CN113472109A - Motor - Google Patents

Abstract

The invention provides a motor having a stator and a pair of rotors stacked in an axial direction. The rotor includes an inner core portion, a first outer core portion, a second outer core portion, a first magnet disposed radially outward of the first outer core portion, a second magnet disposed radially between the inner core portion and the second outer core portion, and a holder. The second outer core portion has an entrance portion that is a hole extending in the axial direction and surrounded by the second outer core portion in a direction intersecting the axial direction or a hole surrounded by the second outer core portion and the second magnet. The holder has a first holding portion that enters the entry 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 one 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; a second magnet disposed radially between the inner core portion and the second outer core portion; and a resin-made holder that holds at least the second outer core portion. The second outer core portion has an entrance portion that is a hole extending in the axial direction and surrounded by the second outer core portion in a direction intersecting the axial direction or a hole surrounded by the second outer core portion and the second magnet. The holder has a first holding portion that enters the entry 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. 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, and corresponds to the cross-section III-III in fig. 1.

Fig. 7 is a cross-sectional view showing a part of a rotor of a motor according to a modification of the present embodiment, and corresponds to the section IV-IV in fig. 1.

Fig. 8 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: motor, 20: rotor, 20A: first rotor, 20B: second rotor, 24: inner core portion, 25: first outer iron core portion, 26: second outer iron core portion, 26 b: entry portion, 26 c: first hole portion, 26 d: second hole portion, 27: first magnet, 28: second magnet, 28 a: radially outer side surface of second magnet, 29: a groove part; 30: stator, 40: cage, 41: first holding portion, 42: second holding portion, 43: connection portion, 51: first magnetic pole portion, 52: second magnetic pole portion, J: a central axis.

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". 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 is cylindrical and extends 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 radially outer side surface 28a is a flat surface extending in a direction perpendicular to the radial direction. The radially inner surface 28b is flat and extends in a direction perpendicular to the radial direction. The second magnet 28 is provided with a pair of second side surfaces 28 c. Each second side surface 28c is a flat surface extending in a direction perpendicular to the circumferential direction. 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.

In a sectional view perpendicular to the center axis J, the length of the first side surface 27c is shorter than the length of the second side surface 28 c. In the present embodiment, the radially outer surface 27a of the first magnet 27 is formed in a convex curved surface shape bulging radially outward, and the radially outer surface 28a of the second magnet 28 is formed in a flat surface shape. The radially inner surface 27b of the first magnet 27 and the radially inner surface 28b of the second magnet 28 are both flat. Therefore, when the length of the first side surface 27c is smaller than the length of the second side surface 28c in a cross-sectional view perpendicular to the central axis J, the balance between the volume of the first magnet 27 and the volume of the second magnet 28 is easily obtained.

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 radially outer surface 25a of the first outer core portion 25 is positioned radially inward of the radially outer surface 28a of the second magnet 28. According to the present embodiment, the radial dimension, i.e., the thickness, of the first magnet 27 located radially outward of the first outer core portion 25 can be secured to be large. Therefore, the pair of first side surfaces 27c can be stably provided on the first magnet 27. For example, unlike the present embodiment, when the circumferential end of the radially outer surface 27a of the first magnet 27 and the circumferential end of the radially inner surface 27b of the first magnet 27 are directly connected to each other to form a sharp corner, the corner is easily broken, and therefore, there is a possibility that a problem occurs in order to ensure handling at the time of manufacturing the motor and stable motor performance, that is, quality. On the other hand, according to the present embodiment, the angular defect of the first magnet 27 is suppressed, and the motor 10 having stable quality can be efficiently manufactured.

In the above configuration, in other words, the radially outer surface 28a of the second magnet 28 is positioned radially outward of the radially outer surface 25a of the first outer core portion 25. Therefore, the second magnet 28 is disposed closer to the stator 30 in the radial direction. That is, the second magnet 28 can be disposed close to the stator 30 located radially outward of the second magnet 28. This can stably secure the magnetic force of the second magnet 28 while suppressing the volume of the second magnet 28, that is, the amount of magnet used.

The radially inner surface 28b of the second magnet 28 is located radially inward of the radially outer surface 25a of the first outer core portion 25. According to the present embodiment, the radial dimension, i.e., the thickness, of the second magnet 28 is ensured. Therefore, the magnetic force of the second magnet 28 can be stably ensured.

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 seat portion 25b contacts the first magnet 27 from the radially inner side, and the circumferential dimension thereof becomes smaller 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 radially outer side surface of the second outer core portion 26 is a convex curved surface bulging radially outward. The radially inner side surface of the second outer core portion 26 is in a flat shape extending in a direction perpendicular to the radial direction. The radial dimension of the circumferential center portion of the second outer core portion 26 is larger than the radial dimensions of both end portions in the circumferential direction. The radial dimension of the second outer core portion 26 increases from both end portions in the circumferential direction toward the center portion in the circumferential direction.

The second outer core portion 26 has a corner portion 26a and an entrance portion 26 b. The corner 26a is disposed at an end in the circumferential direction of the second outer core portion 26. The corner 26a protrudes toward the circumferential direction. The corner 26a is located at a connection portion between the circumferential end of the radially outer surface of the second outer core portion 26 and the circumferential end of the radially inner surface of the second outer core portion 26. The second outer core portion 26 is provided with a pair of corner portions 26 a. According to the present embodiment, the second outer core portion 26 has the corner portion 26a without the side surface facing the circumferential direction, and therefore, the radial dimension, that is, the thickness of the second outer core portion 26 is easily suppressed to be small. This allows the second magnet 28 disposed radially inward of the second outer core portion 26 to be disposed closer to the stator 30 in the radial direction. That is, the second magnet 28 can be disposed close to the stator 30 located radially outward of the second magnet 28. The magnetic force of the second magnet 28 can be stably ensured while the volume of the second magnet 28, that is, the amount of magnet used, is suppressed.

The entrance portion 26b opens at least to an end surface of the second outer core portion 26 facing the axial direction. In the present embodiment, the entry portions 26b penetrate the second outer core portion 26 in the axial direction, and are open at the upper end surface and the lower end surface of the second outer core portion 26, respectively. The entrance portion 26b is a hole extending in the axial direction and surrounded by the second outer core portion 26 in a direction intersecting the axial direction or a hole surrounded by the second outer core portion 26 and the second magnet 28. That is, the entrance portion 26b is a hole extending in the axial direction inside the second magnetic pole portion 52. In the present embodiment, the entering portion 26b is located at the circumferential center portion of the second outer core portion 26. According to the present embodiment, the entering portion 26b is disposed in the circumferential central portion of the second outer core portion 26 having a larger radial dimension, i.e., a larger thickness, than the circumferential both end portions, so that it is easy to ensure the rigidity of the second outer core portion 26 and to suppress the occurrence of magnetic saturation.

The circumferential dimension of the entry portion 26b is longer than the radial dimension. The entry portion 26b extends in the circumferential direction when viewed from the axial direction. According to the present embodiment, the volume of the entrance portion 26b can be ensured to be large while ensuring the rigidity of the second outer core portion 26 that expands in the direction perpendicular to the radial direction. The configuration of the inlet portion 26b other than the above will be described later.

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. At least a part of the groove portion 29 has a smaller circumferential groove width toward the radially outer side. In the present embodiment, the radially inner end portion of the groove portion 29 is narrower in the circumferential direction toward the radially outer side. According to the present embodiment, the second holding portion 42, which will be described later, of the retainer 40 disposed in the groove portion 29 is prevented from coming out from the groove portion 29 to the outside in the radial direction.

The holder 40 is made of resin. As shown in fig. 1, 3, and 4, the holder 40 holds at least the second outer core portion 26. The holder 40 has a first holding portion 41, a second holding portion 42, and a connecting portion 43. The first holding portion 41 enters the entering portion 26 b. That is, the first holding portion 41 is disposed in the entry portion 26 b. The first holding portion 41 extends in the axial direction. Each of the second magnetic pole portions 52 is provided with one first holding portion 41. That is, the first holding portion 41 is provided in plurality. The number of the first holding portions 41 is the same as the number of the second magnetic pole portions 52.

In the present embodiment, the first holding portion 41 of the holder 40 enters the entering portion 26b of the second outer core portion 26, and positioning and fixing of the second outer core portion 26 become easy. Specifically, for example, unlike the present embodiment, when the second magnet 28 and the second outer core portion 26 are pressed from the circumferential direction and the radial direction outside only by the second holding portion 42 disposed in the groove portion 29 of the rotor 20, if a variation occurs in the circumferential dimension of the second magnet 28 and the circumferential dimension of the second outer core portion 26 due to a manufacturing error, a design tolerance, or the like, it may be impossible to position or fix any of the members. On the other hand, according to the present embodiment, for example, even when a deviation occurs between the circumferential dimension of the second magnet 28 and the circumferential dimension of the second outer core portion 26, the second outer core portion 26 can be stably fixed in a positioned state by the first holding portion 41. Therefore, the motor performance is stable. In addition, the strength against the centrifugal force, i.e., the rotational strength, when the rotor 20 rotates can be stably increased.

In the present embodiment, the entry portion 26b is a groove that opens at the radially inner side surface of the second outer core portion 26 and extends in the axial direction. Therefore, the first holding portion 41 contacts the radially outer surface 28a of the second magnet 28. According to the present embodiment, the second magnet 28 can be directly pressed from the radial outside by the first holding portion 41. Therefore, the rotation strength of the rotor 20 during rotation can be more stably increased.

The circumferential groove width of the entry portion 26b increases toward the radially outer side. According to the present embodiment, the first holding portion 41 is restrained from coming out in the radial direction from the entering portion 26 b. That is, the second outer core portions 26 are restrained from moving radially outward relative to the first holding portions 41 when the rotor 20 rotates. Therefore, the rotation strength of the rotor 20 during rotation is more stably improved.

The second holding portion 42 is disposed in the groove portion 29. The second holding portion 42 extends in the axial direction. The second holding portion 42 is provided in plurality at intervals from each other in the circumferential direction. The number of the second holding portions 42 is the same as the number of the groove portions 29. The second 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 from the circumferential direction by the second holding portion 42. The first magnet 27 and the second magnet 28 are prevented from moving in the circumferential direction.

The second holding portion 42 has a flange portion 42 a. The flange portion 42a protrudes in the circumferential direction from a radially outer end portion of the second holding portion 42. Each second holding portion 42 is provided with a pair of flange portions 42 a. The pair of flange portions 42a project in mutually different directions from the second holding portion 42 in the circumferential direction. One of the pair of flange portions 42a contacts the second outer core portion 26 from the radial outside, and presses the second magnet 28 from the radial outside via the second outer core portion 26. The other of the pair of flanges 42a contacts the first magnet 27 from the radially outer side. According to the present embodiment, the second holding portion 42 suppresses the movement of the first magnet 27 outward in the radial direction. Further, the first holding portion 41 and the second holding portion 42 suppress the movement of the second outer core portion 26 and the second magnet 28 to the outside in the radial direction.

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 first holding portion 41 and an axial end of each second holding portion 42. That is, the connecting portion 43 is connected to the first holding portion 41 and the second holding portion 42. The connecting portion 43, the plurality of first holding portions 41, and the plurality of second holding portions 42 are portions of one member. That is, the connecting portion 43, the first holding portion 41, and the second holding portion 42 are integrally provided. According to the present embodiment, the first holding portion 41 and the second holding portion 42 are coupled by the coupling portion 43, and therefore the strength of the entire retainer 40 is improved. The holding state of the holder 40 is maintained well, and the rotation strength of the rotor 20 at the time of rotation is more stably improved.

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.

In the above embodiment, the example in which the entry portion 26b is a groove that is open on the inner surface in the radial direction of the second outer core portion 26 and extends in the axial direction has been described, but the present invention is not limited to this. The entry portion 26b may be a hole extending in the axial direction inside the second outer core portion 26. That is, the inlet portion 26b may not be opened to the radially inner side surface of the second outer core portion 26. In this case, the first holding portion 41 is restrained from coming out in the radial direction from the entering portion 26 b. That is, the second outer core portions 26 are restrained from moving radially outward relative to the first holding portions 41 when the rotor 20 rotates. Therefore, the rotational strength of the rotor 20 during rotation is more stably improved.

Fig. 6 and 7 show a modification of the motor 10 described in the above embodiment. In the rotor 20 of this modification, the inlet portion 26b includes the first hole 26c and the second hole 26 d. The first hole portion 26c extends in the axial direction. The first hole 26c is open at an end surface of the second outer core portion 26 facing the axial direction. In the illustrated example, the first hole 26c has a circular hole shape. The second hole 26d is continuous with the first hole 26c and extends in a direction intersecting the first hole 26 c. In the illustrated example, the second hole 26d extends radially inward from a connection portion with the first hole 26c, and opens at a radially inner side surface of the second outer core portion 26. That is, the second hole 26d faces the radially outer surface 28a of the second magnet 28. The second hole 26d may extend radially outward or in the circumferential direction from a connection portion with the first hole 26 c. In addition, only one second hole 26d may be provided, or a plurality of second holes may be provided at intervals in the axial direction.

The first holding portion 41 enters the first hole portion 26c and the second hole portion 26 d. The first holding portion 41 contacts the radially outer surface 28a of the second magnet 28. According to this modification, the first holding portion 41 is restrained from coming out in the radial direction from the entry portion 26b by the first hole portion 26c when the rotor 20 rotates. Further, the second hole 26d suppresses the relative movement between the entering portion 26b and the first holding portion 41 in the axial direction. That is, the second outer core portions 26 are restrained from moving in the axial direction relative to the first holding portions 41. The second magnet 28 can be directly pressed from the radial outside by the first holding portion 41. Therefore, the rotational strength of the rotor 20 during rotation is more stably improved.

In the above embodiment, the configuration 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 is exemplified, but the present invention is not limited thereto. Fig. 8 shows a modification of the motor 10 described in the above embodiment. In this modification, as shown in fig. 8, 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.

In addition, the respective configurations described in the above-described embodiments, modifications, and the like may be combined, and addition, omission, replacement, and other changes of the configurations 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 (9)

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;

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

a resin-made cage for holding at least the second outer core portion,

the second outer core portion has an entrance portion that is a hole extending in the axial direction and surrounded by the second outer core portion in a direction intersecting the axial direction or a hole surrounded by the second outer core portion and the second magnet,

the holder has a first holding portion that enters the entry 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,

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,

a radial dimension of a circumferential central portion of the second outer core portion is larger than radial dimensions of both circumferential end portions,

the entrance portion is located at a central portion in a circumferential direction of the second outer core portion.

3. The motor according to claim 1 or 2,

the inlet portion is a groove that opens at a radially inner side surface of the second outer core portion and extends in the axial direction.

4. The motor of claim 3,

the circumferential groove width of the inlet portion increases toward the radially outer side.

5. The motor according to claim 1 or 2,

the entrance portion is a hole extending in the axial direction inside the second outer core portion.

6. The motor according to claim 1 or 2,

the entry portion has:

a first hole portion extending in an axial direction; and

and a second hole portion connected to the first hole portion and extending in a direction intersecting the first hole portion.

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

the first holding portion is in contact with a radially outer side surface of the second magnet.

8. The motor according to any one of claims 1 to 7,

the rotor has a groove portion recessed radially inward from a radially outer surface of the rotor and extending in an axial direction,

the groove portion is located between the first magnet and the second magnet adjacent in the circumferential direction,

the retainer has a second retaining portion disposed in the groove portion,

the second holding portion is in contact with the first magnet and the second magnet in the circumferential direction.

9. The motor of claim 8,

the retainer has a connecting portion disposed on an end surface of the rotor facing the axial direction and extending in the circumferential direction,

the connecting portion is connected to the first holding portion and the second holding portion.

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