Permanent magnet of external rotor motor

Abstract

The utility model relates to a permanent magnet of an external rotor motor, the motor comprises a magnetic conductive ring and permanent magnets, the permanent magnets are geometries distributed in an axial symmetry mode, the permanent magnets are installed on the inner ring of the magnetic conductive ring in an end-to-end splicing mode, the end-to-end splicing edge of two adjacent permanent magnets is provided with a concave structure, and the permanent magnets are contacted at the convex positions of the end-to-end splicing edge. The range of the ratio of the area S of the projection plane of the permanent magnet in the magnetizing direction to the area T of the minimum outer quadrilateral of the projection plane of the permanent magnet in the magnetizing direction is 0.75-0.95, namely, the range of S / T is 0.75-0.95. The permanent magnet structure has the advantages of material saving, light weight, cost reduction, guarantee of the installation stability of the permanent magnet body, symmetrical distribution of magnetic field distribution, high-efficiency installation, low inter-pole magnetic leakage, small cogging torque, good sine performance of magnetic field distribution of the whole machine, simple magnetizing process of the permanent magnet body, and obvious improvement of the utilization rate of magnetic energy of the motor. The efficiency of the motor is optimized and improved, and the motor assembly process is simple and efficient.

Description

Technical Field

[0001] The utility model relates to the technical field of external rotor motors, and specifically discloses a permanent magnet of an external rotor motor. Background Art

[0002] As a convenient and economical means of transportation, electric vehicles are widely used in people's daily travel. The drive motor of an electric vehicle, that is, the hub motor we usually call, essentially belongs to an external rotor motor.

[0003] In this regard, motor manufacturers have done a lot of research on the lightweight and efficiency improvement of hub motors, especially in the design of motor permanent magnets. For example, there is a uniformly spaced convex structure on the magnetic conduction ring to separate two adjacent permanent magnets; there are magnetic isolation teeth arranged on both end covers to ensure the effective spaced installation of the motor permanent magnets. However, although the above measures have achieved the spaced (i.e., non-continuous splicing) adhesive installation of the motor, they have also brought complexity and difficulty in the installation process. For example, when setting a spaced structure on the magnetic conduction ring, the processing difficulty of the magnetic conduction ring increases sharply, and the magnetic steel needs to be positioned and installed. Also, when setting a spaced tooth structure on the end cover, due to the slender spaced teeth, they are prone to breakage, and the processing accuracy is difficult to control and the processing is difficult. These technical problems have not been well solved. Of course, there are also permanent magnets that use magnetic isolation tooling to achieve the gap installation between permanent magnets in the market. This method has long been applied in hub motors. As a result, due to the insufficient adhesive force of conventional room-temperature curing glue to meet the direct bonding of permanent magnets, there has been a batch of magnetic steel shedding. However, some manufacturers have used high-adhesion high-temperature curing glue, which has brought problems such as high-temperature energy consumption and post-magnetization of magnetic steel, and the assembly cost has increased sharply. Therefore, the methods of the above-mentioned hub motor manufacturers for saving the amount of permanent magnet used are not satisfactory, and the products have high risks of safety and stability, difficult processing of spare parts, and high manufacturing costs.

[0004] Theoretically speaking, through the spaced installation of permanent magnets, the interpolar leakage magnetic can be effectively reduced, and at the same time, the cogging torque of the motor can be effectively reduced, the magnetic field distribution can be optimized to conform to sine, the electromagnetic noise of the motor can be reduced, and the motor efficiency in the high-speed range can be increased, truly achieving cost reduction, weight reduction, and efficiency increase. However, the method of spaced installation of permanent magnets has problems such as complex installation process, large processing difficulty, and weak adhesive force of permanent magnets. Therefore, how to design the permanent magnet structure to meet the high-efficiency production process, ensure the installation strength of the permanent magnet, and reduce the amount of permanent magnet material used is the goal that the industry has been pursuing and improving, and it is also the motivation for the creation and research of this utility model. Content of the Utility Model

[0005] Aiming at the deficiencies of the prior art, the utility model discloses a permanent magnet of an external rotor motor that saves materials, has low manufacturing cost, and ensures the installation stability of the permanent magnet body.

[0006] To achieve the above object, the present utility model discloses a permanent magnet for an outer rotor motor, and its technical solution is as follows:

[0007] A permanent magnet for an outer rotor motor, the motor includes a magnetic conductive ring and a plurality of permanent magnet bodies, characterized in that: the permanent magnet bodies are geometric bodies with axisymmetric distribution, the permanent magnet bodies are installed on the inner ring of the magnetic conductive ring in a head-to-tail splicing manner, and a plurality of concave structures are provided on the head-to-tail splicing edges of two adjacent permanent magnet bodies, the permanent magnet bodies are in contact with each other at the convex parts of the head-to-tail splicing edges, and the ratio range of the area S of the projection surface of the permanent magnet body in its magnetization direction to the area T of the minimum circumscribed parallelogram of the projection surface of the permanent magnet body in its magnetization direction is 0.75 to 0.95, that is, the range of S / T is 0.75 to 0.95.

[0008] The permanent magnet body of the outer rotor motor provided by the present utility model also has the following subsidiary technical solutions:

[0009] Among them, the head-to-tail splicing edges of any one of the permanent magnet bodies are axially symmetrically distributed.

[0010] Among them, the total width of all the concave structures on any one of the head-to-tail splicing edges in the axial direction of the motor accounts for 1 / 2 of the total axial width of the permanent magnet body.

[0011] Among them, the permanent magnet body is symmetrically distributed about the center line of its axial dimension in the motor.

[0012] Among them, the concave dimension H of the concave structure is H≥0.5mm.

[0013] Among them, the values of the concave dimension H on a plurality of the concave structures are equal.

[0014] Among them, the permanent magnet body is a geometric body with a concave middle and convex axial ends or a convex middle and concave axial ends.

[0015] Among them, the permanent magnet body takes the radial direction of the motor as the magnetization direction.

[0016] Compared with the prior art, the advantages and positive effects of the present utility model are:

[0017] Through the design of the concave structure at the contact part of adjacent magnetic poles in the permanent magnet body structure of the present utility model, about 5% - 25% of rare earth permanent magnet materials are saved, achieving cost reduction and weight reduction.

[0018] The permanent magnet bodies are in contact with each other at the convex parts of the head-to-tail splicing edges, that is, the permanent magnet bodies are closely attached to each other two by two, increasing the adhesion between two adjacent permanent magnet bodies and ensuring the installation stability of the permanent magnet bodies.

[0019] By reducing the length of the contact edge between adjacent magnetic poles, the inter-pole leakage magnetic flux at the contact edge of the magnetic poles is reduced, and the utilization rate of magnetic energy is improved.

[0020] By controlling the size and distribution law of the concave, such as concave at both ends, or concave in the middle, or a design method with multiple protrusions and concavities in a serrated manner, the cogging torque is significantly reduced, the motor vibration is reduced, the electromagnetic noise is reduced, and at the same time, the sinusoidal characteristic of the magnetic flux density distribution of the motor is optimized, the efficiency of the motor is improved, and the efficiency in the high-speed range of the motor is higher.

[0021] Through the design of a symmetric geometric structure, it is ensured that the front and back sides of the permanent magnet body are of the same shape. The permanent magnet body can realize the continuous mounting of the "N / S" law (the polarities of adjacent two magnetic poles are opposite) of the motor magnetic poles through the method of "unidirectional magnetization + front and back mounting". Moreover, the manufacturing process of the permanent magnet body itself is simple and the cost is low. The installation process of the motor magnetic poles is foolproof and the production efficiency is high. In addition, the problems of installation orientation and fixed matching of asymmetric permanent magnets are solved, and free matching is realized.

[0022] Using finite element software to analyze the cogging torque, motor efficiency, magnetic flux density distribution cloud map, etc. of the in-wheel motor using the permanent magnet body, the analysis conclusion is that the structure of the permanent magnet body in the present utility model optimizes the back electromotive force waveform of the motor, reduces the amplitude of the cogging torque, reduces the harmonic noise, the efficiency in the high-speed section of the motor is increased by about 2% - 5%, the inter-pole leakage magnetic flux of the motor is effectively controlled, the leakage magnetic rate is reduced by 10% - 20%, and the utilization rate of magnetic energy is effectively improved.

[0023] The permanent magnet body structure of the present utility model saves materials, reduces weight and cost, ensures the installation stability of the permanent magnet body, has a symmetric magnetic field distribution and is conducive to efficient installation, has low inter-pole leakage magnetic flux, small cogging torque, good sinusoidal property of the whole machine magnetic field distribution, simple magnetization process of the permanent magnet body, significantly improved magnetic energy utilization rate of the motor, optimized and improved motor efficiency, and simple and efficient motor assembly process. Description of the Drawings

[0024] Figure 1 Schematic diagram of the installation structure of the permanent magnet body in Embodiment 1 of the present utility model.

[0025] Figure 2 Schematic diagram of the flat-laid expansion of the installation of the permanent magnet body in Embodiment 1 of the present utility model.

[0026] Figure 3 Schematic diagram of the three-dimensional structure of the permanent magnet body in Embodiment 1 of the present utility model.

[0027] Figure 4 Schematic diagram of the relationship between S and T of the permanent magnet body in Embodiment 1 of the present utility model.

[0028] Figure 5Schematic diagram of the installation structure of the permanent magnet body in Embodiment 2 of the present utility model.

[0029] Figure 6 Schematic diagram of the flat-laid expansion of the installation of the permanent magnet body in Embodiment 2 of the present utility model.

[0030] Figure 7 Schematic three-dimensional structure diagram of the permanent magnet body in Embodiment 2 of the present utility model.

[0031] Figure 8 Schematic diagram of the relationship between S and T of the permanent magnet body in Embodiment 2 of the present utility model.

[0032] In the figure, 1, permanent magnet body; 2, magnetic conduction ring; 3, projection plane of the permanent magnet body in its magnetization direction; 4, minimum circumscribed parallelogram of the projection plane of the permanent magnet body in its magnetization direction; 5, axis of symmetry of the head and tail splicing edge of the permanent magnet body; 6, axial dimension center line of the permanent magnet body; 11, head and tail splicing edge; 111, concave structure; B, total axial width of the permanent magnet; H, concave dimension of the concave structure; S, area of the projection plane of the permanent magnet body in its magnetization direction; T, area of the minimum circumscribed parallelogram of the projection plane of the permanent magnet body in its magnetization direction; W, width of the permanent magnet body in the splicing direction; X, motor axial direction; Y, head and tail splicing direction of the permanent magnet installation; b1, axial width of the first concave structure of the permanent magnet body; b2, axial width of the second concave structure of the permanent magnet body. Detailed implementation manners

[0033] The following are specific embodiments of the present utility model, and the technical solutions of the present utility model are further described in detail in conjunction with the accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of those skilled in the art of the present utility model, and do not limit the protection scope of the present utility model in any way.

[0034] Embodiment 1:

[0035] See Figures 1 to 4As shown in the figure, an outer-rotor hub motor permanent magnet and its installation method for an electric vehicle provided in this embodiment. The hub motor for the electric vehicle is a 10-inch motor, which includes a rotor, a stator, a support cover, and a connecting shaft. The rotor is sleeved outside the stator. The rotor includes a rim, a magnetic conductive ring 2, and a plurality of permanent magnet bodies 1. The plurality of permanent magnet bodies 1 are evenly installed on the inner ring of the magnetic conductive ring 2. The support cover is fixedly connected and installed on the axial end faces of the magnetic conductive ring 2 through screws. The stator is located between the two support covers. A connecting shaft is provided at the center of the stator, and a bearing is provided at the center of the support cover. The connecting shaft is fixedly connected to the inner hole of the bearing. In this embodiment, the inner diameter range of the magnetic conductive ring 2 is 213 - 224 mm. Preferably, the inner diameter range of the magnetic conductive ring 2 is 215 - 223 mm. Further preferably, the inner diameter range of the magnetic conductive ring 2 in this embodiment is 214.9 - 215.2 mm. In the present utility model, the expression of the permanent magnet body is equivalent to the expression of the permanent magnet in the prior art.

[0036] In the above technical solution: The permanent magnet body 1 is a geometric body with an axisymmetric distribution. The permanent magnet bodies 1 are installed on the inner ring of the magnetic conductive ring 2 in a head-to-tail splicing manner. A plurality of concave structures 111 are provided on the head-to-tail splicing edge 11 of two adjacent permanent magnet bodies 1. The plurality of concave structures 111 cause the permanent magnet body 1 to form a plurality of convex portions on the head-to-tail splicing edge 11. The convex portions of the permanent magnet body 1 on the head-to-tail splicing edge 11 are in contact with each other, that is, the permanent magnet bodies are closely attached to each other two by two, increasing the adhesion between two adjacent permanent magnet bodies 1. When the adhesion between a permanent magnet body 1 and the magnetic conductive ring 2 is not very firm, the adjacent permanent magnet body 1 abuts against it, preventing it from falling off the magnetic conductive ring 2 and ensuring the installation stability of the permanent magnet body 1. Preferably, the number of concave structures 111 of the permanent magnet body 1 in this embodiment is 1 and is located in the middle part of the axial direction of the permanent magnet body 1, that is, the convex portions of the permanent magnet body 1 in this embodiment are located at the upper and lower ends. The permanent magnet body 1 is a geometric body structure that is concave in the middle, convex at both axial ends, and approximately in the shape of a "worker" character.

[0037] In the above technical solution: Such as Figure 4As shown, the ratio range between the area S of the projection surface 3 of the permanent magnet body 1 in its magnetization direction and the area T of the smallest circumscribed parallelogram 4 of the projection surface 3 of the permanent magnet body 1 in its magnetization direction is 0.75 to 0.95, that is, the range of S / T is 0.75 to 0.95. Preferably, the range of S / T is 0.8 to 0.85. Further preferably, the range of S / T in this embodiment is 0.83 to 0.85. In this solution, by setting the concave structure 111 on the installation edge of the permanent magnet body 1, the traditional way of continuously splicing and installing the cuboid or tile-shaped or arc-shaped permanent magnet body in the inner ring of the magnetic conduction ring 2 is continued (this process is simple). On this basis, at the head and tail splicing edge 11 between adjacent permanent magnet bodies 1, a certain vacant surface is formed through the concave structure 111, and this vacant surface plays a role in reducing the magnetic leakage between adjacent magnetic poles. The magnetic leakage rate is reduced by 10% to 20%, improving the magnetic energy utilization rate. At the same time, weight reduction and cost reduction are achieved, saving about 5% to 25% of the weight of the permanent magnet body 1, and saving about 5% to 25% of the cost of the rare earth permanent magnet material required for the production of the permanent magnet body 1, realizing weight reduction and cost reduction. Another effect of this solution is that it effectively reduces the cogging torque of the motor, optimizes the magnetic flux density distribution of the motor to make it tend to be sinusoidal, and reduces the electromagnetic noise, improving the efficiency in the high-speed range by about 2% to 5% and reducing the noise by 5 - 20 dB.

[0038] In the above technical solution: Refer to Figure 4 , in this embodiment, the permanent magnet body 1 is a planar geometric body or an arc or an irregular geometric body with a certain thickness. The radial thickness range of the geometric body is 1.5 to 4 mm. Preferably, the radial thickness range is 1.5 to 2.3 mm. Further preferably, the radial thickness range in this embodiment is 1.5 to 1.8 mm. The width W of the permanent magnet body 1 in the splicing direction in this embodiment ranges from 9 to 15 mm. Preferably, the range of W is 12.4 to 12.8 mm. Further preferably, the range of W in this embodiment is 12.72 to 12.76 mm.

[0039] In the above technical solution: The head and tail splicing edges 11 of any permanent magnet body 1 are axially symmetrically distributed, that is, the permanent magnet body 1 is symmetric about the left and right center line 5. The above structure brings two advantages: On the one hand, during the magnetization stage of the permanent magnet body 1, there is no need to distinguish and magnetize the "N" and "S" magnetic pole polarities of the permanent magnet body 1, and unidirectional batch magnetization can be directly carried out. The process is simple and fast, and the fault tolerance is high. When installing the permanent magnet body 1, only by operating the front and back sides, the "N" and "S" poles of the magnetic field can be spliced in an alternating manner; on the other hand, due to the symmetry of the permanent magnet body 1, after continuous splicing and installation of the permanent magnet body 1, the magnetic field distribution is symmetric and uniform, and the motor runs smoothly.

[0040] In the above technical solution: The total width of any permanent magnet body 1 in the axial direction of the motor is simply referred to as the total axial width B of the permanent magnet 1 body. The total width of all the concave structures 111 on any head-to-tail splicing edge 11 of the permanent magnet body 1 in the axial direction of the motor accounts for 1 / 2 of the total axial width B of the permanent magnet body 1, that is Figure 4 b1 = B / 2 in Figure 4 . The range of the total axial width B of the permanent magnet body 1 in this embodiment is 16 - 50 mm. Preferably, the range of B is 18 - 35 mm. In this application, the axial direction of the motor is Figure 4 the X direction in

[0041] In the above technical solution: The permanent magnet body 1 is symmetrically distributed about the center line 6 of its axial dimension in the motor, that is, the permanent magnet body 1 is symmetric up and down. With this solution, the error tolerance of the installation of the permanent magnet body 1 can be effectively improved. That is, during installation, there is no need to distinguish between the upper and lower ends, achieving a foolproof installation, greatly improving the production efficiency. Moreover, the magnetic field of the permanent magnet body 1 is axially symmetric about the center line 6, the axial force is balanced, the vibration of the motor is reduced, and the operation is more stable.

[0042] In the above technical solution: The concave dimension H of the concave structure 111 in this embodiment is H≥0.5 mm. Preferably, H≥2 mm. Further preferably, H = 2.3 - 3 mm in this embodiment. The concave dimension H values of several concave structures 111 are equal. The permanent magnet body 1 in this embodiment is magnetized in the radial direction of the motor.

[0043] Embodiment 2:

[0044] For the technical solution in this embodiment, refer to Figures 5 to 8 . The technical solution in this embodiment is mostly the same as that in Embodiment 1. Only the different parts in this embodiment will be described in detail, and the same parts as in Embodiment 1 will not be repeated.

[0045] Refer to Figures 5 to 8 . The number of concave structures 111 of the permanent magnet body 1 in this embodiment is 2, which are respectively located at both axial ends of the permanent magnet body 1. That is, the permanent magnet body 1 is a geometric body structure that is convex in the middle, concave at both axial ends, and approximately in the shape of the Chinese character 'zhong'. When the permanent magnet bodies 1 are spliced and installed, adjacent two permanent magnet bodies 1 are in contact at the convex edge in the middle. The total width of all the concave structures 111 on the head-to-tail splicing edge 11 of the permanent magnet body 1 in this embodiment accounts for 1 / 2 of the total axial width of the permanent magnet body, that is Figure 8 b1 + b2 = B / 2 in Figure 6 The X direction in Figure 6 refers to the axial direction of the motor,

[0046] Embodiment 3:

[0047] The technical solution in this embodiment is mostly the same as that in Embodiment 1. Only the different parts will be described in detail in this embodiment, and the same parts as in Embodiment 1 will not be repeated.

[0048] In this embodiment, the number of concave structures 111 on the permanent magnet body 1 is n, where n > 2, that is, the head and tail splicing edge 11 of the permanent magnet body 1 is serrated, and when the permanent magnet bodies 1 are spliced and installed, they contact at the convex edges. The total width b1 + b2 +... + bn of all the concave structures 111 on the head and tail splicing edge 11 of the permanent magnet body 1 of this embodiment in the axial direction of the motor shaft accounts for 1 / 2 of the total axial width B of the permanent magnet body, that is, b1 + b2 +... + bn = B / 2.

[0049] The structure of the permanent magnet body of the present utility model, through the design of the concave structure at the contact part of adjacent magnetic poles, saves about 5% - 25% of rare earth permanent magnet materials, achieving cost reduction and weight reduction. Through the outward convex parts in contact with each other between adjacent permanent magnet bodies, that is, the permanent magnet bodies are closely attached to each other pairwise, the adhesion between adjacent two permanent magnet bodies is increased, ensuring the installation stability of the permanent magnet body. By reducing the length of the contact edge between adjacent two magnetic poles, the inter-pole leakage magnetic flux at the contact edge of the magnetic poles is reduced, improving the magnetic energy utilization rate. By controlling the size and distribution law of the concavity, such as concavity at both ends, or concavity in the middle, or a design method with multiple concavities and convexities in a serrated manner, the cogging torque is significantly reduced, the motor vibration is reduced, the electromagnetic noise is reduced, and at the same time, the sine characteristic of the motor magnetic flux density distribution is optimized, improving the efficiency of the motor, and the efficiency in the high-speed range of the motor is higher. Through the design of the symmetric geometric body structure, it is ensured that the front and back sides of the permanent magnet body are of the same shape. The permanent magnet body can realize the continuous mounting of the "N / S" law (the polarities of adjacent two magnetic poles are opposite) of the motor magnetic poles through the method of "unidirectional magnetization + front and back mounting", and the manufacturing process of the permanent magnet body itself is simple and the cost is low, while the motor magnetic pole installation process is foolproof and the production efficiency is high. In addition, the problems of non-symmetric permanent magnet installation orientation and fixed matching are solved, realizing free matching. Using finite element software to analyze the cogging torque, motor efficiency, motor magnetic flux density distribution cloud map, etc. of the in-wheel motor using the permanent magnet body, the analysis conclusion is that the structure of the permanent magnet body in the present utility model optimizes the back electromotive force waveform of the motor, reduces the amplitude of the cogging torque, reduces the harmonic noise, the efficiency in the high-speed section of the motor is increased by about 2% - 5%, the inter-pole leakage magnetic flux of the motor is effectively controlled, the leakage magnetic flux rate is reduced by 10% - 20%, and the magnetic energy utilization rate is effectively improved. The structure of the permanent magnet body of the present utility model uses less materials, reduces weight and cost, ensures the bonding strength of the permanent magnet, has a symmetric magnetic field distribution and is conducive to efficient installation, has low inter-pole leakage magnetic flux, small cogging torque, good sine property of the whole machine magnetic field distribution, simple permanent magnet body magnetization process, obvious improvement in motor magnetic energy utilization rate, optimization and improvement of motor efficiency, and simple and efficient motor assembly process.

[0050] The above-described embodiments are only the preferred embodiments of the present utility model, and are only used to illustrate the technical solutions of the present utility model, and are not intended to limit the patent scope of the present utility model. Although the specific implementation manners of the present utility model have been described above, those of ordinary skill in the art can make changes without departing from the spirit and principle of the present utility model. The protection scope of the present utility model is defined by its claims and their equivalents. Any modification or equivalent replacement of the technical solutions of the present utility model by using the content of the specification and drawings of the present utility model, or direct or indirect application in other related technical fields, shall be included in the patent protection scope of the present utility model by the same token.

[0051] Although terms such as permanent magnet body 1, magnetic conduction ring 2, projection plane 3 of the permanent magnet body in its magnetization direction, minimum circumscribed parallelogram 4 of the projection plane of the permanent magnet body in its magnetization direction, symmetry axis 5 of the head and tail splicing edge of the permanent magnet body, axial dimension center line 6 of the permanent magnet body, head and tail splicing edge 11, concave structure 111, total axial width B of the permanent magnet body, concave dimension H of the concave structure, area S of the projection plane of the permanent magnet body in its magnetization direction, area T of the minimum circumscribed parallelogram of the projection plane of the permanent magnet body in its magnetization direction, width W in the splicing direction of the permanent magnet body, motor axial direction X, head and tail splicing direction Y of the permanent magnet installation, axial width b1 of the first concave structure of the permanent magnet body, and axial width b2 of the second concave structure of the permanent magnet body are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present utility model; interpreting them as any additional limitation is contrary to the spirit of the present utility model.

Claims

1. A permanent magnet for an outer rotor motor, the motor comprising a magnetic conductive ring (2) and a plurality of permanent magnet bodies (1), characterized in that: The permanent magnet body (1) is an axially symmetrically distributed geometric body. The permanent magnet body (1) is installed on the inner ring of the magnetic conductive ring in an end-to-end splicing manner. A plurality of concave structures (111) are provided on the end-to-end splicing edges (11) of two adjacent permanent magnet bodies (1). The permanent magnet bodies (1) are in contact at the convex parts of the end-to-end splicing edges (11). The ratio of the area S of the projection surface of the permanent magnet body (1) in the magnetization direction to the area T of the smallest outer parallelogram of the projection surface of the permanent magnet body (1) in the magnetization direction is in the range of 0.75 to 0.95, that is, the range of S / T is 0.75 to 0.

95.

2. The permanent magnet of an outer rotor motor according to claim 1, characterized in that: The head and tail joint edges (11) of any of the permanent magnet bodies (1) are axially symmetrically distributed with respect to each other.

3. The permanent magnet of an outer rotor motor according to claim 2, characterized in that: The total width of all the concave structures (111) on any of the head and tail joint edges (11) in the axial direction of the motor accounts for 1 / 2 of the total axial width of the permanent magnet body (1).

4. The permanent magnet of an outer rotor motor according to claim 1, characterized in that: The permanent magnet body (1) is symmetrically distributed about its center line (6) in the axial dimension of the motor.

5. The permanent magnet of an outer rotor motor according to claim 1, characterized in that: The concave dimension H of the concave structure (111) is ≥ 0.5 mm.

6. The permanent magnet of an outer rotor motor according to claim 1, characterized in that: The concave dimensions H of the plurality of concave structures (111) are equal.

7. The permanent magnet of an outer rotor motor according to claim 1, characterized in that: The permanent magnet body (1) is a geometric body which is concave in the middle and convex at both axial ends, or convex in the middle and concave at both axial ends.

8. A permanent magnet for an outer rotor motor according to any one of claims 1 to 7, characterized in that: The permanent magnet body (1) has the radial direction of the motor as the magnetization direction.

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