Electric motors and compressors

Abstract

This reduces harmonic components superimposed on the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotor. [Solution] The electric motor includes a rotor having a rotor core in which permanent magnets are embedded in magnet embedding holes and a plurality of magnetic pole portions are arranged circumferentially, and a stator having a plurality of teeth arranged on the outer periphery of the rotor and an annular yoke portion connecting the plurality of teeth. In a plane perpendicular to the rotational centerline of the rotor and passing through the rotor core, when a line connecting the center of rotation of the rotor to the center of rotation of the rotor is defined as the d-axis and a line connecting the center of rotation of the rotor to the center of rotation of the rotor is defined as the q-axis, the magnetic pole portions are provided with rearward non-magnetic portions in the direction of rotation of the rotor at positions rearward of the d-axis, and the rearward non-magnetic portions prevent magnetic flux from short-circuiting between a pair of circumferentially adjacent magnetic pole portions of the rotor core and one of the teeth.

Description

[Technical Field]

[0001] The present invention relates to 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] Related technologies include an electric motor that reduces torque ripple by changing the size of the air gap between the outer surface of the rotor core and the inner surface of the teeth in the circumferential direction of the rotating rotor, thereby bringing the magnetic flux density distribution in the air gap along the circumferential direction closer to a sine wave (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5321451 Specification [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-260972 Summary of the Invention [Problem to be solved by the invention]

[0005] During rotation of such an electric motor, within the range of adjacent north and south poles of the rotor in the circumferential direction, for example, three teeth aligned circumferentially of the rotor may face the outer circumferential surface of the rotor. Here, as an example, we focus on the magnetic path that circulates between the stator and the rotor, when the central tooth of the three teeth is located on the q-axis, which is the line connecting the center between the adjacent magnetic poles and the center of rotation of the rotor. In this case, two types of magnetic paths are generated: a magnetic path in which the magnetic flux short-circuits from the north pole to the south pole via only the inner end (flange) of the teeth without passing through the yoke of the stator; and a proper magnetic path that runs from the north pole to the tooth in the radial direction of the rotor, passes through the yoke, passes through the adjacent tooth, and then reaches the south pole. In this way, in the central teeth, magnetic flux leaks into the magnetic path where the magnetic flux is short-circuited without passing through the proper magnetic path (hereinafter also referred to as leakage magnetic flux), causing losses, and the magnetic flux density distribution in the gap between the rotor and stator does not become sinusoidal, causing the waveform to become distorted, resulting in the generation of harmonic magnetic flux containing higher-order components.The fact that the waveform of the magnetic flux density distribution is distorted and not sinusoidal indicates that the magnetic flux density distribution contains harmonic components.

[0006] As a result, due to the influence of harmonic magnetic flux, high-frequency components that are integer multiples of the operating frequency are superimposed on the electromagnetic force acting between the rotor and stator, and these high-frequency components of the electromagnetic force resonate with the natural frequency of the stator, resulting in increased vibration of the electric motor.In particular, in an electric motor, the amount of magnetic flux increases when the magnetic torque of the permanent magnet is increased, which also increases the amount of leakage magnetic flux mentioned above, making it difficult to make the magnetic flux density distribution in the gap between the rotor and stator in the circumferential direction of the rotating rotor approach a sine wave, resulting in increased vibration of the electric motor.

[0007] The disclosed technology has been developed in consideration of the above, and aims to provide an electric motor and a compressor that can reduce harmonic components superimposed on the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotor. [Means for solving the problem]

[0008] One aspect of the electric motor disclosed in the present application includes a rotor having a rotor core in which permanent magnets are embedded in magnet embedding holes and a plurality of magnetic pole portions are arranged along the circumferential direction, and a stator having a plurality of teeth arranged on the outer periphery of the rotor and an annular yoke portion connecting the plurality of teeth. In a plane perpendicular to the rotation centerline of the rotor and passing through the rotor core, a line connecting the center of rotation of the rotor to the center of rotation of the rotor is defined as the d-axis, and a line connecting the center between adjacent magnetic pole portions in the circumferential direction of the rotor core to the center of rotation of the rotor is defined as the q-axis. In this case, in the plane, the magnetic pole portions are provided with rear-side non-magnetic portions at positions rearward of the d-axis in the direction of rotation of the rotor, and the rear-side non-magnetic portions are defined as follows: It is formed separately from the magnet embedding hole, This prevents magnetic flux from short-circuiting between a pair of magnetic pole portions adjacent to each other in the circumferential direction of the rotor core and one tooth portion. The magnetic pole portion is provided with only a rear non-magnetic portion as a non-magnetic portion provided separately from the magnet embedding hole. [Effects of the Invention]

[0009] According to one aspect of the rotary compressor disclosed in the present application, it is possible to reduce harmonic components superimposed on the magnetic flux density distribution in the gap between the rotor and the stator in the circumferential direction of the rotor. [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 in 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 an enlarged view showing the outer circumferential surfaces of the north and south poles of the rotor core in the first embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the outer circumferential surface of each magnetic pole portion of the rotor core in the first embodiment. [Figure 7]FIG. 7 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 8] FIG. 8 is a plan view showing magnetic lines of force in the first embodiment. [Figure 9] FIG. 9 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor in the first embodiment. [Figure 10] FIG. 10 is a plan view showing magnetic field lines in a comparative example. [Figure 11] FIG. 11 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor in the comparative example. [Figure 12] FIG. 12 is a plan view showing a rotor core of the second embodiment. [Figure 13] FIG. 13 is a plan view showing magnetic lines of force in the second embodiment. [Figure 14] FIG. 14 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor in the second embodiment. [Figure 15] FIG. 15 is a plan view illustrating a main part of a rotor core according to a third embodiment. [Figure 16] FIG. 16 is a plan view showing magnetic lines of force in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the electric motor and compressor disclosed in the present application will be described in detail with reference to the drawings. However, the 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 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 of rotation O 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 rotation between adjacent 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 substantially V-shape on an orthogonal plane. Note that Example 1 does not limit the number or arrangement of the permanent magnets 13 in each magnetic pole portion 11.

[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 14 (14a to 14f), 15 (15a to 15f) 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 two q-axis side non-magnetic portions 14, 15 formed in each magnetic pole portion 11, the q-axis side non-magnetic portion located on the front side in the rotational direction R of the rotor 21 is referred to as the q-axis side first non-magnetic portion 14 (14a to 14f), and the q-axis side non-magnetic portion located on the rear side in the rotational direction R is referred to as the q-axis side second non-magnetic portion 15 (15a to 15f). In each magnetic pole portion 11, the q-axis side non-magnetic portions (q-axis side first non-magnetic portion 14, q-axis side second non-magnetic portion 15) are formed to extend 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 radial outside 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 continuously so as to connect 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 rotation 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 spaces.

[0027] Each magnetic pole portion 11 is provided with 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 (rotation direction R of the rotor core 23) with respect to the d-axis D. In other words, each magnetic pole portion 11 is provided with a rear-side non-magnetic portion 30 formed separately from the q-axis non-magnetic portion 15 at a position forward in the rotation direction R of the rotor 21 with respect to the d-axis D. By forming the rear-side non-magnetic portion 30 separately from the magnet embedding hole 12 in this manner, a decrease in the mechanical strength of the rotor core 23 around the magnet embedding hole 12 is suppressed. The rear-side non-magnetic portion 30 is a through-hole that penetrates the rotor core 23 along the rotation centerline and is a space formed in the magnetic pole portion 11. Details of the rear-side non-magnetic portion 30 will be described later.

[0028] 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.

[0029] (Characteristic structure of the rotor core) Next, a description will be given of the characteristic structure of rotor core 23 in Example 1. The characteristics of Example 1 include rear nonmagnetic portion 30 of each magnetic pole portion 11 and the shape of outer circumferential surface 27 of rotor core 23.

[0030] (Shape of rear non-magnetic part) As shown in FIG. 4 , each magnetic pole portion 11 is provided with only a rear-side non-magnetic portion 30 as a non-magnetic portion provided separately from the magnet embedding hole 12. Similar to the q-axis side non-magnetic portions 14 and 15 and the d-axis side non-magnetic portion 19 described above, the rear-side non-magnetic portion 30 prevents magnetic flux from short-circuiting between a pair of circumferentially adjacent magnetic pole portions 11 of the rotor core 23 and the flange portion 33 of one tooth portion 32. Note that the total amount of magnetic flux, including the magnetic flux passing through the short-circuited magnetic path (leakage magnetic flux) and the magnetic flux passing through the proper magnetic path, can be considered to be constant. Therefore, the rear-side non-magnetic portion 30 reduces the magnetic flux passing through the short-circuited magnetic path described above (leakage magnetic flux), thereby increasing the magnetic flux passing through the proper magnetic path circulating between the pair of circumferentially adjacent magnetic pole portions 11 of the rotor core 23, the pair of circumferentially adjacent teeth portions 32 of the rotor core 23, and the yoke portion 31 connecting the pair of teeth portions 32.

[0031] Specifically, the rear non-magnetic portion 30 prevents the magnetic flux from short-circuiting as described above when the q-axis Q of the rotor 21 coincides with the center of the width direction of one of the teeth 32 during rotation of the rotor 21. The width direction of the teeth 32 here refers to a direction perpendicular to the radial direction of the stator 22 (the radial direction of the rotor 21). The center of the width direction of the teeth 32 is located on a straight line along the radial direction of the stator 22.

[0032] The rear-side non-magnetic portion 30 is formed over a range of 30 degrees or more and 90 degrees or less, where the q-axis Q located on the rear side of the rotation direction R of the rotor 21 relative to the magnetic pole portion 11 is defined as 0 degrees in electrical angle, and the front side of the rotation direction R of the rotor 21 is defined as a positive electrical angle. As a result, the rear-side non-magnetic portion 30 can block magnetic flux passing through a magnetic pole outer peripheral surface 29 (described later) which is the side surface on the outer periphery of the magnetic pole portion 11, over a range of 30 degrees or more and 90 degrees or less in electrical angle.

[0033] To rephrase the above-mentioned electrical angle in terms of mechanical angle, when the number of magnetic pole portions 11 is 2m, the rear non-magnetic portion 30 is formed over a range of (360 / 2m) × (1 / 6) degrees or more and (360 / 2m) × (3 / 6) degrees or less in the mechanical angle of the circumferential range between adjacent magnetic pole portions 11 (the range of one pole pair described below), when the q-axis Q located rearward of the rear magnetic pole portion 11 in the rotational direction R is set to 0 degrees.

[0034] The rear-side non-magnetic portion 30 has a first portion 30a extending from the magnet embedding hole 12 toward the magnetic pole outer peripheral surface 29 described below, and a second portion 30b formed continuously with the first portion 30a and extending toward the d-axis D. For example, the rear-side non-magnetic portion 30 is formed such that the width dimension along the short side of the first portion 30a and the width dimension along the short side of the second portion 30b are equal, and the second portion 30b is formed in the shape of an elongated hole bent relative to the first portion 30a.

[0035] In an orthogonal plane, the rear-side nonmagnetic portion 30 is disposed such that a center line 30c of the first portion 30a, which extends in the direction in which the first portion 30a extends, intersects with the permanent magnet 13. Here, the center line 30c of the first portion 30a is a straight line that passes through the center of the first portion 30a in the width direction, which is the short side direction, and extends in the longitudinal direction of the first portion 30a. By disposing the rear-side nonmagnetic portion 30 in this manner, the rear-side nonmagnetic portion 30 is more likely to block the path of magnetic flux that attempts to pass through the rear-side nonmagnetic portion 30. As a result, it is possible to prevent the magnetic flux that passes through the permanent magnet 13 from passing through the inner peripheral end portion (flange portion 33) of the tooth portion 32 without passing through the yoke portion 31 and returning to the permanent magnet 13, thereby enhancing the effect of restricting the short circuit of magnetic flux described above. In addition, since the center line 30c of the first portion 30a is arranged to intersect with the permanent magnet 13, a larger thickness can be ensured between the rear non-magnetic portion 30 and the magnetic pole outer surface 29 compared to when the center line 30a of the first portion 30a does not intersect with the permanent magnet 13 (for example, when the center line 30c of the first portion 30a extends in a direction along the center line 30d of the second portion 30b), thereby preventing a decrease in the mechanical strength around the rear non-magnetic portion 30 and the q-axis non-magnetic portion 15 in the rotor core 23.

[0036] In the rear-side nonmagnetic portion 30, the length K2 of the second portion 30b extending toward the d-axis D is shorter than the length K1 of the first portion 30a extending toward the magnetic pole outer peripheral surface 29. This ensures a sufficient length of extension of the rear-side nonmagnetic portion 30 in the circumferential direction of the rotor 21, thereby enhancing the effect of preventing the occurrence of short circuits in the magnetic flux. Here, the length K1 of the first portion 30a is, for example, the length on the center line 30c of the first portion 30a along the direction in which the first portion 30a extends. Similarly, the length K2 of the second portion 30b is, for example, the length on the center line 30d of the second portion 30b along the direction in which the second portion 30b extends.

[0037] The rear-side non-magnetic portion 30 is disposed radially inward of the q-axis side second non-magnetic portion 15 in the radial direction of the rotor core 23. This prevents the rear-side non-magnetic portion 30 from being too close to the q-axis side second non-magnetic portion 15. As a result, a large thickness can be ensured between the rear-side non-magnetic portion 30 and the q-axis side second non-magnetic portion 15, which prevents a decrease in the mechanical strength of the rotor core 23 around the rear-side non-magnetic portion 30 and the q-axis side non-magnetic portion 15.

[0038] In addition, in the first embodiment, the rear non-magnetic portion 30 is arranged in the magnetic pole portion 11 only on the rear side in the rotation direction R of the rotor 21 with respect to the d-axis D. This makes it easy to realize a cross-sectional shape of the magnetic pole portion 11 in an orthogonal plane that is asymmetric with respect to the d-axis D.

[0039] (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.

[0040] 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 the ends. 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.

[0041] 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.

[0042] FIG. 5 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 5 , 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 in the second embodiment 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. The virtually rotated magnetic pole may be either the N-pole magnetic pole portion 11N or the S-pole magnetic pole portion 11S. The rotation direction 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.

[0043] 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.

[0044] 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.

[0045] Note that 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 Example 2, 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.

[0046] (Shape of the outer surface of the magnetic pole) Fig. 6 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. 7 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.

[0047] As shown in Figures 6 and 7, 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.

[0048] 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.

[0049] (N pole outer surface shape) Specifically, as shown in Figure 6, 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.

[0050] FIG. 7 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 will be described. As shown in FIG. 7, 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).

[0051] (Shape of the outer surface of the S pole) Also, similar to the N-pole outer surface 29N described above, as shown in Figure 6, 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.

[0052] A case where the S-pole magnetic pole portion 11S is virtually folded back will be described. As shown in Fig. 7, 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).

[0053] (Relationship between the outer surface of the north pole and the outer surface of the south pole) Also, as shown in Figures 4 and 5, 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.

[0054] 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 FIGS. 4 and 5) 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).

[0055] 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).

[0056] 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.

[0057] 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 5).

[0058] 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 FIGS. 4 and 5) 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).

[0059] 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).

[0060] 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.

[0061] 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 of the rotor core 23, each of the magnetic pole outer peripheral surfaces 29 of the rotor core 23 has a maximum outer diameter L, which is the distance (radius) from the rotation center O of the rotor 21 at a position on the d-axis D, as shown in FIG. 4. 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 have the same distance from the rotation center O, i.e., the same outer diameter L, at a position on the d-axis D.

[0062] In addition, in Example 1, the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 is formed in a shape asymmetric with respect to the d-axis D in the orthogonal plane, so that groove portions 16 and groove portions 17 having different recess shapes are alternately arranged in the circumferential direction of the rotor core 23. Similarly, in Example 1, the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 is formed in a shape asymmetric with respect to the d-axis D in the orthogonal plane, so that the q-axis side non-magnetic portion 14 on the front side in the rotation direction R of the rotor 21 and the q-axis side non-magnetic portion 15 on the rear side have different shapes.

[0063] In addition, in Example 1, in the magnetic pole portion 11, the rear non-magnetic portion 30 is arranged only on the rear side of the rotation direction R of the rotor 21 relative to the d-axis D, the q-axis side non-magnetic portion 14 on the front side of the rotation direction R of the rotor 21 and the q-axis side non-magnetic portion 15 on the rear side have different shapes in the orthogonal plane, and the magnetic pole outer surface 29 is formed in a shape asymmetric with respect to the d-axis D, so that the cross-sectional shape of the magnetic pole portion 11 in the orthogonal plane is a shape asymmetric with respect to the d-axis D.

[0064] 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.

[0065] 4 and 6, 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 6, 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.

[0070] 6, 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.

[0071] 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).

[0072] (Inner surface shape of groove) As shown in FIG. 4 , in an orthogonal plane of the rotor core 23, the shape of the inner surface 16a of the groove portion 16 is formed asymmetrically with respect to the q axis Q. Similarly, the shape of the inner surface 17a of the groove portion 17 is formed asymmetrically with respect to the q axis Q. Furthermore, on the outer peripheral surface 27 of the rotor core 23, the groove portions 16 and the groove portions 17 are arranged alternately 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.

[0073] (shape of non-magnetic part on q-axis side) 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.

[0074] (Comparison between Example 1 and Comparative Example) FIG. 8 is a plan view showing magnetic lines of force in Example 1. FIG. 9 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor 21 in Example 1. FIG. 10 is a plan view showing magnetic lines of force in a comparative example. In the comparative example, the same members and parts as in Example 1 are designated by the same reference numerals. FIG. 11 is a diagram showing the magnetic flux density distribution in the circumferential direction of the rotor in the comparative example. In FIGS. 9 and 11, the vertical axis represents magnetic flux density [T] and the horizontal axis represents electrical angle [degrees (deg)]. In FIG. 9, the solid line represents a sine wave, and the dashed line represents Example 1. In FIG. 11, the solid line represents a sine wave, and the dashed line represents the comparative example. The comparative example has the same structure as Example 1, except that it does not have a rear-side nonmagnetic portion 30.

[0075] 8 and 10, in each magnetic pole portion 11 of the first embodiment, the path of the 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 non-magnetic portion 30 so that it passes through the d-axis D side. Therefore, the rear-side non-magnetic portion 30 serves to reduce the amount of magnetic flux passing through the q-axis Q side behind the magnetic pole portion 11 and to increase the amount of magnetic flux passing through the d-axis D side behind the magnetic pole portion 11 accordingly. In other words, the rear-side non-magnetic portion 30 functions to concentrate the path of the magnetic flux on the rear side of the direction of rotation R of the rotor 21 relative to the d-axis D toward the d-axis D side. Therefore, in Example 1, compared to the comparative example, the occurrence of a short-circuiting magnetic path in which magnetic flux passing through permanent magnet 13 returns to permanent magnet 13 via the inner peripheral end (flange portion 33) of tooth portion 32 without passing through yoke portion 31 is suppressed, and the magnetic flux passing through a proper magnetic path in which magnetic flux passes from permanent magnet 13 longitudinally through tooth portion 32 in the radial direction of rotor 21, then passes through yoke portion 31 to an adjacent tooth portion 32 and returns to permanent magnet 13 is increased. Therefore, in Example 1, in each magnetic pole portion 11, the rear-side non-magnetic portion 30 prevents magnetic flux passing through the rear side of magnetic pole portion 11 from being short-circuited between a pair of magnetic pole portions 11 adjacent in the circumferential direction of rotor core 23 and the flange portion 33 of one tooth portion 32.

[0076] 9 and 11, in Example 1, the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 is closer to a sine wave than in the comparative example in an electrical angle range of approximately 20 degrees to 60 degrees. The magnetic flux density distribution being closer to a sine wave indicates that harmonic components superimposed on the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 can be reduced. In other words, in Example 1, the harmonic components superimposed on the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 can be reduced compared to the comparative example.

[0077] Here, it is believed that the harmonic components superimposed on the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 are caused by the short-circuiting of the magnetic flux passing behind the magnetic pole portion 11. Therefore, since the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 approaches a sine wave, it can be said that the short-circuiting of the magnetic flux passing behind the magnetic pole portion 11 is suppressed in Example 1 compared to the comparative example.

[0078] As described above, in Example 1, the magnetic pole portions 11 have rear-side non-magnetic portions 30, which prevents magnetic flux from short-circuiting between adjacent magnetic pole portions 11 through the flange portions 33 of the teeth portions 32, thereby increasing the amount of magnetic flux in the path from the rotor core 23 through the teeth portions 32 and the yoke portion 31. Furthermore, in Example 1, harmonic components superimposed on the magnetic flux density distribution at the position of the gap between the rotor 21 and the stator 22 can be reduced compared to the comparative example.

[0079] (Effects of Example 1) As described above, in the electric motor 1 of the first embodiment, the magnetic pole portions 11 of the rotor core 23 are provided with rear-side non-magnetic portions 30 at positions rearward in the direction of rotation R of the rotor 21 with respect to the d-axis D in an orthogonal plane that is perpendicular to the rotation centerline of the rotor 21 and passes through the rotor core 23. The rear-side non-magnetic portions 30 prevent magnetic flux from being short-circuited between a pair of magnetic pole portions 11 adjacent to each other in the circumferential direction of the rotor core 23 and one of the teeth 32. Note that the short-circuiting of magnetic flux here means that magnetic flux passing through the permanent magnet 13 circulates so as to return to the permanent magnet 13 via the inner peripheral end (flange portion 33) of the tooth portion 32 without passing through the yoke portion 31. As a result, the path of the magnetic flux on the rear side of each magnetic pole portion 11 in the direction of rotation R of the rotor 21 with respect to the d-axis D is changed by the rear-side non-magnetic portions 30 so that it passes through the d-axis D side. Therefore, the rear-side non-magnetic portion 30 reduces the magnetic flux passing through the q-axis Q side behind the magnetic pole portion 11 and increases the amount of magnetic flux passing through the d-axis D side behind the magnetic pole portion 11. As a result, according to the electric motor 1, the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 approaches a sine wave, thereby reducing harmonic components superimposed on the magnetic flux density distribution in the air gap between the rotor 21 and the stator 22. Therefore, according to the first embodiment, it is possible to reduce vibration of the rotor 21 of the electric motor 1 and reduce noise around the electric motor 1.

[0080] Furthermore, in the electric motor 1 of the first embodiment, the rear nonmagnetic portions 30 of the rotor core 23 are formed separately from the magnet embedding holes 12. This prevents a decrease in the mechanical strength of the rotor core 23 around the magnet embedding holes 12. It is possible.

[0081] In addition, in the electric motor 1 of the first embodiment, the rear-side non-magnetic portion 30 of the rotor core 23 is formed over a range of 30 degrees or more and 90 degrees or less, when the q-axis Q located on the rear side of the magnetic pole portion 11 in the rotation direction R of the rotor 21 is defined as 0 degrees in electrical angle and the front side in the rotation direction R is defined as a positive electrical angle. As a result, the rear-side non-magnetic portion 30 can block magnetic flux passing through the magnetic pole outer circumferential surface 29 of the magnetic pole portion 11 over a range of 30 degrees or more and 90 degrees or less in electrical angle.

[0082] Furthermore, the magnetic pole portions 11 of the rotor core 23 of the electric motor 1 of the first embodiment have rear-side non-magnetic portions 30, and the magnetic pole outer peripheral surfaces 29 have an asymmetric shape with respect to the d-axis D, and the cross-sectional shape of the magnetic pole portions 11 in the orthogonal plane is asymmetric with respect to the d-axis D. Because the magnetic pole portions 11 of the rotor core 23 have rear-side non-magnetic portions 30, it is possible to obtain the effect of making the magnetic flux density distribution at the position of the gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 closer to a sine wave, and the asymmetric shape of the magnetic pole outer peripheral surfaces 29 of the magnetic pole portions 11 can make the magnetic flux density distribution even closer to a sine wave.

[0083] Furthermore, in the electric motor 1 of the first embodiment, the magnetic pole outer peripheral surface 29 of the rotor core 23 has a front outer peripheral surface 29-F located forward in the rotational direction R of the rotor 21 with respect to the d-axis D, and a rear outer peripheral surface 29-R located rearward in the rotational direction R with respect to the d-axis D. When the magnetic pole portion 11 is virtually folded back along the d-axis D in an orthogonal plane so that the front outer peripheral surface 29-F is overlapped with the rear outer peripheral surface 29-R, the front outer peripheral surface 29-F has a small-diameter outer peripheral surface 34 located more inward than the rear outer peripheral surface 29-R in the radial direction of the rotor core 23. This prevents the distribution of magnetic flux from becoming asymmetric with respect to the q-axis Q, for example, in the central tooth 32 among the three teeth 32 aligned in the circumferential direction of the rotor core 23, when focusing on a magnetic path in which magnetic flux passing from the N-pole magnetic pole portion 11N through the tooth 32 is short-circuited to the adjacent S-pole magnetic pole portion 11S via the flange 33 without passing through the yoke portion 31. This is because, in an electric motor in which the ratio of the number of poles to the number of teeth is 2:3, when the magnetic pole portion 11 is virtually folded back along the d-axis D in an orthogonal plane so that the front outer peripheral surface 29-F is placed on the rear outer peripheral surface 29-R, if the front outer peripheral surface 29-F and the rear outer peripheral surface 29-R coincide with each other, the magnetic flux density distribution passing between the N-pole permanent magnet and the tooth adjacent to this N-pole permanent magnet and the magnetic flux density distribution passing between the S-pole permanent magnet and the tooth adjacent to this S-pole permanent magnet cannot be symmetrical with respect to the q-axis, for an N-pole permanent magnet and an S-pole permanent magnet that form a single pole pair.Therefore, when the magnetic pole portion 11 is virtually folded back along the d-axis D in an orthogonal plane so that the front outer peripheral surface 29-F is placed on the rear outer peripheral surface 29-R, the front outer peripheral surface 29-F and the rear outer peripheral surface 29-R do not coincide with each other, thereby making the magnetic flux distribution closer to symmetry with respect to the q-axis Q. Therefore, the magnetic flux density distribution when the above-described central teeth 32 are positioned on the q-axis Q approaches an ideal sine wave. Therefore, the magnetic flux density distribution at the position of the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 approaches a sine wave.

[0084] In the electric motor 1 of the first embodiment, the outer peripheral surface 27 of the rotor core 23 has a groove region A1 in which grooves 16 are formed so that the q-axis Q passes through the grooves 16, and a groove region A1 in which grooves 17 are formed so that the q-axis Q passes through the grooves 16. 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 rotation center O 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 rotation center O varies. The constant diameter region A2 has a front constant region A2-F located forward of the d-axis D in the direction of rotation R of the rotor 21, and a rear constant region A2-R located backward of the d-axis D in the direction of rotation R. The circumferential size of the front constant region A2-F is smaller than the circumferential size of the rear constant region A2-R. This makes it possible to easily obtain a shape in each magnetic pole outer peripheral surface 29 in which the rate at which the gaps formed within the range of the front outer peripheral surface 29-F gradually increase and the rate at which the gaps formed within the range of the rear outer peripheral surface 29-R gradually increase is smaller than that of the front outer peripheral surface 29-F. In other words, when the magnetic pole portion 11 is virtually folded back along the d-axis D in the orthogonal plane and the front outer peripheral surface 29-F is placed on the rear outer peripheral surface 29-R, it is possible to easily realize a shape in which the front outer peripheral surface 29-F has a small-diameter outer peripheral surface 34 that is located more inward than the rear outer peripheral surface 29-R in the radial direction of the rotor core 23.

[0085] Furthermore, in the electric motor 1 of the first embodiment, the center line 30c of the first portion 30a of the rear-side non-magnetic portion 30 of the rotor core 23, which is aligned along the extension direction of the first portion 30a, intersects with the permanent magnet 13. This makes it easier for the rear-side non-magnetic portion 30 to block the path of magnetic flux attempting to pass through the rear-side non-magnetic portion 30, thereby enhancing the effect of restricting the short circuit of magnetic flux described above. In addition, a large thickness can be ensured between the rear-side non-magnetic portion 30 arranged as described above and the magnetic pole outer peripheral surface 29, thereby suppressing a decrease in the mechanical strength of the rotor core 23 around the rear-side non-magnetic portion 30 and the q-axis-side non-magnetic portion 15.

[0086] Furthermore, in the electric motor 1 of the first embodiment, the rear-side non-magnetic portion 30 of the rotor core 23 is disposed radially inward of the q-axis-side non-magnetic portion 15 in the radial direction of the rotor core 23. This ensures a large thickness between the rear-side non-magnetic portion 30 and the magnetic pole outer peripheral surface 29, thereby preventing a decrease in the mechanical strength of the rotor core 23 around the rear-side non-magnetic portion 30 and the q-axis-side non-magnetic portion 15.

[0087] Other embodiments will be described below with reference to the drawings. In the other embodiments, the same components and parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and the description thereof will be omitted. [Example]

[0088] 12 is a plan view showing a rotor core 23 of Example 2. Example 2 differs from Example 1 in the shape of the rear non-magnetic portion provided in each magnetic pole portion 11.

[0089] (Shape of rear non-magnetic part) 12 , similar to the first embodiment, the magnetic pole portion 11 in the second embodiment has a magnetic pole outer peripheral surface 29 formed in a shape asymmetric with respect to the d-axis D. The magnetic pole portion 11 in the second embodiment is provided with only a rear-side non-magnetic portion 40 as a non-magnetic portion provided separate from the magnet embedding hole 12. Similar to the rear-side non-magnetic portion 30 in the first embodiment, the rear-side non-magnetic portion 40 prevents 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.

[0090] The rear-side non-magnetic portion 40 is formed in the shape of an elongated hole extending from the magnet embedding hole 12 toward the magnetic pole outer peripheral surface 29 (described later). In an orthogonal plane, the rear-side non-magnetic portion 40 is disposed so that a center line 40c along the longitudinal direction intersects with the permanent magnet 13. The center line 40c here is a straight line that passes through the center of the rear-side non-magnetic portion 40 in the width direction (i.e., the short direction) and extends along the longitudinal direction of the rear-side non-magnetic portion 40. By disposing the rear-side non-magnetic portion 40 in this manner, the rear-side non-magnetic portion 40 can easily block the path of magnetic flux that attempts to pass through the rear-side non-magnetic portion 40. As a result, it is possible to prevent the magnetic flux that passes through the permanent magnet 13 from passing through the inner peripheral end (flange portion 33) of the tooth portion 32 without passing through the yoke portion 31 and returning to the permanent magnet 13, thereby achieving the effect of restricting the short circuit of magnetic flux described above.

[0091] The rear-side non-magnetic portion 40 is disposed radially inward of the q-axis-side non-magnetic portion 15 in the radial direction of the rotor core 23. This ensures a large thickness between the rear-side non-magnetic portion 40 and the magnetic pole outer peripheral surface 29, thereby preventing a decrease in the mechanical strength of the rotor core 23 around the rear-side non-magnetic portion 40 and the q-axis-side non-magnetic portion 15.

[0092] In addition, in the second embodiment, the rear non-magnetic portion 40 is arranged only on the rear side of the magnetic pole portion 11 in the rotation direction R of the rotor 21 with respect to the d-axis D. This makes it easy to realize a cross-sectional shape of the magnetic pole portion 11 in an orthogonal plane that is asymmetric with respect to the d-axis D.

[0093] Fig. 13 is a plan view showing magnetic lines of force in Example 2. Fig. 14 is a diagram showing magnetic flux density distribution in the circumferential direction of the rotor in Example 2. In Fig. 14, the vertical axis represents magnetic flux density [T] and the horizontal axis represents electrical angle [degrees (deg)]. In Fig. 14, the solid line represents a sine wave and the dashed line represents Example 2.

[0094] 13 , in each magnetic pole portion 11 of the second embodiment, as in the first embodiment, the path of the 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 non-magnetic portion 30 so that it passes through the d-axis D side. Therefore, the rear-side non-magnetic portion 30 serves to reduce the magnetic flux passing through the q-axis Q side behind the magnetic pole portion 11 and to increase the amount of magnetic flux passing through the d-axis D side behind the magnetic pole portion 11 by the reduced amount. Therefore, in the second embodiment, the rear-side non-magnetic portion 30 prevents the magnetic flux passing through the front side of the magnetic pole portion 11 from being short-circuited 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.

[0095] In the electrical angle range of approximately 20 degrees to 60 degrees, the magnetic flux density distribution at the position of the air gap between rotor 21 and stator 22 in the circumferential direction of rotor 21 in Example 2 shown in Fig. 14 is closer to a sine wave than the magnetic flux density distribution in the comparative example shown in Fig. 11. By making the magnetic flux density distribution closer to a sine wave in this way, in Example 2, it is possible to reduce harmonic components superimposed on the magnetic flux density distribution at the position of the air gap between rotor 21 and stator 22 compared to the comparative example.

[0096] Therefore, in Example 2, since the magnetic pole portion 11 has the rear non-magnetic portion 40, the magnetic flux is prevented from short-circuiting between adjacent magnetic pole portions 11 through the flange portion 33 of the tooth portion 32, and the amount of magnetic flux in the path from the rotor core 23 through the tooth portion 32 and the yoke portion 31 can be increased.

[0097] (Effects of Example 2) As described above, in the electric motor of Example 2, the magnetic pole portion 11 has the rear non-magnetic portion 40, so that, as in Example 1, the magnetic flux density distribution at the position of the gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 is made closer to a sine wave, thereby reducing the harmonic components superimposed on the magnetic flux density distribution in the gap between the rotor 21 and the stator 22. [Example]

[0098] 15 is a plan view illustrating a main portion of a rotor core according to Example 3. Example 3 has a rear nonmagnetic portion 30 similar to Example 1, but differs from Example 1 in that the magnetic pole outer peripheral surface 29 in the circumferential direction of rotor core 23 has a symmetrical shape.

[0099] (Shape of the outer surface of the magnetic pole) 15 , in Example 3, the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 is formed in a shape symmetrical with respect to the d-axis D. In Example 3, in the above-mentioned orthogonal plane, 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, the distance from the rotation center O of the rotor 21 to the magnetic pole outer peripheral surface 29 of each magnetic pole portion 11 at a position on the d-axis D, i.e., the radius of the rotor core 23, becomes the maximum outer diameter L.

[0100] 16 is a plan view showing magnetic lines of force in the third embodiment. As shown in FIG. 16 , in each magnetic pole portion 11 in the third embodiment, as in the first embodiment, the path of the magnetic flux on the rear side of the direction of rotation R of the rotor 21 with respect to the d-axis D is changed by the rear-side non-magnetic portion 30 so that it passes through the d-axis D side. Therefore, the rear-side non-magnetic portion 30 serves to reduce the magnetic flux passing through the q-axis Q side behind the magnetic pole portion 11 and increase the amount of magnetic flux passing through the d-axis D side behind the magnetic pole portion 11 by the reduced amount. As a result, in each magnetic pole portion 11, the rear-side non-magnetic portion 30 prevents the magnetic flux passing through the front side of the magnetic pole portion 11 from being short-circuited 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.

[0101] (Effects of Example 3) As described above, in the electric motor of Example 3, even if the magnetic pole outer surface 29 of the magnetic pole portion 11 is formed in a shape symmetrical with respect to the d-axis D, by appropriately setting the size, shape, and arrangement of the rear non-magnetic portion 30 of the magnetic pole portion 11, it is possible to make the magnetic flux density distribution at the position of the gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 closer to a sine wave, as in Example 1, and it is possible to reduce the harmonic components superimposed on the magnetic flux density distribution in the gap between the rotor 21 and the stator 22. [Explanation of symbols]

[0102] 1 electric motor 3 shafts 11 Magnetic pole part 11N N pole magnetic pole part 11S S pole magnetic pole part 12 (12a~12f) Magnet embedding hole 13(13a~13f) Permanent magnet 14(14a~14f), 15(15a~15f) q-axis side non-magnetic part 16, 17 Groove 19 d-axis side non-magnetic part 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 30 Rear non-magnetic part 30a Part 1 30b 2nd part 30c center line 31 York 32 Teeth 40 Rear non-magnetic part 101 Compressor 102 Container 105 Compression section A1 Groove area A2 constant diameter area A2-F Front fixed area A2-R Rear fixed area A3 Diameter change area C1, C2 corner D d axis O Center of rotation Q q axis R Rotation direction

Claims

1. a rotor having a rotor core in which permanent magnets are embedded in magnet embedding holes and a plurality of magnetic pole portions are provided along the circumferential direction; a stator having a plurality of teeth arranged on an outer circumferential side of the rotor and an annular yoke connecting the plurality of teeth, In a plane perpendicular to the rotation center line of the rotor and passing through the rotor core, when a straight line connecting the center of the magnetic pole portion in the circumferential direction and the rotation center of the rotor is defined as a d-axis, and a straight line connecting the center of rotation and the center between adjacent magnetic pole portions in the circumferential direction is defined as a q-axis, In the plane, the magnetic pole portion is provided with a rear non-magnetic portion at a position rearward in a rotation direction of the rotor with respect to the d axis, the rear non-magnetic portion is formed separately from the magnet embedding hole and prevents magnetic flux from being short-circuited between a pair of the magnetic pole portions adjacent to each other in the circumferential direction and one of the tooth portions, the magnetic pole portion is provided with only the rear non-magnetic portion as a non-magnetic portion provided separately from the magnet embedding hole.

2. the rear-side non-magnetic portion is formed over a range of 30 degrees or more and 90 degrees or less, when the q-axis located on the rear side of the magnetic pole portion in the rotation direction is defined as 0 degrees in electrical angle and the front side of the rotation direction is defined as a positive electrical angle.

2. The electric motor according to claim 1.

3. When the number of the magnetic pole portions is 2m, in the mechanical angle of the range in the circumferential direction between adjacent magnetic pole portions, when the q-axis located on the rear side with respect to the magnetic pole portion on the rear side in the rotation direction is set to 0 degrees, The angle is formed over a range of (360 / 2m) x (1 / 6) degrees or more and (360 / 2m) x (3 / 6) degrees or less.

2. The electric motor according to claim 1.

4. the rear-side nonmagnetic portion increases magnetic flux circulating through the pair of magnetic pole portions adjacent to each other in the circumferential direction, the pair of tooth portions adjacent to each other in the circumferential direction, and the yoke portion connecting the pair of tooth portions.

2. The electric motor according to claim 1.

5. the rear non-magnetic portion restricts short-circuiting of the magnetic flux when the q-axis of the rotor coincides with the center of one of the plurality of teeth in the width direction during rotation of the rotor.

5. The electric motor according to claim 4.

6. the cross-sectional shape of the magnetic pole portion in the plane is asymmetric with respect to the d-axis; 2. The electric motor according to claim 1.

7. the rear non-magnetic portion has a first portion extending from the magnet embedding hole toward an outer circumferential surface of the magnetic pole portion, which is a side surface on the outer circumferential side of the magnetic pole portion; 2. The electric motor according to claim 1.

8. In the plane, a center line of the rear nonmagnetic portion, which is along a direction in which the first portion extends, intersects with the permanent magnet.

8. The electric motor according to claim 7.

9. the rear nonmagnetic portion has a second portion formed continuously with the first portion and extending toward the d-axis, a center line of the second portion in a lateral direction intersects with a center line of the first portion in a lateral direction; 8. The electric motor according to claim 7.

10. a q-axis side nonmagnetic portion is formed in the magnet embedding hole in the vicinity of the q-axis, the q-axis side nonmagnetic portion extending toward the outer circumferential surface of the magnetic pole portion, which is a side surface on the outer circumferential side of the magnetic pole portion, and the q-axis side nonmagnetic portion is formed in the magnet embedding hole in the vicinity of the q-axis, the rear-side non-magnetic portion is disposed radially inward of the rotor core relative to the q-axis-side non-magnetic portion.

2. The electric motor according to claim 1.

11. an arc-shaped magnetic pole outer peripheral surface, which is a side surface on the outer periphery of the magnetic pole portion, such that the distance between the magnetic pole outer peripheral surface and the rotation center gradually decreases from the d-axis toward the q-axis; 2. The electric motor according to claim 1.

12. the magnetic pole outer peripheral surface has an arc-shaped front outer peripheral surface located on the front side of the rotation direction relative to the d axis, and an arc-shaped rear outer peripheral surface located on the rear side of the rotation direction relative 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, 12. The electric motor according to claim 11.

13. 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, the outer peripheral surface of the rotor core has a groove region in which the groove is formed so that the q axis passes through the groove; 12. The electric motor according to claim 11.

14. The magnetic pole outer peripheral surface has an arc-shaped constant diameter region formed at a position through which the d-axis passes and having a constant distance from the rotation center, and an arc-shaped variable diameter region formed between the groove region and the constant diameter region and having a variable distance from the rotation center.

14. The electric motor according to claim 13.

15. the constant diameter region has a front constant region located on the front side of the d axis in the rotation direction, and a rear constant region located on the rear side of the d axis in the rotation direction, The front-side constant region has a smaller size in the circumferential direction than the rear-side constant region.

15. The electric motor of claim 14.

16. the rear non-magnetic portion is a through hole that passes through the rotor core along the rotation center line, 2. The electric motor according to claim 1.

17. The permanent magnets are provided on both sides of the d-axis in the magnetic pole portion.

2. The electric motor according to claim 1.

18. 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.

2. The electric motor according to claim 1.

19. An electric motor according to any one of claims 1 to 18; 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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