Rotor assembly, electric motor, electric power steering device, and vehicle

Abstract

This invention discloses a rotor assembly, a motor, an electric power steering system, and a vehicle. The rotor assembly includes multiple rotor units arranged at intervals along the axial direction of the rotor core. The m-th rotor unit and the (m+1)-th rotor unit are arranged adjacent to each other along the axial direction of the rotor core. The minimum axial distance between the m-th rotor unit and the (m+1)-th rotor unit is G. m , 0.01≤G m / L r ≤0.16, where L r Let m be the average length of the rotor unit along the axial direction of the rotor core, where m is a natural number greater than or equal to 1. This rotor assembly can effectively solve the problem of magnetic flux interaction between rotor units without significantly changing the electromagnetic torque of the rotor assembly, thereby reducing the cogging torque of the rotor assembly, reducing mechanical vibration and noise, and improving the performance of the rotor assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric machines, in particular, to a rotor assembly, an electric machine having the rotor assembly, an electric power steering device having the electric machine, and an electric vehicle having the electric machine. BACKGROUND

[0002] Permanent magnet machines have the advantages of simple structure, low loss, and high efficiency. However, permanent magnet machines inevitably have cogging torque, which seriously affects the low-speed performance of the permanent magnet machines, and the cogging torque of the permanent magnet machines produces mechanical vibration and noise.

[0003] In the related art, a rotor is segmented and skewed to suppress the cogging torque of the permanent magnet machine. However, due to the misaligned connection between the rotor segments, the magnetic flux is exchanged between the rotor segments, which increases the difference in the magnetic flux density distribution of different rotor segments, greatly weakening the optimization effect of the segmented and skewed rotor. SUMMARY

[0004] The present application aims to at least partially solve one of the technical problems in the related art. To this end, an embodiment of the present application proposes a rotor assembly with small cogging torque and low mechanical vibration.

[0005] An embodiment of the present application further proposes an electric machine.

[0006] An embodiment of the present application further proposes an electric power steering device.

[0007] An embodiment of the present application further proposes a vehicle.

[0008] The rotor assembly according to an embodiment of the first aspect of the present application comprises a plurality of rotor units, each rotor unit comprising a rotor core and a plurality of permanent magnets, the rotor core segment having a plurality of magnet slots arranged at intervals along the circumferential direction of the rotor core; the permanent magnets are arranged in the magnet slots, and a plurality of the permanent magnets and a plurality of the magnet slots correspond to each other, the plurality of rotor units are arranged at intervals along the axial direction of the rotor core, the mth rotor unit and the m+1th rotor unit are arranged adjacent in the axial direction of the rotor core, and the minimum distance G between the mth rotor unit and the m+1th rotor unit in the axial direction of the rotor core is m 0.01≤G m / L r ≤0.16, wherein L i is the length of the ith rotor unit in the axial direction of the rotor core, 1≤i≤n, n is the number of rotor unit segments, and n is a natural number greater than or equal to 2, m is a natural number greater than or equal to 1.

[0009] According to an embodiment of the present invention, the rotor is configured as multiple spaced rotor segments, and the minimum distance G between two adjacent rotor segments is minimized. m The average length Lr of the rotor element in the axial direction of the rotor core satisfies 0.01≤G m / L r With a value ≤0.16, the problem of magnetic flux interaction between rotor units can be effectively solved without significantly changing the electromagnetic torque of the rotor assembly, thereby reducing the cogging torque of the rotor assembly, reducing mechanical vibration and noise, and improving the performance of the rotor assembly.

[0010] Optionally, 0.015 ≤ G m / L r ≤0.07.

[0011] In some embodiments, G m =G n-m Where m≤n-1, G n-m The minimum axial spacing between the nm-th rotor unit and the (n-m+1)-th rotor unit in the rotor core.

[0012] In some embodiments, the skew angle between the m-th rotor unit and the (m+1)-th rotor unit is θ. m , and θ m =θ0+Δθ m θ0 = 360° / (n*N) c ), 0≤Δθ m / θ0≤0.18, where m≤n-1, N c =LCM(Z1,2p), where Z1 is the number of stator slots and p is the number of motor pole pairs.

[0013] Alternatively, 0 < Δθ m / θ0≤0.12.

[0014] In some embodiments, θ m =θ n-m , where θ n-m Let be the skew pole angle of the nm-th rotor unit and the (n-m+1)-th rotor unit.

[0015] In some embodiments, L i =L n-i+1 L n-i+1 Let be the length of the (n-i+1)th rotor unit in the axial direction of the rotor core.

[0016] In some embodiments, there is an air gap between any two adjacent rotor units, or there is a non-magnetic material separating any two adjacent rotor units.

[0017] In some embodiments, among the plurality of rotor units, a part of the rotor units are separated by air gaps between adjacent rotor units, and another part of the rotor units are separated by non-magnetic conductive materials between adjacent rotor units.

[0018] In some embodiments, the air gaps and the non-magnetic conductive materials are alternately arranged along the axial direction of the rotor core.

[0019] In some embodiments, in a projection plane perpendicular to the axial direction of the rotor core, the outer periphery contour of the non-magnetic conductive material is located within the outer periphery contour of the rotor core, or the outer periphery contour of the non-magnetic conductive material is flush with the outer periphery contour of the rotor core.

[0020] The motor according to the embodiments of the second aspect of the present application comprises the rotor assembly according to any one of the above embodiments, and by using the above rotor assembly, the motor has low operation noise and good performance.

[0021] The electric power assisted steering device according to the embodiments of the third aspect of the present application comprises the motor described above, and by using the above motor, the electric power assisted steering system has low operation vibration and low noise.

[0022] The vehicle according to the embodiments of the fourth aspect of the present application comprises the motor described above, and by using the above motor, the vehicle has low operation noise. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of a partial structure of a motor according to embodiments of the present application.

[0024] Figure 2 is a schematic diagram of a partial structure of a rotor according to embodiments of the present application.

[0025] Figure 3 is a schematic diagram of a partial structure of a rotor according to embodiments of the present application.

[0026] Figure 4 is a schematic diagram of a partial structure of a rotor according to embodiments of the present application.

[0027] Figure 5 is a comparison diagram of electromagnetic torque waveforms of a rotor assembly (with spacing between rotor units) according to embodiments of the present application and an existing motor (without spacing).

[0028] Figure 6 is a comparison diagram of cogging torque waveforms of a rotor assembly (with spacing between rotor units) according to embodiments of the present application and an existing motor (without spacing).

[0029] Figure 7 is a comparison diagram of cogging torque reduction principle vectors of a rotor assembly according to embodiments of the present application.

[0030] Figure 8 This is a vector diagram illustrating the principle of reducing cogging torque in a rotor assembly according to an embodiment of the present invention.

[0031] Figure 9 This is a vector diagram illustrating the principle of reducing cogging torque in a rotor assembly according to an embodiment of the present invention.

[0032] Figure 10 This is a comparison diagram of the electromagnetic torque waveforms of a rotor assembly (with a slant angle of 5.15° between rotor units) according to an embodiment of the present invention and a conventional motor (with an included angle of 5°).

[0033] Figure 11 This is a comparison diagram of the cogging torque waveforms of a rotor assembly (with a skew angle of 5.15° between rotor units) according to an embodiment of the present invention and a conventional motor (with an included angle of 5°).

[0034] Figure 12 This is a comparison diagram of the electromagnetic torque waveforms of a rotor assembly (with different minimum spacing between rotor units) according to an embodiment of the present invention and a conventional motor (with the same minimum spacing).

[0035] Figure 13 This is a comparison diagram of the cogging torque waveforms of a rotor assembly (with different minimum spacing between rotor units) according to an embodiment of the present invention and a conventional motor (with the same minimum spacing).

[0036] Figure 14 The rotor assembly (G) according to an embodiment of the present invention m / L r =0.12) and the rotor assembly (G) of the embodiment of the present invention m / L r Comparison of cogging torque waveforms (=0.26).

[0037] Figure 15 The rotor assembly according to embodiments of the present invention is at different Δθ m Electromagnetic torque and cogging torque at / θ0 and Δθ m A curve showing the ratio of electromagnetic torque to cogging torque when / θ0=0.

[0038] Figure 16 This is a graph showing the cogging torque of the rotor assembly under different Gm / Lr ratios and the ratio of cogging torque to Lr when Gm / Lr = 0, according to an embodiment of the present invention.

[0039] Figure label:

[0040] Motor 100;

[0041] Rotor assembly 10;

[0042] Rotor unit 1; Rotor core 11; Permanent magnet 12;

[0043] Air gap 2. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] like Figures 1-16 As shown, the rotor assembly 10 according to an embodiment of the present invention includes multiple rotor units 1, each rotor unit 1 including a rotor core 11 and multiple permanent magnets 12. The rotor core 11 has multiple magnet slots arranged circumferentially along the rotor core 11, and the permanent magnets 12 are disposed in the magnet slots, with the multiple permanent magnets 12 corresponding to the multiple magnet slots.

[0046] like Figure 1 and Figure 2 As shown, multiple rotor units 1 are spaced apart in the vertical direction to form a rotor, and multiple magnet slots are distributed circumferentially in the rotor core 11, with multiple permanent magnets 12 correspondingly assembled in the multiple magnet slots.

[0047] Multiple rotor units 1 are arranged at intervals along the axial direction of the rotor core 11. In other words, the rotor core of the rotor assembly 10 is divided into multiple segments along its axial direction, and each segment and its permanent magnet form a rotor unit 1, thus the rotor assembly 10 includes multiple rotor units 1 arranged at intervals along the axial direction of the rotor core 11. Figure 5 and Figure 6 As shown, the rotor assembly utilizes multiple rotor units 1 arranged at intervals to form multiple space intervals, effectively solving the problem of magnetic flux interaction between rotor units 1.

[0048] The m-th rotor unit 1 and the (m+1)-th rotor unit 1 are arranged adjacent to each other in the axial direction of the rotor core 11, and the minimum distance between the m-th rotor unit 1 and the (m+1)-th rotor unit 1 in the axial direction of the rotor core 11 is G. m , 0.01≤G m / L r ≤0.16, where L i Let L be the length of the i-th rotor unit along the axial direction of the rotor core, 1 ≤ i ≤ n, where n is the number of rotor units and n is a natural number greater than or equal to 2. In other words, L... r is the average length of rotor unit 1 along the axial direction of rotor core 11, where m is a natural number greater than or equal to 1.

[0049] For example, when m is 1, G m G represents the minimum axial spacing between the first rotor unit 1 and the second rotor unit 1 in the rotor core 11. When m is 3, Gm It is the minimum axial spacing between the third rotor unit 1 and the fourth rotor unit 1 in the rotor core 11.

[0050] The inventors discovered that when the interval G between rotor units 1 m With other dimensional parameters remaining essentially unchanged, the average length L of the multi-segment rotor unit 1 r The larger the diameter, the greater the cogging torque, and the higher the cost will be. The average length L of the multi-segment rotor unit 1... r When the length decreases, the electromagnetic torque also decreases, leading to a reduction in the performance of motor 100. When the average length L of the multi-segment rotor unit 1... r If other dimensional parameters remain essentially unchanged, if G m If the value of G is too small, meaning the interval between two adjacent rotor segments is too small, then the magnetic flux interaction between the two adjacent rotor segments will be significant, and the magnetic flux density distribution between the rotor segments will differ greatly. This will weaken the effect of using rotor segmentation with skewed poles to suppress cogging torque. If G m If the value is too large, that is, if the interval between two adjacent rotor segments is too large, then there is basically no magnetic flux interaction between the two adjacent rotor segments. This will lead to problems such as excessive axial length of rotor assembly 10, reduced torque density, increased winding loss, and reduced efficiency.

[0051] Combination Figure 14 As shown, in 0.01≤G m / L r Within the range ≤0.16, take G. m / L r The value is 0.12, compared to the value G outside the range. m / L r When the value is 0.26, the cogging torque of rotor assembly 10 is significantly lower.

[0052] Therefore, according to the rotor assembly of the present invention, by configuring the rotor into multiple spaced-apart rotor segments, and minimizing the distance G between two adjacent rotor segments... m The average length L of the multi-segment rotor unit in the axial direction of the rotor core r Satisfying 0.01≤G m / L r With a value ≤0.16, the problem of magnetic flux interaction between rotor units can be effectively solved without significantly changing the electromagnetic torque of the rotor assembly, thereby reducing the cogging torque of the rotor assembly, reducing mechanical vibration and noise, and improving the performance of the rotor assembly.

[0053] Preferably, 0.015≤G m / L r ≤0.07. For example... Figure 16As shown, Tcog* and Lr* are normalized values, Tcog* is the ratio of the cogging torque under different Gm / Lr to the cogging torque under Gm / Lr=0, and Lr* is the ratio of Lr under different Gm / Lr to Lr under Gm / Lr=0.

[0054] As shown in Figure 16 It can be seen that Lr* increases linearly with Gm / Lr; when 0.015≤Gm / Lr≤0.07, the cogging torque is greatly reduced and the change range is large, and when 0.07<Gm / Lr≤0.16, the cogging torque is still decreasing, but the change range is very small, so considering the increase in cost, Gm / Lr is controlled in the range of 0.015≤Gm / Lr≤0.07, which is more economical and has a higher cost performance.

[0055] In some embodiments, G m =G n-m , m≤n-1, G n-m is the minimum spacing of the n-mth rotor unit 1 and the n-m+1th rotor unit 1 in the axial direction of the rotor core 11. In this way, the motor stator core and the rotor core can be centrally symmetrical, and axial force can be avoided.

[0056] It can be understood that any two adjacent segments of the multi-segment rotor unit can form a spacing, i.e., the multi-segment rotor unit can form multiple spacings, and the minimum spacings of the multiple spacings can be equal or only partially equal.

[0057] For example, when the number of segments n of the rotor unit 1 is 5 and m=1, G1=G 5-1 =G4; when m=2, G2=G 5-2 =G3. It can be understood that when G1=G2, G1=G2=G3=G4 exists.

[0058] For another example, when G1≠G2, G1=G4≠G2=G3 exists.

[0059] As shown in Figure 10 and Figure 11 , when G m =G n-m , the cogging torque is significantly reduced without changing the electromagnetic torque. In this way, the cogging torque can be further reduced, and the optimization effect can be improved.

[0060] In some embodiments, as shown in Figure 4 , the skew angle of the mth rotor unit 1 and the m+1th rotor unit 1 is θ m , and θ m =θ0+Δθ m , θ0=360° / (n*N c ), and 0≤Δθm / θ0≤0.18, where m≤n - 1, Z1 is the number of stator slots, p is the number of pole pairs of the rotor assembly, and N c = LCM(Z1, 2p). In other words, N c is the least common multiple of Z1 and 2p.

[0061] As Figure 4 shown in the 12 - slot 8 - pole rotor assembly 10, the skewing angle of the first - stage rotor unit 1 and the second - stage rotor unit 1, for example, the included angle between the magnetic - pole center line L1 of the first - stage rotor unit 1 and the magnetic - pole center line L2 of the second - stage rotor unit 1 is θ1, and the skewing angle of the second - stage rotor unit 1 and the third - stage rotor unit 1, for example, the included angle between the magnetic - pole center line L2 of the second - stage rotor unit 1 and the magnetic - pole center line L3 of the third - stage rotor unit 1 is θ2.

[0062] It should be noted that the harmonics of the cogging torque of the Z1 - slot 2p - pole rotor assembly 10 are mainly of the N c = LCM(Z1, 2p) order. Therefore, for the 12 - slot 8 - pole rotor assembly 10, the harmonics of the cogging torque are mainly of the 24th order. As Figure 7 shown, S1, S2, and S3 are the cogging - torque components generated by the three - stage rotor cores 11. In theory, S1 = S2 = S3. Using the traditional included angle θ0 = 5° between the neutral lines of the permanent magnets 12 in two adjacent rotor units 1, the three are 120° out of phase with each other in space (θ0 * N c ), and the vector sum of S1 and S3 is S13. The total vector sum of S1, S2, and S3 is 0 (S2 - S13 = 0), that is, the 24th - order harmonic of the cogging torque can be completely eliminated.

[0063] The inventor found that due to the magnetic leakage at both ends of the rotor assembly 10, in the related art, increasing the axial length of the rotor is used to solve the problem of end - leakage magnetic flux. However, this method will cause the rotor to be too long, thereby increasing the length and cost of the motor.

[0064] Specifically, as Figure 8 shown, the cogging - torque component generated by the first - stage rotor core 11 is S1', and the cogging - torque component generated by the third - stage rotor core 11 is S3'. The vector sum of S3' and S1' is S13'. If the included angle θ0 = 5° between the neutral lines of the permanent magnets 12 in two adjacent rotor units 1, then S13' < S2, that is, the three cannot be completely eliminated.

[0065] Therefore, this application uses θ m = θ0+Δθ m , 0≤Δθ m / θ0≤0.18, in this scheme, the cogging torque component generated by the first rotor core 11 is S1''', the cogging torque component generated by the third rotor core 11 is S3''', and the vector sum of the two is S13''', at this time, compared with θ0=5°, S2-S13'''<S2-S13''', thus the synthesis of the three vectors can be effectively reduced, i.e. the harmonic of the uneliminated cogging torque is reduced, thereby effectively reducing the cogging torque.

[0066] As shown in Figure 10 and Figure 11 , when the angle between the neutral lines of the permanent magnets 12 in the adjacent two rotor units 1 is θ2=θ1=θ0+Δθ1=5.15° after optimization, the cogging torque can be greatly reduced on the basis of basically unchanged electromagnetic torque of the rotor assembly 10.

[0067] Preferably, 0<Δθ m / θ0≤0.12. As shown in Figure 15 , Tcog* and Te* are the normalized values, Tcog* is the ratio of the cogging torque under different Δθ m / θ0 to the cogging torque under the condition of Δθ m / θ0=0, and Te* is the ratio of the electromagnetic torque under different Δθ m / θ0 to the electromagnetic torque under the condition of Δθ m / θ0=0. From the above figure, when 0≤Δθ m / θ0≤0.18, with the increase of Δθ m / θ0, the cogging torque decreases, but the electromagnetic torque also decreases. Compared with the range of 0<Δθ m / θ0≤0.12, the change of the cogging torque in the range of 0.12<Δθ m / θ0≤0.18 is relatively flat, and considering the electromagnetic torque, the range of Δθ m / θ0 is controlled to 0<Δθ m / θ0≤0.12, which can effectively suppress the cogging torque on the basis of basically unchanged electromagnetic torque (within 1% decrease).

[0068] In some embodiments, θ m =θ n-m , where θ n-m is the skew angle of the n-mth rotor unit and the n-m+1th rotor unit. Thus, the symmetry of the motor is facilitated, and the consistency of the forward and reverse rotation performance is ensured.

[0069] It can be understood that the plurality of skew angles can be equal or only partially equal. For example, when the number of segments n of the rotor unit 1 is 5 and m=2, θ2=θ 5-2 =θ3; when m=1, θ1=θ 5-1= θ4. When θ1 = θ2, there is θ1 = θ2 = θ3 = θ4, that is, the skew pole angles of any two adjacent rotor units 1 are the same.

[0070] For another example, when θ1 ≠ θ2, there is θ1 = θ4 ≠ θ2 = θ3. Thus, the cogging torque can be further reduced and the optimization effect can be improved.

[0071] As Figure 9 shown, on the premise of not considering the end leakage flux, taking a three-segment skew pole rotor as an example, the cogging torque component generated by the first segment of rotor core is S1', the cogging torque component generated by the second segment of rotor core is S2, and the cogging torque component generated by the third segment of rotor core is S3'. Due to the flux interaction between rotor segments, θ1 < θ0 and θ2 < θ0, so S13' < S2, that is, the vectors of the three cannot be completely eliminated. From L1 = L3, we get S1' = S3', and the vector sum of the two:

[0072]

[0073] As G1 and G2 increase, θ1 and θ2 increase accordingly (tending to θ0), and S13' also increases, that is, the synthetic vector of S1', S2 and S13' is smaller, and the cogging torque is also smaller. From the above formula, when (θ1 + θ2) is a certain value, S13' is the largest when θ1 = θ2, that is, G1 = G2. It can be seen from this that satisfying Gm = Gn - m can suppress the cogging torque to a certain extent.

[0074] In some embodiments, L i = L n-i+1 where L n-i+1 is the length of the n - i + 1th rotor unit 1 in the axial direction of the rotor core. Thus, it further ensures the central symmetry of the motor stator core and rotor core and avoids generating axial force.

[0075] In some embodiments, as Figures 1-4 shown, between any two adjacent rotor units 1 in the rotor unit 1 is an air gap 2, or between any two adjacent rotor units 1 in multiple rotor units 1 are separated by a non-magnetic material.

[0076] Specifically, as Figure 5 and Figure 6 shown, compared with the existing rotor without the air gap 2 or this isolation section, the rotor in this embodiment can, without substantially changing the electromagnetic torque of the rotor assembly 10 (as Figure 5 shown), greatly reduce the cogging torque of the rotor assembly 10 (as Figure 6 shown), so as to further reduce the mechanical vibration and noise of the rotor assembly and further improve the performance of the rotor assembly.

[0077] Optionally, a portion of the rotor units 1 have an air gap 2 between adjacent rotor units 1, while another portion of the rotor units 1 are separated by a non-magnetic material between adjacent rotor units 1.

[0078] Furthermore, the air gap 2 and non-magnetic materials are arranged alternately along the axial direction of the rotor core 11. It can be understood that the air gap 2 and non-magnetic materials can be arranged alternately, or multiple air gaps can be grouped together, multiple non-magnetic materials can be grouped together, and a group of air gaps and a group of non-magnetic materials can alternate. Thus, while reducing the cogging torque of the rotor assembly, the reasonable arrangement of non-magnetic materials can save rotor assembly costs and improve rotor structural strength.

[0079] In some embodiments, the outer periphery of the non-magnetic material is located within the outer periphery of the rotor core 11, or flush with the outer periphery of the rotor core 11, in a projection plane orthogonal to the axial direction of the rotor core 11. In other words, the outer periphery of the non-magnetic material does not extend beyond the outer periphery of the rotor core 11. Therefore, the placement of the non-magnetic material does not affect the structural profile of the rotor, eliminating the need to increase the rotor's assembly space and avoiding rotor assembly interference.

[0080] The motor according to an embodiment of the present invention includes a rotor assembly 10 according to an embodiment of the present invention. By employing the rotor assembly described above, the rotor assembly has low vibration and low noise.

[0081] An electric vehicle according to an embodiment of the present invention includes an electric power steering system, the electric power steering system including the motor described in the above embodiment, and by using the above motor, the electric vehicle operates with low noise.

[0082] The following is for reference. Figures 1-16 A rotor assembly 10 according to a specific example of the present invention is described.

[0083] like Figures 1-4 As shown, the rotor assembly 10 includes three rotor units 1, which are spaced apart in the vertical direction. Each rotor unit 1 includes a rotor core 11 and 12 magnet slots arranged circumferentially along the rotor core 11. Each magnet slot is equipped with a permanent magnet 12.

[0084] The minimum distance between the first rotor unit 1 and the second rotor unit 1 is G1, and the minimum distance between the second rotor unit 1 and the third rotor unit 1 is G2, where G1 = G 3-1 G2 = G 3-2 That is, G1 = G2. The length of each rotor unit 1 is L. r 0.015≤G1 / L r ≤0.07, 0.015≤G2 / L r ≤0.07.

[0085] The skew pole angle of the first segment rotor unit 1 and the second segment rotor unit 1, for example, the included angle between the magnetic pole center line L1 of the first segment rotor unit 1 and the magnetic pole center line L2 of the second segment rotor unit 1 is θ1. The skew pole angle of the second segment rotor unit 1 and the third segment rotor unit 1, for example, the included angle between the magnetic pole center line L2 of the second segment rotor unit 1 and the magnetic pole center line L3 of the third segment rotor unit 1 is θ2, θ1 = θ 3-1 , θ2 = θ 3-2 , that is, θ1 = θ2.

[0086] The electric power steering device according to the embodiment of the application comprises the motor described above, and by adopting the motor described above, the electric power steering device has small vibration and low noise during operation.

[0087] A vehicle according to the embodiment of the application comprises the motor described above, and the vehicle can be a new energy vehicle, a fuel vehicle, etc., and the new energy vehicle includes a pure electric vehicle, a range-extended electric vehicle, a hybrid electric vehicle, a fuel cell electric vehicle, a hydrogen engine vehicle, etc., and by adopting the motor described above, the vehicle has small vibration and low noise during operation.

[0088] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0089] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0090] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", "fixedly connected", "connection", "fixedly connected", "connected", "fixed", and the like should be construed broadly, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be electrical connection or communication with each other; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0091] In the present application, unless specifically defined otherwise, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the first feature is higher than the second feature in horizontal height. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the first feature is lower than the second feature in horizontal height.

[0092] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification and the features of different embodiments or examples without contradiction.

[0093] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A rotor assembly, characterized in that, It includes multiple rotor units, each rotor unit comprising: The rotor core has a plurality of magnet slots arranged circumferentially along the rotor core. A plurality of permanent magnets are disposed within the magnet slots, and the plurality of permanent magnets correspond to the plurality of magnet slots. Multiple rotor segments are arranged at intervals along the axial direction of the rotor core. The m-th rotor segment and the (m+1)-th rotor segment are arranged adjacent to each other along the axial direction of the rotor core. The minimum axial distance between the m-th rotor segment and the (m+1)-th rotor segment is G. m , 0.01≤G m / L r ≤0.16, where L i Let be the length of the i-th rotor unit along the axial direction of the rotor core, 1≤i≤n, where n is the number of rotor units, and n is a natural number greater than or equal to 2, and m is a natural number greater than or equal to 1. The skew angle of the m-th rotor unit and the (m+1)-th rotor unit is θ. m , and θ m =θ0+Δθ m θ0 = 360° / (n*N) c ), 0≤Δθ m / θ0≤0.18, where m≤n-1, N c =LCM(Z1,2p), where Z1 is the number of stator slots and p is the number of motor pole pairs.

2. The rotor assembly according to claim 1, characterized in that, 0.015 ≤G m / L r ≤0.07。 3. The rotor assembly according to claim 1 or 2, characterized in that, G m =G n-m Where m≤n-1, G n-m The minimum axial spacing between the nm-th rotor unit and the (n-m+1)-th rotor unit in the rotor core.

4. The rotor assembly according to claim 1, characterized in that, 0<Δθ m / θ0≤0.12。 5. The rotor assembly according to claim 1, characterized in that, θ m =θ n-m , where θ n-m Let be the skew pole angle of the nm-th rotor unit and the (n-m+1)-th rotor unit.

6. The rotor assembly according to claim 1, characterized in that, L i =L n-i+1 L n-i+1 Let be the length of the (n-i+1)th rotor unit in the axial direction of the rotor core.

7. The rotor assembly according to claim 1, characterized in that, Any adjacent rotor units among the plurality of rotor units are separated by a non-magnetic material.

8. The rotor assembly according to claim 7, characterized in that, An air gap exists between any two adjacent rotor units in the plurality of rotor units.

9. The rotor assembly according to claim 1, characterized in that, In a plurality of rotor units, some of the rotor units are separated from each other by an air gap, while other rotor units are separated from each other by a non-magnetic material.

10. The rotor assembly according to claim 9, characterized in that, The air gap and the non-magnetic material are arranged alternately along the axial direction of the rotor core.

11. The rotor assembly according to any one of claims 7-10, characterized in that, In a projection plane orthogonal to the axial direction of the rotor core, the outer periphery of the non-magnetic material is located within the outer periphery of the rotor core, or the outer periphery of the non-magnetic material is flush with the outer periphery of the rotor core.

12. An electric motor, characterized in that, Includes the rotor assembly according to any one of claims 1-10.

13. An electric power steering device, characterized in that, Includes the motor according to claim 12.

14. A vehicle, characterized in that, Includes the motor according to claim 12.

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