CN110971034A - Motor with a stator having a stator core - Google Patents

Abstract

The present invention provides a motor, one embodiment of which includes: a rotor having a central axis; and a stator that is radially opposed to the rotor. The rotor has: a rotor core having a plurality of electromagnetic steel plates stacked in an axial direction; a magnet disposed on a surface of the rotor core facing in a radial direction; and a resin magnet holder provided on the rotor core and holding the magnet. The rotor core has a 1 st rotor core portion arranged in a 1 st region in the axial direction. The 1 st rotor core portion has a groove portion that is recessed in the radial direction from a surface of the 1 st rotor core portion facing the radial direction and extends in the axial direction. The plurality of electromagnetic steel sheets have: a 1 st electromagnetic steel sheet having a recess on a surface thereof facing a radial direction, the recess constituting a part of an axial direction of the groove; and a 2 nd electromagnetic steel sheet having a closing portion that overlaps and covers the recess when viewed in the axial direction. The 2 nd electromagnetic steel plate is disposed at an end in the axial direction of the 1 st rotor core portion.

Description

Motor with a stator having a stator core

Technical Field

The present invention relates to a motor.

Background

The motor includes a rotor that rotates about a central axis and a stator that faces the rotor in a radial direction. The rotor has a rotor core and a magnet. The rotor core is formed of a plurality of electromagnetic steel plates stacked in the axial direction. The motor disclosed in patent document 1 is an inner rotor type motor in which magnets are arranged on the outer surface of a rotor core in the radial direction. In patent document 1, a gap is provided between the rotor core and the magnet, thereby improving the flow of magnetic flux.

Patent document 1: japanese patent No. 5571480

In order to fix the magnet to the rotor core, it is conceivable to provide a magnet holder on the rotor core by resin molding. However, if the gap is provided as in patent document 1, the molten resin flows into the gap and solidifies, and the magnet is arranged in a state of being lifted from the rotor core in the radial direction by the resin, and the magnetic force may be reduced (demagnetized).

Disclosure of Invention

In view of the above circumstances, an object of the present invention is to provide a motor in which a rotor core and a magnet can be stably brought into contact with each other and a decrease in magnetic force of the magnet can be suppressed.

One embodiment of a motor of the present invention includes: a rotor having a central axis; and a stator that is opposed to the rotor in a radial direction, the rotor including: a rotor core having a plurality of electromagnetic steel plates stacked in an axial direction; a magnet disposed on a surface of the rotor core facing in a radial direction; and a resin magnet holder that is provided on the rotor core and holds the magnet, wherein the rotor core includes a 1 st rotor core portion, the 1 st rotor core portion is disposed in a 1 st region in an axial direction, the 1 st rotor core portion includes a groove portion that is recessed in a radial direction from a surface of the 1 st rotor core portion facing the radial direction and extends in the axial direction, and the plurality of electromagnetic steel plates include: a 1 st electromagnetic steel sheet having a recess on a surface thereof facing a radial direction, the recess constituting a part of the groove in an axial direction; and a 2 nd magnetic steel sheet having a closed portion overlapping the recess and covering the recess as viewed in an axial direction, the 2 nd magnetic steel sheet being disposed at an end portion in the axial direction of the 1 st rotor core portion.

According to the motor of one embodiment of the present invention, the rotor core can be stably brought into contact with the magnet, and a decrease in the magnetic force of the magnet can be suppressed.

Drawings

Fig. 1 is a schematic sectional view of a motor according to an embodiment.

Fig. 2 is a perspective view showing a rotor according to an embodiment, and the magnet holder is not shown.

Fig. 3 is a perspective view showing a rotor core according to an embodiment.

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

Fig. 5 is a partial sectional view showing a portion of the V-V section of fig. 1.

Fig. 6 is a partial sectional view showing a portion of the section VI-VI of fig. 1.

Fig. 7 is a perspective view showing a first rotor core portion 1 and a magnet holder according to an embodiment.

Fig. 8 is a perspective view showing a first rotor core portion 1 and a magnet holder according to an embodiment.

Fig. 9 is a sectional perspective view showing a part of the inside of a mold for resin molding the magnet holder.

Fig. 10 is a perspective view showing a first rotor core portion 1 and a magnet holder according to a modification of the embodiment.

Description of the reference symbols

10: a motor; 20: a rotor; 22: 1 st rotor iron core portion; 22 a: 1 st magnet installation surface; 23: a 2 nd rotor iron core portion; 23 a: a 2 nd magnet mounting surface; 25: a magnet; 25 b: a radially inner surface (a surface of the magnet facing radially); 26: a magnet holder; 26 b: a radial pressing part; 26 c: an axial pressing portion; 27: a rotor core; 28: a groove part; 30: a stator; 41: a 1 st electromagnetic steel sheet; 41 b: a 1 st magnet attachment portion (a surface of the 1 st electromagnetic steel sheet facing the radial direction); 41 e: a recess; 42: a 2 nd electromagnetic steel sheet; 42 b: a 1 st magnet mounting portion (a surface of a 2 nd electromagnetic steel plate facing in a radial direction); 42 e: a closing part; j: a central axis; s1: region 1; s2: region 2.

Detailed Description

In the following description, the axial direction of the center axis J, i.e., the direction parallel to the vertical direction, is simply referred to as the "axial direction", the radial direction about the center axis J is simply referred to as the "radial direction", and the circumferential direction about the center axis J is simply referred to as the "circumferential direction". In the present embodiment, the upper side (+ Z) corresponds to one axial side, and the lower side (-Z) corresponds to the other axial side. The side that advances in the counterclockwise direction of the circumferential direction when the motor 10 is viewed from above, i.e., the side that advances in the direction of the arrow θ, is referred to as "circumferential side". One side that advances in the clockwise direction in the circumferential direction when the motor 10 is viewed from above, that is, one side that advances 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 only names for describing relative positional relationships 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 the names.

Although not particularly shown, the motor 10 of the present embodiment is mounted on, for example, an electric power steering apparatus. The electric power steering apparatus is mounted on a steering mechanism of a wheel of an automobile. An electric power steering apparatus is an apparatus that reduces a steering force by a motor.

As shown in fig. 1, the motor 10 of the present embodiment includes a rotor 20 having a central axis J, a stator 30, a housing 11, and a plurality of bearings 15 and 16. The motor 10 of the present embodiment is an inner rotor type motor. The rotor 20 is disposed radially inward of the stator 30 and rotates about the central axis J with respect to the stator 30. As shown in fig. 1 to 8, the rotor 20 includes a shaft 21, a rotor core 27, a magnet 25, and a magnet holder 26.

The housing 11 is cylindrical having a top and a bottom. The housing 11 has a peripheral wall portion 11a, a top wall portion 11b, a bottom wall portion 11c, and a bearing holder 11 d. The peripheral wall portion 11a is cylindrical. The top wall 11b is plate-shaped and closes the upper opening of the peripheral wall 11 a. The bottom wall 11c is plate-shaped and closes the opening on the lower side of the peripheral wall 11 a. The bottom wall portion 11c holds the bearing 16. The bearing holder 11d is fixed to the inner peripheral surface of the peripheral wall portion 11 a. The bearing holder 11d holds the bearing 15.

The shaft 21 extends in the vertical direction around the center 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 the plurality of bearings 15 and 16 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.

The shaft 21 is fixed to the rotor core 27 by press fitting, bonding, or the like. That is, the rotor core 27 is fixed to the shaft 21. The shaft 21 may be fixed to the rotor core 27 via a resin member or the like. That is, the shaft 21 and the rotor core 27 are directly or indirectly fixed. The shaft 21 is not limited to the cylindrical shape of the present embodiment, and may be, for example, a cylindrical shape.

The rotor core 27 has a cylindrical shape. The rotor core 27 has a shaft hole 27 a. The shaft hole 27a is disposed in the center of the rotor core 27 when viewed in the axial direction. The shaft hole 27a is located on the center axis J and extends in the axial direction. The shaft hole 27a penetrates the rotor core 27 in the axial direction. The shaft hole 27a axially penetrates the two 1 st rotor core portions 22 and the one 2 nd rotor core portion 23, which will be described later. The shaft hole 27a is circular hole-shaped. The shaft 21 is inserted into the shaft hole 27 a. In a cross section perpendicular to the center axis J (hereinafter, may be simply referred to as a cross section), the outer shape of the rotor core 27 is substantially polygonal. In the example of the present embodiment, the outer shape of the rotor core 27 is substantially octagonal in cross section. The rotor core 27 is a magnetic member. The rotor core 27 has a plurality of electromagnetic steel plates stacked in the axial direction. The rotor core 27 is a steel sheet laminate formed by laminating a plurality of electromagnetic steel sheets in the axial direction.

The rotor core 27 has a 1 st rotor core portion 22 and a 2 nd rotor core portion 23. The 1 st rotor core portion 22 is disposed in the 1 st region S1 in the axial direction of the rotor core 27. The 1 st region S1 is a region of at least a part of the rotor core 27 in the axial direction. The 1 st region S1 may also be referred to as a level 1 or a portion 1. The 2 nd rotor core portion 23 is disposed in a 2 nd region S2 of the rotor core 27, which is different from the 1 st region S1 in the axial direction. The 2 nd region S2 is a region of at least a part of the rotor core 27 in the axial direction. The 2 nd region S2 may also be referred to as a level 2 or a part 2. In the present embodiment, a total of three first rotor core portions 22 and three second rotor core portions 2 are arranged in the axial direction so as to be alternately aligned. That is, the rotor core 27 is a three-stage type rotor core.

In the present embodiment, the rotor core 27 includes two 1 st rotor core portions 22 arranged at intervals in the axial direction and one 2 nd rotor core portion 23 arranged between the two 1 st rotor core portions 22 in the axial direction. The two 1 st rotor core portions 22 are disposed at both axial end portions of the rotor core 27. One 2 nd rotor core portion 23 is disposed at the center portion in the axial direction in the rotor core 27. That is, the rotor 20 has two 1 st regions S1 arranged to be separated in the axial direction, and the two 1 st regions S1 are located at both ends in the axial direction in the rotor 20. The rotor 20 has a 2 nd section S2, and a 2 nd section S2 is located between the two 1 st sections S1 in the axial direction in the rotor 20.

In the example of the present embodiment, the axial length of the 1 st rotor core portion 22 and the axial length of the 2 nd rotor core portion 23 are different from each other. Specifically, the axial length of the 2 nd rotor core portion 23 is slightly larger than the axial length of the 1 st rotor core portion 22. However, without being limited thereto, the axial length of the 1 st rotor core portion 22 and the axial length of the 2 nd rotor core portion 23 may be the same as each other. The outer diameter of the 1 st rotor core portion 22 and the outer diameter of the 2 nd rotor core portion 23 are identical to each other.

The 1 st rotor core portion 22 has a 1 st magnet attachment surface 22a, a through hole 22b, a holder attachment groove 22c, and a groove portion 28. The 1 st magnet attachment surface 22a is disposed on a surface of the 1 st rotor core portion 22 facing in the radial direction. In the present embodiment, the 1 st magnet attachment surface 22a is disposed on the surface of the 1 st rotor core portion 22 facing the radially outer side. A magnet 25 is disposed on the 1 st magnet attachment surface 22 a. The 1 st magnet attachment surface 22a is in contact with the magnet 25 in the radial direction. The 1 st magnet attachment surface 22a is disposed in plurality in a circumferential direction on the radially outer surface of the 1 st rotor core portion 22. In the example of the present embodiment, the 1 st rotor core portion 22 has eight 1 st magnet attachment surfaces 22a arranged in the circumferential direction on the radially outer surface of the 1 st rotor core portion 22. The 1 st magnet attachment surfaces 22a are in contact with the radially inner surfaces 25b of the magnets 25.

In the present embodiment, the 1 st magnet attachment surface 22a is a flat surface extending in a direction perpendicular to the radial direction. That is, the 1 st magnet attachment surface 22a is perpendicular to the radial direction. In a cross section perpendicular to the central axis J, the 1 st magnet attachment surface 22a is linear extending in a direction perpendicular to the radial direction. The 1 st magnet attachment surface 22a has a quadrangular shape when viewed from the radially outer side. In the example of the present embodiment, the 1 st magnet attachment surface 22a has a length in the axial direction larger than a length in the circumferential direction. That is, the 1 st magnet attachment surface 22a extends in the axial direction on the radially outer surface of the 1 st rotor core portion 22.

The through hole 22b penetrates the 1 st rotor core portion 22 in the axial direction. The plurality of through holes 22b are arranged in the 1 st rotor core portion 22 at intervals in the circumferential direction. In the example of the present embodiment, eight through holes 22b are arranged at equal intervals in the circumferential direction on the 1 st rotor core portion 22. The through hole 22b is disposed in the 1 st rotor core portion 22 at a position other than the outer end portion in the radial direction. That is, the through hole 22b is disposed at a radially inner end portion or a radially central portion of the 1 st rotor core portion 22 that does not affect the magnetic flux of the magnet 25. The through hole 22b has a circular shape in a cross section perpendicular to the center axis J. According to the present embodiment, the 1 st rotor core portion 22 is hollowed by the through hole 22b, and the weight and material cost of the 1 st rotor core portion 22 can be reduced.

The holder mounting groove 22c is recessed radially inward from the radially outer surface of the 1 st rotor core portion 22, and extends in the axial direction. The holder mounting groove 22c is disposed between a pair of circumferentially adjacent 1 st magnet mounting surfaces 22a on the radially outer surface of the 1 st rotor core portion 22, and opens radially outward. The holder mounting groove 22c is disposed on the radially outer surface of the 1 st rotor core portion 22 over the entire axial length of the 1 st rotor core portion 22. The plurality of cage attachment grooves 22c are arranged on the radially outer surface of the 1 st rotor core portion 22 at intervals in the circumferential direction. In the example of the present embodiment, eight cage attachment grooves 22c are arranged at equal intervals in the circumferential direction in the 1 st rotor core portion 22.

The groove width of the retainer mounting groove 22c becomes smaller toward the radially outer side. That is, the circumferential width dimension of the retainer mounting groove 22c decreases toward the radially outer side. The opening portion located at the radial outer end portion of the holder mounting groove 22c opens between the circumferential end portions of the pair of 1 st magnet mounting surfaces 22a adjacent in the circumferential direction. In a cross section perpendicular to the center axis J, the holder mounting groove 22c is, for example, wedge-shaped.

The groove portion 28 is recessed in the radial direction from a radially facing surface of the 1 st rotor core portion 22, and extends in the axial direction. In the present embodiment, the groove portion 28 is recessed radially inward from the radially outward surface of the 1 st rotor core portion 22, and opens radially outward. The groove 28 is disposed on the radially outer surface of the 1 st rotor core portion 22, and extends in the axial direction at a portion other than the axial end portion of the radially outer surface. A plurality of the groove portions 28 are arranged on the radially outer surface of the 1 st rotor core portion 22 at intervals in the circumferential direction.

The groove 28 is disposed radially inward of the magnet 25 on the radially outer surface of the 1 st rotor core portion 22. The groove 28 is disposed on the 1 st magnet attachment surface 22 a. The plurality of groove portions 28 are provided on the 1 st magnet attachment surface 22a at intervals in the circumferential direction. The groove portions 28 are disposed at both circumferential ends of the 1 st magnet attachment surface 22 a. In the example of the present embodiment, one groove 28 is disposed at each of both circumferential end portions of the 1 st magnet attachment surface 22 a.

The groove 28 is disposed on the 1 st magnet attachment surface 22a at a position inward in the circumferential direction from the circumferential ends 22 e. That is, the groove 28 is disposed on the circumferential central portion side of the 1 st magnet attachment surface 22a with respect to the circumferential both ends 22e of the 1 st magnet attachment surface 22 a. Circumferential both ends 22e of the 1 st magnet attachment surface 22a are in contact with circumferential both ends of the radially inner surface 25b of the magnet 25. Circumferential both ends 22e of the 1 st magnet attachment surface 22a are in contact with circumferential both ends of the radial inner surface 25b of the magnet 25 from the radially inner side.

The groove 28 forms a chamber as a nonmagnetic space on the 1 st magnet attachment surface 22 a. The groove 28 is a void filled with an atmosphere such as air. The groove 28 may also be referred to as a void. In the example of the present embodiment, the groove portion 28 has a substantially quadrangular shape in a cross section perpendicular to the center axis J. The inner surface of the groove portion 28 has an inner surface portion facing in the radial direction and an inner surface portion facing in the circumferential direction. The circumferential length of the groove 28 is greater than the radial length of the groove 28. In the present embodiment, in the cross section, the length of the groove portion 28 in the radial direction is constant along the direction in which the 1 st magnet attachment surface 22a extends. That is, in a cross-sectional view perpendicular to the central axis J, the 1 st magnet attachment surface 22a linearly extends in a direction perpendicular to the radial direction, and the radial dimension (depth) of the groove portion 28 is constant along the extending direction of the 1 st magnet attachment surface 22 a. The shape and position of the groove portion 28 in the cross section perpendicular to the center axis J are constant in the axial direction.

The groove portion 28 has a substantially quadrangular shape when viewed in the radial direction. The groove 28 has a rectangular shape when viewed in the radial direction. The axial length of the groove portion 28 is greater than the circumferential length of the groove portion 28. The groove 28 is disposed to overlap a portion other than the circumferential center portion of the radially outer surface 25a of the magnet 25 when viewed in the radial direction. In the present embodiment, the groove 28 is disposed to overlap with a portion of the radially outer surface 25a of the magnet 25 other than the portion located on the outermost side in the radial direction (i.e., the top portion) when viewed in the radial direction. The function (action and effect) of the groove 28 will be described later.

The 2 nd rotor core portion 23 has a 2 nd magnet attachment surface 23a, a through hole 23b, and a holder attachment groove 23 c. The 2 nd rotor core portion 23 is not provided with the groove portion 28. That is, the 2 nd rotor core portion 23 does not have the groove portion 28 on the surface of the 2 nd rotor core portion 23 facing in the radial direction. The groove 28 is not disposed on the 2 nd magnet attachment surface 23 a.

The 2 nd magnet attachment surface 23a is disposed on a surface of the 2 nd rotor core portion 23 facing in the radial direction. In the present embodiment, the 2 nd magnet attachment surface 23a is disposed on the surface of the 2 nd rotor core portion 23 facing the radially outer side. A magnet 25 is disposed on the 2 nd magnet attachment surface 23 a. The 2 nd magnet mounting surface 23a is in contact with the magnet 25 in the radial direction. The 2 nd magnet attachment surface 23a is disposed in plurality in a row in the circumferential direction on the outer surface in the radial direction of the 2 nd rotor core portion 23. In the example of the present embodiment, the 2 nd rotor core portion 23 has eight 2 nd magnet attachment surfaces 23a arranged in the circumferential direction on the outer surface in the radial direction of the 2 nd rotor core portion 23. The 2 nd magnet attachment surfaces 23a are in contact with the radially inner surfaces 25b of the magnets 25.

In the present embodiment, the 2 nd magnet attachment surface 23a is a flat surface extending in a direction perpendicular to the radial direction. That is, the 2 nd magnet attachment surface 23a is perpendicular to the radial direction. In a cross section perpendicular to the central axis J, the 2 nd magnet attachment surface 23a is linear extending in a direction perpendicular to the radial direction. The 2 nd magnet mounting surface 23a has a quadrangular shape when viewed from the outside in the radial direction. In the example of the present embodiment, the axial length of the 2 nd magnet attachment surface 23a is larger than the circumferential length. That is, the 2 nd magnet attachment surface 23a extends in the axial direction on the radially outer surface of the 2 nd rotor core portion 23.

The circumferential position of the 1 st magnet attachment surface 22a of the 1 st rotor core portion 22 and the circumferential position of the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23 are different from each other. That is, the circumferential position of the 1 st magnet attachment surface 22a and the circumferential position of the 2 nd magnet attachment surface 23a are shifted from each other. In the example of the present embodiment, the 1 st magnet attachment surface 22a of one 1 st rotor core portion 22 located on the upper side (+ Z side) of the two 1 st rotor core portions 22 is offset to the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23 on the one circumferential side (+ θ side). Further, the 1 st magnet attachment surface 22a of the other 1 st rotor core portion 22 positioned on the lower side (-Z side) of the two 1 st rotor core portions 22 is offset to the other side (- θ side) in the circumferential direction with respect to the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23.

In the present embodiment, the rotor core 27 has a shape symmetrical with respect to the 2 nd rotor core portion 23 by rotating 180 ° as viewed in the radial direction. That is, the rotor core 27 has a shape symmetrical with a rotation of 180 ° around a predetermined center point located at the center of the 2 nd rotor core portion 23 in the axial direction, as viewed in the radial direction. According to the present embodiment, it is possible to suppress the occurrence of restrictions in the axial direction of the rotor core 27 when manufacturing the motor 10. Errors in the vertical mounting direction of the rotor core 27 can be eliminated, and manufacturing is facilitated.

The through hole 23b axially penetrates the 2 nd rotor core portion 23. The 2 nd rotor core portion 23 is provided with a plurality of through holes 23b spaced apart from each other in the circumferential direction. In the example of the present embodiment, eight through holes 23b are arranged at equal intervals in the circumferential direction in the 2 nd rotor core portion 23. The through hole 23b is disposed in the 2 nd rotor core portion 23 at a position other than the outer end portion in the radial direction. That is, the through hole 23b is disposed at a radially inner end portion or a radially central portion of the 2 nd rotor core portion 23 that does not affect the magnetic flux of the magnet 25. The through hole 23b has a circular shape in a cross section perpendicular to the center axis J. According to the present embodiment, the 2 nd rotor core portion 23 is made hollow by the through hole 23b, and the weight and material cost of the 2 nd rotor core portion 23 can be reduced.

The cage attachment groove 23c is recessed radially inward from the radially outer surface of the 2 nd rotor core portion 23, and extends in the axial direction. The holder mounting groove 23c is disposed between a pair of 2 nd magnet mounting surfaces 23a adjacent in the circumferential direction on the radial outer surface of the 2 nd rotor core portion 23, and is open radially outward. The holder mounting groove 23c is disposed on the radially outer surface of the 2 nd rotor core portion 23 over the entire axial length of the 2 nd rotor core portion 23. The plurality of cage attachment grooves 23c are arranged on the radially outer surface of the 2 nd rotor core portion 23 at intervals in the circumferential direction. In the example of the present embodiment, eight cage attachment grooves 23c are arranged at equal intervals in the circumferential direction on the 2 nd rotor core portion 23.

The groove width of the holder mounting groove 23c becomes smaller toward the radial outside. That is, the circumferential width dimension of the retainer mounting groove 23c becomes smaller toward the radially outer side. The opening portion located at the radially outer end portion of the holder mounting groove 23c opens between the circumferential ends of the pair of circumferentially adjacent 2 nd magnet mounting surfaces 23 a. In a cross section perpendicular to the center axis J, the holder mounting groove 23c is, for example, wedge-shaped.

The circumferential position of the holder mounting groove 22c of the 1 st rotor core portion 22 and the circumferential position of the holder mounting groove 23c of the 2 nd rotor core portion 23 are different from each other. That is, the circumferential position of the holder mounting groove 22c and the circumferential position of the holder mounting groove 23c are shifted from each other. A magnet holder 26 is fixed to each of the holder mounting grooves 22c and 23 c. According to the present embodiment, by providing the wedge-shaped holder mounting grooves 22c, 23c on the outer surface in the radial direction of the rotor core 27, the magnet holder 26 that prevents the magnet from coming off in the radial direction can be provided to the holder mounting grooves 22c, 23c, and the magnet 25 can be held at least in the radial direction by the magnet holder 26. The structure and function of the magnet holder 26 will be described later.

The 1 st rotor core portion 22 has a plurality of electromagnetic steel sheets stacked in the axial direction. The 1 st rotor core portion 22 is a steel sheet laminate body formed by laminating a plurality of electromagnetic steel sheets in the axial direction. The 2 nd rotor core portion 23 has a plurality of electromagnetic steel sheets stacked in the axial direction. The 2 nd rotor core portion 23 is a steel sheet laminate body configured by laminating a plurality of electromagnetic steel sheets in the axial direction. The plurality of electromagnetic steel sheets constituting the 1 st rotor core portion 22 and the 2 nd rotor core portion 23 will be described later.

The magnet 25 is a permanent magnet. The magnet 25 is disposed on a surface of the rotor core 27 facing the radial direction. In the present embodiment, the magnet 25 is disposed on the radially outward surface of the rotor core 27. A plurality of magnets 25 are arranged in a circumferential direction on the outer surface of the rotor core 27 in the radial direction. A plurality of magnets 25 are arranged in a circumferential direction on the radially outer surface of the 1 st rotor core portion 22. A plurality of magnets 25 are arranged in a circumferential direction on the radially outer surface of the 2 nd rotor core portion 23. The plurality of magnets 25 are arranged at intervals in the circumferential direction. In the present embodiment, the plurality of magnets 25 are arranged at equal intervals in the circumferential direction. Holder mounting grooves 22c, 23c are disposed between a pair of circumferentially adjacent magnets 25. The magnets 25 are also arranged in the axial direction on the radially outer side surface of the rotor core 27. The magnet 25 forms a part of the radially outer surface of the rotor 20. That is, the radially outer surface 25a of the magnet 25 is a part of the radially outer surface of the rotor 20. The rotor 20 of the present embodiment is a Surface Magnet type (SPM) rotor in which a Magnet 25 is disposed on the outer Surface in the radial direction of the rotor 20.

The magnets 25 are disposed on the radially outer surface of the 1 st rotor core portion 22 over substantially the entire length of the 1 st rotor core portion 22 in the axial direction. The magnets 25 are provided on the 1 st magnet attachment surfaces 22a of the 1 st rotor core portion 22, respectively. The magnet 25 contacts the 1 st magnet attachment surface 22a from the radially outer side. In the present embodiment, the circumferential length of the magnet 25 is substantially the same as the circumferential length of the 1 st magnet attachment surface 22 a.

The magnets 25 are disposed on the radially outer surface of the 2 nd rotor core portion 23 over substantially the entire length of the 2 nd rotor core portion 23 in the axial direction. The magnets 25 are provided on the 2 nd magnet mounting surfaces 23a of the 2 nd rotor core portion 23, respectively. The magnet 25 contacts the 2 nd magnet mounting surface 23a from the radially outer side. In the present embodiment, the circumferential length of the magnet 25 is substantially the same as the circumferential length of the 2 nd magnet attachment surface 23 a. The magnet 25 disposed on the 1 st magnet attachment surface 22a of the 1 st rotor core portion 22 and the magnet 25 disposed on the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23 are common members. In the present embodiment, the plurality of magnets 25 provided on the rotor core 27 have the same shape.

The magnet 25 has a plate shape. The plate surface of the magnet 25 faces the radial direction. The magnet 25 has a quadrangular shape when viewed in the radial direction. In the example of the present embodiment, the length of the magnet 25 in the axial direction is larger than the length of the magnet 25 in the circumferential direction. That is, the magnet 25 has a rectangular shape when viewed in the radial direction and extends in the axial direction. In a cross section perpendicular to the center axis J, the circumferential length of the magnet 25 is larger than the radial length of the magnet 25. The radial thickness of the magnet 25 increases from both ends in the circumferential direction of the magnet 25 toward the center in the circumferential direction (inward in the circumferential direction).

In a cross section perpendicular to the center axis J, the radially inner surface 25b of the magnet 25 is linear. The radially inner surface 25b of the magnet 25 is a flat surface extending in a direction perpendicular to the radial direction. The radially inner surface 25b of the magnet 25 is rectangular when viewed from the radially inner side. The radially inner surface 25b of the magnet 25 contacts the 1 st magnet attachment surface 22 a. The radially inner surface 25b of the magnet 25 contacts the 2 nd magnet attachment surface 23 a.

In the cross section, the radially outer side surface 25a of the magnet 25 is convexly curved. The radially outer surface 25a of the magnet 25 is a curved surface that protrudes radially outward in cross section. Denoted by reference sign VC in fig. 4 to 6 is an imaginary circle passing through at least a part of the radially outer side surface 25a of the magnet 25 in cross section and centered on the central axis J. In cross section, the radially outer side surface 25a of the magnet 25 extends substantially along an imaginary circle VC. In the example of the present embodiment, in the cross section, the radius of curvature of the radially outer surface 25a of the magnet 25 is smaller than the radius of the imaginary circle VC. In the cross section, the circumferential center of the radially outer surface 25a of the magnet 25 is located on the imaginary circle VC, and the radially outer surface 25a of the magnet 25 is spaced radially inward from the imaginary circle VC as it goes from the circumferential center to both sides (one side and the other side in the circumferential direction) in the circumferential direction. That is, the radially outer surface 25a of the magnet 25 is positioned radially inward from the circumferential center portion toward both circumferential sides. In the present embodiment, the radially outermost portion of the radially outer surface 25a of the magnet 25 is the circumferential center, and the circumferential center is the apex (top). The radially outer surface 25a of the magnet 25 is rectangular when viewed radially outward. The radially outer surface 25a of the magnet 25 radially faces teeth 31b of the stator 30, which will be described later. That is, the radially outer surface of the rotor 20 is radially opposed to the teeth 31 b.

The function (operational effect) of the groove 28 will be described. According to the present embodiment, the magnetic flux of the magnet 25 is locally weakened in the circumferential direction by the groove portion 28. That is, the magnetic flux at the portion of the magnet 25 overlapping the groove 28 is weaker than the portion of the magnet not overlapping the groove 28 when viewed in the radial direction. Therefore, the groove 28 can provide the same operational effect as that of changing the curvature of the radially outer surface 25a of the magnet 25 without changing the curvature of the radially outer surface 25a of the magnet 25. The action effect is an effect of reducing the torque ripple of the entire motor 10 by locally generating a waveform of torque ripple in opposite phase, for example. Further, vibration and noise generated from the motor 10 can be reduced. In other words, the groove 28 can simulate a curvature different from the curvature of the radially outer surface 25a of the magnet 25. That is, in the present embodiment, the groove portion 28 is provided at a position overlapping a portion where the curvature of the magnet 25 is desired to be changed when viewed in the radial direction, in the radial outer surface of the 1 st rotor core portion 22. According to the present embodiment, the provision of the groove 28 can suppress the curvature of the radially outer surface 25a of the magnet 25 to a small value. In other words, in the cross section, the radius of curvature of the radially outer surface 25a of the magnet 25 can be increased. This makes it possible to approximate the shape of the magnet 25 to a rectangular parallelepiped, and thus the material yield of the magnet 25 can be improved. Even if the specification of the motor 10 is various, the necessity of changing the curvature of the magnet 25 in accordance with the specification of the motor 10 can be suppressed. That is, the necessity of preparing the magnet(s) 25 having different shapes for each specification of the motor 10 is reduced. Further, the magnet 25 can be shared by components. Therefore, the manufacturing cost of the motor 10 can be reduced.

According to the present embodiment, since the groove 28 faces the magnet 25 from the radially inner side, it is easy to control the magnetic flux of the magnet 25 more stably. In the present embodiment, the groove portions 28 are disposed at both circumferential ends of the 1 st magnet attachment surface 22 a. That is, the groove portions 28 are arranged at positions overlapping both circumferential ends of the radially outer surface 25a of the magnet 25 when viewed in the radial direction. Specifically, the groove portions 28 are disposed one at each of positions on the 1 st magnet attachment surface 22a that overlap with both circumferential ends of the radially outer surface 25a of the magnet 25 when viewed in the radial direction. According to the present embodiment, the magnetic flux at the circumferential end of the magnet 25 can be weakened by the groove 28. Therefore, the curvature of the circumferential end of the magnet 25 can be suppressed to be small, and the same operational effect as in the case of increasing the curvature can be obtained. The shape of the magnet 25 can be made closer to a rectangular parallelepiped, and the material yield of the magnet 25 can be improved.

In the present embodiment, the above-described operational effects can be obtained by the groove portions 28, and the magnet 25 can be stably supported by the circumferential both ends 22e of the 1 st magnet attachment surface 22 a. That is, the magnet 25 is supported by the circumferential both ends 22e of the 1 st magnet mounting surface 22a, so that fixation is facilitated, and wobbling or tilting is suppressed.

The 1 st rotor core portion 22 has a groove portion 28 on a surface facing in the radial direction of the 1 st rotor core portion 22, and the 2 nd rotor core portion 23 does not have a groove portion 28 on a surface facing in the radial direction of the 2 nd rotor core portion 23. The groove 28 is disposed only on the 1 st magnet attachment surface 22a of the 1 st rotor core portion 22, and is not disposed on the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23. According to the present embodiment, the magnet 25 provided on the radially outer surface of the 1 st rotor core portion 22 and the magnet 25 provided on the radially outer surface of the 2 nd rotor core portion 23 are made common, and the curvature different from the actual curvature can be simulated in the magnet 25 of the 1 st rotor core portion 22. Thus, the waveform of the torque ripple generated in the 1 st region S1 and the waveform of the torque ripple generated in the 2 nd region S2 can be generated in mutually opposite phases, and the fluctuation width of the waveform of the composite torque ripple (the difference between the maximum value and the minimum value of the waveform of the composite torque ripple) can be suppressed to be small. Therefore, the manufacturing cost of the motor 10 can be suppressed, and the torque ripple can be reduced.

In the present embodiment, the circumferential position of the magnet 25 disposed on the 1 st magnet attachment surface 22a of the 1 st rotor core portion 22 and the circumferential position of the magnet 25 disposed on the 2 nd magnet attachment surface 23a of the 2 nd rotor core portion 23 are different from each other. That is, the circumferential position of the magnet 25 on the 1 st magnet attachment surface 22a and the circumferential position of the magnet 25 on the 2 nd magnet attachment surface 23a are shifted from each other. That is, the magnets 25 of each stage of the 1 st and 2 nd regions S1 and S2 are arranged to be circumferentially shifted from each other, and a step skew (step skew) is applied to the magnets 25. Accordingly, the waveforms of the respective cogging torques generated in the 1 st region S1 and the 2 nd region S2 can be generated in mutually opposite phases, and the fluctuation width of the waveform of the combined cogging torque (the difference between the maximum value and the minimum value of the waveform of the combined cogging torque) can be suppressed to be small. Therefore, the cogging torque can be reduced. Further, vibration and noise generated from the motor 10 can be reduced.

In a cross section perpendicular to the center axis J, the length of the groove portion 28 in the circumferential direction is greater than the length in the radial direction. According to the present embodiment, the rigidity of the radially outer end portion of the 1 st rotor core portion 22 can be ensured, and the magnitude of the magnetic flux of the magnet 25 can be easily controlled. According to the present embodiment, the above-described operational effects can be obtained by the groove portion 28 having a simple structure.

The magnet holder 26 is provided on the rotor core 27 and holds the magnet 25. In the present embodiment, the magnet holder 26 is provided on the radially outer surface of the rotor core 27. The magnet holder 26 has a portion extending in the axial direction between a pair of circumferentially adjacent magnets 25. A plurality of magnet holders 26 are provided on the rotor core 27. The magnet holders 26 are provided on the radially outer surface of the 1 st rotor core portion 22 and the radially outer surface of the 2 nd rotor core portion 23, respectively.

The magnet holder 26 is made of resin. The magnet holder 26 of the 1 st rotor core portion 22 is formed by arranging the 1 st rotor core portion 22 in the mold 100 shown in fig. 9, and causing the molten resin to flow from the plurality of gates 102 and solidify in the mold 100. The magnet holder 26 of the 2 nd rotor core portion 23 is formed by arranging the 2 nd rotor core portion 23 in the mold 100, and causing the molten resin to flow in from the plurality of gates 102 and solidify in the mold 100.

In fig. 9, the center axis of the mold 100 is denoted by reference numeral Jm. The 1 st rotor core portion 22 and the 2 nd rotor core portion 23 are respectively provided in the mold 100 in postures such that the central axes J thereof coincide with the central axis Jm of the mold 100. The 1 st rotor core portion 22 and the 2 nd rotor core portion 23 are disposed in the mold 100 in a state where the magnet 25 is not mounted on the radial outer side surface. The mold 100 has a plurality of magnet corresponding portions 101 arranged in the circumferential direction. The magnet corresponding portion 101 has a shape similar to the magnet 25. Each magnet corresponding portion 101 contacts each 1 st magnet mounting surface 22a of the 1 st rotor core portion 22. The magnet corresponding portion 101 contacts the 1 st magnet attachment surface 22a from the radially outer side. Each magnet corresponding portion 101 contacts each 2 nd magnet mounting surface 23a of the 2 nd rotor core portion 23. The magnet corresponding portion 101 contacts the 2 nd magnet mounting surface 23a from the radially outer side.

The magnet holder 26 provided on the 1 st rotor core portion 22 has an anchor portion 26a, a radial pressing portion 26b, and an axial pressing portion 26 c. The magnet holder 26 provided on the 2 nd rotor core portion 23 has an anchor portion 26a and a radial pressing portion 26 b. In the present embodiment, since the 2 nd rotor core portion 23 is disposed so as to be sandwiched between the two 1 st rotor core portions 22 in the axial direction, the 2 nd rotor core portion 23 does not have the axial pressing portion 26 c. However, the present invention is not limited to this, and for example, in the case where the 1 st rotor core portion 22 and the 2 nd rotor core portion 23 are each provided with one, the 2 nd rotor core portion 23 may have the axial pressing portion 26 c. The anchoring portion 26a, the radial pressing portion 26b and the axial pressing portion 26c are portions of a single member.

The anchor portion 26a is formed by filling molten resin between the holder mounting grooves 22c, 23c and the pair of circumferentially adjacent magnet corresponding portions 101 and solidifying the resin. The anchor portion 26a is fitted in the holder mounting grooves 22c, 23 c. The anchor portion 26a extends in the axial direction. The plurality of anchor portions 26a are provided at intervals in the circumferential direction. The anchor portion 26a has a portion whose circumferential width increases toward the radially inner side. The circumferential width of the radially inner end portion of the anchor portion 26a increases toward the radially inner side. The circumferential width of the portion other than the radially inner end of the anchor portion 26a increases toward the radially outer side.

The radial pressing portion 26b is connected to the anchor portion 26a in the circumferential direction. The radial pressing portion 26b is disposed at the end portion on the radially outer side of the magnet holder 26. The radial pressing portion 26b extends in the axial direction. The plurality of radial pressing portions 26b are provided at intervals in the circumferential direction. The radial pressing portions 26b protrude toward both sides in the circumferential direction (one side in the circumferential direction and the other side in the circumferential direction) with respect to the anchor portions 26 a. The radial pressing portion 26b is a plate whose plate surface faces in the radial direction. The radial pressing portion 26b is disposed at a distance from the 1 st magnet attachment surface 22a on the radially outer side of the 1 st magnet attachment surface 22 a. The radial pressing portion 26b and the 1 st magnet attachment surface 22a are arranged to overlap when viewed in the radial direction. The radial pressing portion 26b is disposed at a distance from the 2 nd magnet attachment surface 23a on the radially outer side of the 2 nd magnet attachment surface 23 a. The radial pressing portion 26b and the 2 nd magnet attachment surface 23a are arranged to overlap when viewed in the radial direction.

The radial pressing portion 26b contacts the magnet 25 in the radial direction. In the present embodiment, the radial pressing portion 26b contacts the magnet 25 from the radially outer side. That is, the radially inward plate surface of the radial pressing portion 26b contacts the radially outer surface 25a of the magnet 25. The radially inward facing plate surface of the radial pressing portion 26b contacts at least a circumferential end of the radially outer surface 25a of the magnet 25. The magnet 25 is disposed between the 1 st magnet attachment surface 22a and the radial pressing portion 26b by, for example, press-fitting in the axial direction. The magnet 25 is disposed between the 2 nd magnet attachment surface 23a and the radial pressing portion 26b by, for example, press-fitting in the axial direction.

According to the present embodiment, the magnet 25 can be pressed in the radial direction by the magnet holder 26, and the movement of the magnet 25 in the radial direction can be suppressed. As in the present embodiment, when both circumferential ends 22e of the 1 st magnet attachment surface 22a and both circumferential ends of the 2 nd magnet attachment surface 23a are in contact with both circumferential ends of the radially inner surface 25b of the magnet 25 from the radially inner side, the retainer mounting grooves 22c, 23c are more preferably formed in a wedge shape in a small circumferential space. That is, the gap between the 1 st magnet attachment surfaces 22a adjacent in the circumferential direction can be kept small, and the wedge-shaped holder attachment groove 22c and the anchor portion 26a can be easily arranged in the gap. It is easy to suppress the gap between the 2 nd magnet attachment surfaces 23a adjacent in the circumferential direction to be small, and the wedge-shaped holder attachment groove 23c and the anchor portion 26a are arranged in the gap.

The axial pressing portion 26c is axially connected to the anchor portion 26a and the radial pressing portion 26 b. The axial pressing portion 26c is annular with the center axis J as the center. In the present embodiment, the axial pressing portion 26c has an annular plate shape. The axial pressing portion 26c is disposed only at one of both axial ends of the 1 st rotor core portion 22. The axial pressing portion 26c axially contacts the magnet 25. According to the present embodiment, the magnet 25 can be pressed in the axial direction by the magnet holder 26, and the movement of the magnet 25 in the axial direction can be suppressed.

A plurality of electromagnetic steel sheets constituting the rotor core 27 will be explained. The 1 st rotor core portion 22 has a 1 st electromagnetic steel plate 41 and a 2 nd electromagnetic steel plate 42. The 2 nd rotor iron core portion 23 has the 3 rd electromagnetic steel sheet 43. That is, the plurality of magnetic steel sheets of the rotor core 27 include the 1 st magnetic steel sheet 41, the 2 nd magnetic steel sheet 42, and the 3 rd magnetic steel sheet 43.

A plurality of 1 st electromagnetic steel plates 41 are provided in the rotor core 27. A plurality of 1 st electromagnetic steel plates 41 are provided in the 1 st rotor core portion 22. Each 1 st electromagnetic steel sheet 41 constitutes a part of the 1 st rotor core portion 22 in the axial direction. The plurality of 1 st magnetic steel sheets 41 are stacked in the axial direction at portions other than the end portions of the 1 st rotor core portion 22 in the axial direction. In the present embodiment, the plurality of 1 st magnetic steel sheets 41 are arranged in a portion other than one of both ends of the 1 st rotor core portion 22 in the axial direction. The 1 st electromagnetic steel sheet 41 has a substantially polygonal plate shape. In a plan view taken along the axial direction, the outer shape of the 1 st magnetic steel sheet 41 is a substantially polygonal shape. In the example of the present embodiment, the outer shape of the 1 st electrical steel sheet 41 is substantially octagonal in a plan view.

The 1 st electromagnetic steel plate 41 has a shaft hole portion 41a, a 1 st magnet attachment portion 41b, a through hole portion 41c, a holder attachment groove portion 41d, and a recess portion 41 e. The shaft hole 41a is disposed in the center of the 1 st electromagnetic steel sheet 41 as viewed in the axial direction. The shaft hole 41a is disposed coaxially with the central axis J in the 1 st electromagnetic steel sheet 41. The shaft hole 41a penetrates the 1 st electromagnetic steel sheet 41 in the axial direction. The shaft hole portion 41a has a circular shape in a plan view viewed in the axial direction. The shaft hole 41a constitutes a part of the shaft hole 27a in the axial direction.

The 1 st magnet mounting portion 41b is disposed on a surface of the 1 st electromagnetic steel sheet 41 facing in the radial direction. In the present embodiment, the 1 st magnet attachment portion 41b is disposed on the radially outward surface of the 1 st electromagnetic steel sheet 41. A plurality of 1 st magnet attachment portions 41b are arranged in a circumferential direction on the radially outer surface of the 1 st electromagnetic steel sheet 41. In the example of the present embodiment, the 1 st magnetic steel sheet 41 has eight 1 st magnet attachment portions 41b arranged in the circumferential direction on the radially outer surface of the 1 st magnetic steel sheet 41. The 1 st magnet mounting portions 41b are in contact with the radially inner surface 25b of the magnet 25. That is, the surface of the 1 st electromagnetic steel sheet 41 facing the radial direction contacts the surface of the magnet 25 facing the radial direction. In the present embodiment, the 1 st magnet attachment portion 41b is a flat surface extending in a direction perpendicular to the radial direction. That is, the 1 st magnet mounting portion 41b is perpendicular to the radial direction. In a plan view taken along the axial direction, the 1 st magnet mounting portion 41b is a straight line extending in a direction perpendicular to the radial direction. The 1 st magnet mounting portion 41b constitutes a part of the 1 st magnet mounting surface 22a in the axial direction.

The through hole 41c penetrates the 1 st electromagnetic steel sheet 41 in the axial direction. The plurality of through holes 41c are arranged in the 1 st electromagnetic steel sheet 41 at intervals in the circumferential direction. In the example of the present embodiment, eight through holes 41c are arranged at equal intervals in the circumferential direction in the 1 st electromagnetic steel sheet 41. The through hole 41c is disposed in a portion other than the outer end portion in the radial direction of the 1 st electromagnetic steel sheet 41. The through hole 41c has a circular shape in a plan view as viewed in the axial direction. The through hole 41c constitutes a part of the through hole 22b in the axial direction.

The cage attachment groove portion 41d is a concave shape recessed radially inward from the radially outer surface of the 1 st electromagnetic steel sheet 41. The holder mounting groove portion 41d is disposed between a pair of circumferentially adjacent 1 st magnet mounting portions 41b on the radially outer surface of the 1 st electromagnetic steel sheet 41, and opens radially outward. The plurality of cage attachment groove portions 41d are arranged on the radially outer surface of the 1 st electromagnetic steel sheet 41 at intervals in the circumferential direction. In the example of the present embodiment, eight cage attachment groove portions 41d are arranged at equal intervals in the circumferential direction on the radial outer surface of the 1 st electromagnetic steel sheet 41.

The cage attachment groove portion 41d has a groove width that decreases radially outward. That is, the circumferential width dimension of the cage attachment groove portion 41d decreases toward the radially outer side. An opening portion located at the radial outer end portion of the holder attachment groove portion 41d opens between the circumferential end portions of the pair of first magnet attachment portions 41b adjacent in the circumferential direction. The holder mounting groove portion 41d constitutes a part of the holder mounting groove 22c in the axial direction.

The recess 41e is disposed on a surface of the electromagnetic steel sheet facing the radial direction. The concave portion 41e is a concave shape recessed in the radial direction from the surface of the 1 st electromagnetic steel sheet 41 facing in the radial direction. In the present embodiment, the recess 41e is recessed radially inward from the radially outward surface of the 1 st electromagnetic steel sheet 41, and is open radially outward. The recess 41e is disposed on the radial outer surface of the 1 st electromagnetic steel sheet 41. A plurality of recesses 41e are arranged on the radially outer surface of the 1 st electromagnetic steel sheet 41 at intervals in the circumferential direction.

The recess 41e is disposed radially inward of the magnet 25 on the radially outer surface of the 1 st electromagnetic steel sheet 41. The recess 41e is disposed in the 1 st magnet mounting portion 41 b. The plurality of recesses 41e are provided in the 1 st magnet mounting portion 41b at intervals in the circumferential direction. The recesses 41e are disposed at both circumferential ends of the 1 st magnet mounting portion 41 b. In the example of the present embodiment, the recesses 41e are disposed one at each of both ends in the circumferential direction of the 1 st magnet mounting portion 41 b.

The recess 41e is disposed on the circumferential inner side of both ends of the 1 st magnet mounting portion 41b in the circumferential direction. That is, the recess 41e is disposed on the circumferential center side of the 1 st magnet mounting portion 41b with respect to both circumferential ends of the 1 st magnet mounting portion 41 b. Both circumferential ends of the 1 st magnet mounting portion 41b are in contact with both circumferential ends of the radially inner surface 25b of the magnet 25. Both circumferential ends of the 1 st magnet mounting portion 41b are in contact with both circumferential ends of the radially inner surface 25b of the magnet 25 from the radially inner side.

In the example of the present embodiment, the recess 41e has a substantially quadrangular shape in a plan view seen in the axial direction. The inner surface of the recess 41e has an inner surface portion facing in the radial direction and an inner surface portion facing in the circumferential direction. The length of the recess 41e in the circumferential direction is larger than the length of the recess 41e in the radial direction. In the present embodiment, the length of the recess 41e in the radial direction is constant along the direction in which the 1 st magnet mounting portion 41b extends in a plan view. That is, in a plan view, the 1 st magnet attachment portion 41b linearly extends in a direction perpendicular to the radial direction, and the radial dimension (depth) of the recess 41e is constant along the extending direction of the 1 st magnet attachment portion 41 b. The recess 41e constitutes a part of the groove 28 in the axial direction.

At least one 2 nd electromagnetic steel sheet 42 is provided in the rotor core 27. In the present embodiment, a plurality of 2 nd electromagnetic steel plates 42 are provided in the rotor core 27. At least one 2 nd electromagnetic steel sheet 42 is provided in the 1 st rotor core portion 22. In the present embodiment, a plurality of 2 nd electromagnetic steel plates 42 are provided in the 1 st rotor core portion 22. The 2 nd electromagnetic steel sheet 42 constitutes a part of the 1 st rotor core portion 22 in the axial direction. The 2 nd electromagnetic steel plate 42 is disposed at an end portion in the axial direction of the 1 st rotor core portion 22. In the present embodiment, the 2 nd electromagnetic steel sheet 42 is disposed only at one of both ends of the 1 st rotor core portion 22 in the axial direction. The 2 nd electromagnetic steel sheet 42 has a substantially polygonal plate shape. In a plan view in the axial direction, the outer shape of the 2 nd electromagnetic steel sheet 42 is a substantially polygonal shape. In the example of the present embodiment, the outer shape of the 2 nd electrical steel sheet 42 is substantially octagonal in a plan view.

The 2 nd electromagnetic steel plate 42 has a shaft hole 42a, a 1 st magnet mounting portion 42b, a through hole 42c, a holder mounting groove portion 42d, and a closing portion 42 e. The shaft hole 42a, the through hole 42c, and the holder attachment groove 42d of the 2 nd electromagnetic steel sheet 42 have substantially the same configurations as the shaft hole 41a, the through hole 41c, and the holder attachment groove 41d of the 1 st electromagnetic steel sheet 41, respectively, and therefore, detailed description thereof is omitted.

The 1 st magnet mounting portion 42b is disposed on a surface of the 2 nd electromagnetic steel sheet 42 facing in the radial direction. In the present embodiment, the 1 st magnet mounting portion 42b is disposed on the radially outward surface of the 2 nd electromagnetic steel sheet 42. A plurality of 1 st magnet attachment portions 42b are arranged in a circumferential direction on an outer surface of the 2 nd electromagnetic steel sheet 42 in the radial direction. In the example of the present embodiment, the 2 nd electromagnetic steel plate 42 has eight 1 st magnet mounting portions 42b arranged in the circumferential direction on the radially outer side surface of the 2 nd electromagnetic steel plate 42. The 1 st magnet mounting portions 42b are in contact with the radially inner surface 25b of the magnet 25. That is, the surface of the 2 nd electromagnetic steel sheet 42 facing the radial direction contacts the surface of the magnet 25 facing the radial direction. According to the present embodiment, since both the 1 st magnetic steel sheet 41 and the 2 nd magnetic steel sheet 42 are in contact with the magnet 25 in the radial direction, a decrease in the magnetic force of the magnet 25 can be suppressed, and generation of magnetic loss can be suppressed. In the present embodiment, the 1 st magnet attachment portion 42b is a flat surface extending in a direction perpendicular to the radial direction. That is, the 1 st magnet mounting portion 42b is perpendicular to the radial direction. In a plan view taken along the axial direction, the 1 st magnet mounting portion 42b is a straight line extending in a direction perpendicular to the radial direction. The 1 st magnet mounting portion 42b constitutes a part of the 1 st magnet mounting surface 22a in the axial direction.

The 1 st magnet attachment portion 42b of the 2 nd electromagnetic steel sheet 42 is different from the 1 st magnet attachment portion 41b of the 1 st electromagnetic steel sheet 41 in the configuration in that a closed portion 42e is disposed instead of the recess portion 41 e. That is, the recess 41e is not disposed in the 1 st magnet mounting portion 42 b. The 2 nd electromagnetic steel sheet 42 does not have the recess 41 e.

The closing portion 42e is disposed at an end in the radial direction of the electromagnetic steel sheet. In the present embodiment, the closing portion 42e is disposed at the end portion on the radially outer side of the 2 nd electromagnetic steel sheet 42. The plurality of closing portions 42e are arranged at intervals in the circumferential direction at the radial outer end portions of the 2 nd electromagnetic steel sheet 42. The closing portion 42e is constituted by a part of the 1 st magnet mounting portion 42b in the circumferential direction and a part of the radially outer end portion of the 2 nd electromagnetic steel sheet 42 located on the radially inner side (adjacent thereto). The plurality of closing portions 42e are provided at intervals in the circumferential direction in a range overlapping with one of the 1 st magnet attachment portions 42b when viewed in the radial direction. The closing portions 42e are disposed at positions overlapping with both circumferential ends of the 1 st magnet mounting portion 42b when viewed in the radial direction. In the example of the present embodiment, the closing portions 42e are disposed at positions overlapping both ends in the circumferential direction of the 1 st magnet mounting portion 42b when viewed in the radial direction.

The closing portion 42e is disposed inward in the circumferential direction from both circumferential ends of the 1 st magnet mounting portion 42b when viewed in the radial direction. That is, the closing portion 42e is disposed closer to the center portion side in the circumferential direction of the 1 st magnet mounting portion 42b than both ends in the circumferential direction of the 1 st magnet mounting portion 42b as viewed in the radial direction. The closing portion 42e overlaps the recess 41e to cover the recess 41e when viewed in the axial direction. The closing portion 42e has substantially the same shape as the recess 41e as viewed in the axial direction. In the present embodiment, the closing portion 42e has a substantially rectangular shape when viewed in the axial direction.

According to the present embodiment, the recess 41e of the 1 st magnetic steel sheet 41 is axially closed by the closing portion 42e of the 2 nd magnetic steel sheet 42. That is, the groove portion 28 of the 1 st rotor core portion 22 is axially closed at an axial end of the 1 st rotor core portion 22. Therefore, when the 1 st rotor core portion 22 is disposed in the mold 100 and the magnet holder 26 is insert-molded on the 1 st rotor core portion 22 in manufacturing the motor 10, the blocking portion 42e can suppress the molten resin from flowing into the groove portion 28. Specifically, when the magnet holder 26 is resin-molded, the magnet corresponding portion 101 of the mold 100 is in contact with the 1 st magnet attachment surface 22a, which is the surface of the 1 st rotor core portion 22 facing the radial direction, instead of the magnet 25. The blocking portion 42e of the 2 nd electromagnetic steel sheet 42 can suppress the molten resin from flowing into the groove portion 28 in the axial direction between the magnet corresponding portion 101 and the 1 st magnet attachment surface 22 a. By suppressing the inflow of the resin into the groove portion 28, the 1 st magnet mounting surface 22a and the magnet 25 are stably adhered to each other at the time of assembling the rotor 20 in the subsequent step of resin molding. That is, the rotor core 27 is stably in contact with the magnet 25.

Specifically, unlike the present embodiment, when the resin flows into the groove 28 during resin molding without providing the closing portion 42e, the resin solidified in the groove 28 protrudes radially outward from the 1 st magnet attachment surface 22 a. In this case, in the subsequent step, when the magnet 25 is mounted on the 1 st magnet mounting surface 22a, a gap in the radial direction is generated between the 1 st magnet mounting surface 22a and the magnet 25. That is, the magnet 25 is not closely attached to the 1 st magnet attachment surface 22a due to the resin, and the magnet 25 is disposed in a state of being partially floated in the radial direction from the 1 st magnet attachment surface 22a, and the magnetic force of the magnet 25 may be reduced. On the other hand, according to the present embodiment, since the magnet 25 is suppressed from being lifted in the radial direction from the 1 st magnet attachment surface 22a and the 1 st magnet attachment surface 22a is stably in contact with the magnet 25, it is possible to suppress a decrease in the magnetic force of the magnet 25 and suppress the occurrence of magnetic loss.

In the present embodiment, the 2 nd electromagnetic steel sheet 42 is disposed only at one of both ends of the 1 st rotor core portion 22 in the axial direction. According to the present embodiment, the number of the 2 nd magnetic steel sheets 42 having a weight larger than that of the 1 st magnetic steel sheet 41 can be suppressed to be small, and the 1 st rotor core portion 22 can be reduced in weight. In the present embodiment, it is preferable that a pin portion (not shown) protruding radially inward from the corresponding magnet portion 101 is provided in the corresponding magnet portion 101 of the mold 100. The pin portion is disposed so as to be axially insertable into the groove portion 28 of the 1 st rotor core portion 22. In this case, when the 1 st rotor core portion 22 is provided in the mold 100, an error in the axial direction of the 1 st rotor core portion 22 (error in the vertical direction) can be suppressed by the pin portion.

As shown in fig. 7, in the present embodiment, a plurality of 2 nd electromagnetic steel plates 42 are stacked and provided in the axial direction at the end portion in the axial direction of the 1 st rotor core portion 22. In the illustrated example, two 2 nd electromagnetic steel plates 42 are provided at the end of the 1 st rotor core portion 22 so as to overlap each other in the axial direction. However, the 2 nd magnetic steel sheets 42 may be provided at least three axially overlapping each other at the axial end of the 1 st rotor core portion 22.

According to the present embodiment, the axial distance between the end surface 101a of the corresponding magnet portion 101 of the mold 100 facing the axial direction and the end portion of the groove portion 28 in the axial direction can be secured to be large. That is, the length of the magnet corresponding portion 101 protruding in the axial direction with respect to the groove portion 28 can be ensured to be large. It is possible to further suppress the molten resin from entering the groove portion 28 from around the end surface 101a of the magnet corresponding portion 101 when the magnet holder 26 is resin-molded. Specifically, by laminating a plurality of 2 nd magnetic steel sheets 42 on the end portion in the axial direction of the 1 st rotor core portion 22, even when, for example, design tolerances or manufacturing errors occur, the axial distance between the end surface 101a of the corresponding magnet portion 101 facing the axial direction and the end portion in the axial direction of the groove portion 28, that is, the amount of protrusion of the corresponding magnet portion 101 is suppressed to zero or a negative value, and the inflow of the molten resin into the groove portion 28 can be stably suppressed. Further, for example, even when the thickness (plate thickness) of the 2 nd electrical steel plate 42 is small, the resin is easily prevented from flowing into the groove portion 28.

In the present embodiment, the 2 nd electrical steel sheet 42 is disposed between the axial pressing portion 26c of the magnet holder 26 and the 1 st electrical steel sheet 41 in the axial direction. That is, the closing portion 42e is disposed between the axial pressing portion 26c and the recess 41e (groove portion 28) in the axial direction. Therefore, the blocking portion 42e of the 2 nd electromagnetic steel sheet 42 can stably prevent the resin melted at the time of resin molding the magnet holder 26 from flowing into the groove portion 28 from the annular chamber 103 (see fig. 9) in the mold 100 for molding the axial pressing portion 26 c.

As shown in fig. 3, in the present embodiment, the 2 nd magnetic steel plates 42 are disposed at both axial end portions of the rotor core 27. That is, the 2 nd electromagnetic steel plates 42 are disposed only at both ends of the rotor core 27 in the axial direction as a whole of the rotor core 27. Specifically, each of the 2 nd electromagnetic steel plates 42 of the pair of 1 st rotor iron cores 22 is disposed only at one end portion axially distant from the 2 nd rotor iron core 23, of both end portions in the axial direction of the 1 st rotor iron core 22. Therefore, interference between the 2 nd electromagnetic steel plate 42 of the 1 st rotor core portion 22 and the magnetic properties of the magnets 25 arranged in the 2 nd rotor core portion 23 can be suppressed.

A plurality of 3 rd electromagnetic steel plates 43 are provided in the rotor core 27. A plurality of 3 rd electromagnetic steel plates 43 are provided in the 2 nd rotor core portion 23. Each 3 rd electromagnetic steel plate 43 constitutes a part of the 2 nd rotor core portion 23 in the axial direction. A plurality of the 3 rd electromagnetic steel sheets 43 are stacked in the axial direction over the entire area in the axial direction of the 2 nd rotor core portion 23. The 3 rd electromagnetic steel sheet 43 has a substantially polygonal plate shape. In a plan view in the axial direction, the outer shape of the 3 rd electromagnetic steel sheet 43 is substantially polygonal. In the example of the present embodiment, the outer shape of the 3 rd electrical steel sheet 43 is substantially octagonal in plan view.

The 3 rd electromagnetic steel plate 43 has a shaft hole portion 43a, a 2 nd magnet mounting portion 43b, a through hole portion 43c, and a holder mounting groove portion 43 d. The shaft hole portion 43a, the through hole portion 43c, and the holder attachment groove portion 43d of the 3 rd electromagnetic steel sheet 43 have substantially the same configurations as the shaft hole portion 42a, the through hole portion 42c, and the holder attachment groove portion 42d of the 2 nd electromagnetic steel sheet 42, respectively, and therefore, detailed description thereof is omitted.

The 2 nd magnet mounting portion 43b is disposed on a surface of the 3 rd electromagnetic steel sheet 43 facing in the radial direction. In the present embodiment, the 2 nd magnet mounting portion 43b is disposed on the radially outward surface of the 3 rd electromagnetic steel sheet 43. A plurality of the 2 nd magnet mounting portions 43b are arranged in a circumferential direction on the radially outer surface of the 3 rd electromagnetic steel sheet 43. In the example of the present embodiment, the 3 rd electromagnetic steel plate 43 has eight 2 nd magnet mounting portions 43b arranged in the circumferential direction on the radially outer side surface of the 3 rd electromagnetic steel plate 43. The 2 nd magnet mounting portions 43b are in contact with the radially inner surface 25b of the magnet 25. That is, the radially facing surface of the 3 rd electromagnetic steel sheet 43 contacts the radially facing surface of the magnet 25. In the present embodiment, the 2 nd magnet mounting portion 43b is a flat surface extending in a direction perpendicular to the radial direction. That is, the 2 nd magnet mounting portion 43b is perpendicular to the radial direction. In a plan view taken along the axial direction, the 2 nd magnet mounting portion 43b is a straight line extending in a direction perpendicular to the radial direction. The 2 nd magnet mounting portion 43b constitutes a part of the 2 nd magnet mounting surface 23a in the axial direction. Since the groove 28 is not disposed in the 2 nd magnet attachment surface 23a, the recess 41e is not disposed in the 2 nd magnet attachment portion 43 b. The 3 rd electromagnetic steel sheet 43 and the 2 nd electromagnetic steel sheet 42 may be a common member. In this case, the types of components constituting the rotor core 27 can be suppressed to be small.

As shown in fig. 1, the stator 30 is radially opposed to the rotor 20. In the present embodiment, the stator 30 is disposed radially outward of the rotor 20, and faces the rotor 20 with a gap therebetween in the radial direction. The stator 30 has a stator core 31, an insulator 30Z, and a plurality of coils 30C.

The stator core 31 is annular with the center axis J as the center. The stator core 31 surrounds the rotor 20 at the radially outer side of the rotor 20. The stator core 31 is disposed radially outward of the rotor 20, and faces the rotor 20 with a gap therebetween in the radial direction. The stator core 31 is, for example, a steel sheet laminate formed by laminating a plurality of electromagnetic steel sheets in the axial direction.

The stator core 31 has a core back 31a and a plurality of teeth 31 b. That is, the stator 30 has a core back 31a and a plurality of teeth 31 b. The core back 31a is annular with the center axis as the center. The radially outer side surface of the core back 31a is directly or indirectly fixed to the inner peripheral surface of the peripheral wall 11a of the housing 11. The teeth 31b extend radially inward from the radially inner surface 31c of the core back 31 a. The plurality of teeth 31b are circumferentially arranged on the radially inner surface 31c of the core back 31a at intervals. In the present embodiment, the plurality of teeth 31b are arranged at equal intervals in the circumferential direction. The teeth 31b are radially opposed to the magnets 25. That is, the radially inner side surfaces of the teeth 31b face the radially outer side surface 25a of the magnet 25 of the 1 st rotor core portion 22 and the radially outer side surface 25a of the magnet 25 of the 2 nd rotor core portion 23 with a gap from the radially outer side.

The insulator 30Z is mounted on the stator core 31. The insulating member 30Z has a portion covering the plurality of teeth 31 b. The material of the insulating member 30Z is, for example, an insulating material such as resin.

The coil 30C is mounted on the stator core 31. The plurality of coils 30C are attached to the stator core 31 via the insulator 30Z. The plurality of coils 30C are formed by winding a conductive wire around each tooth 31b with an insulator 30Z interposed therebetween.

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 total number of the 1 st region S1 and the 2 nd region S2 in the rotor core 27 is three in number, and the total number of the 1 st rotor core portion 22 and the 2 nd rotor core portion 23 in the axial direction is three in number alternately arranged. The same number of the 1 st sections S1 and the same number of the 2 nd sections S2 may be alternately arranged in the axial direction in the rotor core 27. In this case, the 1 st rotor core portion 22 and the 2 nd rotor core portion 23 are arranged in the same number, respectively, so as to be alternately arranged in the axial direction. That is, the sum of the number of the 1 st rotor core portions 22 and the number of the 2 nd rotor core portions 23 is an even number, and the 1 st rotor core portions 22 and the 2 nd rotor core portions 23 are alternately arranged in the axial direction. This makes it easy to more stably obtain the above-described operational effect of reducing torque ripple. In addition, one of the 1 st rotor core portion 22 and one of the 2 nd rotor core portions 23 may be arranged in the axial direction. In this case, the above-described operational effects can be obtained by a simpler configuration.

In addition, only the 1 st region S1 may be disposed in the rotor core 27, and the 2 nd region S2 may not be disposed. That is, in this case, the rotor core 27 is entirely constituted by one or more 1 st rotor core portions 22.

In the above embodiment, the plurality of magnets 25 adjacent in the axial direction are subjected to the stepped skew, but the stepped skew may not be applied unless the cogging torque is required to be reduced. That is, in this case, the circumferential center portion of the magnet 25 of the 1 st rotor core portion 22 and the circumferential center portion of the magnet 25 of the 2 nd rotor core portion 23 are arranged so as to overlap each other when viewed in the axial direction. Further, the circumferential center portions of the magnets 25 of the plural 1 st rotor core portions 22 are arranged to overlap each other when viewed in the axial direction.

In the above embodiment, the example in which the curvature radius of the radially outer surface 25a of the magnet 25 is smaller than the radius of the imaginary circle VC in the cross section perpendicular to the center axis J has been described, but the present invention is not limited thereto. In a cross section perpendicular to the center axis J, the radially outer surface 25a of the magnet 25 may be located on the imaginary circle VC over the entire circumferential region of the radially outer surface 25 a. That is, in the cross section, the radius of curvature of the radially outer surface 25a of the magnet 25 and the radius of the imaginary circle VC may be the same as each other. In this case, the magnet 25 can be made closer to a rectangular parallelepiped, and the material yield of the magnet 25 can be further improved.

In the above embodiment, the groove portions 28 are disposed at both circumferential end portions of the first 1 st magnet attachment surface 22a, respectively, but the present invention is not limited thereto. Only one groove 28 may be disposed on one 1 st magnet attachment surface 22 a. Further, three or more grooves 28 may be provided on the single 1 st magnet attachment surface 22a at intervals in the circumferential direction. In any case, the closing portions 42e of the 2 nd magnetic steel sheet 42 are provided with the same number as the number of the groove portions 28 on one 1 st magnet attachment surface 22a, and cover the recess portions 41e of the 1 st magnetic steel sheet 41 in the axial direction, that is, close the groove portions 28 in the axial direction.

In the above embodiment, the length (depth) of the groove portion 28 in the radial direction is constant along the direction in which the 1 st magnet attachment surface 22a extends in the cross section perpendicular to the center axis J, but the present invention is not limited thereto. In a cross section perpendicular to the center axis J, the length of the groove portion 28 in the radial direction may be increased toward the outer side in the circumferential direction of the 1 st magnet attachment surface 22 a. In addition, in the cross section, the length of the groove portion 28 in the radial direction may be reduced toward the outer side in the circumferential direction of the 1 st magnet attachment surface 22 a. In any case, the closing portion 42e of the 2 nd electromagnetic steel sheet 42 has substantially the same shape as the groove portion 28 when viewed in the axial direction, and closes the groove portion 28 in the axial direction.

In the above embodiment, the cross-sectional shape and position of the groove portion 28 are constant in the axial direction, but the present invention is not limited thereto. The groove 28 may have a cross-sectional shape and a cross-sectional position perpendicular to the central axis J different from each other in each axial portion. In this case, the same operational effects as those of the structure in which the curvature of the radially outer surface 25a of the magnet 25 changes in each portion in the axial direction can be obtained. Therefore, it is easy to meet the requirements of various motor specifications. The closing portion 42e of the 2 nd magnetic steel sheet 42 axially covers the recess 41e of the 1 st magnetic steel sheet 41 that is in contact with the 2 nd magnetic steel sheet 42 in the axial direction, thereby closing the groove portion 28 in the axial direction.

In the above embodiment, the 2 nd electromagnetic steel sheet 42 is disposed only at one of both ends of the 1 st rotor core portion 22 in the axial direction, but is not limited thereto. Fig. 10 shows a modification of the 1 st rotor core portion 22 of the above embodiment. In this modification, a plurality of 2 nd electromagnetic steel sheets 42 are provided. The 2 nd electromagnetic steel plates 42 are disposed at both axial end portions of the 1 st rotor core portion 22. In the illustrated example, one 2 nd magnetic steel sheet 42 is disposed at each of both axial end portions of the 1 st rotor core portion 22. The plurality of 1 st magnetic steel sheets 41 of the 1 st rotor core portion 22 are arranged between the pair of 2 nd magnetic steel sheets 42 in the axial direction. According to this modification, the 1 st rotor core portion 22 is less likely to generate axial imbalance. The unbalance means, for example, unbalance of magnetic force or weight. Further, when the 1 st rotor core portion 22 is provided in the mold 100, the magnet corresponding portion 101 of the mold 100 is prevented from contacting the corner (corner) of the opening of the recess 41e of the 1 st electromagnetic steel sheet 41, and the like, and local wear of the magnet corresponding portion 101 is prevented. In addition, when the 1 st rotor core portion 22 is provided in the mold 100, the limitation of the installation direction of the 1 st rotor core portion 22 in the axial direction can be eliminated, and the manufacturing becomes easy. Since no errors occur in the vertical installation direction of the 1 st rotor core portion 22, it is not necessary to provide the corresponding magnet portion 101 with a pin portion or the like for suppressing an error in the installation direction of the 1 st rotor core portion 22 in the axial direction, and the structure of the mold 100 can be simplified.

In the above embodiment, the inner rotor type motor 10 is described as an example, but the invention is not limited thereto. The present invention can also be applied to an outer rotor type motor. Although not particularly shown, in the outer rotor type motor, the rotor is disposed radially outward of the stator and rotates about the center axis of the rotor with respect to the stator.

In the above embodiment, the motor 10 is mounted on the electric power steering apparatus as an example, but is not limited thereto. The motor 10 can be used for various apparatuses such as a pump, a brake, a clutch, a cleaner, a dryer, a ceiling fan, a washing machine, and a refrigerator.

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

Claims (12)

1. A motor, comprising:

a rotor having a central axis; and

a stator radially opposed to the rotor,

the rotor has:

a rotor core having a plurality of electromagnetic steel plates stacked in an axial direction;

a magnet disposed on a surface of the rotor core facing in a radial direction; and

a resin magnet holder provided on the rotor core and holding the magnet,

the rotor core has a 1 st rotor core portion, the 1 st rotor core portion being disposed in a 1 st region in an axial direction,

the 1 st rotor core portion has a groove portion that is recessed in a radial direction from a radially-facing surface of the 1 st rotor core portion and extends in an axial direction,

the plurality of electromagnetic steel sheets have:

a 1 st electromagnetic steel sheet having a recess on a surface thereof facing a radial direction, the recess constituting a part of the groove in an axial direction; and

a 2 nd electromagnetic steel sheet having a closing portion that overlaps and covers the recess as viewed in an axial direction,

the 2 nd electromagnetic steel plate is disposed at an end in the axial direction of the 1 st rotor core portion.

2. The motor of claim 1,

the 1 st rotor core portion has a 1 st magnet attachment surface on which the magnets are disposed on a surface facing in a radial direction of the 1 st rotor core portion,

a plurality of the groove portions are provided on the 1 st magnet attachment surface at intervals in the circumferential direction,

the groove portions are respectively disposed at both circumferential end portions of the 1 st magnet attachment surface.

3. The motor according to claim 1 or 2,

a plurality of the 2 nd electromagnetic steel sheets are provided,

the 2 nd electromagnetic steel plates are disposed at both axial end portions of the 1 st rotor core portion.

4. The motor according to claim 1 or 2,

the 2 nd electromagnetic steel plate is disposed only at one of both end portions in the axial direction of the 1 st rotor core portion.

5. The motor according to claim 3 or 4,

a plurality of the 2 nd magnetic steel sheets are stacked in the axial direction at an end portion in the axial direction of the 1 st rotor core portion.

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

the magnet holder has:

a radial pressing portion that comes into contact with the magnet from a radial direction; and

an axial pressing portion that is brought into contact with the magnet from an axial direction,

the axial pressing portion is annular with the central axis as a center,

the 2 nd magnetic steel sheet is disposed between the axial pressing portion and the 1 st magnetic steel sheet in the axial direction.

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

a radially facing surface of the 1 st magnetic steel sheet and a radially facing surface of the 2 nd magnetic steel sheet are in contact with a radially facing surface of the magnet.

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

the rotor core has a 2 nd rotor core portion, the 2 nd rotor core portion being disposed in a 2 nd region different from the 1 st region in an axial direction,

the 2 nd rotor core portion has no groove portion on a surface facing the radial direction of the 2 nd rotor core portion.

9. The motor of claim 8,

the 1 st rotor core portion has a 1 st magnet attachment surface on which the magnets are disposed on a surface facing in a radial direction of the 1 st rotor core portion,

the 2 nd rotor core portion has a 2 nd magnet mounting surface on which the magnet is disposed on a surface of the 2 nd rotor core portion facing in the radial direction,

the circumferential position of the 1 st magnet mounting surface and the circumferential position of the 2 nd magnet mounting surface are offset from each other.

10. The motor according to claim 8 or 9,

the rotor core has:

two 1 st rotor core portions arranged at a distance from each other in the axial direction; and

one said 2 nd rotor iron core portion disposed axially between two said 1 st rotor iron core portions.

11. The motor of claim 10,

the rotor core is symmetrical in shape by rotating 180 ° around the 2 nd rotor core portion as a center when viewed in a radial direction.

12. The motor according to claim 10 or 11,

the 2 nd electromagnetic steel plates are disposed at both axial end portions of the rotor core.

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