Axial field permanent magnet Vernier motor

Abstract

The application discloses an axial magnetic field permanent magnet vernier motor, which comprises a rotor assembly and two stator assemblies, the rotor assembly is arranged between the two stator assemblies; the stator assembly comprises a ring-shaped stator core and a plurality of stator windings, the stator core is provided with a plurality of stator teeth on a side facing the rotor assembly, the plurality of stator teeth are arranged along the circumference of the stator core, and the stator windings are arranged in one-to-one correspondence with the stator teeth and are wound on the stator teeth; an auxiliary slot is arranged on the stator tooth, and a slot inner wall of the auxiliary slot is provided in a curved cross section. The application relates to the technical field of motors, and provides an axial magnetic field permanent magnet vernier motor, which adopts a gentle curved slot type auxiliary slot, can reduce magnetic flux leakage, thereby improving the permanent magnet utilization rate, improving the output torque density, improving the matching degree of the air gap magnetic field, and improving the output torque of the motor.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to an axial magnetic field permanent magnet vernier motor. Background Technology

[0002] There are two types of in-wheel motor drive systems for electric vehicles: direct drive and drive with a reducer. Direct drive avoids the drawbacks of long drive chains, unstable mechanical structures, susceptibility to damage, and low transmission efficiency, making it a recent hot topic in academic research and a future technological development trend. The topology of the in-wheel motor is a key technology, facing challenges such as high torque density, high power density, and small axial dimensions. Furthermore, the issue of motor heat dissipation must be fully considered and addressed.

[0003] Permanent magnet magnetic disc motors (PMDMs) possess characteristics such as high torque density, small axial dimensions, and stable and robust structure, making them promising for low-speed, high-torque direct-drive applications and thus possessing great potential as direct-drive motors for electric vehicles. Vernier motors, a new type of motor developed in recent years based on magnetic field modulation theory, can further improve the motor's torque and power density by utilizing harmonic magnetic fields. PMDMs utilize the principle of magnetic field modulation to modulate the air gap magnetic field generated by the permanent magnet and the air gap magnetic field generated by the windings. When the number of pole pairs, speed, and phase of the two are matched, stable output torque can be generated. Adding auxiliary slots to the stator teeth increases the degree of freedom in modulating the air gap magnetic field. Currently, the auxiliary slots are all right-angled grooves, with right-angle structures in the slot walls, meaning that the angle between two adjacent slot walls is a right angle. However, with the current auxiliary slot structure, the stator teeth suffer from severe magnetic leakage, which reduces the utilization rate of the permanent magnet and exacerbates motor saturation. Summary of the Invention

[0004] This invention provides an axial magnetic field permanent magnet vernier motor, including a rotor assembly and two stator assemblies, wherein the rotor assembly is disposed between the two stator assemblies;

[0005] The stator assembly includes an annular stator core and multiple stator windings. The stator core has multiple stator teeth on the side facing the rotor assembly. The multiple stator teeth are arranged circumferentially along the stator core. The stator windings are configured to correspond one-to-one with the stator teeth and are wound on the stator teeth.

[0006] The stator teeth are provided with auxiliary grooves, and the cross-section of the inner wall of the auxiliary grooves is set as a curve.

[0007] One possible design is to set the curve as a sine curve.

[0008] One possible design is that the rotor assembly includes a plurality of rotor permanent magnets, and the stator core forms stator slots between adjacent stator teeth, with the number of auxiliary slots on any stator core set to N. ao ,in:

[0009] Nao = P pm +P w –N slot And N ao / N slot =N, where N is an integer;

[0010] P pm P is set as the number of pole pairs of the rotor permanent magnet. w N is set as the number of pole pairs of the magnetic field formed by the stator windings on any of the stator components. slot The number of stator slots on any of the stator components on which the stator windings are wound is set.

[0011] One possible design is that the auxiliary slot is disposed on the end face of the stator teeth facing the rotor assembly, and the auxiliary slot is configured to penetrate the stator teeth radially along the stator core.

[0012] One possible design is that each stator tooth has one auxiliary slot, or multiple auxiliary slots are provided and arranged at equal intervals, with each auxiliary slot having the same size.

[0013] One possible design is that the opening of the auxiliary groove has a rounded corner.

[0014] One possible design is that the auxiliary slots are centrally located on the stator teeth, and all the auxiliary slots are of the same size.

[0015] One possible design includes a heat dissipation assembly comprising a heat dissipation pipe and a supply mechanism for providing a heat-conducting fluid, the output end of the supply mechanism being connected to the heat dissipation pipe, the heat dissipation pipe extending into the auxiliary tank.

[0016] In one possible design, the heat dissipation assembly includes two spaced-apart water jackets, with the stator assembly and the rotor assembly located between the two water jackets, and the two water jackets respectively connected to the output end of the liquid supply mechanism.

[0017] The axial magnetic field permanent magnet vernier motor of this invention adopts a gentle curved groove-shaped auxiliary slot, which can reduce magnetic leakage, thereby improving the utilization rate of permanent magnet, increasing the output torque density, and improving the matching degree of air gap magnetic field, thus improving the output torque of the motor.

[0018] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description and the drawings. Attached Figure Description

[0019] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0020] Figure 1 This is a partial schematic diagram of the relevant axial magnetic field permanent magnet vernier motor;

[0021] Figure 2 This is a schematic diagram of an axial magnetic field permanent magnet vernier motor according to an embodiment of the present invention;

[0022] Figure 3 for Figure 2 A schematic diagram of the first disassembled part of the axial magnetic field permanent magnet vernier motor;

[0023] Figure 4 for Figure 2 The second disassembled schematic diagram of the axial magnetic field permanent magnet vernier motor;

[0024] Figure 5 for Figure 4 Schematic diagram of the rotor permanent magnet in the middle;

[0025] Figure 6 for Figure 4 Schematic diagram of the stator core in the middle;

[0026] Figure 7 for Figure 6 A magnified view of part A in the diagram;

[0027] Figure 8 for Figure 4 A partial schematic diagram of the stator core in the middle;

[0028] Figure 9 for Figure 4 A schematic diagram of a partial cross-section of the stator core in the diagram;

[0029] Figure 10 A comparison chart of motor output torque;

[0030] Figure 11 A comparison diagram of harmonic pole pairs;

[0031] Figure 12 This is a schematic diagram of the stator module.

[0032] Reference numerals: 1-Rotor assembly, 2-Stator assembly, 3-Stator core, 4-Stator winding, 5-Rotor permanent magnet, 6-Stator tooth, 7-Stator slot, 8-Auxiliary slot, 9-Extension, 10-Top surface, 11-Transition fillet, 12-First end, 13-Second end, 14-Rotor housing, 15-Stator ring, 16-Stator module, 17-First unit. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

[0034] The related axial magnetic field permanent magnet vernier motor, as Figure 1 As shown, the auxiliary groove 8 is a right-angled groove with a right-angled structure in its groove wall. Through experiments and analysis, the applicant found that this right-angled structure causes severe magnetic leakage in the stator teeth 6, which reduces the utilization rate of the permanent magnet, exacerbates motor saturation, and results in low utilization of air gap magnetic field harmonics.

[0035] See Figures 2 to 10 The axial magnetic field permanent magnet vernier motor of this embodiment of the invention shown includes a rotor assembly 1 and two stator assemblies 2, wherein the rotor assembly 1 is rotatably disposed between the two stator assemblies 2. Each stator assembly 2 includes an annular stator core 3 and multiple stator windings 4. The stator core 3 has multiple stator teeth 6 on the side facing the rotor assembly 1, arranged circumferentially along the stator core 3. The stator windings 4 are configured to correspond one-to-one with the stator teeth and are wound on the stator teeth 6. Specifically, each stator tooth 6 has an auxiliary slot 8, the inner wall of which has a curved cross-section. Therefore, the axial magnetic field permanent magnet vernier motor uses a gently curved auxiliary slot 8, which reduces magnetic leakage, thereby improving permanent magnet utilization, increasing output torque density, and improving the matching degree of the air gap magnetic field, thus increasing the motor's output torque.

[0036] like Figure 2 , Figure 4 and Figure 5As shown, two stator assemblies 2 are spaced apart and fixed relative to the motor housing (not shown). The rotor assembly 1 is rotatably mounted between the two stator assemblies 2, and the stator assemblies 2 and rotor assembly 1 are coaxially arranged. The rotor assembly 1 has a rotor housing 14 and multiple rotor permanent magnets 5 located within the rotor housing 14. The multiple rotor permanent magnets 5 are evenly spaced around the axis of the rotor assembly 1. There is an air gap between the stator assembly 2 and the rotor assembly 1. During operation, symmetrical three-phase alternating current is passed through the stator windings 4 to form a rotating magnetic field, which interacts with the magnetic field of the rotor permanent magnets 5 to generate torque that drives the rotor to rotate, thereby driving the wheels of the electric vehicle to move.

[0037] like Figure 4 , Figures 6 to 9 As shown, the stator core 3 is annular, with multiple protruding stator teeth 6 on the side facing the rotor assembly 1. These stator teeth 6 are evenly arranged circumferentially around the stator core 3, and stator slots 7 are formed between adjacent stator teeth 6. Each stator tooth 6 extends radially along the stator core 3. The stator core 3 includes a circular annular plate-shaped stator ring body 15 and stator teeth 6 disposed on one side of the stator ring body 15. The stator teeth 6 are evenly arranged circumferentially around the stator ring body 15, and the stator ring body 15 and stator teeth 6 are integrally formed. Each stator tooth 6 has two spaced-apart extensions 9 at its end facing the rotor assembly 1, positioned on either side of the stator tooth 6, resulting in a T-shaped cross-section. The end face of the stator tooth 6 facing the rotor assembly 1 is the top surface 10. The stator slot 7 is formed by two stator teeth 6.

[0038] For example Figure 4 , Figures 6 to 9 As shown, the auxiliary groove 8 is located on the top surface 10, that is, on the end face of the stator tooth 6 facing the rotor assembly 1. The auxiliary groove 8 is formed by a recess in the top surface 10. Each stator tooth 6 has only one auxiliary groove 8, which is centrally located on the stator tooth 6. That is, the auxiliary groove 8 is centrally located on the stator tooth 6 in the circumferential direction of the stator core 3. The auxiliary groove 8 penetrates the stator tooth 6 radially along the stator core 3, forming a first end 12 and a second end 13. The first end 12 is located at the end of the auxiliary groove 8 close to the axis of the stator core 3, and the second end 13 is located at the end of the auxiliary groove 8 away from the axis of the stator core 3. However, it is not limited to this. Each stator tooth 6 is provided with multiple auxiliary slots 8. For example, there are two auxiliary slots 8 on each stator tooth 6. The two auxiliary slots 8 are evenly arranged on the stator tooth 6. That is, the stator tooth 6 is evenly arranged with two auxiliary slots 8 in the circumferential direction of the stator core 3. Each auxiliary slot 8 penetrates the stator tooth 6 along the radial direction of the stator core 3, and also forms the first end 12 and the second end 13.

[0039] In some exemplary embodiments, such as Figure 9As shown, the cross-section of the inner wall of the auxiliary groove 8 is curved, no longer having right angles or sharp corners. Specifically, this curve is a sine curve. The cross-section of the inner wall of the auxiliary groove 8 is specifically the section of the wall surface perpendicular to the extension direction, and its curve is a sine function curve, specifically a trough section of a sine curve. However, it is not limited to this; for example, the curve could also be a cosine function curve, and a segment of the cosine function curve could also be selected with the shape of the sine curve described above.

[0040] In some exemplary embodiments, such as Figure 7 and Figure 8 As shown, the width of the auxiliary groove 8 refers to its dimension perpendicular to its extension direction. The width of the auxiliary groove 8 gradually narrows from the second end 13 to the first end 12, that is, the width gradually narrows from one end away from the axis of the stator core to the other end. The groove depth of the auxiliary groove 8 is the same everywhere, that is, the groove depth of the auxiliary groove 8 remains consistent from the second end 13 to the first end 12. In addition, the groove opening of the auxiliary groove 8 is provided with a transition fillet 11, that is, there is a transition fillet 11 at the intersection of the groove wall of the auxiliary groove 8 and the top surface 10, forming an arc transition. The dimensions of each auxiliary groove 8 on the same stator core 3 are consistent, and the structures of the two stator cores 3 are also the same. During installation, the stator teeth 6 on one stator core 3 and the other stator core 3 correspond one-to-one, and the auxiliary grooves 8 also correspond one-to-one.

[0041] In some exemplary embodiments, because the stator core 3 has a complex shape, it cannot be manufactured using conventional silicon steel lamination. In this example, the stator core 3 is manufactured using powder metallurgy, forming a sinusoidal auxiliary slot 8 surface. Specifically, as... Figure 12 As shown, to simplify processing and reduce processing costs, the stator core 3 is divided into multiple stator modules 16 along its circumference. Each stator module 16 is manufactured, wound individually, and then assembled to form the stator core 3. Each stator module 16 has one stator tooth 6 and a first unit 17. The first unit 17 is a ring-shaped stator ring 15, equally divided according to the number of stator teeth 6, resembling a fan-shaped plate structure. The stator tooth 6 is centrally located on the first unit 17, and the two are manufactured as a single unit using powder metallurgy. For example, a stator core with twelve stator teeth 6 is formed by assembling twelve identical stator modules 16. After the stator modules 16 are manufactured, stator windings are first wound onto the stator teeth 6 using a winding device, and then the wound stator modules 16 are assembled into a stator assembly.

[0042] In some exemplary embodiments, the number of auxiliary slots on the stator core 3 is set to N. ao The number of pole pairs of rotor permanent magnet 5 is set to P. pm The number of pole pairs of the magnetic field formed by the stator winding 4 on any stator component 2 is set to P. wThe number of stator slots 7 on any stator assembly 2 with stator winding 4 is set to N. slot The determination of the number of auxiliary slots 8 needs to satisfy the following condition, the first condition being N. ao =P pm +P w –N slot The second condition is N ao / N slot = N, where N is an integer. Therefore, the number of auxiliary slots 8 needs to satisfy the above two formulas. In this embodiment, P pm =19, P w =5, N slot =12, therefore, based on the above formula, N is determined. ao =12, the number of auxiliary slots is 12, but not limited to this, the number can be determined according to the usage and the values ​​of each formula. Due to space constraints, the number of stator slots 7 cannot be increased indefinitely, which also limits the increase of the number of magnetic field pole pairs. The increase of the number of magnetic field pole pairs is beneficial to increasing the output torque of the motor. By increasing the number of auxiliary slots 8, the number of magnetic field pole pairs can be increased while keeping the number of slots constant, thereby increasing the output torque of the motor while keeping the number of stator slots 7 constant.

[0043] In some exemplary embodiments, the motor further includes a heat dissipation assembly (not shown in the figure), which includes a heat dissipation pipe (not shown in the figure) and a liquid supply mechanism (not shown in the figure) for providing heat-conducting fluid. The output end of the liquid supply mechanism is connected to the heat dissipation pipe and can continuously supply heat-conducting fluid to the heat dissipation pipe. Simultaneously, the heat dissipation pipe extends into the auxiliary tank 8, thereby reducing the temperature on one side of the auxiliary tank 8. In addition, the heat dissipation assembly (not shown in the figure) also includes two spaced-apart water jackets (not shown in the figure). The stator assembly 2 and the rotor assembly 1 are both located between the two water jackets. The two water jackets are respectively connected to the output end of the liquid supply mechanism, which can continuously supply heat-conducting fluid to the two water jackets, so that the water jackets and the heat dissipation pipe are connected in parallel. Thus, by introducing heat-conducting fluid into the auxiliary tank 8 through the heat dissipation pipe, and cooperating with the water jackets placed outside the two stator assemblies 2, synchronous internal and external heat dissipation is achieved, which is beneficial for controlling the temperature rise of the stator assembly 2, improving the temperature distribution of the motor, thereby enabling it to withstand higher stator currents and improving the output torque.

[0044] The "matching degree" of the air gap magnetic field refers to the degree of matching in terms of the number of pole pairs and the rotational speed of the air gap magnetic flux density harmonics generated by the permanent magnet and the stator winding 5. Only magnetic flux density harmonics with the same number of pole pairs and rotational speed can interact to generate stable torque. According to the principle of magnetic field modulation, magnetic flux density harmonics with the same number of pole pairs and the same rotational direction generated by modulation have the same rotational speed. Therefore, the key is to check whether the air gap magnetic flux density harmonics generated by the permanent magnet and the air gap magnetic flux density harmonics generated by the winding are matched after modulation, and whether they have the same number of pole pairs. Figure 10As shown, without the auxiliary slot, the "matching degree" of the air gap magnetic field is not high. The permanent magnet air gap flux density has a high 19-pole harmonic, while the winding air gap flux density has a very small 19-pole harmonic. By adding the right-angled auxiliary slot 8, the winding air gap flux density increases by 19 pole harmonics, thus matching the permanent magnet air gap flux density. However, the permanent magnet air gap flux density of 7 and 17 poles is too small to match the winding air gap flux density. The sinusoidal auxiliary slot 8, while maintaining the 19-pole winding air gap flux density harmonics, increases the permanent magnet air gap flux density of 7 and 17 poles, thereby improving the "matching degree" of the air gap magnetic field. Under the same size, current excitation, and permanent magnet quantity, the higher the "matching degree" of the air gap magnetic field, the greater the stable output torque generated. In addition, from the perspective of leakage flux, the air gap reluctance function of the right-angled auxiliary slot 8 is a step function with a sudden change. Sharp, right-angled auxiliary slots 8 are more prone to causing magnetic leakage at the tooth tips, which is the main source of magnetic leakage in vernier motors. Using a gentle, sinusoidal slot shape can reduce magnetic leakage, thereby improving permanent magnet utilization and output torque density. Therefore, optimizing the shape of the auxiliary slots 8 can improve the matching degree of the air gap magnetic field, thus increasing the motor's output torque.

[0045] For example Figure 10 As shown, under the same size, current excitation and permanent magnet usage, the motor of the sinusoidal slot type auxiliary slot 8 has a larger output torque than the motor of the right-angle type auxiliary slot 8.

[0046] In some exemplary embodiments, compared to a right-angle slotted permanent magnet vernier hub motor, the motor of this embodiment can increase the torque density (under the same output current and heat dissipation conditions) for long-term stable operation from 5.1 × 10⁻⁶. 4 Nm / m 3 Increased to 5.9×10 4 Nm / m 3 Furthermore, additional cooling water pipes can be placed in the auxiliary slot 8, which is beneficial for controlling the stator temperature rise, thereby enabling it to withstand higher stator currents and improve output torque. This permanent magnet vernier hub motor can enhance torque and power, thus improving the driving capability of electric vehicles and serving as a new generation of direct-drive hub motor topology for electric vehicles.

[0047] In conjunction with the above embodiments, the axial magnetic field permanent magnet vernier motor of the present invention adopts a gentle curved groove-shaped auxiliary groove 8, which can reduce magnetic leakage, thereby improving the utilization rate of permanent magnets, increasing the output torque density, improving the matching degree of air gap magnetic field, and thus improving the output torque of the motor.

[0048] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "one side", "the other side", "one end", "the other end", "edge", "opposite", "four corners", "perimeter", "the structure of the character 'kou'" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred structure has a specific orientation, is constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0049] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "connection", "direct connection", "indirect connection", "fixed connection", "installation", "assembly" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; the terms "installation", "connection", "fixed connection" may be directly connected, or indirectly connected through an intermediate medium, and may be the communication inside two components. 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 situations.

[0050] Although the disclosed embodiments of the present invention are as above, the described content is only the embodiments adopted for the convenience of understanding the present invention, and is not used 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 patent protection scope of the present invention shall still be defined by the appended claims.

Claims

1. An axial magnetic field permanent magnet vernier motor, characterized in that, It includes a rotor assembly and two stator assemblies, the rotor assembly being disposed between the two stator assemblies; The stator assembly includes an annular stator core and multiple stator windings. The stator core has multiple stator teeth on the side facing the rotor assembly. The multiple stator teeth are arranged circumferentially along the stator core. The stator windings are configured to correspond one-to-one with the stator teeth and are wound on the stator teeth. The stator teeth are provided with auxiliary grooves, and the cross-section of the inner wall of the auxiliary grooves is set as a curve; The auxiliary slot is disposed on the end face of the stator tooth facing the rotor assembly, and the auxiliary slot is configured to penetrate the stator tooth radially along the stator core; The width of the auxiliary slot gradually narrows from one end of the axis away from the stator core to the other end.

2. The axial magnetic field permanent magnet vernier motor according to claim 1, characterized in that, The curve is set as a sine curve.

3. The axial magnetic field permanent magnet vernier motor according to claim 1, characterized in that, The rotor assembly includes multiple rotor permanent magnets, and the stator core forms stator slots between two adjacent stator teeth. The number of auxiliary slots on any stator core is set to Nao, where: Nao = Ppm + Pw – Nslot, and Nao / Nslot = N, where N is an integer; Ppm is set to the number of pole pairs of the rotor permanent magnet, Pw is set to the number of pole pairs of the magnetic field formed by the stator winding on any of the stator components, and Nslot is set to the number of stator slots on any of the stator components on which the stator winding is wound.

4. The axial magnetic field permanent magnet vernier motor according to claim 1, characterized in that, The depth of the auxiliary grooves remains consistent.

5. The axial magnetic field permanent magnet vernier motor according to claim 1, characterized in that, The auxiliary groove has a rounded corner at the opening.

6. The axial magnetic field permanent magnet vernier motor according to claim 1, characterized in that, Each stator tooth has one auxiliary slot, or multiple auxiliary slots are provided and arranged at equal intervals, with each auxiliary slot having the same size.

7. The axial magnetic field permanent magnet vernier motor according to any one of claims 1-6, characterized in that, The device includes a heat dissipation assembly, which includes a heat dissipation pipe and a liquid supply mechanism for providing heat-conducting fluid. The output end of the liquid supply mechanism is connected to the heat dissipation pipe, and the heat dissipation pipe extends into the auxiliary tank.

8. The axial magnetic field permanent magnet vernier motor according to claim 7, characterized in that, The heat dissipation assembly includes two spaced-apart water jackets, with the stator assembly and the rotor assembly located between the two water jackets, and the two water jackets respectively connected to the output end of the liquid supply mechanism.

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