WO2019189599A1

WO2019189599A1 - Rotor, motor, and electric power steering device

Info

Publication number: WO2019189599A1
Application number: PCT/JP2019/013646
Authority: WO
Inventors: 明一円; 秀幸金城
Original assignee: 日本電産株式会社
Priority date: 2018-03-30
Filing date: 2019-03-28
Publication date: 2019-10-03
Also published as: CN111903039A; JPWO2019189599A1

Abstract

An embodiment of the rotor of the present invention is provided with a shaft, a rotor core, and a plurality of magnets. The rotor core has a plurality of magnet fixation surfaces arranged along the circumferential direction. At least one magnet fixation surface from among the plurality of magnet fixation surfaces is provided with a first ridge part positioned on one circumferential side of a magnet fixed to the magnet fixation surface. At least one magnet fixation surface from among the plurality of magnet fixation surfaces is provided with a second ridge part positioned on the other circumferential side of a magnet fixed to the magnet fixation surface. The first ridge part extends along the axial direction from an end part, on one side with respect to the axial direction, to approximately the middle, with respect to the axial direction, of the magnet fixation surface. The second ridge part extends along the axial direction from an end part, on the other side with respect to the axial direction, to approximately the middle, with respect to the axial direction, of the magnet fixation surface. The first ridge part and the second ridge part are formed from a magnetic body.

Description

Rotor, motor and electric power steering device

The present invention relates to a rotor, a motor, and an electric power steering device.

The motor rotor includes a rotor core that rotates together with the shaft, and a plurality of magnets provided in the circumferential direction of the rotor core. Such cogging torque generated in the motor leads to an increase in vibration and noise of the motor. For this reason, it is desired to suppress the occurrence of cogging torque in the motor. For example, International Publication No. 2011/114574 describes reducing the cogging torque by inclining (skewing) the magnet of the rotor core with respect to the axial direction.

International Publication No. 2011/114574

However, the motor as described above has a problem that it takes time to assemble the rotor and productivity is lowered.

In view of the above circumstances, an object of the present invention is to provide a rotor, a motor, and an electric power steering device that can suppress cogging torque and simplify assembly.

One aspect of the rotor of the present invention includes a shaft extending along a central axis, a rotor core made of a magnetic material and fixed to the shaft, and a plurality of magnets fixed to the rotor core. The rotor core has a plurality of magnet fixing surfaces arranged in the radial direction facing the radially outer side. The magnets are respectively fixed to the plurality of magnet fixing surfaces. At least one of the plurality of magnet fixing surfaces is positioned on one side in the circumferential direction of the magnet fixed to the magnet fixing surface, and protrudes radially outward from the magnet fixing surface. Ridges are provided. The at least one magnet fixing surface of the plurality of magnet fixing surfaces is located on the other circumferential side of the magnet fixed to the magnet fixing surface, and protrudes radially outward from the magnet fixing surface. Ridges are provided. The first ridge portion extends along the axial direction from the end portion on one axial side of the magnet fixing surface to the middle in the axial direction. The second ridge extends along the axial direction from the other axial end of the magnet fixing surface to the middle of the axial direction. The first and second ridges are made of a magnetic material.

Also, one aspect of the motor of the present invention includes the above-described rotor and a stator that faces the rotor with a gap in the radial direction.

Moreover, one aspect of the electric power steering apparatus of the present invention includes the above-described motor.

According to the rotor, motor, and electric power steering device of one aspect of the present invention, cogging torque can be suppressed and assembly can be simplified.

FIG. 1 is a cross-sectional view of a motor according to an embodiment. FIG. 2 is a partial perspective view of a rotor according to an embodiment. FIG. 3 is a cross-sectional view of the rotor taken along line III-III in FIG. 4 is a cross-sectional view of the rotor taken along line IV-IV in FIG. FIG. 5 is a graph showing a waveform of cogging torque of the motor according to the embodiment. FIG. 6 is a cross-sectional view of the rotor of the first modification. FIG. 7 is a cross-sectional view of the rotor of the first modification. FIG. 8 is a partial perspective view of the rotor of the second modification. FIG. 9 is a graph showing a cogging torque waveform of a motor including the rotor of the second modification. FIG. 10 is a schematic diagram illustrating an electric power steering apparatus according to an embodiment.

Hereinafter, a rotor, a motor, and an electric power steering device according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, in order to make each configuration easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

The Z-axis direction as shown in each figure is a vertical direction in which the positive side is the upper side and the negative side is the lower side. A central axis J shown as appropriate in each drawing is an imaginary line parallel to the Z-axis direction and extending in the vertical direction. In the following description, the axial direction of the central axis J, that is, the direction parallel to the vertical direction is simply referred to as “axial direction”, and the radial direction around the central axis J is simply referred to as “radial direction”. The circumferential direction centered on is simply referred to as the “circumferential direction”. In each drawing, the circumferential direction is appropriately indicated by an arrow θ.

Also, the positive side in the Z-axis direction in the axial direction is referred to as “upper side”, and the negative side in the Z-axis direction in the axial direction is referred to as “lower side”. In the present embodiment, the upper side corresponds to one side in the axial direction, and the lower side corresponds to the other side in the axial direction. Further, the side proceeding counterclockwise when viewed from the upper side to the lower side in the circumferential direction, that is, the side proceeding in the direction of the arrow θ is referred to as “one circumferential side”. The side proceeding clockwise when viewed from the upper side to the lower side in the circumferential direction, that is, the side proceeding in the direction opposite to the direction of the arrow θ is referred to as “the other side in the circumferential direction”.

The vertical direction, the upper side, and the lower side are simply names for explaining the arrangement relationship of each part, and the actual arrangement relationship is an arrangement relationship other than the arrangement relationship indicated by these names. May be.

FIG. 1 is a cross-sectional view of the motor 10 of the present embodiment. The motor 10 according to the present embodiment includes a rotor 20, a stator 30, a bearing holder 12, a housing 11, and a pair of

bearings

15 and 16. The rotor 20 rotates around the central axis J. The housing 11 has a cylindrical shape having a bottom. The housing 11 accommodates the rotor 20, the stator 30, the bearing holder 12, and a pair of

bearings

15 and 15 inside. The bearing holder 12 is located above the stator 30. The bearing holder 12 is supported on the inner peripheral surface of the housing 11. The pair of

bearings

15 and 16 are arranged at an interval in the axial direction. The pair of

bearings

15 and 16 support the shaft 21 of the rotor 20. Of the pair of

bearings

15, 16, one bearing 15 is supported by the bearing holder 12, and the other bearing 16 is supported by the housing 11.

The stator 30 has an annular shape centered on the central axis J. The stator 30 faces the rotor 20 with a gap in the radial direction. 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 is configured, for example, by laminating a plurality of electromagnetic steel plates in the axial direction. The stator core 31 has a substantially annular core back 31a and a plurality of teeth 31b. In the present embodiment, the core back 31a has an annular shape centered on the central axis J. The outer peripheral surface of the core back 31 a is fixed to the inner peripheral surface of the housing 11. The teeth 31b extend radially inward from the radially inner side surface of the core back 31a. The plurality of teeth 31b are arranged at equal intervals along the circumferential direction. The insulator 30Z is attached to the stator core 31. The insulator 30Z covers the teeth 31b. The material of the insulator 30Z is an insulating material such as a resin. The coil 30C is attached to the stator core 31. The coil 30C is configured by winding a conductive wire around the teeth 31b via the insulator 30Z. The rotor 20 includes a shaft 21 having a central axis J, a rotor core 22, and a plurality of magnets 23. The shaft 21 extends in the vertical direction along the central axis J. In the example of the present embodiment, the shaft 21 has a cylindrical shape extending in the axial direction. The shaft 21 is supported by a plurality of

bearings

15 and 16 so as to be rotatable around the central axis J. The shaft 21 is not limited to the cylindrical shape, and may be a cylindrical shape, for example.

FIG. 2 is a partial perspective view of the rotor 20. FIG. 3 is a cross-sectional view of the rotor 20 taken along line III-III in FIG. 4 is a cross-sectional view of the rotor 20 taken along line IV-IV in FIG.

As shown in FIGS. 3 and 4, the outer shape of the rotor core 22 is polygonal when viewed from the axial direction. In the example of this embodiment, the outer shape of the rotor core 22 is a substantially octagonal shape. The rotor core 22 is made of a magnetic material. More specifically, the rotor core 22 is made of a ferromagnetic material. As shown in FIG. 1, the rotor core 22 is composed of a plurality of

electromagnetic steel plates

22A and 22B stacked in the axial direction. As shown in FIGS. 3 and 4, the rotor core 22 is provided with a central hole 22h located in the center in plan view. The central hole 22h penetrates along the axial direction. The shaft 21 is press-fitted into the central hole 22h. Thereby, the rotor core 22 is fixed to the outer peripheral surface of the shaft 21. The rotor core 22 may be indirectly fixed to the shaft 21 via a resin member or the like.

The rotor core 22 is provided with a plurality of holes 22b penetrating along the axial direction and arranged at equal intervals along the circumferential direction. In the present embodiment, the hole 22b has a circular shape in plan view. In the present embodiment, the rotor core 22 is provided with eight holes 22b. Each hole 22b is arranged on the inner side in the radial direction of one magnet 23 described later. According to this embodiment, the rotor core 22 is thinned by the hole 22b, and the weight of the rotor core 22 and the material cost can be reduced. A plurality of magnet fixing surfaces 22a and a plurality of groove portions 22c are provided on the outer periphery of the rotor core 22 facing the radially outer side. In other words, the rotor core 22 has a plurality of magnet fixing surfaces 22a arranged in the circumferential direction facing the radially outer side.

The groove 22c is located between the magnet fixing surfaces 22a adjacent to each other along the circumferential direction. The groove portion 22 c is recessed from the radially outer surface of the rotor core 22 to the radially inner side. Moreover, the groove part 22c opens to the radial direction outer side. The groove 22c extends along the axial direction. The groove portion 22 c extends over the entire axial length of the radially outer surface of the rotor core 22. The groove portion 22c has a groove width that decreases toward the outside in the radial direction. That is, the groove 22c has a wedge shape when viewed from the axial direction. When the rotor 20 is resin-molded, the resin enters the groove 22c. In this case, it is possible to prevent the resin portion from being detached from the rotor 20 because the groove portion 22c has a wedge shape.

The magnet fixing surface 22a has a planar shape extending in a direction perpendicular to the radial direction. The magnet fixing surface 22a may be a curved surface. The magnet fixing surface 22 a extends in the axial direction on the radially outer surface of the rotor core 22. The magnet fixing surface 22 a is disposed on the radially outer side surface of the rotor core 22 over the entire axial direction. In the example of this embodiment, the length dimension in the axial direction of the magnet fixing surface 22a is larger than the length dimension in the circumferential direction. The rotor core 22 of the present embodiment has eight magnet fixing surfaces 22a.

A magnet 23 is fixed to each of the plurality of magnet fixing surfaces 22a. That is, the rotor core 22 holds the magnet 23 on the magnet fixing surface 22a. The magnet 23 and the magnet fixing surface 22a may be indirectly fixed via a resin member or the like. When the rotor 20 is resin-molded, the magnet 23 may be fixed to the magnet fixing surface 22a by covering the magnet 23 from the outside in the radial direction with resin.

The magnet 23 is a permanent magnet. The plurality of magnets 23 are fixed to different magnet fixing surfaces 22a. That is, the magnet 23 is fixed to the rotor core 22. The plurality of magnets 23 are arranged along the circumferential direction, with the magnetic poles facing outward in the radial direction being alternated along the circumferential direction. The magnet 23 extends with a uniform cross section along the axial direction. The magnet 23 has an outer surface 23a facing outward in the radial direction, an inner surface 23b facing inward in the radial direction, and a pair of peripheral side surfaces (end surfaces) 23c facing in the circumferential direction.

The outer surface 23a extends in an arc shape centered on the central axis J. The inner side surface 23b is a flat surface extending in a direction perpendicular to the radial direction. The inner side surface 23b faces the magnet fixing surface 22a. The peripheral side surface 23c is a plane orthogonal to the inner side surface 23b. The peripheral side surface 23c connects the inner side surface 23b and the outer side surface 23a. The circumferential side surfaces 23c of the magnets 23 adjacent to each other in the circumferential direction face each other in the circumferential direction. The magnet 23 covers the entire axial direction of the magnet fixing surface 22a. Moreover, the magnet 23 is arrange | positioned in the center of the magnet fixing surface 22a in the circumferential direction.

As shown in FIG. 2, the magnet fixing surface 22a is provided with a pair of exposed portions 22aa that the magnet 23 does not contact in the circumferential direction. The pair of exposed portions 22aa extends in the axial direction along a pair of circumferential edges of the magnet fixing surface 22a. The rotor core 22 has an upper ridge (first ridge) 24 and a lower ridge (second ridge) 25. The upper ridge 24 and the lower ridge 25 are made of a magnetic material. More specifically, the upper ridge portion 24 and the lower ridge portion 25 are made of a ferromagnetic material. In the present embodiment, the upper ridge portion 24 and the lower ridge portion 25 are part of the rotor core 22. Therefore, the upper ridge portion 24 and the lower ridge portion 25 are configured as part of the electromagnetic steel plates 22 </ b> A and 22 </ b> B constituting the rotor core 22. The upper and

lower ridges

24 and 25 and the rotor core 22 may be separate members.

The upper ridge portion 24 is provided on at least one magnet fixing surface 22a among the plurality of magnet fixing surfaces 22a. Similarly, the lower ridge portion 25 is provided on at least one magnet fixing surface 22a among the plurality of magnet fixing surfaces 22a. In the present embodiment, the upper ridge portion 24 and the lower ridge portion 25 are provided on different magnet fixing surfaces 22a. Moreover, the magnet fixing surface 22a provided with the upper ridges 24 and the magnet fixing surface 22a provided with the lower ridges 25 are adjacent to each other in the circumferential direction. The upper ridge portion 24 and the lower ridge portion 25 may be provided on the same magnet fixing surface 22a.

As shown in FIGS. 3 and 4, four upper ridges 24 and four lower ridges 25 are provided on the rotor core 22, respectively. As shown in FIG. 3, the magnet fixing surfaces 22a on which the upper ridges 24 are provided are arranged at equal intervals along the circumferential direction. As shown in FIG. 4, the magnet fixing surfaces 22a on which the lower ridges 25 are provided are arranged at equal intervals along the circumferential direction. The magnet fixing surface 22a provided with the upper ridges 24 and the magnet fixing surface 22a provided with the lower ridges 25 are alternately arranged in the circumferential direction.

As shown in FIG. 2, the upper ridge portion 24 and the lower ridge portion 25 are respectively positioned on the exposed portion 22aa of the magnet fixing surface 22a. Each of the upper ridges 24 and the lower ridges 25 protrudes radially outward from the magnet fixing surface 22a. The upper ridge portion 24 extends along the axial direction from the upper end portion (end portion on one side in the axial direction) of the magnet fixing surface 22a to the middle in the axial direction. On the other hand, the lower ridge portion 25 extends along the axial direction from the lower end portion (end portion on the other side in the axial direction) of the magnet fixing surface 22a to the middle in the axial direction.

The upper ridge portion 24 is located on one side in the circumferential direction of the magnet 23 fixed to the magnet fixing surface 22a on which the upper ridge portion 24 is provided. The upper ridge portion 24 contacts the circumferential side surface 23 c on one side in the circumferential direction of the magnet 23. On the other hand, the lower ridge portion 25 is located on the other circumferential side of the magnet 23 fixed to the magnet fixing surface 22a on which the lower ridge portion 25 is provided. The lower ridge portion 25 contacts the circumferential side surface 23 c on the other circumferential side of the magnet 23.

In the present embodiment, the length dimension along the axial direction of the upper ridge portion 24 and the length dimension along the axial direction of the lower ridge portion 25 coincide with each other. The axial position of the lower end portion (end on the other side in the axial direction) of the upper ridge portion 24 and the upper end portion (end portion on the one side in the axial direction) of the lower ridge portion 25 coincide with each other.

In the present embodiment, the upper half (half on one side in the axial direction) of the rotor 20 is the upper side area (first area) A1, and the lower half (half on the other side in the axial direction) of the rotor 20 is the lower side area. (Second area) A2. The rotor core 22 has an upper ridge portion 24 and no lower ridge portion 25 in the upper region A1. Further, the rotor core 22 does not have the upper ridge portion 24 but has the lower ridge portion 25 in the lower region A2.

FIG. 5 is a graph showing a cogging torque waveform of the motor 10 of the present embodiment. FIG. 5 shows the waveform of the cogging torque in the upper region A1 of the rotor 20, the waveform of the cogging torque in the lower region A2, and the waveform of the cogging torque obtained by combining these. When comparing the waveform of the cogging torque in the upper region A1 with the waveform of the cogging torque in the lower region A2, they are in opposite phases. That is, according to the present embodiment, an antiphase can be generated in the cogging torque without skewing the magnet 23. According to this embodiment, in the waveform of the combined cogging torque, the waveform of the cogging torque in the upper region A1 and the waveform of the cogging torque in the lower region A2 cancel each other, and the vibration width of the cogging torque (the maximum value of the combined cogging torque). And the minimum value) can be kept small.

An upper ridge portion 24 made of a magnetic material is provided on the magnet fixing surface 22a of the rotor core 22 in the upper region A1. The upper ridge 24 is located on one side of the magnet 23 in the circumferential direction. For this reason, in the upper region A1, it is considered that the magnetic flux of the magnet 23 is pulled by the upper protrusion 24 and biased to one side in the circumferential direction.

On the other hand, on the magnet fixing surface 22a of the rotor core 22 in the lower region A2, a lower ridge portion 25 made of a magnetic material is provided. The lower ridge portion 25 is located on the other circumferential side of the magnet 23. For this reason, in the lower region A2, it is considered that the magnetic flux of the magnet 23 is pulled by the lower protrusion 25 and biased to the other side in the circumferential direction. As a result, in the upper region A1 and the lower region A2, the center of the magnetic flux generated from the magnet 23 is biased to the opposite side in the circumferential direction, and the same effect as when the magnet 23 is skewed can be obtained. That is, according to the present embodiment, since the cogging torque can be reduced without skewing the magnet 23, the assembly process of the rotor 20 can be simplified.

As shown in FIG. 2, according to the present embodiment, the upper ridge portion 24 contacts the circumferential side surface 23 c on one side in the circumferential direction of the magnet 23. Similarly, the lower ridge portion 25 contacts the circumferential side surface 23 c on the other circumferential side of the magnet 23. Thereby, the effect which biases the magnetic flux of the magnet 23 by the upper side protruding item | line part 24 and the lower side protruding item | line part 25 to the circumferential direction one side or the other side can be heightened. According to this embodiment, the magnet fixing surface 22a on which the upper ridge portion 24 is provided and the magnet fixing surface 22a on which the lower ridge portion 25 is provided are adjacent to each other in the circumferential direction. For this reason, the center of the magnetic flux of the magnet 23 adjacent to the circumferential direction can be biased to the opposite side of the circumferential direction, and the effect of reducing the cogging torque can be enhanced.

According to the present embodiment, the length dimension along the axial direction of the upper ridge portion 24 and the length dimension along the axial direction of the lower ridge portion 25 coincide with each other. In other words, the length dimension along the axial direction of the upper region A1 of the rotor 20 and the length dimension along the axial direction of the lower region A2 are the same. For this reason, the absolute value of the cogging torque in the upper region A1 and the absolute value of the cogging torque in the lower region A2 can be substantially matched with each other. As a result, the cogging torque in the upper region A1 and the cogging torque in the lower region A2 cancel each other, and the combined cogging torque is effectively reduced.

According to the present embodiment, the number of the upper ridge portions 24 and the number of the lower ridge portions 25 coincide with each other. For this reason, the absolute value of the cogging torque in the upper region A1 and the absolute value of the cogging torque in the lower region A2 can be substantially matched with each other, and the combined cogging torque is effectively reduced.

As shown in FIG. 3, according to the present embodiment, the magnet fixing surfaces 22a on which the upper ridges 24 are provided are arranged at equal intervals along the circumferential direction. Similarly, as shown in FIG. 4, the magnet fixing surfaces 22a on which the lower ridges 25 are provided are arranged at equal intervals along the circumferential direction. According to this embodiment, the cogging torque can be effectively reduced by arranging the upper ridge portion 24 and the lower ridge portion 25 in a balanced manner along the circumferential direction.

As shown in FIG. 1, according to the present embodiment, the rotor core 22 is composed of a plurality of

electromagnetic steel plates

22A and 22B stacked along the axial direction. Further, the upper ridge portion 24 and the lower ridge portion 25 are part of the

electromagnetic steel plates

22A and 22B. In the upper region A1, the rotor core 22 is configured by laminating the first electromagnetic steel plates 22A. In the lower region A2, the rotor core 22 is configured by laminating the second electromagnetic steel plate 22B. The first electromagnetic steel plate 22 </ b> A includes an upper ridge portion 24. The second electromagnetic steel plate 22B includes a lower ridge portion 25. As shown in FIG. 2, according to this embodiment, the axial position of the lower end portion of the upper ridge portion 24 and the axial position of the upper end portion of the lower ridge portion 25 coincide with each other. Therefore, the rotor core 22 is configured using only two types of electromagnetic steel plates (the first electromagnetic steel plate 22A and the second electromagnetic steel plate 22B). Further, the first electromagnetic steel plate 22A and the second electromagnetic steel plate 22B are in the shape of the front and back surfaces. For this reason, 22 A of 1st electromagnetic steel plates can be reversed and used as the 2nd electromagnetic steel plate 22B. That is, the rotor core 22 of the present embodiment can be configured from one type of electromagnetic steel sheet that has been pressed. According to the present embodiment, it is possible to suppress an increase in the types of components constituting the rotor core 22 and to provide the inexpensive rotor 20 and motor 10.

(Modification 1)
Next, the rotor 120 of the modification 1 employable for the above-described motor 10 will be described with reference to FIGS. 6 and 7. FIG. 6 is a cross-sectional view of the rotor 120 of this modification, and corresponds to FIG. 3 of the above-described embodiment. FIG. 7 is a cross-sectional view of the rotor 120 of this modification, and corresponds to FIG. 4 of the above-described embodiment. In addition, about the component of the same aspect as the above-mentioned embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

The rotor 120 of this modification is mainly different from the above-described embodiment in that the upper ridge portions 24 and the lower ridge portions 25 are provided on all the magnet fixing surfaces 22a of the rotor core 122. According to this modification, the same effect as when all the magnets 23 are skewed can be obtained, and the effect of reducing the cogging torque can be further enhanced.

(Modification 2)
Next, a rotor 220 according to a second modification that can be employed in the motor 10 described above will be described with reference to FIGS. 8 and 9. FIG. 8 is a partial perspective view of the rotor 220 of this modification. In this modification, the rotor core 222 includes an upper ridge (first ridge) 224 and a lower ridge (second ridge) 225. The upper ridge portion 224 and the lower ridge portion 225 are made of a magnetic material.

Similarly to the above-described embodiment, the upper ridge portion 224 and the lower ridge portion 225 of the present modification are provided on different magnet fixing surfaces 22a. Further, the magnet fixing surface 22a provided with the upper ridge portion 224 and the magnet fixing surface 22a provided with the lower ridge portion 225 are adjacent to each other in the circumferential direction. The magnet fixing surfaces 22a on which the upper ridges 224 are provided are arranged at equal intervals along the circumferential direction. The magnet fixing surfaces 22a on which the lower ridges 225 are provided are arranged at equal intervals along the circumferential direction. The magnet fixing surface 22a provided with the upper ridges 224 and the magnet fixing surface 22a provided with the lower ridges 225 are alternately arranged in the circumferential direction.

The upper ridge portion 224 and the lower ridge portion 225 protrude radially outward from the magnet fixing surface 22a. The upper ridge portion 224 is located on one side in the circumferential direction of the magnet 23 fixed to the magnet fixing surface 22a on which the upper ridge portion 224 is provided. The lower ridge portion 225 is located on the other circumferential side of the magnet 23 fixed to the magnet fixing surface 22a on which the lower ridge portion 225 is provided.

The upper ridge 224 extends along the axial direction from the upper end of the magnet fixing surface 22a to the middle in the axial direction. On the other hand, the lower protrusion 225 extends along the axial direction from the lower end of the magnet fixing surface 22a to the middle in the axial direction. In this modification, the axial position of the lower end portion (end on the other side in the axial direction) of the upper ridge portion 224 is the axial position of the upper end portion (end portion on the one side in the axial direction) of the lower ridge portion 225. Is located on the upper side (one side in the axial direction). That is, the upper ridge portion 224 and the lower ridge portion 225 are disposed with a gap in the axial direction.

In this modification, the length dimension along the axial direction of the upper ridge portion 224 and the length dimension along the axial direction of the lower ridge portion 225 coincide with each other. Further, the distance along the axial direction between the lower end portion (the end portion on the other side in the axial direction) of the upper ridge portion 224 and the upper end portion (end portion on the one side in the axial direction) of the lower ridge portion 225 is the upper side. It corresponds with the length dimension along the axial direction of the protruding line part 224 and the lower protruding line part 225.

In this modification, the rotor 220 is partitioned into three in the vertical direction, the upper region is the upper region (first region) B1, the lower region is the lower region (second region) B2, and the upper region is A region sandwiched between B1 and the lower region B2 is defined as an intermediate region (third region) B3. The rotor core 222 has an upper ridge 224 and no lower ridge 225 in the upper region B1. Further, the rotor core 222 does not have the upper ridge portion 224 but has the lower ridge portion 225 in the lower region B2. Furthermore, the rotor core 222 does not have the upper ridge portion 224 and the lower ridge portion 225 in the intermediate region B3.

FIG. 9 is a graph showing the cogging torque waveform of the motor 10 including the rotor 220 of this modification. FIG. 9 shows the cogging torque waveform of the upper region B1 of the rotor 220, the cogging torque waveform of the lower region B2, the cogging torque waveform of the intermediate region B3, and the combined cogging torque waveform. .

When comparing the waveform of the cogging torque in the upper region B1 and the waveform of the cogging torque in the lower region B2, these are in opposite phases. That is, according to this modification, an antiphase can be generated in the cogging torque without skewing the magnet 23. For this reason, the cogging torque waveform in the upper region B1 and the cogging torque waveform in the lower region B2 cancel each other, and the vibration width of the cogging torque (the difference between the maximum value and the minimum value of the combined cogging torque) is kept small. be able to.

Intermediate region B3 is a region where the upper ridge portion 224 and the lower ridge portion 225 are not provided. When comparing the waveform of the cogging torque in the intermediate region B3 with the waveform of the combined cogging torque, the absolute value of the cogging torque in the intermediate region B3 is slightly larger than the absolute value of the combined cogging torque. The intermediate region B3 is provided in a region that is 1/3 of the entire length of the rotor core 222. Therefore, it is estimated that a cogging torque that is three times the cogging torque of the intermediate region B3 in FIG. 9 is generated in the rotor 220 in which the upper ridge 224 and the lower ridge 225 are not provided over the entire axial length. From this, it can be confirmed that the combined cogging torque can be reduced by providing the upper region B1 and the lower region B2.

According to this modification, a gap is provided between the upper ridge 224 and the lower ridge 225 in the axial direction. In addition, the axial dimension of the upper ridge 224, the axial dimension of the lower ridge 225, and the axial dimension of the gap coincide with each other. As a result, the rotor 220 is provided with an upper region B1, a lower region B2, and an intermediate region B3 having the same axial dimension. As a result, the same effect as when the magnet 23 is skewed in three stages can be obtained, and the cogging torque can be effectively reduced.

(Electric power steering device)
Next, an example of an apparatus in which the motor 10 of this embodiment (or each modification) 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. 10, the electric power steering apparatus 100 is mounted on a steering mechanism of a vehicle wheel 112. The electric power steering apparatus 100 is an apparatus that reduces the steering force by hydraulic pressure. The electric power steering apparatus 100 of this embodiment includes a motor 10, a steering shaft 114, an oil pump 116, and a control valve 117.

The steering shaft 114 transmits the input from the steering 111 to the axle 113 having the wheels 112. The oil pump 116 generates hydraulic pressure in the power cylinder 115 that transmits driving force by 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 for the oil pump 116.

The electric power steering apparatus 100 of this embodiment includes the motor 10 of this embodiment. For this reason, the electric power steering apparatus 100 which has an effect similar to the above-mentioned motor 10 is obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and, for example, as described below, the configuration can be changed without departing from the spirit of the present invention.

In the above-described embodiment, an example in which the motor 10 is mounted on the electric power steering apparatus 100 has been described, but this is not a limitation. The motor 10 can be used for various devices such as a pump, a brake, a clutch, a vacuum cleaner, a dryer, a ceiling fan, a washing machine, and a refrigerator.

In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modification, and a note, etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, but is limited only by the scope of the claims.

Claims

A shaft extending along the central axis;
A rotor core made of a magnetic material and fixed to the shaft;
A plurality of magnets fixed to the rotor core,
The rotor core has a plurality of magnet fixing surfaces arranged along the circumferential direction facing the radially outer side,
The magnet is fixed to each of the plurality of magnet fixing surfaces,
At least one of the plurality of magnet fixing surfaces is positioned on one side in the circumferential direction of the magnet fixed to the magnet fixing surface, and protrudes radially outward from the magnet fixing surface. Ridges are provided,
The at least one magnet fixing surface of the plurality of magnet fixing surfaces is located on the other circumferential side of the magnet fixed to the magnet fixing surface, and protrudes radially outward from the magnet fixing surface. Ridges are provided,
The first ridge extends along the axial direction from one axial end of the magnet fixing surface to the middle of the axial direction, and the second ridge is an axis of the magnet fixing surface. Extending along the axial direction from the other end of the direction to the middle of the axial direction,
The first ridge and the second ridge are rotors made of a magnetic material.
The rotor according to claim 1, wherein the magnet fixing surface provided with the first ridges and the magnet fixing surface provided with the second ridges are adjacent in the circumferential direction.
The rotor according to claim 1 or 2, wherein the number of the first ridges and the number of the second ridges coincide with each other.
The magnet fixing surface provided with the first ridges is arranged at equal intervals along the circumferential direction,
The rotor according to any one of claims 1 to 3, wherein the magnet fixing surfaces provided with the second ridges are arranged at equal intervals along a circumferential direction.
The rotor according to any one of claims 1 to 4, wherein the first protrusions and the second protrusions are provided on all the magnet fixing surfaces.
The length dimension along the axial direction of the first ridge portion and the length dimension along the axial direction of the second ridge portion coincide with each other, according to any one of claims 1 to 5. The described rotor.
The axial position of the end on the other axial side of the first ridge and the end on the one axial side of the second ridge coincide with each other. The rotor according to claim 1.
The axial position of the end on the other side in the axial direction of the first ridge is located on the one side in the axial direction from the axial position of the end on the one side in the axial direction of the second ridge. The rotor according to any one of claims 1 to 6.
The distance along the axial direction between the end on the other axial side of the first ridge and the end on the one axial side of the second ridge is the distance between the first ridge and the first ridge The rotor according to claim 8, which coincides with a length dimension along the axial direction of the second ridge portion.
The first protrusion is in contact with an end surface on one circumferential side of the magnet,
The rotor according to any one of claims 1 to 9, wherein the second ridge portion is in contact with an end surface on the other circumferential side of the magnet.
The rotor core is composed of a plurality of electromagnetic steel plates laminated along the axial direction,
The rotor according to any one of claims 1 to 10, wherein the first and second ridges are part of the electromagnetic steel sheet.
The rotor according to any one of claims 1 to 11, wherein the rotor core is provided with a plurality of holes penetrating along the axial direction and arranged along the circumferential direction.
The rotor core is provided with a plurality of grooves extending between the magnet fixing surfaces adjacent to each other along the circumferential direction and extending along the axial direction,
The groove is
The rotor according to any one of claims 1 to 12, wherein the groove portion opens radially outward and the groove width decreases toward the radially outer side.
A rotor according to any one of claims 1 to 13;
And a stator facing the rotor with a gap in the radial direction.
An electric power steering apparatus comprising the motor according to claim 14.