diffuse the heat of the shielding layer 4 into the surrounding environment. Optionally, the second heat diffusion layer is made of non-metallic thermal conductive material, and the inflow can be a composite composed of insulating thermal conductive inorganic particles and a polymer body, wherein the inorganic particles are preferably boron nitride, silicon nitride and aluminum oxide, and metal particles can also be used, that is, the metal particles are embedded in the polymer body as the second heat diffusion layer. At this time, the metal particles in the polymer body can absorb a certain harmonic magnetic field, reduce the total amount of harmonic magnetic field of the shielding layer, thereby reducing the overall temperature of the shielding layer, and the metal particles are diffusely distributed in the polymer body, so the heat dissipation Higher efficiency, optionally, the polymer body can be a carbon fiber material, the carbon fiber layer material is a multi-layer structure, the fiber direction is parallel to the shielding layer 4, and the radial direction is the direction of the shielding layer 4 pointing to the second heat diffusion layer 5. The thermal conductivity coefficient of the carbon fiber material in the fiber direction is extremely high, and the thermal conductivity coefficient in the radial direction is relatively low. Therefore, metal fibers can be arranged in the carbon fiber layer. The extension direction of the metal fibers is the radial direction of the carbon fiber layer. The metal fibers are in contact with the carbon of each layer in the carbon fiber material. The size of the metal fibers is small, so the strength of the carbon fiber layer along the fiber direction will not be destroyed. At the same time, the metal fibers can absorb the harmonic magnetic field and improve the overall thermal conductivity coefficient of the carbon fiber layer in the radial direction, thereby accelerating the heat transfer efficiency from the shielding layer 4 to the second heat diffusion layer 5 and accelerating the heat dissipation.

[0034] Optionally, the second heat diffusion layer 5 is a second carbon fiber layer, the radial direction of the second carbon fiber layer is parallel to the thickness direction of the second heat diffusion layer, and the fiber direction of the second carbon fiber layer is parallel to the extension direction of the second heat diffusion layer. Optionally, a plurality of metal heat conductors are arranged in the second carbon fiber layer, and the metal heat conductors extend along the radial direction of the second carbon fiber layer, and are used to improve the thermal conductivity of the second carbon fiber layer along the radial direction. The second carbon fiber layer is a multi-layer structure, and the thermal conductivity between each layer is low. In order to improve its thermal conductivity along the radial direction, a metal heat conductor is arranged, and the metal heat conductor can penetrate the second carbon fiber layer and contact the shielding layer. One end of the optional metal heat conductor can be fixedly arranged on the shielding layer, or can be integrally connected with the shielding layer, that is, a plurality of metal probes are protrudingly arranged on the shielding layer, and the metal probes penetrate or do not penetrate the second carbon fiber layer, thereby improving the thermal conductivity of the second carbon fiber layer along the radial direction and accelerating the heat dissipation to the external environment on the one hand, and increasing the contact area between the shielding layer and the second carbon fiber layer on the other hand, and improving the heat conduction efficiency. Preferably, as described above, the method of doping metal fibers in the second carbon fiber is adopted, the extension direction of the metal fibers can be randomly distributed or in the fiber direction of the second carbon fiber layer, the length of the metal fibers is preferably 10nm-20nm, and the metal fibers will not destroy the strength of the carbon layer along the fiber direction within the above-mentioned size range, while improving the radial thermal conductivity coefficient of the second carbon fiber layer, and the metal fibers themselves can also absorb harmonic magnetic fields. The metal fibers have a large specific surface area, and their thermal conduction efficiency with the second carbon fiber layer is extremely high.

[0035] Optionally, the first heat diffusion layer and the second heat diffusion layer are made of the same material, and the thickness of the first heat diffusion layer 3 is greater than that of the second heat diffusion layer. For example, the first heat diffusion layer 3 is a first carbon fiber layer, and the second heat diffusion layer 5 is a second carbon fiber layer. According to Fick's first law and Fick's second law, the rate of heat transfer is proportional to the temperature gradient. Therefore, the thickness of the first heat diffusion layer 3 is set to be greater than that of the second heat diffusion layer 5, that is, the temperature gradient between the shielding layer 4 and the magnetic layer 2 is reduced, and the temperature gradient between the shielding layer 4 and the environment on the side of the second heat diffusion layer 5 far away from the shielding layer is increased, so that the shielding layer 4 is prompted to transfer heat to the second heat diffusion layer 5 after absorbing the harmonic magnetic field to generate high temperature, and the heat transfer speed is increased to prevent the shielding layer 4 from transferring heat to the magnetic layer 2. At the same time, because the first heat diffusion layer 3 itself is not an insulating layer or a heat-insulating layer, it can absorb part of the heat of the shielding layer 4 and the magnetic layer 2 while preventing the shielding layer 4 or the magnetic layer 2 from local overheating, and slow down the heating rate of the shielding layer 4. The thermal conductivity coefficient of the first heat diffusion layer 3 along its own extension direction is greater than the thermal conductivity coefficient along its own thickness direction. Its thickness direction is the direction from the magnetic layer 2 to the shielding layer 4, and its extension direction is perpendicular to the thickness direction.

[0036] Optionally, the first heat diffusion layer 3 is interference fit with the magnetic layer 2. Optionally, the second heat diffusion layer 5 is interference fit with the shielding layer 4. The first heat diffusion layer 3 acts as a sheath to provide a certain pre-pressure for the magnetic layer to prevent the magnetic layer 2 from being separated from the shaft when the rotor rotates at high speed, and when there is a permanent magnet in the magnetic layer, to prevent the permanent magnet from being torn into multiple fragments under the action of centrifugal force.

[0037] Optional, such as Figure 1 As shown, the magnetic layer 2 is an annular permanent magnet; at this time, the shielding layer 4 is a whole, a mounting hole is opened in the middle of the annular permanent magnet, the rotating shaft passes through the mounting hole, and magnetic steel glue is arranged between the permanent magnet and the rotating shaft for connecting the permanent magnet and the rotating shaft.

[0038] Or, if Figure 2 As shown, the magnetic layer 2 includes a fixing device 21 and a permanent magnet 22. The fixing device 21 is fixedly sleeved on the rotating shaft 1. The fixing device 21 is provided with a mounting groove on the outer surface away from the rotating shaft 1, and the permanent magnet 22 is installed in the mounting groove. The fixing device 21 can be interference fit with the rotating shaft, so as to be pressed on the rotating shaft. The size of the mounting groove on the fixing device 21 is smaller than the size of the permanent magnet 22, so that the fixing device 21 and the permanent magnet 22 are interference fit, thereby providing pre-pressure for the permanent magnet 22. The permanent magnet 22 is resistant to compression but not to tension. By adding pre-pressure, the permanent magnet is prevented from breaking. The fixing device 21 and the permanent magnet 22 can be installed together to form a circular ring structure. The first heat diffusion layer 3, the shielding layer 4 and the second heat diffusion layer 5 can all be circular ring structures, nested together.

[0039] Optionally, the magnetic layer 2 includes a fixture 21 and a permanent magnet 22, and the fixture 21 is made of a heat storage material. In this case, the fixture made of the heat storage material can absorb the heat generated by the permanent magnet 22 to prevent the permanent magnet from overheating. For example, a phase change heat storage material can be used, and the phase change temperature of the phase change heat storage material is 5-10°C lower than the demagnetization temperature of the permanent magnet 22. When the temperature of the permanent magnet 22 rises, its temperature will be transferred to the fixture 21. When the temperature of the permanent magnet 22 is about to reach its corresponding demagnetization temperature, the fixture undergoes a phase change to accelerate the absorption of heat from the permanent magnet 22, and the phase change process will produce a certain volume change. The fixture 21 is made of a material whose volume increases during the phase change. When the temperature of the permanent magnet 22 rises to near the demagnetization temperature, it means that the motor has been used for a long time and the operating intensity is high. At this time, the fixing device 21 undergoes a phase change and increases in volume. This can increase the pressure between the permanent magnet 22 and the fixing device 21, thereby preventing the permanent magnet 22 from breaking due to long-term and high-intensity use of the rotor. Increasing the pressure between the two can reduce the gap between the permanent magnet 22 and the fixing device 21, increase the contact area between each other, and further improve the heat conduction efficiency. It should be noted that the volume change of the fixing device during the phase change should not be too large. Preferably, the volume change is not greater than 1% to prevent other layers from breaking.

[0040] Optionally, in the present application, the permanent magnet includes a neodymium iron boron magnet and / or a samarium cobalt magnet. These two types of magnets have strong magnetism, good magnetic retention, and high demagnetization temperature. Optionally, the shielding layer 4 is made of metal material. Specifically, the shielding layer 4 is made of copper. Optionally, the thickness of the shielding layer 4 is greater than 0.03mm and less than 1.5mm. Within a certain range of shielding layer thickness, the effect is more obvious as the thickness increases, but when the thickness is too small (such as less than 0.03mm), the eddy current electric density in the shielding layer increases sharply. When the thickness is too large (such as greater than 1.5mm), the improvement effect is no longer increased, but instead occupies the space of the high-strength protective cover and the weight of the rotor. Therefore, in order to prevent excessive eddy current loss from being induced in the shielding layer, affecting its effect of reducing the rotor eddy current loss, and not affecting the thickness of the protective cover, the shielding layer should ensure a certain thickness.

[0041] In order to better illustrate the beneficial effects of the present application, a preferred embodiment is proposed below.

[0042] The shielding layer in the rotor proposed in the present application is made of a high-conductivity metal material, preferably a copper shielding layer. A carbon fiber layer as a first heat diffusion layer is arranged between the shielding layer and the magnetic layer. A second heat diffusion layer is arranged on the side of the shielding layer away from the first heat diffusion layer. Preferably, the carbon fiber thickness of the second heat diffusion layer is less than the carbon fiber thickness of the first heat diffusion layer, so that the heat in the shielding layer is more easily transferred out.

[0043] In this embodiment, the motor rotor is mainly composed of a rotating shaft, a permanent magnet, a shielding layer and two carbon fiber layers.

[0044] Among them, the permanent magnet is made of neodymium iron boron or samarium cobalt material, the magnetic steel is of an annular structure, and its inner surface is bonded to the rotating shaft by a special magnetic steel glue; then a carbon fiber sheath is tied to the outer surface of the magnetic steel, that is, the first heat diffusion layer; the shielding layer is made of high conductivity metal material, preferably a copper shielding layer, and the shielding layer is covered on the outer surface of the inner carbon fiber sheath, and can be connected through a small gap, transition or interference; the thickness of the shielding layer is h, between 0.03mm﹤h﹤1.5mm; in the present application, the shielding layer not only shields the electromagnetic harmonics entering the permanent magnet to a large extent, reduces the eddy current loss on the surface of the permanent magnet, but also improves the heat dissipation efficiency in the shielding layer itself.

[0045] The present application also proposes a permanent magnet motor, comprising any motor rotor proposed in the present application.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A motor rotor, characterized in that: include: Rotating shaft (1); A magnetic layer (2), the magnetic layer (2) being fixedly sleeved on the rotating shaft (1); A first heat diffusion layer (3) is coated on the outer surface of the magnetic layer (2) on a side away from the rotating shaft (1) and is used to prevent the shielding layer (4) from being locally overheated; The shielding layer (4) is coated on a surface of the first heat diffusion layer (3) on a side away from the magnetic layer; The magnetic layer (2) comprises a fixing device (21) and a permanent magnet (22); the fixing device (21) is fixedly sleeved on the rotating shaft (1); a mounting groove is provided on an outer surface of the fixing device (21) on a side away from the rotating shaft (1); and the permanent magnet (22) is interference-mounted in the mounting groove; The fixing device (21) is made of heat storage material, and the volume of the fixing device (21) increases as the temperature increases.

2. The motor rotor according to claim 1, characterized in that: A first thermal conductivity of the first heat diffusion layer (3) along a thickness direction is smaller than a second thermal conductivity of the first heat diffusion layer along an extension direction.

3. The motor rotor according to claim 1, characterized in that: The first heat diffusion layer (3) is a first carbon fiber layer, the radial direction of the first carbon fiber layer is parallel to the thickness direction of the first heat diffusion layer (3), and the fiber direction of the first carbon fiber layer is parallel to the extension direction of the first heat diffusion layer (3).

4. The motor rotor according to any one of claims 1 to 3, characterized in that: Also includes: A second heat diffusion layer (5); The second heat diffusion layer (5) is coated on the outer surface of the shielding layer (4) on a side away from the magnetic layer (2).

5. The motor rotor according to claim 4, characterized in that: The second heat diffusion layer (5) is a second carbon fiber layer, the radial direction of the second carbon fiber layer is parallel to the thickness direction of the second heat diffusion layer, and the fiber direction of the second carbon fiber layer is parallel to the extension direction of the second heat diffusion layer.

6. The motor rotor according to claim 5, characterized in that: A plurality of metal heat-conducting members are arranged in the second carbon fiber layer. The metal heat-conducting members extend in a radial direction of the second carbon fiber layer and are used to improve the thermal conductivity of the second carbon fiber layer in the radial direction.

7. The motor rotor according to claim 4, characterized in that: The first heat diffusion layer and the second heat diffusion layer are made of the same material, and the thickness of the first heat diffusion layer (3) is greater than the thickness of the second heat diffusion layer (5).

8. The motor rotor according to claim 1, characterized in that: The first heat diffusion layer (3) and the magnetic layer (2) are interference fit.

9. The motor rotor according to any one of claims 1 to 3 or 5 to 8, characterized in that: The permanent magnet (22) is a ring-shaped structure.

10. The motor rotor according to claim 9, characterized in that: The permanent magnets include neodymium iron boron magnets and / or samarium cobalt magnets.

11. The motor rotor according to any one of claims 1-3, 5-8 or 10, characterized in that: The thickness of the shielding layer (4) is greater than 0.03 mm and less than 1.5 mm.

12. A permanent magnet motor, characterized in that: It comprises a motor rotor as claimed in any one of claims 1 to 11.

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