Outer rotor of an electric machine and outer rotor electric machine having the same

Abstract

The utility model discloses an outer rotor of motor and have its outer rotor motor relates to motor field. Outer rotor includes: a plurality of permanent magnet, a plurality of plastic magnet main part, a plurality of plastic magnet main part one -to -one correspondence fills between two adjacent permanent magnet, and plastic magnet main part is fixedly connected permanent magnet through integrated injection molding. Every permanent magnet is radial magnetization and every plastic magnet main part is tangential magnetization, or every permanent magnet is tangential magnetization and every plastic magnet main part is radial magnetization, and the magnetization direction of two adjacent permanent magnet is opposite, and the magnetization direction of every plastic magnet main part is consistent with the magnetic field direction formed by two adjacent permanent magnet. And the central axis of every permanent magnet is relatively the central axis of outer rotor and sets up along the tangentiality. According to the utility model embodiment's outer rotor of motor, harmonic content reduces greatly, not only has improved the power density of motor, but also has reduced the harmonic content in air gap magnetic field, has reduced the risk of motor electromagnetic vibration noise production.

Description

Technical Field

[0001] This utility model relates to the field of motors, specifically to an external rotor of a motor and a motor having the external rotor thereon. Background Technology

[0002] Brushless motors can be classified into internal rotor motors and external rotor motors according to their structure. External rotor brushless motors are widely used in applications where the motor's size is limited but sufficient output torque is required.

[0003] External rotor motors are often designed for high power density, but once the power density of the motor increases, the noise also increases, requiring improvement. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an external rotor for an electric motor that improves the power density of the motor while controlling noise.

[0005] This utility model also aims to propose an external rotor motor including the above-mentioned external rotor.

[0006] The outer rotor of the motor according to an embodiment of the present invention includes: a plurality of permanent magnets, the plurality of permanent magnets being arranged at intervals along the circumference, each of the permanent magnets being a sheet extending along the circumference; a plurality of plastic magnetic bodies, the plurality of plastic magnetic bodies being filled between two adjacent permanent magnets in a one-to-one correspondence, the plastic magnetic bodies being fixedly connected to the permanent magnets by integral injection molding; wherein, each of the permanent magnets is radially magnetized and each of the plastic magnetic bodies is tangentially magnetized, or each of the permanent magnets is tangentially magnetized and each of the plastic magnetic bodies is radially magnetized, the magnetization directions of two adjacent permanent magnets are opposite, and the magnetization direction of each plastic magnetic body is consistent with the direction of the magnetic field formed by two adjacent permanent magnets; and the central axis of each permanent magnet is tangentially inclined relative to the central axis of the outer rotor.

[0007] According to an embodiment of this utility model, the outer rotor of the motor is formed by filling with a plastic magnetic material to create a plastic magnetic body. Multiple permanent magnets are then connected to complete the rotor ring. These permanent magnets, in conjunction with the plastic magnetic body, form multiple magnetic poles. After the plastic magnetic material is formed, it is magnetized using tooling, achieving an alternating arrangement of radial and tangential magnetization in the space of the outer rotor. By controlling the forming path of the plastic magnetic material during the process of coating the permanent magnets, the size and physical shape of the magnetic poles of the plastic magnetic body can be controlled.

[0008] In this application, the easy configuration characteristics and coating properties of the plastic magnetic body through injection molding are utilized to connect the permanent magnet poles and the plastic magnetic poles into a complete magnetic ring, which can effectively control the manufacturing cost of the outer rotor. The outer rotor does not require too many processing steps, which is beneficial to the overall motor cost in terms of materials and manufacturing.

[0009] In this application, the permanent magnet is tilted because traditional permanent magnet motors, which are parallel to the central axis of the outer rotor, inevitably experience some manufacturing deviations, leading to vibration and noise risks. Conventional optimization methods are unlikely to solve these problems. However, this application significantly reduces the harmonic content by tilting the permanent magnet. Reducing the harmonic content in the air gap magnetic field can effectively improve the vibration and noise caused by manufacturing deviations and reduce the sensitivity of vibration and noise to the manufacturing process.

[0010] Of course, in conventional solutions, tilting the magnetic tiles makes manufacturing extremely difficult and requires very high technical skill. This application addresses the Halbach pole tilting problem by connecting adjacent permanent magnets with a plastic magnetic material, thus improving manufacturability.

[0011] In some embodiments, the angle between the central axis of the permanent magnet and the central axis of the outer rotor is α1, satisfying: 360° / LCM(Z, Np)≤α1≤0.8*360° / Z; Wherein, LCM is the least common multiple, Z is the number of stator slots of the motor, and Np is the number of poles of the outer rotor.

[0012] In some embodiments, the outer rotor further includes: a first outer diameter plastic magnetic part connected to the radial outer side of the permanent magnet; a second outer diameter plastic magnetic part connected to the radial outer side of the plastic magnetic body; the second outer diameter plastic magnetic part, the first outer diameter plastic magnetic part, and the plastic magnetic body are integrally formed by injection molding.

[0013] Specifically, the magnetization direction of the first outer diameter plastic magnetic part is consistent with the magnetization direction of the permanent magnet on its inner radial side, and the magnetization direction of the second outer diameter plastic magnetic part is consistent with the magnetization direction of the plastic magnetic body on its inner radial side.

[0014] Optionally, the radial dimension of the first outer diameter plastic magnet is d1, which satisfies d1≥1.5mm.

[0015] In some embodiments, the outer rotor further includes: at least one shaft-end plastic magnetic ring, the shaft-end plastic magnetic ring being located at one axial end of the permanent magnet and the plastic magnetic body, and being connected to all the permanent magnets and all the plastic magnetic bodies; The shaft-end plastic magnetic ring and the plastic magnetic body are formed by integral injection molding.

[0016] In some embodiments, the radially magnetized permanent magnet or the plastic magnetic body occupies a central angle b1 in the outer rotor; the tangentially magnetized permanent magnet or the plastic magnetic body occupies a central angle b2 in the outer rotor; satisfying: b1>b2.

[0017] In some embodiments, the outer rotor further includes: a rotor yoke ring, the rotor yoke ring being sleeved on the radially outer side of the permanent magnet and the plastic magnet body; The plastic magnet body is fixedly connected to the permanent magnet and the rotor yoke ring by integral injection molding.

[0018] In some embodiments, the permanent magnet is a rectangular sheet or an arc-shaped sheet, and the permanent magnet is sintered ferrite.

[0019] An external rotor motor according to an embodiment of the present invention includes: a stator; and an external rotor of the motor according to the above embodiment, wherein the external rotor is sleeved on the radially outer side of the stator.

[0020] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a top view of the outer rotor of some embodiments of the present invention; Figure 2 This is a schematic diagram of the partial position structure of the outer rotor in some embodiments of this utility model; Figure 3 This is a perspective view of the outer rotor of some other embodiments of the present invention; Figure 4 for Figure 3 The graph shows the variation trend of the 2p-order noise and back EMF of the external rotor with the skew angle α1 in some specific embodiments. Figure 5 This is a partial structural diagram of the outer rotor of some embodiments of the present invention; Figure 6 This is a top view of the outer rotor of some embodiments of the present invention; Figure 7 This is a perspective view of the outer rotor of some other embodiments of the present invention; Figure 8 This is an assembly diagram of an external rotor motor according to some embodiments of the present invention; Figure 9 This is an assembly diagram of an external rotor motor according to some embodiments of the present invention.

[0022] Figure label: External rotor motor 10 Outer rotor 1, central axis L1 of the outer rotor 11. Permanent magnet; 12. Plastic magnet body; 13. Plastic magnet part outside the first diameter; 14. Plastic magnet part inside the first diameter; 15. Plastic magnet part outside the second diameter; 16. Plastic magnet part inside the second diameter; 17. Rotor yoke ring; 18. Rotor end plate; 19. Shaft end plastic magnet ring. Stator 2, stator core 21, stator slot 211, stator teeth 212, coil winding 23 Shaft 3. Detailed Implementation

[0023] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0024] In the description of this utility model, it should be understood that the terms "center," "length," "width," "thickness," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more. In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0025] The external rotor 1 of the motor according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0026] According to an embodiment of the present invention, the outer rotor 1 of the motor is shown in reference to... Figure 1 and Figure 2 It includes: multiple permanent magnets 11 and multiple plastic magnet bodies 12.

[0027] Multiple permanent magnets 11 are arranged at circumferential intervals, each permanent magnet 11 being a sheet extending circumferentially. Multiple plastic magnetic bodies 12 are correspondingly filled between adjacent permanent magnets 11, and the plastic magnetic bodies 12 are integrally injection molded to the permanent magnets 11. That is, a slot is created between every two adjacent permanent magnets 11, and each slot is filled with plastic magnetic material to form a plastic magnetic body 12. The multiple plastic magnetic bodies 12 correspond one-to-one with the multiple slots, therefore the multiple plastic magnetic bodies 12 are arranged circumferentially, each plastic magnetic body 12 being a sheet extending circumferentially. In this way, the multiple permanent magnets 11 and the multiple plastic magnetic bodies 12 are sequentially connected to form a magnetic ring.

[0028] Each permanent magnet 11 is radially magnetized and each plastic magnetic body 12 is tangentially magnetized, or each permanent magnet 11 is tangentially magnetized and each plastic magnetic body 12 is radially magnetized. The magnetization directions of two adjacent permanent magnets 11 are opposite, and the magnetization direction of each plastic magnetic body 12 is consistent with the direction of the magnetic field formed by the two adjacent permanent magnets 11. Not only are the magnetization directions of two adjacent permanent magnets 11 opposite, but the magnetization directions of two adjacent plastic magnetic bodies 12 are also opposite.

[0029] In radial magnetization, opposite magnetization directions for adjacent objects mean that one object is magnetized radially inwards, and the other object is magnetized radially outwards. In tangential magnetization, opposite magnetization directions for adjacent objects mean that either the magnetization directions of the two adjacent objects are towards each other, or the magnetization directions of the two adjacent objects are away from each other.

[0030] Specifically, when each permanent magnet 11 is radially magnetized, the magnetization directions of two adjacent permanent magnets 11 are opposite. Each plastic magnetic body 12 is tangentially magnetized, and the magnetization direction is consistent with the direction of the magnetic field formed by two adjacent permanent magnets 11. A magnetic circuit formed by closed-loop magnetic lines of force can be formed between each pair of adjacent permanent magnets 11, and the magnetization direction of the plastic magnetic body 12 between each pair of adjacent permanent magnets 11 is consistent with the direction of the magnetic lines of force at the position of the plastic magnetic body 12. In other words, when the magnetization directions of two adjacent plastic magnetic bodies 12 (i.e., the direction of the formed magnetic lines of force) are towards each other, the magnetization direction of the permanent magnets 11 between them (i.e., the direction of the formed magnetic lines of force) is radially from the outside to the inside. When the magnetization directions of two adjacent plastic magnetic bodies 12 (i.e., the direction of the formed magnetic lines of force) are away from each other, the magnetization direction of the permanent magnets 11 between them (i.e., the direction of the formed magnetic lines of force) is radially from the inside to the outside.

[0031] Alternatively, when each permanent magnet 11 is tangentially magnetized, the magnetization directions of two adjacent permanent magnets 11 are opposite. Each plastic magnetic body 12 is radially magnetized, and the magnetization direction is consistent with the direction of the magnetic field formed by two adjacent permanent magnets 11. A magnetic circuit formed by closed-loop magnetic lines of force can be formed between each pair of adjacent plastic magnetic bodies 12, and the magnetization direction of the permanent magnet 11 between each pair of adjacent plastic magnetic bodies 12 is consistent with the direction of the magnetic lines of force at the position of the permanent magnet 11. In other words, when the magnetization directions of two adjacent permanent magnets 11 (i.e., the direction of the magnetic lines of force formed) are towards each other, the magnetization direction of the plastic magnetic body 12 between them (i.e., the direction of the magnetic lines of force formed) is radially from the outside to the inside. When the magnetization directions of two adjacent permanent magnets 11 (i.e., the direction of the magnetic lines of force formed) are away from each other, the magnetization direction of the plastic magnetic body 12 between them (i.e., the direction of the magnetic lines of force formed) is radially from the inside to the outside.

[0032] In this way, a closed magnetic field line can be formed between the outer rotor 1 and the stator 2. The multiple permanent magnets 11 and multiple plastic magnetic bodies 12 of this application form a Halbach magnetic pole array.

[0033] by Figure 2 Taking the example shown, both the permanent magnet 11 and the plastic magnetic body 12 are referred to as magnetic tiles. Compared with conventional external rotors, the external rotor 1 of the Halbach magnetic pole array has the advantage that the magnetic concentration effect can be obtained through the reasonable arrangement of radially magnetized magnetic tiles and tangentially magnetized magnetic tiles.

[0034] Understandably, when all magnets are radially magnetized, the magnetic field lines on the radially inner side (air gap side) of the magnet are directed from left to right, and the magnetic field lines on the radially outer side (rotor yoke side) are directed from right to left. In the case of only tangential magnets, the magnetic field lines on the radially inner side (air gap side) of the magnet are directed from left to right, and the magnetic field lines on the radially outer side (rotor yoke side) of the magnet are also directed from left to right.

[0035] In the case of a combination of radially and tangentially magnetized magnetic tiles, the magnetic field lines on the radially inner side (air gap side) of the magnetic tile are directed from left to right, which superimposes with the magnetic field lines generated by the radially magnetized magnetic tile from left to right, thus increasing the number of magnetic field lines and enhancing the magnetization effect. Conversely, the magnetic field lines on the radially outer side (rotor yoke side) of the magnetic tile are directed from right to left, which cancels out the magnetic field lines generated by the radially magnetized magnetic tile from left to right, thus weakening the magnetic field lines on the rotor yoke side.

[0036] Thus, the magnetic flux flowing in the external rotor yoke 17 is very small, so there is no need to pay too much attention to whether the rotor yoke 17 has magnetic saturation issues, and there is no need to worry about the negative impact of magnetic saturation on the motor's operating torque range and efficiency. This not only enhances the air gap magnetic density of the outer rotor 1 and the air gap magnetic field strength of the outer rotor 1, but also improves the power density of the motor.

[0037] In this application, a plastic magnetic body 12 is formed by filling with plastic magnetic material, and multiple permanent magnets 11 are connected to complete the rotor ring. The multiple permanent magnets 11, together with the multiple plastic magnetic bodies 12, form multiple magnetic poles. After the plastic magnetic material is formed, magnetization is performed using tooling to achieve an adjacent alternating arrangement of radial and tangential magnetization in the space of the outer rotor 1. By controlling the forming path of the plastic magnetic material during the process of encapsulating the permanent magnets 11, the size and physical shape of the magnetic poles of the plastic magnetic body 12 can be controlled.

[0038] In this application, the plastic magnetic body 12 is easily configured through injection molding and has plastic coating characteristics, connecting the permanent magnet 11 poles and the plastic magnetic poles into a complete magnetic ring, which can effectively control the manufacturing cost of the outer rotor 1. The outer rotor 1 does not require too many processing steps, which is beneficial to the overall motor cost in terms of materials and manufacturing.

[0039] In this application, the plastic magnetic body 12 and all the plastic magnetic parts mentioned below are injection molded magnets. During injection molding, the permanent magnet 11 is first placed in the mold cavity, and then the plastic magnetic powder is injected into the mold cavity, filling the micro-pits and micro-gaps on the surface of the permanent magnet 11. After the plastic magnetic powder is cured and formed, the resulting plastic magnetic body 12 and each plastic magnetic part can be firmly connected to the permanent magnet 11 without the need for adhesive to be applied to the permanent magnet 11.

[0040] In this application, such as Figure 3 As shown, the central axis L2 of each permanent magnet 11 is tangentially inclined relative to the central axis L1 of the outer rotor 1. Here, the central axis L2 of the permanent magnet 11 refers to the line connecting the center points of the two end faces of the permanent magnet 11 along its axial direction. Figure 3 For example, the two axial end faces of the permanent magnet 11 are the first end face F1 and the second end face F2, respectively. The center point of the first end face F1 is q1, and the center point of the second end face F2 is q2. In a conventional external rotor, the line q1q2 connecting the center points of the two axial end faces of the permanent magnet is parallel to the central axis of the external rotor. In the present application, the line q1q2 is inclined relative to the central axis L1 of the external rotor 1, and it is inclined along the tangential direction of the permanent magnet 11.

[0041] It is understandable that the tangential direction refers to the direction perpendicular to the q1L1 plane. That is to say, point q2 can be located on either side of the q1L1 plane.

[0042] Of course, in this application, the centerline L2 of all permanent magnets 11 is tangentially inclined relative to the central axis L1 of the outer rotor 1, and the inclination direction is the same. Specifically, facing the first end face F1, the q2 point of all permanent magnets 11 is located on one side of the clockwise direction of its q1L1 plane, or the q2 point of all permanent magnets 11 is located on one side of the counterclockwise direction of its q1L1 plane.

[0043] In this application, the permanent magnet 11 is tilted because traditional permanent magnet motors, which are parallel to the central axis of the outer rotor, inevitably experience some manufacturing deviations, leading to vibration and noise risks. Conventional optimization methods are unlikely to solve these problems. However, by tilting the permanent magnet 11, this application significantly reduces the harmonic content. Reducing the harmonic content in the air gap magnetic field can effectively improve the vibration and noise caused by manufacturing deviations and reduce the sensitivity of vibration and noise to the manufacturing process.

[0044] Of course, in conventional solutions, tilting the magnetic tiles makes manufacturing extremely difficult and requires very high technical skill. This application addresses the Halbach pole tilting problem by connecting adjacent permanent magnets 11 with a plastic magnetic material, thus improving manufacturability.

[0045] In some embodiments, the angle between the central axis L2 of the permanent magnet 11 and the central axis L1 of the outer rotor 1 is α1, which satisfies: 360° / LCM(Z, Np)≤α1≤0.8*360° / Z.

[0046] Where LCM is the least common multiple, Z is the number of stator slots 211 on the inner stator 2 of the outer rotor 1, and Np is the number of poles of the outer rotor 1. It is understandable that the number of poles of the outer rotor 1 may be equal to or different from the number of permanent magnets 11. For example, the outer rotor 1 may have 14 poles, 7 pole pairs, and 28 permanent magnets 11.

[0047] Here, LCM(Z, Np) refers to the least common multiple of the number of stator slots Z and the number of poles Np of the external rotor. 360° / LCM(Z, Np) is calculated by dividing 360° by this least common multiple, assuming the result is angle x1. Dividing 360° by the number of stator slots Z and then multiplying by 0.8 yields angle x2. α1 lies between x1 and x2.

[0048] It's understandable that skewed poles can improve motor vibration and noise to some extent, but they also reduce back EMF. In some applications, the reduced back EMF from skewed poles has little impact on motor performance. However, in other applications, the reduced back EMF can lead to a decrease in motor performance.

[0049] like Figure 4 In some specific embodiments shown, the trend analysis of the 2p-order noise and back EMF effective value generated by the external rotor 1 with the change of the skew angle α1 shows that when α1 is selected between x1 and x2, the noise is improved to a certain extent, while the motor performance loss is also small. Figure 4 In this context, p represents the number of pole pairs, and 2p is equal to the number of poles Np of the outer rotor.

[0050] In some embodiments of this application, such as Figure 1As shown, the outer rotor 1 of the motor also includes a rotor yoke 17, which is fitted radially outside the permanent magnet 11 and the plastic magnet body 12. This improves the support for the permanent magnet 11 and the plastic magnet body 12, withstands the centrifugal force and torque transmission generated when the outer rotor 10 rotates at high speed, and resists vibration and impact. This improves the structural reliability of the outer rotor 1. Moreover, the thickness of the rotor yoke 17 can be controlled to be relatively thin, and the overall size is controllable.

[0051] Some rotor yoke rings 17 are made of soft magnetic materials, which are easy to demagnetize after magnetization and have no residual magnetism. They are suitable for alternating magnetic field or dynamic magnetic field scenarios, which helps to form efficient magnetic flux and reduce magnetic energy loss.

[0052] In other embodiments, the rotor yoke 17 on the outer rotor 1 of the motor can be omitted, meaning the permanent magnets 11 are fixedly connected to form a rotor ring by the plastic magnetic material, eliminating the need for external support from the rotor yoke 17. This design, due to the high efficiency of magnetic flux conduction after the plastic magnetic material is magnetized, can also reduce magnetic energy loss.

[0053] Specifically, such as Figure 1 As shown, when the outer rotor 1 also includes a rotor yoke 17, the plastic magnet body 12 is integrally injection molded to fix the permanent magnet 11 and the rotor yoke 17. This can improve the connection between the rotor yoke 17 and the permanent magnet 11 and improve the overall torsional resistance.

[0054] Furthermore, the rotor yoke 17 is a metal ring with good magnetic permeability. Optionally, the rotor yoke 17 is made of steel by stretching or machining.

[0055] Specifically, the rotor yoke 17 is a steel ring, formed by stretching or rolling the steel ring. This results in a seamless or minimally seamless rotor yoke 17, providing excellent centrifugal resistance, continuous fiber flow, high strength utilization, strong structural integrity, and more reliable mechanical properties.

[0056] In some specific embodiments, such as Figure 1 As shown, the permanent magnet 11 is a rectangular sheet. Alternatively, the permanent magnet 11 can be an arc-shaped sheet arranged around the central axis of the outer rotor 1, i.e., the permanent magnet 11 is tile-shaped. This type of permanent magnet 11 has a simple structure, high processing efficiency, and low cost, which is beneficial for controlling the cost of the outer rotor 1 and for controlling the radial dimension (i.e., thickness) of the outer rotor 1, thus facilitating the miniaturization design of the motor. Of course, it is also possible that in some designs, the permanent magnet 11 is formed into a trapezoidal or other shapes in the cross-section perpendicular to the axis of the outer rotor 1.

[0057] Preferred, the permanent magnet 11 is sintered ferrite. The raw materials for permanent magnet 1 are readily available and low in cost, the production process is simple, and the magnetism is stable after magnetization. Of course, other types of materials can also be used for permanent magnet 11.

[0058] In some embodiments, such as Figure 5 As shown, the outer rotor 1 further includes a first radially outer plastic magnetic part 13, which is connected to the radially outer side of the permanent magnet 11. The first radially outer plastic magnetic part 13 is integrally injection molded to the permanent magnet 11. This increases the area of ​​the plastic magnetic material covering the permanent magnet 11, improving the connection reliability.

[0059] Especially when the outer rotor 1 also includes a rotor yoke 17, the first outer diameter plastic magnetic part 13 fills the gap between the permanent magnet 11 and the rotor yoke 17, and the magnetic resistance between the permanent magnet 11 and the rotor yoke 17 is reduced by utilizing the magnetic permeability of the plastic magnet.

[0060] Optionally, the gap between the permanent magnet 11 and the rotor yoke 17 is filled with plastic magnetic material to form a first radial plastic magnetic part 13.

[0061] Specifically, such as Figure 5 As shown, the outer rotor 1 also includes a second outer diameter plastic magnetic part 15, which is connected to the radially outer side of the plastic magnetic body 12. The second outer diameter plastic magnetic part 15, the first outer diameter plastic magnetic part 13, and the plastic magnetic body 12 are integrally injection molded. That is, the second outer diameter plastic magnetic part 15, the first outer diameter plastic magnetic part 13, and the plastic magnetic body 12 are formed as a whole, the permanent magnet 11 is covered by a large area of ​​plastic magnetic material, and at both circumferential ends of the permanent magnet 11 (i.e., the ends where the permanent magnet is connected to the plastic magnetic body 12), it is connected and covered by the outer second outer diameter plastic magnetic part 15 and the first outer diameter plastic magnetic part 13, which reduces the stress concentration of the plastic magnetic material at both circumferential ends of the permanent magnet 11. Especially when the rotor yoke ring 17 is eliminated from the outer rotor 1, this design can form the entire plastic magnetic material into a complete ring, reducing stress concentration points and lowering the possibility of breakage at the connection with the permanent magnet 11.

[0062] Specifically, the magnetization direction of the outer plastic magnet part 13 is consistent with the magnetization direction of the permanent magnet 11 on its inner radial side. This can further reduce the magnetic reluctance between the permanent magnet 11 and the rotor yoke 17.

[0063] Specifically, the magnetization direction of the outer plastic magnetic part 15 is consistent with the magnetization direction of the inner plastic magnetic body 12. This reduces the magnetic reluctance loss between the two.

[0064] In some embodiments, the outer rotor 1 further includes a first outer diameter plastic magnetic portion 13 and a second outer diameter plastic magnetic portion 15. That is, a plastic magnetic ring is wrapped around the radial outer side of the magnetic ring formed by the permanent magnet 11 and the plastic magnetic body 12.

[0065] Optionally, such as Figure 6 As shown, the radial dimension of the first outer diameter plastic magnetic part 13 is d1, which satisfies d1≥1.5mm. In this way, sufficient bonding force can be provided for the magnetic ring formed by the permanent magnet 11 and the plastic magnetic body 12.

[0066] In some embodiments, such as Figure 5 As shown, the outer rotor 1 of the motor further includes: a first inner diameter plastic magnetic part 14 and a second inner diameter plastic magnetic part 16. The first inner diameter plastic magnetic part 14 is connected to the radially inner side of the permanent magnet 11, and its magnetization direction is consistent with the magnetization direction of the permanent magnet 11 on its radially outer side. The second inner diameter plastic magnetic part 16 is connected to the radially inner side of the plastic magnetic body 12, and its magnetization direction is consistent with the magnetization direction of the plastic magnetic body 12 on its radially outer side. The first inner diameter plastic magnetic part 14, the second inner diameter plastic magnetic part 16, the first outer diameter plastic magnetic part 13, the second outer diameter plastic magnetic part 15, and the plastic magnetic body 12 are integrally injection molded and encapsulate the permanent magnet 11. In this way, the permanent magnet 11 is covered with plastic magnetic material all around its cross-section. The annular structure formed by this plastic magnetic material has greater strength, and the possibility of breakage at the connection between the plastic magnetic material and the permanent magnet 11 after impact is lower.

[0067] In some embodiments, such as Figure 7 As shown, the outer rotor 1 further includes at least one shaft-end plastic magnetic ring 19, which is located at one axial end of the permanent magnet 11 and the plastic magnetic body 12, and is connected to all the permanent magnets 11 and all the plastic magnetic bodies 12. The shaft-end plastic magnetic ring 19 and the plastic magnetic body 12 are formed by integral injection molding.

[0068] In other words, the axial dimension of the permanent magnet 11 is H2, and the axial dimension of the plastic magnetic material part is H1. The axial dimension H1 of the plastic magnetic material part exceeds the axial dimension H2 of the permanent magnet 11. Moreover, the permanent magnet 11 is wrapped by the axial end plastic magnetic ring 19 to prevent the permanent magnet 11 from axially falling off during or after the plastic coating process.

[0069] In some embodiments, such as Figure 2 As shown, the radially magnetized permanent magnet 11 or plastic magnetic body 12 occupies a central angle b1 in the outer rotor 1; the tangentially magnetized permanent magnet 11 or plastic magnetic body 12 occupies a central angle b2 in the outer rotor 1; satisfying: b1>b2.

[0070] like Figure 1 In this design, the permanent magnet 11 is magnetized radially, while the plastic magnet body 12 is magnetized tangentially. The width of a pair of inner permanent magnets 11 is in a ratio of at least 1 to the chord length of the arc of the plastic magnet body 12 distributed on the rotor yoke 17. This further improves the power density of the motor and reduces the harmonic content in the air gap magnetic field.

[0071] It is understandable that the plastic magnetic body 12 is processed by injection molding of plastic magnetic powder, and the permanent magnet 11 with a larger central angle bears more external impact force, reducing the impact on the plastic magnetic powder and reducing powder shedding. Moreover, the permanent magnet 11 has stronger magnetic stability than the plastic magnetic body 12, which is beneficial to extending the service life of the outer rotor 1.

[0072] In some embodiments, such as Figure 8As shown, the outer rotor 1 also includes a rotor end plate 18, which is located at one axial end of the outer rotor 1. The outer periphery of the rotor end plate 18 is connected to the plastic magnetic body 12 and the permanent magnet 11. In some designs, the rotor end plate 18 is also connected to a rotor yoke ring 17, etc. The rotor end plate 18 is used to support the magnetic ring and is connected to the rotating shaft 3.

[0073] In this application, the rotor end plate 18 is made of a non-magnetic material, which saves costs. For example, the rotor end plate 18 can be made of metal or plastic.

[0074] The external rotor motor 10 according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0075] According to the embodiment of the present utility model, the external rotor motor 10, with reference to... Figure 9 The system includes a stator 2 and an outer rotor 1 as described in the above embodiment, with the outer rotor 1 mounted radially outside the stator 2. This structural improvement of the outer rotor 1 enhances its air gap magnetic density and air gap magnetic field strength, thereby increasing the power density of the outer rotor motor 10.

[0076] Specifically, the stator 2 includes a stator core 21 and a coil winding 23. The stator core 21 is provided with stator slots 211 arranged circumferentially. The portion of the stator core 21 between adjacent stator slots 211 forms stator teeth 212. The coil winding 23 is wound on the stator teeth 212.

[0077] Optionally, the stator 2 may also include a mounting base and bearings, the mounting base being used for assembly and the bearings being used to support the outer rotor 1. Further, the stator 2 may include insulation at its axial ends to reduce the probability of magnetic leakage. Further optionally, the coil winding 23 is made of enameled wire.

[0078] The external rotor motor 10 of this application has a wide range of applications and can be used in various electrical appliances to meet current electrical appliance needs. This external rotor motor 10 improves the magnetic focusing ability of the permanent magnet 11, increases the amplitude of the back EMF fundamental wave, and simultaneously makes the air gap magnetic field more sinusoidal, significantly reducing harmonic content. This not only increases the power density of the external rotor motor 10 but also reduces the harmonic content in the air gap magnetic field, thus reducing the risk of electromagnetic vibration and noise generation in the external rotor motor 10.

[0079] Other components of the external rotor motor 10 according to the embodiments of the present invention, such as the electrical control system and impeller, are known to those skilled in the art and will not be described in detail here.

[0080] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An external rotor for an electric motor, characterized in that, include: Multiple permanent magnets are arranged at intervals along the circumference, and each permanent magnet is a sheet extending along the circumference; Multiple plastic magnetic bodies are filled between two adjacent permanent magnets in a one-to-one correspondence, and the plastic magnetic bodies are fixedly connected to the permanent magnets by integral injection molding; Each of the permanent magnets is radially magnetized and each of the plastic magnetic bodies is tangentially magnetized, or each of the permanent magnets is tangentially magnetized and each of the plastic magnetic bodies is radially magnetized. The magnetization directions of two adjacent permanent magnets are opposite, and the magnetization direction of each plastic magnetic body is consistent with the direction of the magnetic field formed by two adjacent permanent magnets. Furthermore, the central axis of each permanent magnet is tangentially inclined relative to the central axis of the outer rotor.

2. The external rotor of the motor according to claim 1, characterized in that, The angle between the central axis of the permanent magnet and the central axis of the outer rotor is α1, satisfying: 360° / LCM(Z,Np)≤α1≤0.8*360° / Z; Wherein, LCM is the least common multiple, Z is the number of stator slots of the motor, and Np is the number of poles of the outer rotor.

3. The external rotor of the motor according to claim 1, characterized in that, Also includes: The first outer diameter plastic magnetic part is connected to the radial outer side of the permanent magnet; The second outer diameter plastic magnetic part is connected to the radial outer side of the plastic magnetic body; The second outer diameter plastic magnetic part, the first outer diameter plastic magnetic part, and the plastic magnetic body are formed by integral injection molding.

4. The external rotor of the motor according to claim 3, characterized in that, The magnetization direction of the first outer diameter plastic magnetic part is consistent with the magnetization direction of the permanent magnet on its radial inner side, and the magnetization direction of the second outer diameter plastic magnetic part is consistent with the magnetization direction of the plastic magnetic body on its radial inner side.

5. The external rotor of the motor according to claim 3, characterized in that, The radial dimension of the first outer plastic magnetic part is d1, which satisfies d1≥1.5mm.

6. The external rotor of the motor according to claim 1, characterized in that, Also includes: At least one axial end plastic magnetic ring, the axial end plastic magnetic ring being located at one axial end of the permanent magnet and the plastic magnetic body, and being connected to all the permanent magnets and all the plastic magnetic bodies; The shaft-end plastic magnetic ring and the plastic magnetic body are formed by integral injection molding.

7. The external rotor of the motor according to claim 1, characterized in that, The radially magnetized permanent magnet or the plastic magnetic body occupies a central angle b1 in the outer rotor; The tangentially magnetized permanent magnet or the plastic magnetic body occupies a central angle b2 in the outer rotor; Satisfies: b1 > b2.

8. The external rotor of the motor according to any one of claims 1-7, characterized in that, Also includes: A rotor yoke ring, which is fitted radially outside the permanent magnet and the plastic magnet body; The plastic magnet body is fixedly connected to the permanent magnet and the rotor yoke ring by integral injection molding.

9. The external rotor of the motor according to any one of claims 1-7, characterized in that, The permanent magnet is a rectangular or arc-shaped sheet, and the permanent magnet is sintered ferrite.

10. An external rotor motor, characterized in that, include: stator; The outer rotor of the motor according to any one of claims 1-9, wherein the outer rotor is sleeved on the radially outer side of the stator.

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