Rotor structure based on three-section Halbach array and motor

Abstract

The invention discloses a three-section Halbach array-based rotor structure and a motor, and belongs to the technical field of permanent magnet motors, and the three-section Halbach array-based rotor structure comprises a rotating shaft and a three-section Halbach permanent magnet pole array; each magnetic pole is an isosceles trapezoid and comprises a first permanent magnet, a second permanent magnet and a third permanent magnet which are attached in sequence; the first permanent magnet and the third permanent magnet are in the same trapezoid shape; in the same magnetic pole, the magnetizing direction of the first permanent magnet is parallel to the side waist, away from the second permanent magnet, of the first permanent magnet, the magnetizing direction of the second permanent magnet is tangential, the magnetizing direction of the third permanent magnet is parallel to the side waist, away from the second permanent magnet, of the third permanent magnet, and the difference between the magnetizing directions of the first permanent magnet and the third permanent magnet is 180 degrees; and in adjacent magnetic poles, the magnetizing directions of the corresponding first permanent magnet, second permanent magnet and third permanent magnet differ by 180 degrees. According to the invention, under the condition that the rated torque of the motor is not reduced, the use of permanent magnets of the motor is reduced, and the torque density of the motor is improved and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet motors, and more specifically, relates to a rotor structure and a motor based on a three-section Halbach array. Background Art

[0002] Rare earth permanent magnet motors are widely used in industrial fields such as electric vehicles, industrial robots, and CNC machine tools due to their many advantages such as high torque density, high efficiency, and low loss, becoming the core driving force of industrial modernization and intelligent manufacturing. In this context, the development of high-performance motor technology is crucial to the upgrading of industrial equipment. In modern high-performance motor design, the Halbach permanent magnet array has attracted much attention because it can effectively enhance the air gap magnetic field density and optimize the magnetic field distribution. It is widely used in various high-performance permanent magnet motors. At the same time, due to the magnetic shielding effect of the Halbach array, a coreless rotor can be used to further achieve the lightweight of the motor and improve the torque density.

[0003] However, the application of Halbach arrays also faces some limitations. The key to achieving its unique magnetic field characteristics lies in the complex arrangement of magnets, which usually requires more permanent magnet materials, which significantly increases the amount of magnetic steel used. With the continuous rise in the price of rare earth permanent magnet materials (such as neodymium iron boron), this material dependence not only increases the manufacturing cost, but also limits the popularity of Halbach array motors in large-scale industrial applications. Therefore, how to further improve the utilization rate of permanent magnet materials and reduce the amount of permanent magnets in Halbach permanent magnet array motors has become a key challenge in current research, which directly affects the feasibility and economy of its further promotion in the industrial field.

[0004] In the patent document with application publication number CN118611292A, an interval-type trapezoidal distributed Halbach permanent magnet array is disclosed. By adopting the interval distribution of permanent magnet poles and iron cores, the air gap magnetic field distribution can be optimized, the high-order harmonics of air gap magnetic density can be reduced, and the output torque can be increased, thereby reducing torque fluctuations. However, this structure is not suitable for coreless rotors. In the patent document with application publication number CN117543858A, an asymmetric permanent magnet motor with a combined magnetic pole Halbach structure is disclosed. In the patent document with application publication number CN114640201A, a new type of permanent magnet motor rotor based on Halbach array is disclosed. Both achieve the beneficial effects of improving air gap magnetic density, increasing torque, and suppressing torque pulsation by cooperating with built-in permanent magnets and Halbach arrays. However, both use additional permanent magnet materials inside the motor rotor, which leads to an increase in cost. Summary of the invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides a rotor structure and a motor based on a three-segment Halbach array, the purpose of which is to reduce the use of permanent magnets in the motor without reducing the rated torque of the motor, thereby improving the torque density of the motor and reducing the cost.

[0006] To achieve the above object, according to one aspect of the present invention, a rotor structure based on a three-section Halbach array is provided, comprising: a rotating shaft, and a three-section Halbach permanent magnet pole array attached to the circumferential outer surface of the rotating shaft;

[0007] In the three-section Halbach permanent magnet magnetic pole array, each magnetic pole is an isosceles trapezoid, and includes a first permanent magnet, a second permanent magnet, and a third permanent magnet that are sequentially attached; the first permanent magnet and the third permanent magnet are trapezoids of the same shape;

[0008] In the same magnetic pole, the magnetization direction of the first permanent magnet is parallel to its side away from the second permanent magnet, the magnetization direction of the second permanent magnet is tangential, the magnetization direction of the third permanent magnet is parallel to its side away from the second permanent magnet, and the magnetization direction of the first permanent magnet differs from the magnetization direction of the third permanent magnet by 180°;

[0009] In adjacent magnetic poles, the magnetizing directions of the two first permanent magnets differ by 180°, the magnetizing directions of the two second permanent magnets differ by 180°, and the magnetizing directions of the two third permanent magnets differ by 180°.

[0010] Furthermore, an included angle α∈[45°,90°) is formed between the side of the first permanent magnet away from the second permanent magnet and the lower base.

[0011] Furthermore, an included angle β∈[60°,90°] between the side waists and the lower base adjacent to the first permanent magnet and the second permanent magnet.

[0012] Furthermore, the values ​​of the angles α and β are determined as follows:

[0013] The optimization objective is to maximize the torque generated by the permanent magnet per unit area in the magnetic pole, and the angles α and β are used as optimization variables. The values ​​of α and β are determined through finite element simulation parameter scanning.

[0014] Furthermore, the gaps between adjacent magnetic poles are not filled and serve as axial cooling channels.

[0015] Furthermore, in the same magnetic pole, the electrical angle occupied by the three permanent magnets is 180°.

[0016] According to another aspect of the present invention, a motor based on a three-segment Halbach array is provided, comprising: the rotor structure based on the three-segment Halbach array provided by the present invention, and a stator located outside the rotor structure.

[0017] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0018] (1) The present invention optimizes the magnetic pole structure and magnetization direction in the three-segment Halbach array. Specifically, the magnetic pole is an isosceles trapezoid as a whole, including a second permanent magnet and a first permanent magnet and a third permanent magnet located on both sides of the second permanent magnet and having the same shape. The magnetization directions of the first permanent magnet and the third permanent magnet are parallel to the side waist away from the second permanent magnet and are 180° apart. The second permanent magnet adopts tangential magnetization. Compared with the traditional rectangular structure magnetic pole, on the one hand, the amount of permanent magnets is effectively reduced, and the cost is reduced. On the other hand, the sinusoidality of the no-load back electromotive force is improved, the harmonic content is small, and the motor torque pulsation is also reduced. In addition, it is used to enhance the unidirectional magnetic shielding effect of the Halbach array, reduce the magnetic field entering the shaft area, and thus effectively reduce leakage magnetic flux. In general, the present invention reduces the use of motor permanent magnets without reducing the rated torque of the motor by optimizing the magnetic pole magnetization direction and magnetic pole structure, thereby achieving an increase in motor torque density and a reduction in cost, and solving the problem that the Halbach array requires more permanent magnet materials.

[0019] (2) In the present invention, the angle α∈[45°, 90°] between the side of the first permanent magnet away from the second permanent magnet and the lower base is set, and this angle range can achieve a good balance between the output torque and the amount of permanent magnets used; further setting the angle β∈[60°, 90°] between the side of the first permanent magnet and the second permanent magnet adjacent to the lower base can further increase the output torque and reduce the amount of permanent magnets used.

[0020] (3) In the preferred embodiment of the present invention, the maximum torque generated by the permanent magnet per unit area in the magnetic pole is taken as the optimization target, and the angles α and β are taken as the optimization variables. The values ​​of α and β are determined by finite element simulation parameter scanning, thereby maximizing the output torque of the motor.

[0021] (4) In the present invention, since the magnetization direction of each permanent magnet in the magnetic pole is optimized, there is no need to fill the magnetic conductive material between adjacent magnetic poles for magnetization; in the preferred embodiment of the present invention, the gap between adjacent magnetic poles is not filled, but serves as an axial cooling channel, thereby improving the rotor cooling effect when the motor is in working state without affecting the electromagnetic performance of the motor.

[0022] (5) In a preferred embodiment of the present invention, in the same magnetic pole, the electrical angle occupied by the three permanent magnets is 180°. Under this configuration, adjacent magnetic poles are in contact with each other, maximizing space utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A schematic diagram of a rotor structure based on a three-segment Halbach array provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the structure of two adjacent magnetic poles provided by an embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the magnetic field line distribution of the traditional rectangular three-section Halbach pole;

[0026] Figure 4 A schematic diagram of the magnetic field line distribution of a trapezoidal three-section Halbach pole provided in an embodiment of the present invention;

[0027] Figure 5 A comparison diagram of the no-load back electromotive force of a motor based on a three-segment Halbach array provided in an embodiment of the present invention and a conventional motor based on a three-segment Halbach array;

[0028] Figure 6 A comparison diagram of no-load back-EMF harmonic content of a motor based on a three-segment Halbach array provided in an embodiment of the present invention and a conventional motor based on a three-segment Halbach array;

[0029] Figure 7 Torque waveform diagram of a motor based on a three-segment Halbach array provided in an embodiment of the present invention and a conventional motor based on a three-segment Halbach array under the same current;

[0030] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0031] 1- Rotating shaft;

[0032] 2-magnetic pole; 21-first permanent magnet, 22-second permanent magnet, 23-third permanent magnet;

[0033] 3- axial cooling channel;

[0034] 4-motor air gap;

[0035] 5- stator; 51- stator core, 52- stator winding. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0038] In order to reduce the use of permanent magnets in the motor without reducing the rated torque of the motor, to achieve an increase in the torque density of the motor and a reduction in the cost, and to solve the problem that the Halbach array requires more permanent magnet materials, the present invention provides a rotor structure and a motor based on a three-section Halbach array, the overall concept of which is to optimize the magnetic pole structure and the magnetization direction, and to cut the permanent magnets along the trajectory of the magnetic lines of force, so as to ensure that the amount of permanent magnets is reduced while fully utilizing the magnetic field generated by the permanent magnets, thereby improving the utilization rate of the permanent magnets without reducing the rated output torque of the motor and reducing the material cost.

[0039] The following are examples.

[0040] Embodiment 1:

[0041] A rotor structure based on a three-section Halbach array, such as Figure 1 , Figure 2 As shown, it includes: a rotating shaft 1, and a three-section Halbach permanent magnet pole array attached to the circumferential outer surface of the rotating shaft 1;

[0042] In the three-section Halbach permanent magnet magnetic pole array, each magnetic pole 2 is an isosceles trapezoid, and includes a first permanent magnet 21, a second permanent magnet 22 and a third permanent magnet 23 which are sequentially attached; the first permanent magnet 21 and the third permanent magnet 23 are trapezoids of the same shape;

[0043] In the same magnetic pole, the magnetization direction of the first permanent magnet 21 is parallel to its side away from the second permanent magnet 22, the magnetization direction of the second permanent magnet 22 is tangential, the magnetization direction of the third permanent magnet 23 is parallel to its side away from the second permanent magnet 22, and the magnetization direction of the first permanent magnet 21 differs from the magnetization direction of the third permanent magnet 23 by 180°;

[0044] In adjacent magnetic poles, the magnetizing directions of the two first permanent magnets 21 differ by 180°, the magnetizing directions of the two second permanent magnets 22 differ by 180°, and the magnetizing directions of the two third permanent magnets 23 differ by 180°.

[0045] The rotor structure provided in this embodiment is a coreless rotor structure. In the traditional three-segment Halbach array rotor coreless motor, the magnetic pole is rectangular as a whole, and the three segments of permanent magnets in the magnetic pole are also rectangular; in the same magnetic pole, the middle permanent magnet is tangentially magnetized, and the permanent magnets on both sides are radially magnetized. The magnetic lines of force are as follows: Figure 3 As shown. Figure 3It can be seen that the traditional three-stage Halbach array rotor-coreless motor has serious magnetic leakage, and the magnetic field generated by the permanent magnet cannot be fully utilized.

[0046] Based on the above findings, the present embodiment improves the rotor magnetic pole structure and magnetization direction, and cuts the permanent magnets along the trajectory of the magnetic force lines, so that the shapes of the permanent magnets on both sides of the same magnetic pole are improved to trapezoidal. At the same time, since the magnetization direction of the permanent magnets is parallel to the side waist of the trapezoidal structure, the magnetic force lines in the overall Halbach array are distributed as follows: Figure 4 As shown. Figure 4 and Figure 3 It can be seen that the magnetic flux leakage phenomenon is significantly improved in this embodiment, and the magnetic field generated by the permanent magnet is more fully utilized, so that the output torque density can be improved. At the same time, by cutting the permanent magnet, the amount of permanent magnet used is reduced.

[0047] In order to ensure a good balance between the amount of permanent magnets used and the output torque, in this embodiment, the angle α∈[45°,90°] between the side waist of the first permanent magnet away from the second permanent magnet and the lower base, and the angle β∈[60°,90°] between the side waist adjacent to the second permanent magnet and the lower base.

[0048] When β=90°, the first permanent magnet and the third permanent magnet are both trapezoidal, and the second permanent magnet is rectangular.

[0049] As a preferred implementation, in this embodiment, the values ​​of the angles α and β are specifically determined by the following method:

[0050] The optimization objective is to maximize the torque generated by the permanent magnet per unit area in the magnetic pole, and the angles α and β are used as optimization variables. The values ​​of α and β are determined through finite element simulation parameter scanning.

[0051] Optionally, in this embodiment, N42UH grade neodymium iron boron rare earth permanent magnet material is used.

[0052] like Figure 4 As shown, since the present embodiment optimizes the magnetic pole structure and magnetization direction, no magnetic conductive material is required between adjacent magnetic poles for magnetic conduction. Therefore, in the present embodiment, the gap between adjacent magnetic poles is not filled, and serves as an axial cooling channel 3. Under the condition of forced air cooling, efficient cooling of the permanent magnets of the motor can be achieved to avoid demagnetization caused by high temperature. When other cooling methods are used, cooling oil and other cooling media can also be introduced into the axial cooling channel accordingly.

[0053] By adjusting the electrical angle occupied by the three permanent magnets in the same magnetic pole, the gap size between adjacent magnetic poles can be adjusted. As a preferred implementation, in this embodiment, the electrical angle occupied by the three permanent magnets in the same magnetic pole is 180°. Figure 1 and Figure 2 As shown, two adjacent magnetic poles are in contact with each other, and the axial cooling channel between the magnetic poles is triangular; in some other embodiments of the present invention, the electrical angle occupied by the three permanent magnets in the same magnetic pole may also be less than 180°. In this case, the axial cooling channel between the magnetic poles is trapezoidal.

[0054] Embodiment 2:

[0055] A motor based on a three-stage Halbach array, such as Figure 1 As shown, it includes: a rotor structure based on a three-segment Halbach array provided in the above-mentioned embodiment 1, and a stator 5 located outside the rotor structure;

[0056] There is a motor air gap 4 between the stator 5 and the rotor structure; the stator includes a stator core 51 and a stator winding 52 .

[0057] The following is a 48-slot 40-pole high torque density permanent magnet synchronous motor as an example to further analyze and illustrate the beneficial effects that can be achieved by the present invention. The motor adopts fractional slot concentrated winding, the number of conductors per slot is 24, the rotor outer diameter is 102 mm, the stator outer diameter is 120 mm, the air gap length is 1 mm, the magnetic pole thickness is 7.4 mm, and the N42UH brand neodymium iron boron rare earth permanent magnet material is used. Based on the above optimization design, in this embodiment, α is 76.5° and β is 87°. At this time, the permanent magnet area under each pole is 100.2 mm 2 , compared to the 114.2mm permanent magnet area of ​​the conventional three-stage Halbach magnetization 2 A decrease of 12.3%.

[0058] The comparison diagram of the no-load back electromotive force between the motor based on the three-segment Halbach array provided by the present invention and the conventional motor based on the three-segment Halbach array is shown in FIG. Figure 5 As shown, the corresponding back EMF harmonic contrast is Figure 6 As shown, based on Figure 5 and Figure 6 It can be seen from the comparison that the present invention achieves an increase in the fundamental wave content, a reduction in the harmonic content, and a better sinusoidal property of the no-load back electromotive force, and therefore can effectively reduce the torque pulsation.

[0059] The torque waveforms of the motor based on the three-stage Halbach array provided by the present invention and the conventional motor based on the three-stage Halbach array under the same driving current are further compared. When the effective value of the driving current is the same as 120A, the torque waveforms of the two motors are compared. Figure 7As shown, the average torque of the rotor coreless permanent magnet motor of the three-stage Halbach array provided by the present invention is 536.1N·m, the torque pulsation is 20.1N·m, and the torque pulsation percentage is 3.74%; the average torque of the conventional three-stage Halbach array rotor coreless permanent magnet motor is 533.0N·m, the torque pulsation is 24.2N·m, and the torque pulsation percentage is 4.54%. By comparison, it can be seen that under the condition of reducing the amount of permanent magnets by 12.3%, the present invention achieves a similar average torque and a smaller torque pulsation.

[0060] In general, this embodiment can achieve the following effects by improving the structure and magnetization direction of the magnetic poles in the Halbach permanent magnet magnetic pole array:

[0061] (1) Under the condition of reducing the amount of permanent magnets used, the same torque as the existing three-stage Halbach structure is achieved, the utilization rate of rare earth permanent magnets is improved, and the torque density is improved;

[0062] (2) The no-load back EMF has a higher sinusoidal degree, the harmonic content is reduced, and the torque pulsation of the torque motor is smaller;

[0063] (3) It is beneficial to enhance the unidirectional magnetic shielding effect of the Halbach array and reduce the magnetic field entering the shaft area.

[0064] (4) An axial cooling channel is left between the permanent magnets of the rotor poles, which can achieve efficient cooling of the motor permanent magnets and avoid demagnetization caused by high temperature.

[0065] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A rotor structure based on a three-stage Halbach array, characterized in that: include: A rotating shaft, and a three-section Halbach permanent magnet pole array attached to the circumferential outer surface of the rotating shaft; In the three-section Halbach permanent magnet magnetic pole array, each magnetic pole is an isosceles trapezoid, and includes a first permanent magnet, a second permanent magnet and a third permanent magnet that are sequentially attached; the first permanent magnet and the third permanent magnet are trapezoids of the same shape; In the same magnetic pole, the magnetization direction of the first permanent magnet is parallel to the side away from the second permanent magnet, the magnetization direction of the second permanent magnet is tangential, the magnetization direction of the third permanent magnet is parallel to the side away from the second permanent magnet, and the magnetization direction of the first permanent magnet differs from that of the third permanent magnet by 180°; In adjacent magnetic poles, the magnetizing directions of the two first permanent magnets differ by 180°, the magnetizing directions of the two second permanent magnets differ by 180°, and the magnetizing directions of the two third permanent magnets differ by 180°.

2. The rotor structure based on the three-section Halbach array according to claim 1, characterized in that: The included angle α∈[45°,90°] between the side of the first permanent magnet away from the second permanent magnet and the lower base.

3. The rotor structure based on the three-section Halbach array according to claim 2, characterized in that: An included angle β∈[60°,90°] between the side waists and the lower bases adjacent to the first permanent magnet and the second permanent magnet.

4. The rotor structure based on the three-section Halbach array according to claim 3, characterized in that: The angles α and β are determined as follows: The optimization objective is to maximize the torque generated by the permanent magnet per unit area in the magnetic pole, and the angles α and β are used as optimization variables. The values ​​of α and β are determined through finite element simulation parameter scanning.

5. The rotor structure based on the three-segment Halbach array according to any one of claims 1 to 4, characterized in that: The gaps between adjacent poles are not filled and serve as axial cooling channels.

6. The rotor structure based on the three-section Halbach array according to claim 5, characterized in that: In the same magnetic pole, the electrical angle occupied by the three permanent magnets is 180°.

7. A motor based on a three-stage Halbach array, characterized in that: include: A rotor structure based on a three-segment Halbach array as described in any one of claims 1 to 6, and a stator located outside the rotor structure.

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