Rotor assembly of an electric machine and electric machine comprising the same

Abstract

This disclosure provides a rotor assembly for an electric motor and an electric motor including the rotor assembly. The rotor assembly includes n pairs of core segments stacked sequentially in the axial direction. Each core segment has multiple rotor slots, each slot is inclined relative to the rotation axis of the rotor assembly, and the inclination directions of the multiple rotor slots in each core segment are the same. The inclination directions of the rotor slots in adjacent core segments are opposite. The rotor slots of each core segment form a circumferential offset angle in the circumferential direction of the rotor assembly. The circumferential offset angles of the multiple rotor slots in each core segment are the same. The absolute values ​​of the circumferential offset angles of the rotor slots of the two core segments in each pair are 360° / Z1 and 360° / Z2, respectively, where Z1 is the number of stator slots and Z2 is the number of rotor slots. Z1 and Z2 are not equal. By using a multi-segment hybrid skewed rotor structure with different skew angles in each segment, stator and rotor tooth harmonics can be effectively suppressed simultaneously, thereby avoiding high-frequency electromagnetic noise.

Description

Technical Field

[0001] This disclosure relates to the field of electric motor technology, and more specifically, to a rotor assembly of an electric motor and an electric motor comprising the rotor assembly. Background Technology

[0002] Existing motors use a 36 / 28 stator / rotor slot configuration, resulting in high cost and noise. To address this issue, a specific number of stator / rotor slot configurations are often employed to optimize electromagnetic performance. However, when optimizing the stator and rotor slot numbers to reduce the overall number of slots and increase the distributed winding factor, the selection of the rotor slot number is often constrained by a specific mathematical relationship: the number of rotor slots Z2 satisfies Z2 = 2pmk + 2p, where p is the number of pole pairs, m is the number of phases, and k is any integer. While this specific slot configuration can reduce higher harmonics and improve efficiency, it can also cause the first-order rotor harmonics to interact with the stator phase band harmonics, resulting in synchronous additional torque during motor operation.

[0003] The presence of synchronous additional torque makes the motor unstable during startup, prone to shaking or even jamming at low speeds, and significantly increases motor vibration and electromagnetic noise. Furthermore, traditional rotor skew slot designs typically use a single skew angle. While this single-angle design can reduce some harmonics, it is difficult to effectively suppress both stator and rotor tooth harmonics simultaneously, failing to fundamentally change the motor's resonance spectrum. This results in still high electromagnetic noise at high frequencies and cannot completely eliminate synchronous torque fluctuations caused by specific slot combinations.

[0004] Therefore, existing technologies lack a rotor structure design that can simultaneously achieve high efficiency, low cost, and effectively address synchronous additional torque and multi-source harmonic noise. Existing simple skewed or straight slot designs cannot simultaneously reduce stator tooth harmonics and suppress rotor tooth harmonics, nor can they flexibly adjust the structural design to offset the adverse effects of specific slot combinations. Therefore, there is an urgent need to improve the noise, vibration performance, and operational smoothness of motors. Summary of the Invention

[0005] To address at least one of the aforementioned problems, this disclosure provides a rotor assembly for an electric motor and an electric motor comprising the rotor assembly. By employing a multi-segment hybrid skewed rotor structure with segmented skewed slot angles, it solves the technical problems of low-speed vibration caused by synchronous additional torque in traditional motors with few slots and close engagement, high-frequency electromagnetic noise caused by the inability of a single skewed slot to effectively suppress stator and rotor tooth harmonics simultaneously, and the difficulty of balancing low additional losses and low cost in traditional designs.

[0006] According to one embodiment of this disclosure, a rotor assembly for an electric motor is provided. The rotor assembly includes n pairs of iron core segments stacked sequentially in the axial direction of the rotor assembly, where n is an integer greater than or equal to 2. Each iron core segment has a plurality of rotor slots extending along the axial direction. Each rotor slot is inclined relative to the rotation axis of the rotor assembly, and the inclination directions of the plurality of rotor slots in each iron core segment are the same. The inclination directions of the rotor slots in adjacent iron core segments are opposite, so that the rotor assembly as a whole forms a zigzag inclined slot structure. Each iron core segment has a first end face and a second end face, and both the first end face and the second end face are perpendicular to the rotor assembly. The rotor slots of each core segment have a first slot center on the first end face of the core segment and a second slot center on the second end face of the core segment. The first connecting line between the first slot center and the first axis of rotation and the second connecting line between the second slot center and the second axis of rotation form a circumferential offset angle in the circumferential direction of the rotor assembly. The circumferential offset angles of the multiple rotor slots of each core segment are the same as each other. The absolute values ​​of the circumferential offset angles of the rotor slots of the two core segments of each core segment pair are 360° / Z1 and 360° / Z2, respectively, where Z1 is the number of stator slots of the motor and Z2 is the number of rotor slots. Z1 and Z2 are not equal.

[0007] By employing a zigzag-shaped skewed slot structure, the manufacturing complexity associated with continuous spiral skewed slots is avoided, reducing processing difficulty and cost. A multi-segment hybrid skewed slot design is achieved by setting the circumferential offset angles of the core segments to the absolute values ​​of the stator slot pitch angle (360° / Z1) and the rotor slot pitch angle (360° / Z2), respectively. This specific angle combination effectively weakens stator tooth harmonics (such as the 23rd and 25th harmonics under a 48 / 40 fit) and rotor tooth harmonics (such as the 19th and 21st harmonics), while altering the motor's resonance spectrum, thereby significantly reducing electromagnetic noise and vibration. Furthermore, this structure disrupts the harmonic coupling conditions that generate synchronous additional torque, eliminating unstable motor starting and low-speed vibration.

[0008] Furthermore, the second end face of one of the adjacent iron core segments fits into the first end face of another adjacent iron core segment to form a mating end face. The line connecting the center of the second slot of the rotor slot of one iron core segment and the axis of rotation on the mating end face and the line connecting the center of the first slot of the rotor slot of another iron core segment and the axis of rotation on the mating end face form a preset inter-segment misalignment angle in the circumferential direction.

[0009] By creating a preset inter-segment misalignment angle at the mating end faces of adjacent core segments, the control over the air gap permeability distribution is further refined. This misalignment can more accurately counteract the tooth harmonic magnetic field caused by the slotting of the stator and rotor, especially for high-frequency harmonic components. This reduces additional losses while further optimizing the motor's noise, vibration, and acoustic roughness performance, ensuring the motor's smoothness during high-speed operation.

[0010] Furthermore, the inter-segment misalignment angle is equal to 360° / 2Z2.

[0011] By limiting the inter-segment misalignment angle to 360° / 2Z2 (i.e., half of the rotor slot pitch angle), it is possible to maximize the use of the phase difference between adjacent core segments to cancel out specific order tooth harmonics. In particular, for a 40-slot rotor, this misalignment angle helps to homogenize the radial magnetic pull, reduce vibration caused by unilateral magnetic pull, and maintain low transverse eddy current losses.

[0012] Furthermore, the n core segments define a virtual symmetry plane perpendicular to the axis of rotation at the center of the rotor assembly in the axial direction. The absolute values ​​of the circumferential offset angles of the rotor slots of the two core segments located on both sides of the virtual symmetry plane and in mirror-symmetric positions are the same or different.

[0013] By introducing a virtual symmetry plane and making the core segments at mirror-symmetrical positions have a specific circumferential offset angle relationship, this symmetrical structural design helps to balance the radial electromagnetic force experienced by the rotor assembly during rotation, thereby reducing mechanical vibration and noise caused by magnetic pull imbalance and improving the smoothness and lifespan of motor operation.

[0014] Furthermore, the rotor assembly includes a first core segment pair and a second core segment pair stacked sequentially in the axial direction of the rotor assembly. The absolute value of the circumferential offset angle of the rotor slot of the core segment closer to the virtual symmetry plane in the first core segment pair is equal to the absolute value of the circumferential offset angle of the rotor slot of the core segment closer to the virtual symmetry plane in the second core segment pair, and the absolute value of the circumferential offset angle of the rotor slot of the core segment farther from the virtual symmetry plane in the first core segment pair is equal to the absolute value of the circumferential offset angle of the rotor slot of the core segment farther from the virtual symmetry plane in the second core segment pair.

[0015] This configuration can more effectively cover the harmonic suppression requirements of a wide frequency band. In particular, with the 48 / 40 slot combination, it can simultaneously optimize the harmonic attenuation effect on both the stator and rotor sides, achieving the best balance between low noise and high efficiency.

[0016] Furthermore, the absolute value of the circumferential offset angle of the rotor slot of the core segment away from the virtual symmetry plane in the first core segment pair and the absolute value of the circumferential offset angle of the rotor slot of the core segment away from the virtual symmetry plane in the second core segment pair are 360° / Z1, and the absolute value of the circumferential offset angle of the rotor slot of the core segment close to the virtual symmetry plane in the first core segment pair and the absolute value of the circumferential offset angle of the rotor slot of the core segment close to the virtual symmetry plane in the second core segment pair are 360° / Z2.

[0017] By specifically limiting the offset angle of the outer core section to 360° / Z1 and the offset angle of the inner core section near the symmetry plane to 360° / Z2, the winding coefficient of each tooth harmonic on the stator and rotor sides can be reduced more significantly than that of a single skewed slot. This reduces additional losses while maximizing motor efficiency and suppressing electromagnetic noise.

[0018] Furthermore, each of the n core segment pairs includes a preceding core segment and a following core segment stacked sequentially in the axial direction. In each core segment pair, the absolute value of the circumferential offset angle of the rotor slot of the preceding core segment is 360° / Z1, and the absolute value of the circumferential offset angle of the rotor slot of the following core segment is 360° / Z2.

[0019] For rotor assemblies containing multiple core segments, the application of zigzag slots is expanded by repeating the alternating arrangement of "stator slot pitch angle - rotor slot pitch angle". This structure can also achieve mutual cancellation of harmonics and suppression of synchronous additional torque, while maintaining structural symmetry and magnetic pull balance, providing flexibility for motor designs with different axial lengths.

[0020] Furthermore, Z1 equals 48, and Z2 equals 40.

[0021] The number of slots is specifically limited to a 48 / 40 fit, which has a small slot pitch angle. Combined with the zigzag inclined slot structure disclosed herein, it can significantly reduce the harmonic coefficient and tooth harmonics of the distributed winding. Actual test data shows that it can effectively reduce additional losses (e.g., from 248W to 138W) and improve efficiency, while solving the synchronous torque problem unique to 40 slots.

[0022] Furthermore, the rotor slots are closed slots.

[0023] According to another aspect of this disclosure, an electric motor is provided, comprising: a stator assembly; and a rotor assembly disposed inside the stator assembly, wherein the rotor assembly is the rotor assembly of the aforementioned electric motor.

[0024] This motor integrates all the technological advantages of the aforementioned rotor components, including low noise, low vibration, high efficiency, low additional losses, and no synchronous additional torque jitter. At the same time, due to the adoption of a few slots close fit and an optimized skewed slot structure, material costs and manufacturing complexity are reduced.

[0025] Furthermore, the motor is a 4-pole motor.

[0026] Furthermore, the stator assembly has Z1 stator slots evenly distributed along the circumference; the rotor assembly has Z2 rotor slots evenly distributed along the circumference; the stator slot pitch angle is 360° / Z1, the rotor slot pitch angle is 360° / Z2, and the ratio of the rotor slot pitch angle to the stator slot pitch angle is 1.2.

[0027] By limiting the ratio of rotor slot pitch angle to stator slot pitch angle to 1.2 (i.e., Z1 / Z2 = 1.2, corresponding to 48 / 40), combined with the polygonal skew slot structure, it is possible to effectively suppress specific harmonics (such as 19th, 21st, 23rd, and 25th), ensuring the accuracy and repeatability of electromagnetic design, thereby stably achieving low noise and high efficiency.

[0028] This disclosure provides a rotor assembly for an electric motor and an electric motor including the rotor assembly. Electromagnetic performance optimization is achieved through a specific number (48 / 40) of slots combined with a multi-segment hybrid zigzag slot structure. The near-perfect fit between fewer stator and rotor slots (e.g., 48 stator slots and 40 rotor slots) reduces the distributed winding harmonic coefficient and rotor resistance, significantly reducing additional losses. Multiple core segments are stacked sequentially in the axial direction, with adjacent segments tilting in opposite directions to form a zigzag slot. The circumferential offset angle of some segments is the stator slot distance angle (360° / Z1), while the other... The circumferential offset angle of some sections is the rotor slot pitch angle (360° / Z2), which effectively weakens stator tooth harmonics (e.g., 23rd and 25th) and rotor tooth harmonics (e.g., 19th and 21st), changes the motor resonance spectrum, and eliminates low-speed jitter caused by synchronous additional torque; the inter-segment misalignment angle is set to 360° / 2Z2, which further cancels high-frequency harmonic vibrations and ensures smooth and low-noise motor operation; this structure does not require additional damping rings or complex continuous skew slot processes, maintains manufacturing feasibility, and saves material costs while improving energy efficiency (reducing copper weight and losses). Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this disclosure, illustrate exemplary embodiments of the present disclosure and are used to explain the disclosure, but do not constitute an undue limitation of the disclosure. In the drawings: Figure 1 A partial cross-sectional view of the structure of an electric motor according to an embodiment of the present disclosure is shown.

[0030] Figure 2 An exploded three-dimensional view of the structure of a rotor assembly of an electric motor according to an embodiment of the present disclosure is shown.

[0031] Figure 3 A schematic diagram showing the unfolded rotor assembly of an electric motor according to an embodiment of the present disclosure is provided.

[0032] Figure 4 Another schematic diagram showing the unfolded rotor assembly of an electric motor according to an embodiment of the present disclosure is shown.

[0033] Figure 5 A schematic diagram showing the unfolded rotor assembly of an electric motor according to another embodiment of the present disclosure is shown.

[0034] Explanation of icon numbers: 1. Stator assembly 11 Stator Core 12 stator slots 2 Rotor Assembly 21 Rotor core 22 Rotor slots 21-1 First Core Section 21-1a First end face of the first core section 21-1b Second end face of the first core section 22-1 First Rotor Slot 21-2 Second core section 21-2a First end face of the second core section 21-2b Second end face of the second core section 22-2 Second rotor slot 21-3 Third core section 21-3a First end face of the third core section 21-3b The second end face of the third core section 22-3 Third rotor slot 21-4 Fourth core section 21-4a First end face of the fourth core section 21-4b The second end face of the fourth core section 22-4 Fourth rotor slot 21-5 Fifth core section 22-5 Fifth rotor slot 21-6 Sixth core section 22-6 Sixth rotor slot C1 First slot center C2 Second slot center Detailed Implementation

[0035] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, and not all of them. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such signals can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, including a series of steps or units, a method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0037] As discussed in the background section, in order to reduce costs and suppress high-order harmonics, a specific number of stator and rotor slot combinations are often used in existing motors. However, this slot combination results in the number of rotor slots meeting specific synchronization conditions, causing the first-order tooth harmonics of the rotor to interact with the phase band harmonics of the stator to generate synchronous additional torque, leading to unstable motor starting and low-speed vibration. At the same time, traditional single skewed slot or straight slot designs are difficult to effectively suppress stator and rotor tooth harmonics simultaneously, resulting in high electromagnetic noise.

[0038] To address this, this disclosure provides a rotor assembly for an electric motor. This rotor assembly employs a segmented, zigzag-slot structure design. By setting the circumferential offset angles of each core segment (corresponding to the stator slot pitch angle and rotor slot pitch angle, respectively) and the inter-segment misalignment angles, active optimization of rotor magnetic field harmonics is achieved without altering the motor's basic topology. Even if there is a risk of synchronous torque in the stator-rotor slot fit, automatic "correction" and cancellation of electromagnetic harmonics can be achieved through specific angle combinations (e.g., a mixed distribution of a rotor slot pitch angle and a stator slot pitch angle), thereby ensuring smooth operation of the motor at low speeds and during startup. The rotor assembly of this disclosed motor can achieve electromagnetic performance optimization for the limited slot fit characteristics of the stator and rotor without adding additional mechanical components.

[0039] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0040] like Figure 1 As shown, Figure 1A partial cross-sectional view of the structure of an electric motor according to an embodiment of the present disclosure is shown. The motor may include a stator assembly 1 and a rotor assembly 2 disposed inside the stator assembly 1. The stator assembly 1 may include a stator core 11 and stator slots 12 uniformly spaced circumferentially in the stator core 11. The rotor assembly 2 may be disposed inside the stator assembly 1 and may have an air gap fit with the stator assembly 1. The rotor assembly 2 may extend axially and rotate about a rotation axis. The rotor assembly 2 may include a rotor core 21 and rotor slots 22 uniformly spaced circumferentially in the rotor core 21.

[0041] In this embodiment, the stator slot number Z1 is described as 48 and the rotor slot number Z2 as 40, with Z1 / Z2=1.2. However, this disclosure is not limited to this specific slot combination, but the technology of this disclosure can also be applied to motors with other slot combinations.

[0042] In a motor with this slot fit structure, the stator slot pitch angle θ1 is 360° / Z1=7.5°, corresponding to one stator tooth; the rotor slot pitch angle θ2 is 360° / Z2=9°, corresponding to one rotor tooth, and the relative position ratio between the rotor slot and the stator slot is 9 / 7.5=1.2.

[0043] Among the factors affecting the harmonic losses of a motor, the selection of the number of winding slots influences the distribution coefficient of the motor winding, k_dv = distribution coefficient = sin(v·q·α / 2) / [q·sin(v·α / 2)], where v: harmonic order; q: number of slots per pole per phase; α: slot pitch angle = 2πp / Z. Therefore, the phase harmonic coefficients of the 48 / 40 slot winding are shown in Table 1 below.

[0044] Table 1:

[0045] As can be seen, when the motor uses a 48 / 40 slot configuration, the higher harmonic coefficients are significantly reduced, the motor waveform is close to a sine wave, and the motor loss is low with high efficiency. If the formula Z2=2 is satisfied... p m k+2p, where k is any integer, the first-order harmonic of the rotor interacts with the phase band harmonic of the stator, generating a synchronous additional torque during motor operation. When the number of rotor slots is 40, due to 2... p m k + 2p = 2 2 3 3+4=40, which is equal to the number of rotor slots Z2 (40). Therefore, the interaction between the rotor first-order tooth harmonics and the stator phase band harmonics will generate synchronous additional torque, resulting in unstable motor starting, shaking at low speeds, and even jamming. The noise and vibration of the motor will increase significantly. In addition, the stator and rotor tooth harmonics have a huge impact on the noise and vibration of the motor.

[0046] Therefore, in the embodiments of this disclosure, the inventors of this disclosure have discovered that by adopting a multi-segment skewed rotor structure for the rotor assembly of the motor, such as a four-segment rotor assembly, it is possible to design two segments skewed by the angle of one stator tooth (i.e., stator slot pitch angle) and two segments skewed by the angle of one rotor tooth (i.e., rotor slot pitch angle), with each skewed slot rotating by half the rotor slot pitch angle, which can reduce both stator tooth harmonics and rotor tooth harmonics.

[0047] Therefore, in the embodiments of this disclosure, the rotor assembly 2 can adopt a segmented structure to solve problems such as synchronous additional torque and high-frequency electromagnetic noise generated by existing motors under specific slot combinations.

[0048] like Figure 2 As shown, Figure 2 A three-dimensional exploded view of the structure of a rotor assembly of an electric motor according to an embodiment of the present disclosure is shown. The rotor assembly 2 may include n pairs of iron core segments stacked sequentially in the axial direction of the rotor assembly 2, where n is an integer greater than or equal to 2.

[0049] like Figure 2 As shown, this embodiment takes n=2 as an example. Therefore, in this example, the rotor assembly 2 may include two pairs of iron core segments stacked sequentially along the axial direction, that is, four iron core segments stacked sequentially along the axial direction: first iron core segment 21-1, second iron core segment 21-2, third iron core segment 21-3 and fourth iron core segment 21-4. The first iron core segment 21-1 and the second iron core segment 21-2 can form a first iron core segment pair, and the third iron core segment 21-3 and the fourth iron core segment 21-4 can form a second iron core segment pair.

[0050] These four core segments (first core segment 21-1, second core segment 21-2, third core segment 21-3, and fourth core segment 21-4) together constitute the main body of the rotor assembly 2. Each core segment has multiple rotor slots 22 that extend along the axial direction and are evenly distributed along the circumference.

[0051] Specifically, such as Figure 2 and Figure 3As shown, a plurality of first rotor slots 22-1 can be formed on the first iron core section 21-1, a plurality of second rotor slots 22-2 can be formed on the second iron core section 21-2, a plurality of third rotor slots 22-3 can be formed on the third iron core section 21-3, and a plurality of fourth rotor slots 22-4 can be formed on the fourth iron core section 21-4. In the following, without distinguishing between rotor slots, the first rotor slot to the fourth rotor slot can be collectively referred to as rotor slots. If it is necessary to describe the first rotor slot to the fourth rotor slot separately, they will be described as first rotor slot to fourth rotor slot respectively to make this disclosure clearer.

[0052] like Figure 2 and Figure 3 As shown, the rotor slots on each of the first core segment 21-1, the second core segment 21-2, the third core segment 21-3, and the fourth core segment 21-4 are inclined relative to the rotation axis of the rotor assembly 2, and the multiple rotor slots of each core segment are inclined in the same direction. The rotor slots of adjacent core segments are inclined in opposite directions, so that the rotor assembly 2 as a whole forms a broken-line inclined slot structure.

[0053] More specifically, the first rotor slot 22-1 of the first core segment 21-1 and the second rotor slot 22-2 of the second core segment 21-2 can form an approximate herringbone shape, the second rotor slot 22-2 of the second core segment 21-2 and the third rotor slot 22-3 of the third core segment 21-3 can form an approximate herringbone shape, and the third rotor slot 22-3 of the third core segment 21-3 and the fourth rotor slot 22-4 of the fourth core segment 21-4 can form an approximate herringbone shape.

[0054] More specifically, the first core segment 21-1 may have opposing first end faces 21-1a and 21-1b, both of which are perpendicular to the rotation axis of the rotor assembly 2. Similarly, the second core segment 21-2 may have opposing first end faces 21-2a and 21-2b, both of which are perpendicular to the rotation axis of the rotor assembly 2; the third core segment 21-3 may have opposing first end faces 21-3a and 21-3b, both of which are perpendicular to the rotation axis of the rotor assembly 2; and the fourth core segment 21-4 may have opposing first end faces 21-4a and 21-4b, both of which are perpendicular to the rotation axis of the rotor assembly 2.

[0055] To more clearly describe the skewed slot structure, the circumferential offset angle of the rotor slot for each core segment is defined. For example... Figure 3As shown, for any core segment (e.g., the first core segment 21-1), its rotor slot (e.g., the first rotor slot 22-1) has a first slot center C1 on a first end face (e.g., 21-1a) and a second slot center C2 on a second end face (e.g., 21-1b). The first line connecting the first slot center C1 to the axis of rotation and the second line connecting the second slot center C2 to the axis of rotation form an angle in the circumferential direction of the rotor assembly 2, which is the circumferential offset angle. The circumferential offset angles of the multiple rotor slots 22 of each core segment are the same.

[0056] As described above, the first core segment 21-1 and the second core segment 21-2 can form a first core segment pair, and the third core segment 21-3 and the fourth core segment 21-4 can form a second core segment pair. In this embodiment, the absolute value of the circumferential offset angle of the rotor slot of the first core segment 21-1 is 360° / Z1 = 7.5°, and the absolute value of the circumferential offset angle of the rotor slot of the second core segment 21-2 is 360° / Z2 = 9°, where Z1 is the number of stator slots of the motor and Z2 is the number of rotor slots. The absolute value of the circumferential offset angle of the rotor slot of the fourth core segment 21-4 is 360° / Z1 = 7.5°, and the absolute value of the circumferential offset angle of the rotor slot of the third core segment 21-3 is 360° / Z2 = 9°. Figure 4 As shown, γ1 indicates 360° / Z1=7.5°, and γ2 indicates 360° / Z2=9°.

[0057] Additionally or alternatively, the slot skew electrical angles of the rotor slots in the first core section 21-1 and the second core section 21-2 can be respectively and Where p is the number of pole pairs of the motor, this also applies to the third core section 21-3 and the fourth core section 21-4. The configuration is a skewed slot electrical angle of... The iron core section, with its skewed slot electrical angle corresponding to one stator slot pitch electrical angle, can completely cancel the spatial magnetic field harmonics caused by stator slotting through axial integration effect, thus weakening the cogging torque of the motor; simultaneously, it is configured with a skewed slot electrical angle of... The iron core section has a skewed slot angle that corresponds to a rotor slot pitch electrical angle, which can completely cancel out specific order spatial harmonics caused by rotor side (such as rotor slotting) and greatly weaken the radial electromagnetic force waves that cause high-frequency resonance of the motor.

[0058] like Figure 2 and Figure 3As shown, two adjacent core segments are connected by end-face contact. Specifically, the second end face of one core segment is contacted with the first end face of the adjacent core segment to form a mating end face. For example, the second end face 21-1b of the first core segment 21-1 is contacted with the first end face 21-2a of the second core segment 21-2. There is an angular jump at the mating end face between the first core segment 21-1 and the second core segment 21-2. The inclination angle of the rotor slot of the first core segment 21-1 is +7.5°, and the inclination angle of the rotor slot of the second core segment 21-2 is -9.0° (opposite directions, different absolute values).

[0059] On the mating end face, the line connecting the center C2 of the second slot of the rotor slot of the third core segment 21-3 to the rotation axis and the line connecting the center C1 of the first slot of the rotor slot of the fourth core segment 21-4 to the rotation axis form a preset inter-segment misalignment angle α in the circumferential direction (e.g., ...). Figure 3 As shown in the figure, the skew slots of each core segment rotate by a certain angle. Preferably, the skew slots of each core segment rotate by half the rotor slot pitch angle, that is, the inter-segment misalignment angle α can be half the rotor slot pitch angle. In this example, the inter-segment misalignment angle can be 4.5°.

[0060] By creating such an inter-segment misalignment angle, the magnetic pull between adjacent iron core segments can be balanced, achieving specific harmonic cancellation.

[0061] Therefore, in the example of this embodiment, the rotor assembly 2 adopts a multi-segment structure, and the rotor slots of the two core segments of each core segment are inclined by the degree of one stator tooth and one rotor tooth, respectively.

[0062] Therefore, in the example of this embodiment, at the mating surface, the inclined rotor slots, together with the slight circumferential misalignment, can effectively reduce the rotor tooth harmonic order, improve motor efficiency, avoid the generation of synchronous additional torque, and reduce electromagnetic noise caused by stator tooth harmonics, as detailed below.

[0063] The equivalent skew coefficient of this structure , in, For the angle of the inclined groove, , This is the distance of the inclined groove. For polar distance, Tooth harmonic number Where Z1 is the number of stator slots, p is the number of pole pairs, and k = 1, 2, 3, ...

[0064] According to the example of this embodiment, the stator and rotor slots of the motor are matched in a 48 / 40 ratio. Therefore, the stator tooth harmonics are v=48 / 2±1=23 and 25, respectively, and the rotor tooth harmonics are v=40 / 2±1=19 and 21, respectively.

[0065] For the 19th harmonic of the rotor teeth (v=19), the slot coefficient k_sk19=0.148591776; For the 21st harmonic of the rotor teeth (v=21), the slot coefficient k_sk21=0.093318544; For the 23rd harmonic of the stator teeth (v=23), the slot coefficient k_sk23=0.08450739; For the 25th harmonic of the stator teeth (v=25), the slot coefficient k_sk25=0.109974565.

[0066] Table 2 summarizes examples of embodiments of this disclosure and the sloping groove coefficients of related technologies.

[0067] Table 2:

[0068] As can be seen from Table 2 above, the four-segment hybrid structure of the rotor assembly 2 in the example of the present disclosure can more effectively reduce stator tooth harmonics and rotor tooth harmonics simultaneously.

[0069] Furthermore, this structural design also aims to address the issue of synchronous additional torque. Since Z2=40 satisfies Z2 = 2pmk +2p (where p=2, m=3, k=3), the interaction between the rotor first-order tooth harmonics and the stator phase band harmonics generates synchronous additional torque, leading to unstable motor starting, low-speed vibration, and even jamming. This significantly increases motor noise and vibration. Additionally, the harmonics of the stator and rotor teeth have a substantial impact on motor noise and vibration. By employing the aforementioned specific multi-segment skewed slot structure, with two segments skewed by the angle of one stator tooth and two segments skewed by the angle of one rotor tooth, and each skewed slot rotating by half the angle of one rotor slot, the distribution of air gap permeability is altered. This disrupts the harmonic components that generate synchronous additional torque, weakening both stator and rotor tooth harmonics, thereby eliminating unstable motor starting and low-speed vibration.

[0070] Furthermore, in this embodiment, assuming that the virtual symmetry plane of the rotor assembly 2, perpendicular to the axis of rotation, is located between the second and third core segments, the absolute values ​​of the circumferential offset angles of the rotor slots of the two core segments (e.g., the first and fourth core segments) located on both sides of the virtual symmetry plane and in mirror-symmetrical positions are the same. Similarly, the absolute values ​​of the circumferential offset angles of the rotor slots of the second and third core segments are the same. This symmetrical structure can further balance the radial magnetic pull, helping to reduce unilateral magnetic pull and lower vibration.

[0071] In this embodiment, the rotor slot 22 can be a closed slot. Closed slots have a smaller tooth tip width, which can increase the magnetic reluctance between the stator and rotor, further weaken the harmonic electromotive force, and reduce additional losses and noise.

[0072] The example motor in this embodiment is a 4-pole motor, i.e., the number of pole pairs p=2. The ratio of the rotor slot pitch angle to the stator slot pitch angle is 9.0 / 7.5 = 1.2. By adopting a close fit with fewer slots, the distributed winding coefficient can be increased, thereby effectively reducing the high-order harmonics of the motor.

[0073] In summary, this embodiment, by employing a 48 / 40 slotted near-fit design combined with a four-segment hybrid zigzag-slot rotor (two 7.5° and two 9.0° segments, symmetrically distributed), achieves the following technical effects: it reduces high-order harmonic coefficients, increases the distributed winding coefficient, makes the motor waveform closer to a sine wave, reduces copper and iron losses, and improves efficiency (tests show efficiency increased to 94.24%); through a specific combination of zigzag slot angles, it effectively weakens stator tooth harmonics (23rd and 25th) and rotor tooth harmonics (19th and 21st), significantly reducing electromagnetic noise; and through the zigzag slot design, it suppresses the synchronous additional torque caused by the 40 slots, solving the problems of low-speed motor vibration and starting difficulties.

[0074] Furthermore, the structure of the motor in this embodiment reduces material costs (copper weight from 21.8 kg to 16.8 kg) and additional losses (from 248 W to 138 W) compared to the conventional 36 / 28 slot configuration.

[0075] As shown in Table 3 below:

[0076] Furthermore, the rotor assembly of this disclosure, in which 2n core segments are stacked sequentially in the axial direction, can be tilted sequentially at angles of 360° / Z1, 360° / Z2, 360° / Z1, and 360° / Z2. That is, each pair of n core segments includes a preceding core segment and a following core segment stacked sequentially in the axial direction. In each core segment pair, the absolute value of the circumferential offset angle of the rotor slot of the preceding core segment is 360° / Z1, and the absolute value of the circumferential offset angle of the rotor slot of the following core segment is 360° / Z2. (Refer to the following...) Figure 5 This embodiment of the rotor assembly of the present disclosure is described.

[0077] The following will be referenced Figure 5 Describes a rotor assembly of an electric motor according to another embodiment of the present disclosure, wherein, Figure 5 A schematic diagram showing the unfolded rotor assembly of an electric motor according to another embodiment of the present disclosure is shown. Figure 5 The rotor assembly of the motor in another embodiment shown is with Figure 3The difference in the rotor assembly of the motor shown is that, Figure 5 The rotor assembly 2 shown is divided into 6 segments, namely, three pairs of iron core segments stacked sequentially along the axial direction: first iron core segment 21-1, second iron core segment 21-2, third iron core segment 21-3, fourth iron core segment 21-4, fifth iron core segment 21-5, and sixth iron core segment 21-6. The first iron core segment 21-1 and the second iron core segment 21-2 form the first iron core segment pair; the third iron core segment 21-3 and the fourth iron core segment 21-4 form the second iron core segment pair; and the fifth iron core segment 21-5 and the sixth iron core segment 21-6 form the third iron core segment pair. In the first iron core segment pair, the absolute value of the circumferential offset angle of the first rotor slot 22-1 of the first iron core segment 21-1 is 360° / Z1 = The absolute value of the circumferential offset angle of the second rotor slot 22-2 of the second core segment 21-2 is 360° / Z2=9 degrees. Similarly, in the second core segment pair, the absolute value of the circumferential offset angle of the third rotor slot 22-3 of the third core segment 21-3 is 360° / Z1=7.5 degrees, and the absolute value of the circumferential offset angle of the fourth rotor slot 22-4 of the fourth core segment 21-4 is 360° / Z2=9 degrees. In the third core segment pair, the absolute value of the circumferential offset angle of the fifth rotor slot 22-5 of the fifth core segment 21-5 is 360° / Z1=7.5 degrees, and the absolute value of the circumferential offset angle of the sixth rotor slot 22-6 of the sixth core segment 21-6 is 360° / Z2=9 degrees.

[0078] This implementation further extends the effective skewed slot length and enhances the bandwidth and depth of harmonic suppression by setting multiple (e.g., six) iron core segments (three pairs of iron core segments) and alternating circumferential offsets of stator slot pitch angle (7.5°) and rotor slot pitch angle (9°). This multi-segment zigzag skewed slot structure can more evenly distribute the air gap magnetic flux density, which not only effectively weakens the main stator tooth harmonics (23rd and 25th) and rotor tooth harmonics (19th and 21st), but also further smooths the radial electromagnetic pull through multiple phase reversals, thereby significantly reducing the vibration and noise levels of the motor at high speeds.

[0079] The above is a schematic example of a rotor assembly of an electric motor according to this embodiment, but this disclosure is not limited thereto. For example, the iron core of the rotor assembly can be divided into 8 segments according to actual needs. The configuration structure of the rotor slots of the 8-segment iron core segment can be similar to the configuration structure of the rotor slots of the 4-segment iron core segment described above. Those skilled in the art can easily conceive of the configuration structure of the rotor slots of the 8-segment iron core segment based on the 4-segment structure provided in this disclosure, and will not be elaborated here.

[0080] In addition, an eight-segment core (four pairs of core segments) structure can be set up and the stator slot pitch angle (7.5°) and rotor slot pitch angle (9°) can be alternately used in a circumferentially offset structure.

[0081] The motor according to this disclosure has at least the following advantages: 1. Reduce electromagnetic noise and vibration, and optimize operational stability. By reducing the harmonic coefficient of the distributed winding by using a specific number of stator slots (e.g., 48 slots) and combining it with a multi-segment skewed rotor structure (skewed one stator tooth and one rotor tooth respectively), the stator tooth harmonics (v=23, 25) and rotor tooth harmonics (v=19, 21) are effectively weakened, and the resonant spectrum of the motor is changed. At the same time, the problem of synchronous additional torque caused by slot matching is solved, thereby significantly reducing the electromagnetic noise, vibration and low-speed jitter of the motor.

[0082] 2. Improve energy efficiency and reduce various losses.

[0083] By employing designs such as a 48 / 40 stator / rotor close-fitting configuration with fewer slots and a specific number of rotor slots, rotor resistance, lateral eddy current losses, and additional losses are reduced. Combined with the harmonic suppression effect of multiple skewed slots, motor operating losses are reduced, thereby improving the overall efficiency of the motor.

[0084] 3. Save manufacturing costs

[0085] By using a low-slot, close-fitting design and an optimized rotor structure, the amount of materials such as copper is reduced (saving motor costs), achieving high performance (low noise, high efficiency) while lowering manufacturing costs.

[0086] In the above embodiments of this disclosure, the descriptions of each embodiment have their own emphasis. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0087] In the several embodiments provided in this disclosure, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection between the units shown or discussed may be through some interfaces, and the indirect coupling or communication connection between units may be electrical or other forms.

[0088] The above are merely preferred embodiments of this disclosure. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure.

Claims

1. A rotor assembly for an electric motor, characterized in that, The rotor assembly comprises n pairs of core segments stacked sequentially along the axial direction of the rotor assembly, where n is an integer greater than or equal to 2. Each core segment has multiple rotor slots extending along the axial direction. Each rotor slot is inclined relative to the rotation axis of the rotor assembly, and the inclination directions of the multiple rotor slots in each core segment are the same. The inclination directions of the rotor slots in adjacent core segments are opposite, so that the rotor assembly as a whole forms a polygonal inclined slot structure. Each core segment has a first end face and a second end face, both of which are perpendicular to the rotation axis of the rotor assembly. Each core segment's rotor slot has a first slot center on the first end face and a second slot center on the second end face. A first connecting line between the first slot center and the rotation axis and a second connecting line between the second slot center and the rotation axis form a circumferential offset angle in the circumferential direction of the rotor assembly. The circumferential offset angles of the rotor slots in each core segment are the same. In each core segment pair, the absolute values ​​of the circumferential offset angles of the rotor slots of the two core segments are 360° / Z1 and 360° / Z2, respectively, where Z1 is the number of stator slots of the motor and Z2 is the number of rotor slots, and Z1 and Z2 are not equal.

2. The rotor assembly of the motor according to claim 1, characterized in that, The second end face of one of the adjacent iron core segments fits into the first end face of another adjacent iron core segment to form a mating end face. The line connecting the center of the second slot of the rotor slot of one iron core segment and the axis of rotation on the mating end face and the line connecting the center of the first slot of the rotor slot of the other iron core segment and the axis of rotation on the mating end face form a preset inter-segment misalignment angle in the circumferential direction.

3. The rotor assembly of the motor according to claim 2, characterized in that, The inter-segment misalignment angle is equal to 360° / 2Z2.

4. The rotor assembly of the motor according to claim 1, characterized in that, The n core segments define a virtual symmetry plane perpendicular to the rotation axis at the center of the rotor assembly in the axial direction. The absolute values ​​of the circumferential offset angles of the rotor slots of two core segments located on both sides of the virtual symmetry plane and in mirror-symmetrical positions are the same or different.

5. The rotor assembly of the motor according to claim 4, characterized in that, The rotor assembly includes a first core segment pair and a second core segment pair stacked sequentially in the axial direction of the rotor assembly. The absolute value of the circumferential offset angle of the rotor slot of the core segment of the first core segment pair that is close to the virtual symmetry plane is equal to the absolute value of the circumferential offset angle of the rotor slot of the core segment of the second core segment pair that is close to the virtual symmetry plane, and the absolute value of the circumferential offset angle of the rotor slot of the core segment of the first core segment pair that is far from the virtual symmetry plane is equal to the absolute value of the circumferential offset angle of the rotor slot of the core segment of the second core segment pair that is far from the virtual symmetry plane.

6. The rotor assembly of the motor according to claim 5, characterized in that, The absolute value of the circumferential offset angle of the rotor slot of the core segment in the first core segment pair that is far from the virtual symmetry plane and the absolute value of the circumferential offset angle of the rotor slot of the core segment in the second core segment pair that is far from the virtual symmetry plane are 360° / Z1. The absolute value of the circumferential offset angle of the rotor slot of the core segment in the first core segment pair that is close to the virtual symmetry plane and the absolute value of the circumferential offset angle of the rotor slot of the core segment in the second core segment pair that is close to the virtual symmetry plane are 360° / Z2.

7. The rotor assembly of the motor according to claim 1, characterized in that, Each of the n core segment pairs includes a preceding core segment and a following core segment stacked sequentially in the axial direction. In each core segment pair, the absolute value of the circumferential offset angle of the rotor slot of the preceding core segment is 360° / Z1, and the absolute value of the circumferential offset angle of the rotor slot of the following core segment is 360° / Z2.

8. The rotor assembly of the motor according to any one of claims 1-7, characterized in that, Z1 equals 48, and Z2 equals 40.

9. The rotor assembly of the motor according to any one of claims 1-7, characterized in that, The rotor slots are closed slots.

10. An electric motor, characterized in that, The motor includes: Stator assembly; and A rotor assembly is disposed inside the stator assembly, the rotor assembly being the rotor assembly of an electric motor according to any one of claims 1-9.

11. The motor according to claim 10, characterized in that, The motor is a 4-pole motor.

12. The motor according to claim 10, characterized in that, The stator assembly has Z1 stator slots evenly distributed circumferentially; the rotor assembly has Z2 rotor slots evenly distributed circumferentially; the stator slot distance angle of the stator slots is 360° / Z1, the rotor slot distance angle of the rotor slots is 360° / Z2, and the ratio of the rotor slot distance angle to the stator slot distance angle is 1.2.

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