Rotating electric machine

Abstract

This rotating electric machine comprises: a stator (10) that includes a plurality of teeth (11) extending in a radial direction at intervals in a circumferential direction; a rotor (20) that is provided so as to be rotatable with respect to the stator (10); and a case (30) that accommodates the stator (10) and the rotor (20) and includes a side part (33) facing the stator (10) in an axial direction. The side part (33) includes a spoke part (34) and a high-resistance region (35) arranged alternately in the circumferential direction. The high-resistance region (35) has a higher electrical resistivity than the spoke part (34). When viewed from the axial direction, the high-resistance region (35) is located between any two of the plurality of teeth (11).

Description

Rotating electrical machine

[0001] The present invention relates to a rotating electrical machine.

[0002] Patent Document 1 discloses a spindle motor including a base and a rotor portion. The base includes a stator core around which a coil winding is wound. On the other hand, the rotor portion includes a rotor magnet rotatably supported on the base via a bearing portion. The rotor magnet is provided around the outer periphery of the stator core and faces the stator core in the radial direction.

[0003] Japanese Patent Application Laid-Open No. 2008-109793

[0004] In the spindle motor of Patent Document 1, a metal stator is close to a rotatably provided rotor. Therefore, leakage magnetic flux generated by a magnet provided on the rotor and a coil of the stator flows through the stator and the rotor, thereby generating eddy current loss. In order to suppress this eddy current loss, a magnetic attraction plate formed of a powder magnetic material is attached to a portion of the stator that faces the magnet provided on the rotor. However, when the magnetic flux penetrating the magnetic attraction plate increases and the magnetic flux density inside it saturates, the eddy current loss generated in the stator cannot be sufficiently reduced.

[0005] An object of the present invention is to provide a rotating electrical machine capable of suppressing eddy current loss generated in a stator and a rotor.

[0006] A rotating electrical machine according to an aspect of the present invention includes a stator including a plurality of teeth extending in the radial direction at intervals in the circumferential direction, a rotor rotatably provided with respect to the stator, and a case that houses the stator and the rotor and includes side portions facing the stator in the axial direction. The side portions include spoke portions and high-resistance regions alternately arranged in the circumferential direction. The high-resistance region has a higher electrical resistivity than the spoke portions. When viewed from the axial direction, the high-resistance region is located between any two of the plurality of teeth.

[0007] According to the present invention, it is possible to provide a rotating electrical machine capable of suppressing eddy current loss generated in a stator and a rotor.

[0008] Figure 1 is a cross-sectional view showing the structure of a rotating electric machine according to an embodiment. Figure 2 is a view showing a part of the cross-section along line A-A in Figure 1. Figure 3 is a view showing a part of the cross-section along line B-B in Figure 1. Figure 4 is a view showing a part of the cross-section along line B-B in Figure 1. Figure 5 is a view showing a part of the cross-section along line B-B in Figure 1. Figure 6 is a perspective view showing a part of the case according to an embodiment. Figure 7 is a cross-sectional view showing the structure of a rotating electric machine according to one modified example of the embodiment.

[0009] The rotating electric machine according to the embodiment will be described below with reference to the drawings. Elements having the same function are denoted by the same reference numerals, and redundant explanations will be omitted.

[0010] As illustrated in Figure 1, the motor 1, which is a rotating electric machine, comprises a stator 10, a rotor 20, and a case 30. As illustrated in Figure 2, the stator 10 is located radially inward of the rotor core 21 and is fixed to the inner cylindrical portion 32 of the case 30. The stator 10 has a plurality of teeth 11 that are spaced apart in the circumferential direction CD and extend radially outward. In other words, the plurality of teeth 11 are arranged radially around the center of the axis 2. The stator 10 may also be composed of fractional slots such that the number of slots 12 divided by the number of poles of the rotor 20 is an irreducible fraction.

[0011] As illustrated in Figure 2, a slot 12, which is a space for housing a coil 13, is formed between two adjacent teeth 11, 11 in the circumferential direction CD. The coil 13 is wound around each tooth 11, and a portion of it is housed in the slot 12. The motor 1 according to this embodiment is a so-called outer rotor type motor. Therefore, the tip of each tooth 11 faces the magnet 23 of the rotor core 21 in the radial direction RD.

[0012] The rotor 20 is rotatable around the shaft 2 and relative to the stator 10. The rotor 20 comprises a rotor core 21 and a shaft 22 that supports the rotor core 21. The rotor core 21 is formed in a cylindrical shape with the shaft 2 as its center and holds a plurality of magnets 23. The plurality of magnets 23 are arranged in a circumferential direction CD with alternating polarities and face the teeth 11 of the stator 10.

[0013] The case 30 houses the stator 10 and the rotor 20. The case 30 includes an outer cylinder portion 31 located radially outward from the rotor 20, an inner cylinder portion 32 located radially inward from the outer cylinder portion 31, and a side portion 33 connecting the outer cylinder portion 31 and the inner cylinder portion 32. The outer cylinder portion 31 surrounds the outer circumference of the rotor 20. On the other hand, the inner cylinder portion 32 supports the central part of the stator 10. Therefore, the stator 10 is located between the outer cylinder portion 31 and the inner cylinder portion 32. The side portion 33 connecting the outer cylinder portion 31 and the inner cylinder portion 32 faces the stator 10 in the axial direction AD.

[0014] As illustrated in Figure 3, the side portion 33 includes spoke portions 34 and high-resistance regions 35 that are alternately arranged in the circumferential direction CD. The spoke portions 34 extend from the inner cylinder portion 32 to the outer cylinder portion 31 and are connecting portions that connect the outer cylinder portion 31 and the inner cylinder portion 32. The spoke portions 34 along the circumferential direction CD may be constant or vary over the radial direction RD. In order to provide the case 30 with sufficient mechanical strength, the spoke portions 34 are made of metal.

[0015] The high-resistance region 35 has a higher electrical resistivity than the spoke portion 34. The high-resistance region 35 illustrated in Figures 1 and 3 is formed by space. That is, the high-resistance region 35 illustrated in these figures is a hole (cavity) that penetrates the side portion 33 in the axial direction AD.

[0016] Viewed from the axial direction AD, the high-resistance region 35 is located between any two of the multiple teeth 11. For example, the high-resistance region 35 is located between the respective centerlines 11a of any two of the multiple teeth 11. As illustrated in Figure 3, the high-resistance region 35 is formed between two adjacent teeth 11. That is, at least a portion of the high-resistance region 35 is located in a position that overlaps with the slot 12 when viewed from the axial direction AD. Therefore, the spoke portion 34 is located in a position that overlaps with the teeth 11 when viewed from the axial direction AD.

[0017] As the rotor 20 rotates in the circumferential direction CD, magnetic flux is generated inside the case 30 in various directions. Of these, the intensity of the intersecting magnetic flux on the side portion 33 is relatively large between two adjacent teeth 11, that is, where the slot 12 housing part of the coil 13 is located. In this embodiment, a high-resistance region 35 is provided on the side portion 33 at a location corresponding to this area.

[0018] As illustrated in Figure 4, the width W1 of the high-resistance region 35 along the circumferential direction may increase as it extends radially outward. For example, the high-resistance region 35 has a trapezoidal or fan-shaped outline with a cut-out top when viewed from the axial direction AD.

[0019] As illustrated in Figure 5, the high-resistance region 35 may be formed by a structure with a higher electrical resistivity than the spoke portion 34. Such a structure may be an insulator such as resin or ceramic.

[0020] As illustrated in Figure 6, the length L of the spoke portion 34 along the axial direction AD may be greater than the width W2 of the spoke portion 34 along the circumferential direction CD. In this case, as illustrated in Figure 7, the spoke portion 34 may be covered by the cover portion 36 from the outside of the case 30, in other words, from the side opposite to the side where the stator 10 is located relative to the spoke portion 34. The cover portion 36 is a plate member having a predetermined thickness in the axial direction AD, and may be integrally formed with the case 30, or it may be fixed to the case 30 using predetermined fasteners such as screws. In either case, the cover portion 36 covers the high-resistance region 35 from the axial direction.

[0021] (1) The rotating electric machine according to the embodiment includes a stator 10 including a plurality of teeth 11 that are spaced apart in the circumferential direction CD and extend in the radial direction RD, a rotor 20 that is rotatably mounted relative to the stator 10, and a case 30 that houses the stator 10 and the rotor 20 and includes a side portion 33 that faces the stator 10 in the axial direction AD. The side portion 33 includes spoke portions 34 and a high-resistance region 35 that are alternately arranged in the circumferential direction CD. The high-resistance region 35 has a higher electrical resistivity than the spoke portions 34. When viewed from the axial direction AD, the high-resistance region 35 is located between any two of the plurality of teeth 11. With the above configuration, among the magnetic fluxes that intersect the side portion 33 of the case 30, those with relatively high intensity penetrate the high-resistance region 35. The high-resistance region 35 is a part of the side portion 33 with relatively high electrical resistivity, and eddy currents are less likely to be generated or increased. Therefore, eddy loss generated in the side portion 33 can be suppressed.

[0022] (2) The high-resistance region 35 according to the embodiment may span at least one of the multiple teeth 11 when viewed from the axial direction AD. In this case, the number of locations where eddy loss caused by magnetic flux occurs can be reduced while maintaining the mechanical strength of the case 30.

[0023] (3) In the embodiment, the width W1 of the high-resistance region 35 along the circumferential direction may increase as it extends radially outward. In this case, the area of ​​the high-resistance region 35 can be made as large as possible, and the reduction of eddy loss can be promoted.

[0024] (4) The stator 10 according to this embodiment may be composed of fractional slots. In this case, the torque constant can be increased, and the rotating electric machine can be made smaller. Furthermore, eddy losses that tend to occur with miniaturization can be reduced by the high-resistance region 35.

[0025] (5) The rotor 20 according to this embodiment may be provided around the outer circumference of the stator 10. That is, the rotating electric machine may be an outer rotor type rotating electric machine. With an outer rotor type rotating electric machine, as it becomes thinner, magnetic flux at the shaft end that generates eddy loss is more likely to occur. However, this eddy loss can also be reduced by the high resistance region 35.

[0026] (6) In this embodiment, the length L of the spoke portion 34 along the axial direction AD may be greater than the width W1 of the spoke portion 34 along the circumferential direction CD. In this case, the second moment of area of ​​the spoke portion 34 along the axial direction AD is increased, while the displacement of the stator 10 tilting relative to the axial direction AD is suppressed. That is, the mechanical strength of the case 30 can be improved.

[0027] (7) The high-resistance region 35 according to the embodiment may be formed of an insulator. In this case, it is possible to prevent foreign matter from entering the stator 10 through the high-resistance region 35. It is also possible to improve the mechanical strength of the side portion 33, such as rigidity.

[0028] The embodiments described above are merely illustrative examples provided to facilitate understanding of the invention. The technical scope of the invention is not limited to the specific technical matters disclosed in the embodiments described above, but also includes various modifications, changes, and alternative technologies that can be easily derived therefrom.

[0029] 1 Motor 10 Stator 11 Teeth 12 Slots 20 Rotor 30 Case 33 Side 34 Spoke 35 High-resistance region

Claims

1. A rotating electric machine comprising: a stator having a plurality of teeth extending radially at circumferential intervals; a rotor rotatably mounted relative to the stator; and a case housing the stator and the rotor, and including a side portion facing the stator in the axial direction, wherein the side portion includes spoke portions and high-resistance regions arranged alternately in the circumferential direction, the high-resistance regions having a higher electrical resistivity than the spoke portions, and, viewed from the axial direction, the high-resistance regions being located between any two of the plurality of teeth.

2. The rotating electric machine according to claim 1, wherein, viewed from the axial direction, the high-resistance region spans at least one of the plurality of teeth.

3. The rotating electric machine according to claim 1 or 2, wherein the width of the high-resistance region along the circumferential direction increases as it extends radially outward.

4. The rotating electric machine according to any one of claims 1 to 3, wherein the stator is composed of fractional slots.

5. The rotating electric machine according to any one of claims 1 to 4, wherein the rotor is provided around the outer circumference of the stator.

6. The rotating electric machine according to any one of claims 1 to 5, wherein the length of the spoke portion along the axial direction is greater than the width of the spoke portion along the circumferential direction.

7. The rotating electric machine according to any one of claims 1 to 6, wherein the high-resistance region is formed by an insulator.

Images