Rotors, electric motors, and compressors

Abstract

The effective magnetic flux passing through the permanent magnet on one side of the magnetic pole section relative to the d-axis is made larger than the effective magnetic flux passing through the permanent magnet on the other side of the d-axis, and differences in the magnetization rate and demagnetization rate of the two permanent magnets arranged on both sides of the d-axis in the magnetic pole section are suppressed. [Solution] In a rotor, in a plane perpendicular to the centerline of rotation of the rotor core, when a line connecting the center of rotation of the rotor core to the center of the magnetic pole portions in the circumferential direction of the rotor core is defined as a d-axis, the permanent magnets provided in each magnetic pole portion include a first magnet arranged on one side of the circumferential direction of the rotor core with respect to the d-axis, and a second magnet arranged on the other side of the circumferential direction of the rotor core with respect to the d-axis. In the plane, when a first angle formed by the longitudinal direction of the first magnet and the d-axis on the outer periphery of the rotor core is defined as θ1 and a second angle formed by the longitudinal direction of the second magnet and the d-axis on the outer periphery of the rotor core is defined as θ2, the first magnet and second magnet satisfy θ1 = θ2 < 90 degrees and are arranged asymmetrically with respect to the d-axis.

Description

[Technical Field]

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

[0002] Known electric motors include an embedded magnet rotor in which permanent magnets are embedded inside a rotor core. This type of electric motor includes a rotor with multiple magnetic poles formed on the outer periphery of the permanent magnet and arranged along the circumferential direction, and a stator with multiple teeth arranged on the outer periphery of the rotor and an annular yoke connecting the multiple teeth.

[0003] One type of rotor has two permanent magnets arranged in a V-shape on either side of the d-axis of the magnetic pole portion in a plane perpendicular to the center line of rotation of the rotor core, where the d-axis is the line connecting the center of the magnetic pole portion in the circumferential direction of the rotor core and the center of rotation of the rotor core (Patent Document 1).

[0004] The magnetic pole section in Patent Document 1 has two permanent magnets arranged in the magnetic pole section, and the longitudinal direction of each magnet is arranged at different angles relative to the d-axis. This increases the effective magnetic flux passing through the permanent magnets on either the front or rear side of the rotor's rotational direction relative to the d-axis relative to the rotor core circumferential direction relative to the d-axis compared to the effective magnetic flux passing through the permanent magnets on either the front or rear side of the rotor's rotational direction relative to the d-axis. The effective magnetic flux here refers to the magnetic flux that passes through the permanent magnets in the rotor core and circulates via the teeth and yoke of the stator core. When the effective magnetic flux is greater on the rear side of the rotational direction relative to the d-axis, as in Patent Document 1, torque can be increased. Note that, since the product of rotational speed [rpm] and torque [N·m] is a constant value when the motor output [W] is constant, increasing the effective magnetic flux on the front side of the rotational direction relative to the d-axis reduces torque, but increases rotational speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-154152 Summary of the Invention [Problem to be solved by the invention]

[0006] In the manufacturing process for the embedded magnet rotor described above, a permanent magnet is embedded in the rotor core, and then the rotor is attached to a magnetizing device. In this manufacturing process, for example, a rotor having permanent magnets magnetized by a magnetizing magnetic field is manufactured by passing the magnetic flux of the magnetizing magnetic field through the magnetic pole sections along the d-axis. The magnetizing magnetic field here refers to the magnetic field applied to the magnetic body by a magnetizing device to magnetize the magnetic body as a permanent magnet. In Patent Document 1, the two permanent magnets in the magnetic pole sections have different angles with respect to the d-axis. Therefore, when a magnetizing magnetic field is applied along the d-axis, the amount of magnetic flux of the magnetizing magnetic field passing through the magnets differs between the two magnets. This can result in a difference in the magnetization ratios of the two magnets (a ratio indicating the degree to which a material is magnetized when an external magnetic field H is applied (magnet moment density)). This can also result in a problem of an increased risk of demagnetization of the magnet with the lower magnetization ratio. The difference in magnetization rate and demagnetization rate can cause problems such as an imbalance in the amount of magnetic flux between the two permanent magnets and a difference in durability.

[0007] The disclosed technology has been made in view of the above, and aims to provide a rotor, an electric motor, and a compressor that can make the effective magnetic flux passing through the permanent magnet on one side of the d-axis of the magnetic pole section greater than the effective magnetic flux passing through the permanent magnet on the other side of the d-axis, and can suppress differences in the magnetization rate and demagnetization rate of the two permanent magnets arranged on both sides of the d-axis in the magnetic pole section. [Means for solving the problem]

[0008] One aspect of a rotor disclosed in the present application includes a rotor core having a plurality of magnetic pole portions, each of which is provided with a permanent magnet, arranged along a circumferential direction, and in a plane perpendicular to the centerline of rotation of the rotor core, when a line connecting the center of rotation of the rotor core to the center of the magnetic pole portions in the circumferential direction of the rotor core is defined as a d-axis, the permanent magnets provided in each magnetic pole portion include a first magnet arranged on one side of the circumferential direction of the rotor core with respect to the d-axis, and a second magnet arranged on the other side of the circumferential direction of the rotor core with respect to the d-axis. In the plane, when a first angle formed by the longitudinal direction of the first magnet and the d-axis on the outer periphery of the rotor core is defined as θ1 and a second angle formed by the longitudinal direction of the second magnet and the d-axis on the outer periphery of the rotor core is defined as θ2, the first magnet and the second magnet satisfy θ1 = θ2 < 90 degrees and are arranged asymmetrically with respect to the d-axis. In the plane, one end of the first magnet on the d-axis side in the longitudinal direction is located radially inward of the rotor core than the other end of the first magnet in the longitudinal direction, and in the plane, one end of the second magnet on the d-axis side in the longitudinal direction is located radially inward of the rotor core than the other end of the second magnet in the longitudinal direction, and when the shortest distance between the first magnet and the d-axis in the plane is L1a and the shortest distance between the d-axis and the second magnet is L1b, L1a ≠ L1b is satisfied. [Effects of the Invention]

[0009] According to one aspect of the rotor disclosed in the present application, the effective magnetic flux passing through the permanent magnet on one side of the magnetic pole portion with respect to the d-axis can be made larger than the effective magnetic flux passing through the permanent magnet on the other side with respect to the d-axis, and differences in the magnetization rate and demagnetization rate of the two permanent magnets arranged on both sides of the d-axis in the magnetic pole portion can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a compressor according to a first embodiment. [Figure 2] FIG. 2 is a plan view showing the electric motor of the first embodiment. [Figure 3] FIG. 3 is a plan view showing the rotor of the first embodiment. [Figure 4] FIG. 4 is a plan view illustrating a main part of the rotor core in the first embodiment. [Figure 5] FIG. 5 is a schematic diagram for explaining the arrangement of permanent magnets in the magnetic pole portion in the first embodiment. [Figure 6] FIG. 6 is an enlarged view showing the outer circumferential surfaces of the north and south pole magnetic poles of the rotor core in the first embodiment. [Figure 7]FIG. 7 is a schematic diagram showing the outer circumferential surface of each magnetic pole portion of the rotor core in the first embodiment. [Figure 8] FIG. 8 is a schematic diagram for explaining the shape of the outer circumferential surface of the magnetic pole of the rotor core in the first embodiment. [Figure 9] FIG. 9 is a plan view showing magnetic lines of force in the first embodiment. [Figure 10] FIG. 10 is a plan view showing magnetic lines of force in the embodiment. [Figure 11] FIG. 11 is a plan view showing magnetic lines of force in a comparative example. [Figure 12] FIG. 12 is a diagram for explaining the torque of the electric motor of the embodiment. [Figure 13] FIG. 13 is a schematic diagram for explaining the arrangement of permanent magnets in the magnetic pole portion in the second embodiment. [Figure 14] FIG. 14 is a schematic diagram for explaining the arrangement of permanent magnets in the magnetic pole portion in the third embodiment. [Figure 15] FIG. 15 is a plan view showing the magnetic pole part in the first modification. [Figure 16] FIG. 16 is a plan view showing magnetic lines of force in the first modification. [Figure 17] FIG. 17 is a plan view showing the magnetic pole part in the second modification. [Figure 18] FIG. 18 is a plan view showing magnetic lines of force in the second modification. [Figure 19] FIG. 19 is a plan view showing the magnetic pole part in the third modification. [Figure 20] FIG. 20 is a plan view showing magnetic lines of force in the third modification. [Figure 21] FIG. 21 is a plan view showing a magnetic pole part in the fourth modification. [Figure 22] FIG. 22 is a plan view showing a magnetic pole part in the fifth modification. [Figure 23] FIG. 23 is a plan view showing a magnetic pole part in the sixth modification. [Figure 24] FIG. 24 is a plan view showing the magnetic pole part in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the rotor, electric motor, and compressor disclosed in the present application will be described in detail with reference to the drawings. Note that the rotor, electric motor, and compressor disclosed in the present application are not limited to the following embodiments. [Example]

[0012] (Compressor configuration) FIG. 1 is a longitudinal cross-sectional view showing a compressor of a first embodiment. As shown in FIG. 1, compressor 101 is a so-called rotary compressor and includes a container 102, a compression section 105, and an electric motor 1. Container 102 is made of a metal material and defines a sealed internal space 107. Internal space 107 of container 102 is formed in a generally cylindrical shape. When container 102 is placed upright on a horizontal surface, the central axis of the cylinder defining internal space 107 is parallel to the vertical direction. Container 102 has an oil reservoir 108 formed below internal space 107. Refrigerant oil, which serves as a lubricant for lubricating compression section 105, is stored in oil reservoir 108. Container 102 is connected to a suction pipe 111 for drawing in a refrigerant and a discharge pipe 112 for discharging the compressed refrigerant. A shaft 3 rotated by an electric motor 1 (described later) is disposed in the internal space 107 of the container 102, with one end of the shaft 3 positioned in an oil reservoir 108. The shaft 3 is supported by the container 102 so as to be rotatable around the central axis of a cylinder that forms the internal space 107. The shaft 3 supplies refrigeration oil stored in the oil reservoir 108 to the compression section 105 by rotating.

[0013] The compression section 105 is disposed at the bottom of the internal space 107 and above the oil sump 108. The compressor 101 further includes an upper muffler cover 114 and a lower muffler cover 115. The upper muffler cover 114 is disposed above the compression section 105 in the internal space 107. The upper muffler cover 114 defines an upper muffler chamber 116 therein. The lower muffler cover 115 is provided below the compression section 105 in the internal space 107 and is disposed above the oil sump 108. The lower muffler cover 115 defines a lower muffler chamber 117 therein. The lower muffler chamber 117 is in communication with the upper muffler chamber 116 via a communication passage (not shown) formed in the compression section 105. A compressed refrigerant discharge hole 118 is formed between the upper muffler cover 114 and the shaft 3, and the upper muffler chamber 116 communicates with the internal space 107 via the compressed refrigerant discharge hole 118.

[0014] Compression section 105 compresses the refrigerant supplied from suction pipe 111 as shaft 3 rotates, and supplies the compressed refrigerant to upper muffler chamber 116 and lower muffler chamber 117. The refrigerant is compatible with refrigeration oil. Motor 1 is disposed above compression section 105 in internal space 107.

[0015] (Motor configuration) Fig. 2 is a plan view showing the electric motor 1 in the first embodiment. Fig. 3 is a plan view showing the rotor in the first embodiment. As shown in Figs. 2 and 3, the electric motor 1 in the first embodiment is a concentrated winding three-phase motor with 6 poles and 9 slots. The electric motor 1 includes a rotor 21 and a stator 22 arranged on the outer periphery of the rotor 21.

[0016] The rotor 21 has a cylindrical rotor core 23 formed by laminating multiple metal plates made of a soft magnetic material such as silicon steel, and the multiple metal plates are integrated by, for example, crimping. A shaft 3 serving as the rotation axis of the rotor core 23 is inserted through a central axis that is the rotation center line of the rotor core 23, and the shaft 3 and the rotor 21 are fixed together. Although not shown, the rotor core 23 may be provided with multiple elongated refrigerant gas passages that penetrate the rotor core 23 in the axial direction (axial direction of the shaft 3). The multiple refrigerant gas passages are arranged at intervals around the axis of the shaft 3. Main parts of the rotor core 23 in the first embodiment will be described later.

[0017] The stator 22 is formed in a generally cylindrical shape and is disposed so as to surround the outer periphery of the rotor 21. The stator 22 is fixed, for example, to the inside of the container 102 of the compressor 101. As shown in FIGS. 1 and 2 , the stator 22 includes a stator core 24, an upper insulator 25, a lower insulator 26, and a plurality of windings 46.

[0018] As shown in FIGS. 2 and 3, the stator core 24 is disposed with a predetermined gap (air gap) between it and the outer peripheral surface 27 of the rotor core 23. The shape of the outer peripheral surface 27 of the rotor core 23 in the circumferential direction of the rotor core 23 will be described in detail later. The stator core 24 has nine teeth 32 extending from an annular yoke portion 31 toward the inside in the radial direction of the rotor core 23, and the nine teeth 32 are formed at equal intervals of 40 degrees (mechanical angle) in the circumferential direction of the stator core 24. Each tooth 32 has a flange (inner peripheral end) 33 that protrudes from a tip located on the inner peripheral side of the stator core 24 to both sides in the circumferential direction of the stator core 24. The teeth 32 are formed to have the same shape. As shown in FIG. 2, each tooth 32 has a winding portion 45 in which each winding 46 is wound in a concentrated winding manner. The plurality of windings 46 include three U-phase windings 46-U1 to 46-U3, three V-phase windings 46-V1 to 46-V3, and three W-phase windings 46-W1 to 46-W3. In the stator 22, the neutral wires drawn out from each winding portion 45 and bundled together are covered with an insulating tube and inserted into gaps between adjacent winding portions 45 in the circumferential direction of the stator 22 (the rotational direction R of the rotor 21) (see FIG. 2). The upper insulator 25 is fixed to the upper end of the stator core 24. The lower insulator 26 is fixed to the lower end of the stator core 24. The upper insulator 25 and the lower insulator 26 are insulating members that insulate the stator core 24 from the windings 46.

[0019] As shown in FIG. 3, the rotor core 23 of the electric motor 1 of the first embodiment has a plurality of magnet embedding holes 12a, 12b, 12c, 12d, 12e, and 12f (hereinafter also referred to as magnet embedding holes 12) into which permanent magnets 13a, 13b, 13c, 13d, 13e, and 13f (hereinafter also referred to as permanent magnets 13) are embedded. The rotor core 23 has two slit-like magnet embedding holes 12 formed in each magnetic pole portion 11, which will be described later, on an orthogonal plane, i.e., on the end face of the rotor core 23, so as to form a roughly V-shape. The two magnet embedding holes 12 in each magnetic pole portion 11 are adjacent to each other at one end and extend to the outer periphery of the rotor core 23 at the other end. Plate-shaped permanent magnets 13 are embedded in the magnet embedding holes 12. End plates are attached to both axial end faces of the rotor core 23 to prevent the permanent magnets 13 from falling out, but the end plates are not shown in the illustration to explain the main parts of the rotor core 23. The end plates are fixed to the rotor core 23 by rivets 8 that are passed through rivet holes 7 in the rotor core 23.

[0020] As described above, the rotor core 23 has six magnetic pole portions 11, i.e., three N-pole magnetic pole portions 11N and three S-pole magnetic pole portions 11S, arranged alternately along the circumferential direction of the rotor core 23 by embedding the permanent magnets 13 in the magnet embedding holes 12. Each of the N-pole magnetic pole portions 11N and S-pole magnetic pole portions 11S (hereinafter also referred to as magnetic pole portions 11) includes two permanent magnets 13 and is the outer peripheral portion of each permanent magnet 13 in the radial direction of the rotor core 23 (the portion between each permanent magnet 13 and the outer peripheral surface 27 of the rotor core 23).

[0021] In the electric motor disclosed herein, the number of pole pairs formed by the magnetic pole portions 11 (N-pole magnetic pole portions 11N and S-pole magnetic pole portions 11S) is m, where m is a natural number, and the number of teeth portions 32 is 3m. In the rotor 21, the number of magnetic pole portions 11, i.e., the number of poles, is 2m. As an example, the electric motor 1 of the first embodiment has six poles, three pole pairs, and nine teeth portions 32.

[0022] Furthermore, in a plane (hereinafter also referred to as an orthogonal plane) that is orthogonal to the rotation center line that passes through the rotation center O of the rotor 21 (rotation center of the rotor core 23) and that passes through the rotor core 23, a line connecting the center of the magnetic pole portions 11 in the circumferential direction of the rotor 21 to the rotation center O is defined as a d-axis D, and a line connecting the center between adjacent magnetic pole portions 11 in the circumferential direction of the rotor 21 to the rotation center O is defined as a q-axis Q. Therefore, in the orthogonal plane, the center of the magnetic pole portions 11 in the circumferential direction of the rotor 21 is a position along the radial direction of the rotor core 23, and refers to a position on a line that coincides with the q-axis Q. The rotation center line that passes through the rotation center O of the rotor 21 coincides with the center line of the shaft 3 that is along the axial direction of the shaft 3. The rotor core 23 has a plurality of d-axes D that extend radially from the rotation center O at equal intervals in the circumferential direction of the rotor core 23, and a plurality of q-axes Q that extend radially from the rotation center O at equal intervals in the circumferential direction of the rotor core 23.

[0023] In each magnetic pole portion 11, two plate-shaped permanent magnets 13 are provided on both sides of the d-axis D and are arranged to form a substantial V-shape on an orthogonal plane. The arrangement of the two permanent magnets 13 in the magnetic pole portion 11 will be described in detail later.

[0024] Fig. 4 is a plan view illustrating a main portion of the rotor core 23 in the first embodiment. As shown in Fig. 4, the rotor core 23 has a plurality of q-axis side non-magnetic portions 14a to 14f, 15a to 15f (hereinafter referred to as q-axis side non-magnetic portions 14, 15) formed contiguous with the magnet embedding holes 12 and near the q-axis Q, a plurality of d-axis side non-magnetic portions 19a to 19f (hereinafter referred to as d-axis side non-magnetic portions 19) formed contiguous with the magnet embedding holes 12 on the d-axis D, a plurality of grooves 16, 17, and a plurality of bridge portions 18 formed between the q-axis side non-magnetic portions 14, 15 and the grooves 16, 17.

[0025] Here, of the q-axis side non-magnetic portions 14, 15 formed at the ends of each magnet embedding hole 12, one q-axis side non-magnetic portion 14 (14a to 14f) is located on the front side in the rotational direction R of the rotor 21 (rotational direction R of the rotor core 23), and the other q-axis side non-magnetic portion 15 (15a to 15f) is located on the rear side in the rotational direction R. In each magnetic pole portion 11, the q-axis side non-magnetic portions 14, 15 are formed by extending from each end of the two magnet embedding holes 12 located on the outer circumferential surface 27 side of the rotor core 23 toward the outside in the radial direction of the rotor core 23, i.e., toward the outer circumferential surface 27 of the rotor core 23. In each magnetic pole portion 11, the d-axis side non-magnetic portion 19 is formed by connecting adjacent ends of the two magnet embedding holes 12.

[0026] The q-axis-side non-magnetic portions 14, 15 and the d-axis-side non-magnetic portion 19 are so-called flux barriers, and are formed as spaces continuous with the magnet embedding holes 12. The q-axis-side non-magnetic portions 14, 15 and the d-axis-side non-magnetic portion 19 prevent the creation of a magnetic path between circumferentially adjacent magnetic pole portions 11 of the rotor core 23, in which magnetic flux short-circuits so as to circulate between the magnetic pole portions 11 via the flange portions 33 of the teeth portions 32 without passing through the yoke portion 31 of the stator 22. In other words, the rotor core 23 has through holes formed therethrough that run along the rotational centerline of the rotor core 23 that is parallel to the axial direction of the shaft 3. The regions of the through holes that are filled with the permanent magnets 13 are the magnet embedding holes 12, and the regions of the through holes that are not filled with the permanent magnets 13 are the q-axis-side non-magnetic portions 14, 15 and the d-axis-side non-magnetic portion 19, which are gaps that serve as non-magnetic portions.

[0027] Grooves 16 and 17 are formed in the outer peripheral surface 27 of the rotor core 23 between adjacent magnetic pole portions 11 in the circumferential direction of the rotor core 23, by cutting out portions of the outer peripheral surface 27 in the radial direction of the rotor core 23 and recessing the portions. In other words, the grooves 16 and 17 are located between adjacent q-axis side non-magnetic portions 14 and 15 in the circumferential direction of the rotor core 23, and are arranged on the q-axis Q.

[0028] (Characteristic structure of the rotor core) Next, a description will be given of the characteristic structure of the rotor 21 in the embodiment 1. The characteristics of the embodiment 1 include the arrangement of the two permanent magnets 13 in each magnetic pole portion 11.

[0029] (Arrangement of permanent magnets in the magnetic pole section) Fig. 5 is a schematic diagram for explaining the arrangement of the permanent magnets 13 of the magnetic pole portion 11 in Example 1. For convenience, Fig. 5 shows only the permanent magnets 13, and does not show the magnet embedding holes 12, the q-axis side non-magnetic portions 14 and 15, and the d-axis side non-magnetic portion 19.

[0030] As shown in FIG. 5, the permanent magnets 13 (13a to 13f) provided in each magnetic pole portion 11 in the first embodiment include a first magnet 13A arranged on one circumferential side of the rotor core 23 with respect to the d-axis D, and a second magnet 13B arranged on the other circumferential side of the rotor core 23 with respect to the d-axis D. The two permanent magnets 13 in one magnetic pole portion 11 are referred to as the first magnet 13A and the second magnet 13B, and the permanent magnets 13 provided in each magnetic pole portion 11 aligned in the circumferential direction of the rotor core 23 are also referred to as permanent magnets 13a to 13f. In an orthogonal plane, the first magnet 13A and the second magnet 13B have the same shape and are the same size. That is, the first magnet 13A and the second magnet 13B have the same external dimensions.

[0031] In the first embodiment, of the two permanent magnets 13, one permanent magnet 13 arranged on the front side of the rotation direction R of the rotor 21 relative to the d axis D is referred to as the first magnet 13A, and the other permanent magnet 13 arranged on the rear side of the rotation direction R of the rotor 21 relative to the d axis D is referred to as the second magnet 13B, but this is not limited to this. In other words, in the following description, if the arrangement of the two permanent magnets 13 in the rotation direction R of the rotor 21 relative to the d axis D is not specified, one permanent magnet 13 arranged on the front side of the rotation direction R of the rotor 21 relative to the d axis D may be referred to as the second magnet 13B, and the other permanent magnet 13 arranged on the rear side of the rotation direction R of the rotor 21 relative to the d axis D may be referred to as the first magnet 13A.

[0032] In an orthogonal plane, when a first angle formed by a line parallel to the longitudinal direction of first magnet 13A and d-axis D on the outer periphery of rotor core 23 is defined as θ1 [degrees] and a second angle formed by a line parallel to the longitudinal direction of second magnet 13B and d-axis D on the outer periphery of rotor core 23 is defined as θ2 [degrees], first magnet 13A and second magnet 13B are arranged so that first angle θ1 and second angle θ2 are equal and are arranged asymmetrically with respect to d-axis D. Furthermore, both first angle θ1 and second angle θ2 are less than 90 degrees, and in Example 1, θ1 = θ2 = 60 [degrees].

[0033] Furthermore, in the orthogonal plane, one end of plate-shaped first magnet 13A on the d-axis D side in the longitudinal direction is located radially inward of rotor core 23 than the other end of first magnet 13A in the longitudinal direction. Similarly, in the orthogonal plane, one end of plate-shaped second magnet 13B on the d-axis D side in the longitudinal direction is located radially inward of rotor core 23 than the other end of second magnet 13B in the longitudinal direction. Therefore, in the orthogonal plane, first magnet 13A and second magnet 13B are arranged to form a V shape with d-axis D between them.

[0034] As described above, by arranging the first magnet 13A and the second magnet 13B asymmetrically with respect to the d-axis D, it is possible to adjust the path of the magnetic flux passing through the outer circumferential surface of each magnetic pole portion 11 (magnetic pole outer circumferential surface 29 described later), and to make the effective magnetic flux passing through the first magnet 13A of the magnetic pole portion 11 different from the effective magnetic flux passing through the second magnet 13B. Therefore, it is possible to make the effective magnetic flux passing through the permanent magnet 13 on one side with respect to the d-axis D larger than the effective magnetic flux passing through the permanent magnet 13 on the other side with respect to the d-axis D. Note that the effective magnetic flux here refers to the magnetic flux that passes through the permanent magnet 13 and circulates via the teeth portions 32 and yoke portions 31 of the stator core 24.

[0035] In addition, as will be described in detail later, the first and second magnets 13A and 13B form a first angle θ1 and a second angle θ2 with respect to the d-axis D, respectively, such that θ1=θ2<90[degrees] (Formula 1) By satisfying this condition, it is possible to suppress the occurrence of a difference in magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B in each magnetic pole portion 11. Therefore, in the rotor 21 of the first embodiment, in the first magnet 13A and the second magnet 13B, it is possible to suppress the imbalance of each magnetic flux amount and the occurrence of a difference in durability, so that the quality of the electric motor 1 can be improved.

[0036] (Asymmetric arrangement of the first magnet and the second magnet) In the magnetic pole portion 11 in the first embodiment, in the orthogonal plane, when the shortest distance between the first magnet 13A and the d-axis D is L1a [mm], and the shortest distance between this d-axis D and the second magnet 13B is L1b [mm], the shortest distances L1a and L1b are L1a ≠ L1b ··· (Equation 2) satisfies.

[0037] That is, the first magnet 13A and the second magnet 13B are different in the direction orthogonal to the d-axis D with respect to the d-axis D, in other words, in the circumferential direction of the rotor core 23. Thereby, since the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, the path of the magnetic flux passing through the magnetic pole outer peripheral surface 29 can be adjusted, and the effective magnetic flux passing through the first magnet 13A of the magnetic pole portion 11 and the effective magnetic flux passing through the second magnet 13B can be made different. Therefore, the effective magnetic flux passing through the permanent magnet 13A on one side with respect to the d-axis D can be made larger than the effective magnetic flux passing through the magnetic pole outer peripheral surface 29 on the other side with respect to the d-axis D. In Equation 2, the arrangement of the first magnet 13A and the second magnet 13B in the rotation direction R of the rotor 21 with respect to the d-axis D is not limited.

[0038] In the first embodiment, as an example, in the orthogonal plane, when the first magnet 13A is arranged on the front side in the rotation direction R of the rotor 21 with respect to the d-axis D, and the second magnet 13B is arranged on the rear side in the rotation direction R with respect to the d-axis D, the shortest distances L1a and L1b are L1a < L1b ··· (Equation 3) As a result, in addition to the effect of satisfying Equation 2, in one magnetic pole portion 11, the shortest distance L1a between the first magnet 13A arranged on the front side of the d-axis D in the rotation direction R of the rotor 21 and the d-axis D is smaller than the shortest distance L1b between the second magnet 13B arranged on the rear side of the d-axis D in the rotation direction R and the d-axis D. This reduces the effective magnetic flux passing through the first magnet 13A, which is the permanent magnet 13 on the front side of the magnetic pole portion 11 in the rotation direction R, and increases the effective magnetic flux passing through the second magnet, which is the permanent magnet 13 on the rear side of the magnetic pole portion 11 in the rotation direction R, compared to when the shortest distances L1a and L1b are equal. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side of the magnetic pole portion 11 in the rotation direction R can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side of the rotation direction R, thereby improving torque. In the first embodiment, L1a:L1b ≈ 1:2.

[0039] In addition, in the orthogonal plane, when the shortest distance between first magnet 13A and center of rotation O of rotor core 23 is L2a [mm] and the shortest distance between second magnet 13B and center of rotation O of rotor core 23 is L2b [mm], the shortest distances L2a and L2b are L2a≠L2b (Formula 4) Meet the following.

[0040] In other words, the first magnet 13A and the second magnet 13B are arranged differently in the direction along the d-axis D, in other words, in the radial direction of the rotor core 23, with respect to the d-axis D. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so that the path of the magnetic flux passing through the magnetic pole outer peripheral surface 29 can be adjusted, and the effective magnetic flux passing through the first magnet 13A and the effective magnetic flux passing through the second magnet 13B of the magnetic pole portion 11 can be made different. Therefore, the effective magnetic flux passing through the permanent magnet 13 on one side with respect to the d-axis D in the magnetic pole portion 11 can be made larger than the effective magnetic flux passing through the permanent magnet 13 on the other side with respect to the d-axis D.

[0041] In Example 1, as an example, in the orthogonal plane, when the first magnet 13A is arranged on the front side of the rotation direction R of the rotor core 23 with respect to the d-axis D, and the second magnet 13B is arranged on the rear side of the rotation direction R of the rotor core 23 with respect to the d-axis, the shortest distances L2a and L2b are L2a < L2b ···(Equation 5) are satisfied. Thereby, in addition to the effect in the case where Equation 4 is satisfied, in one magnetic pole portion 11, the shortest distance L2a between the first magnet 13A arranged on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D and the rotation center O of the rotor core 23 is shorter than the shortest distance L2b between the second magnet 13B arranged on the rear side of the rotation direction R with respect to the d-axis D and the rotation center O of the rotor core 23. As a result, compared with the case where the shortest distance L2a and the shortest distance L2b are equal, the effective magnetic flux passing through the permanent magnet 13 (the first magnet 13A) on the front side of the rotation direction R with respect to the d-axis D in the magnetic pole portion 11 is reduced, and the effective magnetic flux passing through the permanent magnet 13 (the second magnet 13B) on the rear side of the rotation direction R with respect to the d-axis D in the magnetic pole portion 11 can be increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (the second magnet 13B) on the rear side of the rotation direction R in the magnetic pole portion 11 can be made larger than the effective magnetic flux passing through the permanent magnet 13 (the first magnet 13A) on the front side of the rotation direction R in the magnetic pole portion 11, and the torque can be improved. In Example 1, L2a:L2b ≒ 1:1.2 is set.

[0042] In other words, in Example 1, in the orthogonal plane, among the long sides along the longitudinal direction of the first magnet 13A and the second magnet 13B, the shortest distance between the first magnet 13A and the d-axis D on the straight line extending the inner long side in the radial direction of the rotor core 23 in the first magnet 13A is a [mm], and the shortest distance between the second magnet 13B and the d-axis D on the straight line extending the inner long side in the radial direction of the rotor core 23 in the second magnet 13B is b [mm]. When the shortest distances a and b are a > b ···(Equation 6) are satisfied.

[0043] In other words, the arrangement of the first magnet 13A and the second magnet 13B satisfies the above-mentioned formula 3 (and formula 2), and also satisfies formula 5 (and formula 4), thereby satisfying formula 6. In other words, the first magnet 13A and the second magnet 13B in Example 1 are positioned at different positions in the circumferential direction of the rotor core 23, and are also positioned at different positions in the radial direction of the rotor core 23. As a result, the first magnet 13A and the second magnet 13B are positioned asymmetrically with respect to the d-axis D, so that the path of the magnetic flux passing through the magnetic pole outer peripheral surface 29 can be adjusted, and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D in the magnetic pole portion 11 can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D.

[0044] (Outer surface of rotor core) Next, the shape of the outer peripheral surface 27 of the rotor core 23 will be described. As shown in FIG. 4 , in an orthogonal plane of the rotor core 23, a portion of the outer peripheral surface 27 of the rotor core 23 that forms one pole pair is defined as a one-pole-pair outer peripheral surface 28. In addition, the number of pole pairs formed by the magnetic pole portions 11 (a set of an N-pole magnetic pole portion 11N and an S-pole magnetic pole portion 11S) in the orthogonal plane is defined as m (m is a natural number). In this case, the overall shape of the outer peripheral surface 27 of the rotor core 23 in the orthogonal plane is formed by repeating the shape of one one-pole-pair outer peripheral surface 28 m times in the circumferential direction of the rotor core 23. In other words, in the orthogonal plane, each of the m one-pole-pair outer peripheral surfaces 28 is formed to be rotationally symmetrical with respect to the center of rotation O of the rotor 21. In other words, in an orthogonal plane, the outer circumferential surface 27 of the rotor core 23 is divided into m equal parts in the circumferential direction based on the q-axis Q (described later), and each of the m pole-pair outer circumferential surfaces 28 is a pole-pair outer circumferential surface 28, and each of the m pole-pair outer circumferential surfaces 28 has the same shape. As a result, the magnetic flux path formed by the rotor core 23 and the stator core 24 radially opposed to the rotor core 23 is periodically repeated m times. As a result, the same magnetic flux density distribution is periodically repeated every 360 / m mechanical degrees, or every 360 electrical degrees, thereby suppressing an increase in vibration due to irregular fluctuations in the magnetic flux density distribution during one rotation of the rotor core 23. For example, the outer circumferential surface 27 of the rotor core 23 in the first embodiment has three pole-pair outer circumferential surfaces 28 formed thereon around the entire circumference of the rotor core 23.

[0045] Here, on the above-mentioned orthogonal plane, of the ends of the two permanent magnets 13 of the magnetic pole portion 11 located on the outer circumferential surface 27 side of the rotor core 23, the points located most outer in the radial direction of the rotor core 23 are defined as angles C1 and C2 on the d-axis D side of each end. Also, a line passing through the rotation center O of the rotor 21 and the angle C1 at the end of the permanent magnet 13 located on the front side in the rotation direction R of the rotor 21 is defined as a first boundary line B1. Also, a line passing through the rotation center O of the rotor 21 and the angle C2 at the end of the permanent magnet 13 located on the rear side in the rotation direction R of the rotor 21 is defined as a second boundary line B2. In this case, the outer circumferential surface 27 of each magnetic pole portion 11 of the rotor core 23 has a magnetic pole outer circumferential surface 29 formed in a range between two boundary lines (first boundary line B1 and second boundary line B2) that pass through one magnetic pole portion 11.

[0046] Therefore, the pole pair outer surface 28 is the range of one pole pair, in the circumferential direction of the outer surface 27 of the rotor core 23, including the magnetic pole outer surface 29 (hereinafter also referred to as the N-pole outer surface 29N) of the N-pole magnetic pole portion 11N and the magnetic pole outer surface 29 (hereinafter also referred to as the S-pole outer surface 29S) of the S-pole magnetic pole portion 11S that are aligned in the circumferential direction of the rotor core 23, as shown in Figure 4, the inner surface of the groove portion 16 located between the N-pole outer surface 29N and the S-pole outer surface 29S, the inner surface of the groove portion 17 located on the rear side of the rotational direction R relative to the N-pole magnetic pole portion 11N, the inner surface of the groove portion 17 located on the front side of the rotational direction R relative to the q-axis Q, and the inner surface of the groove portion 17 located on the rear side of the rotational direction R relative to the q-axis Q, in the groove portion 17 located on the front side of the rotational direction R relative to the S-pole magnetic pole portion 11S. One magnetic pole outer peripheral surface 29 (N-pole outer peripheral surface 29N or S-pole outer peripheral surface 29S) is the range of the outer peripheral surface 27 of rotor core 23, located between two circumferentially adjacent q axes Q, that is, the range of the side surface on the outer periphery of the magnetic pole portion 11, not including groove portions 16, 17. In other words, each magnetic pole outer peripheral surface 29 (N-pole outer peripheral surface 29N and S-pole outer peripheral surface 29S) is a portion formed in the range between two boundary lines (first boundary line B1, second boundary line B2) that pass through one magnetic pole portion 11 in the circumferential direction of the outer peripheral surface 27.

[0047] FIG. 6 is an enlarged view showing the magnetic pole outer peripheral surfaces 29 of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S of the rotor core 23 in the first embodiment. As shown in FIGS. 4 and 6 , in an orthogonal plane, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S are formed in shapes that do not coincide with each other when one of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is virtually rotated 60 degrees around the rotation center O of the rotor 21 and placed on the other of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S. Note that the magnetic pole portion to be virtually rotated may be either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S. Furthermore, the direction of rotation around the rotation center O may be either clockwise or counterclockwise. Here, the explanation will be given on the assumption that the north magnetic pole portion 11N is virtually rotated counterclockwise by 60 degrees and overlapped with the south magnetic pole portion 11S.

[0048] In the rotor core 23 in the first embodiment, when focusing on one pole-pair outer peripheral surface 28, the pole-pair outer peripheral surface 28 is formed in a different shape from each other with respect to the q-axis Q. This makes it possible to make the magnetic flux density distribution passing between the N-pole permanent magnet 13 and the tooth portion 32 adjacent to the N-pole permanent magnet 13 and the magnetic flux density distribution passing between the S-pole permanent magnet 13 and the tooth portion 32 adjacent to the S-pole permanent magnet 13, in the N-pole permanent magnet 13 and the S-pole permanent magnet 13 constituting one pole pair, closer to symmetry with respect to the q-axis Q. As a result, the magnetic flux density distribution at the position of the air gap formed between the rotor core 23 and the tooth portion 32 within the range of the pole-pair outer peripheral surface 28 (measured or analyzed over the circumferential direction, the radial magnetic flux density [T] at the air gap position) closer to a sine wave can be made even closer to a sine wave.

[0049] For example, in the first embodiment, the radius of curvature r of the radius change region A3 (described later) where the distance from the rotation center O of the rotor 21 to the outer circumferential surface 27 of the rotor core 23 changes is different between the radius change region A3 of the N-pole outer circumferential surface 29N and the radius change region A3 of the S-pole outer circumferential surface 29S. This makes it easy to realize that the pole pair outer circumferential surfaces 28 have different shapes relative to the q-axis Q.

[0050] When one of the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S is overlapped with the other magnetic pole portion 11, the rotation angle of the one magnetic pole portion 11 around the rotation center O is 360 / (2m) degrees. (The number of pole pairs is m.) In the following description, the rotation angle when the N-pole magnetic pole portion 11N is virtually rotated around the rotation center O of the rotor 21 is also 360 / (2m) degrees. For example, in the first embodiment, the number of pole pairs is m=3, so when the N-pole magnetic pole portion 11N is virtually rotated around the rotation center O of the rotor 21 to overlap with the S-pole magnetic pole portion 11S, the rotation angle is 360 / 6=60 degrees.

[0051] (Shape of the outer surface of the magnetic pole) Fig. 7 is a schematic diagram showing the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 of the rotor core 23 in the first embodiment. Fig. 8 is a schematic diagram for explaining the shape of the magnetic pole outer peripheral surface 29 of the rotor core 23 in the first embodiment.

[0052] As shown in Figures 7 and 8, in an orthogonal plane, the N-pole outer surface 29N of the N-pole magnetic pole portion 11N is formed in an asymmetric shape with respect to the N-pole d-axis DN, which is the d-axis D of this N-pole magnetic pole portion 11N, and the S-pole outer surface 29S of the S-pole magnetic pole portion 11S is formed in an asymmetric shape with respect to the S-pole d-axis DS, which is the d-axis of this S-pole magnetic pole portion 11S.

[0053] In this way, by devising the shape of the magnetic pole outer peripheral surface 29 formed within the range of each magnetic pole portion 11, it is possible to make the magnetic flux density distribution passing between the N-pole permanent magnet 13 and the tooth portion 32 adjacent to this N-pole permanent magnet 13, and the magnetic flux density distribution passing between the S-pole permanent magnet 13 and the tooth portion 32 adjacent to this S-pole permanent magnet 13, in the N-pole permanent magnet 13 and the S-pole permanent magnet 13 forming one pole pair, closer to being more symmetrical with respect to the q-axis Q. Therefore, in addition to the effect obtained by devising the shape of one pole pair outer peripheral surface 28 described above, it is possible to make the magnetic flux density distribution in the air gap formed between the rotor core 23 and the tooth portion 32 within the range of one pole pair outer peripheral surface 28 closer to a sine wave.

[0054] (N pole outer surface shape) Specifically, as shown in Figure 7, the N-pole outer surface 29N of the N-pole magnetic pole portion 11N has an N-pole front outer surface 29N-F located on the front side of the rotation direction R of the rotor 21 relative to the N-pole d-axis DN, and an N-pole rear outer surface 29N-R located on the rear side of the rotation direction R relative to the N-pole d-axis DN.

[0055] FIG. 8 is a diagram showing the magnetic pole portion 11 virtually folded back along the d-axis D in the orthogonal plane of the rotor core 23, with the front outer peripheral surface 29-F virtually overlapping the rear outer peripheral surface 29-R. Here, a case where the N-pole magnetic pole portion 11N is virtually folded back is described. As shown in FIG. 8, when the N-pole magnetic pole portion 11N is virtually folded back and overlapped along the N-pole d-axis DN in the orthogonal plane of the rotor core 23, the N-pole front outer peripheral surface 29N-F has a small-diameter outer peripheral surface 34 located more inwardly than the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23. On the other hand, the N-pole rear outer peripheral surface 29N-R does not have a portion located more inwardly than the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23. In other words, N pole front side outer peripheral surface 29N-F has only a portion overlapping with N pole rear side outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion located more inward than N pole rear side outer peripheral surface 29N-R (small diameter outer peripheral surface 34). When viewed from the N pole rear side outer peripheral surface 29N-R, N pole rear side outer peripheral surface 29N-R has only a portion overlapping with N pole front side outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion located more outward than N pole front side outer peripheral surface 29N-F (large diameter outer peripheral surface 36).

[0056] (Shape of the outer surface of the S pole) Also, similar to the N-pole outer surface 29N described above, as shown in Figure 7, the S-pole outer surface 29S of the S-pole magnetic pole portion 11S has an S-pole front outer surface 29S-F located on the front side of the S-pole d-axis DS in the rotational direction R of the rotor 21, and an S-pole rear outer surface 29S-R located on the rear side of the S-pole d-axis DS in the rotational direction R.

[0057] A case where the S-pole magnetic pole portion 11S is virtually folded back will be described. As shown in Fig. 8, when the S-pole magnetic pole portion 11S is virtually folded back along the S-pole d-axis DS in the orthogonal plane of the rotor core 23 and overlapped, the S-pole front-side outer peripheral surface 29S-F has a small-diameter outer peripheral surface 34 located more inward than the S-pole rear-side outer peripheral surface 29S-R in the radial direction of the rotor core 23. On the other hand, the S-pole rear-side outer peripheral surface 29S-R does not have a portion located more inward than the S-pole front-side outer peripheral surface 29S-F in the radial direction of the rotor core 23. In other words, the S-pole front-side outer peripheral surface 29S-F only has a portion overlapping with the S-pole rear-side outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion located more inward than the S-pole rear-side outer peripheral surface 29S-R (small-diameter outer peripheral surface 34). When viewed from the S pole rear side outer peripheral surface 29S-R, the S pole rear side outer peripheral surface 29S-R has only a portion that overlaps with the S pole front side outer peripheral surface 29S-F (overlapping outer peripheral surface 35) and a portion that is located more outer than the S pole front side outer peripheral surface 29S-F (large diameter outer peripheral surface 36).

[0058] (Relationship between the outer surface of the north pole and the outer surface of the south pole) Also, as shown in Figures 4 and 6, in an orthogonal plane, the N-pole rear outer surface 29N-R and the S-pole rear outer surface 29S-R are formed in shapes that do not coincide with each other when the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S are overlapped by virtually rotating the rotor 21 around the rotation center O.

[0059] Specifically, when N pole rear side outer peripheral surface 29N-R is virtually rotated 360 / (2 m) degrees around rotation center O of rotor 21 in an orthogonal plane of rotor core 23 and overlapped with S pole rear side outer peripheral surface 29S-R, S pole rear side outer peripheral surface 29S-R has small diameter outer peripheral surface 34 (see FIG. 4) located more inward than N pole rear side outer peripheral surface 29N-R in the radial direction of rotor core 23, and N pole rear side outer peripheral surface 29N-R does not have a portion located more inward than S pole rear side outer peripheral surface 29S-R in the radial direction of rotor core 23. In other words, S pole rear side outer peripheral surface 29S-R only has a portion overlapping with N pole rear side outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion (small diameter outer peripheral surface 34) located more inward than N pole rear side outer peripheral surface 29N-R. The N-pole rear-side outer peripheral surface 29N-R has only a portion that overlaps with the S-pole rear-side outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion that is located more outer than the S-pole rear-side outer peripheral surface 29S-R (large-diameter outer peripheral surface 36).

[0060] Alternatively, conversely, when N-pole rear-side outer peripheral surface 29N-R is virtually rotated 360 / (2 m) degrees around rotation center O of rotor 21 in the orthogonal plane of rotor core 23 and overlapped with S-pole rear-side outer peripheral surface 29S-R, N-pole rear-side outer peripheral surface 29N-R may have a small-diameter outer peripheral surface (not shown) located more inward than S-pole rear-side outer peripheral surface 29S-R in the radial direction of rotor core 23, and S-pole rear-side outer peripheral surface 29S-R may not have a portion located more inward than N-pole rear-side outer peripheral surface 29N-R in the radial direction of rotor core 23. In other words, N-pole rear-side outer peripheral surface 29N-R may be formed to have a portion overlapping with S-pole rear-side outer peripheral surface 29S-R (overlapping outer peripheral surface 35) and a portion (small-diameter outer peripheral surface 34) located more inward than S-pole rear-side outer peripheral surface 29S-R. The S-pole rear-side outer peripheral surface 29S-R may be formed to have only a portion that overlaps with the N-pole rear-side outer peripheral surface 29N-R (overlapping outer peripheral surface 35) and a portion that is located more outer than the N-pole rear-side outer peripheral surface 29N-R (large diameter outer peripheral surface 36).

[0061] For example, in the first embodiment, the radius of curvature r of the radius change region A3, where the distance from the rotation center O of the rotor 21 to the outer circumferential surface of the rotor core 23 changes, is different between the radius change region A3 of the N-pole outer circumferential surface 29N and the radius change region A3 of the S-pole outer circumferential surface 29S. This makes it easy to virtually rotate either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S by 360 / (2 m) [degrees] around the rotation center O of the rotor 21 and overlap the other magnetic pole portion of either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S, so that they do not match each other.

[0062] Similarly, in the orthogonal plane of the rotor core 23, the N-pole front outer peripheral surface 29N-F and the S-pole front outer peripheral surface 29S-F are formed in shapes that do not coincide with each other when the rotor 21 is virtually rotated 360 / (2 m) degrees around the rotation center O to overlap the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S (see Figure 4).

[0063] Specifically, when N-pole front outer peripheral surface 29N-F is virtually rotated 360 / (2 m) degrees around rotation center O of rotor 21 in an orthogonal plane of rotor core 23 and overlapped with S-pole front outer peripheral surface 29S-F, S-pole front outer peripheral surface 29S-F has small-diameter outer peripheral surface 34 (see FIG. 4) located more inward than N-pole front outer peripheral surface 29N-F in the radial direction of rotor core 23, and N-pole front outer peripheral surface 29N-F does not have a portion located more inward than S-pole front outer peripheral surface 29S-F in the radial direction of rotor core 23. In other words, S-pole front outer peripheral surface 29S-F only has a portion overlapping with N-pole front outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion (small-diameter outer peripheral surface 34) located more inward than N-pole front outer peripheral surface 29N-F. The N-pole front outer peripheral surface 29N-F has only a portion that overlaps with the S-pole front outer peripheral surface 29S-F (overlapping outer peripheral surface 35) and a portion that is located more outer than the S-pole front outer peripheral surface 29S-F (large diameter outer peripheral surface 36).

[0064] Alternatively, conversely, when N-pole front side outer peripheral surface 29N-F is virtually rotated 360 / (2 m) degrees around rotation center O of rotor 21 in the orthogonal plane of rotor core 23 and overlapped with S-pole front side outer peripheral surface 29S-F, N-pole front side outer peripheral surface 29N-F may have a small-diameter outer peripheral surface (not shown) located more inward than S-pole front side outer peripheral surface 29S-F in the radial direction of rotor core 23, and S-pole front side outer peripheral surface 29S-F may not have a portion located more inward than N-pole front side outer peripheral surface 29N-F in the radial direction of rotor core 23. In other words, N-pole front side outer peripheral surface 29N-F may be formed to have a portion overlapping with S-pole front side outer peripheral surface 29S-F (overlapping outer peripheral surface 35) and a portion (small-diameter outer peripheral surface 34) located more inward than S-pole front side outer peripheral surface 29S-F. The S-pole front outer peripheral surface 29S-F may be formed to have only a portion that overlaps with the N-pole front outer peripheral surface 29N-F (overlapping outer peripheral surface 35) and a portion that is located more outer than the N-pole front outer peripheral surface 29N-F (large diameter outer peripheral surface 36).

[0065] For example, in the first embodiment, the radius of curvature r of the radius change region A3, where the distance from the rotation center O of the rotor 21 to the magnetic pole outer peripheral surface 29 of the rotor core 23 changes, is different between the radius change region A3 of the N-pole outer peripheral surface 29N and the radius change region A3 of the S-pole outer peripheral surface 29S. This makes it easy to virtually rotate either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S by 360 / (2 m) [degrees] around the rotation center O of the rotor 21 and overlap the other magnetic pole portion of either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S, so that they do not match each other.

[0066] In the orthogonal plane described above, the magnetic pole outer peripheral surface 29, which is the side surface on the outer periphery of the magnetic pole portion 11, is formed so that the distance between the magnetic pole outer peripheral surface 29 and the rotation center O gradually decreases from the d-axis D to the q-axis Q. Therefore, in the orthogonal plane, as shown in FIG. 4, the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 has an outer diameter L at which the distance from the rotation center O of the rotor 21 at a position on the d-axis D, i.e., the radius of the rotor core 23, is the maximum. Also, in the orthogonal plane, the N-pole outer peripheral surface 29N of the N-pole magnetic pole portion 11N and the S-pole outer peripheral surface 29S of the S-pole magnetic pole portion 11S are the same distance from the rotation center O at a position on the d-axis D, i.e., the outer diameter L.

[0067] In addition, the outer peripheral surface 27 of the rotor core 23 has a groove region A1 in which the inner surface 16a of the groove 16 is formed so that the q-axis Q passes through the groove 16, and a groove region A1 in which the inner surface 17a of the groove 17 is formed so that the q-axis Q passes through the groove 17.

[0068] 4 and 7, the magnetic pole outer peripheral surface 29 has a constant diameter region A2 formed at a position where the d-axis D passes and whose distance from the center of rotation O of the rotor 21 is constant, and a diameter change region A3 formed between the groove region A1 and the constant diameter region A2 and whose distance from the center of rotation O of the rotor 21 varies. The constant diameter region A2 is a maximum radius of curvature region formed with a maximum radius of curvature rm from the center of rotation O. The radius change region A3 is formed with a plurality of radii of curvature smaller than the maximum radius of curvature rm from the center of rotation O in the constant diameter region A2.

[0069] 4, the constant diameter region A2 on the N-pole magnetic pole portion 11N side is referred to as constant diameter region An2, the front side of this constant diameter region An2 in the direction of rotation R is referred to as constant diameter region An2-F, and the rear side of this constant diameter region An2 in the direction of rotation R is referred to as constant diameter region An2-R. Similarly, the constant diameter region A2 on the S-pole magnetic pole portion 11S side is referred to as constant diameter region As2, the front side of this constant diameter region As2 in the direction of rotation R is referred to as constant diameter region As2-F, and the rear side of this constant diameter region As2 in the direction of rotation R is referred to as constant diameter region As2-R.

[0070] The radius of curvature r of the multiple radii of curvature forming the radius change region A3 gradually decreases toward grooves 16, 17. For simplicity's sake, the combination of radii of curvature forming the radius change region A3 on N pole front outer peripheral surface 29N-F is assumed to be equal to the combination of radii of curvature forming the radius change region A3 on N pole rear outer peripheral surface 29N-R. That is, the first radius of curvature r1-F of the front side radius change region A3-F and the first radius of curvature r1-R of the rear side radius change region A3-R are expressed as r1-F = r1-R = r1, and the second radius of curvature r2-F of the front side radius change region A3-F and the second radius of curvature r2-R of the rear side radius change region A3-R are expressed as r2-F = r2-R = r2. As an example, the radius change region A3 includes a first region A3-1 having a first curvature radius r1 smaller than the maximum curvature radius rm, and a second region A3-2 having a second curvature radius r2 smaller than the first curvature radius r1. In the radius change region A3, the first region A3-1 and the second region A3-2 are formed in this order from the constant diameter region A2 toward the groove region A1. In the first embodiment, the difference between the first curvature radius r1 and the second curvature radius r2 is relatively small, so the first region A3-1 and the second region A3-2 are smoothly connected. The centers Or (Or1, Or2) of the curvature radii r (r1, r2) are positioned so that they approach the outer peripheral surface 27 of the rotor core 23 as the curvature radius decreases. The number of types of curvature radii is not limited to two.

[0071] In Fig. 4, of the second radius of curvature r2-F of the front radius changing region A3-F, the second radius of curvature on the N-pole magnetic pole portion 11N side is the second radius of curvature rn2-F, and the second radius of curvature on the S-pole magnetic pole portion 11S side is the second radius of curvature rs2-F. Similarly, of the second radius of curvature r2-R of the rear radius changing region A3-R, the second radius of curvature on the N-pole magnetic pole portion 11N side is the second radius of curvature rn2-R, and the second radius of curvature on the S-pole magnetic pole portion 11S side is the second radius of curvature rs2-R. Note that the first radius of curvature r1 is not shown in Fig. 4.

[0072] 7, the constant diameter region A2 has a front constant region A2-F located forward in the rotational direction R of the rotor 21 with respect to the d-axis D, and a rear constant region A2-R located backward in the rotational direction R with respect to the d-axis D. The circumferential length of the front constant region A2-F is smaller than the circumferential length of the rear constant region A2-R. This makes it easy to obtain a shape in each magnetic pole outer circumferential surface 29 in which the air gap formed within the range of the front outer circumferential surface 29-F gradually increases toward the q-axis Q, and the rate at which the air gap formed within the range of the rear outer circumferential surface 29-R gradually increases toward the q-axis Q is smaller than the rate at which the air gap formed within the range of the front outer circumferential surface 29-F gradually increases toward the q-axis Q. In other words, because the front constant region A2-F is smaller than the rear constant region A2-R, when the N-pole magnetic pole portion 11N is virtually folded back along the N-pole d-axis DN in each orthogonal plane and the N-pole front outer peripheral surface 29N-F is overlapped on the N-pole rear outer peripheral surface 29N-R, the N-pole front outer peripheral surface 29N-F has a small diameter outer peripheral surface 34 that is located more inward than the N-pole rear outer peripheral surface 29N-R in the radial direction of the rotor core 23, and the N-pole rear outer peripheral surface 29N-R does not have a portion that is located more inward than the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23, making it easy to obtain a shape.

[0073] 7 and 8, in the first embodiment, the front diameter change region A3-F located on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D is larger than the rear diameter change region A3-R located on the rear side of the rotation direction R with respect to the d-axis D. This makes it easy to obtain a shape in each magnetic pole outer peripheral surface 29 in which the gap formed within the range of the front outer peripheral surface 29-F gradually increases, and the rate at which the gap formed within the range of the rear outer peripheral surface 29-R gradually increases is smaller than that of the front outer peripheral surface 29-F.

[0074] For simplicity, the combination of radii of curvature forming the front diameter change region A3-F of the N pole front outer peripheral surface 29N-F and the combination of radii of curvature forming the rear diameter change region A3-R of the N pole rear outer peripheral surface 29N-R have been described as being equal. However, the combinations of radii of curvature of the front diameter change region A3-F and the rear diameter change region A3-R may be different. For example, the first radius of curvature r1-F of the front diameter change region A3-F (As3-F) may be different from the first radius of curvature r1-R of the rear diameter change region A3-R (As3-R). Similarly, the second radius of curvature r2-F (rs2-F) of the front diameter change region A3-F (As3-F) may be different from the second radius of curvature r2-R (rs2-R) of the rear diameter change region A3-R (As3-R).

[0075] (Inner surface shape of groove) As shown in FIG. 6 , in an orthogonal plane of the rotor core 23, the shape of the inner surface 16a of the groove portion 16 is asymmetric with respect to the q axis Q. Similarly, the shape of the inner surface 17a of the groove portion 17 is asymmetric with respect to the q axis Q. Furthermore, on the outer peripheral surface 27 of the rotor core 23, the groove portions 16 and 17 are alternately arranged along the circumferential direction of the rotor core 23. In the orthogonal plane, the shapes of the inner surfaces 16a of the groove portions 16 and the inner surfaces 17a of the groove portions 17 that are adjacent to each other in the circumferential direction of the rotor core 23 are different from each other. The shapes of the inner surfaces 16a, 17a of the groove portions 16, 17 are formed as a result of smoothly connecting the inner surfaces 16a, 17a with the diameter change region A3 of the outer peripheral surface 29 of each magnetic pole.

[0076] (shape of non-magnetic part) The two q-axis side non-magnetic portions 14, 15 of the S-pole magnetic pole portion 11S are formed asymmetrically with respect to the S-pole d-axis DS, which is the d-axis of the S-pole magnetic pole portion 11S. The two q-axis side non-magnetic portions 14, 15 of the N-pole magnetic pole portion 11N are formed asymmetrically with respect to the N-pole d-axis DN, which is the d-axis of the N-pole magnetic pole portion 11N. Furthermore, the two q-axis side non-magnetic portions 14, 15 of the N-pole magnetic pole portion 11N and the two q-axis side non-magnetic portions 14, 15 of the S-pole magnetic pole portion 11S are formed in shapes that do not match with each other when the N-pole magnetic pole portion 11N and the S-pole magnetic pole portion 11S are virtually rotated 360 / (2 m) degrees around the rotation center O of the rotor 21 so that they overlap.

[0077] Fig. 9 is a plan view showing magnetic field lines in Example 1. As shown in Fig. 9, in Example 1, two permanent magnets 13 (first magnet 13A and second magnet 13B) are arranged asymmetrically with respect to the d-axis D in each magnetic pole portion 11, thereby adjusting the path of magnetic flux passing through the magnetic pole outer circumferential surface 29 of the magnetic pole portion 11. As a result, in the rotor 21 of Example 1, magnetic flux that short-circuits through the flange portion 33 of the tooth portion 32 in the magnetic pole portions 11 adjacent to each other in the circumferential direction of the rotor core 23 without passing through an appropriate magnetic path is reduced, and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D in the magnetic pole portion 11 is greater than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D.

[0078] (Magnetization process) In the magnetizing process of the rotor 21, the magnetic material before being magnetized (the magnetic material that will become the permanent magnets 13 after magnetization) is embedded in the rotor core 23, and then the rotor 21 is attached to a magnetizing device (not shown). In this magnetizing process, for example, the magnetic flux of the magnetizing magnetic field passes through the magnetic pole portions 11 along the d-axis D, thereby manufacturing a rotor having permanent magnets 13 magnetized by the magnetizing magnetic field. Here, the magnetizing magnetic field refers to a magnetic field that is applied from the magnetizing device to the magnetic material (permanent magnets 13) in order to magnetize the magnetic material to make it a permanent magnet (i.e., to magnetize the magnetic material).

[0079] In the first embodiment, in the orthogonal plane of the rotor core 23, the two permanent magnets 13 (first magnet 13A and second magnet 13B) of the magnetic pole portion 11 have the same angle between their longitudinal directions and the d-axis D. Therefore, when a magnetizing magnetic field is applied along the d-axis D, the amount of magnetic flux of the magnetizing magnetic field passing through the magnetic material that becomes the permanent magnet 13 is equal for the two permanent magnets 13. As a result, it is possible to prevent a difference in the magnetization rate (a ratio indicating how much a material is magnetized when an external magnetic field H is applied (magnitude of magnetic moment density)) of the two permanent magnets 13. Therefore, it is possible to prevent a difference in the magnetization rate and demagnetization rate between the two permanent magnets 13 (first magnet 13A and second magnet 13B). As a result, it is possible to prevent problems such as an imbalance in the amount of magnetic flux between the two permanent magnets 13 and differences in durability.

[0080] (Comparison between Examples and Comparative Examples) FIG. 10 is a plan view showing magnetic field lines in an analytical model corresponding to the example (hereinafter, the analytical model of the example). The analytical model of the example is the same as Example 1 in that the two permanent magnets 13 in the magnetic pole portion 11 are arranged asymmetrically with respect to the d-axis D. However, for convenience, an analytical model is used in which the q-axis side nonmagnetic portions 14, 15 and the d-axis side nonmagnetic portion 19 are not provided. FIG. 11 is a plan view showing magnetic field lines in an analytical model corresponding to a comparative example (hereinafter, the analytical model of the comparative example). The analytical model of the comparative example differs from Example 1 in that the two permanent magnets 13 in the magnetic pole portion 11 are arranged symmetrically with respect to the d-axis D. Like the analytical model of the example, an analytical model is used in which the q-axis side nonmagnetic portions 14, 15 and the d-axis side nonmagnetic portion 19 are not provided. In the analytical model of the comparative example, the same members and parts as those in the analytical model of the example are designated by the same reference numerals as those in the example (the analytical model of the example).

[0081] 10 and 11, in each magnetic pole portion 11 in the analysis model of the example, the amount of magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D is increased compared to the analysis model of the comparative example. For example, in the analysis model of the comparative example shown in Fig. 11, the number of magnetic field lines that radially cross the tooth portion 32 that is located most forward in the rotation direction R of the rotor 21 among the three teeth portions 32 lined up in the circumferential direction and pass through the permanent magnet 13 (second magnet 13B) located on the rear side in the rotation direction R is four, whereas in the analysis model of the example shown in Fig. 10, the number of magnetic field lines that radially cross the tooth portion 32 that is located most forward in the rotation direction R of the rotor 21 among the three teeth portions 32 lined up in the circumferential direction and pass through the permanent magnet 13 (second magnet 13B) located on the rear side in the rotation direction R is increased to six. The reason for this difference is presumably that, in the analytical model of the example, the permanent magnet 13 (second magnet 13B) located on the rear side in the rotational direction R relative to the d-axis D is located closer to the magnetic pole outer peripheral surface 29 than the analytical model of the comparative example, so that the effective magnetic flux that crosses the tooth portion 32 and passes through the magnetic pole outer peripheral surface 29 passes more easily through the second magnet 13B than through the first magnet 13A. In this way, in each magnetic pole portion 11 of the example, the magnetic flux that short-circuits at magnetic pole portions 11 adjacent to each other in the circumferential direction of the rotor core 23 is reduced, reducing the effective magnetic flux that passes through the permanent magnet 13 (first magnet 13A) on the front side in the rotational direction R of the rotor 21 relative to the d-axis D and increasing the effective magnetic flux that passes through the permanent magnet 13 (second magnet 13B) on the rear side in the rotational direction R relative to the d-axis D.

[0082] (Movement of torque fluctuation peak) This section explains the shift of the peak of torque fluctuation depending on the position of the two permanent magnets 13 (first magnet 13A, second magnet 13B) arranged on either side of the d-axis D in the magnetic pole portion 11 of the rotor 21 of the embodiment. Here, one permanent magnet 13 arranged on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D is referred to as the first magnet 13A, and the other permanent magnet 13 arranged on the rear side of the rotation direction R with respect to the d-axis D is referred to as the second magnet 13B. FIG. 12 is a diagram for explaining the torque of the electric motor 6 of the embodiment, showing the fluctuation of torque with the rotation of the rotor 21. In FIG. 12, the vertical axis represents torque, and the horizontal axis represents electrical angle [°]. The direction of arrow a indicates the front side of the rotation direction R of the rotor 21.

[0083] In FIG. 12, the solid line RT indicates the fluctuation of the reluctance torque of the electric motor 1. The dashed line MT1 indicates the fluctuation of the magnet torque when permanent magnets arranged symmetrically with respect to the d-axis D are used, i.e., the magnet torque before the shift, and is the magnet torque in the comparative example. The dashed line MT2 indicates the fluctuation of the magnet torque when a first magnet is formed that is located forward in the rotation direction R of the rotor 21, i.e., the magnet torque after the shift, and is the magnet torque in the embodiment. The dashed line CT1 indicates the resultant torque before the shift, which is a combination of the reluctance torque (solid line RT) and the magnet torque before the shift (dashed line MT1). The thick line CT2 indicates the resultant torque before the shift, which is a combination of the reluctance torque (solid line RT) and the magnet torque after the shift (dashed line MT2), and is the resultant torque in the embodiment.

[0084] 12, in the embodiment, the peak of the magnet torque in the embodiment indicated by the dashed line MT2 is shifted forward in the rotation direction R of the rotor 21, and is shifted in a direction approaching the positive peak of the fluctuation of the reluctance torque indicated by the solid line RT. As a result, in the embodiment, the peak of the resultant torque indicated by the dashed line CT2 becomes larger than the peak of the resultant torque indicated by the dashed line CT1. As a result, the torque of the electric motor 1 can be increased.

[0085] (Effects of Example 1) As described above, in the rotor 21 of the first embodiment, the permanent magnets 13 provided in each magnetic pole portion 11 include a first magnet 13A arranged on one circumferential side of the rotor core 23 with respect to the d-axis D, and a second magnet 13B arranged on the other circumferential side of the rotor core 23 with respect to the d-axis D. In an orthogonal plane, when a first mechanical angle formed between the longitudinal direction of the first magnet 13A and the d-axis D on the outer circumferential side of the rotor core 23 is θ1 and a second mechanical angle formed between the longitudinal direction of the second magnet 13B and the d-axis D on the outer circumferential side of the rotor core 23 is θ2, the first magnet 13A and the second magnet 13B satisfy θ1 = θ2 < 90 degrees (Equation 1) and are arranged asymmetrically with respect to the d-axis D. This makes it possible to adjust the path of the magnetic flux passing through the magnetic pole outer peripheral surface 29, reducing the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on one side with respect to the d-axis D and increasing the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the other side with respect to the d-axis D, while suppressing differences in the magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B arranged on both sides of the d-axis D in the magnetic pole portion 11. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet) on one side with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D. As a result, the torque of the electric motor 1 can be increased and the quality of the electric motor 1 can be improved.

[0086] Furthermore, in the rotor 21 of the first embodiment, when the shortest distance between the first magnet 13A and the d-axis D is L1a and the shortest distance between the d-axis D and the second magnet 13B is L1b in an orthogonal plane, L1a ≠ L1b (Equation 2) is satisfied. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so that the path of the magnetic flux passing through the magnetic pole outer circumferential surface 29 can be adjusted, and the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on one side with respect to the d-axis D can be reduced and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the other side with respect to the d-axis D can be increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D.

[0087] Also, in the case of the rotor 21 of the first embodiment, in the orthogonal plane, when the first magnet 13A is arranged on the front side in the rotation direction R of the rotor core 23 with respect to the d-axis D, and the second magnet 13B is arranged on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D, the shortest distances L1a and L1b satisfy L1a < L1b ··· (Equation 3). Thereby, the magnetic flux passing through the first magnet 13A, which is the permanent magnet 13 on the front side in the rotation direction R of the rotor core 23 with respect to the d-axis D, can be reduced, and the magnetic flux passing through the second magnet 13B, which is the permanent magnet 13 on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D, can be increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side in the rotation direction R with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side in the rotation direction R with respect to the d-axis D.

[0088] Also, in the case of the rotor 21 of the first embodiment, in the orthogonal plane, when the shortest distance between the first magnet 13A and the rotation center O of the rotor 21 is L2a, and the shortest distance between the second magnet 13B and the rotation center O of the rotor 21 is L2b, L2a ≠ L2b ··· (Equation 4) is satisfied. Thereby, since the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, the path of the magnetic flux passing through the outer peripheral surface 29 of the magnetic pole can be adjusted, the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on one side with respect to the d-axis D can be reduced, and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the other side with respect to the d-axis D can be increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D.

[0089] In addition, in the rotor 21 of the first embodiment, in the orthogonal plane, when the first magnet 13A is disposed on the front side in the rotation direction R of the rotor core 23 with respect to the d-axis D and the second magnet 13B is disposed on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D, the shortest distances L2a and L2b satisfy L2a < L2b... (Equation 5). Thereby, the effective magnetic flux passing through the permanent magnet 13 (the first magnet 13A) on the front side in the rotation direction R of the rotor core 23 with respect to the d-axis D can be reduced, and the effective magnetic flux passing through the permanent magnet 13 (the second magnet 13B) on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D can be increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (the second magnet 13B) on the rear side in the rotation direction R with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (the first magnet 13A) on the front side in the rotation direction R with respect to the d-axis D.

[0090] In addition, in the rotor 21 of the first embodiment, the magnetic pole outer peripheral surface 29 of the rotor core 23 has a front side outer peripheral surface 29-F located on the front side in the rotation direction R of the rotor 21 with respect to the d-axis D and a rear side outer peripheral surface 29-R located on the rear side in the rotation direction R of the rotor 21 with respect to the d-axis D. When the magnetic pole portion 11 is virtually folded along the d-axis D in the orthogonal plane and the front side outer peripheral surface 29-F is overlapped with the rear side outer peripheral surface 29-R, the front side outer peripheral surface 29-F has a small diameter outer peripheral surface 34 located inside the rear side outer peripheral surface 29-R in the radial direction of the rotor core 23. Thereby, for example, when paying attention to a magnetic path in which the magnetic flux passing through the teeth portion 32 from the N-pole magnetic pole portion 11N does not pass through the yoke portion 31 but short-circuits to the adjacent S-pole magnetic pole portion 11S via the flange portion 33 in the central teeth portion 32 among the three teeth portions 32 arranged in the circumferential direction of the rotor core 23, the magnetic flux distribution is suppressed from becoming asymmetric with respect to the q-axis Q. For this reason, the magnetic flux density distribution when the above-described central teeth portion 32 is located on the q-axis Q can be made closer to an ideal sine wave. Therefore, the magnetic flux density distribution at the position of the gap (air gap) between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 can be made closer to a sine wave.

[0091] Hereinafter, Examples 2 and 3 will be described with reference to the drawings. In other examples, the same components as those in Example 1 are denoted by the same reference numerals as in Example 1, and the description thereof will be omitted. In Examples 2 and 3, the arrangements of the first magnet 13A and the second magnet 13B in the magnetic pole portion 11 are different from those in Example 1.

Example

[0092] FIG. 13 is a schematic diagram for explaining the arrangement of the permanent magnets 13 in the magnetic pole portion 11 in Example 2. As shown in FIG. 13, in the magnetic pole portion 11 of the rotor 51 in Example 2, the first magnet 13A is arranged on the front side in the rotational direction R of the rotor core 23 with respect to the d-axis D, and the second magnet 13B is arranged on the rear side in the rotational direction R with respect to the d-axis D. Similar to Example 1, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D while satisfying the first angle θ1 [degrees] and the second angle θ2 [degrees] formed with respect to the d-axis D, where θ1 = θ2 < 90 degrees... (Equation 1). [[ID=⑨]]

[0093] [[ID=⑩]] [[ID=⑪]]In the rotor 51 of Example 2, in the orthogonal plane, when the shortest distance between the first magnet 13A and the d-axis D is L1a [mm] and the shortest distance between this d-axis D and the second magnet 13B is L1b [mm], the shortest distances L1a and L1b are L1a < L1b... (Equation 3) is satisfied.

[0094] That is, the positions of the first magnet 13A and the second magnet 13B with respect to the d-axis D are different in the circumferential direction of the rotor core 23. In other words, the rotor 51 of Example 2 corresponds to an arrangement in which each of the first magnet 13A and the second magnet 13B arranged symmetrically with respect to the d-axis D in the orthogonal plane is shifted in position along the direction orthogonal to the d-axis D toward the rear side in the rotational direction R of the rotor core 23 with respect to the d-axis D.

[0095] (Effect of Example 2) As described above, in the rotor 51 of the second embodiment as well, since the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, the path of the magnetic flux passing through the outer peripheral surface 29 of the magnetic pole can be adjusted, and the effective magnetic flux passing through the permanent magnet 13 (the second magnet 13B) on one side with respect to the d-axis D can be made larger than the effective magnetic flux passing through the permanent magnet 13 (the first magnet 13A) on the other side with respect to the d-axis D. Also, in the second embodiment as well, similar to the first embodiment, by satisfying the formula 1 (θ1 = θ2 < 90 degrees) for the first angle θ1 of the first magnet 13A and the second angle θ2 of the second magnet 13B, it is possible to suppress the occurrence of a difference in magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B arranged on both sides of the d-axis D in the magnetic pole portion 11.

Embodiment

[0096] FIG. 14 is a schematic diagram for explaining the arrangement of the permanent magnets 13 in the magnetic pole portion 11 in the third embodiment. As shown in FIG. 14, in the magnetic pole portion 11 of the rotor 52 of the third embodiment, the first magnet 13A is arranged on the front side in the rotation direction R of the rotor core 23 with respect to the d-axis D, and the second magnet 13B is arranged on the rear side in the rotation direction R of the rotor core 23 with respect to the d-axis D. The first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D while satisfying the first angle θ1 [degrees] and the second angle θ2 [degrees] formed with respect to the d-axis D, θ1 = θ2 < 90 degrees... (Formula 1), similar to the first embodiment.

[0097] In the rotor 52 of the third embodiment, in the orthogonal plane, when the shortest distance between the first magnet 13A and the rotation center O of the rotor core 23 is L2a [mm] and the shortest distance between the second magnet 13B and the rotation center O of the rotor core 23 is L2b [mm], the shortest distances L2a and L2b satisfy L2a < L2b... (Formula 5) and satisfy it.

[0098] That is, the first magnet 13A and the second magnet 13B are differently arranged in the radial direction of the rotor core 23. In other words, the rotor 51 of the second embodiment corresponds to an arrangement in which, of the first magnet 13A and the second magnet 13B arranged symmetrically with respect to the d-axis D in an orthogonal plane, the second magnet 13B is shifted along the d-axis D toward the radial outside of the rotor core 23, i.e., toward the magnetic pole outer circumferential surface 29 of the rotor core 23.

[0099] (Effects of Example 3) As described above, in rotor 52 of Example 3 as well, first magnet 13A and second magnet 13B are arranged asymmetrically with respect to d-axis D, so that the path of the magnetic flux passing through magnetic pole outer peripheral surface 29 can be adjusted, and the effective magnetic flux passing through permanent magnet 13 (second magnet 13B) on one side with respect to d-axis D can be made larger than the effective magnetic flux passing through permanent magnet 13 (first magnet 13A) on the other side with respect to d-axis D. Also, in Example 3 as well, as in Example 1, by having first angle θ1 of first magnet 13A and second angle θ2 of second magnet 13B satisfy formula 1 (θ1 = θ2 < 90 degrees), it is possible to suppress differences in magnetization rate and demagnetization rate between first magnet 13A and second magnet 13B arranged on both sides of d-axis D in magnetic pole portion 11.

[0100] Below, we will explain modified examples 1 to 3, which differ from Example 1 in the presence or absence of a nonmagnetic portion in the magnetic pole portion 11 of the rotor core 23. In modified examples 1 to 3, the first magnet 13A and the second magnet 13B of the magnetic pole portion 11 also satisfy the above-mentioned formula 6 (a>b), as in Example 1, and are arranged asymmetrically with respect to the d-axis D.

[0101] (Variation 1) Fig. 15 is a plan view showing a magnetic pole portion 11 in Modification 1. As shown in Fig. 15, each magnetic pole portion 11 of a rotor 53A in Modification 1 has a front-side non-magnetic portion 20 formed separately from the magnet embedding hole 12 at a position forward in the rotation direction R of the rotor 21 (rotation direction R of the rotor core 23) with respect to the d-axis D, and a rear-side non-magnetic portion 30 formed separately from the magnet embedding hole 12 at a position forward in the rotation direction R of the rotor 21 with respect to the d-axis D. The front-side non-magnetic portion 20 and the rear-side non-magnetic portion 30 are through holes that penetrate the rotor core 23 along the rotation center line, and are gaps formed in the magnetic pole portion 11.

[0102] The front-side non-magnetic portion 20 is formed as an elongated hole extending from the first magnet 13A side toward the d-axis D side. The rear-side non-magnetic portion 30 is formed as an elongated hole extending from the second magnet 13B side toward the d-axis D side. Similar to the q-axis side non-magnetic portions 14, 15 and d-axis side non-magnetic portion 19 described above, the front-side non-magnetic portion 20 and the rear-side non-magnetic portion 30 prevent magnetic flux from short-circuiting between a pair of magnetic pole portions 11 adjacent to each other in the circumferential direction of the rotor core 23 and the flange portion 33 of one tooth portion 32. Therefore, the front-side non-magnetic portion 20 and the rear-side non-magnetic portion 30 increase the magnetic flux circulating between the pair of magnetic pole portions 11 adjacent to each other in the circumferential direction of the rotor core 23, the pair of teeth portions 32 adjacent to each other in the circumferential direction of the rotor core 23, and the yoke portion 31 connecting the pair of teeth portions 32.

[0103] FIG. 16 is a plan view showing magnetic lines of force in Modification 1. As shown in FIG. 16, in each magnetic pole portion 11 of Modification 1, the path of magnetic flux on the front side of the direction of rotation R of the rotor 21 relative to the d-axis D is changed by the front-side nonmagnetic portion 20 so that it passes through the d-axis D side. Therefore, the front-side nonmagnetic portion 20 can reduce the magnetic flux passing through the q-axis Q side in front of the magnetic pole portion 11 and increase the amount of magnetic flux passing through the d-axis D side in front of the magnetic pole portion 11. Similarly, in each magnetic pole portion 11 of Modification 1, the path of magnetic flux on the rear side of the direction of rotation R of the rotor 21 relative to the d-axis D is changed by the rear-side nonmagnetic portion 30 so that it passes through the d-axis D side. Therefore, the rear-side nonmagnetic portion 30 can reduce the magnetic flux passing through the q-axis Q side in the rear of the magnetic pole portion 11 and increase the amount of magnetic flux passing through the d-axis D side in the rear of the magnetic pole portion 11.

[0104] In Modification 1, as in Example 1, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which makes it possible to adjust the path of the magnetic flux passing through the magnetic pole outer surface 29, making the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D greater than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D, and suppressing differences in the magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B arranged on both sides of the d-axis D in the magnetic pole portion 11. Note that Modification 1 has a front non-magnetic portion 20 and a rear non-magnetic portion 30, but it is also possible to have only one of the non-magnetic portions, and the effect of restricting short-circuiting of the magnetic flux can be obtained as described above.

[0105] (Variation 2) Fig. 17 is a plan view showing a magnetic pole portion 11 in Modification 2. As shown in Fig. 17, each magnetic pole portion 11 of a rotor 53B in Modification 2 differs from that of Example 1 only in that the q-axis side nonmagnetic portions 14, 15 in Example 1 are not provided.

[0106] Fig. 18 is a plan view showing magnetic field lines in Modification 2. As shown in Fig. 18, in the magnetic pole portion 11 of Modification 2 as well, the effective magnetic fluxes passing through the two permanent magnets 13 included in one magnetic pole portion 11 are different from each other.

[0107] In variant example 2, as in example 1, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which makes it possible to adjust the path of the magnetic flux passing through the magnetic pole outer surface 29, making the effective magnetic flux passing through the permanent magnet 13 on one side with respect to the d-axis D greater than the effective magnetic flux passing through the permanent magnet 13 on the other side with respect to the d-axis D, and suppressing differences in the magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B arranged on both sides of the d-axis D in the magnetic pole portion 11.

[0108] (Variation 3) Fig. 19 is a plan view showing a magnetic pole portion 11 in Modification 3. As shown in Fig. 19, each magnetic pole portion 11 of a rotor 53C in Modification 3 differs from that of Example 1 only in that the d-axis side nonmagnetic portion 19 in Example 1 is not provided.

[0109] Fig. 20 is a plan view showing magnetic field lines in Modification 3. As shown in Fig. 20, in the magnetic pole portion 11 of Modification 2 as well, the effective magnetic fluxes passing through the two permanent magnets 13 included in one magnetic pole portion 11 are different from each other.

[0110] In variant example 3, as in example 1, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which makes it possible to adjust the path of the magnetic flux passing through the magnetic pole outer surface 29, making the effective magnetic flux passing through the permanent magnet 13 on one side with respect to the d-axis D greater than the effective magnetic flux passing through the permanent magnet 13 on the other side with respect to the d-axis D, and suppressing differences in the magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B arranged on both sides of the d-axis D in the magnetic pole portion 11.

[0111] The number of permanent magnets 13 in each magnetic pole portion 11 of the rotor core 23 is not limited to two. Below, Modifications 4 to 6 will be described, in which the number of permanent magnets 13 in the magnetic pole portion 11 of the rotor core 23 is different from that of Example 1. Note that, although non-magnetic portions are not shown in the figures illustrating Modifications 4 to 6, non-magnetic portions may be formed continuously to the ends of the magnet embedding holes 12 of the permanent magnets 13, similar to the q-axis side non-magnetic portions 14, 15 and the d-axis side non-magnetic portion 19 in Example 1. In Modifications 4 to 6, the first magnets 13A and second magnets 13B of the magnetic pole portion 11 also satisfy the above-mentioned formula 6 (a>b), similar to Example 1, and are arranged asymmetrically with respect to the d-axis D.

[0112] (Variation 4) Fig. 21 is a plan view showing a magnetic pole portion 11 in Modification 4. As shown in Fig. 21, each magnetic pole portion 11 of a rotor 53D in Modification 4 has a first magnet 13A and a second magnet 13B that are asymmetrically arranged in an orthogonal plane, similar to Example 1, and a third magnet 13C that is arranged between the ends of the first magnet 13A and the second magnet 13B that are adjacent to each other. For example, the plate-shaped third magnet 13C has a longitudinal direction that is perpendicular to the d-axis D and is arranged symmetrically with respect to the d-axis D.

[0113] (Variation 5) Fig. 22 is a plan view showing a magnetic pole portion 11 in Modification 5. As shown in Fig. 22, each magnetic pole portion 11 of a rotor 53E in Modification 5 has, in an orthogonal plane, a first magnet 13A and a second magnet 13B that are asymmetrically arranged as in Example 1, and a third magnet 13C that is arranged radially outward of the rotor core 23 with respect to the first magnet 13A and the second magnet 13B, i.e., on the magnetic pole outer peripheral surface 29 side. For example, the plate-shaped third magnet 13C has a longitudinal direction that is perpendicular to the d-axis D and is arranged symmetrically with respect to the d-axis D.

[0114] (Variation 6) Fig. 23 is a plan view showing a magnetic pole portion 11 in Modification 6. As shown in Fig. 23, each magnetic pole portion 11 of a rotor 53F in Modification 6 has, in an orthogonal plane, a first magnet 13A and a second magnet 13B that are asymmetrically arranged in the same manner as in Example 1, and a third magnet 13C and a fourth magnet 13D that are arranged radially outward of the rotor core 23 relative to the first magnet 13A and the second magnet 13B, i.e., on the magnetic pole outer circumferential surface 29 side. Like the first magnet 13A and the second magnet 13B, the third magnet 13C and the fourth magnet 13D satisfy the above-described formula 6 (a>b) and are arranged asymmetrically with respect to the d-axis D.

[0115] Example 4 24 is a plan view showing the magnetic pole portion 11 in Example 4. Example 4 differs from Example 1 in that the positional relationship between the first magnet 13A and the second magnet 13B with respect to the d-axis D is reversed. In Example 4, the following relationship holds between the output P [W], rotation speed Nr [rpm], and torque T [N m] of the electric motor, with k being the proportionality constant. P = k × Nr × T = const. As is clear from this relational expression, when the torque T decreases, the rotation speed Nr increases. Conversely, when the rotation speed Nr decreases, the torque T increases. That is, compared to Example 1, which can increase the torque T by decreasing the rotation speed Nr by satisfying Expression 3 or Expression 5, Example 4 can increase the rotation speed Nr by decreasing the torque T. [Explanation of symbols]

[0116] 1 electric motor 3 shafts 11 Magnetic pole part 11N N pole magnetic pole part 11S S pole magnetic pole part 13(13a~13f) Permanent magnet 13A First magnet 13B Second magnet 16, 17 Groove 21 rotor 22 Stator 23 rotor core 24 stator core 27 Outer surface 29 Magnetic pole outer surface 29-F Front outer circumferential surface 29-R Rear outer peripheral surface 31 York 32 Teeth 51, 52, 53A~53F rotors 101 Compressor 102 Container 105 Compression section θ1 1st angle θ2 2nd angle A1 Groove area A2 constant diameter area A3 Diameter change area C1, C2 corner D d axis L1a, L1b, L2a, L2b Shortest distance O Center of rotation Q q axis R Rotation direction

Claims

1. a rotor core having a plurality of magnetic pole portions provided with permanent magnets arranged along a circumferential direction; When a straight line connecting the center of the magnetic pole portion in the circumferential direction and the center of rotation of the rotor core is defined as a d-axis in a plane perpendicular to the rotation center line of the rotor core, the permanent magnets provided in each magnetic pole portion include a first magnet arranged on one side in the circumferential direction with respect to the d axis, and a second magnet arranged on the other side in the circumferential direction with respect to the d axis, In the plane, when a first angle formed by a longitudinal direction of the first magnet and the d-axis on the outer periphery of the rotor core is defined as θ1 and a second angle formed by a longitudinal direction of the second magnet and the d-axis on the outer periphery is defined as θ2, the first magnet and the second magnet satisfy θ1 = θ2 < 90 degrees and are arranged asymmetrically with respect to the d-axis, In the plane, one end of the first magnet on the d-axis side in the longitudinal direction is located radially inward of the rotor core with respect to the other end of the first magnet in the longitudinal direction, In the plane, one end of the second magnet on the d-axis side in the longitudinal direction is located radially inward of the other end of the second magnet in the longitudinal direction, In the plane, when the shortest distance between the first magnet and the d axis is L1a and the shortest distance between the d axis and the second magnet is L1b, A rotor that satisfies L1a≠L1b.

2. When a line connecting the center between the magnetic pole portions adjacent to each other in the circumferential direction and the center of rotation is defined as a q-axis in the plane, the distance between the magnetic pole outer peripheral surface formed on the outer peripheral surface of the magnetic pole portion and the center of rotation gradually decreases from the d-axis to the q-axis. The rotor of claim 1 .

3. In the plane, the first magnet and the second magnet have the same shape and size. The rotor of claim 1 .

4. the first magnet is disposed forward of the d-axis in the rotation direction of the rotor core, the second magnet is disposed on the rear side of the d axis in the rotation direction, The shortest distances L1a and L1b are L1a<L1b is satisfied. The rotor of claim 1 .

5. In the plane, when the shortest distance between the first magnet and the rotation center is L2a and the shortest distance between the second magnet and the rotation center is L2b, L2a≠L2b is satisfied. The rotor of claim 1 .

6. the first magnet is disposed forward of the d-axis in the rotation direction of the rotor core, the second magnet is disposed on the rear side of the d axis in the rotation direction, The shortest distances L2a and L2b are L2a<L2b is satisfied. The rotor according to claim 5 .

7. a magnetic pole outer peripheral surface formed on the outer peripheral surface of each magnetic pole portion has a front outer peripheral surface located on the front side of the rotation direction with respect to the d axis, and a rear outer peripheral surface located on the rear side of the rotation direction with respect to the d axis, When the magnetic pole portion is virtually folded back along the d axis on the plane and the front outer peripheral surface is superimposed on the rear outer peripheral surface, the front outer peripheral surface has a small diameter outer peripheral surface located more inward than the rear outer peripheral surface in the radial direction of the rotor core, A rotor according to claim 4 or 6.

8. a groove portion recessed in the outer peripheral surface of the rotor core in a radial direction of the rotor core is formed along the rotation center line between the magnetic pole portions adjacent in the circumferential direction, When a straight line connecting a center between the magnetic pole portions adjacent to each other in the circumferential direction and the center of rotation is defined as a q-axis in the plane, the outer circumferential surface of the rotor core has a groove region in which the groove is formed so that the q-axis passes through the groove, The magnetic pole outer peripheral surface formed on the outer peripheral surface of each magnetic pole portion has a constant diameter region formed at a position through which the d axis passes and whose distance from the rotation center is constant, and a diameter changing region formed between the groove region and the constant diameter region and whose distance from the rotation center changes. A rotor according to claim 4 or 6.

9. A rotor core having a plurality of magnetic pole portions provided with permanent magnets arranged along a circumferential direction, When a straight line connecting the center of the magnetic pole portion in the circumferential direction and the center of rotation of the rotor core is defined as a d-axis in a plane perpendicular to the rotation center line of the rotor core, the permanent magnets provided in each magnetic pole portion include a first magnet arranged on one side in the circumferential direction with respect to the d axis, and a second magnet arranged on the other side in the circumferential direction with respect to the d axis, In the plane, when a first angle formed by a longitudinal direction of the first magnet and the d-axis on the outer periphery of the rotor core is defined as θ1 and a second angle formed by a longitudinal direction of the second magnet and the d-axis on the outer periphery is defined as θ2, the first magnet and the second magnet satisfy θ1 = θ2 < 90 degrees and are arranged asymmetrically with respect to the d-axis, In the plane, one end of the first magnet on the d-axis side in the longitudinal direction is located radially inward of the rotor core with respect to the other end of the first magnet in the longitudinal direction, In the plane, one end of the second magnet on the d-axis side in the longitudinal direction is located radially inward of the other end of the second magnet in the longitudinal direction, the first magnet is disposed forward of the d-axis in the rotation direction of the rotor core, the second magnet is disposed on the rear side of the d axis in the rotation direction, In the plane, when the shortest distance between the first magnet and the rotation center is L2a and the shortest distance between the second magnet and the rotation center is L2b, A rotor that satisfies L2a<L2b.

10. The rotor according to claim 1; a stator having a plurality of teeth arranged on an outer periphery of the rotor; An electric motor comprising:

11. When m is a natural number, the number of the plurality of magnetic pole portions is 2m, and the number of the plurality of tooth portions is 3m.

11. The electric motor according to claim 10.

12. an electric motor according to claim 10 or 11; a compression section driven by the electric motor; a container that houses the electric motor and the compression unit; A compressor comprising:

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