A rotor structure with a series-connected magnetic circuit of a rare-earth-free permanent magnet material

Abstract

The present invention discloses a rotor structure with a series-connected magnetic circuit of a rare-earth-free permanent magnet material, which includes a central rotating shaft, a rotor core sleeved outside the central rotating shaft, a first permanent magnet with P blocks magnetized radially, and 2P blocks of second permanent magnets magnetized tangentially. The P blocks of the first permanent magnets made of neodymium iron boron material are surface-mounted on the outer periphery of the rotor core at intervals, and the 2P blocks of the second permanent magnets made of ferrite material are radially embedded inside the rotor core. The present invention realizes the formation of a series magnetic circuit by using neodymium iron boron and ferrite permanent magnet materials. Through the design of the installation position of the permanent magnets and the included angle of the tangentially magnetized permanent magnets, the usage amount of rare-earth permanent magnet materials is reduced, the utilization rate of permanent magnet materials is improved, the output torque of the motor is increased, and the torque ripple of the motor is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet motors, and particularly relates to a rotor structure with a series magnetic circuit of rare-earth-free permanent magnet materials. Background Art

[0002] Permanent magnet synchronous motors have the advantages of simple structure, high torque density, high efficiency, and high power density. However, due to the high price of rare-earth permanent magnet materials, the manufacturing cost of motors increases. Replacing rare-earth permanent magnet materials with rare-earth-free or less-rare-earth permanent magnet materials can significantly reduce the manufacturing cost of motors. Among them, ferrite materials have a low price and are usually selected as alternative materials, but the remanence and coercivity of ferrite materials are lower than those of rare-earth materials.

[0003] In an alternating-pole permanent magnet motor, the permanent magnets are arranged with the same polarity in the radial direction, and the iron core salient poles between the permanent magnets are magnetized in the radial direction to another polarity. The polarities of the permanent magnet poles and the rotor iron poles are alternately distributed. This structure can reduce the permanent magnet usage and improve the permanent magnet utilization rate of the motor, but its air-gap magnetic density is asymmetric, and there is a problem of large torque ripple. Summary of the Invention

[0004] The purpose of the present invention is to solve the above technical problems, and provide a rotor structure with a series magnetic circuit of rare-earth-free permanent magnet materials, so as to realize the formation of a series magnetic circuit using neodymium-iron-boron and ferrite permanent magnet materials. Through the design of the installation position of the permanent magnets and the included angle of the tangentially magnetized permanent magnets, the usage of rare-earth permanent magnet materials is reduced, the utilization rate of permanent magnet materials is improved, the output torque of the motor is increased, and the torque ripple of the motor is reduced. To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] A rotor structure with a series magnetic circuit of rare-earth-free permanent magnet materials includes a central rotating shaft, a rotor iron core sleeved outside the central rotating shaft, P radially magnetized first permanent magnets, and 2P tangentially magnetized second permanent magnets. The P first permanent magnets made of neodymium-iron-boron materials are alternately surface-mounted on the outer periphery of the rotor iron core, and the 2P second permanent magnets made of ferrite materials are radially embedded inside the rotor iron core;

[0006] The inner and outer radii of the rotor iron core are r i and r o , respectively. The thickness of the first permanent magnet is h m1 . The height and width of the second permanent magnet are h m2 and w, respectively,

[0007] and satisfy the following relationship: h m1 +h m2 =r o -r i ,

[0008] The circumferential angle corresponding to the first permanent magnet is θ, and the included angle between two adjacent tangentially magnetized permanent magnets constituting a series magnetic circuit with the first permanent magnet is α,

[0009] and the following relationship is satisfied:

[0010] Specifically, the magnetization direction of the first permanent magnet points to the center of the circle, and the magnetization directions of the two second permanent magnets on both sides adjacent to the first permanent magnet are opposite to each other.

[0011] Specifically, the magnetization direction of the first permanent magnet points from the center of the circle to the outside, and the magnetization directions of the two second permanent magnets on both sides adjacent to the first permanent magnet face each other.

[0012] Specifically, salient pole structures are evenly spaced on the surface of the rotor core. The number of salient pole structures is P, and their shapes are the same as those of the first permanent magnet, and the corresponding circumferential angles and thicknesses are the same as those of the first permanent magnet.

[0013] Specifically, the salient pole structures and the first permanent magnet are alternately and evenly arranged along the circumferential surface of the rotor core, and the adjacent first permanent magnet and salient pole structure are separated by 180° / P on the circumference.

[0014] Compared with the prior art, the beneficial effects of a rotor structure with a series magnetic circuit of rare-earth-free permanent magnet materials in the present invention are mainly reflected in:

[0015] 1. By designing the installation positions of the permanent magnets, the magnetic leakage of the rotor part is reduced; 2. Using ferrite materials as the tangentially magnetized permanent magnet materials reduces the cost of the motor; 3. Through the design of surface-mounted alternating poles, the usage of rare-earth permanent magnet materials is reduced, and the utilization rate of permanent magnet materials is improved; 4. By designing the included angle of the tangentially magnetized permanent magnets, the output torque of the motor is increased; 5. Compared with the traditional alternating pole structure, the rotor structure reduces the influence of the air-gap asymmetry problem and has a lower torque ripple. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a plan view of the rotor structure according to an embodiment of the present invention;

[0017] Figure 2 is a partial plan view of the rotor structure of this embodiment;

[0018] Figure 3 is a comparison chart of the average output torque under different included angles α in this embodiment;

[0019] Figure 4 is the output torque diagram of the motor with a rotor structure of a series magnetic circuit of rare-earth-free permanent magnet materials and a traditional alternating pole rotor structure in this embodiment;

[0020] The numbers in the figures represent:

[0021] 1 Central rotating shaft, 2 rotor core, 3 first permanent magnet, 4 second permanent magnet, 5 salient pole structure. Detailed implementation manners

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0023] Embodiment:

[0024] This embodiment is a rotor structure with a series-connected magnetic circuit of a rare-earth-free permanent magnet material. As Figure 1 shown, it includes a central rotating shaft 1, a rotor core 2 sleeved outside the central rotating shaft 1, a first permanent magnet 3 with P blocks magnetized radially, and a second permanent magnet 4 with 2P blocks magnetized tangentially. The P-block first permanent magnet 3 made of neodymium iron boron material is surface-mounted at intervals on the outer periphery of the rotor core, and the 2P-block second permanent magnet 4 made of ferrite material is radially embedded inside the rotor core.

[0025] As Figure 2 shown, the inner and outer radii of the rotor core 2 are r i and r o respectively, the thickness of the first permanent magnet 3 is h m1 , the height and width of the second permanent magnet 4 are h m2 and w respectively, and the following relationship is satisfied: h m1 +h m2 =r o -r i .

[0026] The circumferential angle corresponding to the first permanent magnet 3 is θ, and the included angle between two adjacent tangentially magnetized permanent magnets that form a series magnetic circuit with the first permanent magnet 3 is α.

[0027] And

[0028] The magnetization directions of the permanent magnets include the following two methods. If the magnetization direction of the first permanent magnet 3 points to the center of the circle, the magnetization directions of the two second permanent magnets 4 on both sides adjacent to the first permanent magnet 3 are opposite; if the magnetization direction of the first permanent magnet 3 points from the center of the circle to the outside, the magnetization directions of the two second permanent magnets 4 on both sides adjacent to the first permanent magnet 3 are the same.

[0029] The surface of the rotor core 2 is provided with evenly spaced salient pole structures 5. The number of the salient pole structures 5 is P blocks, and their shapes are the same as those of the first permanent magnet 3, and the corresponding circumferential angles and thicknesses are also the same as those of the first permanent magnet 3. The salient pole structures 5 and the first permanent magnet 3 are alternately and evenly arranged along the circumferential surface of the rotor core 2, and the adjacent first permanent magnet 3 and salient pole structure 5 are separated by 180° / P on the circumference.

[0030] The following is a specific description of the rotor structure of this embodiment applied to a three-phase synchronous motor:

[0031] As Figure 1 and 2 shown, the stator adopts a double-layer fractional-slot concentrated winding structure with 12 slots, the rotor pole-pair number is 5, and the rotor magnetic poles are composed of 5 radially magnetized first permanent magnets and 10 tangentially magnetized second permanent magnets. The placement methods of the two types of permanent magnets are surface-mounted and embedded respectively, and the materials used are neodymium iron boron and ferrite. The inner diameter r i of the rotor core = 3.5 mm, the outer diameter r o = 10.1 mm, the thickness h m1 of the first permanent magnet = 0.5 mm, the height h m2 of the second permanent magnet = 6.1 mm, the width w = 1.2 mm, the circumferential angle θ corresponding to the first permanent magnet = 25.2°, and the included angle α between two adjacent tangentially magnetized permanent magnets forming a series magnetic circuit with the first permanent magnet = 28.75°. The magnetization direction of the first permanent magnet points to the center of the circle, and the magnetization directions of the two second permanent magnets on both sides adjacent to the first permanent magnet are opposite to each other.

[0032] Set the test conditions for the three-phase synchronous motor applied with the rotor structure of this embodiment. At the rated speed, a current excitation with an effective value of 1.1 A is applied to the stator side, and the included angle α between the two tangentially magnetized permanent magnets forming a series magnetic circuit with the first permanent magnet is changed. The average output torque at different included angles is as Figure 3 shown. When the included angle α = 28.75°, the average output torque is the largest, which is 218.21 mNM. This embodiment can improve the motor output torque.

[0033] Compare the motor with a traditional alternating-pole rotor structure only equipped with surface-mounted permanent magnets with the three-phase synchronous motor applied with the rotor structure of this embodiment. When the average output torque is the same, the output torque curves of the two in one cycle are as Figure 4 shown. The torque ripples of the motor with a series magnetic circuit rotor structure with less rare-earth permanent magnet materials and the traditional alternating-pole rotor structure motor are 4.25% and 6.02% respectively, showing the inhibitory effect of this embodiment on torque ripple and being able to greatly reduce the motor torque ripple.

[0034] Applying the series magnetic circuit rotor structure with less rare-earth permanent magnet materials of this embodiment has the following advantages: 1. By designing the installation position of the permanent magnets, the leakage magnetic flux of the rotor part is reduced; 2. Using ferrite material as the material of the tangentially magnetized permanent magnets reduces the cost of the motor; 3. Through the design of surface-mounted alternating poles, the usage of rare-earth permanent magnet materials is reduced and the utilization rate of permanent magnet materials is improved; 4. Through the design of the included angle of the tangentially magnetized permanent magnets, the motor output torque is increased; 5. Compared with the traditional alternating-pole structure, the rotor structure reduces the influence of the air-gap asymmetry problem and has a lower torque ripple.

[0035] In the description of the present invention, terms such as "installed", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0037] Although the disclosed embodiments of the present invention are as above, the above content is only an embodiment adopted for the convenience of understanding the present invention and is not intended to limit the present invention. Any person skilled in the art within the scope of the present invention can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A rotor structure with a series-connected magnetic circuit of a rare-earth-reduced permanent magnet material, characterized in that: It includes a central rotating shaft, a rotor core sleeved outside the central rotating shaft, a first permanent magnet magnetized radially by P blocks, and a second permanent magnet magnetized tangentially by 2P blocks. The P-block first permanent magnets made of neodymium iron boron material are surface-mounted on the outer periphery of the rotor core at intervals, and the 2P-block second permanent magnets made of ferrite material are radially embedded inside the rotor core; The inner and outer radii of the rotor core are r i and r o respectively, the thickness of the first permanent magnet is h m1 respectively, the height and width of the second permanent magnet are h m2 and w, and satisfy the following relationship: h m1 +h m2 =r o -r i , The circumferential angle corresponding to the first permanent magnet is θ, and the included angle between two adjacent tangentially magnetized permanent magnets forming a series magnetic circuit with the first permanent magnet is α. and satisfy the following relationship: α ≤ 180° / P.

2. The rotor structure with a series-connected magnetic circuit of a rare-earth-reduced permanent magnet material according to claim 1, characterized in that: The magnetization direction of the first permanent magnet points to the center of the circle, and the magnetization directions of the two second permanent magnets on the two adjacent sides of the first permanent magnet are opposite to each other.

3. The rotor structure with a series-connected magnetic circuit of a rare-earth-reduced permanent magnet material according to claim 1, characterized in that: The magnetization direction of the first permanent magnet points from the center of the circle to the outside, and the magnetization directions of the two second permanent magnets on the two adjacent sides of the first permanent magnet face each other.

4. The rotor structure with a series-connected magnetic circuit of a rare-earth-reduced permanent magnet material according to claim 1, characterized in that: The surface of the rotor core is provided with pole projection structures evenly distributed at intervals. The number of pole projection structures is P blocks, and their shapes are the same as those of the first permanent magnets, and the corresponding circumferential angles and thicknesses are the same as those of the first permanent magnets.

5. The rotor structure with a series-connected magnetic circuit of a rare-earth-reduced permanent magnet material according to claim 4, characterized in that: The pole projection structures and the first permanent magnets are alternately and evenly arranged along the circumferential surface of the rotor core, and the adjacent first permanent magnet and pole projection structure are separated by 180° / P on the circumference.

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