Shifting type built-in double-layer permanent magnet rotor
By adopting a shift-type built-in double-layer permanent magnet rotor structure in the permanent magnet synchronous motor and utilizing different magnet designs, the problems of large torque fluctuation and high processing difficulty are solved, achieving high power density, low noise, low torque fluctuation and wide speed regulation of the motor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-06
- Publication Date
- 2026-04-14
AI Technical Summary
Existing permanent magnet synchronous motors suffer from problems such as large torque fluctuations, low power density, narrow high-speed constant power range, low overload capacity, and poor reliability, making them particularly difficult to meet the requirements in electric vehicles.
The rotor adopts a displacement-type built-in double-layer permanent magnet rotor structure. By setting multiple permanent magnet units on the rotor core, and utilizing the different coercivity, remanence density and thickness distribution of the first and second magnets, a local radial displacement design of the magnets is formed to reduce torque fluctuation.
It effectively reduces torque ripple, improves the overall performance of the motor, reduces mechanical vibration and noise, improves the air gap magnetic field waveform, reduces core loss, increases overload capacity and the high power density of the motor, and meets the driving requirements of electric vehicles.
Smart Images
Figure CN224123961U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to motor technology, and in particular to a technology for a displacement-type built-in double-layer permanent magnet rotor. Background Technology
[0002] Currently, permanent magnet synchronous motors suitable for electric vehicles suffer from drawbacks such as large torque fluctuations, low power density, narrow high-speed constant power range, low overload capacity, and poor reliability, making it difficult to meet the requirements.
[0003] Reducing motor torque ripple is a key focus of motor research. The interaction between the stator core and permanent magnets generates positioning torque, and the non-sinusoidal waveforms of current and back EMF cause harmonic torque during motor operation. Furthermore, deviations in manufacturing processes exacerbate torque ripple. Cogging torque, also known as magnetic reluctance torque, is a fatal flaw in speed control systems used in automation and mechatronics applications. When the frequency of the torque coincides with the mechanical resonant frequency of the stator or rotor during motor operation, the vibration and noise generated by the cogging torque are significantly amplified, also affecting low-speed performance and positioning accuracy.
[0004] To overcome the above-mentioned defects, most existing permanent magnet synchronous motors adopt measures such as setting skewed slots in the stator, setting skewed poles in the rotor, setting uneven air gaps between the stator and rotor, and increasing the number of motor slots to reduce torque fluctuations. These measures increase the difficulty of rotor processing and increase rotor processing costs. Utility Model Content
[0005] In view of the defects existing in the prior art, the technical problem to be solved by this utility model is to provide a displacement-type built-in double-layer permanent magnet rotor that can reduce motor torque fluctuation and has low processing difficulty.
[0006] To solve the above-mentioned technical problems, this utility model provides a shift-type built-in double-layer permanent magnet rotor, including a rotor core, on which multiple permanent magnet units are provided, each permanent magnet unit being symmetrically arranged around the axis of the rotor core; each permanent magnet unit is composed of a first magnet and a second magnet, the second magnet and the first magnet being arranged at intervals from the inside to the outside along the radial direction of the rotor core, characterized in that:
[0007] The second magnet is composed of three magnet segments arranged at intervals from left to right. The distance between the middle magnet segment and the rotor core axis is greater than the distance between the other two magnet segments and the rotor core axis.
[0008] Furthermore, the coercivity of the first magnet is greater than the coercivity of each magnet segment in the second magnet.
[0009] Furthermore, the remanent magnetization of the first magnet is greater than that of the second magnet.
[0010] Furthermore, each segment of the first magnet and the second magnet is a straight-line magnet, and the thickness of each segment of the second magnet is greater than the thickness of the first magnet.
[0011] Furthermore, each segment of the second magnet is an arc-shaped magnet, and the thickness of the left and right magnet segments in the second magnet decreases from the inside to the outside along the radial direction of the rotor core.
[0012] Furthermore, the outer ends of the left and right magnet segments in the second magnet are 0.8 to 0.86 times the thickness of the middle magnet segment.
[0013] Furthermore, an outer magnetic shielding groove is formed at each end of the first magnet, and an inner magnetic shielding groove is formed at each end of the second magnet.
[0014] The shift-type built-in double-layer permanent magnet rotor provided by this utility model adopts a structure of local magnetic steel radial shift, which can effectively improve the overall performance. The motor stator does not need skewed slots, the rotor does not need skewed poles, and there is no need to set uneven air gaps between the stator and rotor. This can effectively reduce torque fluctuations, improve the air gap magnetic field waveform of the motor, and reduce the manufacturing difficulty. Without increasing the number of motor slots, it can increase the fundamental frequency of cogging torque fluctuations, reduce the amplitude of cogging fundamental and higher harmonic torques, reduce torque fluctuations caused by cogging, and make the radial force of the d-axis of the magnetic pole radial centerline and the q-axis of the inter-pole centerline tend to be balanced, improve the air gap magnetic flux density waveform, reduce mechanical vibration, noise and back EMF harmonics, reduce core losses, and effectively reduce torque fluctuations. Attached Figure Description
[0015] Figure 1 This is a radial cross-sectional schematic diagram of the shift-type built-in double-layer permanent magnet rotor of the first embodiment of this utility model;
[0016] Figure 2 This is a radial cross-sectional schematic diagram of the shift-type built-in double-layer permanent magnet rotor of the second embodiment of this utility model;
[0017] Figure 3 These are torque fluctuation histograms of the shift-type built-in double-layer permanent magnet rotor of the first and second embodiments of this utility model and the existing built-in V-type permanent magnet rotor. Detailed Implementation
[0018] The embodiments of this utility model are described in further detail below with reference to the accompanying drawings. However, these embodiments are not intended to limit this utility model. Any similar structures or variations thereof that adopt this utility model should be included in the protection scope of this utility model. The commas in this utility model all indicate the relationship between and.
[0019] like Figure 1As shown, the first embodiment of this utility model provides a displacement-type built-in double-layer permanent magnet rotor, including a rotor core 1, on which a plurality of permanent magnet units are provided, and each permanent magnet unit is symmetrically arranged around the axis of the rotor core.
[0020] The permanent magnet unit consists of a first magnet 11 and a second magnet. The second magnet and the first magnet 11 are arranged radially from the inside to the outside along the rotor core. The second magnet consists of three magnet segments 12, 13, and 14 arranged radially from left to right. The distance between the middle magnet segment 13 and the rotor core axis is greater than the distance between the other two magnet segments 12 and 14 and the rotor core axis, so that the middle magnet segment 13 is moved radially outward relative to the other two magnet segments 12 and 14 along the rotor core, forming a structure in which the magnet is partially radially outward.
[0021] Each segment of the first magnet 11 and the second magnet is a straight-line magnet. The thickness of each segment of the second magnet is greater than the thickness of the first magnet 11. The coercivity of the first magnet 11 is greater than the coercivity of each segment of the second magnet. The remanence density of the first magnet 11 is greater than that of the second magnet.
[0022] In the first embodiment of this utility model, an outer magnetic isolation groove 15 is formed at each end of the first magnet 11, and an inner magnetic isolation groove 16 is formed at each end of the second magnet.
[0023] like Figure 2 As shown, the second embodiment of this utility model is similar to the first embodiment. The rotor core 2 of the second embodiment is also provided with multiple permanent magnet units, and each permanent magnet unit is symmetrically arranged around the axis of the rotor core. The permanent magnet unit is also composed of a first magnet 21 and a second magnet. The second magnet is also composed of three magnet segments 22, 23, and 24 arranged from left to right. The distance between the middle magnet segment 23 and the axis of the rotor core is greater than the distance between the other two magnet segments 22 and 24 and the axis of the rotor core. Each end of the first magnet 21 has an outer magnetic isolation groove 25, and each end of the second magnet has an inner magnetic isolation groove 26.
[0024] The difference between the second embodiment of this utility model and the first embodiment is that each magnet segment 22, 23, and 24 in the second magnet in the second embodiment is an arc-shaped magnet. The thickness of the left magnet segment 22 and the right magnet segment 24 in the second magnet decreases from the inside to the outside along the radial direction of the rotor core. The outer end thickness of the left magnet segment 22 and the right magnet segment 24 in the second magnet is 0.8 to 0.86 times the thickness of the middle magnet segment 23.
[0025] Figure 3 This is a torque fluctuation histogram of the embodiment of this utility model and an existing built-in V-type permanent magnet rotor. Figure 3 In the figure, the vertical axis Tr represents torque fluctuation, the square column A represents the torque fluctuation of the existing built-in V-type permanent magnet rotor, the square column D represents the torque fluctuation of the first embodiment, and the square column F represents the torque fluctuation of the second embodiment.
[0026] Torque fluctuations caused by electromagnetic factors generate mechanical and electromagnetic noise, affecting the smooth operation and reliability of the motor. These fluctuations are of two types: cogging torque, which is the torque generated by the interaction between the stator slots and the rotor permanent magnets. This torque fluctuates periodically with spatial position and is independent of the stator current; and ripple torque, which is the harmonic torque caused by the difference between the current and back EMF waveforms. The torque fluctuations in automotive permanent magnet synchronous motors are the superposition of cogging torque and ripple torque.
[0027] from Figure 3 It can be seen that the torque fluctuation of the existing built-in V-type permanent magnet rotor is 73%, the torque fluctuation of the first embodiment is 49.5%, and the torque fluctuation of the second embodiment is 47%. The torque fluctuation has decreased significantly, indicating that the rotor of this embodiment can effectively reduce cogging torque fluctuation and ripple torque fluctuation.
[0028] The motor using the permanent magnet rotor of this embodiment was compared with a motor of the same specification using an existing built-in V-type permanent magnet rotor. The motor parameters are: rated power of 18KW, rated speed of 3000r / min, maximum speed of 9000r / min, rated torque of 57.3Nm, and maximum torque of 126Nm.
[0029] The cogging torque of the motor using the existing built-in V-type permanent magnet rotor is 2.63 Nm, the cogging torque fluctuation is 4.58%, and the efficiency is 94%.
[0030] The motor using the permanent magnet rotor of the first embodiment has a cogging torque of 1.23 Nm, a cogging torque ripple of 2.15%, and an efficiency of 96.5%.
[0031] The motor using the permanent magnet rotor of the second embodiment has a cogging torque of 1.23 Nm, a cogging torque ripple of 2.15%, and an efficiency of 96.5%.
[0032] It can be seen that using the same specifications of motors in the first and second embodiments significantly reduces cogging torque fluctuation and significantly improves efficiency.
[0033] This utility model embodiment features a structure with localized radial displacement of the magnets, effectively improving overall performance. The motor stator does not require skewed slots, the rotor does not require skewed poles, and there is no need for measures such as uneven air gaps between the stator and rotor. This effectively reduces torque ripple, improves the air gap magnetic field waveform, and increases the fundamental frequency of cogging torque ripple without increasing the number of motor slots. It also reduces the amplitude of the fundamental and higher harmonic torques, lowers torque ripple caused by cogging, and brings the radial forces along the d-axis of the magnetic pole radial centerline and the q-axis of the inter-pole centerline into balance. This improves the air gap magnetic flux density waveform, reduces mechanical vibration, noise, and back EMF harmonics, reduces core losses, effectively reduces torque ripple, improves overload capacity, meets the drive requirements of electric vehicles, and achieves high power density, low noise, low torque ripple, wide speed range, small size, lightweight design, and smooth operation.
Claims
1. A shift type built-in double-layer permanent magnet rotor, comprising a rotor core, a plurality of permanent magnet units are arranged on the rotor core, each permanent magnet unit is arranged symmetrically around the axis of the rotor core; the permanent magnet unit is composed of a first magnetic steel and a second magnetic steel, the second magnetic steel and the first magnetic steel are arranged in the radial direction of the rotor core from inside to outside at intervals, characterized in that: the second magnetic steel is composed of three magnetic steel segments arranged at intervals from left to right, the distance between the middle magnetic steel segment and the axis of the rotor core is greater than the distance between the other two magnetic steel segments and the axis of the rotor core. The coercive force of the first magnetic steel is greater than the coercive force of each magnetic steel segment in the second magnetic steel.
2. The shift built-in double-layer permanent magnet rotor according to claim 1, characterized by: The residual magnetism density of the first magnetic steel is greater than the residual magnetism density of the second magnetic steel.
3. The shift built-in double-layer permanent magnet rotor according to claim 1, characterized by: Each magnetic steel segment in the first magnetic steel and the second magnetic steel is a bar type magnetic steel, and the thickness of each magnetic steel segment in the second magnetic steel is greater than the thickness of the first magnetic steel.
4. The shift built-in double-layer permanent magnet rotor according to claim 1, characterized by: Each magnetic steel segment in the second magnetic steel is an arc type magnetic steel, and the thickness of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel decreases from inside to outside in the radial direction of the rotor core.
5. The shift built-in double-layer permanent magnet rotor according to claim 1, characterized by: The outer end thickness of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel is 0.8-0.86 times the thickness of the middle magnetic steel segment.
6. The shift built-in double-layer permanent magnet rotor according to claim 5, characterized by: Each end of the first magnetic steel forms an outer layer magnetic separation groove, and each end of the second magnetic steel forms an inner layer magnetic separation groove.
7. The shift built-in double-layer permanent magnet rotor according to claim 1, characterized by: