ROTOR, MOTOR AND ELECTRIC POWER STEERING DEVICE

Abstract

Rotor (20), comprising: a shaft (21) having a central axis (J); a rotor core (22) fixed to the shaft (21); and a magnet unit (23a, 23b) and a magnetic unit (24a, 24b) arranged side by side in a radial direction on a radial outer surface of the rotor core (22), wherein a plurality of sets (P1, P2) of the magnet unit (23a, 23b) and the magnetic unit (24a, 24b) are arranged in a circumferential direction and an axial direction on the radial outer side surface of the rotor core (22), wherein the plurality of sets (P1, P2) comprise: a first set (P1) in which the magnet unit (23a) is arranged on the radially outer side surface of the rotor core (22), while the magnetic unit (24b) is arranged on a radially outer side surface of the magnet unit (23a); and a second set (P2) in which the magnetic unit (24a) is arranged on the radially outer side surface of the rotor core (22), while the magnetic unit (23b) is arranged on a radially outer side surface of the magnetic unit (24a), wherein the first set (P1) and the second set (P2) are arranged alternately in the circumferential direction in a first partial area (S1) along the axial direction on the radial outer side surface of the rotor core (22), wherein the first set (P1) and the second set (P2) are arranged alternately in the circumferential direction in a second partial region (S2) different from the first partial region (S1) along the axial direction on the radial outer side surface of the rotor core (22), wherein, when viewed in the axial direction, the first set (P1) of the first partial region (S1) and the second set (P2) of the second partial region (S2) are arranged to overlap each other, and the second set (P2) of the first partial region (S1) and the first set (P1) of the second partial region (S2) are arranged to overlap each other, wherein a shape of the magnetic unit (23a) of the first set (P1) and a shape of the magnetic unit (24a) of the second set (P2) are identical to each other, and a shape of the magnetic unit (24b) of the first set (P1) and a shape of the magnetic unit (23b) of the second set (P2) are identical to each other.

Description

[Technical field]

[0001] The present invention relates to a rotor, a motor and an electric power steering device. [Background technology]

[0002] Typically, a motor comprises a rotor and a stator. The rotor includes at least one magnet. To reduce vibration and noise generated by the motor, it is necessary to reduce both cogging torque and torque ripple.

[0003] Conventional motors reduce cogging torque by providing protrusions or offsets that create phase reversal. For example, Patent Literature 1 discloses the offset. Torque ripple is reduced by increasing the sine wave ratio of an induced voltage. [REFERENCE LIST][PATENT LITERATURE]

[0004] Patent literature 1: JP 5 414 887 B2 Further exemplary rotors are known from US 2015 / 0 061 443 A1 and DE 10 2012 020 895 A1. [CONTENT OF THE INVENTION][Technical tasks]

[0005] A countermeasure for cogging torque is generally designed to generate an offset to generate an opposite phase. However, a problem arises in that the application of the offset causes a torque reduction. Furthermore, the cogging torque and torque ripple have a reciprocal relationship with respect to an offset angle, and both the cogging torque and the torque ripple are hardly reduced.

[0006] Taking the above circumstances into consideration, it is an object of the present invention to provide a rotor, a motor and an electric power steering apparatus capable of reducing cogging torque while preventing torque reduction and reducing torque ripple. [Solution of the tasks]

[0007] According to the present invention, there are provided a rotor according to claim 1, a motor according to claim 13, and an electric power steering apparatus according to claim 14. Exemplary embodiments are defined in the subclaims.

[0008] A rotor according to an exemplary embodiment includes: a shaft having a central axis; a rotor core fixed to the shaft; and a magnet unit and a magnetic unit arranged side by side in a radial direction on a radially outer side surface of the rotor core. A plurality of sets of the magnet unit and the magnetic unit are lined up in a circumferential direction and an axial direction on the radially outer side surface of the rotor core, the plurality of sets including: a first set in which the magnet unit is arranged on the radially outer side surface of the rotor core, while the magnetic unit is arranged on a radially outer side surface of the magnet unit;and a second set in which the magnetic unit is arranged on the radially outer side surface of the rotor core, while the magnet unit is arranged on the radially outer side surface of the magnetic unit, wherein the first set and the second set are alternately arranged in the circumferential direction in a first partial region along the axial direction on the radially outer side surface of the rotor core, the first set and the second set are alternately arranged in the circumferential direction in a second partial region, different from the first partial region, along the axial direction on the radially outer side surface of the rotor core, and wherein, when viewed in the axial direction, the first set of the first partial region and the second set of the second partial region are arranged to overlap each other, and the second set of the first partial region and the first set of the second partial region are arranged to overlap each other.;

[0009] A motor according to an exemplary embodiment includes the above-mentioned rotor and a stator opposed to the rotor with a gap in a radial direction.

[0010] An electric power steering apparatus according to an exemplary embodiment includes the above-mentioned motor. [Advantageous effects of the invention]

[0011] In the rotor, the motor, and the electric power steering apparatus according to one aspect of the present invention, the cogging torque can be reduced while preventing the torque reduction, and the torque ripple can be reduced. [Brief description of drawings] Fig. 1 is a schematic sectional view illustrating a rotor and a motor according to an embodiment. Fig. 2 is a perspective view of the rotor of the embodiment. Fig. 3 is an enlarged sectional view showing a portion of a section taken along a line III-III in Fig. 1 represents. Fig. 4 is an enlarged sectional view showing a portion of a section taken along a line IV-IV in Fig. 1 represents. Fig. 5 is a graph showing a waveform of a cogging torque of the motor of the embodiment. Fig. 6 is a graph showing a waveform of a torque ripple of the motor of the embodiment. Fig. 7 is an enlarged sectional view showing a part of a rotor according to a modification of the embodiment. Fig. 8 is a schematic diagram illustrating an electric power steering apparatus of the embodiment. [Description of embodiments]

[0012] In the following description, a direction parallel to a central axis J, namely a vertical direction, is simply referred to as an "axial direction," a radial direction centered on the central axis J is simply referred to as a "radial direction," and a circumferential direction centered on the central axis J is simply referred to as a "circumferential direction." In the following embodiment, an upper side (+Z) corresponds to one side in the axial direction, and a lower side (-Z) corresponds to the other side in the axial direction. The vertical direction, the upper side, and the lower side are merely labels for describing a relative positional relationship between the respective units, and an actual arrangement relationship and the like may be different from the arrangement relationship indicated by these labels.

[0013] As in Fig. 1, a motor 10 of the embodiment comprises a rotor 20, a stator 30, a housing 11 and a plurality of bearings 15, 16. As shown in Fig. 1 to Fig. 4, the rotor 20 comprises a shaft 21 having the central axis J, a rotor core 22, a plurality of magnet units 23a, 23b, a plurality of magnetic units 24a, 24b and a cover 25.

[0014] The shaft 21 extends vertically along the central axis J. In the example of the embodiment, the shaft 21 has a columnar shape extending in the axial direction. The shaft 21 is supported by the plurality of bearings 15, 16 so as to be rotatable around the central axis J. The plurality of bearings 15, 16 are arranged at intervals in the axial direction and are supported by the housing 11. The housing 11 has a tubular shape.

[0015] The shaft 21 is fixed to the rotor core 22 by means of press-fitting, bonding, or the like. This means that the rotor core 22 is fixed to the shaft 21. The shaft 21 may be fixed to the rotor core 22 with a resin member or the like interposed therebetween. This means that the shaft 21 is fixed to the rotor core 22 directly or indirectly. The shaft 21 is not limited to the above-mentioned cylindrical shape. For example, the shaft 21 may have a tubular shape.

[0016] For example, the rotor core 22 is a laminated steel plate formed by laminating a plurality of uniform plates of electromagnetic steel in the axial direction. The rotor core 22 has a tubular shape. The rotor core 22 has a polygonal outer shape when viewed in the axial direction (see Fig. 2). A radially outer side surface of the rotor core 22 has a plurality of flat surfaces 22a arranged in the circumferential direction. In the example of the embodiment, the rotor core 22 has an octagonal outer shape. The radially outer side surface of the rotor core 22 has eight flat surfaces 22a arranged in the circumferential direction. The flat surface 22a has a flat shape extending in a direction perpendicular to the radial direction. The flat surface 22a extends in the axial direction in the radially outer side surface of the rotor core 22. The flat surfaces 22a are arranged on the radially outer side surface of the rotor core 22 over the entire length in the axial direction. In the example of the embodiment, an axial length of the flat surface 22a is greater than a circumferential length.

[0017] The rotor core 22 has a through hole 22h, a hole 22b, and a groove 22c. When viewed in the axial direction, the through hole 22h is located in a central region of the rotor core 22. The through hole 22h penetrates the rotor core 22 in the axial direction. The shaft 21 is inserted into the through hole 22h.

[0018] The hole 22b penetrates the rotor core 22 in the axial direction. The plurality of holes 22b are formed in the rotor core 22 at intervals in the circumferential direction. In the example of the embodiment, the holes 22b are arranged in the rotor core 22 at equal intervals in the circumferential direction. When viewed in the axial direction, the hole 22b has a circular shape. In the embodiment, the rotor core 22 is lightened by means of the hole 22b, so that weight reduction and cost reduction of a material of the rotor core 22 can be achieved.

[0019] The groove 22c is recessed radially inward from the radial outer side surface of the rotor core 22 and extends in the axial direction. The groove 22c is arranged over the entire length in the axial direction on the radial outer side surface of the rotor core 22. The groove 22c is arranged between a pair of circumferentially adjacent flat surfaces 22a on the radial outer side surface of the rotor core 22 and is open radially outward. A plurality of grooves 22c are arranged on the rotor core 22 at intervals in the circumferential direction. The grooves 22c are arranged on the rotor core 22 at equal intervals in the circumferential direction. A groove width of the groove 22c becomes smaller radially outward. When viewed in the axial direction, the groove 22c has a wedge shape.

[0020] The magnet units 23a, 23b are permanent magnets. The magnetic units 24a, 24b are formed of a uniform magnetic material (a ferromagnetically uniform material), such as iron, stainless steel, and steel. As shown in Fig. 3 and Fig. 4, the magnet units 23a, 23b and the magnetic units 24a, 24b are provided radially adjacent to each other on the radially outer side surface of the rotor core 22. The magnet units 23a, 23b and the magnetic units 24a, 24b are provided on the flat surface 22a in such a way that they overlap each other in the radial direction. When viewed in a sectional view perpendicular to the central axis J, the magnet units 23a, 23b and the magnetic units 24a, 24b are provided one after another (two in total) in the flat surface 22a in such a way that they are layered in the radial direction.

[0021] A plurality of sets P1, P2 of the magnet units 23a, 23b and the magnetic units 24a, 24b arranged in the radial direction are arrayed in the circumferential direction and the axial direction on the radially outer side surfaces of the rotor core 22. In the example of the embodiment, the sets P1, P2 arrayed in the axial direction are arranged without a gap in the axial direction. The sets P1, P2 arrayed in the circumferential direction are arranged at intervals in the circumferential direction. The groove 22c is arranged between the pair of circumferentially adjacent sets P1, P2.

[0022] The plurality of sets P1, P2 include a first set P1 and a second set P2. In the first set P1, the magnet unit 23a is arranged on the radially outer side surface of the rotor core 22, and the magnetic unit 24b is arranged on the radially outer side surface of the magnet unit 23a. That is, the first set P1 includes the magnet unit 23a and the magnetic unit 24b such that the magnet unit 23a and the magnetic unit 24b are arranged in this order from the flat surface 22a toward the radially outer side. The magnet unit 23a of the first set P1 is overlapped with the magnetic unit 24b from the radially outer side. The magnet unit 23a is arranged on a radially inner side in the first set P1. For example, the magnet unit 23a may be referred to as an inner permanent magnet (IPM).

[0023] In the second set P2, the magnetic unit 24a is arranged on the radially outer side surface of the rotor core 22, and the magnet unit 23b is arranged on the radially outer side surface of the magnetic unit 24a. That is, the second set P2 includes the magnetic unit 24a and the magnet unit 23b such that the magnetic unit 24a and the magnet unit 23b are arranged in this order from the flat surface 22a toward the radially outer side. The magnet unit 23b is arranged on the radially outer side in the second set P2. For example, the magnet unit 23b can be referred to as a surface permanent magnet (SPM).

[0024] In the example of the embodiment, the shape of the magnetic unit 23a of the first set P1 and the shape of the magnetic unit 24a of the second set P2 are identical to each other. The shape of the magnetic unit 24b of the first set P1 and the shape of the magnetic unit 23b of the second set P2 are identical to each other.

[0025] Both the magnet unit 23a and the magnetic unit 24a have a plate shape. The magnet unit 23a and the magnetic unit 24a have a rectangular plate shape. As shown in Fig. 3 and Fig. As shown in Figure 4, when viewed in the axial direction, both the magnet unit 23a of the first set P1 and the magnet unit 24a of the second set P2 have a circumferential length longer than a radial length. Both the radially inner side surface and the radially outer side surface of the magnet unit 23a have the flat shape extending in the direction perpendicular to the radial direction. Both the radially inner side surface and the radially outer side surface of the magnet unit 24a have the flat shape extending in the direction perpendicular to the radial direction.

[0026] Both the magnet unit 23b and the magnetic unit 24b have a plate shape. When viewed from the radial direction, the magnet unit 23b and the magnetic unit 24b have a rectangular shape. Radial thicknesses of the magnet unit 23b and the magnetic unit 24b increase from both ends in the circumferential direction toward the center side (circumferential inner side). When viewed in the axial direction, both the magnetic unit 24b of the first set P1 and the magnet unit 23b of the second set P2 have the linear radial inner side surface and the convex radial outer side surface. The radial inner side surface of the magnetic unit 24b is the flat shape extending in the direction perpendicular to the radial direction. The radial outer side surface of the magnetic unit 24b has a curved surface that is convex toward the radial outer side when viewed in the axial direction.The radially inner side surface of the magnet unit 23b has a flat shape extending in the direction perpendicular to the radial direction. The radially outer side surface of the magnet unit 23b has a curved shape that is convex toward the radially outer side when viewed in the axial direction. When viewed in the axial direction, the magnetic unit 24b and the magnet unit 23b have a substantially D-shape.

[0027] In the example of the embodiment, in the first set P1, both ends in the circumferential direction of the magnet unit 23a and both ends in the circumferential direction of the magnetic unit 24b are arranged to overlap each other when viewed from the radial direction. This means that the circumferential positions at both ends in the circumferential direction of the magnet unit 23a are the same as the circumferential positions at both ends in the circumferential direction of the magnetic unit 24b. Both ends in the circumferential direction of both the magnet unit 23a and the magnetic unit 24b (i.e., the first set P1) and both ends in the circumferential direction of the flat surface 22a are arranged to overlap each other when viewed from the radial direction.In the illustrated example, the circumferential positions at the two ends in the circumferential direction of the flat surface 22a are slightly offset on the outer circumferential side from the circumferential positions at the two ends in the circumferential direction of the first set P1. This means that the circumferential length of the flat surface 22a is longer than the circumferential length of the first set P1.

[0028] In the second set P2, the two ends in the circumferential direction of the magnetic unit 24a and the two ends in the circumferential direction of the magnet unit 23b are arranged to overlap each other when viewed from the radial direction. This means that the circumferential positions at the two ends in the circumferential direction of the magnetic unit 24a are the same as the circumferential positions at the two ends in the circumferential direction of the magnet unit 23b. The two ends in the circumferential direction of both the magnetic unit 24a and the magnet unit 23b (i.e., the second set P2) and the two ends in the circumferential direction of the flat surface 22a are arranged to overlap each other when viewed from the radial direction.In the illustrated example, the circumferential positions at the two ends in the circumferential direction of the flat surface 22a are slightly offset on the outer circumferential side from the circumferential positions at the two ends in the circumferential direction of the second set P2. This means that the circumferential length of the flat surface 22a is longer than the circumferential length of the second set P2.

[0029] A volume of the magnetic unit 23a of the first set P1 is equal to a volume of the magnetic unit 24a of the second set P2. The volume of the magnetic unit 24b of the first set P1 is equal to the volume of the magnetic unit 23b of the second set P2. In the embodiment, the shape, properties, and the like of the first set P1 (the magnetic unit 23a and the magnetic unit 24b) and the shape, properties, and the like of the second set P2 (the magnetic unit 24a and the magnetic unit 23b) can be made similar. Accordingly, the effect (to be described later) of the embodiment can be achieved more stably.

[0030] In a first subregion (a first stage, a first region) S1 along the axial direction on the radially outer side surface of the rotor core 22, the first set P1 and the second set P2 are arranged alternately in the circumferential direction. In the first subregion S1, a plurality of sets P1, P2 are arranged at equal intervals in the circumferential direction on the radially outer side surface of the rotor core 22. In a second subregion (a second stage, a second region) S2, which is different from the first subregion S1, along the axial direction on the radially outer side surface of the rotor core 22, the first set P1 and the second set P2 are arranged alternately in the circumferential direction. In the second subregion S2, a plurality of sets P1, P2 are arranged at equal intervals in the circumferential direction on the radially outer side surface of the rotor core 22.

[0031] When viewed in the axial direction, the first set P1 of the first divided region S1 and the second set P2 of the second divided region S2 are arranged to overlap each other. When viewed in the axial direction, the second set P2 of the first divided region S1 and the first set P1 of the second divided region S2 are arranged to overlap each other. In the embodiment, when viewed in the axial direction, the center region in the circumferential direction of the first set P1 of the first divided region S1 and the center region in the circumferential direction of the second set P2 of the second divided region S2 are arranged to overlap each other, and the center region in the circumferential direction of the second set P2 of the first divided region S1 and the center region in the circumferential direction of the first set P1 of the second divided region S2 are arranged to overlap each other.When viewed in the axial direction, the two ends in the circumferential direction of the first set P1 of the first divided region S1 and the two ends in the circumferential direction of the second set P2 of the second divided region S2 are arranged to overlap each other, and the two ends in the circumferential direction of the second set P2 of the first divided region S1 and the two ends in the circumferential direction of the first set P1 of the second divided region S2 are arranged to overlap each other. For this reason, the offset is not applied to the magnet units 23a, 23b, and the magnet units 23a and 23b are lined up straight in the axial direction.

[0032] Fig. 5 is a graph showing a cogging torque waveform of the motor 10 having the rotor 20 of the embodiment. Fig. 6 is a graph showing a torque ripple waveform of the motor 10 of the embodiment. As shown in Fig. 5 and Fig. 6, in the embodiment, the opposite phase can be generated in the cogging torque without applying an offset to the magnet units 23a, 23b. That is, since the cogging torque generated in the first divided region S1 and the cogging torque generated in the second divided region S2 are generated with opposite phases to each other, the cogging torque generated in the first divided region S1 and the cogging torque generated in the second divided region S2 cancel each other, and a fluctuation range of a combined cogging torque waveform (a difference between a maximum value and a minimum value of the combined cogging torque) can be kept small. The opposite phase can be generated in the torque ripple.That is, since the torque ripple generated in the first divided region S1 and the torque ripple generated in the second divided region S2 are generated with phases opposite to each other, the torque ripple generated in the first divided region S1 and the torque ripple generated in the second divided region S2 cancel each other, and a fluctuation range of a combined torque ripple waveform (the difference between the maximum value and the minimum value of the combined torque ripple) can be kept small. Thus, in the embodiment, the cogging torque can be reduced while preventing torque degradation, and the torque ripple can be reduced. The vibration and noise generated by the motor 10 can be reduced.

[0033] When the magnet units 23a, 23b and the magnetic units 24a, 24b are arranged in the radial direction, a usage amount of the magnet (permanent magnet) can be reduced while preventing torque reduction. Specifically, for example, the usage amount of the magnet unit of an arrangement (hereinafter referred to as a comparative example) in which a plurality of magnet units (not shown) each having the same volume as a sum of the volume of the magnet unit 23a (23b) per one set P1 (P2) and the volume of the magnetic unit 24b (24a) per one set P1 (P2) are arrayed on the radially outer side surface of the rotor core 22, and the usage amount of the magnet in the embodiment will be compared with each other.In this case, compared to the comparative example, in the embodiment, the amount of magnet used can be reduced by about half, while suppressing the torque reduction, for example, to about 20%. In other words, the amount of magnet used can be reduced without reducing the torque. In general, a ratio of the cost of the magnet to the cost of the entire rotor 20 is high, and therefore, the cost of the entire rotor 20 can be easily reduced in the embodiment.

[0034] In the embodiment, the same number of first divided regions S1 and second divided regions S2 are alternately arranged in the axial direction on the radially outer side surface of the rotor core 22. This means that the sum of the number of first divided regions S1 and the number of second divided regions S2 becomes an even number, and the first divided regions S1 and the second divided regions S2 are alternately arranged in the axial direction. As a result, the above-described effect that can reduce the cogging torque and torque ripple can be achieved more stably. In the example of the embodiment, the first divided region S1 and the second divided region S2 are arranged in the axial direction on the radially outer side surface of the rotor core 22. Thus, the above-described effect can be achieved with a simple structure.

[0035] The cover 25 has a tubular shape centered on the central axis J. In the example of the embodiment, the cover 25 has a cylindrical shape. The cover 25 surrounds the rotor core 22, the magnet units 23a, 23b, and the magnetic units 24a, 24b from the radially outer side. An inner peripheral surface of the cover 25 and the radially outer side end of the first set P1 contact each other or face each other with a gap therebetween. Specifically, the inner peripheral surface of the cover 25 and the circumferential center region of the radially outer side surface of the first set P1 contact each other or face each other with a gap therebetween. The inner peripheral surface of the cover 25 and the radially outer side end of the second set P2 contact each other or face each other with a gap therebetween.Specifically, the inner peripheral surface of the cover 25 and the circumferential center portion of the radially outer side surface of the second set P2 contact each other or face each other with a gap therebetween. The rotor core 22, the magnet units 23a, 23b, and the magnetic units 24a, 24b are arranged with an air gap (empty space) G in the radial direction between the rotor core 22 and the inner peripheral surface of the cover 25. In the embodiment, even if the magnet units 23a, 23b and the magnetic units 24a, 24b are laminated in the radial direction on the radially outer side surface of the rotor core 22, the cover 25 can prevent movement toward the radially outer side of the magnet units 23a, 23b and the magnetic units 24a, 24b. An air gap G between the rotor core 22, the magnet units 23a, 23b and the magnetic units 24a, 24b and the cover 25 may be filled with resin.

[0036] Fig. 7 illustrates a modification of the rotor 20 of the embodiment. The rotor 20 includes a resin mold 26 instead of or together with the cover 25. The resin mold 26 is provided on the radially outer surface of the rotor core 22. A plurality of resin molds 26 are arranged at intervals in the circumferential direction on the radially outer surface of the rotor core 22. The resin mold 26 extends along the groove 22c. The resin mold 26 is formed by insert molding and curing a molten resin together with the rotor core 22.

[0037] The resin mold 26 includes an armature 26a and a movement preventing unit 26b. The groove 22c is filled with the molten resin and cured, thereby forming the armature 26a. The armature 26a extends in the axial direction. A circumferential width of the armature 26a increases toward the radially inner side. The movement preventing unit 26b is arranged on the radially outer side of the armature 26a and connected to the armature 26a. The movement preventing unit 26b is arranged at the radially outer side end of the resin mold 26. The movement preventing unit 26b protrudes from the armature 26a toward both circumferential sides (one side and the other side). The movement preventing unit 26b has a plate shape in which a plate surface faces the radial direction. The movement preventing unit 26b extends in the axial direction.The movement preventing unit 26b is arranged at a distance from the flat surface 22a on the radially outer side of the flat surface 22a. When viewed from the radial direction, the movement preventing unit 26b and the flat surface 22a are arranged to overlap each other.

[0038] After forming the resin mold 26, the sets P1, P2 are inserted between the flat surface 22a and the movement preventing unit 26b. For example, the sets P1, P2 are press-fitted between the flat surface 22a and the movement preventing unit 26b. In the embodiment, the resin mold 26 can act by providing the wedge-shaped groove 22c on the radially outer side surface of the rotor core 22. This means that the resin mold 26 can be provided that is prevented from radially detaching from the groove 22c. The magnet units 23a, 23b and the magnetic units 24a, 24b can be pressed from the radial outside by means of the resin mold 26, and the movement toward the radial outside of the magnet units 23a, 23b and the magnetic units 24a, 24b can be prevented.

[0039] As in Fig. As shown in Fig. 1, the stator 30 includes a stator core 31, an insulator 30Z, and a plurality of coils 30C. The stator core 31 has an annular shape centered on the central axis J. The stator core 31 surrounds the rotor 20 on the radially outer side of the rotor 20. The stator core 31 faces the rotor 20 with a gap therebetween. That is, the stator 30 faces the rotor 20 with the gap therebetween. For example, the stator core 31 is formed of a laminated steel plate in which a plurality of electromagnetic steel plates are laminated in the axial direction.

[0040] Specifically, the stator core 31 includes a substantially annular core back 31a and a plurality of teeth 31b. In the embodiment, the core back 31a has an annular shape centered on the central axis J. The tooth 31b extends from the radially inner side surface of the core back 31a toward the radially inner side. The outer peripheral surface of the core back 31a is fixed to the inner peripheral surface of a peripheral wall of the housing 11. The plurality of teeth 31b are arranged at intervals in the circumferential direction on the radially inner side surface of the core back 31a. In the embodiment, the teeth 31b are arranged at regular intervals in the circumferential direction.

[0041] The insulating body 30Z is attached to the stator core 31. The insulating body 30Z has a portion that covers the teeth 31b. For example, an insulating material such as a resin is used as a material for the insulating body 30Z.

[0042] The coil 30C is attached to the stator core 31. The plurality of coils 30C are attached to the stator core 31 with the insulating body 30Z interposed therebetween. A conductive wire is wound around each tooth 31b with the insulating body 30Z interposed therebetween, thereby forming the plurality of coils 30C.

[0043] An example of a device to which the motor 10 of the embodiment is mounted will be described below. An example in which the motor 10 is mounted on an electric power steering device will be described in the embodiment.

[0044] As in Fig.As shown in Figure 8, an electric power steering device 100 is mounted on a steering mechanism of a wheel of a car. The electric power steering device 100 is a device that reduces steering force using hydraulic pressure. The electric power steering device 100 of the embodiment includes the motor 10, a steering shaft 114, an oil pump 116, and a control valve 117.

[0045] The steering axle 114 transmits input from the steering 111 to an axle 113 having wheels 112. The oil pump 116 generates hydraulic pressure in a pressure cylinder 115, which transmits a driving force of the hydraulic pressure to the axle 113. The control valve 117 controls the 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.

[0046] The electric power steering apparatus 100 of the embodiment includes the motor 10 of the embodiment. Therefore, the electric power steering apparatus 100 achieving the same effect as the motor 10 can be achieved.

[0047] The present invention is not limited to the above embodiment. For example, as described below, the configuration or the like may be changed without departing from the scope of the present invention.

[0048] The shapes of the magnet units 23a, 23b and the shapes of the magnetic units 24a, 24b are not limited to the examples described in the above embodiment. The volume of the magnet unit 23a of the first set P1 and the volume of the magnet unit 23b of the second set P2 may be different from each other. The volume of the magnetic unit 24b of the first set P1 and the volume of the magnetic unit 24a of the second set P2 may be different from each other.

[0049] Instead of or during providing the cover 25 and the resin mold 26 to the rotor 20, the flat surface 22a, the magnet units 23a, 23b and the magnetic units 24a, 24b contacting each other in the radial direction may be fixed to each other by bonding or the like.

[0050] In the above embodiment, the rotor core 22 and the magnetic units 24a, 24b are provided in the rotor 20 as separate components. However, the present invention is not limited to this configuration. The rotor core 22 and the magnetic units 24a, 24b may be a single component. Furthermore, the magnetic unit 23a may be embedded in the magnetic unit 24b provided integrally with the rotor core 22. In this case, the cover 25 may surround the second set P2 from the radially outer side. Accordingly, the magnetic unit 23b can be prevented from detaching in the second set P2.

[0051] Although the example in which the motor 10 is mounted on the electric power steering device 100 is described in the above embodiment, the present invention is not limited to this configuration. The motor 10 can be used for various devices, such as a pump, a brake, a clutch, a vacuum cleaner, a dryer, a sluice air blower, a washing machine, and a refrigerator.

[0052] Without departing from the scope of the present invention, the configurations (components), modifications, and explanatory notes described in the above embodiment may be combined, and additions, omissions, substitutions, and other changes to the configurations may be made. The present invention is not limited by the above embodiment, but is limited only by the scope of the claims. [List of reference symbols] 10 Engine 20 rotors 21 Wave 22 Rotor core 22b hole 22c groove 23a, 23b Magnet unit 24a, 24b magnetic unit 25 Cover 30 Stator 100 electric power steering device J Central axis P1, P2 sentence P1 first sentence P2 second set S1 first section S2 second section

Claims

[1] Rotor (20), comprising: a shaft (21) having a central axis (J); a rotor core (22) fixed to the shaft (21); and a magnet unit (23a, 23b) and a magnetic unit (24a, 24b) arranged side by side in a radial direction on a radial outer surface of the rotor core (22), wherein a plurality of sets (P1, P2) of the magnet unit (23a, 23b) and the magnetic unit (24a, 24b) are arranged in a circumferential direction and an axial direction on the radial outer side surface of the rotor core (22), wherein the plurality of sets (P1, P2) comprise: a first set (P1) in which the magnet unit (23a) is arranged on the radially outer side surface of the rotor core (22), while the magnetic unit (24b) is arranged on a radially outer side surface of the magnet unit (23a); and a second set (P2) in which the magnetic unit (24a) is arranged on the radially outer side surface of the rotor core (22), while the magnetic unit (23b) is arranged on a radially outer side surface of the magnetic unit (24a), wherein the first set (P1) and the second set (P2) are arranged alternately in the circumferential direction in a first partial area (S1) along the axial direction on the radial outer side surface of the rotor core (22), wherein the first set (P1) and the second set (P2) are arranged alternately in the circumferential direction in a second partial region (S2) different from the first partial region (S1) along the axial direction on the radial outer side surface of the rotor core (22), wherein, when viewed in the axial direction, the first set (P1) of the first partial region (S1) and the second set (P2) of the second partial region (S2) are arranged to overlap each other, and the second set (P2) of the first partial region (S1) and the first set (P1) of the second partial region (S2) are arranged to overlap each other, wherein a shape of the magnetic unit (23a) of the first set (P1) and a shape of the magnetic unit (24a) of the second set (P2) are identical to each other, and a shape of the magnetic unit (24b) of the first set (P1) and a shape of the magnetic unit (23b) of the second set (P2) are identical to each other. [2] Rotor (20) according to claim 1, wherein when viewed in the axial direction a central region in the circumferential direction of the first set (P1) of the first partial region (S1) and a central region in the circumferential direction of the second set (P2) of the second partial region (S2) are arranged such that they overlap each other, and a central region in the circumferential direction of the second set (P2) of the first partial region (S1) and a central region in the circumferential direction of the first set (P1) of the second partial region (S2) are arranged such that they overlap each other. [3] Rotor (20) according to claim 1 or 2, wherein when viewed in the axial direction both ends in the circumferential direction of the first set (P1) of the first partial region (S1) and both ends in the circumferential direction of the second set (P2) of the second partial region (S2) are arranged such that they overlap each other, and both ends in the circumferential direction of the second set (P2) of the first partial region (S1) and both ends in the circumferential direction of the first set (P1) of the second partial region (S2) are arranged such that they overlap each other. [4] Rotor (20) according to one of claims 1 to 3, wherein identical numbers of the first partial regions (S1) and the second partial regions (S2) are arranged alternately in the axial direction on the radial outer side surface of the rotor core (22). [5] Rotor (20) according to claim 4, wherein the first partial region (S1) and the second partial region (S2) are arranged axially successively on the radial outer side surface of the rotor core (22). [6] Rotor (20) according to one of claims 1 to 5, wherein when viewed in the axial direction both the magnetic unit (23a) of the first set (P1) and the magnetic unit (24a) of the second set (P2) have a rectangular shape having a circumferential length that is longer than a radial length, and both the magnetic unit (24b) of the first set (P1) and the magnetic unit (23b) of the second set (P2) have a radially inner side surface having a linear shape and a radially outer side surface having a convexly curved shape. [7] Rotor (20) according to one of claims 1 to 6, wherein a volume of the magnet unit (23a) of the first set (P1) and a volume of the magnetic unit (24a) of the second set (P2) are equal to each other, and wherein a volume of the magnetic unit (24b) of the first set (P1) and a volume of the magnet unit (23b) of the second set (P2) are equal to each other. [8] The rotor (20) according to any one of claims 1 to 7, wherein the rotor core (22) has a hole (22b) penetrating the rotor core (22) in the axial direction. [9] The rotor (20) according to claim 8, wherein a plurality of said holes (22b) are arranged at intervals in the circumferential direction in the rotor core (22). [10] The rotor (20) according to any one of claims 1 to 9, wherein the rotor core (22) has a groove (22c) recessed from the radially outer side surface of the rotor core (22) toward a radially inner side and extending in the axial direction, and wherein the groove (22c) is arranged between a pair of circumferentially adjacent sets (P1, P2) and is open toward a radially outer side, and a groove width decreases toward the radially outer side. [11] Rotor (20) according to one of claims 1 to 10, further comprising a cover (25) surrounding the rotor core (22), the magnet unit (23a, 23b) and the magnetic unit (24a, 24b) from the radial outside. [12] Rotor (20) according to claim 11, wherein the cover (25) surrounds the second set (P2) from the radial outside. [13] Engine (10), comprising: the rotor (20) according to one of claims 1 to 12; and a stator (30) arranged opposite the rotor (20) in a radial direction with a gap. [14] An electric power steering apparatus (100) comprising the motor (10) according to claim 13.

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