Single-polarity surface-mounted permanent magnet motor rotor with three-surface cooperative interception type sinusoidal harmonic wave profile

Abstract

This invention discloses a unipolar surface-mount permanent magnet motor rotor with a three-surface co-selective sinusoidal harmonic profile. The rotor includes a rotor core and unipolar surface-mount permanent magnets arranged circumferentially. The permanent magnets form N-pole magnetic poles, and the rotor core salient pole teeth between adjacent N-pole permanent magnets form equivalent S-pole magnetic poles opposite to the N-pole permanent magnets in the magnetic circuit. The outer surface of the permanent magnets on the air gap side, the air gap side surface of the rotor core salient pole teeth, and the inner surface of the permanent magnets each adopt a selective sinusoidal harmonic profile with different parameter selection rules. This profile is generated by combining a segment of a composite sine function formed by the superposition of the fundamental sine component and harmonic sine components including the third harmonic sine component. This invention can reduce torque ripple, cogging torque, and back EMF harmonic distortion rate, and is suitable for unipolar surface-mount permanent magnet synchronous motors with high requirements for smooth operation and low vibration and noise.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, specifically to a unipolar surface-mount permanent magnet synchronous motor rotor structure, and more particularly to a rotor structure in which the N pole is formed by a surface-mount permanent magnet, the S pole is formed by the rotor core salient pole teeth in the magnetic circuit equivalently, and a three-surface synergistic truncated sinusoidal harmonic profile is adopted on the outer surface of the air gap side of the permanent magnet, the air gap side surface of the rotor core salient pole teeth, and the inner surface of the permanent magnet. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) offer advantages such as high power density, high efficiency, compact structure, and excellent control performance, making them widely used in electric vehicles, rail transportation, power equipment, industrial servo systems, and high-end manufacturing. For high-power-density PMSMs, average torque, torque ripple, cogging torque, back EMF harmonic distortion rate, and the amount of permanent magnets used are crucial indicators affecting the motor's overall performance.

[0003] Unipolar surface-mount permanent magnet synchronous motors typically utilize surface-mount permanent magnets to form a single-polarity magnetic pole, while the rotor core salient pole teeth form an equivalent magnetic pole of opposite polarity in the magnetic circuit. Compared to the traditional all-permanent magnet structure, the unipolar structure reduces the amount of permanent magnets used and improves the utilization rate of permanent magnet materials. However, because the magnetomotive force of the permanent magnet pole and the core salient pole originates from different sources, the unipolar structure is prone to problems such as air gap magnetic flux density imbalance, abrupt changes in magnetic flux density at the pole junction, increased back EMF harmonics, torque pulsation, and increased cogging torque.

[0004] Existing technologies for reducing torque ripple and cogging torque include optimizing the pole arc coefficient, changing the permanent magnet width, using skewed slots or poles, altering the air gap side profile of the magnet, setting auxiliary slots, or using segmented permanent magnets. These methods can improve the torque smoothness of the motor to some extent, but for unipolar surface-mounted permanent magnet synchronous motors, simply optimizing the permanent magnet width or using ordinary circular arcs or ordinary sinusoidal shaping is insufficient to simultaneously address average torque, cogging torque, torque ripple, total harmonic distortion (THD) of back EMF, and the amount of permanent magnet used. Especially when the rotor core salient pole teeth replace part of the permanent magnet poles, the magnetic circuit asymmetry between the permanent magnet poles and the core salient poles becomes more pronounced, and ordinary pole shaping methods are insufficient to adequately adapt to this asymmetrical magnetic circuit.

[0005] Therefore, it is necessary to propose a rotor surface and permanent magnet shape co-optimization structure suitable for unipolar surface-mount permanent magnet synchronous motors, so as to reduce torque pulsation, cogging torque and back EMF harmonic distortion rate while maintaining a high average torque, and avoid the material consumption and cost increase caused by simply increasing the overall thickness of the permanent magnet.

[0006] A search revealed that Chinese invention patent CN104184236A discloses a permanent magnet for an electric motor. The motor includes a rotor and a stator, with an air gap between them. The permanent magnet comprises a base surface that is in contact with the outer surface of the rotor; and an upper surface opposite the air gap. The outline of the upper surface is a curve formed by the superposition of a sine wave and a third harmonic function, the specific shape of which is determined by a function expressed by the following formula. The advantages of this invention are: by obtaining a new permanent magnet structure through a sine wave plus an optimal third harmonic function, the torque output is increased without increasing the motor's torque pulsation. The motor has advantages such as high power density, high efficiency and energy saving, smooth operation, and low noise.

[0007] The technical differences between this application and the aforementioned patent are as follows:

[0008] The permanent magnet in the patent "Permanent magnet for motor, wherein the motor" adopts a sinusoidal + third harmonic permanent magnet upper surface profile, while the permanent magnet synchronous motor rotor structure of this application is a unipolar structure, three-surface coordination, and a cut-and-paste profile, which is fundamentally different from the above patent.

[0009] A search revealed that Chinese invention patent CN116207882A discloses a design method for the rotor magnetic poles of a permanent magnet motor. The method involves first modeling the rotor magnetic poles, determining their shape using eccentricity, pole width, and pole thickness, then calculating the air gap magnetic flux density using simulation software, performing Fourier decomposition on the air gap magnetic flux density, analyzing the magnitude of the fundamental and harmonic components, increasing or decreasing the pole thickness and width based on the air gap magnetic flux density value, and increasing or decreasing the eccentricity based on the air gap magnetic flux density waveform. Finally, the air gap magnetic flux density waveform is iteratively optimized until the air gap magnetic flux density meets the design requirements and its waveform is closest to a sine wave. This invention effectively reduces harmonic components in the air gap magnetic field while optimizing the rotor assembly structure, improving the sine wave of the magnetic field, increasing the utilization rate of the permanent magnet, and reducing motor vibration and noise.

[0010] The technical differences between this application and the aforementioned patent are as follows:

[0011] The patent "A Design Method for Rotor Magnetic Pole of a Permanent Magnet Motor" adopts an iterative design of magnetic poles based on eccentricity, pole width, and thickness, while this application has a clearly defined truncated sinusoidal harmonic function and a three-surface structure, which is fundamentally different from the aforementioned patent.

[0012] A search revealed Chinese invention patent CN107492960A, which discloses a lamination outer circular structure for a permanent magnet synchronous motor rotor. This structure includes several salient poles, each comprising arc segments and straight segments connected by rounded corners. These salient poles are arranged in a circular array to form the outer circular structure. The line connecting the apex of a salient pole to the center of the outer circle passes through the geometric center of the permanent magnet, and the line connecting the lowest point of a salient pole to the center of the outer circle passes through the boundary line between two adjacent permanent magnets. The arc segments satisfy a sine function. The arc segments of the salient poles in this invention can be drawn using a specific sine function, minimizing human interference during the drawing process and improving the precision of the salient poles. This results in a sinusoidal distribution of the air gap magnetic density in the motor. Furthermore, based on the principle that magnetic flux passes through at the lowest possible magnetic reluctance, the back EMF waveform during rotor rotation also exhibits a sinusoidal distribution, reducing the influence of motor back EMF harmonics in the existing equations describing the sinusoidal arc profile of the magnetic pole surface.

[0013] The technical differences between this application and the aforementioned patent are as follows:

[0014] The patent "A lamination outer circle structure of a permanent magnet synchronous motor rotor" uses a salient pole sinusoidal function arc of the rotor lamination outer circle; the difference between this application and "A lamination outer circle structure of a permanent magnet synchronous motor rotor" is that the former uses a single-surface sinusoidal outer circle of the iron core, while this application uses a three-surface sinusoidal harmonic synergy, which is fundamentally different from the above patent. Summary of the Invention

[0015] The purpose of this invention is to provide a unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile, so as to solve the problem of asymmetrical magnetic circuit caused by the different sources of magnetomotive force of the N-pole permanent magnet and the equivalent S-pole iron core in unipolar surface-mount permanent magnet synchronous motor, and reduce the resulting problems of air gap magnetic flux density distortion, large torque pulsation, large cogging torque and high back EMF THD.

[0016] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0017] A unipolar surface-mount permanent magnet motor rotor with a three-surface co-cutting sinusoidal harmonic profile includes a rotor core, rotor core salient pole teeth mounted on the rotor core, and unipolar surface-mount permanent magnets arranged circumferentially along the rotor core, wherein the rotor core salient pole teeth are located between two adjacent unipolar surface-mount permanent magnets.

[0018] The unipolar surface-mount permanent magnet forms an N-pole magnetic pole on the periphery of the rotor core, and the salient pole teeth of the rotor core form an equivalent S-pole magnetic pole opposite to the N-pole magnetic pole on the periphery of the rotor core.

[0019] The unipolar surface-mount permanent magnet has its side adjacent to the air gap as the magnet air gap side, and its side adjacent to the rotor core salient pole teeth as the magnet inner side. The side of the rotor core salient pole teeth adjacent to the air gap is the salient pole tooth air gap side. The outer surfaces of both the magnet air gap side and the salient pole tooth air gap side are constrained by the rotor outer diameter reference circle. The magnet air gap side, the magnet inner side, and the salient pole tooth air gap side all adopt truncated sinusoidal harmonic profiles, and the three sinusoidal harmonic profiles respectively truncate segments with different profile parameters.

[0020] The truncated sinusoidal harmonic profile is generated by combining a predetermined number of segments from a composite sine function obtained by superimposing the fundamental sine component and harmonic sine components, including the third harmonic sine component.

[0021] The composite sine function comprises two functions with different parameters. Segments are extracted from the normalized intervals of the positive half-cycles of each function, and the extracted segments are combined, mirrored by the N / S magnetic pole centerline, and then connected end to end to form the magnetic pole profile.

[0022] By adjusting the radial offset, fundamental amplitude coefficient, frequency coefficient, and harmonic amplitude coefficient of the three magnetic pole profiles respectively, the edge thickness of the unipolar surface-mount permanent magnet, the magnetic flux at the center of the N / S magnetic pole, and the air gap magnetic flux distribution at the N / S magnetic pole junction can be adjusted in a coordinated manner.

[0023] As a preferred technical solution of the present invention: the positive half-cycle normalization interval is the interval obtained by normalizing the interval from 0 to π / 2 to 0 to 1 by a composite sine function with two different parameters;

[0024] The truncated segments include a first truncated segment of the composite sine function with the first parameter located on the normalized interval from 0 to α, and a second truncated segment of the composite sine function with the second parameter located on the normalized interval from β to 1, where α is 0.3 to 0.5 and β is 0.7 to 0.9.

[0025] The first and second segments form one side of the magnetic pole profile curve, while the other side curve is arranged symmetrically about the N / S magnetic pole centerline.

[0026] The connection point between the first and second segments is defined on the rotor outer diameter reference circle. The starting point of the first segment is located on the rotor outer diameter reference circle or offset radially towards the rotation axis relative to the rotor outer diameter reference circle.

[0027] The endpoint of the second segment does not exceed the rotor outer diameter reference circle;

[0028] The first segment, the second segment, and their mirror image segments form an overall outline through continuous connection, tangential continuous connection, rounded corner transition, spline transition, or local chamfering.

[0029] As a preferred embodiment of the present invention: the truncated sinusoidal harmonic profile is represented in the local coordinate system as follows:

[0030] (1);

[0031] Among them, the preferred harmonic sinusoidal component is the third harmonic sinusoidal component. The dimensionless independent variable is normalized along the circumferential width direction of the N / S magnetic poles. The frequency coefficient is a dimensionless frequency coefficient. This is the radial offset relative to the rotor's outer diameter reference circle or relative to a preset inner surface reference line. , and and Using the same unit of length, The amplitude coefficient of the fundamental sinusoidal component. The amplitude coefficient of the third harmonic sinusoidal component. This is the radial offset.

[0032] As a preferred embodiment of the present invention: the air gap side of the magnet includes a first outer surface segment and a second outer surface segment.

[0033] The first segment of the outer surface is represented as:

[0034] (2);

[0035] The second outer surface segment is represented as follows:

[0036] (3);

[0037] in, , Used to adjust the edge thickness of unipolar surface-mount permanent magnets. , , , , and Used to adjust the air gap magnetic flux density distribution of the N pole.

[0038] As a preferred embodiment of the present invention: the salient pole tooth air gap side includes a first salient pole tooth segment and a second salient pole tooth segment.

[0039] The first salient pole tooth segment is represented as:

[0040] (4);

[0041] The second salient pole tooth segment is represented as follows:

[0042] (5);

[0043] in, , Used to adjust the edge thickness of unipolar surface-mount salient pole teeth. , , , , and Used to adjust the air gap magnetic flux density distribution of salient pole teeth;

[0044] The first salient pole tooth segment and the second salient pole tooth segment are used to mitigate the sudden change in magnetic flux density at the interface between the unipolar surface-mount permanent magnet and the salient pole tooth of the rotor core.

[0045] As a preferred embodiment of the present invention: the inner side of the magnet body includes a first inner surface segment and a second inner surface segment.

[0046] The first inner surface segment is represented as follows:

[0047] (6);

[0048] The second inner surface segment is represented as follows:

[0049] (7);

[0050] in, , Used to adjust the edge thickness of unipolar surface-mount permanent magnets. , , , , and Used to adjust the effective thickness distribution of the N-pole permanent magnet;

[0051] By adjusting the parameters of the first inner surface segment and the second inner surface segment, the unipolar surface-mount permanent magnet can form a non-uniform thickness cross section with an effective thickness that gradually decreases from the middle to both sides and the effective thickness on both sides is adjustable.

[0052] As a preferred embodiment of the present invention, the parameters of the magnet air gap side, the salient pole tooth air gap side, and the magnet inner side satisfy the following constraints:

[0053] The radial offset of the magnet air gap side and the salient pole tooth air gap side relative to the rotor outer diameter reference circle does not reduce the minimum value of the main air gap.

[0054] The radial offset of the inner side of the magnet relative to the preset inner surface reference line does not cause the local thickness of the unipolar surface-mount permanent magnet to be less than the minimum thickness allowed by mechanical strength and magnetization requirements.

[0055] The absolute values ​​of D11, D21, and D31 do not exceed the thickness of the unipolar surface-mount permanent magnet;

[0056] The values ​​of D12, D22, and D32 are all 0.

[0057] As a preferred technical solution of the present invention: the preferred parameter range of the air gap side surface of the magnet is:

[0058] A11 is 0.0004 to 0.0005, B11 is 39 to 40, C11 is 0.0036 to 0.0038, and D11 is 0.2 to 0.4; A12 is 0.0003 to 0.0004, B12 is 78 to 79, and C12 is 0.00011 to 0.00013.

[0059] As a preferred technical solution of the present invention: the preferred parameter range of the air gap side surface of the salient pole tooth is:

[0060] A21 is 0.0008 to 0.0009, B21 is 81 to 82, C21 is 0.0004 to 0.0005, D21 is 0 to 0.3; A22 is 0.0009 to 0.0010, B22 is 162 to 163, C22 is 0.00009 to 0.00010.

[0061] As a preferred technical solution of the present invention: the preferred parameter range of the inner surface of the magnet is:

[0062] A31 is -9.4 to -9.3, B31 is 50 to 51, C31 is -85 to -84, D31 is -3.4 to -3.2; A32 is -0.004 to -0.003, B32 is 101 to 102, C32 is 0.002 to 0.003.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] 1. For the asymmetric magnetic circuit of unipolar surface-mount permanent magnet synchronous motor, not only is the air gap side of the magnet shaped, but also the air gap side surface of the iron core salient pole tooth and the inner surface of the permanent magnet are designed in a coordinated manner to mitigate the sudden change in magnetic flux density at the N / S magnetic pole junction.

[0065] 2. It adopts a truncated sinusoidal harmonic profile instead of a regular circular arc, a complete sine wave, or a single surface cut, which gives it greater freedom in adjusting the magnetic flux density at the pole edges, pole centers, and boundary regions.

[0066] 3. Without reducing the minimum value of the main air gap, by adjusting the edge thickness of the permanent magnet and the local air gap magnetic flux density through radial offset, fundamental amplitude coefficient, frequency coefficient and harmonic amplitude coefficient, it is possible to reduce torque pulsation, cogging torque and back EMF THD while maintaining a high level of average torque. Attached Figure Description

[0067] Figure 1 This is a schematic diagram of a two-dimensional cross-sectional model of a unipolar surface-mount permanent magnet synchronous motor using a three-surface collaborative truncated sinusoidal harmonic profile in an embodiment of the present invention.

[0068] Figure 2 This is a schematic diagram of the cross-sectional shape of a permanent magnet using a truncated sinusoidal harmonic profile in an embodiment of the present invention;

[0069] Figure 3 This is a schematic diagram of the cross-sectional shape of the salient pole tooth of the rotor core using a truncated sinusoidal harmonic profile in an embodiment of the present invention.

[0070] Figure 4 This is a schematic diagram of the truncated sinusoidal harmonic profile generation method;

[0071] Figure 5 This is a schematic diagram comparing the performance of the baseline circular arc structure and the optimized structure of this invention.

[0072] List of reference numerals in the attached diagram:

[0073] 1. Rotor core; 2. Unipolar surface-mount permanent magnet; 21. Magnet air gap side; 22. Magnet inner side; 3. Rotor core salient pole tooth; 31. Salient pole tooth air gap side; 4. First segment; 5. Second segment; 6. Sine curve height; 7. Permanent magnet symmetry axis; 8. Rotor outer diameter reference circle; 9. Permanent magnet width and coordinate axes for establishing the curve. Detailed Implementation

[0074] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0075] like Figures 1-5 As shown, the unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile proposed in this invention includes a rotor core 1, rotor core salient pole teeth 3 mounted on the rotor core 1, and unipolar surface-mount permanent magnets 2 arranged circumferentially along the rotor core 1. The rotor core salient pole teeth 3 are located between two adjacent unipolar surface-mount permanent magnets 2.

[0076] The unipolar surface-mount permanent magnet 2 forms an N-pole magnetic pole on the periphery of the rotor core 1, and the rotor core salient pole teeth 3 form an equivalent S-pole magnetic pole opposite to the N-pole magnetic pole on the periphery of the rotor core 1.

[0077] The unipolar surface-mount permanent magnet 2 has its side adjacent to the air gap as the magnet air gap side 21, and its side adjacent to the rotor core salient pole teeth 3 as the magnet inner side 22. The side of the rotor core salient pole teeth 3 adjacent to the air gap is the salient pole tooth air gap side 31. The outer surfaces of both the magnet air gap side 21 and the salient pole tooth air gap side 31 are constrained by the rotor outer diameter reference circle 8. The magnet air gap side 21, the magnet inner side 22, and the salient pole tooth air gap side 31 all adopt truncated sinusoidal harmonic profiles, and the three sinusoidal harmonic profiles respectively truncate segments with different profile parameters.

[0078] The truncated sinusoidal harmonic profile is generated by combining a predetermined number of segments from a composite sine function obtained by superimposing the fundamental sine component and harmonic sine components, including the third harmonic sine component.

[0079] The composite sine function comprises two functions with different parameters. Segments are extracted from the normalized intervals of the positive half-cycles of each function, and the extracted segments are combined, mirrored by the N / S magnetic pole centerline, and then connected end to end to form the magnetic pole profile.

[0080] By adjusting the radial offset, fundamental amplitude coefficient, frequency coefficient, and harmonic amplitude coefficient of the three magnetic pole profiles respectively, the edge thickness of the unipolar surface-mount permanent magnet 2, the magnetic flux at the center of the N / S magnetic pole, and the air gap magnetic flux distribution at the N / S magnetic pole junction can be adjusted in a coordinated manner.

[0081] In this embodiment, since the N-pole magnetic pole is directly provided with magnetomotive force by the unipolar surface-mounted permanent magnet 2, while the equivalent S-pole magnetic pole is mainly formed by the rotor core salient pole and magnetic flux loop, the two types of magnetic poles are asymmetrical in terms of magnetic flux amplitude, magnetic flux gradient and magnetic flux distribution at the interface.

[0082] To accommodate this asymmetrical magnetic circuit, in this embodiment, the air gap side 21 and the inner side 22 of the unipolar surface-mount permanent magnet 2, as well as the air gap side 31 of the salient pole teeth on the rotor core salient pole, are all set as truncated sinusoidal harmonic profiles, but the parameters of the three profiles are independent of each other. Thus, the air gap side 21 is mainly used to adjust the magnetic flux density of the N pole air gap, the surface of the salient pole tooth air gap side 31 is mainly used to mitigate the abrupt change in magnetic flux density at the N / S junction, and the surface of the inner side 22 of the magnet is mainly used to adjust the effective thickness distribution of the unipolar surface-mount permanent magnet 2.

[0083] Contour generation method

[0084] In this embodiment, the positive half-cycle normalization interval is the interval obtained by normalizing the interval from 0 to π / 2 to 0 to 1 using a composite sine function with two different parameters;

[0085] The extracted segments include a first segment 4, where the composite sine function of the first parameter lies on the normalized interval from 0 to α, and a second segment 5, where the composite sine function of the second parameter lies on the normalized interval from β to 1, wherein α is 0.3 to 0.5 and β is 0.7 to 0.9.

[0086] The first segment 4 and the second segment 5 form one side curve of the magnetic pole profile, while the other side curve is arranged symmetrically about the center line of the N / S magnetic poles.

[0087] The connection point between the first segment 4 and the second segment 5 is defined on the rotor outer diameter reference circle 8. The starting point of the first segment 4 is located on the rotor outer diameter reference circle 8 or offset radially towards the rotation axis relative to the rotor outer diameter reference circle 8.

[0088] The endpoint of the second segment 5 does not exceed the rotor outer diameter reference circle 8;

[0089] The first segment 4, the second segment 5, and their mirror segments form an overall outline through continuous connection, tangential continuous connection, rounded corner transition, spline transition, or local chamfering.

[0090] The local coordinate system of the truncated sinusoidal harmonic profile is defined as follows: with the magnetic pole centerline as the axis of symmetry, the circumferential width direction of the magnetic pole as the transverse coordinate, and the radial offset direction as the longitudinal coordinate; the circumferential interval corresponding to one side of the magnetic pole profile is normalized to t∈[0,1]. Within this normalized interval, the first truncated segment 4 on t∈[0,α] and the second truncated segment 5 on t∈[β,1] are selected, where α is 0.3 to 0.5 and β is 0.7 to 0.9; in the preferred embodiment, α=0.4 and β=0.8.

[0091] Each segment is obtained by superimposing the fundamental sinusoidal component and harmonic sinusoidal components, including the third harmonic sinusoidal component, wherein the third harmonic sinusoidal component is preferred, and its general expression is:

[0092] (1);

[0093] Among them, the preferred harmonic sinusoidal component is the third harmonic sinusoidal component. The dimensionless independent variable is normalized along the circumferential width direction of the N / S magnetic poles. The frequency coefficient is a dimensionless frequency coefficient. This is the radial offset relative to the rotor outer diameter reference circle 8 or relative to the preset inner surface reference line. , and and Using the same unit of length, The amplitude coefficient of the fundamental sinusoidal component. The amplitude coefficient of the third harmonic sinusoidal component. This is the radial offset.

[0094] For example, when finite element modeling software uses millimeters as the geometric unit, A, C, D, and y(t) are all measured in millimeters; when meters are used as the geometric unit, A, C, D, and y(t) are all measured in meters. Different surfaces may have different order of magnitudes of parameters due to differences in local coordinate reference lines and scales.

[0095] The first segment 4 and the second segment 5 form one side curve of the magnetic pole profile, and the other side curve is arranged in mirror image with respect to the magnetic pole centerline. The connection point between the first segment 4 and the second segment 5 is located on the rotor outer diameter reference circle 8. The starting point of the first segment 4 is located on the rotor outer diameter reference circle 8 or offset radially towards the rotation axis relative to the rotor outer diameter reference circle 8, and the ending point of the second segment 5 does not exceed the rotor outer diameter reference circle 8. When the radial distance from the rotor center to any point on the air gap side profile is not greater than the radius of the rotor outer diameter reference circle 8, it is considered that the air gap side profile does not exceed the rotor outer diameter reference circle 8, thereby ensuring that the minimum value of the main air gap is not reduced. The starting point of the first segment 4 can be moved radially towards the rotation axis according to the edge thickness requirements of the unipolar surface-mounted permanent magnet 2, and the moving distance does not exceed the thickness of the unipolar surface-mounted permanent magnet 2.

[0096] To meet actual processing requirements, the first segment 4, the second segment 5, and their mirror images can be smoothly connected using methods such as continuous connection, tangential continuous connection, rounded corner transition, spline transition, or local chamfering. These transitions do not change the technical essence of three-surface coordinated magnetization; their purpose is to avoid magnetic congestion or processing difficulties caused by sharp corners.

[0097] Three-surface co-contour parameters

[0098] In this embodiment, the surface of the magnet air gap side 21 includes a first outer surface segment and a second outer surface segment.

[0099] The first segment of the outer surface is represented as:

[0100] (2);

[0101] The second outer surface segment is represented as follows:

[0102] (3).

[0103] in, , Used to adjust the edge thickness of the unipolar surface-mount permanent magnet 2. , , , , and Used to adjust the air gap magnetic flux density distribution of the N pole.

[0104] Preferably, A11 is 0.0004124, B11 is 39.26, C11 is 0.0037116, and D11 is 0.3; A12 is 0.0003935, B12 is 78.52, C12 is 0.00011805, and D12 is 0.

[0105] The surface of the salient pole tooth air gap side 31 includes a first salient pole tooth segment and a second salient pole tooth segment.

[0106] The first salient pole tooth segment is represented as:

[0107] (4);

[0108] The second salient pole tooth segment is represented as follows:

[0109] (5);

[0110] in, , Used to adjust the edge thickness of unipolar surface-mount salient pole teeth 3. , , , , and Used to adjust the air gap magnetic flux density distribution of the salient pole tooth 3 magnetic pole;

[0111] The first salient pole tooth segment and the second salient pole tooth segment are used to mitigate the sudden change in magnetic flux density at the interface between the unipolar surface-mount permanent magnet 2 and the rotor core salient pole tooth 3.

[0112] Preferably, A21 is 0.0008574, B21 is 81.3935, C21 is 0.0004287, and D21 is 0; A22 is 0.0009345, B22 is 162.787, C22 is 0.00009345, and D22 is 0. The first salient pole tooth segment and the second salient pole tooth segment are used to mitigate the abrupt change in magnetic flux density at the interface between the surface-mounted permanent magnet and the salient pole tooth 3 of the rotor core.

[0113] The inner surface of the magnet body 22 includes a first inner surface segment and a second inner surface segment. The first inner surface segment is represented as follows:

[0114] (6);

[0115] The second inner surface segment is represented as follows:

[0116] (7);

[0117] in, , Used to adjust the edge thickness of the unipolar surface-mount permanent magnet 2. , , , , and Used to adjust the effective thickness distribution of the N-pole permanent magnet;

[0118] By adjusting the parameters of the first inner surface segment and the second inner surface segment, the unipolar surface-mount permanent magnet 2 forms a non-uniform thickness cross section with an effective thickness that gradually decreases from the middle to both sides and the effective thickness on both sides is adjustable.

[0119] Preferably, A31 is -9.3776, B31 is 50.9457, C31 is -84.3984, and D31 is -3.3; A32 is -0.0033734, B32 is 101.8914, C32 is 0.00236138, and D32 is 0. By adjusting the parameters of the first and second inner surface segments, the unipolar surface-mount permanent magnet 2 forms a non-uniform thickness cross-section with a larger effective thickness in the middle and adjustable effective thickness on both sides. For the inner surface of the unipolar surface-mount permanent magnet 2, the local thickness at any circumferential position of the unipolar surface-mount permanent magnet 2 is determined by the radial distance between the outer surface and the inner surface on the air gap side at that position. The local thickness should not be less than the minimum thickness allowed by mechanical strength and magnetization requirements. The minimum thickness can be determined according to the material strength, processing accuracy, magnetization direction, and assembly requirements of the unipolar surface-mount permanent magnet 2.

[0120] The above parameters are not limited to a specific motor size, but are used to describe a preferred implementation of the three-surface synergistic truncated sinusoidal harmonic profile. Those skilled in the art can adjust or re-optimize these parameters proportionally based on the motor radius, air gap length, pole arc width, thickness of the unipolar surface-mount permanent magnet 2, slot-pole fit, and target performance requirements. As long as the above-mentioned truncated sinusoidal harmonic profile is adopted, and the outer surface of the magnet air gap side 21, the surface of the salient pole tooth air gap side 31, and the inner surface of the magnet body 22 respectively undertake the synergistic effects of air gap magnetic flux density adjustment, mitigation of magnetic flux density abrupt changes at the interface, and effective thickness adjustment of the unipolar surface-mount permanent magnet 2, it falls within the technical concept of this invention.

[0121] Proportional Setting and Creative Explanation

[0122] To demonstrate that the technical effect of this invention does not originate from ordinary circular arc trimming, ordinary complete sinusoidal harmonic double-surface trimming, or conventional double-surface parameter optimization, this embodiment sets up multiple sets of comparative examples for finite element verification. Comparative example one is an ordinary circular arc trimming structure; comparative example two is a double-surface trimming structure in which both the outer surface of the magnet air gap side 21 and the surface of the salient pole tooth air gap side 31 adopt complete sinusoidal harmonic profiles; comparative example three is a double-surface trimming structure in which both the outer surface of the magnet air gap side 21 and the surface of the salient pole tooth air gap side 31 adopt truncated sinusoidal harmonic profiles; the embodiment is a three-surface collaborative trimming structure in which the outer surface of the magnet air gap side 21, the surface of the salient pole tooth air gap side 31, and the inner surface of the magnet 22 all adopt truncated sinusoidal harmonic profiles with different parameter selection rules, as shown in Table 1.

[0123] The above comparative examples are used to distinguish the technical differences between this invention and ordinary circular arc trimming, complete sinusoidal harmonic double-surface trimming, and truncated sinusoidal harmonic double-surface trimming. The core of this invention does not lie in using a single sine curve in isolation, nor in trimming only the double surfaces on the rotor air gap side, but rather in addressing the asymmetric magnetic circuit between the N-pole unipolar surface-mounted permanent magnet 2 and the equivalent S-pole rotor core salient pole teeth 3 of a unipolar motor. It treats the outer surface of the magnet air gap side 21, the surface of the salient pole tooth air gap side 31, and the inner surface 22 of the magnet as interconnected magnetic adjustment objects, and collaboratively designs three aspects: N-pole air gap magnetic flux density, magnetic flux density abrupt change at the N / S junction, and the effective thickness distribution of the unipolar surface-mounted permanent magnet 2.

[0124] The complete sinusoidal harmonic double-surface trimming can improve some back EMF harmonics, but its overall improvement on cogging torque and torque ripple is limited. The truncated sinusoidal harmonic double-surface trimming further reduces cogging torque and torque ripple, indicating that the truncated profile is more suitable for unipolar asymmetric magnetic circuits. On this basis, the three-surface synergistic truncated sinusoidal harmonic trimming structure further adjusts the effective thickness distribution of the inner surface of the permanent magnet body, so that the magnetic supply capacity of the unipolar surface-mounted permanent magnet 2, the magnetic flux density transition at the junction of the rotor core salient pole teeth 3 and the magnetic flux density distribution on the air gap side form a synergistic match, thereby further reducing torque ripple while maintaining a high average torque, and maintaining a low cogging torque and back EMF harmonic distortion rate.

[0125] Therefore, the three contours are not optimized independently, but correspond to three coupling links: N-pole magnetization, equivalent S-pole magnetic flux density transition, and effective thickness redistribution of unipolar surface-mount permanent magnet 2. If only one surface is optimized or only the two surfaces on the air gap side are optimized, it is difficult to simultaneously take into account torque pulsation, cogging torque, and back EMF (THD).

[0126] Table 1

[0127]

[0128] Finite element simulation and effect

[0129] A finite element simulation model was established using the above method. The function coefficients of the edge thickness of the unipolar surface-mount permanent magnet 2, the outer surface of the magnet air gap side 21, the surface of the salient pole tooth air gap side 31, and the inner surface of the magnet 22 were set as independent controllable parameters. Parameter scanning optimization was performed within the parameter range to select the parameter set that can reduce torque ripple, cogging torque, and back EMF THD while maintaining a high average torque.

[0130] In one set of embodiments, the average torque of the ordinary arc-shaped structure is approximately 185.0 N·m, the torque ripple is approximately 1.4074%, the permanent magnet utilization rate is approximately 38.17%, the cogging torque is approximately 5.193 N·m, and the back EMF THD is approximately 9.79%.

[0131] The average torque of the complete sinusoidal harmonic double-surface veneer structure is approximately 179.1 N·m, the torque ripple is approximately 1.3371%, the permanent magnet utilization rate is approximately 38.22%, the cogging torque is approximately 5.376 N·m, and the back EMF THD is approximately 7.67%.

[0132] The average torque of the truncated sinusoidal harmonic double-surface shaped structure is approximately 176.2 N·m, the torque ripple is approximately 1.2070%, the permanent magnet utilization rate is approximately 38.20%, the cogging torque is approximately 4.041 N·m, and the back EMF THD is approximately 7.32%.

[0133] After adopting the three-surface collaborative interception sinusoidal harmonic profile of the present invention, the average torque is about 178.5 N·m, the torque ripple is about 1.1644%, the permanent magnet utilization rate is about 36.00%, the cogging torque is about 4.018 N·m, and the back EMF THD is about 7.47%.

[0134] The performance comparison of the embodiments is shown in Table 2:

[0135] Table 2

[0136]

[0137] As shown in Table 2, the objective of this invention is not solely to maximize average torque across all metrics, but rather to comprehensively improve the torque stability and back EMF waveform quality of a unipolar surface-mount permanent magnet synchronous motor while maintaining a high average torque level. Compared to the complete sinusoidal harmonic double-surface trimming, the truncated sinusoidal harmonic double-surface trimming significantly reduces torque ripple and cogging torque. Compared to the truncated sinusoidal harmonic double-surface trimming, the three-surface synergistic truncated sinusoidal harmonic trimming structure further reduces torque ripple and maintains cogging torque at a low level, indicating that the effective thickness redistribution of the permanent magnet's inner surface contributes further to the synergistic magnetization of the three surfaces. For applications requiring high power density, high stability, and low vibration and noise, this comprehensive performance improvement has practical engineering significance.

[0138] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A unipolar surface-mount permanent magnet motor rotor with a three-surface co-cutting sinusoidal harmonic profile, comprising a rotor core (1), rotor core salient pole teeth (3) mounted on the rotor core (1), and unipolar surface-mount permanent magnets (2) arranged circumferentially along the rotor core (1), wherein the rotor core salient pole teeth (3) are located between two adjacent unipolar surface-mount permanent magnets (2). The unipolar surface-mount permanent magnet (2) forms an N-pole magnetic pole on the periphery of the rotor core (1), and the rotor core salient pole teeth (3) form an equivalent S-pole magnetic pole opposite to the N-pole magnetic pole on the periphery of the rotor core (1). Its features are: The unipolar surface-mount permanent magnet (2) has a magnet air gap side (21) adjacent to the air gap and a magnet inner side (22) adjacent to the rotor core salient pole teeth (3). The rotor core salient pole teeth (3) has a salient pole tooth air gap side (31) adjacent to the air gap. The outer surfaces of the magnet air gap side (21) and the salient pole tooth air gap side (31) are constrained by the rotor outer diameter reference circle (8). The magnet air gap side (21), the magnet inner side (22), and the salient pole tooth air gap side (31) all adopt a truncated sinusoidal harmonic profile, and the three sinusoidal harmonic profiles respectively truncate segments with different profile parameters. The truncated sinusoidal harmonic profile is generated by combining a predetermined number of segments from a composite sine function obtained by superimposing the fundamental sine component and harmonic sine components, including the third harmonic sine component. The composite sine function comprises two functions with different parameters. Segments are extracted from the normalized intervals of the positive half-cycles of each function, and the extracted segments are combined, mirrored by the N / S magnetic pole centerline, and then connected end to end to form the magnetic pole profile. By adjusting the radial offset, fundamental amplitude coefficient, frequency coefficient, and harmonic amplitude coefficient of the three magnetic pole profiles respectively, the edge thickness of the unipolar surface-mount permanent magnet (2), the magnetic flux at the center of the N / S magnetic pole, and the air gap magnetic flux distribution at the junction of the N / S magnetic poles can be adjusted in a coordinated manner.

2. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 1, characterized in that: The positive half-cycle normalized interval is the interval obtained by normalizing the interval from 0 to π / 2 to 0 to 1 using a composite sine function with two different parameters. The truncated segments include a first truncated segment (4) of the composite sine function with the first parameter located on the normalized interval from 0 to α, and a second truncated segment (5) of the composite sine function with the second parameter located on the normalized interval from β to 1, where α is 0.3 to 0.5 and β is 0.7 to 0.

9. The first segment (4) and the second segment (5) form one side curve of the magnetic pole profile, while the other side curve is arranged symmetrically about the center line of the N / S magnetic pole. The connection point of the first segment (4) and the second segment (5) is defined on the rotor outer diameter reference circle (8). The starting point of the first segment (4) is located on the rotor outer diameter reference circle (8) or offset radially toward the rotation axis relative to the rotor outer diameter reference circle (8). The endpoint of the second segment (5) does not exceed the rotor outer diameter reference circle (8); The first segment (4), the second segment (5) and their mirror segments form an overall outline through continuous connection, tangential continuous connection, rounded transition, spline transition or local chamfering.

3. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 1, characterized in that: The truncated sinusoidal harmonic profile is represented in the local coordinate system as follows: （1）； Among them, the preferred harmonic sinusoidal component is the third harmonic sinusoidal component. The dimensionless independent variable is normalized along the circumferential width direction of the N / S magnetic poles. The frequency coefficient is a dimensionless frequency coefficient. This is the radial offset relative to the rotor outer diameter reference circle (8) or relative to the preset inner surface reference line. , and and Using the same unit of length, The amplitude coefficient of the fundamental sinusoidal component. The amplitude coefficient of the third harmonic sinusoidal component. This is the radial offset.

4. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 1, characterized in that: The air gap side (21) of the magnet includes a first outer surface segment and a second outer surface segment. The first segment cut from the outer surface is represented as follows: （2）； The second outer surface segment is represented as follows: （3）； in, , Used to adjust the edge thickness of unipolar surface-mount permanent magnets (2), , , , , and Used to adjust the air gap magnetic flux density distribution of the N pole.

5. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 1, characterized in that: The salient pole tooth air gap side (31) includes a first salient pole tooth segment and a second salient pole tooth segment. The first salient pole tooth segment is represented as: （4）； The second salient pole tooth segment is represented as follows: （5）； in, , Used to adjust the edge thickness of unipolar surface-mount salient pole teeth (3) , , , , and Used to adjust the air gap magnetic flux density distribution of the salient pole tooth (3); The first salient pole tooth segment and the second salient pole tooth segment are used to mitigate the sudden change in magnetic flux density at the interface between the unipolar surface-mount permanent magnet (2) and the rotor core salient pole tooth (3).

6. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 1, characterized in that: The inner side (22) of the magnet body includes a first inner surface segment and a second inner surface segment. The first inner surface segment is represented as follows: （6）； The second inner surface segment is represented as follows: （7）； in, , Used to adjust the edge thickness of unipolar surface-mount permanent magnets (2), , , , , and Used to adjust the effective thickness distribution of the N-pole permanent magnet; By adjusting the parameters of the first inner surface segment and the second inner surface segment, the unipolar surface-mount permanent magnet (2) forms a non-uniform thickness cross section with an effective thickness that gradually decreases from the middle to both sides and the effective thickness on both sides is adjustable.

7. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to any one of claims 4 to 6, characterized in that: The parameters of the magnet air gap side (21), the salient pole tooth air gap side (31), and the magnet inner side (22) satisfy the following constraints: The radial offset of the magnet air gap side (21) and the salient pole tooth air gap side (31) relative to the rotor outer diameter reference circle (8) does not reduce the minimum value of the main air gap; The radial offset of the inner side (22) of the magnet body relative to the preset inner surface reference line does not cause the local thickness of the unipolar surface-mount permanent magnet (2) to be less than the minimum thickness allowed by mechanical strength and magnetization requirements; The absolute values ​​of D11, D21 and D31 do not exceed the thickness of the unipolar surface-mount permanent magnet (2); The values ​​of D12, D22, and D32 are all 0.

8. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 7, characterized in that: The preferred parameter range for the surface of the magnet air gap side (21) is as follows: A11 is 0.0004 to 0.0005, B11 is 39 to 40, C11 is 0.0036 to 0.0038, and D11 is 0.2 to 0.4; A12 is 0.0003 to 0.0004, B12 is 78 to 79, and C12 is 0.00011 to 0.00013.

9. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 7, characterized in that: The preferred parameter range for the surface of the salient pole tooth air gap side (31) is as follows: A21 is 0.0008 to 0.0009, B21 is 81 to 82, C21 is 0.0004 to 0.0005, D21 is 0 to 0.3; A22 is 0.0009 to 0.0010, B22 is 162 to 163, C22 is 0.00009 to 0.00010.

10. The unipolar surface-mount permanent magnet motor rotor with a three-surface cooperative truncated sinusoidal harmonic profile according to claim 7, characterized in that: The preferred parameter range for the inner surface (22) of the magnet body is: A31 is -9.4 to -9.3, B31 is 50 to 51, C31 is -85 to -84, D31 is -3.4 to -3.2; A32 is -0.004 to -0.003, B32 is 101 to 102, C32 is 0.002 to 0.003.

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