Motor rotors, permanent magnet motors and electric vehicles

Abstract

The present application provides a motor rotor, a permanent magnet motor and an electric vehicle. The motor rotor comprises a rotor core (1), a mounting groove (2) is arranged on the rotor core (1), the mounting groove (2) forms a V-shaped structure, the angle between the two mounting grooves (2) forming the V-shaped structure is △, a permanent magnet (3) is arranged in the mounting groove (2), the thickness of the permanent magnet (3) is L4, the width of the permanent magnet (3) is L5, wherein 110°≤△≤140°, △=(18~20)*L4, L5≥2L4. According to the motor rotor of the present application, the back electromotive force harmonics can be effectively controlled, the motor output torque can be improved, and the motor working performance can be improved.

Description

Technical Field

[0001] The present application relates to the field of motor technology, and in particular to a motor rotor, a permanent magnet motor and an electric vehicle. Background Art

[0002] Electric vehicles are the main type of new energy vehicles. Compared with traditional internal combustion engine vehicles, the power transmission system of electric vehicles has undergone major changes in power source and structure, which makes the torsional vibration of the transmission system have new characteristics. Research on how to reduce the torsional vibration of the power transmission system of electric vehicles is of great significance to improving the safety and comfort of the whole vehicle. The drive motor is the main excitation source of the steady-state torsional vibration of the transmission system, and the size and frequency characteristics of its torque fluctuation directly affect the steady-state torsional vibration response of the power transmission system.

[0003] As the core power system of electric vehicles, the drive motor plays a decisive role in the power performance and cruising range of electric vehicles. At present, permanent magnet synchronous motors, especially built-in permanent magnet synchronous motors, are widely used in the drive systems of electric vehicles because of their wide speed regulation range, high efficiency, high power density, compact structure and fast response ability. For example, the drive motors of electric vehicles such as Toyota Prius, BMW I3 and Honda Civic are all built-in permanent magnet synchronous motors. In addition, the corresponding control technology has also gradually developed and matured. Therefore, built-in permanent magnet synchronous motors have a larger development space in the field of electric vehicle drive motors, and because its rotor structure has a greater impact on motor performance and has great design flexibility, the study of the impact of rotor topology on motor performance is of great significance to promoting the development and application of built-in permanent magnet synchronous motors.

[0004] The different rotor topologies of permanent magnet synchronous motors have a great influence on the performance of the motor. Compared with the rotor structure of surface-mounted permanent magnets, the built-in type has a higher permanent magnet utilization rate and a wider constant power speed range due to the asymmetry of its rotor circuit. At the same time, the built-in permanent magnet synchronous motor also has the characteristics of great flexibility in rotor design. Therefore, the overload capacity, efficiency and power density of the motor can be improved by changing the rotor topology, and its speed regulation capability can be improved. The rotor structure of the built-in permanent magnet synchronous motor is relatively flexible and diverse in design, and different rotor topologies also have a great influence on the performance of the built-in permanent magnet synchronous motor.

[0005] There are two main reasons for the torque fluctuation of permanent magnet synchronous motors: magnetic field harmonics and inductance harmonics caused by the non-ideal structure of the motor body, and voltage harmonics and current harmonics caused by the nonlinear characteristics of the inverter. Magnetic field harmonics and inductance harmonics will also cause voltage and current harmonics in the motor control system, and harmonic currents will eventually cause motor torque fluctuations.

[0006] For permanent magnet synchronous motors, the main structure mainly includes the stator core and permanent magnets. The permanent magnets will generate magnetic flux, which is divided into radial and tangential flux. The magnetic flux enters the stator core through the motor air gap, and the magnetic flux passing along the tangential direction is less. The air gap magnetic field formed by the main pole flux will act on the rotor, causing the motor stator core and rotor to deform and form cyclic vibration. The radial electromagnetic force of the motor is the force of interaction between the stator core and the rotor. The radial electromagnetic force is the main source of electromagnetic vibration noise of the permanent magnet synchronous motor, and the radial electromagnetic force wave of the motor is closely related to the harmonic component of the motor air gap magnetic field.

[0007] The operating harmonics of permanent magnet motors are mainly divided into time harmonics and space harmonics. Time harmonics are mainly caused by the fact that the power supply connected to the motor generates harmonic voltages and harmonic currents inside the motor when it is non-sinusoidal. The nonlinearity of the power supply is mainly due to the nonlinearity of power electronic devices in the actual inverter process, mainly including the dead time and conduction voltage drop of power electronic devices. The reason for the generation of space harmonics is mainly caused by the motor body. In the design of the motor body, due to the limited number of pole pairs and slots of the motor, the rotating magnetic field generated by the stator winding during the operation of the motor is not a standard rotating magnetic field. The main factors affecting the space harmonics of the motor are the slot effect, the winding distribution form, the magnetic saturation degree of the magnetic circuit, the rotor topology, etc. In addition, there will inevitably be errors in the manufacturing process of the motor, which is impossible to be the same as the ideal state. There will be winding errors, permanent magnet rotor coaxiality deviations, etc. These factors will cause the motor to generate high-order harmonics and endanger the operation of the motor. There are two main reasons for the harmonics in the operation of permanent magnet synchronous motors: ⑴ Harmonics caused by the distortion of the air gap magnetic field inside the motor; ⑵ Since power electronic devices are not ideal devices, there will be a conduction voltage drop during the inversion process, generating harmonics.

[0008] During the operation of the motor, harmonic electromotive force will cause great harm to the operation of the motor: ⑴ Harmonic electromotive force will deteriorate the quality of the electromotive force waveform of the permanent magnet motor, resulting in reduced smoothness of the motor output torque, increased torque pulsation, and greater noise; ⑵ Harmonics will also increase the temperature rise of the motor operation, causing aging of the insulation layer of the motor components, increased losses to the motor body, and reduced the working efficiency of the motor; ⑶ The presence of high-order harmonics in the operation of the motor will generate harmonic magnetic fields in the vehicle, causing electromagnetic interference to other surrounding communications, affecting the safety of the entire vehicle operation.

[0009] Therefore, at present, how to effectively control the back EMF harmonics, increase the motor output torque, and improve the motor working performance are issues that need to be considered during the motor design process. Summary of the invention

[0010] Therefore, the technical problem to be solved by the present application is to provide a motor rotor, a permanent magnet motor and an electric vehicle that can effectively control back-EMF harmonics, increase the motor output torque and improve the motor working performance.

[0011] In order to solve the above problems, the present application provides a motor rotor, including a rotor core, a mounting groove is arranged on the rotor core, the mounting groove forms a V-shaped structure, the angle between the two mounting grooves forming the V-shaped structure is △, a permanent magnet is arranged in the mounting groove, the thickness of the permanent magnet is L4, and the width of the permanent magnet is L5, wherein 110°≤△≤140°, △=(18~20)*L4, L5≥2L4.

[0012] Preferably, a magnetic isolation bridge is formed between the mounting groove and the outer peripheral wall of the rotor core, and the circumferential length of the magnetic isolation bridge is L3, wherein L3≥L4.

[0013] Preferably, an avoidance groove is provided on at least one side wall of the mounting groove that cooperates with the permanent magnet, the avoidance groove corresponds to the corner position of the permanent magnet, the avoidance groove is an arc groove, and the radius R1 of the avoidance groove satisfies 0.2mm≤R1≤0.5mm.

[0014] Preferably, in a cross section perpendicular to the central axis of the rotor core, the mounting groove includes an adjacent first side edge and a second side edge, the first side edge forms an outer side edge of a V-shaped structure, the second side edge is located on a side of the mounting groove close to an outer peripheral wall of the rotor core, the first side edge and the second side edge are transitionally connected by a first arc and a second arc, and the center of the first arc and the center of the second arc are staggered.

[0015] Preferably, the distance between the center of the first arc and the center of the second arc is L2, wherein 0.2 mm≤L2≤0.4 mm.

[0016] Preferably, in a cross section perpendicular to the central axis of the rotor core, the mounting groove includes adjacent second side edges and third side edges, the second side edge is located on a side of the mounting groove close to the outer peripheral wall of the rotor core, the third side edge forms an inner side edge of a V-shaped structure, the second side edge and the third side edge are transitionally connected by a third circular arc, and the radius R4 of the third circular arc is R4 = (0.5-0.6)*L4.

[0017] Preferably, in a cross section perpendicular to the central axis of the rotor core, along the radial direction of the rotor core, a plurality of weight-reducing grooves are circumferentially arranged on the rotor core inside the mounting groove.

[0018] Preferably, along the radial direction of the rotor core, the minimum distance between the mounting groove and the central axis of the rotor core is R5, the maximum distance between the outer side of the weight-reducing groove and the central axis of the rotor core is R6, the minimum distance between the inner side of the weight-reducing groove and the central axis of the rotor core is R7, the distance between two adjacent weight-reducing grooves is L6, the radius of the central axis hole of the rotor core is R8, the maximum speed of the rotor core is ω, in ten thousand revolutions, the radius of the rotor core is R9,

[0019] R6=R5-(0.6~0.7)*ω2*R9,

[0020] R7=R8+(0.07~0.1)*ω2*R9,

[0021] L6=(0.8~0.11)*ω2*R9.

[0022] According to another aspect of the present application, a permanent magnet motor is provided, comprising a motor rotor, which is the motor rotor described above.

[0023] According to another aspect of the present application, an electric vehicle is provided, comprising a permanent magnet motor, which is the permanent magnet motor described above.

[0024] The motor rotor provided by the present application comprises a rotor core, a mounting groove is provided on the rotor core, the mounting groove forms a V-shaped structure, the angle between the two mounting grooves forming the V-shaped structure is △, a permanent magnet is provided in the mounting groove, the thickness of the permanent magnet is L4, the width of the permanent magnet is L5, wherein 110°≤△≤140°, △=(18~20)*L4, L5≥2L4. The above-mentioned motor rotor of the present application can be used to constrain the key dimensions of the rotor topological structure, which can greatly reduce the no-load back-EMF harmonics and torque pulsation of the motor, improve the motor output torque, improve the motor power density, improve the smoothness of the motor output torque, reduce motor vibration and noise, improve the comfort of the whole vehicle, and reduce harmonics. The reduction of harmonics can reduce rotor losses, improve motor efficiency, and avoid high-order harmonics interfering with other components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a partial structure of a motor rotor according to an embodiment of the present application;

[0026] Figure 2 for Figure 1 Schematic diagram of the enlarged structure at L;

[0027] Figure 3 This is a table of harmonic contents of the permanent magnet motor according to an embodiment of the present application;

[0028] Figure 4 This is a torque pulsation diagram of the permanent magnet motor according to an embodiment of the present application.

[0029] The reference numerals are as follows:

[0030] 1. Rotor core; 2. Mounting slot; 3. Permanent magnet; 4. Magnetic isolation bridge; 5. Avoidance slot; 6. First side; 7. Second side; 8. Third side; 9. First arc; 10. Second arc; 11. Third arc; 12. Weight reduction slot. DETAILED DESCRIPTION

[0031] See also Figure 1 to Figure 2 As shown, according to an embodiment of the present application, the motor rotor includes a rotor core 1, a mounting groove 2 is provided on the rotor core 1, the mounting groove 2 forms a V-shaped structure, the angle between the two mounting grooves 2 forming the V-shaped structure is △, a permanent magnet 3 is provided in the mounting groove 2, the thickness of the permanent magnet 3 is L4, the width of the permanent magnet 3 is L5, wherein 110°≤△≤140°, △=(18~20)*L4, L5≥2L4.

[0032] The motor rotor provided by the present application comprises a rotor core 1, a mounting groove 2 is provided on the rotor core 1, the mounting groove 2 forms a V-shaped structure, the angle between the two mounting grooves 2 forming the V-shaped structure is △, a permanent magnet 3 is provided in the mounting groove 2, the thickness of the permanent magnet 3 is L4, the width of the permanent magnet 3 is L5, wherein 110°≤△≤140°, △=(18~20)*L4, L5≥2L4. The above-mentioned motor rotor of the present application can be used to constrain the key dimensions of the rotor topological structure, greatly reduce the no-load back electromotive force harmonics and torque pulsation of the motor (both ≤3%), improve the motor output torque, improve the motor power density, improve the smoothness of the motor output torque, reduce the motor vibration and noise, improve the comfort of the whole vehicle, reduce the harmonics, reduce the rotor loss, improve the motor efficiency, and avoid high-order harmonics interfering with other components.

[0033] The motor rotor adopts the existing V-shaped topology structure, without adding redundant hollow structure. By increasing the rotor pole arc size, the motor torque output capacity can be improved, thereby improving the motor's overload capacity, efficiency and power density, and improving its speed regulation capability. The rotor topology structure that is easy to weaken magnetic field has a small weakening magnetic field angle under high-speed conditions, which reduces the motor current and significantly reduces motor losses, thereby improving the efficiency of the high-speed zone, improving the overall regional efficiency of the motor, and increasing the proportion of the motor's high-efficiency zone.

[0034] The length direction of the permanent magnet 3 is the axial direction of the rotor core 1, the width direction is the direction extending along the side of the V-shaped structure in a cross section perpendicular to the central axis of the rotor core 1, and the thickness direction is the direction perpendicular to the side of the V-shaped structure.

[0035] A magnetic isolation bridge 4 is formed between the mounting groove 2 and the outer peripheral wall of the rotor core 1 , and the circumferential length of the magnetic isolation bridge 4 is L3 , wherein L3 ≥ L4 .

[0036] Through research, it is found that the circumferential length L3 of the magnetic isolation bridge 4 is a factor that affects the harmonic content and torque pulsation. If space permits, L3 ≥ L4 can obtain better harmonic content and torque pulsation. The length of the magnetic isolation bridge 4 is increased, which can also reduce rotor leakage, improve the motor output capacity, and improve the rotor structural strength, ensuring that the motor can output a higher speed without damage. As a preferred embodiment, 1.2 ≤ L3 / L4 ≤ 1.4.

[0037] At least one side wall of the mounting groove 2 and the permanent magnet 3 is provided with an escape groove 5, the escape groove 5 corresponds to the corner position of the permanent magnet 3, the escape groove 5 is an arc groove, and the radius R1 of the escape groove 5 satisfies 0.2mm≤R1≤0.5mm. The arc groove with a radius of R1 is an escape groove for facilitating the placement of the permanent magnet. The escape groove 5 can improve the anti-demagnetization ability of the magnetic steel, avoid irreversible demagnetization of the motor under high current and high temperature conditions, and the escape groove 5 can reduce the chamfer of the permanent magnet, even if the permanent magnet 3 is not chamfered, it can be smoothly inserted into the mounting groove 2. In this embodiment, the width of the mounting groove 2 where the permanent magnet 3 is installed at the installation position of the permanent magnet 3 is greater than the width of other positions, and the wider structure at this place can be used to form a step with the structure at other positions, so as to form a limit for the installation of the permanent magnet 3 in the mounting groove 2, and prevent the displacement of the motor rotor during operation.

[0038] In a cross section perpendicular to the central axis of the rotor core 1, the mounting groove 2 includes an adjacent first side 6 and a second side 7, the first side 6 forming the outer side of the V-shaped structure, the second side 7 being located on a side of the mounting groove 2 close to the outer peripheral wall of the rotor core 1, the first side 6 and the second side 7 being transitionally connected by a first arc 9 and a second arc 10, and the center of the first arc 9 and the center of the second arc 10 are staggered.

[0039] The distance between the center of the first arc 9 and the center of the second arc 10 is L2, wherein 0.2 mm≤L2≤0.4 mm.

[0040] When the centers of the first arc 9 and the second arc 10 coincide, the magnetic isolation bridge structure here will be too short and cannot play an effective magnetic isolation role. By reasonably setting the distance between the centers of the first arc 9 and the second arc 10, the performance requirements of the motor can be met while achieving lower harmonics.

[0041] In a cross section perpendicular to the central axis of the rotor core 1, the mounting groove 2 includes adjacent second side edges 7 and third side edges 8, the second side edges 7 are located on a side of the mounting groove 2 close to the outer peripheral wall of the rotor core 1, the third side edges 8 form an inner side edge of a V-shaped structure, the second side edges 7 and the third side edges 8 are transitionally connected by a third circular arc 11, and the radius R4 of the third circular arc 11 is R4=(0.5-0.6)*L4.

[0042] Since the thickness of the permanent magnet 3 represented by L4 is closely related to the circumferential length of the magnetic isolation bridge 4 represented by L3, and the radius R4 of the third arc 11 will affect the circumferential length of the magnetic isolation bridge 4, associating the radius R4 of the third arc 11 with the thickness L4 of the permanent magnet 3 can make the radius of the third arc 11 have a suitable value and will not cause the relationship between the circumferential length of the magnetic isolation bridge 4 and the thickness of the permanent magnet 3 to exceed the optimal range.

[0043] In a cross section perpendicular to the central axis of the rotor core 1 , along the radial direction of the rotor core 1 , a plurality of weight-reducing grooves 12 are circumferentially arranged on the rotor core 1 inside the mounting groove 2 .

[0044] Along the radial direction of the rotor core 1, the minimum distance between the mounting groove 2 and the central axis of the rotor core 1 is R5, the maximum distance between the outer side of the weight reduction groove 12 and the central axis of the rotor core 1 is R6, the minimum distance between the inner side of the weight reduction groove 12 and the central axis of the rotor core 1 is R7, the distance between two adjacent weight reduction grooves 12 is L6, the radius of the central axis hole of the rotor core 1 is R8, the maximum speed of the rotor core 1 is ω, the unit is ten thousand revolutions, the radius of the rotor core 1 is R9,

[0045] R6=R5-(0.6~0.7)*ω2*R9,

[0046] R7=R8+(0.07~0.1)*ω2*R9,

[0047] L6=(0.8~0.11)*ω2*R9.

[0048] By defining the above relationship, the rotor magnetic circuit and rotor strength can be guaranteed, and at the same time, the best weight reduction effect can be achieved.

[0049] According to an embodiment of the present application, the permanent magnet motor includes a motor rotor, which is the motor rotor mentioned above.

[0050] See also Figure 3 and Figure 4 As shown, the permanent magnet motor of the embodiment of the present application has a maximum harmonic content of 2.14% and a torque pulsation of 1.57%. Therefore, the harmonic content and the torque pulsation are both below 3%, which can effectively reduce the motor exciting force, and the steady-state torsional vibration response of the motor excitation transmission system is significantly reduced, thereby reducing the torsional vibration of the electric vehicle power transmission system, reducing the overall noise and vibration, and greatly improving the safety and comfort of the entire vehicle.

[0051] After adopting the embodiments of the present application, the no-load back-EMF harmonics of the permanent magnet motor can be reduced to below 3%, thereby avoiding the reduction in the smoothness of the motor output torque, increased torque pulsation, and greater noise caused by large load harmonics; the reduction of harmonics can also reduce the temperature rise of the motor operation and avoid aging of the insulation layer of the motor components. The reduction of harmonics can also reduce the loss of the motor body and improve the motor efficiency; the generation of high-order harmonics during motor operation can be reduced, avoiding the generation of harmonic magnetic fields in the vehicle to cause electromagnetic interference to other surrounding communications, thereby improving the safety of the entire vehicle operation.

[0052] Harmonic reduction can reduce the loss of the air gap harmonic magnetic field on the rotor surface, avoid the temperature rise of the rotor, reduce the operating temperature of the permanent magnet, ensure higher magnetic properties of the permanent magnet, and enable the motor to achieve higher output performance and improve efficiency.

[0053] According to an embodiment of the present application, the electric vehicle includes a permanent magnet motor, which is the permanent magnet motor mentioned above.

[0054] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0055] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A motor rotor, characterized in that: The invention comprises a rotor core (1), wherein a mounting groove (2) is arranged on the rotor core (1), wherein the mounting groove (2) forms a V-shaped structure, wherein the angle between the two mounting grooves (2) forming the V-shaped structure is △, wherein a permanent magnet (3) is arranged in the mounting groove (2), wherein the thickness of the permanent magnet (3) is L4, and the width of the permanent magnet (3) is L5, wherein 110°≤△≤140°, △=(18-20)*L4, and L5≥2L4; In a cross section perpendicular to the central axis of the rotor core (1), along the radial direction of the rotor core (1), a plurality of weight-reducing grooves (12) are provided on the rotor core (1) inside the mounting groove (2) along the circumferential direction; Along the radial direction of the rotor core (1), the minimum distance between the mounting groove (2) and the central axis of the rotor core (1) is R5, the maximum distance between the outer side of the weight-reducing groove (12) and the central axis of the rotor core (1) is R6, the minimum distance between the inner side of the weight-reducing groove (12) and the central axis of the rotor core (1) is R7, the distance between two adjacent weight-reducing grooves (12) is L6, the radius of the central axis hole of the rotor core (1) is R8, the maximum rotation speed of the rotor core (1) is ω, in ten thousand revolutions, the radius of the rotor core (1) is R9, R6=R5-(0.6~0.7)*ω2*R9, R7=R8+(0.07~0.1)*ω2*R9, L6=(0.8~0.11)*ω2*R9.

2. The motor rotor according to claim 1, characterized in that: A magnetic isolation bridge (4) is formed between the installation groove (2) and the outer peripheral wall of the rotor core (1), and the circumferential length of the magnetic isolation bridge (4) is L3, wherein L3≥L4.

3. The motor rotor according to claim 1, characterized in that: An avoidance groove (5) is provided on at least one side wall of the mounting groove (2) that cooperates with the permanent magnet (3); the avoidance groove (5) corresponds to the corner position of the permanent magnet (3); the avoidance groove (5) is an arc-shaped groove; and the radius R1 of the avoidance groove (5) satisfies 0.2 mm ≤ R1 ≤ 0.5 mm.

4. The motor rotor according to claim 1, characterized in that: In a cross section perpendicular to the central axis of the rotor core (1), the mounting groove (2) comprises a first side edge (6) and a second side edge (7) adjacent to each other, the first side edge (6) forming an outer side edge of the V-shaped structure, the second side edge (7) being located on a side of the mounting groove (2) close to an outer peripheral wall of the rotor core (1), the first side edge (6) and the second side edge (7) being transitionally connected via a first circular arc (9) and a second circular arc (10), the center of the first circular arc (9) and the center of the second circular arc (10) being offset.

5. The motor rotor according to claim 4, characterized in that: The distance between the center of the first arc (9) and the center of the second arc (10) is L2, where 0.2 mm ≤ L2 ≤ 0.4 mm.

6. The motor rotor according to claim 1, characterized in that: In a cross section perpendicular to the central axis of the rotor core (1), the mounting groove (2) comprises a second side (7) and a third side (8) adjacent to each other, the second side (7) being located on a side of the mounting groove (2) close to the outer peripheral wall of the rotor core (1), the third side (8) forming an inner side of the V-shaped structure, the second side (7) and the third side (8) being transitionally connected via a third circular arc (11), the radius R4 of the third circular arc (11) being R4=(0.5-0.6)*L4.

7. A permanent magnet motor, comprising a motor rotor, characterized in that: The motor rotor is the motor rotor according to any one of claims 1 to 6.

8. An electric vehicle, comprising a permanent magnet motor, characterized in that: The permanent magnet motor is the permanent magnet motor according to claim 7.

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