Shifting type built-in double-layer permanent magnet rotor

Abstract

A displacement type built-in double-layer permanent magnet rotor relates to the technical field of motors and comprises a rotor core, a plurality of permanent magnet units are arranged on the rotor core, and the permanent magnet units are symmetrically arranged around the axis of the rotor core; the permanent magnet unit is composed of first magnetic steel and second magnetic steel, the second magnetic steel and the first magnetic steel are arranged at intervals from inside to outside in the radial direction of the rotor core, the second magnetic steel is composed of three magnetic steel segments arranged at intervals from left to right, and the distance between the middle magnetic steel segment and the axis of the rotor core is smaller than the distance between the middle magnetic steel segment and the axis of the rotor core. And the distance between the other two magnetic steel segments and the axis of the rotor iron core is larger than that between the two magnetic steel segments. The rotor provided by the invention can effectively reduce the torque ripple.

Description

Technical Field

[0001] The invention relates to motor technology, in particular to a technology of a shifted built-in double-layer permanent magnet rotor. Background Art

[0002] The permanent magnet synchronous motors currently suitable for electric vehicles have defects such as large torque fluctuation, low power density, narrow high-speed constant power range, low overload capacity and poor reliability, which make it difficult to meet the requirements.

[0003] Reducing motor torque fluctuation is one of the key points of motor research. The interaction between the stator core and the permanent magnet generates a positioning torque. The current and back EMF are non-sinusoidal waveforms, which cause harmonic torque to be generated during motor operation. In addition, deviations in the processing technology will aggravate torque fluctuations. Cogging torque, also known as magnetic resistance torque, is a fatal defect in the speed control system of automation and mechatronics. When the motor is running and the frequency of the torque is consistent with the mechanical resonance frequency of the stator or rotor, the vibration and noise generated by the cogging torque are significantly amplified, and it also affects the low-speed performance and positioning accuracy.

[0004] In order to overcome the above defects, most of the existing permanent magnet synchronous motors adopt measures such as setting oblique slots in the stator, setting oblique 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 the rotor processing cost. Summary of the invention

[0005] In view of the defects existing in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a shifted internal double-layer permanent magnet rotor which can reduce the torque fluctuation of the motor and has low processing difficulty.

[0006] In order to solve the above technical problems, the present invention provides a shifted internal double-layer permanent magnet rotor, comprising a rotor core, on which a plurality of permanent magnet units are arranged symmetrically around the axis of the rotor core; the permanent magnet units are composed of a first magnetic steel and a second magnetic steel, and the second magnetic steel and the first magnetic steel are arranged from inside to outside along the radial direction of the rotor core, characterized in that:

[0007] The second magnetic steel consists of three magnetic steel segments arranged at intervals from left to right, wherein 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.

[0008] Furthermore, the coercive force of the first magnetic steel is greater than the coercive force of each magnetic steel segment in the second magnetic steel.

[0009] Furthermore, the residual magnetic density of the first magnetic steel is greater than the residual magnetic density of the second magnetic steel.

[0010] Furthermore, each magnetic steel segment in the first magnetic steel and the second magnetic steel is a straight-line 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.

[0011] Furthermore, each magnetic steel segment in the second magnetic steel is an arc-shaped magnetic steel, and the thickness of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel decreases from the inside to the outside along the radial direction of the rotor core.

[0012] Furthermore, the thickness of the outer ends of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel is 0.8 to 0.86 times the thickness of the middle magnetic steel segment.

[0013] Furthermore, an outer magnetic isolation groove is formed at each of the two ends of the first magnetic steel, and an inner magnetic isolation groove is formed at each of the two ends of the second magnetic steel.

[0014] The shifted built-in double-layer permanent magnet rotor provided by the present invention adopts a structure of partial radial displacement of magnetic steel, which can effectively improve the comprehensive performance. The motor stator does not need skewed slots, the rotor does not need skewed poles, and there is no need to set an uneven air gap between the stator and the rotor. Measures such as these can effectively reduce torque fluctuations and improve the air gap magnetic field waveform of the motor. The processing difficulty is also relatively low. Without increasing the number of motor slots, the fundamental frequency of the tooth slot torque fluctuation can be increased, the amplitude of the tooth slot fundamental wave and high-order harmonic torque can be reduced, the torque fluctuation caused by the tooth slot can be reduced, the d-axis radial center line of the magnetic pole and the q-axis radial force of the inter-pole center line can be balanced, the air gap magnetic flux density waveform can be improved, mechanical vibration, noise and back-electromotive force harmonics can be reduced, core loss can be reduced, and torque fluctuations can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a radial cross-sectional schematic diagram of a displaced internal double-layer permanent magnet rotor according to a first embodiment of the present invention;

[0016] Figure 2 is a radial cross-sectional schematic diagram of a displaced internal double-layer permanent magnet rotor according to a second embodiment of the present invention;

[0017] Figure 3 It is a torque fluctuation histogram of the shifted internal double-layer permanent magnet rotor according to the first and second embodiments of the present invention and the existing internal V-type permanent magnet rotor. DETAILED DESCRIPTION

[0018] The following is a further detailed description of an embodiment of the present invention in conjunction with the accompanying drawings, but this embodiment is not intended to limit the present invention. All similar structures and similar variations of the present invention should be included in the protection scope of the present invention. The commas in the present invention all represent the relationship of and.

[0019] like Figure 1As shown, a displaced internal double-layer permanent magnet rotor provided in the first embodiment of the present invention comprises a rotor core 1, on which a plurality of permanent magnet units are arranged symmetrically around the axis of the rotor core;

[0020] The permanent magnet unit is composed of a first magnetic steel 11 and a second magnetic steel. The second magnetic steel and the first magnetic steel 11 are arranged from inside to outside along the radial direction of the rotor core. The second magnetic steel is composed of three magnetic steel segments 12, 13, and 14 arranged from left to right. The spacing between the middle magnetic steel segment 13 and the axis of the rotor core is greater than the spacing between the other two magnetic steel segments 12 and 14 and the axis of the rotor core, so that the middle magnetic steel segment 13 moves outward along the radial direction of the rotor core relative to the other two magnetic steel segments 12 and 14, forming a structure in which the local magnetic steel moves outward in the radial direction.

[0021] Each magnetic steel segment in the first magnetic steel 11 and the second magnetic steel is a straight-line magnetic steel, the thickness of each magnetic steel segment in the second magnetic steel is greater than the thickness of the first magnetic steel 11, the coercive force of the first magnetic steel 11 is greater than the coercive force of each magnetic steel segment in the second magnetic steel, and the residual magnetic density of the first magnetic steel 11 is greater than the residual magnetic density of the second magnetic steel.

[0022] In the first embodiment of the present invention, an outer magnetic isolation groove 15 is formed at both ends of the first magnetic steel 11 , and an inner magnetic isolation groove 16 is formed at both ends of the second magnetic steel.

[0023] like Figure 2 As shown, the second embodiment of the present invention is similar to the first embodiment. The rotor core 2 of the second embodiment is also provided with a plurality of permanent magnet units, and each permanent magnet unit is symmetrically arranged around the axis of the rotor core, and the permanent magnet unit is also composed of a first magnetic steel 21 and a second magnetic steel, and the second magnetic steel is also composed of three magnetic steel segments 22, 23, and 24 arranged from left to right, wherein the spacing between the middle magnetic steel segment 23 and the axis of the rotor core is greater than the spacing between the other two magnetic steel segments 22 and 24 and the axis of the rotor core; an outer magnetic isolation groove 25 is formed at each end of the first magnetic steel 21, and an inner magnetic isolation groove 26 is formed at each end of the second magnetic steel;

[0024] The difference between the second embodiment of the present invention and the first embodiment is that each magnetic steel segment 22, 23, 24 in the second magnetic steel in the second embodiment is an arc-shaped magnetic steel, and the thickness of the left magnetic steel segment 22 and the right magnetic steel segment 24 in the second magnetic steel decreases from the inside to the outside along the radial direction of the rotor core, and the outer end thickness of the left magnetic steel segment 22 and the right magnetic steel segment 24 in the second magnetic steel is 0.8 to 0.86 times the thickness of the middle magnetic steel segment 23.

[0025] Figure 3 is a torque fluctuation histogram of the embodiment of the present invention and the existing built-in V-type permanent magnet rotor, Figure 3The vertical axis Tr in is the torque fluctuation, the square column A is the torque fluctuation of the existing internal V-type permanent magnet rotor, the square column D is the torque fluctuation of the first embodiment, and the square column F is the torque fluctuation of the second embodiment.

[0026] Torque fluctuation caused by electromagnetic reasons will generate mechanical and electromagnetic noise, affecting the smooth operation and reliability of the motor. It is divided into two types: one is cogging torque, which is the torque generated by the interaction between the stator teeth and the rotor permanent magnets. This torque fluctuates due to periodic changes in spatial position and has nothing to do with the stator current; the other is ripple torque, which is the harmonic torque caused by the difference in current and back-EMF waveforms. The torque fluctuation of automotive permanent magnet synchronous motors is 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 is significantly reduced, which shows that the rotor of this embodiment can effectively reduce the cogging torque fluctuation and the ripple torque fluctuation.

[0028] The motor using the permanent magnet rotor of this embodiment is compared with a motor of the same specification using an existing built-in V-type permanent magnet rotor. The parameters of the motor 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 motor using the existing internal V-type permanent magnet rotor has a cogging torque of 2.63Nm, a cogging torque ripple of 4.58%, and an efficiency of 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 the cogging torque ripple is significantly reduced and the efficiency is significantly improved by using the motors of the same specifications of the first embodiment and the second embodiment.

[0033] The embodiment of the present invention constitutes a structure of partial radial displacement of magnetic steel, which can effectively improve the comprehensive performance. The motor stator does not need skewed slots, the rotor does not need skewed poles, and there is no need to set an uneven air gap between the stator and the rotor. Measures such as these can effectively reduce torque fluctuations and improve the air gap magnetic field waveform of the motor. Without increasing the number of motor slots, the fundamental frequency (frequency) of the tooth slot torque fluctuation can be increased, the amplitude of the tooth slot fundamental wave and high-order harmonic torque can be reduced, the torque fluctuation caused by the tooth slot can be reduced, and the d-axis radial force of the magnetic pole radial center line and the q-axis radial force of the inter-pole center line can be balanced, the air gap magnetic flux density waveform can be improved, mechanical vibration, noise and back electromotive force harmonics can be reduced, core loss can be reduced, torque fluctuations can be effectively reduced, overload capacity can be improved, and the driving requirements of electric vehicles can be met, and the motor can achieve high power density, low noise, low torque fluctuation, wide speed regulation, small size, light weight and stable operation.

Claims

1. A shifted internal double-layer permanent magnet rotor, comprising a rotor core, on which a plurality of permanent magnet units are arranged symmetrically around the axis of the rotor core; the permanent magnet units are composed of a first magnetic steel and a second magnetic steel, and the second magnetic steel and the first magnetic steel are arranged from inside to outside along the radial direction of the rotor core. Features: The second magnetic steel consists of three magnetic steel segments arranged at intervals from left to right, wherein 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.

2. The shifted internal double-layer permanent magnet rotor according to claim 1, Features: The coercive force of the first magnetic steel is greater than the coercive force of each magnetic steel segment in the second magnetic steel.

3. The shifted internal double-layer permanent magnet rotor according to claim 1, Features: The residual magnetic density of the first magnetic steel is greater than the residual magnetic density of the second magnetic steel.

4. The shifted internal double-layer permanent magnet rotor according to claim 1, Features: Each magnetic steel segment in the first magnetic steel and the second magnetic steel is a straight-line 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.

5. The shifted internal double-layer permanent magnet rotor according to claim 1, Features: Each magnetic steel segment in the second magnetic steel is an arc-shaped magnetic steel, and the thickness of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel decreases from the inside to the outside along the radial direction of the rotor core.

6. The shifted internal double-layer permanent magnet rotor according to claim 5, Features: The thickness of the outer ends of the left magnetic steel segment and the right magnetic steel segment in the second magnetic steel is 0.8 to 0.86 times the thickness of the middle magnetic steel segment.

7. The shifted internal double-layer permanent magnet rotor according to claim 1, Features: An outer magnetic isolation groove is formed at each of the two ends of the first magnetic steel, and an inner magnetic isolation groove is formed at each of the two ends of the second magnetic steel.

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