Outer rotor of electric motor, outer rotor motor and fan

Abstract

The utility model discloses an outer rotor of motor, outer rotor motor and fan relates to motor field. Outer rotor includes: a plurality of permanent magnet, the permanent magnet is all the sheet body of extension setting along the circumference direction, a plurality of plastic magnet main part, a plurality of plastic magnet main part one to one correspondingly fills between two adjacent permanent magnet, and plastic magnet main part is fixedly connected permanent magnet through integrated injection molding. Each permanent magnet is radial magnetization, and the magnetization direction of two adjacent permanent magnet is opposite, and each plastic magnet main part is tangential magnetization, and the magnetization direction is consistent with the magnetic field direction formed by two adjacent permanent magnet. This outer rotor can not only enhance the air gap magnetic density of motor, improve the power density of motor, and can effectively control the manufacturing cost of outer rotor.

Description

Technical Field

[0001] This utility model relates to the field of electric motors, specifically to an external rotor of an electric motor, an external rotor motor, and a fan. 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] Most external rotor brushless motors use the housing sheath as the rotor yoke, with tile-shaped magnets surface-mounted on the outer rotor yoke. The magnetization direction of the magnets is usually radial. The stator assembly includes a stator core made of several stacked silicon steel sheets, end insulation mounted on the end faces of the stator core, and coil windings wound on the end insulation. The advantage of this type of motor is its simple structure and the ease of implementing the process of surface-mounting the magnets on the outer rotor yoke. However, this type of motor only utilizes the magnetic lines of force on one side of the magnet; that is, only the inner magnetic lines of force of the magnet link with the windings (i.e., the induced components) to generate a magnetic field, while the outer magnetic lines of force of adjacent magnets form their own loops through the rotor yoke and do not link with the windings.

[0004] Furthermore, given a fixed air gap thickness and rotor sleeve, a large magnetic load in this type of motor can easily increase the magnetic flux density of the rotor sleeve, leading to magnetic flux oversaturation. The yoke rings are also prone to significant eddy current losses in a high-speed rotating magnetic field. Rotor yoke ring magnetic flux oversaturation affects motor torque output and efficiency, thus necessitating rotor improvements for this type of motor. Utility Model Content

[0005] 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 can alleviate the problem of rotor yoke magnetic flux density oversaturation and increase the linkage between the rotor magnetic lines of force and the inducted portion of the stator, thereby improving motor efficiency.

[0006] This utility model also aims to provide an external rotor motor and a fan including the above-mentioned external rotor.

[0007] 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 the magnetization directions of two adjacent permanent magnets are opposite; each of the plastic magnetic bodies is tangentially magnetized, and the magnetization direction is consistent with the direction of the magnetic field formed by two adjacent permanent magnets.

[0008] According to the embodiment of the present invention, the outer rotor of the motor has a plastic magnetic body between two adjacent permanent magnets, and the magnetization direction of the plastic magnetic body is consistent with the direction of the magnetic lines of force formed by the two adjacent permanent magnets at this location. As a result, the plastic magnetic body can attract the magnetic lines of force radially outward from the permanent magnets as much as possible, so that more of the magnetic lines of force generated by the permanent magnets pass through the plastic magnetic body to form a closed magnetic circuit and intersect with the inducted part of the stator (such as the coil winding), thereby improving the magnetic utilization rate and increasing the electromagnetic driving force.

[0009] In this way, the main magnetic circuit of the outer rotor is concentrated on one side of the permanent magnet and the plastic magnet body, with only a small portion dispersed radially outward. The magnetic flux flowing externally, such as within the rotor yoke, is very small. Therefore, there is no need to worry too much about whether the rotor yoke will experience magnetic saturation, nor 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 and magnetic field strength of the outer rotor but also improves the motor's power density.

[0010] Furthermore, in this application, the permanent magnet is radially magnetized, with the inner radial end of the permanent magnet being either an N pole or a S pole. The magnetic field lines are more dense on the inner radial side of the permanent magnet (i.e., the side of the permanent magnet facing the center point). Therefore, the magnetic field strength is greater in the part where the permanent magnet links with the stator, which can further improve the power density of the motor.

[0011] In this application, a plastic magnetic body is formed by filling it with a plastic magnetic material, and multiple permanent magnets are connected to complete the rotor ring. These permanent magnets, in conjunction with the multiple plastic magnetic bodies, form multiple magnetic poles. After the plastic magnetic material is formed, magnetization is achieved using tooling, resulting in alternating radial and tangential magnetization in the outer rotor space. By controlling the forming path of the plastic magnetic material during the process of encapsulating the permanent magnets, the size and physical shape of the magnetic poles of the plastic magnetic body can be controlled.

[0012] 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.

[0013] In some embodiments, the permanent magnet occupies a1 at the central angle of the outer rotor, and the plastic magnet occupies a2 at the central angle of the outer rotor, wherein the ratio of a1 to a2 is greater than or equal to 1.

[0014] In some embodiments, the outer rotor further includes: a first outer diameter plastic magnetic part, the first outer diameter plastic magnetic part being connected to the radial outer side of the permanent magnet, the first outer diameter plastic magnetic part being fixedly connected to the permanent magnet by integral injection molding; the first outer diameter plastic magnetic part being radially magnetized, and the magnetization direction being consistent with the magnetization direction of the permanent magnet on its radial inner side.

[0015] In some embodiments, the outer rotor of the motor further includes: a second outer diameter plastic magnetic part, the second outer diameter plastic magnetic part being 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 being integrally formed by injection molding; the second outer diameter plastic magnetic part is tangentially magnetized, and the magnetization direction is consistent with the magnetization direction of the plastic magnetic body on its radial inner side.

[0016] In some embodiments, the outer rotor of the motor further includes: a first inner diameter plastic magnet portion, which is connected to the radial inner side of the permanent magnet and whose magnetization direction is consistent with the magnetization direction of the permanent magnet on its radial outer side; a second inner diameter plastic magnet portion, which is connected to the radial inner side of the plastic magnet body and whose magnetization direction is consistent with the magnetization direction of the plastic magnet body on its radial outer side; the first inner diameter plastic magnet portion, the second inner diameter plastic magnet portion, the first outer diameter plastic magnet portion, the second outer diameter plastic magnet portion, and the plastic magnet body are integrally formed by injection molding and encapsulate the permanent magnet.

[0017] In some embodiments, the permanent magnet is a rectangular sheet, or an arc-shaped sheet around the central axis of the outer rotor; the permanent magnet is sintered ferrite.

[0018] In some embodiments, the outer rotor of the motor further includes: a rotor yoke ring, which is sleeved on the radially outer side of the permanent magnet and the plastic magnet body; the plastic magnet body is integrally injection molded to fix the permanent magnet and the rotor yoke ring.

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

[0020] Optionally, the number of poles Np of the outer rotor satisfies Np≥8.

[0021] Optionally, the stator includes a stator core and a coil winding. The stator core is provided with stator slots arranged at intervals along the circumference. The portion of the stator core between adjacent stator slots forms stator teeth, and the coil winding is wound on the stator teeth. The number of stator slots is Ns, which satisfies Ns≥12.

[0022] Optionally, the absolute value of the difference between the number of stator slots Ns and the number of poles Np of the outer rotor is between 1 and 6.

[0023] The fan according to an embodiment of the present invention includes the external rotor motor described in the above embodiment.

[0024] 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

[0025] 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 an assembly diagram of an external rotor motor according to some embodiments of the present invention; Figure 2 for Figure 1 Schematic diagram of magnetic field line distribution at local locations on the inner and outer rotors; Figure 3 This is a schematic diagram of the assembly of the outer rotor and stator cell in some other embodiments of the present invention; Figure 4 for Figure 3 A partial structural diagram of the inner and outer rotors; Figure 5 This is an assembly diagram of an external rotor motor according to other embodiments of the present invention; Figure 6 for Figure 5 Schematic diagram of magnetic field line distribution at local locations on the inner and outer rotors; Figure 7 This is a schematic diagram of the assembly of the outer rotor and stator cell in some other embodiments of the present invention; Figure 8 This is a cross-sectional schematic diagram of the outer rotor of 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; Figure 10 This is an assembly diagram of an external rotor motor according to some embodiments of the present invention; Figure 11 This is an assembly diagram of an external rotor motor according to some embodiments of the present invention; Figure 12 This is an assembly diagram of a fan according to some embodiments of the present invention.

[0026] Figure label: Fan 100 External rotor motor 10 External rotor 1, Permanent magnet 11, first permanent magnet 11-1, second permanent magnet 11-2, third permanent magnet 11-3 Plastic magnetic body 12, first body 12-1, second body 12-2, third body 12-3 First diameter outer plastic magnetic part 13, first diameter inner plastic magnetic part 14, second diameter outer plastic magnetic part 15, second diameter inner plastic magnetic part 16, rotor yoke ring 17, rotor end plate 18. Stator 2, stator core 21, stator slot 211, stator teeth 212, coil winding 23 Shaft 3. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] The external rotor 1 of the motor according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0030] 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.

[0031] 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.

[0032] Among them, such as Figure 2 As shown, each permanent magnet 11 is radially magnetized, and 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.

[0033] In other words, 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.

[0034] like Figure 2 In the example shown, the outer rotor 1 has a center point O on a section perpendicular to the axis of the outer rotor 1. Figure 2 The permanent magnet 11 of the outer rotor 1 shown includes a first permanent magnet 11-1, a second permanent magnet 11-2, and a third permanent magnet 11-3. Figure 2 The plastic magnetic body 12 of the outer rotor 1 shown includes a first body 12-1 and a second body 12-2. The first body 12-1 is located between the first permanent magnet 11-1 and the second permanent magnet 11-2, and the second body 12-2 is located between the second permanent magnet 11-2 and the third permanent magnet 11-3. The magnetization directions of the first permanent magnet 11-1, the second permanent magnet 11-2, and the third permanent magnet 11-3 are all radial, while the magnetization directions of the first body 12-1 and the second body 12-2 are both tangential.

[0035] In this configuration, the outer radial end of the first permanent magnet 11-1 is the S pole, and the inner radial end is the N pole. The outer radial end of the second permanent magnet 11-2 is the N pole, and the inner radial end is the S pole. The outer radial end of the third permanent magnet 11-3 is the S pole, and the inner radial end is the N pole. The end of the first main body 12-1 connected to the first permanent magnet 11-1 is the N pole, and the end connected to the second permanent magnet 11-2 is the S pole. The end of the second main body 12-2 connected to the second permanent magnet 11-2 is the S pole, and the end connected to the second permanent magnet 11-2 is the N pole. In other words, 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. This allows a closed magnetic field line to be formed between the outer rotor 1 and the stator 2.

[0036] The outer rotor 1 of this application solution has a plastic magnetic body 12 set between two adjacent permanent magnets 11, and the magnetization direction of the plastic magnetic body 12 is consistent with the direction of the magnetic lines of force formed by the two adjacent permanent magnets 11 at this time. As a result, the plastic magnetic body 12 can attract the magnetic lines of force radially outward of the permanent magnets 11 as much as possible, so that more of the magnetic lines of force generated by the permanent magnets 11 pass through the plastic magnetic body 12 to form a closed magnetic circuit and intersect with the inducted part of the stator 2 (such as the coil winding 23), thereby improving the magnetic utilization rate and the electromagnetic driving force.

[0037] Thus, the main magnetic circuit of the outer rotor 1 is concentrated on one side of the permanent magnet 11 and the plastic magnet body 12, with only a small portion dispersed radially outward. The magnetic flux flowing externally, such as within the rotor yoke 17, is very small. Therefore, there is no need to worry excessively about magnetic saturation in the rotor yoke 17, nor 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 and magnetic field strength of the outer rotor 1, but also improves the motor's power density.

[0038] Furthermore, in this application, the permanent magnet 11 is radially magnetized, with the inner radial end of the permanent magnet 11 being either an N pole or a S pole. The magnetic field lines on the inner radial side of the permanent magnet 11 (i.e., the side of the permanent magnet 11 facing the center point O) are more dense. Therefore, the magnetic field strength of the permanent magnet 11 in the linking part with the stator 2 is greater, which can further improve the power density of the motor.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In some embodiments of this application, such as Figure 1 As 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.

[0043] Some rotor yoke rings 17 are made of soft magnetic material, which means that they 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.

[0044] In other embodiments, such as Figure 3 and Figure 4 As shown, the rotor yoke 17 on the outer rotor 1 of the motor can be eliminated, meaning the permanent magnet 11 is 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, also reduces magnetic energy loss.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Optionally, the thickness of the rotor yoke 17 is less than or equal to 2 mm. This effectively controls the overall radial dimension of the outer rotor 1, which is beneficial for the miniaturization design of the motor.

[0049] In other embodiments, such as Figures 5-7 As shown, changing the magnetization direction on the outer rotor 1 can also achieve the above purpose.

[0050] Specifically, refer to Figures 5-7 The system includes: multiple permanent magnets 11, multiple plastic magnetic bodies 12, and a rotor yoke 17. The multiple permanent magnets 11 are arranged circumferentially at intervals, and each permanent magnet 11 is 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, and each plastic magnetic body 12 is a sheet extending circumferentially. Thus, the multiple permanent magnets 11 and the multiple plastic magnetic bodies 12 are sequentially connected to form a magnetic ring. The rotor yoke 17 is fitted radially outside the permanent magnets 11 and the plastic magnetic bodies 12, improving the support for the permanent magnets 11 and the plastic magnetic bodies 12 and constructing a closed magnetic path.

[0051] The plastic magnet body 12 is integrally injection molded to fix the permanent magnet 11 and the rotor yoke 17. This improves the connection strength between the rotor yoke 17 and the permanent magnet 11, and enhances the overall torsional resistance. For example, Figure 6 As shown, each permanent magnet 11 is tangentially magnetized, and 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.

[0052] In other words, a magnetic circuit formed by closed-loop magnetic lines of force can be formed between every two adjacent plastic magnetic bodies 12, and the magnetization direction of the permanent magnet 11 between every two adjacent plastic magnetic bodies 12 is consistent with the direction of the magnetic lines of force at the position of the permanent magnet 11. Alternatively, it can be said that when the magnetization directions of two adjacent permanent magnets 11 (i.e., the direction of the formed magnetic lines of force) are towards each other, the magnetization direction of the plastic magnetic body 12 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 permanent magnets 11 (i.e., the direction of the formed magnetic lines of force) are away from each other, the magnetization direction of the plastic magnetic body 12 between them (i.e., the direction of the formed magnetic lines of force) is radially from the inside to the outside.

[0053] like Figure 6 In the example shown, the outer rotor 1 has a center point O on a section perpendicular to the axis of the outer rotor 1. Figure 6 The permanent magnet 11 of the outer rotor 1 shown includes a first permanent magnet 11-1, a second permanent magnet 11-2, and a third permanent magnet 11-3. Figure 6 The plastic magnetic body 12 of the outer rotor 1 shown includes a first body 12-1, a second body 12-2, and a third body 12-3. Figure 6 On a quarter-section of the outer rotor 1 shown, the permanent magnets 11 and the plastic magnetic bodies 12 are arranged alternately in the following order: first permanent magnet 11-1, first body 12-1, second permanent magnet 11-2, second body 12-2, third permanent magnet 11-3, and third body 12-3. The magnetization direction of the first permanent magnet 11-1, the second permanent magnet 11-2, and the third permanent magnet 11-3 is tangential, while the magnetization direction of the first body 12-1, the second body 12-2, and the third body 12-3 is radial.

[0054] In this configuration, the end of the first permanent magnet 11-1 furthest from the first main body 12-1 is the S pole, and the end connected to the first main body 12-1 is the N pole. The end of the second permanent magnet 11-2 connected to the first main body 12-1 is the N pole, and the end connected to the second main body 12-2 is the S pole. The end of the third permanent magnet 11-3 connected to the second main body 12-2 is the S pole, and the end connected to the third main body 12-3 is the N pole. The outer radial end of the first main body 12-1 is the S pole, and the inner radial end is the N pole. The outer radial end of the second main body 12-2 is the N pole, and the inner radial end is the S pole. The outer radial end of the third main body 12-3 is the S pole, and the inner radial end is the N pole.

[0055] In other words, not only are the magnetization directions of two adjacent permanent magnets 11 opposite, but the magnetization directions of two adjacent plastic magnet bodies 12 are also opposite. In this way, a closed magnetic field line can be formed between the outer rotor 1 and the stator 2.

[0056] The outer rotor 1 of this application solution has a plastic magnetic body 12 between two adjacent permanent magnets 11, and the magnetization direction of the plastic magnetic body 12 is consistent with the direction of the magnetic lines of force formed by the two adjacent permanent magnets 11 at this location. This allows the plastic magnetic body 12 to attract the magnetic lines of force at the ends of the permanent magnets 11 as much as possible, so that more of the magnetic lines of force generated by the permanent magnets 11 pass through the plastic magnetic body 12 to form a closed magnetic circuit and intersect with the inducted part of the stator 2 (such as the coil winding 23), thereby improving magnetic utilization and electromagnetic driving force.

[0057] Thus, the main magnetic circuit of the outer rotor 1 is concentrated on one side of the permanent magnet 11 and the plastic magnet body 12, with only a small portion dispersed radially outward. The magnetic flux flowing externally, such as within the rotor yoke 17, is very small. Therefore, there is no need to worry excessively about magnetic saturation in the rotor yoke 17, nor 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 and magnetic field strength of the outer rotor 1, but also improves the motor's power density.

[0058] In this application, the permanent magnet 11 is tangentially magnetized, with the N pole and S pole at both ends of the permanent magnet 11. The magnetic lines of force dispersed to the radially outer side of the permanent magnet 11 are concentrated on the rotor yoke ring 17, reducing the leakage of magnetic lines of force.

[0059] 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.

[0060] 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 and the rotor yoke 17 are 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 and the rotor yoke 17, without the need for adhesive to be applied to the permanent magnet 11 and the rotor yoke 17.

[0061] In some specific embodiments, such as Figure 1As 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.

[0062] 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.

[0063] In some embodiments, such as Figure 1 As shown, the central angle occupied by the permanent magnet 11 on the outer rotor 1 is a1, and the central angle occupied by the adjacent plastic magnet body 12 on the outer rotor 1 is a2. The ratio of a1 to a2 is greater than or equal to 1. Figure 1 In the process, the width of the pair of inner permanent magnets 11 is not less than 1 in proportion to the arc chord length of the plastic magnetic body 12 distributed on the rotor yoke ring 17.

[0064] 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.

[0065] In some embodiments, such as Figure 1 and Figure 3 , Figure 4 As shown, the outer rotor 1 further includes a first outer diameter plastic magnetic part 13, which is connected to the radial outer side of the permanent magnet 11. The first outer diameter plastic magnetic part 13 is fixedly connected to the permanent magnet 11 by integral injection molding. This increases the area of ​​the plastic magnetic material covering the permanent magnet 11 and improves the connection reliability.

[0066] 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.

[0067] 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.

[0068] Specifically, the first radially outer plastic magnet part 13 is radially magnetized, and the magnetization direction is consistent with the magnetization direction of the permanent magnet 11 on its radially inner side. This can further reduce the magnetic reluctance between the permanent magnet 11 and the rotor yoke 17.

[0069] In some embodiments, such as Figure 4 As shown, the outer rotor 1 of the motor 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 one piece, and the permanent magnet 11 is covered by a large area of ​​plastic magnetic material. Moreover, 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.

[0070] Specifically, the outer plastic magnetic part 15 of the second diameter is tangentially magnetized, and the magnetization direction is consistent with the magnetization direction of the inner plastic magnetic body 12. This can reduce the magnetic reluctance loss between the two.

[0071] In some embodiments, such as Figure 4 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.

[0072] In some embodiments, such as Figure 8 As 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] In this application, the number of poles Np of the outer rotor 1 satisfies Np≥8. Correspondingly, the number of permanent magnets 11 is at least 8, such as... Figure 9 There are 10 permanent magnets 11 in the middle, and the number of poles Np of the outer rotor 1 is equal to 10. For example... Figure 10 There are 14 permanent magnets in the middle (11), and the number of poles Np of the outer rotor 1 is equal to 14. For example... Figure 11 There are 18 permanent magnets 11 in the middle, and the number of poles Np of the outer rotor 1 is equal to 18.

[0075] By rationally setting the number of poles Np, power density can be improved, low-speed performance optimized, and losses reduced. For example, an 8-pole or higher multi-pole design can increase electromagnetic torque by increasing the number of pole pairs without increasing the motor's outer diameter or length. Compared to 4-pole or 6-pole external rotor motors, torque can be increased by 30% to 50% within the same volume.

[0076] The external rotor motor 10 according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0077] According to the embodiment of the present utility model, the external rotor motor 10, with reference to... Figure 1 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.

[0078] 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.

[0079] 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.

[0080] In some specific embodiments, the number of poles Np of the outer rotor 1 is at least 8, and the number of stator slots 211 is Ns, satisfying Ns≥12. This ensures that the number of slots on the stator 2 matches the number of poles on the outer rotor 1, for example, 12 slots for 8 poles, or 24 slots for 16 poles. Among these, 12 slots is the optimal starting point for the number of slots in a multi-pole rotor (such as 8-pole or 10-pole), representing an ideal combination of "integer slot concentrated winding" or "short-pitch distributed winding." This results in a more uniform coverage area between the stator teeth 212 and the rotor poles, significantly reducing the "cogging torque" (magnetic reluctance torque) of the air gap magnetic field.

[0081] Optionally, the absolute value of the difference between the number of stator slots 211, Ns, and the number of poles of the outer rotor 1, Np, is between 1 and 6. This design results in high electromagnetic coupling efficiency and increased power density.

[0082] According to the embodiment of the present utility model, the fan 100, such as Figure 12 As shown, the external rotor motor 10 of the above embodiment is included. Thus, the fan 100 has higher output power and lower energy consumption.

[0083] Other components of the external rotor motor 10 and the fan 100 according to the embodiments of the present invention, such as the electrical control system and the impeller, are known to those skilled in the art and will not be described in detail here.

[0084] In this specification, the terms "embodiment," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the 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.

[0085] 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 the magnetization directions of two adjacent permanent magnets are opposite. Each of the plastic magnetic bodies is tangentially magnetized, and the magnetization direction is consistent with the direction of the magnetic field formed by the two adjacent permanent magnets.

2. The external rotor of the motor according to claim 1, characterized in that, The permanent magnet occupies a central angle a1 on the outer rotor, and the adjacent plastic magnet occupies a central angle a2 on the outer rotor, with the ratio of a1 to a2 being greater than or equal to 1.

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, and the first outer diameter plastic magnetic part is fixedly connected to the permanent magnet by integral injection molding; The first outer diameter plastic magnet is radially magnetized, and the magnetization direction is consistent with the magnetization direction of the permanent magnet on its radial inner side.

4. The external rotor of the motor according to claim 3, characterized in that, Also includes: The second outer diameter plastic magnetic part is connected to the radially 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. The second outer diameter plastic magnetic part is tangentially magnetized, and the magnetization direction is consistent with the magnetization direction of the plastic magnetic body on its inner radial side.

5. The external rotor of the motor according to claim 4, characterized in that, Also includes: The first inner diameter plastic magnetic part is connected to the radial inner side of the permanent magnet, and the magnetization direction is consistent with the magnetization direction of the permanent magnet on its radial outer side. The second inner diameter plastic magnetic part is connected to the radial inner side of the plastic magnetic body, and the magnetization direction is consistent with the magnetization direction of the plastic magnetic body on its radial outer side. The first inner diameter plastic magnetic part, the second inner diameter plastic magnetic part, the first outer diameter plastic magnetic part, the second outer diameter plastic magnetic part, and the plastic magnetic body are integrally formed by injection molding and encapsulate the permanent magnet.

6. The external rotor of the motor according to any one of claims 1-5, characterized in that, The permanent magnet is a rectangular piece, or an arc-shaped piece of the permanent magnet arranged around the central axis of the outer rotor; The permanent magnet is sintered ferrite.

7. The external rotor of the motor according to any one of claims 1-5, 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.

8. An external rotor motor, characterized in that, include: stator; The outer rotor of the motor according to any one of claims 1-7, wherein the outer rotor is sleeved on the radially outer side of the stator.

9. The external rotor motor according to claim 8, characterized in that, The number of poles Np of the outer rotor satisfies Np≥8.

10. The external rotor motor according to claim 9, characterized in that, The stator includes a stator core and a coil winding. The stator core has stator slots arranged circumferentially. The portion of the stator core between adjacent stator slots forms stator teeth. The coil winding is wound on the stator teeth. The number of stator slots is Ns, which satisfies Ns≥12.

11. The external rotor motor according to claim 10, characterized in that, The absolute value of the difference between the number of stator slots Ns and the number of poles Np of the outer rotor is between 1 and 6.

12. A fan comprising an external rotor motor according to any one of claims 8-11.

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