Built-in alternating arrangement type permanent magnet rotor

Abstract

A built-in alternating arrangement type 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 units are divided into a group A and a group B, the two groups of permanent magnet units are alternately arranged around the axis of the rotor core, a first magnetic steel group is arranged on the group A of permanent magnet units, and a second magnetic steel group is arranged on the group B of permanent magnet units; the number of the magnetic steels in the first magnetic steel group is different from the number of the magnetic steels in the second magnetic steel group, and the arrangement shape of the magnetic steels in the first magnetic steel group is different from the arrangement shape of the magnetic steels in the second magnetic steel group. 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 built-in alternately arranged 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 built-in alternating arrangement type 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 built-in alternating 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; characterized in that:

[0007] The permanent magnet units are divided into group A and group B. The two groups of permanent magnet units are alternately arranged around the axis of the rotor core. The permanent magnet units of group A are arranged with a first magnetic steel group, and the permanent magnet units of group B are arranged with a second magnetic steel group. The number of magnetic steels in the first magnetic steel group is different from the number of magnetic steels in the second magnetic steel group, and the arrangement shape of the magnetic steels in the first magnetic steel group is different from the arrangement shape of the magnetic steels in the second magnetic steel group.

[0008] Furthermore, the first magnetic steel group consists of two magnetic steels, which are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with a narrow mouth facing inward; the second magnetic steel group consists of three magnetic steels, two of which are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with a narrow mouth facing inward, and the other magnetic steel is arranged in the narrow mouth of the eight-shaped shape.

[0009] Furthermore, the first magnetic steel group consists of two magnetic steels, which are arranged on both sides of the d-axis and are arranged in an eight-shaped shape with a narrow mouth facing inward; the second magnetic steel group consists of an arc-shaped magnetic steel with both ends facing outward.

[0010] Furthermore, the first magnetic steel group consists of two inner magnetic steels and two outer magnetic steels, the two inner magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with a narrow mouth facing inward, and the two outer magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with a narrow mouth facing inward; the second magnetic steel group consists of two magnetic steels, the two magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with a narrow mouth facing inward.

[0011] Furthermore, both ends of each inner magnetic steel and each outer magnetic steel are provided with end magnetic isolation grooves, and a bottom magnetic isolation groove is provided between the inner ends of the two inner magnetic steels.

[0012] Furthermore, an end magnetic isolation groove is formed at each end of the two magnetic steels in the second magnetic steel group, and a circular auxiliary groove is provided between the two magnetic steels.

[0013] The built-in alternating arrangement type permanent magnet rotor provided by the present invention adopts an alternating arrangement structure of adjacent permanent magnet unit magnets to form asymmetric eccentric magnetic poles, 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 tooth slot fundamental wave and high-order harmonic torque amplitudes can be reduced, and the torque fluctuation caused by the tooth slot can be reduced, so that the d-axis radial center line of the magnetic pole and the q-axis radial force of the inter-pole center line tend to be balanced, the air gap magnetic flux density waveform is improved, mechanical vibration, noise and back-electromotive force harmonics are reduced, core loss is reduced, and torque fluctuations are effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a radial cross-sectional schematic diagram of a built-in alternating arrangement type permanent magnet rotor according to a first embodiment of the present invention;

[0015] Figure 2 is a radial cross-sectional schematic diagram of a built-in alternating arrangement type permanent magnet rotor according to a second embodiment of the present invention;

[0016] Figure 3 is a radial cross-sectional schematic diagram of a built-in alternating arrangement type permanent magnet rotor according to a third embodiment of the present invention;

[0017] Figure 4 1 is a histogram of torque fluctuations of the interior alternating permanent magnet rotors according to the first embodiment, the second embodiment and the third embodiment of the present invention and the existing interior V-shaped 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 1 As shown, a first embodiment of the present invention provides a built-in alternating permanent magnet rotor, comprising a rotor core 1, wherein the rotor core 1 is provided with a plurality of permanent magnet units, and each permanent magnet unit is symmetrically arranged around the axis of the rotor core;

[0020] The permanent magnet units are divided into group A and group B. The two groups of permanent magnet units are alternately arranged around the axis of the rotor core. The permanent magnet units of group A are provided with a first magnetic steel group, and the permanent magnet units of group B are provided with a second magnetic steel group.

[0021] In the first embodiment of the present invention, the first magnetic steel group is composed of two magnetic steels 111, which are arranged on both sides of the d-axis and in an eight-shaped arrangement with a narrow opening facing inwards. An inner magnetic isolation groove 112 is formed between the inner ends of the two magnetic steels, and an outer magnetic isolation groove 113 is formed at the outer ends of the two magnetic steels.

[0022] The second magnetic steel group is composed of three magnetic steels 121, two of which are arranged on both sides of the d-axis and are arranged in an eight-shaped shape with the narrow mouth facing inward, and the other magnetic steel is arranged in the narrow mouth of the eight-shaped shape. An outer magnetic isolation groove 123 is formed at the outer end of the two eight-shaped magnetic steels, and an inner magnetic isolation groove 122 is provided between each 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 units are also divided into group A and group B. The two groups of permanent magnet units are alternately arranged around the axis of the rotor core, the permanent magnet units of group A are provided with a first magnetic steel group, and the permanent magnet units of group B are provided with a second magnetic steel group;

[0024] The difference between the second embodiment of the present invention and the first embodiment is that the second magnetic steel group of the second embodiment is composed of an arc-shaped magnetic steel 211 with two ends facing outwards.

[0025] like Figure 3As shown, the third embodiment of the present invention is similar to the first embodiment. The rotor core 3 of the third 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 units are also divided into group A and group B. The two groups of permanent magnet units are alternately arranged around the axis of the rotor core, the permanent magnet units of group A are provided with a first magnetic steel group, and the permanent magnet units of group B are provided with a second magnetic steel group;

[0026] The difference between the third embodiment of the present invention and the first embodiment is that the first magnetic steel group of the third embodiment is composed of two inner magnetic steels 311 and two outer magnetic steels 312, the two inner magnetic steels 311 are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with a narrow mouth facing inward, the two outer magnetic steels 312 are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with a narrow mouth facing inward, both ends of each inner magnetic steel 311 and each outer magnetic steel 312 are provided with an end magnetic isolation groove 313, and a bottom magnetic isolation groove 314 is provided between the inner ends of the two inner magnetic steels 311;

[0027] The second magnetic steel group is composed of two magnetic steels 321, which are arranged on both sides of the d-axis and in an eight-shaped shape with a narrow mouth facing inward. An end magnetic isolation groove 322 is formed at each end of the two magnetic steels 321, and a circular auxiliary groove 324 is provided between the two magnetic steels 321.

[0028] Figure 4 is a torque fluctuation histogram of the embodiment of the present invention and the existing built-in V-type permanent magnet rotor, Figure 4 The vertical axis Tr in the figure is the torque fluctuation, the square column A is the torque fluctuation of the existing built-in V-type permanent magnet rotor, the square column H is the torque fluctuation of the first embodiment, the square column I is the torque fluctuation of the second embodiment, and the square column J is the torque fluctuation of the third embodiment.

[0029] 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.

[0030] from Figure 4 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 47.5%, the torque fluctuation of the second embodiment is 47.5%, and the torque fluctuation of the third 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.

[0031] 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;

[0032] 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%;

[0033] The motor using the permanent magnet rotor of the first embodiment has a cogging torque of 1.63 Nm, a cogging torque ripple of 2.85%, and an efficiency of 95.8%;

[0034] The motor using the permanent magnet rotor of the second embodiment has a cogging torque of 1.26 Nm, a cogging torque ripple of 2.2%, and an efficiency of 96.2%.

[0035] The motor using the permanent magnet rotor of the second embodiment has a cogging torque of 1.22 Nm, a cogging torque ripple of 2.13%, and an efficiency of 96.3%;

[0036] It can be seen that the cogging torque fluctuation of the motors of the same specifications according to the first embodiment, the second embodiment and the third embodiment is significantly reduced and the efficiency is significantly improved.

[0037] The embodiment of the present invention adopts an alternating arrangement structure of adjacent permanent magnet unit magnets to form an asymmetric eccentric magnetic pole, 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 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, and the torque fluctuation caused by the tooth slot can be reduced, so that the d-axis radial force of the magnetic pole radial center line and the q-axis radial force of the inter-pole center line tend to balance, improve the air gap magnetic flux density waveform, reduce mechanical vibration, noise and back electromotive force harmonics, reduce core loss, effectively reduce torque fluctuations, improve overload capacity, meet the driving requirements of electric vehicles, and achieve the characteristics of high power density, low noise, low torque fluctuation, wide speed regulation, small size, light weight and stable operation of the motor.

Claims

1. A built-in alternating 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; Features: The permanent magnet units are divided into group A and group B. The two groups of permanent magnet units are alternately arranged around the axis of the rotor core. The permanent magnet units of group A are arranged with a first magnetic steel group, and the permanent magnet units of group B are arranged with a second magnetic steel group. The number of magnetic steels in the first magnetic steel group is different from the number of magnetic steels in the second magnetic steel group, and the arrangement shape of the magnetic steels in the first magnetic steel group is different from the arrangement shape of the magnetic steels in the second magnetic steel group.

2. The internal alternating permanent magnet rotor according to claim 1, Features: The first magnetic steel group consists of two magnetic steels, which are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with the narrow mouth facing inward; the second magnetic steel group consists of three magnetic steels, two of which are respectively arranged on both sides of the d-axis and are arranged in an eight-shaped shape with the narrow mouth facing inward, and the other magnetic steel is arranged in the narrow mouth of the eight-shaped shape.

3. The internal alternating permanent magnet rotor according to claim 1, Features: The first magnetic steel group consists of two magnetic steels, which are arranged on both sides of the d-axis and in an eight-shaped arrangement with the narrow mouth facing inward; the second magnetic steel group consists of an arc-shaped magnetic steel with both ends facing outward.

4. The internal alternating permanent magnet rotor according to claim 1, Features: The first magnetic steel group consists of two inner magnetic steels and two outer magnetic steels, the two inner magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with the narrow mouth facing inward, and the two outer magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with the narrow mouth facing inward; the second magnetic steel group consists of two magnetic steels, the two magnetic steels are respectively arranged on both sides of the d-axis and are arranged in a figure-eight shape with the narrow mouth facing inward.

5. The internal alternating permanent magnet rotor according to claim 4, Features: Both ends of each inner magnetic steel and each outer magnetic steel are provided with end magnetic isolation grooves, and a bottom magnetic isolation groove is provided between the inner ends of the two inner magnetic steels.

6. The internal alternating permanent magnet rotor according to claim 4, Features: An end magnetic isolation groove is formed at each end of the two magnetic steels in the second magnetic steel group, and a circular auxiliary groove is provided between the two magnetic steels.

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