Motor rotor and permanent magnet motor

Abstract

The utility model relates to the technical field of motors, in particular to a motor rotor and a permanent magnet motor. The motor rotor comprises a rotor body, a plurality of magnetic steel groups are uniformly arranged in the circumferential direction in the rotor body, and the magnetic steel groups are arranged corresponding to magnetic poles of the rotor body; each magnetic steel group comprises at least two magnetic steel units, and the magnetic steel units are sequentially arranged along the radial direction of the rotor body; each magnetic steel unit comprises two sub magnetic steels which are arranged at an included angle, the distance between the first ends of the two sub magnetic steels is greater than the distance between the second ends of the two sub magnetic steels, the first ends of the sub magnetic steels are one ends far away from the center of the rotor body, and the second ends of the sub magnetic steels are one ends close to the center of the rotor body; the residual magnetisms of the magnetic steel units in the magnetic steel group are different; according to the motor rotor provided by the utility model, the overall heat dissipation effect of the magnetic steel is good, and the permanent magnet torque, the peak power and the motor efficiency are all improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to motor technical field, concretely relates to a motor rotor and permanent magnet motor. BACKGROUND

[0002] Permanent magnet synchronous motor rotor embeds permanent magnet, and permanent magnet provides rotor magnetic field, and mutual action with stator magnetic field, output power, torque.

[0003] For permanent magnet synchronous motor rotor, the existing permanent magnet synchronous motor rotor generally only has single layer magnetic steel along the radial direction, not only makes the heat dissipation effect of magnetic steel whole is poor, and makes all magnetic steel remanence must be same, thereby is unfavorable to the improvement of motor performance. SUMMARY

[0004] In view of above prior art's shortcoming, the utility model discloses a motor rotor and permanent magnet motor, not only improve the heat dissipation effect of magnetic steel whole, simultaneously still optimize the space of motor rotor, improve permanent magnet torque, peak power and motor efficiency.

[0005] To realize above-mentioned purpose and other relative purposes, the utility model provides a motor rotor, including:

[0006] Rotor body, the circumferential direction in the rotor body is evenly arranged with multiple magnetic steel groups, and each magnetic steel group is correspondingly arranged with the magnetic pole of the rotor body;

[0007] Each magnetic steel group includes at least two magnetic steel units, and each magnetic steel unit is sequentially arranged along the radial direction of the rotor body;

[0008] Each magnetic steel unit includes two sub-magnetic steels arranged at an angle, the interval of the first end of the two sub-magnetic steels is greater than the interval of the second end of the two sub-magnetic steels, the first end of the sub-magnetic steel is away from the center of the rotor body, and the second end is close to the center of the rotor body;And the remanence of each magnetic steel unit in the magnetic steel group is different.

[0009] In an embodiment of the utility model, the rotor body includes multiple magnetic steel grooves, and each sub-magnetic steel is one-to-one correspondingly arranged in the magnetic steel groove;

[0010] And there is a gap between the two ends of the magnetic steel groove and the sub-magnetic steel, and the gap is filled with a non-magnetic structure for fixing the sub-magnetic steel.

[0011] In an embodiment of the utility model, the magnetic steel unit close to the center of the rotor body is larger in size than the magnetic steel unit away from the center of the rotor body;The size includes thickness and / or length size.

[0012] In an embodiment of the utility model, each sub magnetic steel is square.

[0013] In an embodiment of the utility model, the residual magnetism of each sub magnetic steel is greater than 0.90T.

[0014] In an embodiment of the utility model, the included angle between the sub magnetic steel of each magnetic pole unit and the radial bisector of the corresponding magnetic pole is between 30 DEG and 70 DEG.

[0015] In an embodiment of the utility model, each magnetic pole unit in the same magnetic steel group is arranged non-parallelly, and the opening of the magnetic pole unit close to the rotor body center is smaller than the opening of the magnetic pole unit far from the rotor body center.

[0016] In an embodiment of the utility model, the spacing between the two sub magnetic steels of the magnetic pole unit located in the inner layer is smaller than the spacing between the two sub magnetic steels of the magnetic pole unit located in the outer layer.

[0017] In an embodiment of the utility model, each magnetic pole unit is symmetrical about the rotor body center, and the two sub magnetic steels of each magnetic pole unit are arranged symmetrically about the radial bisector of the magnetic pole.

[0018] To achieve the above object and other related objects, the utility model provides a permanent magnet motor, which comprises the motor rotor.

[0019] In summary, the radial arrangement of the multi-layer magnetic pole unit can realize more efficient and uniform magnetic field conversion, so that the magnetic field distribution is more concentrated, thereby improving the magnetic resistance and efficiency of the motor; The multi-layer magnetic pole unit structure helps to disperse the heat generated by the magnetic steel, avoids local overheating, and at the same time enhances the heat dissipation capacity, so that the motor operates at the best working temperature; The two sub magnetic steels of each magnetic pole unit are arranged at an included angle, which reduces the friction between the rotor and the stator, reduces the noise and vibration of the machine, and is beneficial to improve the running stability of the motor; At the same time, the residual magnetism of the multiple magnetic pole units in each magnetic pole is different, which will cause the magnetic chain to be different, so that the permanent magnet torque of the motor is improved, the peak power is improved, the torque current ratio is improved, and the motor efficiency is improved, which is helpful to improve the overall performance of the motor. ACCURACY

[0020] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 is a schematic diagram of a motor rotor structure in an optional embodiment of the present application;

[0022] Figure 2 is a schematic diagram of a structure of three sub-magnetic steels in an optional embodiment of the present application;

[0023] Figure 3 is a schematic diagram of a structure of each magnetic steel group having two magnetic steel units in an optional embodiment of the present application;

[0024] Element number explanation: rotor body 100, magnetic steel group 10, magnetic pole 101, magnetic steel unit 11, sub-magnetic steel 111, first end 1111, second end 1112, magnetic steel slot 112, radial bisector M. DETAILED DESCRIPTION

[0025] The present application will be described in more detail by the following specific examples. Other advantages and effects of the present application can be easily understood by those skilled in the art from this disclosure. The present application can also be implemented or applied in other different specific embodiments, and each detail in the specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. It should also be understood that the terms used in the embodiments of the present application are for describing specific specific embodiments, not for limiting the protection scope of the present application. The test methods not specified in the following embodiments are usually performed under conventional conditions or according to the conditions recommended by the manufacturers.

[0026] Please refer to Figures 1-3 It should be noted that the structures, proportions, sizes, etc. shown in the drawings of the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and do not have technical significance to limit the conditions under which the present application can be implemented. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "up", "down", "left", "right", "middle" and "one" in the specification are only for the convenience of clear description, not for limiting the scope of the present application, and the change or adjustment of the relative relationship without substantially changing the technical content is also considered as the scope of the present application.

[0027] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified herein, both endpoints of each numerical range and any value between the endpoints may be used. Unless otherwise defined, all technical and scientific terms used in this utility model are consistent with the prior art as understood by those skilled in the art and the description of this utility model. Any prior art methods, equipment, and materials similar or equivalent to those described in the examples of this utility model may also be used to implement this utility model.

[0028] See also Figure 1 The present invention provides a motor rotor, comprising a rotor body 100; a plurality of magnetic steel groups 10 are evenly arranged in the circumferential direction of the rotor body 100, and each magnetic steel group 10 is arranged corresponding to a magnetic pole 101 of the rotor body 100;

[0029] Each of the magnetic steel groups 10 includes at least two magnetic steel units 11 , and each of the magnetic steel units 11 is sequentially arranged along the radial direction of the rotor body 100 , and each of the magnetic steel units 11 is symmetrical about the center of the rotor body 100 ;

[0030] Each of the magnetic steel units 11 includes two sub-magnets 111 arranged at an angle, and the distance between the first ends 1111 of the two sub-magnets 111 is greater than the distance between the second ends 1112 of the two sub-magnets 111. The first end 1111 of the sub-magnet 111 is the end away from the center 100 of the rotor body, and the second end 1112 is the end close to the center 100 of the rotor body, so that each of the magnetic steel units 11 is V-shaped or C-shaped. Each of the V-shaped or C-shaped magnetic steel units 11 has an opening, that is, the opening direction of the magnetic steel unit 11 is away from the center of the rotor body 100. The residual magnetism of each of the magnetic steel units 11 in the magnetic steel group 10 is different.

[0031] It should be noted that the magnets in this case are all made of residual magnetic materials, such as ferrite sintered magnets, ferrite bonded magnets, and other magnets. The individual magnet groups 10 in this case are arranged along the circumference of the rotor body 100, alternating between north and south poles, and the number of magnet groups 10 is an even number. Remanence refers to the magnetism that a magnet retains in the absence of an external magnetic field. The presence of remanence is fundamental to motor operation, ensuring that the rotor body 100 can rotate stably in the magnetic field generated by the stator coils, thereby continuously and efficiently outputting power. Higher remanence means more magnetism a magnet retains after demagnetization. Flux linkage is a critical parameter in a motor, proportional to magnetic flux. An increase in remanence leads to an increase in magnetic flux, which in turn increases flux linkage. In a permanent magnet motor, torque is proportional to the product of flux linkage and current. Therefore, as flux linkage increases, if the current remains constant, the motor's torque also increases accordingly. Peak power refers to the maximum power a motor can output under specific conditions. Increased torque enables the motor to generate greater torque at the same current, thereby increasing peak power. The torque-to-current ratio refers to the torque generated per unit current. When torque increases while current remains constant or decreases relatively, the torque-to-current ratio increases, thereby improving motor efficiency because the same current can produce greater torque. Therefore, when the residual magnetization of the magnet is high, the flux linkage increases, leading to higher motor torque; while maintaining the current constant, the motor's peak power is increased. Furthermore, because the rate of increase in torque can exceed the rate of increase in current (or if the current remains constant), the torque-to-current ratio also increases, further improving motor efficiency.

[0032] Furthermore, each of the magnetic steel groups 10 includes at least two magnetic steel units 11, and each of the magnetic steel units 11 is V-shaped or C-shaped or other shapes that meet the characteristic requirements of this case. Among the multiple magnetic steel units 11 of each of the magnetic steel groups 10, at least one of the magnetic steel units 11 is V-shaped or at least one of the magnetic steel units 11 is C-shaped, that is, V-shaped magnetic steel units 11 and C-shaped magnetic steel units 11 may exist in a magnetic steel group 10 at the same time, so that magnetic steel units 11 of different shapes can be arranged according to actual needs.

[0033] In this case, each of the magnetic steel groups 10 includes at least two magnetic steel units 11, such as Figure 3 As shown, each of the magnetic steel groups 10 includes two magnetic steel units 11; Figure 1 As shown, each magnetic steel group 10 includes three magnetic steel units 11 , that is, each magnetic steel group 10 in this embodiment may include two magnetic steel units 11 , three magnetic steel units 11 , or more magnetic steel units 11 .

[0034] like Figures 1-2As shown, the magnetic pole 101 of the rotor body 100 is provided with three layers of magnetic steel units 11, as shown in FIG. Figure 2 The figure shows a schematic structural diagram of the sub-magnetic steel 111 in the three-layer magnetic steel unit 11. The three-layer magnetic steel unit 11 is divided into layer A, layer B and layer C, wherein layer C is closer to the center of the rotor body 100 and layer A is farther away from the center of the rotor body 100.

[0035] Furthermore, in this case, because the remanence of the multiple magnetic steel units 11 in each magnetic pole 101 is different, resulting in different magnetic flux linkages, the permanent magnet torque of the motor is increased, thereby increasing the peak power. The torque-to-current ratio is improved, the motor efficiency is improved, and the overall performance of the entire motor is improved. Specifically, as shown in Table 1 below, under the conditions of maintaining the same current, voltage, and motor temperature, the average value of the sum of the different remanence values ​​of the three layers of magnetic steel units 11 is the same as the remanence value of the three layers of magnetic steel units 11 with the same remanence. By comparison, it can be seen that the motor with three layers of magnetic steel units 11 having different remanence improves the peak torque, peak power, and operating efficiency of the motor.

[0036] Motor type Motor with three-layer magnetic steel units with same residual magnetism Motor with three-layer magnetic steel units with different residual magnetism Residual magnetism of A layer magnetic steel x = 1.30 T x = 1.20 T Residual magnetism of B layer magnetic steel y = 1.30 T x = 1.30 T Residual magnetism of C layer magnetic steel z = 1.30 T x = 1.40 T Peak torque 400 Nm 414 Nm Peak power 200 kW 213 kW Operating efficiency 95.4％ 95.6％

[0037] Table 1

[0038] In this case, each of the magnetic steel units 11 includes two sub-magnets 111 arranged at an angle, and the opening direction of the magnetic steel unit 11 is away from the center of the rotor body 100. For example, each magnetic steel unit 11 is V-shaped, and the opening of the magnetic steel unit 11 is also a V-shaped opening, which can achieve more efficient magnetic field conversion and energy transfer, making the magnetic field distribution more concentrated, thereby improving the magnetic resistance and efficiency of the motor; at the same time, the high linear magnetic characteristics of the V-shaped magnetic steel unit 11 also help the motor achieve a higher speed and output power, further improving the overall efficiency of the equipment; at the same time, the rotor of the V-shaped magnetic steel unit 11 reduces the friction between the rotor and the stator, Thereby, the noise and vibration of the machine are reduced, which is beneficial to improving the running stability of the motor; the rotor of the V-shaped magnetic steel unit 11 has the advantage of high torque density, so that the motor can generate greater torque under the same current input; at the same time, the V-shaped magnetic steel unit 11 of this case is suitable for the high-speed new energy vehicle motor requirements, and the V-shaped magnetic steel unit 11 is made into an embedded structure, which has strength advantages; and the magnetic steel is made into a square shape, which is easy to prepare the magnetic steel; in terms of electromagnetics, the V-shaped magnetic steel has the advantages of high salient pole ratio, high torque power, low torque pulsation, and easy optimization; at the same time, arranging multiple layers of magnetic steel units 11 along the radial direction can improve the overall heat dissipation efficiency of the magnetic steel 11.

[0039] In this embodiment, the magnetic steel units 11 are arranged radially. The remanence of the magnetic steel units 11 within different magnetic steel slots 112 within a stack of cores varies. Each magnetic pole 101 of the motor rotor in this embodiment is arranged with three layers of magnetic steel units 11. By varying the remanence of the magnetic steel within different magnetic steel slots 112 and combining multiple V-shaped magnetic steel slots 112, this embodiment significantly increases the space available for motor optimization and reduces motor cost. This optimized motor achieves high operating efficiency, high torque density, and high power density, and optimizes motor NVH performance, such as torque ripple and radial force at various orders.

[0040] See also Figure 1 As an optional embodiment of the present invention, the rotor body 100 includes a plurality of magnetic steel slots 112, and each of the sub-magnetic steels 111 is disposed in the magnetic steel slot 112 in a one-to-one correspondence;

[0041] There is a gap between the two ends of the magnetic steel slot 112 and the sub-magnetic steel 111 , and the gap is filled with a non-magnetic conductive structure that fixes the sub-magnetic steel 111 .

[0042] It should be noted that each sub-magnet 111 described in this case occupies a separate magnetic steel slot 112; in order to avoid demagnetization of the parts of the sub-magnet 111 close to the two ends of the magnetic steel slot 112, this case creates a gap between the two ends of the magnetic steel slot 112 and the corresponding sub-magnet 111, and fills the gap with a non-magnetic conductive structure. This can, on the one hand, increase the mechanical strength of the motor rotor, and on the other hand, improve the stability of the sub-magnet 111 in the magnetic steel slot 112, thereby avoiding displacement or sliding.

[0043] See also Figure 2 As an optional embodiment of the present invention, the magnetic steel unit 11 close to the center of the rotor body 100 is larger in size than the magnetic steel unit 11 away from the center of the rotor body 100; the size includes thickness and / or length.

[0044] It should be noted that the length dimension refers to Figure 1 As shown, the length and thickness directions of the sub-magnetic steel 11 are perpendicular to the length direction, while the width direction of the sub-magnetic steel 11 is the axial direction of the rotor body 100. The width direction of the sub-magnetic steel 11 is perpendicular to the length and thickness directions. Due to the shape restriction of the rotor punching where each magnetic pole 101 is located, this case makes the magnetic steel unit 11 close to the center of the rotor body 100 larger in size than the magnetic steel unit 11 away from the center of the rotor body 100. On the one hand, more magnetic steel units 11 can be arranged at each magnetic pole 101, thereby increasing the total remanence value, increasing the magnetic flux, and thereby increasing the motor torque, peak power and efficiency.

[0045] See also Figure 2As an optional embodiment of the present invention, each of the sub-magnetic steels 111 is square in shape.

[0046] It should be noted that the square-shaped sub-magnet 111 can have a higher magnetic flux in a specific direction, which is beneficial to improving the output torque and efficiency of the motor. The square-shaped sub-magnet 111 helps to better optimize the magnetic circuit design, making the magnetic flux more concentrated and reducing leakage flux, thereby improving the performance of the motor; the square-shaped sub-magnet 111 is easier to process and assemble than magnets of other shapes, which helps to reduce production costs and improve production efficiency.

[0047] See also Figure 1 As an optional embodiment of the present invention, the remanence of each sub-magnetic steel 111 is greater than 0.90T.

[0048] It should be noted that a specific numerical threshold is set for the remanence of the sub-magnet 111, for example, greater than 0.90 Tesla T, so as to ensure that all sub-magnets 111 used meet certain performance standards, which helps to ensure the quality and consistency of the final motor rotor; higher remanence is conducive to ensuring the stability and efficiency of the motor rotor.

[0049] See also Figure 1 As an optional embodiment of the present invention, the angle between the sub-magnetic steel 111 of each magnetic steel unit 11 and the radial bisector M of the corresponding magnetic pole is between 30° and 70°.

[0050] It should be noted that each of the magnetic steel units 11 is symmetrical about the center of the rotor body 100, and the two sub-magnets 111 of each magnetic steel unit 11 are symmetrical about the radial bisector M of the motor rotor at the magnetic steel unit 11. The radial bisector M passes through the center of the rotor body 100 and faces the radial direction of the rotor body 100. In this embodiment, the angle between the sub-magnets 111 of each magnetic steel unit 11 and the radial bisector M of the corresponding magnetic pole is set between 30° and 70°. Figure 1 As shown, that is, 70°≥a2≥a1≥30°, that is, the angle between the two sub-magnets 111 of the magnetic steel unit 11 is between 60° and 140°, the angle between the two sub-magnets 111 of the third-layer magnetic steel unit 11 is greater than or equal to the angle between the two sub-magnets 111 of the second-layer magnetic steel unit 11, and the angle between the two sub-magnets 111 of the second-layer magnetic steel unit 11 is greater than or equal to the angle between the two sub-magnets 111 of the third-layer magnetic steel unit 11. Such a constraint setting can effectively improve the output torque of the motor, sort out the magnetic circuit, reduce the torque pulsation of the motor, and improve the performance of the motor.

[0051] See also Figure 1As an optional embodiment of the present invention, the magnetic steel units 11 in the same magnetic steel group 10 are not arranged in parallel, and the opening of the magnetic steel unit 11 close to the center of the rotor body 100 is smaller than the opening of the magnetic steel unit 11 away from the center of the rotor body 100.

[0052] It should be noted that when the angle between the two sub-magnets 111 of each magnetic steel unit 11 is between 30° and 70°, the magnetic steel units 11 in the same magnetic steel group 10 are not arranged in parallel, and the opening of the magnetic steel unit 11 close to the center of the rotor body 100 is smaller than the opening of the magnetic steel unit 11 away from the center of the rotor body 100. On the one hand, it is beneficial to the specific structural arrangement of the motor rotor, and on the other hand, it can obtain the largest possible power torque, thereby facilitating the improvement of motor performance.

[0053] See also Figure 1 As an optional embodiment of the present invention, the distance between the two sub-magnets 111 of the magnetic steel unit 11 located in the inner layer is smaller than the distance between the two sub-magnets 111 of the magnetic steel unit 11 located in the outer layer, which is beneficial to improving the strength of the high-speed motor rotor.

[0054] See also Figure 1 As an optional embodiment of the present invention, the two sub-magnets 111 of each magnetic steel unit 11 are symmetrically arranged about the radial bisector M of the magnetic pole 101, thereby improving the sinusoidality of the motor rotor magnetic field and improving the motor performance.

[0055] See also Figure 1 As an optional embodiment of the present invention, the two sub-magnets 111 of each magnetic steel unit 11 are symmetrically arranged about the radial center line of the magnetic pole 101, thereby optimizing the magnetic circuit of each magnetic pole 101, improving the motor output torque, and reducing torque pulsation.

[0056] See also Figure 1 As an optional embodiment of the present invention, among the multiple magnetic steel units 11 in the same magnetic steel group 10, the residual magnetism difference between two adjacent magnetic steel units 11 is greater than a preset value. An appropriate residual magnetism difference is conducive to different magnetic flux linkages, thereby improving the permanent magnet torque of the motor and thus improving the peak power; the torque-to-current ratio is improved, the motor efficiency is improved, and thus the overall performance of the entire motor is improved; for example, the preset value can be 0.1T.

[0057] As an optional embodiment of this case, the remanence of each sub-magnetic steel should be less than 1.50T, so as to reduce material costs.

[0058] The motor rotor provided by the utility model can be used not only for oil-cooled motors, but also for water-cooled motors and air-cooled motors, and is equally applicable to high-voltage motors above 600V and low-voltage motors below 500V.

[0059] See also Figure 1 The utility model provides a permanent magnet motor, including the motor rotor, which is beneficial to improving the overall performance of the permanent magnet motor.

[0060] In summary, the utility model effectively overcomes some practical problems in the prior art and thus has high utilization value and use significance.

[0061] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed in the present invention are intended to be covered by the claims of the present invention.

Claims

1. A motor rotor, characterized in that: include: A rotor body, wherein a plurality of magnetic steel groups are evenly arranged in a circumferential direction within the rotor body, and each magnetic steel group is arranged corresponding to a magnetic pole of the rotor body; Each of the magnetic steel groups includes at least two magnetic steel units, and each of the magnetic steel units is arranged in sequence along the radial direction of the rotor body; Each of the magnetic steel units includes two sub-magnets arranged at an angle, the spacing between the first ends of the two sub-magnets is greater than the spacing between the second ends of the two sub-magnets, the first end of the sub-magnet is the end away from the center of the rotor body, and the second end is the end close to the center of the rotor body; and the remanence of each of the magnetic steel units in the magnetic steel group is different.

2. The motor rotor according to claim 1, characterized in that: The rotor body includes a plurality of magnetic steel slots, and each of the sub-magnetic steels is arranged in the magnetic steel slot in a one-to-one correspondence; There is a gap between the two ends of the magnetic steel slot and the sub-magnetic steel, and the gap is filled with a non-magnetic conductive structure for fixing the sub-magnetic steel.

3. The motor rotor according to claim 1, characterized in that: The magnetic steel unit close to the center of the rotor body is larger in size than the magnetic steel unit far from the center of the rotor body; the size includes thickness and / or length.

4. The motor rotor according to claim 1, characterized in that: Each of the sub-magnets is square in shape.

5. The motor rotor according to claim 1, characterized in that: The remanence of each sub-magnetic steel is greater than 0.90T.

6. The motor rotor according to claim 1, characterized in that: The included angle between the sub-magnetic steel of each magnetic steel unit and the radial bisector of the corresponding magnetic pole is between 30° and 70°.

7. The motor rotor according to claim 6, characterized in that: The magnetic steel units in the same magnetic steel group are not arranged in parallel, and the opening of the magnetic steel unit close to the center of the rotor body is smaller than the opening of the magnetic steel unit far from the center of the rotor body.

8. The motor rotor according to claim 6, characterized in that: The distance between the two sub-magnetic steels of the magnetic steel unit located in the inner layer is smaller than the distance between the two sub-magnetic steels of the magnetic steel unit located in the outer layer.

9. The motor rotor according to claim 1, characterized in that: Each of the magnetic steel units is symmetrical about the center of the rotor body, and the two sub-magnets of each magnetic steel unit are symmetrically arranged about the radial bisector of the magnetic pole.

10. A permanent magnet motor comprising the motor rotor according to any one of claims 1 to 9.

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