CN113472169A

CN113472169A - Motor

Info

Publication number: CN113472169A
Application number: CN202110324086.3A
Authority: CN
Inventors: 荒尾侑典; 一圆明
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2020-03-31
Filing date: 2021-03-26
Publication date: 2021-10-01
Also published as: JP2021164262A

Abstract

The motor includes a stator and a pair of rotors that rotate about a central axis and are stacked in an axial direction. The rotor has: an inner iron core portion; a first outer core portion; a second outer core portion arranged at a position different from the first outer core portion in a circumferential direction; a first magnet disposed radially outward of the first outer core portion; and a second magnet disposed radially between the inner core portion and the second outer core portion. The second magnet has a portion located radially outward in a cross-sectional view perpendicular to the central axis as being circumferentially distant from a center line passing through a center of the circumference and the central axis of the second outer core portion. First magnetic pole portions formed by the first outer core portions and the first magnets arranged in the radial direction and second magnetic pole portions formed by the second magnets and the second outer core portions arranged in the radial direction are alternately arranged in the circumferential direction. One first magnetic pole portion and the other second magnetic pole portion of the pair of rotors are arranged in an axial direction, and have the same circumferential position.

Description

Motor

Technical Field

The present invention relates to a motor.

Background

The motor has a rotor and a stator. The motor can suppress vibration or noise by reducing cogging torque. For example, as described in patent document 1, in a conventional motor, a step skew (stage skew) is provided for a rotor and a stator to reduce a cogging torque.

Patent document 1: japanese laid-open patent publication No. 2004-159492

If the skew is provided, the manufacturing process of the motor increases, and the productivity decreases.

Disclosure of Invention

An object of the present invention is to provide a motor capable of reducing cogging torque without providing skew.

One embodiment of the present invention is a motor including: a cylindrical stator; and a pair of rotors that are positioned radially inward of the stator, rotate about a central axis, and are stacked in an axial direction. The rotor has: an inner iron core portion; a first outer core portion located radially outward of the inner core portion; a second outer core portion located radially outward of the inner core portion and arranged at a position different from the first outer core portion in a circumferential direction; a first magnet disposed radially outward of the first outer core portion; and a second magnet disposed radially between the inner core portion and the second outer core portion. The second magnet has a portion located radially outward in a cross-sectional view perpendicular to the center axis as being circumferentially distant from a center line passing through a circumferential center of the second outer core portion and the center axis. First magnetic pole portions formed by the first outer core portions and the first magnets arranged in the radial direction and second magnetic pole portions formed by the second magnets and the second outer core portions arranged in the radial direction are alternately arranged in the circumferential direction. The first magnetic pole portion of one of the pair of rotors and the second magnetic pole portion of the other of the pair of rotors are arranged in an axial direction, and have the same circumferential position.

According to the motor of one embodiment of the present invention, the cogging torque can be reduced without providing a skew.

Drawings

Fig. 1 is a sectional view schematically showing a motor of the present embodiment.

Fig. 2 is a perspective view schematically showing a rotor of the motor of the present embodiment.

Fig. 3 is a sectional view showing the III-III section of fig. 1.

Fig. 4 is a sectional view showing the section IV-IV of fig. 1.

Fig. 5 is a schematic diagram showing an electric power steering apparatus having the motor of the present embodiment.

Fig. 6 is a cross-sectional view showing a part of a rotor of a motor according to a modification of the present embodiment.

Fig. 7 is a cross-sectional view showing a part of a rotor of a motor according to a modification of the present embodiment.

Description of the reference symbols

10: a motor; 20: a rotor; 20A: a first rotor; 20B: a second rotor; 24: an inner iron core portion; 25: a first outer core portion; 26: a second outer core portion; 27: a first magnet; 28: a second magnet; 28A: a side magnet; 28B: a magnet on the other side; 30: a stator; 51: a first magnetic pole portion; 52: a second magnetic pole portion; c: a centerline; j: a central axis; θ 1: one side in the circumferential direction; θ 2: the other side in the circumferential direction.

Detailed Description

A motor 10 according to an embodiment of the present invention will be described with reference to the drawings. As shown in fig. 1, in the present embodiment, the direction in which the central axis J of the motor 10 extends is simply referred to as "axial direction". In the present embodiment, the axial direction is the vertical direction. The upper side (+ Z) corresponds to one axial side, and the lower side (-Z) corresponds to the other axial side. In addition, the radial direction centered on the central axis J is simply referred to as the "radial direction". In the radial direction, a direction approaching the central axis J is referred to as a radially inner side, and a direction away from the central axis J is referred to as a radially outer side. The circumferential direction around the central axis J is simply referred to as "circumferential direction". In the present embodiment, as shown in fig. 3 and 4, when viewed in the axial direction, a predetermined rotational direction in the circumferential direction is referred to as a circumferential one side θ 1, and a rotational direction opposite to the predetermined rotational direction is referred to as a circumferential other side θ 2. Specifically, in a plan view of the rotor 20, a counterclockwise direction about the central axis J is referred to as a circumferential one side θ 1, and a clockwise direction about the central axis J is referred to as a circumferential other side θ 2. The vertical direction, the upper side, and the lower side are only names for describing the relative positional relationship of the respective parts, and the actual arrangement relationship and the like may be an arrangement relationship other than the arrangement relationship and the like indicated by these names.

As shown in fig. 1, the motor 10 of the present embodiment includes a cylindrical stator 30 centered on a central axis J, a rotor 20 positioned radially inward of the stator 30, a housing 11, and a plurality of

bearings

15 and 16. The motor 10 is an inner rotor type motor. The rotor 20 rotates about the central axis J with respect to the stator 30.

The housing 11 houses the rotor 20 and the stator 30. The housing 11 has a cylindrical shape extending in the axial direction. The housing 11 has a peripheral wall 11a, a top wall 11b, a bottom wall 11c, and a bearing holding wall 11 d. The peripheral wall 11a is cylindrical and extends in the axial direction. The top wall 11b closes the opening of the upper side of the peripheral wall 11 a. The bottom wall 11c closes the opening on the lower side of the peripheral wall 11 a. The bottom wall 11c holds the bearing 16. The bearing holding wall 11d is fixed to the peripheral wall 11 a. The bearing holding wall portion 11d holds the bearing 15.

The rotor 20 is provided in a pair aligned in the axial direction. The pair of rotors 20 are stacked in the axial direction. As shown in fig. 1 and 2, the pair of rotors 20 includes a first rotor 20A and a second rotor 20B arranged at a position different from the first rotor 20A in the axial direction. In the present embodiment, the first rotor 20A is located above the second rotor 20B, and the second rotor 20B is located below the first rotor 20A.

Rotor 20 includes shaft 21, rotor core 22, a plurality of magnets 23 located at the outer end of rotor core 22 in the radial direction and arranged in a circumferential direction, groove portions 29, and holder 40. The rotor core 22 has an inner core portion 24, a first outer core portion 25, and a second outer core portion 26. The plurality of magnets 23 include a first magnet 27 and a second magnet 28. That is, the rotor 20 includes an inner core portion 24, a first outer core portion 25, a second outer core portion 26, a first magnet 27, and a second magnet 28.

The shaft 21 has a cylindrical shape extending in the axial direction around the central axis J. The shaft 21 may be cylindrical. The shaft 21 is supported by the plurality of

bearings

15 and 16 so as to be rotatable about the central axis J. The plurality of

bearings

15, 16 are arranged at intervals in the axial direction and supported by the housing 11. That is, the shaft 21 is supported by the housing 11 via the plurality of

bearings

15 and 16.

Rotor core 22 has a cylindrical shape extending in the axial direction. Rotor core 22 is made of a magnetic material (ferromagnetic material), and is made of iron, steel, stainless steel, or the like, for example. Rotor core 22 is formed by laminating a plurality of electromagnetic steel plates in the axial direction. Rotor core 22 has an outer diameter larger than shaft 21. The axial length of rotor core 22 is smaller than that of shaft 21. The inner peripheral surface of rotor core 22 is fixed to the outer peripheral surface of shaft 21. Rotor core 22 is fixed to shaft 21 by press fitting, bonding, or the like. The rotor core 22 is located between the pair of

bearings

15, 16 in the axial direction.

As shown in fig. 3 and 4, the inner core portion 24 constitutes a radially inner portion in the rotor core 22. The inner core portion 24 has a cylindrical shape extending in the axial direction around the center axis J. The inner core portion 24 has a shaft hole 24a and a lightening hole 24 b. The shaft hole 24a is located on the center axis J and penetrates the inner core portion 24 in the axial direction. The shaft 21 is inserted into the shaft hole 24 a. The lightening holes 24b penetrate the inner core portion 24 in the axial direction. The lightening holes 24b are provided in plurality at intervals from each other in the circumferential direction. The plurality of lightening holes 24b are arranged at equal intervals in the circumferential direction. According to the present embodiment, the weight reduction of the rotor 20, the reduction of the material cost, and the like can be achieved by providing the lightening holes 24 b.

The first outer core portion 25 constitutes a part of a radially outer portion of the rotor core 22. The first outer core portion 25 is located radially outward of the inner core portion 24. The first outer core portions 25 protrude radially outward from the inner core portions 24 at a part in the circumferential direction. The first outer core portions 25 are provided in plurality at intervals from each other in the circumferential direction. In the present embodiment, four first outer core portions 25 are provided at equal intervals in the circumferential direction on each rotor 20.

The second outer core portion 26 constitutes a part of a radially outer portion in the rotor core 22. The second outer core portions 26 are located radially outward of the inner core portions 24, and are arranged at positions different from the first outer core portions 25 in the circumferential direction. The second outer core portion 26 is disposed at a position radially outward away from the inner core portion 24 at a part in the circumferential direction. The second outer core portions 26 are provided in plurality at intervals from each other in the circumferential direction. In the present embodiment, four second outer core portions 26 are provided at equal intervals in the circumferential direction on each rotor 20. In each rotor 20, the first outer core portions 25 and the second outer core portions 26 are alternately arranged in the circumferential direction.

At least one of the first outer core portion 25 and the second outer core portion 26 is integral with the inner core portion 24. In the present embodiment, the first outer core portion 25 is integrated with the inner core portion 24. According to the present embodiment, the number of components of the rotor 20 can be reduced, and the manufacturing process and manufacturing cost of the motor 10 can be reduced. The configurations of the first outer core portion 25 and the second outer core portion 26 other than the above are described later.

The magnet 23 is a permanent magnet. Each magnet 23 is fixed to the outer periphery of rotor core 22 by a holder 40, an adhesive, or the like.

The first magnet 27 is disposed radially outward of the first outer core portion 25. The first magnet 27 is disposed on the radially outer surface of the rotor 20 and exposed radially outward. The first outer core portion 25 and the first magnet 27 overlap each other when viewed from the radial direction. The first magnetic pole portion 51 is constituted by the first outer core portion 25 and the first magnet 27 arranged in the radial direction. That is, the rotor 20 has the first magnetic pole portion 51. The first magnetic pole 51 is a magnetic pole of Surface Magnet type (SPM). The first magnetic pole portions 51 are provided in plurality at intervals in the circumferential direction. In the present embodiment, four first magnetic pole portions 51 are provided at equal intervals in the circumferential direction on each rotor 20.

The first magnet 27 has a plate shape, and the pair of plate surfaces face in the radial direction. The first magnet 27 has a radially outer surface 27a facing radially outward, a radially inner surface 27b facing radially inward, and a first side surface 27c facing circumferentially. The radially outer surface 27a is a convex curved surface bulging radially outward. The radially inner surface 27b is flat and extends in a direction perpendicular to the radial direction. The first magnet 27 is provided with a pair of first side surfaces 27 c. Each first side surface 27c is a flat surface extending in a direction perpendicular to the circumferential direction. Each first side surface 27c is continuous with a circumferential end of the radially outer surface 27a and a circumferential end of the radially inner surface 27 b. According to the present embodiment, by providing the pair of first side surfaces 27c on the first magnet 27, formation of sharp corner portions at both ends in the circumferential direction of the first magnet 27 is suppressed, so that corner loss of the first magnet 27 can be suppressed, and the structure of the first magnet 27 can be simplified.

As shown in fig. 3 and 4, the first side surface 27c has a length of 1mm or more in a cross-sectional view perpendicular to the central axis J. If the length of the first side surface 27c is 1mm or more, the angular defect of the first magnet 27 is more stably suppressed.

The second magnet 28 is disposed radially between the inner core portion 24 and the second outer core portion 26. The second magnet 28 and the second outer core portion 26 overlap each other when viewed from the radial direction. The second magnetic pole portion 52 is constituted by the second magnet 28 and the second outer core portion 26 arranged in the radial direction. That is, the rotor 20 has the second magnetic pole portion 52. The second magnetic pole portion 52 is a buried Magnet type (IPM) magnetic pole portion. The second magnetic pole portions 52 are provided in plurality at intervals in the circumferential direction. In the present embodiment, four second magnetic pole portions 52 are provided at equal intervals in the circumferential direction on each rotor 20.

The second magnet 28 has a plate shape, and a pair of plate surfaces face in the radial direction. The second magnet 28 has a radially outer surface 28a facing radially outward, a radially inner surface 28b facing radially inward, and a second side surface 28c facing circumferentially. The second magnet 28 is provided with a plurality of second side surfaces 28 c. Each second side surface 28c is connected to a circumferential end of the radially outer side surface 28a and a circumferential end of the radially inner side surface 28 b. The configuration of the second magnet 28 other than the above will be described later.

As shown in fig. 2, the first magnetic pole portions 51 and the second magnetic pole portions 52 are alternately arranged in the circumferential direction. One first magnetic pole portion 51 and the other second magnetic pole portion 52 of the pair of rotors 20 are arranged in an axial direction, and have the same circumferential position. That is, the circumferential positions of the first magnetic pole portions 51 of the first rotor 20A and the second magnetic pole portions 52 of the second rotor 20B are the same as each other, and the circumferential positions of the second magnetic pole portions 52 of the first rotor 20A and the first magnetic pole portions 51 of the second rotor 20B are the same as each other.

More specifically, when viewed from the axial direction, the circumferential center portion of the first magnetic pole portion 51 of the first rotor 20A and the circumferential center portion of the second magnetic pole portion 52 of the second rotor 20B are disposed so as to overlap each other, and the circumferential center portion of the second magnetic pole portion 52 of the first rotor 20A and the circumferential center portion of the first magnetic pole portion 51 of the second rotor 20B are disposed so as to overlap each other. That is, in the present embodiment, the rotor 20 is not biased. In the present embodiment, when viewed from the axial direction, both circumferential end portions of the first magnetic pole portion 51 of the first rotor 20A and both circumferential end portions of the second magnetic pole portion 52 of the second rotor 20B are disposed so as to overlap each other, and both circumferential end portions of the second magnetic pole portion 52 of the first rotor 20A and both circumferential end portions of the first magnetic pole portion 51 of the second rotor 20B are disposed so as to overlap each other. Further, when viewed from the axial direction, both circumferential end portions of the first magnetic pole portion 51 of the first rotor 20A and both circumferential end portions of the second magnetic pole portion 52 of the second rotor 20B may not necessarily be disposed so as to overlap each other, and both circumferential end portions of the second magnetic pole portion 52 of the first rotor 20A and both circumferential end portions of the first magnetic pole portion 51 of the second rotor 20B may not necessarily be disposed so as to overlap each other. That is, the fact that the rotor 20 is not skewed means that the circumferential center portion of the first magnetic pole portion 51 of the first rotor 20A and the circumferential center portion of the second magnetic pole portion 52 of the second rotor 20B overlap each other when viewed from the axial direction.

According to the present embodiment, the waveform of the cogging torque generated in the first rotor 20A and the waveform of the cogging torque generated in the second rotor 20B of the pair of rotors 20 can be generated in opposite phases to each other. That is, the cogging torque of the first rotor 20A and the cogging torque of the second rotor 20B cancel each other out, and the fluctuation width, which is the difference between the maximum value and the minimum value of the waveform of the synthesized cogging torque, can be suppressed to be small. Therefore, the cogging torque of the entire motor 10 can be reduced without providing a skew. The manufacturing processes of the motor 10 are reduced, thereby improving productivity. In addition, torque ripple can be made to be in opposite phases. That is, the torque ripple generated in the first rotor 20A and the torque ripple generated in the second rotor 20B are generated in opposite phases to each other, and therefore they cancel each other out, so that the fluctuation width, which is the difference between the maximum value and the minimum value of the waveform of the combined torque ripple, can be suppressed small. Therefore, according to the present embodiment, the cogging torque can be reduced while suppressing the reduction of the torque caused by applying the skew, and the torque ripple can be reduced. Further, vibration and noise generated by the motor 10 can be reduced.

As shown in fig. 3 and 4, the second magnet 28 has a portion located radially outward as being circumferentially distant from a center line C passing through the center of the second outer core portion 26 in the circumferential direction and the center axis J in a cross-sectional view perpendicular to the center axis J. Specifically, the second magnet 28 is positioned radially outward from the center line C in the circumferential direction, with a portion on one side θ 1 in the circumferential direction (a first magnet 28A described later) and a portion on the other side θ 2 in the circumferential direction (a second magnet 28B described later). According to the present embodiment, since the magnetic flux extending from the radially outer surface 28a of the second magnet 28 toward the stator 30 approaches the center line C as it goes radially outward, the magnetic flux of the second magnet 28 is easily concentrated on the circumferential center portion of the second outer core portion 26. This can suppress the fluctuation width of the waveform of the synthesized cogging torque to be smaller. The vibration or noise of the motor 10 is further reduced, and the motor performance is improved.

In a cross-sectional view perpendicular to the central axis J, the second magnet 28 is arranged in a V-shape or a U-shape. In the present embodiment, the second magnet 28 is disposed in a V-shape or U-shape in the cross-sectional view with the center line C as the center and opening radially outward. The circumferential both ends of the second magnet 28 are located radially outward of the circumferential central portion of the second magnet 28. According to the present embodiment, the magnetic flux extending from the radially outer surface 28a of the second magnet 28 toward the stator 30 can be made to approach the center line C stably as it goes radially outward.

The circumferential both ends of the second magnet 28 are located radially inward of the circumferential both ends of the first magnet 27. Therefore, the function of the second magnetic pole portion 52 of the embedded magnet type can be stably secured while the second magnet 28 is disposed in a V-shape or U-shape.

The second magnet 28 includes a first magnet 28A on one circumferential side θ 1 with respect to the center line C and a second magnet 28B on the other circumferential side θ 2 with respect to the center line C. That is, the one second magnet 28 is composed of the one side magnet 28A and the other side magnet 28B.

The one magnet 28A has a plate shape, and a pair of plate surfaces thereof face in the radial direction. The portion of the radially outer surface 28A of the second magnet 28 that is disposed on the one magnet 28A is located radially outward as it moves away from the center line C toward the one circumferential side θ 1. The portion of the radially inner surface 28b of the second magnet 28 that is disposed on the one magnet 28A is located radially outward as it moves away from the center line C toward the one circumferential side θ 1.

The other magnet 28B has a plate shape, and a pair of plate surfaces thereof face in the radial direction. The portion of the radially outer surface 28a of the second magnet 28 that is disposed on the other magnet 28B is located radially outward as it moves away from the center line C toward the other circumferential side θ 2. The portion of the radially inner surface 28B of the second magnet 28 that is disposed on the other magnet 28B is located radially outward as it moves away from the center line C toward the other circumferential side θ 2.

The one-side magnet 28A and the other-side magnet 28B are arranged in the circumferential direction. The first magnet 28A and the second magnet 28B are arranged apart from each other in the circumferential direction. According to the present embodiment, the second magnet 28 is composed of the one-side magnet 28A and the other-side magnet 28B which are separate from each other. Therefore, the direction of the magnetic flux extending from the portion of the one-side magnet 28A to the stator 30 and the direction of the magnetic flux extending from the portion of the other-side magnet 28B to the stator 30 in the radially outer surface 28A are easily made different from each other. The respective magnetic fluxes extending from the one-side magnet 28A and the other-side magnet 28B to the stator 30 can be made to approach the center line C stably as they go radially outward. In addition, the shapes of the first magnet 28A and the second magnet 28B can be simplified, and the second magnet 28 can be easily manufactured.

The one-side magnet 28A and the other-side magnet 28B have the same shape as each other. According to the present embodiment, the one-side magnet 28A and the other-side magnet 28B can be shared (shared). Therefore, management and assembly of the components are easy.

The N pole of the magnet 28A faces one radial side, and the S pole faces the other radial side. The other magnet 28B has an N pole facing one radial side and an S pole facing the other radial side. In the case where one radial side corresponds to the radially inner side, the other radial side corresponds to the radially outer side. In the case where one radial side corresponds to a radially outer side, the other radial side corresponds to a radially inner side. According to the present embodiment, the magnetic poles of the first magnet 28A and the second magnet 28B are oriented in the same radial direction, and therefore the function of the second magnet 28 is stabilized.

Both circumferential end portions of the radially inner surface of the second outer core portion 26 are positioned radially outward of the circumferential center portion. In other words, the radially inner side surface of the second outer core portion 26 is located radially inward from both end portions toward the central portion in the circumferential direction. According to the present embodiment, the radially outer surface 28a of the second magnet 28, which is in contact with the radially inner surface of the second outer core portion 26, is easily formed into a V-shape, a U-shape, or the like that is open radially outward. Therefore, the magnetic flux extending from the radially outer surface 28a of the second magnet 28 toward the stator 30 can be made to approach the center line C stably as it goes radially outward.

The first outer core portion 25 has a pedestal portion 25 b. The pedestal portion 25b is located at a radially outer end portion of the first outer core portion 25. The pedestal portion 25b contacts the first magnet 27 from the radially inner side, and the dimension of the pedestal portion 25b in the circumferential direction decreases toward the radially outer side. According to the present embodiment, the pedestal portion 25b of the first outer core portion 25 is spaced apart from the circumferentially adjacent second magnets 28 as it goes radially outward. The leakage magnetic flux of the first outer core portion 25 can be suppressed. The circumferential dimension of the pedestal portion 25b is equal to or greater than the circumferential dimension of the first magnet 27. In the present embodiment, the dimension in the circumferential direction of the radially outer end portion of the pedestal portion 25b is the same as the dimension in the circumferential direction of the radially inner end portion of the first magnet 27. According to the present embodiment, the radially inner surface 27b of the first magnet 27 can be stably supported over the entire circumferential region by the pedestal portion 25 b.

The groove portion 29 is recessed radially inward from the radially outer surface of the rotor 20 and extends in the axial direction. In the present embodiment, the groove 29 extends over the entire axial length of the rotor 20 and opens to the upper end surface and the lower end surface of the rotor 20. The groove portions 29 are provided in plurality at intervals in the circumferential direction. In the present embodiment, eight groove portions 29 are provided at equal intervals in the circumferential direction in each rotor 20.

The groove 29 is located between the first magnet 27 and the second magnet 28 adjacent in the circumferential direction. The groove 29 is disposed between the first magnetic pole 51 and the second magnetic pole 52 in the circumferential direction. The groove width in the circumferential direction of at least a part of the groove portion 29 decreases toward the radially outer side. In the present embodiment, the circumferential groove width of the radially inner end portion of the groove portion 29 becomes narrower toward the radially outer side. According to the present embodiment, the later-described holding portions 42 of the retainer 40 disposed in the groove portions 29 are prevented from coming out from the groove portions 29 to the outside in the radial direction.

The holder 40 is made of resin. The holder 40 has a holding portion 42 and a connecting portion 43. The holding portion 42 is disposed in the groove portion 29. The holding portion 42 extends in the axial direction. The plurality of holding portions 42 are provided at intervals from each other in the circumferential direction. The number of the holding portions 42 is the same as the number of the groove portions 29. The holding portion 42 is in contact with the first magnet 27 and the second magnet 28 in the circumferential direction. According to the present embodiment, the first magnet 27 and the second magnet 28 can be pressed in the circumferential direction by the holding portion 42. The first magnet 27 and the second magnet 28 are prevented from moving in the circumferential direction.

The holding portion 42 contacts the first magnet 27 and the second outer core portion 26 from the radially outer side. The holding portion 42 presses the first magnetic pole portion 51 and the second magnetic pole portion 52 from the radial outside. According to the present embodiment, the movement of the first magnet 27, the second magnet 28, and the second outer core portion 26 outward in the radial direction is suppressed by the holding portion 42. This stably improves the rotational strength of the rotor 20 when rotating.

As shown in fig. 1, the connection portion 43 is disposed on an end surface of the rotor 20 facing the axial direction. In the present embodiment, the connection portions 43 are provided on the upper end surface of the first rotor 20A and the lower end surface of the second rotor 20B, respectively. The connecting portion 43 extends in the circumferential direction. The connection portion 43 is, for example, annular with the center axis J as the center. The connecting portion 43 is connected to an axial end of each holding portion 42. That is, the connecting portion 43 is connected to the holding portion 42. The connecting portion 43 and the plurality of holding portions 42 are portions of one member.

The stator 30 is opposed to the rotor 20 with a gap in the radial direction. The stator 30 surrounds the rotor 20 over the entire circumferential range from the radially outer side in the circumferential direction. The stator 30 includes a stator core 31, an insulator 32, and a coil 33.

The stator core 31 is annular with the center axis J as the center. The stator core 31 has a cylindrical shape extending in the axial direction. The stator core 31 surrounds the rotor 20 from the radially outer side. Although not particularly shown, stator core 31 is formed of a plurality of electromagnetic steel plates stacked in the axial direction. Stator core 31 is fixed to the inner circumferential surface of housing 11. The stator core 31 and the housing 11 are fixed by, for example, shrink fitting, press fitting, or the like.

The stator core 31 has a core back 31a and a plurality of teeth 31 b. The core back 31a is cylindrical with the center axis J as the center. The radially outer side surface of the core back 31a is fixed to the inner peripheral surface of the peripheral wall 11 a. Specifically, the core back 31a is fixed to the peripheral wall 11a in a state where the radially outer surface of the core back 31a is in contact with the inner peripheral surface of the peripheral wall 11 a. The teeth 31b project radially inward from the radially inner surface of the core back 31 a. The plurality of teeth 31b are arranged at intervals in the circumferential direction. In the present embodiment, the plurality of teeth 31b are arranged at equal intervals in the circumferential direction. The radially inner surface of each tooth 31b faces the radially outer surface of the rotor 20 with a gap therebetween.

The insulator 32 is attached to the stator core 31. The insulating member 32 is made of an insulating material. The insulator 32 is made of, for example, resin. The insulator 32 is annularly arranged around the central axis J.

The coil 33 is attached to the stator core 31 via an insulator 32. The coil 33 is provided in plurality in a circumferentially aligned manner. The number of coils 33 is the same as the number of teeth 31 b. Each coil 33 is attached to each tooth 31b via an insulator 32. The coil 33 is formed by winding a wire around the teeth 31b via a part of the insulator 32.

The motor 10 of the present embodiment is, for example, a three-phase motor. Three phases are referred to as U phase, V phase and W phase. In the case of a three-phase motor, the U-phase, V-phase, and W-phase coils 33 are each formed of any one of the first, second, and third lead wires.

Next, an example of a device on which the motor 10 of the present embodiment is mounted will be described. In the present embodiment, an example in which the motor 10 is mounted on the electric power steering apparatus 100 will be described.

As shown in fig. 5, the electric power steering apparatus 100 is mounted on a steering mechanism of a wheel of an automobile. The electric power steering apparatus 100 is an apparatus for reducing a steering force by hydraulic pressure. The electric power steering apparatus 100 of the present embodiment includes a motor 10, an oil pump 116, a steering shaft 114, and a control valve 117.

The steering shaft 114 transmits an input from the steering 111 to an axle 113 having wheels 112. The oil pump 116 generates hydraulic pressure in the power cylinder 115. The power cylinder 115 transmits a driving force based on a hydraulic pressure to the axle 113. The control valve 117 controls oil of the oil pump 116. In the electric power steering apparatus 100, the motor 10 is mounted as a drive source of the oil pump 116.

The electric power steering apparatus 100 of the present embodiment includes the motor 10 of the present embodiment. Therefore, the electric power steering apparatus 100 that achieves the same effects as the above-described motor 10 is obtained.

The present invention is not limited to the above-described embodiments, and for example, as described below, structural modifications and the like can be made without departing from the scope of the present invention.

Fig. 6 shows a modification of the motor 10 described in the above embodiment. In this modification, as shown in fig. 6, the second magnet 28 of the rotor 20 is arranged in a U-shape in a cross-sectional view perpendicular to the central axis J. The second magnet 28 includes a first magnet 28A, a second magnet 28B, and an intermediate magnet 28C. The intermediate magnet 28C is located between the first magnet 28A and the second magnet 28B in the circumferential direction. In the illustrated example, the intermediate magnet 28C is located on the center line C in the cross-sectional view. The one-side magnet 28A and the intermediate magnet 28C are arranged so as to be separated from each other in the circumferential direction. The other-side magnet 28B and the intermediate magnet 28C are arranged apart from each other in the circumferential direction. That is, the one-side magnet 28A, the intermediate magnet 28C, and the other-side magnet 28B are arranged apart from each other in the circumferential direction. The intermediate magnet 28C has a plate shape, and a pair of plate surfaces thereof face in the radial direction. The portion of the radially outer surface 28a of the second magnet 28, which is disposed on the intermediate magnet 28C, is flat and extends in a direction perpendicular to the radial direction. The portion of the radially inner surface 28b of the second magnet 28, which is disposed on the intermediate magnet 28C, is flat and extends in a direction perpendicular to the radial direction. The first magnet 28A, the second magnet 28B, and the intermediate magnet 28C have the same shape. The one-side magnet 28A, the other-side magnet 28B, and the intermediate magnet 28C are common members (common products). The intermediate magnet 28C has an N pole facing one radial side and an S pole facing the other radial side, similarly to the first magnet 28A and the second magnet 28B. In this modification as well, the same operational effects as those of the above embodiment are obtained.

In the above embodiment, the configuration is exemplified in which the radially inner surface 27b of the first magnet 27 is planar and the radially outer surface 25a of the first outer core portion 25 is planar, and they are in contact with each other, but the present invention is not limited thereto. Fig. 7 shows a modification of the motor 10 described in the above embodiment. In this modification, as shown in fig. 7, the radially outer surface 25a of the first outer core portion 25 is formed into a convex curved surface shape bulging radially outward, and the radially inner surface 27b of the first magnet 27 is formed into a concave curved surface shape recessed radially outward, and they are in contact with each other. In this case, the radially outer surface 27a and the radially inner surface 27b of the first magnet 27 are both curved surfaces that protrude radially outward. That is, the first magnet 27 has an arcuate shape that protrudes outward in the radial direction when viewed from the axial direction.

In the above embodiment, the motor 10 is mounted on the electric power steering apparatus 100, but the present invention is not limited to this. The motor 10 may be used for a pump, a brake, a clutch, a vacuum cleaner, a dryer, a ceiling fan, a washing machine, a refrigerator, and the like.

Further, the respective configurations described in the above-described embodiment, modification example, and the like may be combined, and addition, omission, replacement, and other changes of the configuration may be made without departing from the scope of the present invention. The present invention is not limited to the above embodiments, but is defined only by the claims.

Claims

1. A motor, comprising:

a cylindrical stator; and

a pair of rotors which are positioned radially inward of the stator and rotate about a central axis, and which are stacked in an axial direction,

the rotor has:

an inner iron core portion;

a first outer core portion located radially outward of the inner core portion;

a second outer core portion located radially outward of the inner core portion and arranged at a position different from the first outer core portion in a circumferential direction;

a first magnet disposed radially outward of the first outer core portion; and

a second magnet disposed radially between the inner core portion and the second outer core portion,

the second magnet has a portion located radially outward in a cross-sectional view perpendicular to the center axis as being circumferentially distant from a center line passing through a circumferential center of the second outer core portion and the center axis,

first magnetic pole portions formed by the first outer core portions and the first magnets arranged in the radial direction and second magnetic pole portions formed by the second magnets and the second outer core portions arranged in the radial direction are alternately arranged in the circumferential direction,

the first magnetic pole portion of one of the pair of rotors and the second magnetic pole portion of the other of the pair of rotors are arranged in an axial direction, and have the same circumferential position.

2. The motor of claim 1,

in a cross-sectional view perpendicular to the central axis, the second magnet is arranged in a V-shape or a U-shape.

3. The motor according to claim 1 or 2,

the circumferential end portions of the second magnet are located radially outward of the circumferential central portion of the second magnet.

4. The motor according to any one of claims 1 to 3,

the circumferential both ends of the second magnet are located radially inward of the circumferential both ends of the first magnet.

5. The motor according to any one of claims 1 to 4,

the circumferential end portions of the radially inner surface of the second outer core portion are located radially outward of the circumferential center portion.

6. The motor according to any one of claims 1 to 5,

the second magnet has:

a first magnet located on one side in the circumferential direction with respect to the center line; and

a second-side magnet located on the other side in the circumferential direction from the center line,

the one-side magnet and the other-side magnet are arranged so as to be separated from each other in the circumferential direction.

7. The motor of claim 6,

the magnet at one side is in a plate shape,

the magnet on the other side is in a plate shape,

the one-side magnet and the other-side magnet have the same shape as each other.

8. The motor according to claim 6 or 7,

the N pole of the magnet at one side faces to one radial side, the S pole faces to the other radial side,

the N pole of the magnet on the other side faces to one radial side, and the S pole faces to the other radial side.