Rotor structure and electric machine

Abstract

The application provides a rotor structure and a motor. The rotor structure comprises a rotor core (1) and permanent magnets (2) which are attached to the outer periphery of the rotor core (1), the permanent magnets (2) are multiple, the multiple permanent magnets (2) are uniformly distributed along the circumferential direction of the rotor core (1), and the outer surface of the permanent magnet (2) is provided with at least two grooves (3) which are symmetrical about the magnetic pole center line of the permanent magnet (2). According to the rotor structure of the application, the cogging torque and the eddy current loss of the motor can be effectively reduced, and the efficiency of the motor is improved.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to a rotor structure and a motor. Background Technology

[0002] In surface-mount permanent magnet synchronous motors, each pole of the rotor is supplied with magnetic flux by two permanent magnets, allowing for higher power density compared to other types of rotor motors. However, due to the characteristics of the cogging structure and the widespread use of neodymium iron boron permanent magnet materials, cogging torque and eddy current losses occur during motor operation. This causes torque fluctuations, increases permanent magnet temperature, and consequently affects the distribution of the air gap magnetic flux density (air gap magnetic field), ultimately leading to vibration, noise, and decreased motor efficiency. Therefore, solving the problems of high cogging torque and eddy current losses in high-power-density permanent magnet synchronous motors is a key challenge for motor developers. Summary of the Invention

[0003] The main objective of this invention is to provide a rotor structure and motor that can effectively reduce the cogging torque and eddy current loss of the motor and improve the motor efficiency.

[0004] To achieve the above objectives, according to one aspect of the present invention, a rotor structure is provided, comprising a rotor core and a permanent magnet attached to the outer periphery of the rotor core. The permanent magnets are a plurality of each other and are evenly distributed along the circumference of the rotor core. The outer surface of the permanent magnets is provided with at least two grooves symmetrical about the magnetic pole centerline of the permanent magnet.

[0005] Furthermore, the radial thickness of the permanent magnet is h1, and the radial height of the groove is h2, where 0 < h2 / h1 ≤ 0.7.

[0006] Furthermore, there are two grooves, and the opening width of the groove is b2, where 0 < b2 ≤ 1 mm.

[0007] Furthermore, the opening width of the groove is b2, where 0 < b2 ≤ 0.2 mm.

[0008] Furthermore, there are two grooves, and the distance between the two grooves on the same permanent magnet and the center line of the magnetic pole of the permanent magnet is b1. The circumferential width of the permanent magnet is 2a, and 0.25≤2b1 / 2a=b1 / a≤0.5.

[0009] Furthermore, 2mm≤b1≤4mm, 15mm≤2a≤17mm.

[0010] Furthermore, there are two grooves, the opening width of the grooves is b2, the distance between the two grooves on the same permanent magnet and the center line of the magnetic pole of the permanent magnet is b1, and the relationship between b1 and b2 satisfies 0.1≤b2 / b1≤1.5.

[0011] Furthermore, within a cross-section perpendicular to the central axis of the rotor core, the groove can be rectangular, U-shaped, arc-shaped, or parallelogram-shaped.

[0012] Furthermore, in a cross section perpendicular to the central axis of the rotor core, the groove is a parallelogram. The parallelogram includes two sides located on both sides along the circumference. The line connecting the outer end of one side to the center of the rotor core is the first line. The angle formed by the side and the first line is θ3, where θ3 satisfies 15°≤θ3≤75°.

[0013] Furthermore, the groove extends axially along the rotor core.

[0014] Furthermore, the groove extends axially through both ends of the rotor core; or, the groove extends axially through one end of the rotor core; or, the groove has a preset distance from both end faces of the rotor core.

[0015] According to another aspect of the present invention, an electric motor is provided, including a rotor structure, which is the rotor structure described above.

[0016] Furthermore, the motor also includes a stator structure, and the rotor structure is housed within the stator structure. The stator structure includes stator windings, which are concentrated windings.

[0017] According to the technical solution of this invention, the rotor structure includes a rotor core and permanent magnets attached to the outer periphery of the rotor core. Multiple permanent magnets are evenly distributed along the circumference of the rotor core. The outer surface of each permanent magnet has at least two grooves symmetrically positioned about the center line of its magnetic poles. By creating at least two symmetrical grooves about the center line of the permanent magnets on the rotor structure, the magnetic circuit on the surface of the permanent magnets can be optimized and adjusted, improving the magnetic field distribution between the stator and rotor, reducing cogging torque, reducing the skin effect on the surface of the permanent magnets, and effectively reducing the eddy current density on the surface of the permanent magnets, thereby improving motor efficiency. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic diagram of the structure of a motor according to an embodiment of the present invention is shown;

[0020] Figure 2 A structural dimension diagram of the rotor structure according to an embodiment of the present invention is shown;

[0021] Figure 3 A structural dimension diagram of the rotor structure according to an embodiment of the present invention is shown;

[0022] Figure 4 A schematic diagram of the structure of a motor according to an embodiment of the present invention is shown;

[0023] Figure 5 It shows Figure 4 A magnified view of a portion at point A;

[0024] Figure 6 The equivalent impedance diagram of an ungrooved permanent magnet in the related technology is shown;

[0025] Figure 7 An equivalent impedance diagram of a slotted permanent magnet according to an embodiment of the present invention is shown;

[0026] Figure 8 The diagram shows the eddy current distribution of an ungrooved permanent magnet in the related technology;

[0027] Figure 9 An eddy current distribution diagram of a slotted permanent magnet according to an embodiment of the present invention is shown;

[0028] Figure 10 The diagram shows the cogging torque curve of an ungrooved permanent magnet in the related technology;

[0029] Figure 11 The diagram shows the b1 and b2 curves of the cogging torque of the rotor structure according to an embodiment of the present invention; and

[0030] Figure 12 The diagram shows the h1 curve of the cogging torque of the rotor structure according to an embodiment of the present invention.

[0031] The above figures include the following reference numerals:

[0032] 1. Rotor core; 2. Permanent magnet; 3. Groove; 4. Stator structure. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] See also Figures 1 to 5 As shown, according to an embodiment of the present invention, the rotor structure includes a rotor core 1 and a permanent magnet 2 attached to the outer periphery of the rotor core 1. There are multiple permanent magnets 2, which are evenly distributed along the circumference of the rotor core 1. The outer surface of the permanent magnet 2 is provided with at least two grooves 3 that are symmetrical about the magnetic pole center line of the permanent magnet 2.

[0035] By creating at least two grooves 3 symmetrical about the magnetic pole centerline of the permanent magnet 2 on the rotor structure, the magnetic circuit on the surface of the permanent magnet 2 can be optimized and adjusted using the grooves 3, thereby improving the magnetic field distribution between the stator and rotor, reducing cogging torque, reducing the skin effect on the surface of the permanent magnet 2, effectively reducing the eddy current density on the surface of the permanent magnet 2, thereby reducing the temperature rise of the permanent magnet and improving the motor efficiency.

[0036] In one embodiment, the outer periphery of the rotor core 1 is a complete circle, and the permanent magnet 2 is fixedly bonded to the surface of the rotor core 1 with adhesive before magnetization. In this embodiment, the permanent magnet 2 is located entirely outside the rotor core 1.

[0037] In one embodiment, a mounting groove is formed on the outer peripheral wall of the permanent magnet 2, the permanent magnet is embedded in the mounting groove, and then it is fixed by adhesive. In this embodiment, the permanent magnet 2 can be completely embedded in the mounting groove or partially embedded in the mounting groove.

[0038] In one embodiment, the permanent magnet 2 is tangentially magnetized, and the polarities of the faces of two adjacent permanent magnets 2 are the same, thereby jointly providing the magnetomotive force of that pole, which greatly improves the power density of the motor and enables the motor to be miniaturized.

[0039] In one embodiment, the number of permanent magnets 2 is 10.

[0040] In one embodiment, the permanent magnet 2 is tile-shaped.

[0041] In one embodiment, the radial thickness of the permanent magnet 2 is h1, and the radial height of the groove 3 is h2, where 0 < h2 / h1 ≤ 0.7.

[0042] In this embodiment, by defining the proportional relationship between the radial thickness h1 of the permanent magnet 2 and the radial height h2 of the groove 3, the value of h2 can be associated with h1. Thus, h2 can be defined by h1, and the radial height of the groove 3 can be adaptively adjusted according to the change in the radial thickness of the permanent magnet 2. A better fit can be obtained, so that the obtained permanent magnet 2 can effectively destroy the skin effect on the surface of the permanent magnet, reduce the eddy current on the surface of the permanent magnet 2, thereby reducing the temperature rise of the permanent magnet 2 and improving the working performance of the permanent magnet 2.

[0043] h2 represents the groove depth of permanent magnet 2. Therefore, the value of h2 should not be too large, and it needs to be able to ensure the mechanical strength of permanent magnet 2. In order to achieve this purpose, the groove depth h2 of permanent magnet 2 should not exceed 70% of the radial thickness h1 of permanent magnet 2, that is, 0 < h2 / h1 ≤ 0.7.

[0044] In one embodiment, 0.1≤h2 / h1≤0.7 ensures that the groove 3 on the permanent magnet 2 has sufficient depth to optimize the surface structure of the permanent magnet 2, effectively destroy the skin effect on the surface of the permanent magnet 2, and reduce eddy current loss. At the same time, it avoids that the groove 3 on the permanent magnet 2 is too deep, which would significantly reduce the mechanical strength of the permanent magnet 2 and ensure that the permanent magnet 2 can operate stably and reliably.

[0045] In one embodiment, there are two grooves 3, and the opening width of the groove 3 is b2, where 0 < b2 ≤ 1 mm.

[0046] By limiting the opening width of groove 3 to no more than 1mm, it is possible to avoid reducing the mechanical strength of the permanent magnet and the performance of the motor due to excessively large groove width.

[0047] In one embodiment, the opening width of the groove 3 is b2, where 0 < b2 ≤ 0.2 mm. This can more effectively reduce the cogging torque of the motor while avoiding excessively large groove widths that would reduce the mechanical strength of the permanent magnet and the performance of the motor.

[0048] In one embodiment, there are two grooves 3. The distance between the two grooves 3 on the same permanent magnet 2 and the center line of the magnetic pole of the permanent magnet 2 is b1. The circumferential width of the permanent magnet 2 is 2a, and 0.25≤2b1 / 2a=b1 / a≤0.5.

[0049] See also Figure 11 and Figure 12 As shown, when b1 = 0.5, 1, 3, and 4 mm, the cogging torque gradually increases with the increase of b2; when b1 = 2 and 5.5 mm, the cogging torque gradually decreases with the increase of b2. Therefore, based on this characteristic, the trough range of the cogging torque can be determined, and thus the relationship between the distance 2b1 between the two grooves 3 and the circumferential width 2a of the permanent magnet 2 can be determined, so that the cogging torque generated by the motor can be controlled within an optimal range. Research has found that when the relationship between b1 and a satisfies 0.25 ≤ b1 / a ≤ 0.5, the slotting of the permanent magnet 2 can effectively reduce the cogging torque of the motor.

[0050] See also Figure 10 and Figure 11 As shown, a comparison is made between the cogging torque of the permanent magnet slotted motor in the related art and the cogging torque of the permanent magnet slotted motor in the present application embodiment. It can be seen that when b2 = 0.2 mm and b1 = 0.5, 3, 3.5, 4 and 6 mm, the cogging torque of the permanent magnet slotted motor is less than that of the unslotted motor.

[0051] When selecting Figure 11Two points with better results were b1 = 0.5, b2 = 0.2 mm and b1 = 0.35, b2 = 0.4 mm. Using the parameters of these two points and then changing the value of h1, from... Figure 12 It can be seen that the cogging torque gradually decreases as h2 increases, but the decreasing trend becomes very slow after h2 reaches 0.9-1 mm. Therefore, based on this characteristic, 0.4 ≤ h2 / h1 ≤ 0.5 is the optimal solution for reducing the cogging torque.

[0052] from Figure 11 and Figure 12 It can be seen that by comparing the effects of parameters b1, b2 and h2 on the cogging torque, it can be concluded that parameters b1 and b2 have a greater impact on the cogging torque of the motor, while the slotting depth h2 has a smaller impact on the cogging torque of the motor after reaching a certain value. Therefore, when slotting permanent magnets, the slotting depth h2 can be preset according to the size of h1, and then the parameters b1 and b2, that is, the spacing between the two grooves 3 and the opening width of the groove 3, should be the focus.

[0053] In one embodiment, 2mm≤b1≤4mm, 15mm≤2a≤17mm. The spacing between the two grooves 3 is affected by the circumferential width of the permanent magnet 2. The matching relationship between the two has a significant impact on the cogging torque of the motor. By reasonably limiting the numerical matching relationship between the two, the grooves on the surface of the permanent magnet 2 can form a good structural design, which can control the cogging torque of the motor within a low range, improve the working performance of the motor, and reduce the temperature rise of the permanent magnet.

[0054] In one embodiment, 2.5mm ≤ b1 ≤ 3.5mm, 2a = 16mm.

[0055] In one embodiment, there are two grooves 3, the opening width of the groove 3 is b2, the distance between the two grooves 3 on the same permanent magnet 2 and the center line of the magnetic pole of the permanent magnet 2 is b1, and the relationship between b1 and b2 satisfies 0.1≤b2 / b1≤1.5, which can make the cogging torque of the motor smaller.

[0056] In one embodiment, 0.1≤b2 / b1≤0.3. Within this range, the structural design of the groove 3 is better, which makes the matching relationship between the opening width of the groove 3 and the distance between the two grooves 3 better, and can more effectively reduce the cogging torque of the motor.

[0057] In one embodiment, the groove 3 has the largest width at the opening.

[0058] In one embodiment, the parameters of the motor are as follows:

[0059] Rotor outer diameter = 63mm;

[0060] Air gap length Q = 1 mm;

[0061] Stator outer diameter = 124 mm;

[0062] The thickness of the permanent magnet is h1 = 2mm.

[0063] Formula 1 is the formula for calculating the cogging torque of a motor, where l represents the axial length of the motor.

[0064]

[0065] like Figure 10 As shown, the cogging torque of the slotless permanent magnet motor in the relevant technology is simulated, and the cogging torque can be calculated to be 58.0315 mN.m.

[0066] Where h2 is ≤1.4mm and b2 is ≤1mm.

[0067] In one embodiment, the included angle between the two grooves 3 on the same permanent magnet 2 is θ1, where 6°≤θ1≤15°. θ1 defines the included angle between the two grooves 3, matches the diameter of the rotor core 1, and determines the spacing between the two grooves 3.

[0068] In one embodiment, the angle between the radial outer endpoints of the two sides of the groove 3 and the center line of the rotor core 1 is θ2, where 0.5°≤θ1≤2°.

[0069] The groove 3 can have various shapes. In one embodiment, the groove 3 can be rectangular, U-shaped, arc-shaped or parallelogram-shaped in a cross section perpendicular to the central axis of the rotor core 1.

[0070] In one embodiment, in a cross section perpendicular to the central axis of the rotor core 1, the groove 3 is a parallelogram in shape. The parallelogram includes two sides located on both sides along the circumference. The line connecting the outer end of one of the sides to the center of the rotor core is a first line. The angle formed by the side and the first line is θ3, where θ3 satisfies 15°≤θ3≤75°.

[0071] In this embodiment, the groove 3 is a parallelogram, which makes the groove 3 form an inclined structure, which can more effectively reduce the eddy current loss of the permanent magnet 2 and improve the working performance of the permanent magnet.

[0072] In one embodiment, the groove 3 extends along the axial direction of the rotor core 1.

[0073] In one embodiment, the groove 3 extends axially through both ends of the rotor core 1. This structure is simple to process and can more effectively isolate the surface structure of the permanent magnet 2 and more effectively destroy the skin effect on the surface of the permanent magnet 2.

[0074] In one embodiment, the groove 3 extends axially through one end of the rotor core 1.

[0075] In one embodiment, the groove 3 has a preset distance from both end faces of the rotor core 1.

[0076] The axial extension length of the groove 3 can be designed and arranged as needed, thus making the structural design more flexible and making it easier to obtain the required structure.

[0077] The simplified model of the equivalent impedance of permanent magnet 2 is as follows: Figure 6 and Figure 7 As shown, where Figure 6 This is a diagram showing the equivalent impedance model of an ungrooved permanent magnet in related technologies. Figure 7 This is an equivalent impedance model diagram of a slotted permanent magnet according to an embodiment of the present invention, where the width of the permanent magnet is 2a and the axial length of the permanent magnet is 2b. The segmentation effect of the permanent magnet can be understood as an increase in the equivalent resistance of the permanent magnet.

[0078] When two grooves 3 are set on the permanent magnet 2, it is equivalent to dividing the surface of the permanent magnet 2 into three pieces, and the cut surface has two more equivalent resistances Rb. When the permanent magnet is divided into N segments, there will be N more Rb.

[0079] Based on the skin effect of eddy currents, it can be seen that eddy currents are distributed on the surface of the permanent magnet; the eddy current distribution before and after slotting the permanent magnet is as follows: Figure 8 and Figure 9 As shown, where Figure 8 This is a diagram showing the eddy current distribution of ungrooved permanent magnets in related technologies. Figure 9 This is an eddy current distribution diagram of the slotted permanent magnet according to an embodiment of the present invention. Figure 8 and Figure 9 The comparison shows that slotting the permanent magnet can effectively reduce the eddy current density on the surface of permanent magnet 2.

[0080] Formula 2 can be used to calculate the eddy current loss before and after slotting the permanent magnet, where N represents the number of segments of the permanent magnet; the calculated eddy current loss of the motor using the unslotted permanent magnet is W_unslotted = 45W, and the eddy current loss of the motor using the slotted permanent magnet is W_slotted = 18W.

[0081]

[0082] The difference between the eddy current loss of a motor using slotted permanent magnets and that of a motor using unslotted permanent magnets is 45-18=27W. The reduction in eddy current loss is 27W / 45W=60%. In other words, the eddy current loss of the motor using the rotor structure of this invention is reduced by 60% compared to motors in related technologies. The significant reduction in eddy current loss effectively controls the temperature rise of the permanent magnets and improves the performance of the motor.

[0083] The calculation results show that slotting permanent magnets can effectively reduce eddy current losses.

[0084] Based on the above analysis, when the fixed air gap length Q = 1mm, the rotor outer diameter = 63mm, and the permanent magnet thickness = 2mm, by opening grooves 3 symmetrically on both sides of the permanent magnet centerline, and changing the groove width b2, the distance between the two grooves 2b1, and the groove depth h1, the cogging torque of the motor can be effectively reduced. By circumferentially slotting the permanent magnet, the eddy current loss of the permanent magnet can be effectively reduced, thereby improving the heating of the permanent magnet.

[0085] According to an embodiment of the present invention, the motor includes a rotor structure, which is the rotor structure described above.

[0086] In one embodiment, the motor further includes a stator structure 4, and a rotor structure is fitted inside the stator structure 4. The stator structure 4 includes a stator winding, which is a concentrated winding.

[0087] An air gap with length Q is formed between the stator core of stator structure 4 and the permanent magnet 2 of rotor structure. The stator core and rotor core are formed by stacking electro-permanent magnet plates. Most of the rotor structure is the main magnetic circuit, which together with the stator core provides the magnetic circuit for magnetomotive force.

[0088] In one embodiment, the motor is a permanent magnet synchronous motor.

[0089] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0090] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rotor structure, characterized in that, It includes a rotor core (1) and a permanent magnet (2) attached to the outer periphery of the rotor core (1). There are multiple permanent magnets (2), which are evenly distributed along the circumference of the rotor core (1). The outer surface of the permanent magnet (2) is provided with at least two grooves (3) symmetrical about the magnetic pole center line of the permanent magnet (2). The radial thickness of the permanent magnet (2) is h1, and the radial height of the groove (3) is h2, wherein 0.4≤h2 / h1≤0.5; The number of grooves (3) is two. The distance between the two grooves (3) on the same permanent magnet (2) and the magnetic pole center line of the permanent magnet (2) is b1. The circumferential width of the permanent magnet (2) is 2a, and 0.25≤b1 / a≤0.

5.

2. The rotor structure according to claim 1, characterized in that, The number of grooves (3) is two, and the opening width of the grooves (3) is b2, 0 < b2 ≤ 1 mm.

3. The rotor structure according to claim 2, characterized in that, The opening width of the groove (3) is b2, 0 < b2 ≤ 0.2 mm.

4. The rotor structure according to claim 1, characterized in that, 1mm≤b1≤6mm, 15mm≤2a≤17mm.

5. The rotor structure according to claim 1, characterized in that, The number of grooves (3) is two, the opening width of the grooves (3) is b2, the distance between the two grooves (3) on the same permanent magnet (2) and the magnetic pole center line of the permanent magnet (2) is b1, and the relationship between b1 and b2 satisfies 0.1≤b2 / b1≤1.

5.

6. The rotor structure according to any one of claims 1 to 5, characterized in that, Within a cross section perpendicular to the central axis of the rotor core (1), the groove (3) is rectangular, U-shaped, arc-shaped, or parallelogram-shaped.

7. The rotor structure according to any one of claims 1 to 5, characterized in that, In a cross section perpendicular to the central axis of the rotor core (1), the groove (3) is a parallelogram. The parallelogram includes two sides located on both sides along the circumference. The line connecting the outer end of one of the sides and the center of the rotor core is a first line. The angle formed by the side and the first line is θ3, where θ3 satisfies 15°≤θ3≤75°.

8. The rotor structure according to any one of claims 1 to 5, characterized in that, The groove (3) extends along the axial direction of the rotor core (1).

9. The rotor structure according to claim 8, characterized in that, The groove (3) extends through both ends of the rotor core (1) axially; or, the groove (3) extends through one end of the rotor core (1) axially; or, the groove (3) has a preset distance from both end faces of the rotor core (1).

10. An electric motor, comprising a rotor structure, characterized in that, The rotor structure is the rotor structure according to any one of claims 1 to 9.

11. The motor according to claim 10, characterized in that, The motor also includes a stator structure (4), and the rotor structure is fitted inside the stator structure (4). The stator structure (4) includes a stator winding, which is a concentrated winding.

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