Rotor assembly, rotor and electric machine

Abstract

The application provides a rotor assembly, a rotor and a motor. The rotor assembly comprises a rotor core, which comprises two core pieces with the same structure, the core pieces comprising a first core and a second core arranged at intervals; the first core comprises a ring part and a first tooth part, the second core comprises an arc part and a second tooth part, the second tooth parts are uniformly distributed on the inner wall of the arc part; the second core is arranged between two first tooth parts in a mode that the second tooth part is close to the ring part, the ring parts of the two core pieces are axially superposed, the first tooth part with a small axial thickness of one core piece is axially superposed with the second tooth part with a small axial thickness of the other core piece, and the rotor core is formed. The rotor core is formed by splicing, so that the inner side of the rotor assembly is connected as a whole, and the outer side is connected as a whole, the connecting surface of the core punching sheet is effectively reduced, and the magnetic energy loss is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric machines, and particularly relates to a rotor assembly, a rotor and an electric machine. BACKGROUND

[0002] Permanent magnet brushless DC motors are undergoing a process of rapid update iteration, and new structural electromagnetic designs are constantly replacing old designs. With the increasing demand for high performance of electric machines, embedded rotors gradually replace surface-mounted rotors, so developing a reasonable embedded structure rotor is the front direction of permanent magnet brushless motors.

[0003] Although the embedded rotor has the advantages of high magnetic energy utilization rate, large winding coefficient and available reluctance torque, the magnetic loss caused by the embedded structure itself is difficult to avoid, and therefore, designing a reasonable rotor structure to effectively reduce the magnetic energy loss is the most important thing in developing an embedded rotor motor. SUMMARY

[0004] Therefore, the application provides a rotor assembly, a rotor and an electric machine, which can solve the magnetic loss problem of the embedded rotor in the prior art.

[0005] In order to solve the above problems, the application provides a rotor assembly, comprising:

[0006] The rotor core comprises two iron core pieces with the same structure, and the iron core piece comprises a first iron core and a second iron core arranged at intervals;

[0007] The first iron core comprises a ring part and a first tooth part, and the first tooth part is uniformly distributed on the outer peripheral wall of the ring part; the first tooth part is provided with an odd number of first tooth parts, and the axial thickness of one first tooth part is less than that of the remaining first tooth parts;

[0008] The second iron core comprises an arc part and a second tooth part, and the second tooth part is uniformly distributed on the inner wall of the arc part; the second tooth part is provided with an odd number of second tooth parts, and the axial thickness of the second tooth part at the middle position is less than that of the remaining second tooth parts;

[0009] The number of the first tooth parts and the second tooth parts is the same; the second iron core is arranged between two adjacent first tooth parts in a manner that the second tooth part is close to the ring part, and the first tooth part and the second tooth part with small axial thickness are located on the same diameter;

[0010] The ring parts of the two iron core pieces are axially superimposed, the first tooth part with small axial thickness of one iron core piece is axially superimposed with the second tooth part with small axial thickness of the other iron core piece, and the rotor core is formed.

[0011] Optionally, the first core comprises a first punching sheet and a second punching sheet, the first punching sheet comprises a ring body and a first tapered tooth, a tooth tip of the first tapered tooth is connected to an outer peripheral wall of the ring body; the second punching sheet is identical in shape to the first tapered tooth; the first punching sheet and the second punching sheet are both provided in plurality, all the first punching sheets are stacked, and all the second punching sheets are stacked on one side of the first punching sheets.

[0012] Optionally, in a cross section of the rotor assembly, the number of the first tapered teeth is one more than the number of the second punching sheets.

[0013] Optionally, the first punching sheet is provided with Z first tapered teeth, and Z=(P+1) / 2, where Z is an odd number greater than 3, and P is the number of pole pairs of the rotor assembly; an adjacent tooth angle difference of the rotor assembly is a, and a=360° / 2P; an adjacent first tapered tooth angle difference of the first punching sheet is a1, and a1=(Z+3)*a / 2.

[0014] Optionally, the axial thickness of the first punching sheet is the same as the axial thickness of the second punching sheet.

[0015] Optionally, the second core comprises a third punching sheet and a fourth punching sheet, the third punching sheet comprises an arc segment and a second tapered tooth, a tooth root of the second tapered tooth is connected to an inner wall of the arc segment; the fourth punching sheet is identical in shape to the second tapered tooth; the third punching sheet and the fourth punching sheet are both provided in plurality, all the third punching sheets are stacked, and all the fourth punching sheets are stacked on one side of the third punching sheets.

[0016] Optionally, in a cross section of the rotor assembly, the number of the second tapered teeth is one more than the number of the fourth punching sheets.

[0017] Optionally, the third punching sheet is provided with Z second tapered teeth, and Z=(P+1) / 2, where Z is an odd number greater than 3, and P is the number of pole pairs of the rotor assembly; an adjacent tooth angle difference of the rotor assembly is a, and a=360° / 2P; an adjacent second tapered tooth angle difference of the third punching sheet is a2, and a2=(n-1)*a.

[0018] Optionally, the axial thickness of the third punching sheet is the same as the axial thickness of the fourth punching sheet, and is equal to the axial thickness of the first punching sheet and the axial thickness of the second punching sheet.

[0019] According to another aspect of the present application, a rotor is provided, comprising the rotor assembly as described in the above item.

[0020] Optionally, the rotor further comprises a permanent magnet arranged between the first and second conical teeth, and a plastic coating wrapping the rotor core and the permanent magnet.

[0021] According to still another aspect of the present application, there is provided an electric machine comprising the rotor assembly as described above or the rotor as described above.

[0022] The rotor assembly provided by the present application comprises a rotor core, which comprises two core pieces of the same structure, and the core pieces comprise a first core and a second core arranged at intervals; the first core comprises a ring part and a first tooth part, and the first tooth parts are uniformly distributed on the outer peripheral wall of the ring part; the first tooth parts are provided in odd number, and the axial thickness of one first tooth part is smaller than that of the remaining first tooth parts; the second core comprises an arc part and a second tooth part, and the second tooth parts are uniformly distributed on the inner wall of the arc part; the second tooth parts are provided in odd number, and the axial thickness of the second tooth part at the middle position is smaller than that of the remaining second tooth parts; the number of the first tooth parts is the same as that of the second tooth parts; the second core is arranged between two first tooth parts in such a manner that the second tooth part is close to the ring part, and the first tooth part and the second tooth part with small axial thickness are located on the same diameter; the ring parts of the two core pieces are axially superposed, and the first tooth part with small axial thickness of one core piece is axially superposed with the second tooth part with small axial thickness of the other core piece, thereby forming the rotor core.

[0023] The rotor core is formed by splicing, so that the inner part and the outer part of the rotor assembly are connected, the connecting surface of the core punching sheet is effectively reduced, the magnetic energy loss is reduced, and the overall structural strength of the rotor is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a structural schematic diagram of a first core according to an embodiment of the present application;

[0025] Figure 2 FIG. 2 is a structural schematic diagram of a first punching sheet according to an embodiment of the present application;

[0026] Figure 3 FIG. 3 is a structural schematic diagram of a second punching sheet according to an embodiment of the present application;

[0027] Figure 4 FIG. 4 is a structural schematic diagram of a second core according to an embodiment of the present application;

[0028] Figure 5 FIG. 5 is a structural schematic diagram of a third punching sheet according to an embodiment of the present application;

[0029] Figure 6A structure schematic diagram of a fourth punching sheet of an embodiment of the present application;

[0030] Figure 7 A top view schematic diagram of a core piece of an embodiment of the present application;

[0031] Figure 8 A top view of a rotor assembly of an embodiment of the present application;

[0032] Figure 9 An exploded view of a rotor assembly of an embodiment of the present application.

[0033] The signs of the reference numerals are as follows:

[0034] 1, first punching sheet; 11, ring body; 12, first conical tooth; 2, second punching sheet; 21, second tooth; 3, third punching sheet; 31, arc segment; 32, second conical tooth; 4, fourth punching sheet; 41, fourth tooth. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in connection with the embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0036] It should be noted that the terms “first”, “second” and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms “include” and “have” and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] For reference Figures 1 to 9 As shown, according to an embodiment of the present application, a rotor assembly comprises:

[0038] The rotor core comprises two core pieces of the same structure, and the core pieces comprise a first core and a second core arranged at intervals;

[0039] The first core comprises a ring part and first tooth parts which are uniformly distributed on the outer peripheral wall of the ring part; the first tooth parts are provided with an odd number, and the axial thickness of one first tooth part is less than that of the rest of the first tooth parts;

[0040] The second core comprises an arc part and second tooth parts which are uniformly distributed on the inner wall of the arc part; the second tooth parts are provided with an odd number, and the axial thickness of the second tooth part at the middle position is less than that of the rest of the second tooth parts;

[0041] The number of the first tooth parts and the second tooth parts is the same; the second core is placed between two adjacent first tooth parts with the second tooth part close to the ring part, and the first tooth part and the second tooth part with small axial thickness are located on the same diameter;

[0042] The ring parts of the two core pieces are axially superimposed, and the first tooth part with small axial thickness of one core piece is axially superimposed with the second tooth part with small axial thickness of the other core piece, thereby forming the rotor core.

[0043] The rotor core is formed by splicing, so that the inner part and the outer part of the rotor assembly are connected, the connecting surface of the core punching sheet is effectively reduced, the magnetic energy loss is reduced, and the overall structural strength of the rotor is enhanced.

[0044] In some embodiments, the first core comprises first punching sheets 1 and second punching sheets 2, the first punching sheets 1 comprise ring bodies 11 and first tapered teeth 12, the tooth tips of the first tapered teeth 12 are connected to the outer peripheral wall of the ring body 11; the second punching sheets 2 are the same shape as the first tapered teeth 12; the first punching sheets 1 and the second punching sheets 2 are provided with a plurality of, all the first punching sheets 1 are stacked, and all the second punching sheets 2 are stacked on one side of the first punching sheets 1.

[0045] The first core is composed of two layers of different punching sheets, forming a first punching sheet 1 connection, while the second punching sheet 2 does not want to be linked to the structure, effectively reducing the connecting surface of the core punching sheet and reducing the magnetic energy loss.

[0046] In some embodiments, on the cross section of the rotor assembly, the number of the first tapered teeth 12 is one more than the number of the second punching sheets 2.

[0047] Since the number of the second punching sheets 2 is relatively small compared to the number of the first tapered teeth 12, the number of the inner connection of the entire rotor core is greater than the number of the outer connection, thereby enhancing the overall structural strength of the rotor.

[0048] For example, the rotor core is assembled by two core pieces, each of the first and second punching sheets 1 and 2 has Z pieces, when the two core pieces are butted to form the whole rotor core structure, there are 2*Z connections inside the whole rotor core and 2*(Z-1) connections outside the whole rotor core, thus the whole structure strength is increased.

[0049] In some embodiments, the first punching sheet 1 is provided with Z first tapered teeth 12, and Z=(P+1) / 2, where Z is an odd number greater than 3 and P is the pole pair number of the rotor assembly; the adjacent tooth angle difference of the rotor assembly is a, and a=360° / 2P; the angle difference between the adjacent first tapered teeth 12 on the first punching sheet 1 is a1, and a1=(Z+3)*a / 2.

[0050] The distribution rule of the first tapered teeth 12 is that the first tapered teeth 12 with small axial thickness are located at the center line, (Z-1) teeth are symmetrically distributed along the center line, and there are (Z-1) / 2 teeth on the left and right sides of the center line, so that the angle between each tooth of the whole rotor core is a=360° / 2P, and the second first tapered tooth 12 on the first punching sheet 1 is offset from the first first tapered tooth 12 by a1=(Z+3)*a / 2, and when the number of teeth on one side is greater than 1, the distribution rule of the third tooth is a n =(((Z+3) / 2)+2*(n-2))*a. Assuming that the preferred combination of the rotor is 5-pole, the angle between each tooth of the rotor is a=360° / 10=36°, the number of teeth of the punching sheet 1 is Z=(P+1) / 2= (5+1) / 2=3, the first tooth is located at the center line, there is (3-1) / 2=1 tooth on the left and right sides of the center line, and the second tooth 21 is a1=(3+3)*a / 2=108° away from the first tooth. Another tooth is symmetrically distributed along the center line on the other side. The second punching sheet 2 has (Z-1) dispersed second teeth 21, except that the tooth located at the center line is missing, the other teeth coincide with the first punching sheet 1 and are laminated.

[0051] Preferably, the axial thickness of the first punching sheet 1 and the axial thickness of the second punching sheet 2 are the same.

[0052] In some embodiments, the second core includes a third punching sheet 3 and a fourth punching sheet 4, the third punching sheet 3 includes an arc segment 31 and a second tapered tooth 32, the tooth root of the second tapered tooth 32 is connected to the inner wall of the arc segment 31; the fourth punching sheet 4 has the same shape as the second tapered tooth 32; the third punching sheet 3 and the fourth punching sheet 4 are provided with a plurality of, all the third punching sheets 3 are laminated, and all the fourth punching sheets 4 are laminated on one side of the third punching sheet 3.

[0053] The second core is composed of two layers of different punching sheets, forming a third punching sheet 3 connection, and a fourth punching sheet 4 without linkage structure, effectively reducing the connection surface of the core punching sheet and reducing the magnetic energy loss.

[0054] In some embodiments, the number of the second conical teeth 32 is one more than the number of the fourth punching sheets 4 in cross section of the rotor assembly.

[0055] Since the number of the fourth punching sheets 4 is relatively small compared to the number of the second conical teeth 32, the number of the inner connections of the entire rotor core is greater than the number of the outer connections, thereby enhancing the structural strength of the entire rotor.

[0056] For example, the rotor core is assembled by two core pieces, the number of the third punching sheets 3 and the fourth punching sheets 4 of one core piece is Z, when the two core pieces are butted to form the entire rotor core structure, there are 2*Z connections on the inner side and 2*(Z-1) connections on the outer side of the entire rotor core, thereby increasing the structural strength of the entire rotor core.

[0057] In some embodiments, the third punching sheet 3 is provided with Z second conical teeth 32, and Z=(P+1) / 2, where Z is an odd number greater than 3, and P is the number of pole pairs of the rotor assembly; the angle difference between adjacent teeth of the rotor assembly is a, and a=360° / 2P; the angle difference between adjacent second conical teeth 32 on the third punching sheet 3 is a2, and a2=(n-1)*a.

[0058] The third punching sheet 3 has Z teeth, and the relationship between the number of teeth and the number of pole pairs is Z=(P+1) / 2 (Z is 3, 5, 7, 9, …) (P is the number of pole pairs of the rotor), and the distribution rule of the teeth is that the first tooth is located at the center line, (Z-1) teeth are symmetrically distributed along the center line, and there are (Z-1) / 2 teeth on the left and right sides of the center line, respectively (the angle between each tooth of the combined block rotor is a=360° / 2P), and the distribution rule of the second tooth 21 is a2=(n-1)*a. Assuming that the preferred combined block rotor is 5-pole, the angle between each tooth of the rotor is a=360° / 10=36°, the number of teeth of the punching sheet 3 is Z=(P+1) / 2= (5+1) / 2=3, the first tooth is located at the center line, there is (3-1) / 2=1 tooth on the left and right sides of the center line, respectively, the second tooth is a2=(2-1)*a / 2=36° away from the first tooth, and the other tooth is symmetrically distributed on the other side along the center line. The fourth punching sheet 4 has (Z-1) dispersed fourth teeth 41, and the other teeth coincide with the third punching sheet 3 except for the tooth located at the center.

[0059] When P=9, the first punching sheet 1 of the rotor has Z=(9+1) / 2=5, one first conical tooth 12 is located at the center line, (Z-1)=5-1=4 first conical teeth 12 are symmetrically distributed along the center line, there are (Z-1) / 2=2 first conical teeth 12 on each side, the second tooth 21 is located at a2=(Z+3)*a / 2=(5+3)*20° / 2=80° away from the center line (a=360° / 2*9=20°), the third tooth is distributed a n= (((Z+3) / 2) + 2*(n-2))*a°

[0060] = ((5+3) / 2) + 2*(3-2)*20° = 120° at …, and so on.

[0061] In some embodiments, the axial thickness of the third punching sheet 3 is the same as the axial thickness of the fourth punching sheet 4, and is equal to the axial thickness of the first punching sheet 1 and the axial thickness of the second punching sheet 2.

[0062] The first core is formed by layering the first punching sheet 1 and the second punching sheet 2, wherein the first punching sheet 1 is layered with a thickness of X1 (mm), the second punching sheet 2 is layered with a thickness of X2 (mm), and X1 = X2; the second core is formed by layering the third punching sheet 3 and the fourth punching sheet 4, wherein the third punching sheet 3 is layered with a thickness of X3 (mm), the fourth punching sheet 4 is layered with a thickness of X4 (mm), and X3 = X4 = X1 = X2; the combined block rotor is formed by combining two first cores and two second cores, wherein the first core / second core is flipped by 180° along the horizontal plane, and then the two cores are combined by the shaft hole as the center to form a columnar combined rotor. At this time, the combined block rotor core has Z punching sheets connected on the inside of each single layer, and Z punching sheets connected on the outside. Compared with the full connection of 2P punching sheets, the combined block rotor has only 2Z punching sheets connected, and the local magnetic energy loss is reduced to Z / P times of the original. The combined block rotor has 2Z connections on the inside and 2(Z-1) connections on the outside, a total of 4Z-2 connections. The staggered combination greatly improves the structural strength compared with the 2Z full connection.

[0063] According to another aspect of the present application, a rotor is provided, comprising the rotor assembly as described above.

[0064] In some embodiments, the rotor further comprises a permanent magnet arranged between the first tapered tooth 12 and the second tapered tooth 32, and a plastic wrapping layer wrapping the rotor core and the permanent magnet.

[0065] The rotor is composed of the two sets of first cores and the two sets of second cores, the permanent magnet, and the plastic wrapping layer. The first core and the second core are combined in a staggered manner, the first tapered tooth 12 and the second tapered tooth 32 are arranged with the permanent magnet, and finally a plastic wrapping layer is arranged on the outside to form a columnar combined rotor.

[0066] The connection between the parts can be achieved by, but not limited to, threaded fastening, pin fastening, plug-in fastening, and positioning column limiting.

[0067] The manufacturing process of the rotor includes the following steps:

[0068] Step 1: Select the rotor punching sheet according to the magnetic pole relationship and the design formula;

[0069] Second step: stamping the distributed teeth according to the designed rotor core stamping sheet;

[0070] Third step: stacking the rotor stamping sheet according to the designed rotor core;

[0071] Fourth step: assembling the rotor core into groups and injecting the rotor.

[0072] According to still another aspect of the present application, there is provided an electric machine comprising the rotor assembly as described above or the rotor as described above.

[0073] It is easily understood by those skilled in the art that the above-mentioned embodiments can be freely combined and superimposed without conflict.

[0074] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A rotor assembly, characterized in that, include: The rotor core includes two core components with identical structures, wherein the core components include a first core and a second core that are spaced apart from each other. The first iron core includes a ring portion and a first tooth portion, the first tooth portions being evenly distributed on the outer peripheral wall of the ring portion; the first tooth portion has an odd number, and the axial thickness of one first tooth portion is less than the axial thickness of the remaining first teeth portions; The second iron core includes an arc-shaped portion and a second toothed portion. The second teeth are evenly distributed on the inner wall of the arc-shaped portion. There is an odd number of second teeth, and the axial thickness of the second tooth in the middle position is less than the axial thickness of the other second teeth. The number of the first teeth and the second teeth are the same; the second core is positioned between two adjacent first teeth with the second teeth close to the ring, and the first teeth and the second teeth with smaller axial thickness are located on the same diameter; The ring portions of the two core components are axially superimposed, and the first tooth portion of one core component with a smaller axial thickness is axially superimposed with the second tooth portion of the other core component with a smaller axial thickness to form the rotor core.

2. The rotor assembly according to claim 1, characterized in that, The first iron core includes a first lamination (1) and a second lamination (2). The first lamination (1) includes a ring body (11) and a first conical tooth (12). The tip of the first conical tooth (12) is connected to the outer peripheral wall of the ring body (11). The second lamination (2) has the same shape as the first conical tooth (12). There are multiple first laminations (1) and second laminations (2). All first laminations (1) are stacked, and all second laminations (2) are stacked on one side of the first laminations (1).

3. The rotor assembly according to claim 2, characterized in that, On the cross-section of the rotor assembly, the number of the first conical teeth (12) is one more than the number of the second laminations (2).

4. The rotor assembly according to claim 3, characterized in that, The first lamination (1) has Z first conical teeth (12) such that Z = (P+1) / 2, where Z is an odd number greater than 3 and P is the number of pole pairs of the rotor assembly; the angle difference between adjacent teeth of the rotor assembly is a, a = 360° / 2P; the angle difference between adjacent first conical teeth (12) on the first lamination (1) is a1, a1 = (Z+3)*a / 2.

5. The rotor assembly according to any one of claims 2-4, characterized in that, The axial thickness of the first lamination (1) is the same as that of the second lamination (2).

6. The rotor assembly according to claim 5, characterized in that, The second iron core includes a third lamination (3) and a fourth lamination (4). The third lamination (3) includes an arc segment (31) and a second conical tooth (32). The root of the second conical tooth (32) is connected to the inner wall of the arc segment (31). The fourth lamination (4) has the same shape as the second conical tooth (32). There are multiple third laminations (3) and fourth laminations (4). All third laminations (3) are stacked. All fourth laminations (4) are stacked on one side of the third laminations (3).

7. The rotor assembly according to claim 6, characterized in that, On the cross-section of the rotor assembly, the number of the second conical teeth (32) is one more than the number of the fourth laminations (4).

8. The rotor assembly according to claim 7, characterized in that, The third lamination (3) has Z second conical teeth (32) such that Z = (P+1) / 2, where Z is an odd number greater than 3 and P is the number of pole pairs of the rotor assembly; the angle difference between adjacent teeth of the rotor assembly is a, a = 360° / 2P; the angle difference between adjacent second conical teeth (32) on the third lamination (3) is a2, a2 ​​= (n-1)*a.

9. The rotor assembly according to any one of claims 6-8, characterized in that, The axial thickness of the third lamination (3) is the same as that of the fourth lamination (4), and equal to the axial thickness of the first lamination (1) and the axial thickness of the second lamination (2).

10. A rotor, characterized in that, Includes the rotor assembly as described in any one of claims 1-9.

11. The rotor according to claim 10, characterized in that, The first iron core includes a first lamination (1) and a second lamination (2). The first lamination (1) includes a ring body (11) and a first conical tooth (12). The tip of the first conical tooth (12) is connected to the outer peripheral wall of the ring body (11). The second lamination (2) has the same shape as the first conical tooth (12). There are multiple first laminations (1) and second laminations (2). All first laminations (1) are stacked, and all second laminations (2) are stacked on one side of the first laminations (1). The second iron core includes a third lamination (3) and a fourth lamination (4). The third lamination (3) The rotor includes an arc segment (31) and a second conical tooth (32), the root of which is connected to the inner wall of the arc segment (31); the fourth lamination (4) has the same shape as the second conical tooth (32); multiple third laminations (3) and fourth laminations (4) are provided, all third laminations (3) are stacked, and all fourth laminations (4) are stacked on one side of the third laminations (3); the rotor also includes a permanent magnet and a plastic coating, the permanent magnet is located between the first conical tooth (12) and the second conical tooth (32), and the plastic coating covers the rotor core and the permanent magnet.

12. An electric motor, characterized in that, It includes the rotor assembly as described in any one of claims 1-9 or the rotor as described in any one of claims 10-11.

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