Motor structure capable of reducing demagnetization risk

Abstract

The utility model provides a motor structure capable of reducing demagnetization risk, which comprises a stator and a rotor arranged around the stator, the stator is provided with a yoke part, a plurality of tooth parts arranged on the yoke part, a plurality of shoe parts arranged at one ends of the tooth parts and a plurality of coils wound on the tooth parts, two symmetrical shoe parts are arranged at one end of each tooth part, and a groove opening is formed between the two shoe parts of the adjacent tooth parts; the rotor is provided with a plurality of radial magnets and a plurality of circumferential magnets, the radial magnets and the circumferential magnets are arranged in a Halbach array, the radial magnets and the circumferential magnets are arranged in a staggered mode, the magnetic field intensity of the radial magnets is higher than that of the circumferential magnets, and the demagnetization risk of the circumferential magnets of the rotor is reduced through matching of different magnetic field intensities.

Description

Technical Field

[0001] The utility model relates to a motor structure, and more particularly to a motor structure capable of reducing the risk of demagnetization. The structure arranges rotor magnets in a Halbach array to enhance the torque of the motor, and the magnetic field strength of the radial magnets selected is higher than the magnetic field strength of the circumferential magnets. By matching rotor magnets with different magnetic field strengths, the risk of demagnetization of the circumferential magnets of the rotor is reduced, thereby avoiding the decay of the motor torque. Background Art

[0002] With the advancement of technology, many things in life have been electronicized, and the demand for motors is increasing. The principle of motors is to convert electrical energy into kinetic energy to drive other devices. The motor structure is mainly composed of a stator and a rotor. A coil is wound on the stator. When powered on, electromagnetic induction occurs between the coil and the rotor, allowing the rotor to generate an induced electromotive force and form an induced current. At this time, the rotor starts to rotate and can output power to the device connected to the back end.

[0003] If the motor is used in a harsh environment, especially in a high temperature or severe vibration environment, the motor's rotor magnet may be demagnetized. The demagnetization of the magnet is an irreversible state. Once demagnetization occurs, it will directly affect the rotor's torque output and the motor's output power will permanently decline. Therefore, motor manufacturers hope to improve the magnet's demagnetization resistance by changing the magnet structure, or by adding heat dissipation components to reduce the motor's operating temperature, so as to reduce the probability of demagnetization and allow the motor to maintain its original performance.

[0004] Patent Announcement No. I502858 "Permanent Magnet Rotating Electric Machine" discloses a method of improving the demagnetization resistance of magnets by changing the magnet structure, so that the two ends of each magnet of the rotor have different thicknesses. When arranged, the thin end is connected to the thick end of another magnet. In this way, in the block where the thickness of the magnet is increased, the gap between the stator and the rotor will also become narrower, so the magnetic permeability coefficient of the magnet will increase and the demagnetization resistance will be improved. Patent Announcement No. I686036 "Permanent Magnet Motor" discloses a method of adding a heat dissipation structure to improve the efficiency of motor cooling. It has a magnetic barrier hole that runs through the rotor, so that a hollow channel is formed inside the rotor to be used as a heat dissipation channel or an airflow guide channel. After the permanent magnet motor is installed in the compressor, it helps to improve the heat dissipation of the motor and reduce the fluid resistance, reduce the demagnetization phenomenon caused by excessive temperature, and thus maintain the motor performance and increase the motor life.

[0005] However, whether changing the structure of the magnet or adding a heat dissipation structure, additional structural costs will be generated and will affect the overall design of the motor. Therefore, how to provide a motor structure that can reduce the risk of demagnetization and reduce the additional structural design cost of the motor is the direction of consideration of the applicant. Utility Model Content

[0006] In view of the fact that the above-mentioned existing motor structure still has many deficiencies in actual implementation and use, the applicant has made improvements with the help of his rich professional knowledge and many years of practical experience, and has developed the present utility model accordingly.

[0007] The main purpose of the utility model is to provide a motor structure that can reduce the risk of demagnetization. By combining different magnet brands of rotor magnets, the magnets can have different magnetic field strengths to reduce the risk of demagnetization of the rotor magnets, so that the output torque of the motor will not be reduced due to demagnetization, and the service life of the motor can be increased.

[0008] In order to achieve the above-mentioned implementation objectives, the utility model provides a motor structure capable of reducing the risk of demagnetization, which includes a stator, including a yoke, a plurality of teeth arranged on the yoke, a plurality of boots arranged at one end of the plurality of teeth, and a plurality of coils wound around the plurality of teeth, one end of each tooth is provided with two symmetrical boots, and a slot opening is formed between the two boots of two adjacent teeth; and a rotor, which is arranged around the stator and includes a plurality of radial magnets and a plurality of circumferential magnets arranged in a Halbach array, the plurality of radial magnets are arranged alternately with the plurality of circumferential magnets, and the magnetic field strength of the plurality of radial magnets is higher than the magnetic field strength of the plurality of circumferential magnets, so as to reduce the risk of demagnetization of the plurality of circumferential magnets.

[0009] In an embodiment provided by the present invention, the plurality of radial magnets are magnets with a magnet grade between N45 and N55.

[0010] In an embodiment provided by the present invention, the plurality of circumferential magnets are magnets with a magnet grade between N35 and N42.

[0011] In an embodiment provided by the present invention, directions of magnetic force lines of the plurality of radial magnets and directions of magnetic force lines of the plurality of circumferential magnets are perpendicular to each other.

[0012] In an embodiment provided by the present invention, a motor consisting of a stator and a rotor is further disposed in a wheel set of an electric scooter to be used as a hub motor.

[0013] In one embodiment provided by the present invention, the wheel set of the electric scooter includes a wheel rim for accommodating a hub motor, a fixed shaft connected to a stator, two bearings respectively sleeved on both ends of the fixed shaft, and a brake assembly arranged on the wheel rim.

[0014] In an embodiment provided by the present invention, the ratio of the size of each radial magnet to the sum of the sizes of each radial magnet and each circumferential magnet is 0.6-0.8.

[0015] In an embodiment provided by the present invention, the ratio of the size of the slot opening of the stator to the size of each circumferential magnet is 0.6-1.

[0016] In an embodiment provided by the present invention, the size refers to the length of each radial magnet and each circumferential magnet, and the width of the slot opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other purposes, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0018] Figure 1 A partial cross-sectional view of a motor structure according to a preferred embodiment of the utility model;

[0019] Figure 2 This is a schematic diagram of the arrangement of rotor magnets in a preferred embodiment of the utility model;

[0020] Figure 3 It is a schematic diagram of an exploded view of components of a motor applied to an electric scooter according to a preferred embodiment of the utility model;

[0021] Figure 4 A magnetic flux density diagram for thermal demagnetization comparison of a preferred embodiment of the utility model;

[0022] Figure 5 A diagram showing the relationship between slot opening and torque of a preferred embodiment of the utility model;

[0023] Figure 6 A diagram showing the relationship between slot opening and torque ripple in a preferred embodiment of the utility model;

[0024] Figure 7 The average torque diagram of the slot opening and magnet ratio of the preferred embodiment of the utility model;

[0025] Figure 8 The torque ripple diagram of the slot opening and magnet ratio of the preferred embodiment of the utility model;

[0026] Fig. 9 A motor efficiency diagram of the slot opening and magnet ratio of a preferred embodiment of the utility model;

[0027] Fig.10 A schematic diagram of the arrangement of rotor magnets in the prior art; and

[0028] Fig.11The figure is a schematic diagram comparing the volumes of a hub motor applied to an electric scooter according to a preferred embodiment of the present utility model and the prior art.

[0029] In the above drawings, the meanings of the reference numerals are as follows:

[0030] 1. Motor;

[0031] 11. Stator;

[0032] 111. Yoke;

[0033] 112. Tooth;

[0034] 113. Boots;

[0035] 114. Coil;

[0036] 115. Slot opening;

[0037] 12. Rotor;

[0038] 121, radial magnet;

[0039] 122. Circumferential magnet;

[0040] 123. Rotor seat;

[0041] 2. Wheel set;

[0042] 21. Wheel rim;

[0043] 211, side panels;

[0044] 22. Fixed axis;

[0045] 23. Bearings;

[0046] 24. Brake assembly. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0048] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "include", "comprises", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0049] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0050] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0051] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only for reference to the drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted when they may cause confusion in the understanding of the present invention.

[0052] See also Figure 1~Figure 3 The motor structure that can reduce the risk of demagnetization provided by the embodiment of the utility model includes a stator 11 and a rotor 12, which can be arranged in a wheel set 2 of an electric scooter to be used as a hub motor. The wheel set 2 includes a wheel rim 21 for accommodating the motor 1, a fixed shaft 22 connected to the stator 11, two bearings 23 respectively sleeved on both ends of the fixed shaft 22, and a brake assembly 24 arranged on the wheel rim 21.

[0053] The stator 11 of the motor 1 provided in the embodiment of the utility model includes a yoke 111, a plurality of teeth 112 arranged on the yoke 111, a plurality of boots 113 arranged at one end of the plurality of teeth 112, and a plurality of coils 114 wound around the plurality of teeth 112, two symmetrical boots 113 are arranged at one end of each tooth 112, and a slot opening 115 is formed between the two boots 113 of two adjacent teeth 112.

[0054] The rotor 12 is arranged around the stator 11, and includes a plurality of radial magnets 121 and a plurality of circumferential magnets 122 arranged in a Halbach array. The plurality of radial magnets 121 are arranged alternately with the plurality of circumferential magnets 122. The radial magnets 121 can be magnets with magnet grades between N45 and N55, and the circumferential magnets 122 can be magnets with magnet grades between N35 and N45. The magnetic field strength of the radial magnets 121 is higher than that of the circumferential magnets 122, thereby reducing the risk of demagnetization of the circumferential magnets 122 and making the directions of the magnetic lines of force of the plurality of radial magnets 121 and the directions of the magnetic lines of force of the plurality of circumferential magnets 122 perpendicular to each other. Among them, the ratio of the size of the radial magnet 121 to the sum of the sizes of the radial magnet 121 and the circumferential magnet 122 is 0.6~0.8, and the ratio of the size of the slot opening 115 of the stator 11 to the size of the circumferential magnet 122 is 0.6~1, and the size here refers to the length of the radial magnet 121 and the circumferential magnet 122, and the width of the slot opening 115.

[0055] In addition, the following specific embodiments can further demonstrate the practical application scope of the present invention, but do not limit the scope of the present invention in any form.

[0056] Please continue reading Figure 1 and Figure 2 In the embodiment of the utility model, the stator 11 of the motor 1 is formed by stacking a plurality of silicon steel sheets to form a hollow annular yoke 111. The yoke 111 extends outward to form a plurality of teeth 112. Two symmetrical boots 113 are formed at one end of each tooth 112. The position of a slot opening 115 can be defined between the boots 113 of adjacent teeth 112. The winding machine can wind the coil 114 on each tooth 112 through the slot opening 115.

[0057] The multiple radial magnets 121 and the multiple circumferential magnets 122 of the rotor 12 are arranged in a Halbach array, wherein the directions of the magnetic lines of force of the radial magnets 121 and the circumferential magnets 122 are perpendicular to each other, and the directions of the magnetic lines of force are repeatedly arranged in the order of top, right, bottom, and left. This arrangement can enhance the magnetic field on one side. In this embodiment, the motor 1 structure is an external rotation type, and the rotor 12 is arranged around the stator 11. The side of the rotor 12 with a stronger magnetic field is adjacent to the stator 11, so that a large amount of magnetic lines of force can flow into the stator 11 more easily, and the torque can be improved.

[0058] During the use of the motor 1, the working temperature will inevitably rise gradually. In a high temperature environment, the radial magnets 121 and the circumferential magnets 122 of the rotor 12 may undergo thermal demagnetization, causing the magnetic force of the radial magnets 121 and the circumferential magnets 122 to decrease. The thermal demagnetization of magnets is an irreversible state. Once thermal demagnetization occurs, the output power of the motor 1 will permanently decline, and the torque and efficiency will not be able to return to the data specifications before thermal demagnetization. If the thermal demagnetization phenomenon occurs repeatedly, the magnetic force of the radial magnets 121 and the circumferential magnets 122 will gradually disappear, resulting in a decrease in the torque of the motor 1. In this embodiment, the magnetic force of the radial magnets 121 and the circumferential magnets 122 will gradually disappear, causing a decrease in the torque of the motor 1. In the embodiment, since the rotor 12 is arranged in a Halbach array, the radial magnets 121 and the circumferential magnets 122 are arranged alternately, and the directions of the magnetic lines of force are perpendicular to each other, which makes it easier for the circumferential magnets 122 to be thermally demagnetized. Therefore, when the radial magnets 121 and the circumferential magnets 122 are selected, the radial magnets 121 are selected with magnets of larger magnet grades, such as N45, N48, N50, N52, N54 or N55, and the circumferential magnets 122 are selected with magnets of smaller magnet grades, such as N35, N38, N40 or N42, which can effectively reduce the risk of thermal demagnetization of the circumferential magnets 122. In the present embodiment, the radial magnets 121 and the circumferential magnets 122 are made of neodymium iron boron to obtain a larger magnetic force.

[0059] Generally speaking, the larger the magnet brand number, the greater the residual induction and maximum energy product, which means the stronger the magnetic field strength. The smaller the magnet brand number, the weaker the magnetic field strength, but the greater the coercive force, which means it is better at resisting demagnetization.

[0060] Furthermore, three groups of different magnet brands were compared and tested at a temperature of 120°C; the radial magnet 121 of group (a) selected magnets of magnet brand N50, and the circumferential magnet 122 selected magnets of magnet brand N35; the radial magnet 121 of group (b) selected magnets of magnet brand N50, and the circumferential magnet 122 selected magnets of magnet brand N40; and the radial magnet 121 and the circumferential magnet 122 of group (c) both selected magnets of magnet brand N50. Figure 4The magnetic flux density distribution of the three groups of magnet brand combinations can be seen in the figure. The circled position in the figure shows the thermal demagnetization area on the circumferential magnet 122. The thermal demagnetization area of ​​the magnet combination of group (c) using the same magnet brand is significantly larger than that of group (a) and group (b). If converted into actual values, the demagnetization area of ​​group (a) is 0.987 mm2, the demagnetization area of ​​group (b) is 1.187 mm2, and the demagnetization area of ​​group (c) is 2.015 mm2. Through this test result, it can be seen that when the magnetic field strength of the radial magnet 121 is higher than the magnetic field strength of the circumferential magnet 122, the range of thermal demagnetization of the circumferential magnet 122 in a high temperature environment can be effectively reduced, the influence on the decay of the output torque of the motor 1 can be reduced, the risk of thermal demagnetization can be controlled, and the service life of the motor 1 can be extended.

[0061] In the prior art, in order to reduce the occurrence of magnetic leakage, the current surface mounted magnetization (SPM) usually uses the narrower slot opening width as possible, so that the magnetic lines of force can flow into the stator completely, so that the magnetic flux density of the stator reaches a saturated state, and better torque characteristics are obtained through a narrower slot opening. However, for the rotor 12 using the Halbach array in the present invention, the applicant confirmed during research that this arrangement of magnets is opposite to the surface mounted magnetization technology, and the slot opening 115 of the stator 11 is not the narrower the better, and the slot opening 115 of the stator 11 will show a curve relationship with the output torque. Figure 5 As shown, in this embodiment, when the width of the slot opening 115 is 2 mm and 8 mm, only a small torque can be obtained, while when the width of the slot opening 115 is about 5 mm, the maximum torque can be output. Figure 6 In the relationship between the slot opening 115 and the torque ripple, when the slot opening 115 width is 2 mm, the torque ripple presents the highest value, and when the slot opening 115 gradually increases to 8 mm, the torque ripple also decreases accordingly. It can be seen that when the slot opening 115 width is the smallest 2 mm, the torque and torque ripple output by the motor 1 both present poor data. In the figure, the torque ripple trend is relatively linear, and as the slot opening 115 width increases, the motor performance becomes more stable.

[0062] Based on the above research results, in order to standardize and obtain the best output data, the applicant defines that the radial magnet 121 of the rotor 12 and the circumferential magnet 122 have a specific proportional relationship in size, and the slot opening 115 of the stator 11 and the circumferential magnet 122 of the rotor 12 also have a specific proportional relationship in size, so that the output performance of the motor 1 can stably fall within an optimal range and reduce the leakage magnetic phenomenon. In this embodiment, the radial magnet 121 is a magnet of a larger size than the circumferential magnet 122, that is, the length of the radial magnet 121 is greater than the length of the circumferential magnet 122. The relationship between the radial magnet 121 and the circumferential magnet 122 affected by the circumferential magnet 122 can be defined by the ratio of the length of the radial magnet 121 to the sum of the lengths of the radial magnet 121 and the circumferential magnet 122. Please refer to formula (1) for this ratio. In this embodiment, the ratio of the magnetic circles is 0.6~0.8, which is a better ratio.

[0063] Magnetic circle (embrace) = radial magnet / (radial magnet + circumferential magnet) Formula (1).

[0064] Please see again Figure 7~Figure 9 In the figure, eb0.6, eb0.7, and eb0.8 represent that the magnetic coils of this embodiment are 0.6, 0.7, and 0.8 respectively, and B type represents the existing motor structure. From the relationship between the magnet ratio and the slot opening 115, it can be seen that when the slot opening 115 is 3 mm to 5 mm, the average torque and efficiency of the motor 1 can be maintained in the optimal range, and the torque ripple presents relatively good data. The existing surface-mounted motor structure B type has a performance worse than that of the present embodiment, and since the magnetic flux leakage phenomenon is mostly caused by the circumferential magnet 122, based on the above-mentioned magnetic circle relationship, the width of the slot opening 115 can be determined according to the size (length) of the circumferential magnet 122 when adding the test. In the present embodiment, the width of the slot opening 115 is set to 60%~100% of the length of the circumferential magnet 122, which means that the ratio of the width of the slot opening 115 to the length of the circumferential magnet 122 is 0.6~1; thus, the rotor 12 manufactured with a specific ratio of the radial magnet 121 to the circumferential magnet 122 and a specific ratio of the slot opening 115 to the circumferential magnet 122 can effectively reduce magnetic flux leakage and achieve the best torque and efficiency performance.

[0065] Furthermore, the stator 11 and the rotor 12 of the motor 1 of the utility model can be installed in the wheel rim 21 of the wheel set 2 of the electric scooter, and the rotor 12 will be set on the inner ring of the wheel rim 21 through the rotor seat 123 to be used as a hub motor, and the fixed shaft 22 will be penetrated through the hollow area in the center of the stator 11, and two bearings 23 are respectively penetrated at both ends of the fixed shaft 22, and the bearings 23 will be fixed in the side plates 211 on both sides of the wheel rim 21. Finally, the frame of the electric scooter is assembled with the fixed shaft 22 to complete the combination of the electric scooter and the motor 1, so that the motor 1 can directly drive the wheel set 2 to rotate, and then the brake assembly 24 assembled on one of the side plates 211 of the wheel rim 21 provides a braking function, so that the electric scooter can be decelerated in time.

[0066] Continue reading Fig.10 and Fig.11 , a motor assembled by a rotor with a surface magnet in the prior art is compared with the motor 1 of the present embodiment using a rotor 12 with a Halbach array, Fig.10 Schematic diagram of the magnet arrangement of the prior art. The existing rotor magnets are arranged with N poles and S poles alternately. Through this magnet arrangement, a uniform magnetic field distribution is generated on both sides. This is also the most common arrangement at present. When the existing stator cannot completely allow the magnetic lines of force to flow in, the overall size is usually increased to increase the thickness of the existing motor to accommodate more magnetic lines of force, so that the torque of the existing motor is improved. The present embodiment uses the magnet arrangement of the Halbach array, which is characterized by enhancing the magnetic field on one side, without increasing the thickness of the motor 1, and can achieve the same torque as the existing motor with a smaller volume. Fig.11 It can be seen that the existing motor thickness is as high as 38 mm, while this embodiment is only 30.1 mm, which is about 20% different in volume. However, it can also output 8.35 Nm of torque during testing. In this way, when the motor 1 of the utility model is applied to other equipment, it can achieve a lightweight effect. The amount of iron and copper materials used in the motor 1 as a whole is less, which has a great advantage in material cost and weight. If it is used as a hub motor in an electric scooter, the smaller motor 1 can provide a more flexible choice for the wheel set 2.

[0067] It can be seen from the above implementation description that compared with the prior art, the present invention has the following advantages:

[0068] 1. The motor structure of the utility model can reduce the risk of demagnetization. The magnetic field strengths of the radial magnets and the circumferential magnets of the rotor will be matched differently, and the magnetic field strength of the radial magnets will be higher than the magnetic field strength of the circumferential magnets. Through this combination, even in a high temperature environment, the risk of thermal demagnetization of the circumferential magnets can be reduced, the torque decay of the motor can be avoided, and the service life of the motor can be increased.

[0069] 2. The motor structure of the utility model can reduce the risk of demagnetization. The rotor magnets are arranged using a Halbach array so that the magnetic lines of force of the radial magnets and the circumferential magnets are in different directions. The magnetic field is concentrated on one side to increase the overall output power of the motor.

[0070] 3. The motor structure of the utility model can reduce the risk of demagnetization. Through the arrangement of the Halbach array, the size of the motor can be reduced while maintaining high torque. It can also save overall material costs and reduce weight. When used as a hub motor, the wheel set of the electric scooter has more flexible choices and applications, and can also reduce the cost of the wheel set, so that the electric scooter can achieve a lightweight effect. The length of the radial magnet and the circumferential magnet of the rotor has a specific proportional relationship, and the slot opening of the stator and the circumferential magnet of the rotor also have a specific proportional relationship. This size relationship can reduce magnetic leakage and keep the magnetic flux density of the stator in a saturated state, so that the motor has high torque and high efficiency performance, thereby improving the motor output power.

[0071] In summary, the motor structure capable of reducing the risk of demagnetization of the present invention can indeed achieve the expected use effect through the above-disclosed embodiments; however, the above-disclosed drawings and descriptions are only preferred embodiments of the present invention, and the methods and constituent elements disclosed in the above-disclosed embodiments are only for illustrative purposes and are not intended to limit the scope of the present invention. Replacements or changes of other equivalent elements should also be covered by the scope of the patent application of the present invention.

[0072] The embodiments of the present invention are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present invention is defined by the attached claims and their equivalents. Without departing from the scope of the present invention, a person skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A motor structure capable of reducing the risk of demagnetization, characterized in that: Contains: A stator comprises a yoke, a plurality of teeth arranged on the yoke, a plurality of boots arranged at one end of the plurality of teeth, and a plurality of coils wound around the plurality of teeth, wherein one end of each of the teeth is provided with two symmetrical boots, and a slot opening is formed between the two boots of the two adjacent teeth; as well as A rotor is arranged around the stator, comprising a plurality of radial magnets and a plurality of circumferential magnets arranged in a Halbach array, wherein the plurality of radial magnets are arranged alternately with the plurality of circumferential magnets, and the magnetic field strength of the plurality of radial magnets is higher than the magnetic field strength of the plurality of circumferential magnets to reduce the risk of demagnetization of the plurality of circumferential magnets.

2. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The plurality of radial magnets are magnets with a magnet grade between N45 and N55.

3. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The plurality of circumferential magnets are magnets with grades ranging from N35 to N42.

4. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The directions of the magnetic force lines of the plurality of radial magnets are perpendicular to the directions of the magnetic force lines of the plurality of circumferential magnets.

5. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The motor composed of the stator and the rotor is further arranged in a wheel set of an electric scooter to be used as a hub motor.

6. The motor structure capable of reducing the risk of demagnetization according to claim 5, characterized in that: The wheel set of the electric scooter comprises a wheel rim for accommodating the wheel hub motor, a fixed shaft connected to the stator, two bearings respectively sleeved on both ends of the fixed shaft and a brake assembly arranged on the wheel rim.

7. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The ratio of the size of each radial magnet to the sum of the sizes of each radial magnet and each circumferential magnet is 0.6-0.

8.

8. The motor structure capable of reducing the risk of demagnetization according to claim 1, characterized in that: The ratio of the size of the slot opening of the stator to the size of each of the circumferential magnets is 0.6-1.

9. The motor structure capable of reducing the risk of demagnetization according to claim 7 or 8, characterized in that: The dimension refers to the length of each of the radial magnets and each of the circumferential magnets, and the width of the slot opening.

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