Rotor and switched reluctance motor
By using a rotor core made of a first magnetic material and a second salient pole made of a low-iron-loss material, and joining them with an insulating material stop, the problem of increased hysteresis loss in SR motors is solved, thereby achieving reduced iron loss and cost control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ISUZU MOTORS LTD
- Filing Date
- 2025-11-10
- Publication Date
- 2026-05-19
AI Technical Summary
Traditional switched reluctance motors (SR motors) suffer from increased hysteresis losses due to the fixed polarity of the stator teeth when the rotor rotates. Using low-iron-loss materials results in high costs or reduced torque density.
The rotor core and the first salient pole are formed of a first magnetic material, and the second salient pole is formed of a low iron loss material on the outside. The rotor core and the first salient pole are joined by a stop member of insulating material to prevent the second salient pole from separating.
It reduces rotor iron loss, suppresses cost increases and torque density reduction, and improves rotor structure stability.
Smart Images
Figure CN122068700A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to rotors and switched reluctance motors. Background Technology
[0002] A conventional switched reluctance motor (hereinafter referred to as "SR motor") includes a stator formed into a cylindrical shape by stacking annular electromagnetic steel plates and a rotor that is also formed into a cylindrical shape and disposed radially inside the stator. The stator has a plurality of stator teeth formed on its inner circumference, and the rotor has a plurality of rotor teeth formed on its outer circumference (e.g., Japanese Unexamined Patent Application Publication No. 2018-186592). Summary of the Invention
[0003] The problem to be solved by the present invention
[0004] SR motors generate torque by rotating the rotor in a manner that reduces the magnetic reluctance associated with the coils corresponding to the excitation phase in the coils wound around the stator teeth. Since the polarity of each magnetized stator tooth is fixed, the polarity of each rotor tooth changes depending on the polarity of the stator tooth adjacent to it. As a result, the rotor experiences increased hysteresis losses (so-called iron losses). To address this issue, one approach is to form the rotor using a material with low iron losses; however, such materials tend to increase cost or reduce torque density.
[0005] This disclosure is made in consideration of these points, and the purpose of this disclosure is to reduce iron losses in the rotor while suppressing increases in cost and decreases in torque density.
[0006] The means to solve this problem
[0007] The rotor according to a first aspect of the present disclosure includes: a rotor core rotatably disposed about a rotation axis and formed of a first magnetic material; a plurality of first salient poles formed of the first magnetic material and formed at predetermined intervals on the outer peripheral surface of the rotor core in the circumferential direction; a plurality of second salient poles radially disposed outside the plurality of first salient poles of the rotor core and formed of a second magnetic material having lower iron loss than the first magnetic material; and a stop member formed of an insulating material, the stop member engaging with the first salient poles and the second salient poles.
[0008] The length of the second salient pole in the circumferential direction of the rotor core can decrease as the distance from the outer circumferential surface of the rotor core increases, and the stop can engage with the surface of the second salient pole along the radial direction of the rotor core.
[0009] The first salient electrode may have a first protrusion, which is wedge-shaped and formed on a surface that contacts the second salient electrode. The second salient electrode may have a concave portion, which is wedge-shaped and formed on a surface that contacts the first salient electrode. The concave portion of the second salient electrode may be fitted to the first protrusion of the first salient electrode.
[0010] The first salient electrode may have a recess that is wedge-shaped and formed on a surface that contacts the second salient electrode. The second salient electrode may have a first protrusion that is wedge-shaped and formed on a surface that contacts the first salient electrode. The first protrusion of the second salient electrode may be fitted into the recess of the first salient electrode.
[0011] The stop can be configured to contact: (i) two opposing surfaces of adjacent first salient poles in the first salient poles; (ii) two opposing surfaces of adjacent second salient poles in the second salient poles, radially disposed outside the first salient poles; and (iii) the outer peripheral surface between adjacent first salient poles.
[0012] The stop can fill the space between adjacent first salient poles and the space between adjacent second salient poles.
[0013] In the first salient pole, a wedge-shaped second protrusion may be formed on a surface along the radial direction of the rotor core, and a stop member may engage with the second protrusion.
[0014] The further the second protrusion is from the top surface of the first salient pole, the more the second protrusion can protrude in the circumferential direction of the rotor core, and the second protrusion can be formed such that the point that protrudes the most in the circumferential direction of the rotor core is positioned closest to the rotor core.
[0015] The lengths of the first convex portion and the concave portion in the circumferential direction of the rotor core are formed such that they increase as the first convex portion and the concave portion move away from the rotor core.
[0016] A switched reluctance motor according to a second aspect of this disclosure includes: a rotor; and a stator, wherein the rotor includes: a rotor core rotatably disposed about a rotation axis and formed of a first magnetic material; a plurality of first salient poles formed of the first magnetic material and formed at predetermined first intervals on the outer peripheral surface of the rotor core in the circumferential direction; a plurality of second salient poles radially disposed outside the plurality of first salient poles of the rotor core and formed of a second magnetic material having lower iron loss than the first magnetic material; and a stop member formed of an insulating material, the stop member engaging with the first and second salient poles, and the stator includes: a stator core disposed on the outer diameter side of the rotor; and teeth formed at predetermined second intervals on the inner peripheral surface of the stator core in the circumferential direction, each tooth having a coil of one phase wound around it among a plurality of phase coils.
[0017] Effects of the present invention
[0018] According to this disclosure, it is possible to reduce rotor iron loss while suppressing cost increases and torque density reduction. Attached Figure Description
[0019] Figure 1 This is a diagram showing an overview of motor 1.
[0020] Figure 2 This is an enlarged view of part P of the cross-sectional view of rotor 3.
[0021] Figure 3 This is a view showing the stop 23 that fills the space between adjacent salient poles 20. Detailed Implementation
[0022] <Overview of Motor 1>
[0023] Figure 1 This is a diagram showing an overview of motor 1. Figure 1 This is a sectional view taken along a plane perpendicular to the axial direction of the rotation shaft 2 of motor 1. Motor 1 is a switched reluctance motor (SR motor) and includes a rotation shaft 2, a rotor 3, and a stator 4.
[0024] The rotor 3 is located outside the rotating shaft 2 and inside the stator 4, and includes a rotor core 10, multiple salient poles 20, and multiple stop members 23. Figure 1 In the figure, only one of the plurality of salient poles 20 is indicated by a reference numeral, and only the stop 23 that contacts the salient pole 20 indicated by the reference numeral is indicated by a reference numeral. The rotor core 10 is rotatably mounted along the rotation direction (circumferential direction) of the rotation axis 2 and is formed into a cylindrical shape by stacking, for example, annular magnetic material in the axial direction. The salient pole 20 has a first salient pole 21 and a second salient pole 22, and protrudes radially outward from the outer periphery of the rotor core 10. The salient pole 20 is formed of magnetic material, and the first salient pole 21 is integrally formed with the rotor core 10. The stop 23 is formed of insulating material and engages with the first salient pole 21 and the second salient pole 22.
[0025] The stator 4 is located outside the rotor 3 and includes a stator core 30, multiple teeth 40, and multiple coils 50. Figure 1 In the figure, only one of the multiple teeth 40 is indicated by the reference numerals and only one of the multiple coils 50 is indicated by the reference numerals.
[0026] The stator core 30 is disposed outside the rotor 3 and is formed into a cylindrical shape by stacking, for example, annular magnetic material in the axial direction. Teeth 40 are formed of magnetic material and are formed at predetermined intervals on the inner circumferential surface of the stator core 30 in the circumferential direction. The predetermined interval refers to the equal spacing of the plurality of teeth 40 in the circumferential direction. One phase coil 50 of the plurality of phase coils 50 is wound around its respective tooth 40. Figure 1 The figure shows six phases, namely phase A, phase B, phase C, phase D, phase E and phase F, as multiple phases, and the coil 50 of phase A is wound around the tooth 40 indicated by the reference numerals.
[0027] Motor 1 generates torque by rotating rotor 3 in a manner that reduces the magnetic reluctance associated with the coil 50 of the coil 50 wound around the teeth 40, which corresponds to the excitation phase (the phase with high magnetic reluctance). In motor 1, drive circuit (not shown) excites the phase with high magnetic reluctance that changes with the rotation of rotor 3, thereby allowing rotor 3 to continue rotating.
[0028] In motor 1, iron losses (hysteresis losses, eddy current losses) occur because an alternating magnetic field is generated in rotor 3 and stator 4 due to the rotation of rotor 3. In stator 4, since the polarity (S pole or N pole) of each tooth 40 is fixed, hysteresis losses occur due to the repetition of unmagnetized and magnetized states. On the other hand, in rotor 3, the polarity of the salient pole 20 changes in response to the polarity of the adjacent tooth 40, resulting in hysteresis losses caused by repeated S pole magnetization and N pole magnetization states. This hysteresis loss is greater than the hysteresis loss occurring in stator 4. Furthermore, since the frequency of the alternating magnetic field of rotor 3 is higher than the frequency of the alternating magnetic field of stator 4, the iron losses of rotor 3 are greater than those of stator 4.
[0029] To address the aforementioned problems, one approach is to form the rotor 3 from a low-iron-loss material, such as thin silicon steel sheets (e.g., 100 μm or less thick), amorphous metals, or powdered materials in which the surface of each metal particle is coated with resin. However, thin silicon steel sheets and amorphous metals are more expensive than conventional silicon steel sheets (which are not thin) used to form the conventional rotor 3 and stator 4. Furthermore, the rotor 3 formed from powdered materials lacks sufficient strength to overcome the forces generated during rotation, making it difficult to increase the rotational speed of the rotor 3. Additionally, since low-iron-loss materials have a lower saturation flux density than conventional materials, they can reduce torque density.
[0030] Therefore, the rotor 3 includes a first salient pole 21 formed on the outer peripheral surface of the rotor core 10 and made of a conventional material, and a second salient pole 22 radially disposed outside the first salient pole of the rotor core 10 and formed of a low-iron-loss material. With this structure, iron loss can be suppressed because the rotor 3 has a second salient pole 22 formed of a low-iron-loss material at a location where iron loss is high (where the teeth 40 and the salient pole 20 are close to each other). Furthermore, in the rotor 3, since the rotor core 10 and the first salient pole 21 are formed of conventional materials, the increase in cost and the decrease in torque density can be suppressed compared to the case where the entire rotor 3 is formed of a low-iron-loss material. Moreover, since the stop member 23 engages with the first salient pole 21 and the second salient pole 22, separation of the second salient pole 22 from the first salient pole 21 can be prevented even when centrifugal force and magnetic stress from the rotation of the rotor 3 act on the second salient pole 22. The configuration of the rotor 3 will be described in detail below.
[0031] <Configuration of Rotor 3>
[0032] like Figure 1 As shown, the rotor 3 includes a rotor core 10, a plurality of salient poles 20, and a plurality of stops 23. Each salient pole 20 has a first salient pole 21 and a second salient pole 22. The stops 23 are disposed between adjacent salient poles 20. The rotor core 10 is rotatably disposed about a rotation axis 2 and is formed of a first magnetic material. The first magnetic material is, for example, a conventional material such as a thin silicon steel sheet.
[0033] The first salient pole 21 is formed of a first magnetic material and is formed at predetermined intervals on the outer peripheral surface of the rotor core 10 in the circumferential direction. The predetermined interval refers to the spacing between the plurality of first salient poles 21 formed at equal intervals in the circumferential direction of the rotor core 10. The first salient pole 21 protrudes radially outward from the outer peripheral surface of the rotor core 10, and a wedge-shaped protrusion is formed on the radial surface and its top surface. The rotor core 10 and the first salient pole 21 are integrally formed. As described above, by including the rotor core 10 and the first salient pole 21 formed of the first magnetic material, the rotor 3 can suppress the increase in cost and the decrease in torque density.
[0034] The second salient pole 22 is radially disposed outside the first salient pole 21 of the rotor core 10, and is formed of a second magnetic material having lower iron loss than the first magnetic material. The second magnetic material is a low-iron-loss material such as thin silicon steel sheet, amorphous metal, or powder material. The second salient pole 22 contacts the top surface of the first salient pole 21, and a wedge-shaped recess is formed on the surface in contact with the top surface. Because the second salient pole 22 is configured in this way, the rotor 3 can have the second salient pole 22, formed of a low-iron-loss material, disposed at a location where the teeth 40 and the salient pole 20 are close to each other and where there is high iron loss. As a result, the rotor 3 can suppress iron loss.
[0035] The stop member 23 is formed of an insulating material and engages with the first salient pole 21 and the second salient pole 22. The insulating material forming the stop member 23 is non-magnetic and insulating, and is, for example, a ceramic or resin material. The stop member 23 engages with the two first salient poles 21 and the two second salient poles 22 that are in contact with each other in the circumferential direction of the rotor core 10. By configuring the stop member 23 in this way, even when the centrifugal force and magnetic stress from the rotation of the rotor 3 act on the second salient pole 22, separation of the second salient pole 22 from the first salient pole 21 can be prevented. The configuration of the first salient pole 21, the second salient pole 22 and the stop member 23 will be described in detail below.
[0036] Figure 2 yes Figure 1 The image shows an enlarged view of portion P of the cross-sectional view of the rotor 3. In the following description, the plurality of salient poles 20 included in the rotor 3 will be described primarily. Figure 2 The configuration of the salient pole 20a shown and the plurality of stops 23 included in the rotor 3 Figure 2 The stop member 23a is configured as shown. The salient pole 20, which is different from the salient pole 20a, is configured the same as the salient pole 20a, and the stop member 23, which is different from the stop member 23a, is configured the same as the stop member 23a.
[0037] like Figure 2 As shown, in the first salient pole 21a, a wedge-shaped first protrusion 211a is formed on the surface S1a that contacts the second salient pole 22a. Surface S1a is the top surface of the first salient pole 21a. In the second salient pole 22a, a wedge-shaped recess 222a is formed on the surface S2a that contacts the first salient pole 21a, and the recess 222a is fitted to the first protrusion 211a. The lengths of the first protrusion 211a in the circumferential direction of the rotor core 10 and the lengths of the recess 222a in the circumferential direction of the rotor core 10 are formed such that the further away from the rotor core 10 in the radial direction, the longer the recess 222a becomes. With the above configuration, even when the centrifugal force and magnetic stress from the rotation of the rotor 3 act on the second salient pole 22, it is difficult for the second salient pole 22 to separate from the first salient pole 21a.
[0038] In the first salient pole 21a, a wedge-shaped second protrusion is formed on the surface along the radial direction of the rotor core 10, and the stop member 23 engages with the second protrusion. Specifically, in the first salient pole 21a, a wedge-shaped second protrusion 213a is formed on the surface S3a, and a wedge-shaped second protrusion 214a is formed on the surface S4a.
[0039] The second protrusion 213a is formed as an end portion of the rotor core 10 in the radial direction excluding surface S3a, and the second protrusion 214a is formed as an end portion of the rotor core in the radial direction excluding surface S4a. The further the second protrusion 213a and the second protrusion 214a are from the top surface of the first salient pole 21, the more the second protrusion 213a and the second protrusion 214a protrude in the circumferential direction of the rotor core 10. The second protrusion 213a and the second protrusion 214a can be formed such that the point that protrudes the most in the circumferential direction of the rotor core 10 (i.e., the distal end) is located closest to the rotor core 10 in the radial direction.
[0040] The stop 23a engages with the second protrusion 213a, and the stop 23c engages with the second protrusion 214a. With the above configuration, even when the centrifugal force and magnetic stress from the rotation of the rotor 3 act on the stop 23, the stop 23 can be effectively prevented from dislodging outward in the radial direction of the rotor core 10.
[0041] The second salient pole 22a is formed such that the circumferential length of the rotor core 10 decreases as it moves away from the outer peripheral surface of the rotor core 10. Specifically, the second salient pole 22a has a tapered shape. A stop member 23a engages with the surface S5a of the second salient pole 22a radially along the rotor core 10, and a stop member 23c engages with the surface S6a of the second salient pole 22a radially along the rotor core 10. With this configuration, even when centrifugal force and magnetic stress from the rotation of the rotor 3 act on the second salient pole 22, separation of the second salient pole 22 from the first salient pole 21 can be effectively prevented.
[0042] The stop 23 is configured to contact: (i) two facing surfaces of adjacent first convex poles 21; (ii) two radially disposed outside the first convex poles 21 and facing each other; and (iii) the outer peripheral surface between adjacent first convex poles 21. For example, the two facing surfaces of adjacent first convex poles 21 are surface S3a of first convex pole 21a and surface S4b of first convex pole 21b. The two facing surfaces of adjacent second convex poles 22 are, for example, surface S5a of second convex pole 22a and surface S6b of second convex pole 22b. The outer peripheral surface between adjacent first convex poles 21 is, for example, outer peripheral surface R.
[0043] For example, such as Figure 2As shown, the stop member 23a is configured to contact surfaces S3a, S4b, S5a, S6b, and an outer peripheral surface R, and has a U-shaped cross-section perpendicular to the axial direction of the rotation axis 2. In the above configuration, the stop member 23a includes recesses formed on the surfaces that contact surfaces S3a and S4b. These recesses fit into second protrusions 213a and wedge-shaped second protrusions 214b formed on the surface of the first salient pole 21b along the radial direction of the rotor core 10. As a result, even when centrifugal force and magnetic stress from the rotation of the rotor 3 act on the stop member 23a, the stop member 23a can be effectively prevented from dislodging outward in the radial direction of the rotor core 10.
[0044] Figure 1 and Figure 2 The stop 23 shown has a U-shaped cross-section perpendicular to the axial direction of the rotation axis 2, but this configuration is not limiting. The stop 23 can be configured to fill the space between adjacent first salient poles 21 and between adjacent second salient poles 22. Figure 3 This is a view showing the stop 23 configured to fill the space between adjacent salient poles 20. Figure 3 The motor 1 shown is Figure 1 The motor 1 shown differs in the shape of the stop 23, but is otherwise identical. For example... Figure 3 As shown, the stop 23a can be configured to fill the space between adjacent first salient poles 21a and 21b, as well as the space between second salient poles 22a and 22b. This configuration increases the rigidity of the stop 23, making it easier to form the stop 23 using an insulating material with low strength.
[0045] <First Variation>
[0046] The above description illustrates an example of a 10-salient-pole, 12-slot SR motor as motor 1, but this embodiment is not limited to this. Motor 1 can be an SR motor with a different number of poles and slots, such as an 8-pole, 12-slot SR motor.
[0047] <Second Variation>
[0048] The above description illustrates an example of a configuration where the first salient pole 21 has a wedge-shaped protrusion on the surface contacting the second salient pole 22, and the second salient pole 22 has a wedge-shaped recess on the surface contacting the first salient pole 21. However, this embodiment is not limited to this. The first salient pole 21 may have a wedge-shaped recess formed on the surface contacting the second salient pole 22, and the second salient pole 22 may have a wedge-shaped protrusion formed on the surface contacting the first salient pole 21. The protrusion of the second salient pole 22 can be fitted into the recess of the first salient pole 21. Using this structure, the rotor 3 can be... Figure 1The rotor 3 shown has a large second salient pole 22 formed of a low-iron-loss material. As a result, the iron loss generated by the rotation of the rotor 3 can be reduced more easily.
[0049] <The effect of rotor 3>
[0050] As described above, the rotor 3 includes: a rotor core 10, rotatably disposed about a rotation axis 2 and formed of a first magnetic material; a first salient pole 21, formed of the first magnetic material and formed at predetermined intervals on the outer peripheral surface of the rotor core 10 in the circumferential direction; a second salient pole 22, radially disposed outside the first salient pole 21 of the rotor core 10 and formed of a second magnetic material having lower iron loss than the first magnetic material; and a stop member 23, formed of an insulating material and engaged with the first salient pole 21 and the second salient pole 22.
[0051] Since the rotor 3 is configured as described above, the second salient pole 22, formed of a low-iron-loss material, can be positioned close to the tooth 40 and the salient pole 20, where iron loss may increase, thus the rotor 3 can suppress iron loss. Furthermore, since the rotor core 10 and the first salient pole 21 can be formed of conventional materials that are less expensive and have a higher saturation magnetic flux density than low-iron-loss materials, the increase in cost and the decrease in torque density can be suppressed. Moreover, because the stop member 23 engages with the first salient pole 21 and the second salient pole 22, even when centrifugal force and magnetic stress from the rotation of the rotor 3 act on the second salient pole 22, separation of the second salient pole 22 from the first salient pole 21 can be prevented.
[0052] This disclosure has been described based on exemplary embodiments. The technical scope of this disclosure is not limited to the scope described in the above embodiments, and various changes and modifications can be made within the scope of this disclosure. For example, all or part of the apparatus may be configured with any functionally or physically distributed or integrated units. Furthermore, new exemplary embodiments resulting from any combination of embodiments are included in the exemplary embodiments. Moreover, the effects of new exemplary embodiments resulting from combinations also have the effects of the original exemplary embodiments.
[0053] [Symbol Description]
[0054] 1. Motor
[0055] 2 Rotation axis
[0056] 3 rotors
[0057] 4. Stator
[0058] 10 Rotor core
[0059] 20 salient pole
[0060] 20a salient pole
[0061] 20b salient pole
[0062] 21 First salient pole
[0063] 21a First Salient Pole
[0064] 21b First salient pole
[0065] 22 Second salient pole
[0066] 22a Second salient pole
[0067] 22b Second salient pole
[0068] 23 Stop components
[0069] 23a Stop
[0070] 23c Stop
[0071] 30 stator core
[0072] 40 teeth
[0073] 50 coils
[0074] 211a first convex part
[0075] 213a Second convex part
[0076] 214a Second convex part
[0077] 214b Second convex part
[0078] 222a recess
Claims
1. A rotor, comprising: The rotor core is rotatably mounted about a rotating shaft and is formed of a first magnetic material; Multiple first salient poles, formed of the first magnetic material, are formed at predetermined intervals on the outer peripheral surface of the rotor core in the circumferential direction of the rotor core; Multiple second salient poles are radially disposed outside the multiple first salient poles of the rotor core and are formed of a second magnetic material having lower iron loss than the first magnetic material; as well as A stop member, formed of an insulating material, engages with the first salient pole and the second salient pole.
2. The rotor according to claim 1, wherein, The length of the second salient pole in the circumferential direction of the rotor core decreases as the distance from the outer circumferential surface of the rotor core increases, and The stop member engages with the surface of the second salient pole along the radial direction of the rotor core.
3. The rotor according to claim 1 or 2, wherein, The first salient electrode has a first convex portion, which is wedge-shaped and formed on the surface that contacts the second salient electrode. The second convex electrode has a recess, which is wedge-shaped and formed on the surface in contact with the first convex electrode. The recess of the second salient electrode is fitted to the first salient electrode.
4. The rotor according to claim 1 or 2, wherein, The first convex electrode has a recess, which is wedge-shaped and formed on the surface that contacts the second convex electrode. The second salient electrode has a first salient portion, which is wedge-shaped and formed on the surface in contact with the first salient electrode. The first protrusion of the second salient electrode is fitted into the recess of the first salient electrode.
5. The rotor according to claim 1, wherein, The stop is configured to contact: (i) two opposing surfaces of adjacent first salient poles in the first salient poles; (ii) two opposing surfaces of adjacent second salient poles in the second salient poles, radially disposed outside the first salient poles; and (iii) the outer peripheral surface between the adjacent first salient poles.
6. The rotor according to claim 5, wherein, The stopper fills the space between the adjacent first salient poles and the space between the adjacent second salient poles.
7. The rotor according to claim 1, wherein, In the first salient pole, a wedge-shaped second protrusion is formed on a surface along the radial direction of the rotor core, and The stop member engages with the second protrusion.
8. The rotor according to claim 7, wherein, The further the second protrusion is from the top surface of the first salient pole, the more the second protrusion protrudes in the circumferential direction of the rotor core, and the second protrusion is formed such that the point that protrudes the most in the circumferential direction of the rotor core is located closest to the rotor core.
9. The rotor according to claim 3, wherein, The length of the first protrusion in the circumferential direction of the rotor core and the length of the concave portion in the circumferential direction of the rotor core are formed to increase as the first protrusion and the concave portion move away from the rotor core.
10. A switched reluctance motor, comprising: Rotor; as well as Stator, among which, The rotor includes: The rotor core is rotatably mounted about a rotating shaft and is formed of a first magnetic material; Multiple first salient poles, formed of the first magnetic material, are formed on the outer peripheral surface of the rotor core at predetermined first intervals in the circumferential direction of the rotor core; A plurality of second salient poles are radially disposed outside the plurality of first salient poles of the rotor core, and are formed of a second magnetic material having lower iron loss than the first magnetic material; and A stop member, formed of an insulating material, engages with the first salient pole and the second salient pole, and The stator includes: Stator core, disposed on the outer diameter side of the rotor; and Teeth are formed at predetermined second intervals on the inner circumferential surface of the stator core in the circumferential direction, and each tooth has a coil of one phase wound around it among a plurality of phase coils.