Rotor, electric motor, and compressor

Abstract

In a rotor (21), if a straight line connecting the center of a magnetic pole part (11) in the circumferential direction of a rotor core (23) and the rotation center (O) of the rotor core (23) in a plane orthogonal to the rotation center line of the rotor core (23) is defined as a d-axis (D), a permanent magnet (13) provided to each magnetic pole part (11) includes a first magnet (13A) disposed on one side of the d-axis (D) in the circumferential direction of the rotor core (23), and a second magnet (13B) disposed on the other side of the d-axis (D) in the circumferential direction of the rotor core (23). In the plane, if, as mechanical angles, a first angle formed by the longitudinal direction of the first magnet (13A) and the d-axis (D) at the outer circumferential-side of the rotor core (23) is denoted by θ1 and a second angle formed by the longitudinal direction of the second magnet (13B) and the d-axis (D) at the outer circumferential-side of the rotor core (23) is denoted by θ2, the first magnet (13A) and the second magnet (13B) satisfy θ1 = θ2 < 90 degrees and are disposed asymmetrically with respect to the d-axis (D).

Description

Rotor, Electric Motor, and Compressor

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

[0002] As an electric motor, one including an embedded magnet type rotor in which permanent magnets are embedded inside a rotor core is known. This type of electric motor includes a rotor in which a plurality of magnetic pole portions formed on the outer peripheral side of the permanent magnet are provided along the circumferential direction, and a stator having a plurality of tooth portions arranged on the outer peripheral side of the rotor and an annular yoke portion connecting the plurality of tooth portions.

[0003] As a rotor, when a straight line connecting the center of the magnetic pole portion in the circumferential direction of the rotor core and the center of rotation of the rotor core in a plane orthogonal to the rotation center line of the rotor core is defined as the d-axis, there is a rotor in which two permanent magnets are arranged in a V shape on both sides of the d-axis of the magnetic pole portion (Patent Document 1).

[0004] In the magnetic pole portion in Patent Document 1, by making the angles formed by the longitudinal directions of the two permanent magnets arranged in the magnetic pole portion different with respect to the d-axis, in the circumferential direction of the rotor core, the effective magnetic flux passing through the permanent magnet on either the front side or the rear side in the rotation direction of the rotor with respect to the d-axis is made larger than the effective magnetic flux passing through the permanent magnet on the other side in the rotation direction of the rotor with respect to the d-axis. The effective magnetic flux here is the magnetic flux that passes through the permanent magnet of the rotor core and circulates via the tooth portion and the yoke portion of the stator core. When the effective magnetic flux on the rear side in the rotation direction with respect to the d-axis is large as in Patent Document 1, the torque can be increased. When the motor output [W] is constant, since the product of the rotational speed [rpm] and the torque [N·m] is a constant value, when the effective magnetic flux on the front side in the rotation direction with respect to the d-axis is increased, although the torque decreases, the rotational speed can be increased instead.

[0005] Japanese Patent Application Laid-Open No. 2022-154152

[0006] In the manufacturing process of the embedded magnet type rotor described above, after the magnetic material as a permanent magnet is embedded in the rotor core, the rotor is attached to a magnetization device. In this manufacturing process, for example, the magnetic flux of the magnetization magnetic field passes through the magnetic pole section along the d axis, thereby manufacturing a rotor having permanent magnets that have been magnetized by the magnetization magnetic field. Here, the magnetization magnetic field refers to the magnetic field applied from the magnetization device to the magnetic material in order to magnetize it as a permanent magnet, that is, to magnetize it. In Patent Document 1, the two permanent magnets in the magnetic pole section have different angles between their longitudinal directions and the d axis, so when a magnetization magnetic field is applied along the d axis, the amount of magnetic flux of the magnetization magnetic field passing through the magnets differs between the two magnets. As a result, there is a risk that a difference will occur in the magnetization susceptibility (the ratio indicating how much a substance is magnetized (the magnitude of the magnetic moment density)) of the two magnets. Also as a result, a problem arises in which the magnet with the lower magnetization susceptibility of the two magnets has an increased risk of demagnetization. Differences in magnetic attraction and demagnetization rates can lead to problems such as an imbalance in the magnetic flux of the two permanent magnets and differences in durability.

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

[0008] One embodiment of the rotor disclosed in this application comprises a rotor core having a plurality of magnetic pole portions, each provided with a permanent magnet, arranged circumferentially. In a plane perpendicular to the rotational centerline of the rotor core, when the line connecting the center of the magnetic pole portion in the circumferential direction of the rotor core and the rotational center of the rotor core is defined as the d-axis, the permanent magnets provided in each magnetic pole portion include a first magnet positioned on one side of the circumferential direction of the rotor core with respect to the d-axis, and a second magnet positioned on the other side of the circumferential direction of the rotor core with respect to the d-axis. In the aforementioned plane, when the first angle formed by the longitudinal direction of the first magnet and the d-axis on the outer circumference of the rotor core is defined as the mechanical angle θ1, and the second angle formed by the longitudinal direction of the second magnet and the d-axis on the outer circumference of the rotor core is defined as the mechanical angle θ2, the first magnet and the second magnet satisfy θ1 = θ2 < 90 degrees and are positioned asymmetrically with respect to the d-axis.

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

[0010] Figure 1 is a longitudinal cross-sectional view showing the compressor of Example 1. Figure 2 is a plan view showing the electric motor of Example 1. Figure 3 is a plan view showing the rotor of Example 1. Figure 4 is a plan view illustrating the main part of the rotor core in Example 1. Figure 5 is a schematic diagram illustrating the arrangement of permanent magnets in the magnetic pole section of Example 1. Figure 6 is an enlarged view showing the outer magnetic pole surfaces of the N pole and S pole sections of the rotor core in Example 1. Figure 7 is a schematic diagram illustrating the outer magnetic pole surfaces of each magnetic pole section of the rotor core in Example 1. Figure 8 is a schematic diagram illustrating the shape of the outer magnetic pole surface of the rotor core in Example 1. Figure 9 is a plan view showing magnetic field lines in Example 1. Figure 10 is a plan view showing magnetic field lines in an example. Figure 11 is a plan view showing magnetic field lines in a comparative example. Figure 12 is a diagram illustrating the torque of the electric motor in the example. Figure 13 is a schematic diagram illustrating the arrangement of permanent magnets in the magnetic pole section of Example 2. Figure 14 is a schematic diagram illustrating the arrangement of permanent magnets in the magnetic pole section of Example 3. Figure 15 is a plan view showing the magnetic pole portion in Modification 1. Figure 16 is a plan view showing the magnetic field lines in Modification 1. Figure 17 is a plan view showing the magnetic pole portion in Modification 2. Figure 18 is a plan view showing the magnetic field lines in Modification 2. Figure 19 is a plan view showing the magnetic pole portion in Modification 3. Figure 20 is a plan view showing the magnetic field lines in Modification 3. Figure 21 is a plan view showing the magnetic pole portion in Modification 4. Figure 22 is a plan view showing the magnetic pole portion in Modification 5. Figure 23 is a plan view showing the magnetic pole portion in Modification 6. Figure 24 is a plan view showing the magnetic pole portion in Example 4.

[0011] The embodiments of the rotor, motor, and compressor disclosed in this application will be described in detail below with reference to the drawings. However, the rotor, motor, and compressor disclosed in this application are not limited by the embodiments described below.

[0012] (Compressor Configuration) Figure 1 is a longitudinal cross-sectional view showing the compressor of Embodiment 1. As shown in Figure 1, the compressor 101 is a so-called rotary compressor and comprises a container 102, a compression unit 105, and an electric motor 1. The container 102 is made of a metal material and forms a sealed internal space 107. The internal space 107 of the container 102 is formed in a generally cylindrical shape. When the container 102 is placed vertically on a horizontal plane, the central axis of the cylinder forming the internal space 107 is parallel to the vertical direction. An oil reservoir 108 is formed in the lower part of the internal space 107 of the container 102. Refrigerant oil, which is a lubricating oil for lubricating the compression unit 105, is stored in the oil reservoir 108. The container 102 is connected to an intake pipe 111 for drawing in refrigerant and a discharge pipe 112 for discharging compressed refrigerant. A shaft 3, which is rotated by an electric motor 1 (described later), is positioned in the internal space 107 of the container 102 such that one end of the shaft 3 is located in the oil reservoir 108. The shaft 3 is supported by the container 102 so as to be rotatable about the central axis of the cylinder that makes up the internal space 107. By rotating, the shaft 3 supplies the refrigerant oil stored in the oil reservoir 108 to the compression unit 105.

[0013] The compression section 105 is located in the lower part of the internal space 107 and above the oil reservoir 108. The compressor 101 further comprises an upper muffler cover 114 and a lower muffler cover 115. The upper muffler cover 114 is located above the compression section 105 in the internal space 107. The upper muffler cover 114 forms an upper muffler chamber 116 inside. The lower muffler cover 115 is located below the compression section 105 in the internal space 107 and above the oil reservoir 108. The lower muffler cover 115 forms a lower muffler chamber 117 inside. The lower muffler chamber 117 communicates with the upper muffler chamber 116 via a connecting 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] The compression unit 105 compresses the refrigerant supplied from the intake pipe 111 by the rotation of the shaft 3, and supplies the compressed refrigerant to the upper muffler chamber 116 and the lower muffler chamber 117. The refrigerant is compatible with refrigerant oil. The electric motor 1 is located above the compression unit 105 in the internal space 107.

[0015] (Motor Configuration) Figure 2 is a plan view showing the motor 1 in Embodiment 1. Figure 3 is a plan view showing the rotor in Embodiment 1. As shown in Figures 2 and 3, the motor 1 of Embodiment 1 is a 6-pole, 9-slot concentrated winding type 3-phase motor. The motor 1 comprises a rotor 21 and a stator 22 arranged on the outer circumference 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 together, for example, by crimping. A shaft 3, which serves as the rotation axis of the rotor core 23, is inserted through the central axis, which is the rotation centerline of the rotor core 23, and the shaft 3 and the rotor 21 are fixed together. Although not shown in the figures, the rotor core 23 may be provided with multiple elongated refrigerant gas passages that penetrate through the rotor core 23 in the axial direction (the axial direction of the shaft 3). The multiple refrigerant gas passages are arranged at intervals along the axis of the shaft 3. The main parts of the rotor core 23 in Embodiment 1 will be described later.

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

[0018] As shown in Figures 2 and 3, the stator core 24 is positioned with a predetermined air gap between it and the outer circumferential surface 27 of the rotor core 23. Details of the shape of the outer circumferential surface 27 of the rotor core 23 in the circumferential direction will be described later. The stator core 24 has nine teeth 32 extending radially inward from an annular yoke 31, formed at equal intervals of 40 degrees (mechanical angle) in the circumferential direction of the stator core 24. Each tooth 32 has a flange (inner circumferential end) 33 that protrudes from the tip located on the inner circumferential side of the stator core 24 to both sides in the circumferential direction of the stator core 24. Each tooth 32 is formed to have the same shape. As shown in Figure 2, each tooth 32 has a winding section 45 in which each winding 46 is wound in a concentrated winding manner. The multiple 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 from each winding section 45 and bundled together are covered with insulating tubing and inserted into the gaps between adjacent winding sections 45 in the circumferential direction (rotation direction R of the rotor 21) of the stator 22 (see Figure 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 Figure 3, the rotor core 23 of the electric motor 1 of Embodiment 1 has a plurality of magnet embedding holes 12a, 12b, 12c, 12d, 12e, 12f (hereinafter also referred to as magnet embedding holes 12) into which permanent magnets 13a, 13b, 13c, 13d, 13e, 13f (hereinafter also referred to as permanent magnets 13) are embedded. The rotor core 23 has two slit-shaped magnet embedding holes 12 in each magnetic pole portion 11, which will be described later, and are formed in a roughly V-shape on the orthogonal plane, i.e., on the end face of the rotor core 23. The two magnet embedding holes 12 in each magnetic pole portion 11 are adjacent at one end and the other end extends to the outer circumference of the rotor core 23. Plate-shaped permanent magnets 13 are embedded in the magnet embedding holes 12. Although end plates are attached to both axial ends of the rotor core 23 to prevent the permanent magnets 13 from coming out, the illustration of the end plates is omitted in order to explain the main part of the rotor core 23. These end plates are fixed to the rotor core 23 by rivets 8 that are passed through rivet holes 7 of the rotor core 23.

[0020] As described above, the rotor core 23 has six magnetic pole sections 11, namely three north pole sections 11N and three south pole sections 11S, which are arranged alternately along the circumferential direction of the rotor core 23 by embedding permanent magnets 13 in magnet embedding holes 12. Each of the north pole section 11N and south pole section 11S (hereinafter also referred to as magnetic pole section 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] Furthermore, in the electric motor disclosed in this application, where m is a natural number, the number of pole pairs formed by the magnetic pole portion 11 (N pole portion 11N and S pole portion 11S) is m, and the number of multiple teeth portions 32 is 3m. Also, in the rotor 21, the number of magnetic pole portions 11, i.e., the number of poles, is 2m. In the electric motor 1 of Embodiment 1, as an example, the number of poles is 6, the number of pole pairs is 3, and the number of teeth portions 32 is 9.

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

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

[0024] Figure 4 is a plan view illustrating the main parts of the rotor core 23 in Embodiment 1. As shown in Figure 4, the rotor core 23 has a plurality of q-axis side non-magnetic parts 14a to 14f, 15a to 15f (hereinafter referred to as q-axis side non-magnetic parts 14 and 15) formed near the q-axis Q in continuity with the magnet embedding hole 12, a plurality of d-axis side non-magnetic parts 19a to 19f (hereinafter referred to as d-axis side non-magnetic parts 19) formed on the d-axis D in continuity with the magnet embedding hole 12, a plurality of grooves 16 and 17, and a plurality of bridge parts 18 formed between the q-axis side non-magnetic parts 14 and 15 and the grooves 16 and 17.

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

[0026] The q-axis non-magnetic portions 14, 15 and the d-axis non-magnetic portion 19 are so-called flux barriers and are formed as spaces continuous with the magnet embedding holes 12. The q-axis non-magnetic portions 14, 15 and the d-axis non-magnetic portion 19 suppress the formation of a magnetic path in which magnetic flux circulates between adjacent magnetic pole portions 11 in the circumferential direction of the rotor core 23, bypassing the yoke portion 31 of the stator 22 and passing through the flange portion 33 of the teeth portion 32. In other words, the rotor core 23 has through holes formed along the rotational centerline of the rotor core 23 which is parallel to the axial direction of the shaft 3. The area of ​​the through hole that is filled by the permanent magnet 13 is the magnet embedding hole 12, and the area of ​​the through hole that is not filled by the permanent magnet 13 is the q-axis non-magnetic portions 14, 15 and the d-axis non-magnetic portion 19, which are air gaps that act as non-magnetic portions.

[0027] On the outer circumferential surface 27 of the rotor core 23, grooves 16 and 17 are formed along the rotational centerline of the rotor core 23, where a portion of the outer circumferential surface 27 is cut out and recessed in the radial direction of the rotor core 23, between adjacent magnetic pole portions 11 in the circumferential direction of the rotor core 23. In other words, the grooves 16 and 17 are located between adjacent q-axis side non-magnetic portions 14 and q-axis side non-magnetic portions 15 in the circumferential direction of the rotor core 23, and are positioned on the q-axis Q.

[0028] (Characteristic structure of the rotor core) Next, the characteristic structure of the rotor 21 in Embodiment 1 will be described. A characteristic of Embodiment 1 is the arrangement of two permanent magnets 13 in each magnetic pole portion 11.

[0029] (Arrangement of permanent magnets in the magnetic pole section) Figure 5 is a schematic diagram illustrating the arrangement of permanent magnets 13 in the magnetic pole section 11 in Embodiment 1. For convenience, only the permanent magnets 13 are shown in Figure 5, and the illustration of the magnet embedding holes 12, the q-axis side non-magnetic sections 14 and 15, and the d-axis side non-magnetic section 19 is omitted.

[0030] As shown in Figure 5, the permanent magnets 13 (13a to 13f) provided in each magnetic pole portion 11 in Embodiment 1 include a first magnet 13A positioned on one side of the circumferential direction of the rotor core 23 with respect to the d-axis D, and a second magnet 13B positioned on the other side of the circumferential direction of the rotor core 23 with respect to the d-axis D. The two permanent magnets 13 in one magnetic pole portion 11 are referred to as the first magnet 13A and the second magnet 13B, and the permanent magnets 13 in each magnetic pole portion 11 arranged in the circumferential direction of the rotor core 23 are also referred to as permanent magnets 13a to 13f. In an orthogonal plane, the first magnet 13A and the second magnet 13B have the same shape and are of the same size. That is, the first magnet 13A and the second magnet 13B have the same external dimensions.

[0031] In Embodiment 1, of the two permanent magnets 13, one permanent magnet 13 positioned on the front side of the rotor 21 in the rotation direction R relative to the d-axis D is designated as the first magnet 13A, and the other permanent magnet 13 positioned on the rear side of the rotor 21 in the rotation direction R relative to the d-axis D is designated as the second magnet 13B, but the invention is not limited thereto. That is, in the following description, if the arrangement of the two permanent magnets 13 in the rotation direction R of the rotor 21 relative to the d-axis D is not specified, one permanent magnet 13 positioned on the front side of the rotor 21 in the rotation direction R relative to the d-axis D may be designated as the second magnet 13B, and the other permanent magnet 13 positioned on the rear side of the rotor 21 in the rotation direction R relative to the d-axis D may be designated as the first magnet 13A.

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

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

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

[0035] In addition, as will be described in detail later, the first magnet 13A and the second magnet 13B satisfy the following conditions with respect to the d-axis D: θ1 = θ2 < 90 degrees ... (Equation 1). This suppresses differences in magnetization and demagnetization rates between the first magnet 13A and the second magnet 13B of each magnetic pole section 11. Therefore, the rotor 21 of Embodiment 1 can suppress imbalances in the magnetic flux amounts and differences in durability between the first magnet 13A and the second magnet 13B, thereby improving the quality of the electric motor 1.

[0036] (Asymmetrical arrangement of the first and second magnets) In the first embodiment, when the shortest distance between the first magnet 13A and the d-axis D in the orthogonal plane is L1a [mm], and the shortest distance between the d-axis D and the second magnet 13B is L1b [mm], the shortest distances L1a and L1b satisfy L1a ≠ L1b ... (Equation 2).

[0037] In other words, the first magnet 13A and the second magnet 13B are arranged differently in the direction perpendicular to the d-axis D, or in other words, in the circumferential direction of the rotor core 23. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole, making it possible to make the effective magnetic flux passing through the first magnet 13A and the effective magnetic flux passing through the second magnet 13B of the magnetic pole portion 11 different. Therefore, the effective magnetic flux passing through the permanent magnet 13A on one side with respect to the d-axis D can be made greater than the effective magnetic flux passing through the outer surface 29 of the magnetic pole on the other side with respect to the d-axis D. Equation 2 does not limit the arrangement of the first magnet 13A and the second magnet 13B in the rotation direction R of the rotor 21 with respect to the d-axis D.

[0038] In Embodiment 1, as an example, when the first magnet 13A is positioned in front of the rotor 21 in the rotation direction R relative to the d-axis D in an orthogonal plane, and the second magnet 13B is positioned behind the rotor 21 in the rotation direction R relative to the d-axis D, the shortest distances L1a and L1b satisfy L1a < L1b ... (Equation 3). As a result, in addition to the effect when Equation 2 is satisfied, in one magnetic pole section 11, the shortest distance L1a between the first magnet 13A, which is positioned in front of the rotor 21 in the rotation direction R relative to the d-axis D, and the d-axis D is smaller than the shortest distance L1b between the second magnet 13B, which is positioned behind the rotor 21 in the rotation direction R relative to the d-axis D, and the d-axis D. Compared to the case where the shortest distances L1a and L1b are equal, the effective magnetic flux passing through the first magnet 13A, which is the permanent magnet 13 on the front side in the rotation direction R of the magnetic pole section 11, is reduced, and the effective magnetic flux passing through the second magnet, which is the permanent magnet 13 on the rear side in the rotation direction R of the magnetic pole section 11, is increased. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side in the rotation direction R of the magnetic pole section 11 can be made larger than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side in the rotation direction R, thereby improving torque. In Embodiment 1, L1a:L1b ≈ 1:2.

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

[0040] In other words, the first magnet 13A and the second magnet 13B are arranged differently in the direction along the d-axis D, or in other words, in the radial direction of the rotor core 23. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole, making it possible to make the effective magnetic flux passing through the first magnet 13A and the effective magnetic flux passing through the second magnet 13B of the magnetic pole section 11 different. Therefore, in the magnetic pole section 11, the effective magnetic flux passing through one permanent magnet 13 with respect to the d-axis D can be made greater than the effective magnetic flux passing through the other permanent magnet 13 with respect to the d-axis D.

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

[0042] In other words, in Embodiment 1, in an orthogonal plane, if we consider the long sides along the longitudinal directions of the first magnet 13A and the second magnet 13B, and the shortest distance between the first magnet 13A and the d-axis D on a straight line extending the radially inner long side of the rotor core 23 of the first magnet 13A to the d-axis D is a [mm], and the shortest distance between the second magnet 13B and the d-axis D on a straight line extending the radially inner long side of the rotor core 23 of the second magnet 13B to the d-axis D is b [mm], then the shortest distances a and b satisfy a > b ... (Equation 6).

[0043] In other words, the arrangement of the first magnet 13A and the second magnet 13B satisfies equation 3 (and equation 2) and equation 5 (and equation 4) above, thereby satisfying equation 6. That is, in Embodiment 1, the first magnet 13A and the second magnet 13B are positioned differently in the circumferential direction of the rotor core 23, as well as in the radial direction of the rotor core 23. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so that the path of the magnetic flux passing through the outer surface 29 of the magnetic pole can be adjusted, and the effective magnetic flux passing through one permanent magnet 13 (second magnet 13B) with respect to the d-axis D in the magnetic pole portion 11 can be made greater than the effective magnetic flux passing through the other permanent magnet 13 (first magnet 13A) with respect to the d-axis D.

[0044] (Outer Peripheral 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 the orthogonal plane of the rotor core 23, among the outer peripheral surface 27 of the rotor core 23, the outer peripheral surface 27 of the rotor core 23 in the range forming one pole pair, which is one pole pair, is defined as the outer peripheral surface 28 of one pole pair. Also, in the orthogonal plane, the number of pole pairs formed by the magnetic pole portions 11 (a set of the N - pole magnetic pole portion 11N and the S - pole magnetic pole portion 11S) is set as m (m is a natural number). At this time, 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 outer peripheral surface 28 of one pole pair m times in the circumferential direction of the rotor core 23. That is, in the orthogonal plane, each of the m outer peripheral surfaces 28 of one pole pair is formed to be rotationally symmetric with respect to the rotation center O of the rotor 21. In other words, in the orthogonal plane, each of the portions obtained by equally dividing the outer peripheral surface 27 of the rotor core 23 in the circumferential direction into m parts with reference to the q - axis Q described later is the outer peripheral surface 28 of one pole pair, and each of the m outer peripheral surfaces 28 of one pole pair has the same shape. As a result, the path of the magnetic flux formed by the rotor core 23 and the stator core 24 facing the rotor core 23 in the radial direction is also periodically repeated m times. As a result, every 360 / m [degrees] in mechanical angle and every 360 [degrees] in electrical angle, the same magnetic flux density distribution is periodically repeated. Therefore, it is possible to suppress the increase in vibration caused by the irregular fluctuation of the magnetic flux density distribution during one rotation of the rotor core 23. For example, in the outer peripheral surface 27 of the rotor core 23 of the first embodiment, the outer peripheral surface 28 of one pole pair is repeated three times over the entire circumference of the rotor core 23.

[0045] Here, on the orthogonal plane described above, the points on the radially outermost side of the rotor core 23 among the ends of the two permanent magnets 13 of the magnetic pole portion 11 located on the outer peripheral surface 27 side of the rotor core 23 are defined as angles C1 and C2 on the d-axis D side at each end. The first boundary line B1 is defined as the straight 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. The second boundary line B2 is defined as the straight 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. At this time, the outer peripheral surface 27 of each magnetic pole portion 11 of the rotor core 23 has a magnetic pole outer peripheral surface 29 formed in the range between the two boundary lines (first boundary line B1 and second boundary line B2) that pass through one magnetic pole portion 11.

[0046] Therefore, the single pole pair outer surface 28 is a single pole pair that includes, in the circumferential direction of the outer surface 27 of the rotor core 23, as shown in Figure 4, the outer pole surface 29 of the N pole portion 11N (hereinafter also referred to as the N pole outer surface 29N) and the outer pole surface 29 of the S pole portion 11S (hereinafter also referred to as the S pole outer surface 29S), 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 in the rotation direction R with respect to the q axis Q in the groove portion 17 located on the front side in the rotation direction R with respect to the q axis Q in the groove portion 17 located on the front side in the rotation direction R with respect to the S pole portion 11S in the groove portion 17 located on the rear side in the rotation direction R with respect to the q axis Q in the groove portion 17. Each magnetic pole outer surface 29 (N pole outer surface 29N or S pole outer surface 29S) is the area of ​​the outer surface 27 of the rotor core 23 that is located between two adjacent q-axis Qs in the circumferential direction, and does not include the grooves 16 and 17, but is the outer surface of the magnetic pole portion 11. In other words, each magnetic pole outer surface 29 (N pole outer surface 29N and S pole outer surface 29S) is a portion formed in the circumferential direction of the outer surface 27 between two boundary lines (first boundary line B1 and second boundary line B2) that pass through one magnetic pole portion 11.

[0047] FIG. 6 is an enlarged view showing the magnetic pole outer peripheral surfaces 29 of the N - pole magnetic pole portion 11N and the S - pole magnetic pole portion 11S of the rotor core 23 in Example 1. As shown in FIGS. 4 and 6, in an orthogonal plane, the N - pole outer peripheral surface 29N of the N - pole magnetic pole portion 11N and the S - pole outer peripheral surface 29S of the S - pole magnetic pole portion 11S are formed in shapes that do not coincide with each other when one of the magnetic pole portions of the N - pole magnetic pole portion 11N and the S - pole magnetic pole portion 11S is virtually rotated 60° around the rotation center O of the rotor 21 and overlapped with the other magnetic pole portion of the N - pole magnetic pole portion 11N and the S - pole magnetic pole portion 11S. Note that the magnetic pole portion to be virtually rotated can be either the N - pole magnetic pole portion 11N or the S - pole magnetic pole portion 11S. Also, the direction of rotation around the rotation center O can be either clockwise or counterclockwise. Here, an explanation will be given assuming that the N - pole magnetic pole portion 11N is virtually rotated 60° counterclockwise and overlapped with the S - pole magnetic pole portion 11S.

[0048] When focusing on one pair of outer peripheral surfaces 28 of the rotor core 23 in Example 1, since the one pair of outer peripheral surfaces 28 are formed in different shapes with respect to the q - axis Q, in the N - pole permanent magnet 13 and the S - pole permanent magnet 13 forming one pole pair, it becomes 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 approach symmetry with respect to the q - axis Q. Therefore, it is possible to further approximate the magnetic flux density distribution (the radial magnetic flux density [T] at the gap position measured or analyzed over the circumferential direction) at the position of the air gap (air gap) formed between the rotor core 23 and the tooth portion 32 within the range of the one pair of outer peripheral surfaces 28 to a sine wave.

[0049] For example, in Example 1, the radius of curvature r of the diameter - change region A3 (described later) where the distance from the rotation center O of the rotor 21 to the outer peripheral surface 27 of the rotor core 23 changes is different between the diameter - change region A3 of the N - pole outer peripheral surface 29N and the diameter - change region A3 of the S - pole outer peripheral surface 29S. Thereby, it is possible to easily realize different shapes of the one pair of outer peripheral surfaces 28 with respect to the q - axis Q.

[0050] Furthermore, when one of the pole portions 11 of the north pole portion 11N and the south pole portion 11S is superimposed on the other pole portion 11, the rotation angle around the rotation center O that virtually rotates one of the pole portions 11 is 360 / (2m) [degrees]. (Let the number of pole pairs be m.) Also, in the following description, the rotation angle when virtually rotating the rotor 21 around the rotation center O is also 360 / (2m) [degrees]. For example, in Embodiment 1, since the number of pole pairs is m=3, when the north pole portion 11N is virtually rotated around the rotation center O of the rotor 21 and superimposed on the south pole portion 11S, the rotation angle is 360 / 6 = 60 [degrees].

[0051] (Shape of the outer magnetic pole surface) Figure 7 is a schematic diagram showing the outer magnetic pole surface 29 of each magnetic pole portion 11 of the rotor core 23 in Embodiment 1. Figure 8 is a schematic diagram for explaining the shape of the outer magnetic pole surface 29 of the rotor core 23 in Embodiment 1.

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

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

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

[0055] Figure 8 shows the rotor core 23 with the magnetic pole portion 11 virtually folded along the d-axis D in the orthogonal plane, and the front outer peripheral surface 29-F virtually superimposed on the rear outer peripheral surface 29-R. Here, we will explain the case where the N-pole magnetic pole portion 11N is virtually folded. As shown in Figure 8, when the N-pole magnetic pole portion 11N is virtually folded along the N-pole d-axis DN in the orthogonal plane of the rotor core 23 and superimposed, the N-pole front outer peripheral surface 29N-F has a small-diameter outer peripheral surface 34 that is located inside 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 that is located inside the N-pole front outer peripheral surface 29N-F in the radial direction of the rotor core 23. In other words, the outer peripheral surface 29N-F on the front side of the north pole has only a portion that overlaps with the outer peripheral surface 29N-R on the rear side of the north pole (overlapping outer peripheral surface 35) and a portion that is located on the inner side of the outer peripheral surface 29N-R on the rear side of the north pole (small diameter outer peripheral surface 34). And, when viewed from the side of the outer peripheral surface 29N-R on the rear side of the north pole, the outer peripheral surface 29N-R on the rear side of the north pole has only a portion that overlaps with the outer peripheral surface 29N-F on the front side of the north pole (overlapping outer peripheral surface 35) and a portion that is located on the outer side of the outer peripheral surface 29N-F on the rear side of the north pole (large diameter outer peripheral surface 36).

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

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

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

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

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

[0061] For example, in Embodiment 1, the radius of curvature r of the diameter 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 for the diameter change region A3 of the N pole outer circumferential surface 29N and the diameter change region A3 of the S pole outer circumferential surface 29S. This makes it easy to realize shapes that do not coincide when either the N pole portion 11N or the S pole portion 11S is virtually rotated 360 / (2m) [degrees] around the rotation center O of the rotor 21 and superimposed on the other pole portion of the N pole portion 11N or the S pole portion 11S.

[0062] Similarly, in the orthogonal plane of the rotor core 23, the outer peripheral surface 29N-F on the front side of the north pole and the outer peripheral surface 29S-F on the front side of the south pole are formed in such a shape that they do not coincide with each other when the north pole portion 11N and the south pole portion 11S are superimposed by virtually rotating them 360 / (2m) [degrees] around the rotation center O of the rotor 21 (see Figure 4).

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

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

[0065] For example, in Embodiment 1, the radius of curvature r of the diameter change region A3, where the distance from the rotation center O of the rotor 21 to the outer magnetic pole surface 29 of the rotor core 23 changes, is different for the diameter change region A3 of the N pole outer surface 29N and the diameter change region A3 of the S pole outer surface 29S. This makes it easy to realize shapes that do not coincide when either the N pole portion 11N or the S pole portion 11S is virtually rotated 360 / (2m) [degrees] around the rotation center O of the rotor 21 and superimposed on the other pole portion of the N pole portion 11N or the S pole portion 11S.

[0066] In the orthogonal plane described above, the outer magnetic pole surface 29, which is the outer peripheral side of the magnetic pole portion 11, is formed such that the distance between the outer magnetic pole surface 29 and the rotation center O gradually decreases as you move from the d-axis D towards the q-axis Q. Therefore, in the orthogonal plane, as shown in Figure 4, the outer magnetic pole surface 29 of each magnetic pole portion 11 has its largest outer diameter L at the position on the d-axis D, which is the distance from the rotation center O of the rotor 21, i.e., the radius of the rotor core 23. Also, in the orthogonal plane, the outer magnetic pole surface 29N of the N-pole magnetic pole portion 11N and the outer magnetic pole surface 29S of the S-pole magnetic pole portion 11S have the same outer diameter L at the position on the d-axis D, i.e., the distance from the rotation center O.

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

[0068] As shown in Figures 4 and 7, the outer surface of the magnetic pole 29 has a constant diameter region A2 formed at a position through which the d-axis D passes and at a constant distance from the rotation center O of the rotor 21, and a diameter-changing region A3 formed between the groove region A1 and the constant diameter region A2, at which the distance from the rotation center O of the rotor 21 changes. The constant diameter region A2 is a maximum radius of curvature region formed by a radius of curvature that is the maximum radius of curvature rm from the rotation center O. The diameter-changing region A3 is formed by a plurality of radii of curvature smaller than the maximum radius of curvature rm from the rotation center O in the constant diameter region A2.

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

[0070] The multiple radii of curvature that form the diameter change region A3 gradually decrease in radius r as they approach the grooves 16 and 17. For the sake of simplicity, we will assume that the combination of radii of curvature that forms the diameter change region A3 on the outer peripheral surface 29N-F on the front side of the N pole and the combination of radii of curvature that forms the diameter change region A3 on the outer peripheral surface 29N-R on the rear side of the N pole are equal. That is, the first radius of curvature r1-F of the front side diameter change region A3-F and the first radius of curvature r1-R of the rear side diameter change region A3-R are set to r1-F = r1-R = r1, and the second radius of curvature r2-F of the front side diameter change region A3-F and the second radius of curvature r2-R of the rear side diameter change region A3-R are set to r2-F = r2-R = r2. As an example, the diameter-changing region A3 has a first region A3-1 formed with a first radius of curvature r1 smaller than the maximum radius of curvature rm, and a second region A3-2 formed with a second radius of curvature r2 smaller than the first radius of curvature r1. The diameter-changing region A3 is formed continuously from the constant diameter region A2 toward the groove region A1, in the order of the first region A3-1 and the second region A3-2. In Example 1, since the difference in size between the first radius of curvature r1 and the second radius of curvature r2 is relatively small, the first region A3-1 and the second region A3-2 are smoothly continuous. The centers Or(Or1, Or2) of each radius of curvature r(r1, r2) are arranged to approach the outer circumferential surface 27 of the rotor core 23 as the radius of curvature decreases. Note that the number of types of radii of curvature is not limited to two.

[0071] In Figure 4, within the second radius of curvature r2-F of the front diameter change region A3-F, the N pole side of the magnetic pole 11N is defined as the second radius of curvature rn2-F, and the S pole side of the magnetic pole 11S is defined as the second radius of curvature rs2-F. Similarly, within the second radius of curvature r2-R of the rear diameter change region A3-R, the N pole side of the magnetic pole 11N is defined as the second radius of curvature rn2-R, and the S pole side of the magnetic pole 11S is defined as the second radius of curvature rs2-R. Note that the first radius of curvature r1 is not shown in Figure 4.

[0072] Furthermore, as shown in Figure 7, the constant diameter region A2 has a front constant region A2-F located on the front side of the rotation direction R of the rotor 21 with respect to the d axis D, and a rear constant region A2-R located on the rear side of the rotation 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 which, at each magnetic pole outer surface 29, the air gap formed in the front outer surface 29-F gradually increases toward the q axis Q, and the ratio of the air gap formed in the rear outer surface 29-R gradually increasing toward the q axis Q is smaller than the ratio of the air gap formed in the front outer surface 29-F gradually increasing toward the q axis Q. In other words, because the forward 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 forward outer peripheral surface 29N-F is superimposed on the N pole rear outer peripheral surface 29N-R, the N pole forward outer peripheral surface 29N-F has a small diameter outer peripheral surface 34 located inside 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 located inside the N pole forward outer peripheral surface 29N-F in the radial direction of the rotor core 23.

[0073] Furthermore, in Embodiment 1, as shown in Figures 7 and 8, 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 which the gap formed in the area of ​​the front outer surface 29-F of each magnetic pole outer surface 29 gradually increases, while the ratio of the gap formed in the area of ​​the rear outer surface 29-R gradually increasing is smaller than that of the front outer surface 29-F.

[0074] For the sake of simplicity, the explanation has been given assuming that the combinations of multiple radii of curvature forming the front diameter change region A3-F of the front outer peripheral surface 29N-F of the N pole and the combinations of multiple radii of curvature forming the rear diameter change region A3-R of the rear outer peripheral surface 29N-R of the N pole are equal. However, the combinations of multiple radii of curvature in the front diameter change region A3-F and the rear diameter change region A3-R may be different from each other. For example, the first radius of curvature r1-F of the front diameter change region A3-F (As3-F) and the first radius of curvature r1-R of the rear diameter change region A3-R (As3-R) may be different from each other. Similarly, the second radius of curvature r2-F (rs2-F) of the front side diameter change region A3-F (As3-F) and the second radius of curvature r2-R (rs2-R) of the rear side diameter change region A3-R (As3-R) may be different from each other.

[0075] (Inner surface shape of grooves) As shown in Figure 6, in the orthogonal plane of the rotor core 23, the shape of the inner surface 16a of groove 16 is formed asymmetrically with respect to the q-axis Q. Similarly, the shape of the inner surface 17a of groove 17 is formed asymmetrically with respect to the q-axis Q. In addition, grooves 16 and groove 17 are arranged alternately along the circumferential direction of the rotor core 23 on the outer circumferential surface 27 of the rotor core 23. In the orthogonal plane, the shapes of the inner surfaces 16a of groove 16 and the inner surfaces 17a of groove 17 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 and 17a of grooves 16 and 17 are formed as a result of smoothly continuing the inner surfaces 16a and 17a with the diameter change region A3 of each magnetic pole outer circumferential surface 29.

[0076] (Shape of non-magnetic parts) The two q-axis side non-magnetic parts 14 and 15 of the S pole magnetic part 11S are formed in a shape asymmetrical to each other with respect to the S pole d axis DS, which is the d axis of the S pole magnetic part 11S. The two q-axis side non-magnetic parts 14 and 15 of the N pole magnetic part 11N are formed in a shape asymmetrical to each other with respect to the N pole d axis DN, which is the d axis of the N pole magnetic part 11N. Furthermore, the two q-axis side non-magnetic parts 14 and 15 of the N pole magnetic part 11N and the two q-axis side non-magnetic parts 14 and 15 of the S pole magnetic part 11S are formed in a shape that does not coincide with each other when the N pole magnetic part 11N and the S pole magnetic part 11S are superimposed by virtually rotating them 360 / (2m) [degrees] around the rotation center O of the rotor 21.

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

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

[0079] In Example 1, in the orthogonal plane of the rotor core 23, the two permanent magnets 13 (first magnet 13A and second magnet 13B) of the magnetic pole section 11 have the same angle between their longitudinal directions and the d-axis D. Therefore, when a magnetizing magnetic field is applied along the d-axis D, the amount of magnetic flux of the magnetizing magnetic field passing through the magnetic material that becomes the permanent magnet 13 is equal for both permanent magnets 13. As a result, it is possible to prevent a difference in the magnetization rate (a ratio indicating how much a material is magnetized (magnitude of magnetic moment density) when an external magnetic field H is applied) between the two permanent magnets 13. Therefore, it is possible to prevent a difference in magnetization rate and demagnetization rate between the two permanent magnets 13 (first magnet 13A and second magnet 13B). As a result, it is possible to suppress problems such as an imbalance in the amount of magnetic flux of the two permanent magnets 13 and differences in durability.

[0080] (Comparison of Example and Comparative Example) Figure 10 is a plan view showing the magnetic field lines in the analysis model corresponding to the example (hereinafter, the analysis model of the example). The analysis model of the example is the same as in Example 1 in that the two permanent magnets 13 in the magnetic pole section 11 are arranged asymmetrically with respect to the d axis D, but for convenience, an analysis model is used in which the q-axis side non-magnetic sections 14, 15 and the d-axis side non-magnetic section 19 are not provided. Figure 11 is a plan view showing the magnetic field lines in the analysis model corresponding to the comparative example (hereinafter, the analysis model of the comparative example). The analysis model of the comparative example differs from Example 1 in that the two permanent magnets 13 in the magnetic pole section 11 are arranged symmetrically with respect to the d axis D, and, similar to the analysis model of the example, an analysis model is used in which the q-axis side non-magnetic sections 14, 15 and the d-axis side non-magnetic section 19 are not provided. In the analysis model of the comparative example, the same members and parts as in the analysis model of the example are indicated by the same reference numerals as in the example (analysis model of the example).

[0081] Comparing Figure 10 and Figure 11, in the analytical model of the embodiment, the amount of magnetic flux passing through the permanent magnet 13 (second magnet 13B) located on the rear side of the rotor core 23 in the rotation direction R is increased compared to the analytical model of the comparative example. For example, in the analytical model of the comparative example shown in Figure 11, there are 4 magnetic field lines that pass through the permanent magnet 13 (second magnet 13B) located on the rear side of the rotation direction R when the tooth portion 32 located on the front side of the rotor 21 in the rotation direction R is radially cut vertically from the tooth portion 32 located on the front side of the rotor 21 in the rotation direction R of the three tooth portions 32 arranged in the circumferential direction, while in the analytical model of the embodiment shown in Figure 10, the number of magnetic field lines that pass through the permanent magnet 13 (second magnet 13B) located on the rear side of the rotation direction R when the tooth portion 32 located on the front side of the rotor 21 in the rotation direction R is radially cut vertically from the tooth portion 32 arranged in the circumferential direction is increased to 6. The reason for this difference is expected to be that, in the analytical model of the embodiment, compared to the analytical model of the comparative example, the permanent magnet 13 (second magnet 13B) located on the rear side in the rotation direction R with respect to the d-axis D is closer to the outer surface 29 of the magnetic pole, making it easier for the effective magnetic flux that traverses the teeth portion 32 and passes through the outer surface 29 of the magnetic pole to pass through the second magnet 13B than the first magnet 13A. In this way, in each magnetic pole portion 11 of the embodiment, the magnetic flux that short-circuits between adjacent magnetic pole portions 11 in the circumferential direction of the rotor core 23 is reduced, reducing the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side in the rotation direction R of the rotor 21 with respect to the d-axis D, and increasing the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side in the rotation direction R with respect to the d-axis D.

[0082] (Shift in Torque Fluctuation Peak) The shift in the torque fluctuation peak due to the position of two permanent magnets 13 (first magnet 13A, second magnet 13B) arranged on either side of the d-axis D in the magnetic pole portion 11 of the rotor 21 of the embodiment will be explained. Here, one permanent magnet 13 positioned on the front side of the rotation direction R of the rotor 21 with respect to the d-axis D is referred to as the first magnet 13A, and the other permanent magnet 13 positioned on the rear side of the rotation direction R with respect to the d-axis D is referred to as the second magnet 13B. Figure 12 is a diagram for explaining the torque of the electric motor 6 of the embodiment, and shows the torque fluctuation associated with the rotation of the rotor 21. In Figure 12, the vertical axis shows torque, and the horizontal axis shows electrical angle [°]. The direction of arrow a is the front side of the rotation direction R of the rotor 21.

[0083] In Figure 12, the solid line RT shows the fluctuation of the reluctance torque of the electric motor 1. The dashed line MT1 shows the fluctuation of the magnet torque when permanent magnets are arranged symmetrically with respect to the d-axis D, i.e., the magnet torque before shifting, and is the magnet torque in the comparative example. The broken line MT2 shows the fluctuation of the magnet torque when a first magnet is formed located on the front side in the rotation direction R of the rotor 21, i.e., the magnet torque after shifting, and is the magnet torque in the embodiment. The broken line CT1 shows the combined torque before shifting, which is the sum of the reluctance torque (solid line RT) and the magnet torque before shifting (dashed line MT1). The thick line CT2 shows the combined torque before shifting, which is the sum of the reluctance torque (solid line RT) and the magnet torque after shifting (broken line MT2), and is the combined torque in the embodiment.

[0084] As shown in Figure 12, in this embodiment, the peak of the magnet torque shown by the dashed line MT2 is moved forward in the rotation direction R of the rotor 21, and is moved in a direction that approaches the positive peak of the reluctance torque fluctuation shown by the solid line RT. As a result, in this embodiment, the peak of the combined torque shown by the dashed line CT2 is larger than the peak of the combined torque shown by the dashed line CT1. As a result, the torque of the electric motor 1 can be increased.

[0085] (Effects of Example 1) As described above, in the rotor 21 of Example 1, the permanent magnets 13 provided in each magnetic pole portion 11 include a first magnet 13A positioned on one side of the circumferential direction of the rotor core 23 with respect to the d axis D, and a second magnet 13B positioned on the other side of the circumferential direction of the rotor core 23 with respect to the d axis D. In a perpendicular plane, when the first angle formed by the longitudinal direction of the first magnet 13A and the d axis D on the outer circumference of the rotor core 23 is θ1, and the second angle formed by the longitudinal direction of the second magnet 13B and the d axis D on the outer circumference of the rotor core 23 is θ2, the first magnet 13A and the second magnet 13B satisfy θ1 = θ2 < 90 degrees ... (Equation 1) and are positioned asymmetrically with respect to the d axis D. This allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole, reducing the effective magnetic flux passing through one permanent magnet 13 (first magnet 13A) with respect to the d-axis D, and increasing the effective magnetic flux passing through the other permanent magnet 13 (second magnet 13B) with respect to the d-axis D. Furthermore, it suppresses differences in magnetization and demagnetization rates between the first magnet 13A and the second magnet 13B, which are positioned on both sides of the d-axis D in the magnetic pole section 11. Therefore, the effective magnetic flux passing through one permanent magnet 13 (second magnet) with respect to the d-axis D can be made greater than the effective magnetic flux passing through the other permanent magnet 13 (first magnet 13A) with respect to the d-axis D. As a result, the torque of the electric motor 1 can be increased, and the quality of the electric motor 1 can be improved.

[0086] Furthermore, in the rotor 21 of Embodiment 1, when the shortest distance between the first magnet 13A and the d-axis D in an orthogonal plane is L1a, and the shortest distance between the d-axis D and the second magnet 13B is L1b, the equation L1a ≠ L1b ... (Equation 2) is satisfied. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so the path of the magnetic flux passing through the outer surface 29 of the magnetic pole can be adjusted, reducing the effective magnetic flux passing through one permanent magnet 13 (first magnet 13A) with respect to the d-axis D, and increasing the effective magnetic flux passing through the other permanent magnet 13 (second magnet 13B) with respect to the d-axis D. Therefore, the effective magnetic flux passing through one permanent magnet 13 (second magnet 13B) with respect to the d-axis D can be made greater than the effective magnetic flux passing through the other permanent magnet 13 (first magnet 13A) with respect to the d-axis D.

[0087] Furthermore, in the rotor 21 of Embodiment 1, when the first magnet 13A is positioned in front of the rotor core 23 in the rotation direction R relative to the d-axis D, and the second magnet 13B is positioned behind the rotor core 23 in the rotation direction R relative to the d-axis D, the shortest distances L1a and L1b satisfy L1a < L1b ... (Equation 3). This reduces the magnetic flux passing through the first magnet 13A, which is the permanent magnet 13 on the front side of the rotor core 23 in the rotation direction R relative to the d-axis D, and increases the magnetic flux passing through the second magnet 13B, which is the permanent magnet 13 on the rear side of the rotor core 23 in the rotation direction R relative to the d-axis D. Therefore, the effective magnetic flux passing through the permanent magnet 13 on the rear side of the rotation direction R relative to the d-axis D (second magnet 13B) can be made greater than the effective magnetic flux passing through the permanent magnet 13 on the front side of the rotation direction R relative to the d-axis D (first magnet 13A).

[0088] Furthermore, in the rotor 21 of Embodiment 1, when the shortest distance between the first magnet 13A and the rotation center O of the rotor 21 is L2a and the shortest distance between the second magnet 13B and the rotation center O of the rotor 21 is L2b, the equation L2a ≠ L2b ... (Equation 4) is satisfied. As a result, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so the path of the magnetic flux passing through the outer surface 29 of the magnetic pole can be adjusted, reducing the effective magnetic flux passing through one permanent magnet 13 (first magnet 13A) with respect to the d-axis D and increasing the effective magnetic flux passing through the other permanent magnet 13 (second magnet 13B) with respect to the d-axis D. Therefore, the effective magnetic flux passing through one permanent magnet 13 (second magnet 13B) with respect to the d-axis D can be made greater than the effective magnetic flux passing through the other permanent magnet 13 (first magnet 13A) with respect to the d-axis D.

[0089] Furthermore, in the rotor 21 of Embodiment 1, when the first magnet 13A is positioned in front of the rotor core 23 in the rotation direction R relative to the d-axis D, and the second magnet 13B is positioned behind the rotor core 23 in the rotation direction R relative to the d-axis D, the shortest distances L2a and L2b satisfy L2a < L2b ... (Equation 5). This reduces the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side of the rotor core 23 in the rotation direction R relative to the d-axis D, and increases the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side of the rotor core 23 in the rotation direction R relative to the d-axis D. Therefore, the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on the rear side of the rotor core 23 in the rotation direction R relative to the d-axis D can be made greater than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the front side of the rotor core 23 in the rotation direction R relative to the d-axis D.

[0090] Furthermore, in the rotor 21 of Embodiment 1, the magnetic pole outer circumferential surface 29 of the rotor core 23 has a front outer circumferential surface 29-F located on the front side of the rotation direction R of the rotor 21 with respect to the d axis D, and a rear outer circumferential surface 29-R located on the rear side of the rotation 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 and the front outer circumferential surface 29-F is superimposed on the rear outer circumferential surface 29-R, the front outer circumferential surface 29-F has a small-diameter outer circumferential surface 34 located inward from the rear outer circumferential surface 29-R in the radial direction of the rotor core 23. As a result, for example, when considering a magnetic path in the central tooth portion 32 of the three tooth portions 32 arranged in the circumferential direction of the rotor core 23, where the magnetic flux from the N pole portion 11N passing through the tooth portion 32 short-circuits to the adjacent S pole portion 11S via the flange portion 33 without passing through the yoke portion 31, the asymmetry of the magnetic flux distribution with respect to the q axis Q is suppressed. Therefore, the magnetic flux density distribution when the central teeth portion 32 described above is located on the q-axis Q can be brought closer to an ideal sine wave. Thus, the magnetic flux density distribution at the location of the air gap between the rotor 21 and the stator 22 in the circumferential direction of the rotor 21 can be brought closer to a sine wave.

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

[0092] Figure 13 is a schematic diagram illustrating the arrangement of the permanent magnets 13 in the magnetic pole section 11 of Embodiment 2. As shown in Figure 13, in the magnetic pole section 11 of the rotor 51 of Embodiment 2, the first magnet 13A is positioned on the front side of the rotor core 23 in the rotation direction R relative to the d-axis D, and the second magnet 13B is positioned on the rear side of the rotation direction R relative to the d-axis D. Similar to Embodiment 1, the first magnet 13A and the second magnet 13B are positioned asymmetrically with respect to the d-axis D, with the first angle θ1 [degrees] and the second angle θ2 [degrees] with respect to the d-axis D satisfying θ1 = θ2 < 90 degrees ... (Equation 1).

[0093] In the rotor 51 of Embodiment 2, when the shortest distance between the first magnet 13A and the d-axis D in an orthogonal plane is L1a [mm], and the shortest distance between the d-axis D and the second magnet 13B is L1b [mm], the shortest distances L1a and L1b satisfy L1a < L1b ... (Equation 3).

[0094] In other words, the first magnet 13A and the second magnet 13B are positioned differently relative to the d-axis D in the circumferential direction of the rotor core 23. To put it another way, the rotor 51 of Embodiment 2 corresponds to an arrangement in which the first magnet 13A and the second magnet 13B, which are arranged symmetrically with respect to the d-axis D in an orthogonal plane, are each shifted in position along a direction perpendicular to the d-axis D, toward the rear side of the rotation direction R of the rotor core 23 with respect to the d-axis D.

[0095] (Effects of Example 2) As described above, in the rotor 51 of Example 2, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so the path of the magnetic flux passing through the outer surface 29 of the magnetic pole can be adjusted, and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D can be made greater than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D. Also, in Example 2, as in Example 1, the first angle θ1 of the first magnet 13A and the second angle θ2 of the second magnet 13B satisfy equation 1 (θ1 = θ2 < 90 degrees), so that a difference in magnetization rate and demagnetization rate occurs between the first magnet 13A and the second magnet 13B which are arranged on both sides of the d-axis D in the magnetic pole section 11.

[0096] Figure 14 is a schematic diagram illustrating the arrangement of the permanent magnets 13 in the magnetic pole section 11 of Embodiment 3. As shown in Figure 14, in the magnetic pole section 11 of the rotor 52 of Embodiment 3, the first magnet 13A is positioned on the front side of the rotor core 23 in the rotation direction R relative to the d-axis D, and the second magnet 13B is positioned on the rear side of the rotor core 23 in the rotation direction R relative to the d-axis D. Similar to Embodiment 1, the first magnet 13A and the second magnet 13B are positioned asymmetrically with respect to the d-axis D, with the first angle θ1 [degrees] and the second angle θ2 [degrees] with respect to the d-axis D satisfying θ1 = θ2 < 90 degrees ... (Equation 1).

[0097] In the rotor 52 of Embodiment 3, when the shortest distance between the first magnet 13A and the rotation center O of the rotor core 23 is L2a [mm] in an orthogonal plane, and the shortest distance between the second magnet 13B and the rotation center O of the rotor core 23 is L2b [mm], the shortest distances L2a and L2b satisfy L2a < L2b ... (Equation 5).

[0098] In other words, the first magnet 13A and the second magnet 13B have different radial arrangements on the rotor core 23. To put it another way, the rotor 51 of Embodiment 2 corresponds to an arrangement in which, of the first magnet 13A and the second magnet 13B which are arranged symmetrically with respect to the d-axis D in an orthogonal plane, the second magnet 13B is shifted along the d-axis D toward the radially outer side of the rotor core 23, that is, toward the outer magnetic pole surface 29 side of the rotor core 23.

[0099] (Effects of Example 3) As described above, in the rotor 52 of Example 3, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, so the path of the magnetic flux passing through the outer surface 29 of the magnetic pole can be adjusted, and the effective magnetic flux passing through the permanent magnet 13 (second magnet 13B) on one side with respect to the d-axis D can be made greater than the effective magnetic flux passing through the permanent magnet 13 (first magnet 13A) on the other side with respect to the d-axis D. Also, in Example 3, as in Example 1, the first angle θ1 of the first magnet 13A and the second angle θ2 of the second magnet 13B satisfy equation 1 (θ1 = θ2 < 90 degrees), so that a difference in magnetization rate and demagnetization rate occurs between the first magnet 13A and the second magnet 13B which are arranged on both sides of the d-axis D in the magnetic pole section 11.

[0100] The following describes Modifications 1 to 3, in which the presence or absence of a non-magnetic portion in the magnetic pole portion 11 of the rotor core 23 differs from that of Example 1. In Modifications 1 to 3, the first magnet 13A and the second magnet 13B of the magnetic pole portion 11 satisfy the above-described formula 6 (a > b) and are arranged asymmetrically with respect to the d-axis D, similar to Example 1.

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

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

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

[0104] In Modification 1, as in Embodiment 1, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole. This makes the effective magnetic flux passing through one permanent magnet 13 (second magnet 13B) with respect to the d-axis D greater than the effective magnetic flux passing through the other permanent magnet 13 (first magnet 13A) with respect to the d-axis D, and also suppresses the occurrence of differences in magnetization and demagnetization rates between the first magnet 13A and the second magnet 13B, which are arranged on both sides of the d-axis D in the magnetic pole section 11. In Modification 1, there is a front non-magnetic section 20 and a rear non-magnetic section 30, but there may be only one of the non-magnetic sections, and the effect of restricting short circuits of the magnetic flux as described above can be obtained.

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

[0106] Figure 18 is a plan view showing the magnetic field lines in Modified Example 2. As shown in Figure 18, in the magnetic pole portion 11 of Modified Example 2, the effective magnetic flux passing through the two permanent magnets 13 provided in one magnetic pole portion 11 is different from that of the other.

[0107] In the modified example 2, as in the first example, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole. This makes the effective magnetic flux passing through one permanent magnet 13 with respect to the d-axis D greater than the effective magnetic flux passing through the other permanent magnet 13 with respect to the d-axis D, and also suppresses the occurrence of differences in magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B, which are arranged on both sides of the d-axis D in the magnetic pole portion 11.

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

[0109] Figure 20 is a plan view showing the magnetic field lines in Modification 3. As shown in Figure 20, in the magnetic pole portion 11 of Modification 2, the effective magnetic flux passing through the two permanent magnets 13 provided in one magnetic pole portion 11 is different from that of the other.

[0110] In the modified example 3, as in the first example, the first magnet 13A and the second magnet 13B are arranged asymmetrically with respect to the d-axis D, which allows for adjustment of the path of the magnetic flux passing through the outer surface 29 of the magnetic pole. This makes the effective magnetic flux passing through one permanent magnet 13 with respect to the d-axis D greater than the effective magnetic flux passing through the other permanent magnet 13 with respect to the d-axis D, and also suppresses the occurrence of differences in magnetization rate and demagnetization rate between the first magnet 13A and the second magnet 13B, which are arranged on both sides of the d-axis D in the magnetic pole portion 11.

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

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

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

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

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

[0116] 1 Electric motor 3 Shaft 11 Magnetic pole section 11N N-pole magnetic pole section 11S S-pole magnetic pole section 13 (13a-13f) Permanent magnet 13A First magnet 13B Second magnet 16, 17 Groove section 21 Rotor 22 Stator 23 Rotor core 24 Stator core 27 Outer surface 29 Magnetic pole outer surface 29-F Front outer surface 29-R Rear outer surface 31 Yoke section 32 Teeth section 51, 52, 53A-53F Rotor 101 Compressor 102 Container 105 Compression section θ1 First angle θ2 Second angle A1 Groove section area A2 Constant diameter area A3 Diameter changing area C1, C2 Angles D d-axis L1a, L1b, L2a, L2b Shortest distance O: Center of rotation Q: Q-axis R: Direction of rotation

Claims

1. A rotor having a rotor core in which a plurality of magnetic pole portions, each provided with a permanent magnet, are arranged circumferentially, wherein, in a plane perpendicular to the rotational centerline of the rotor core, when the line connecting the center of the magnetic pole portion in the circumferential direction and the rotational center of the rotor core is defined as the d-axis, the permanent magnets provided in each magnetic pole portion include a first magnet positioned on one side of the circumferential direction with respect to the d-axis and a second magnet positioned on the other side of the circumferential direction with respect to the d-axis, wherein, in the plane, when the mechanical angle is defined as a first angle formed by the longitudinal direction of the first magnet and the d-axis on the outer circumference of the rotor core as θ1, and the mechanical angle formed by the longitudinal direction of the second magnet and the d-axis on the outer circumference as θ2, the first magnet and the second magnet satisfy θ1 = θ2 < 90 degrees and are arranged asymmetrically with respect to the d-axis.

2. In the plane, one end of the first magnet on the d-axis side in the longitudinal direction is located radially inward of the rotor core than the other end of the first magnet on the longitudinal direction, and in the plane, one end of the second magnet on the d-axis side in the longitudinal direction is located radially inward of the second magnet than the other end of the second magnet on the longitudinal direction. The rotor according to claim 1.

3. The rotor according to claim 1, wherein, in the plane, when the straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center is defined as the q-axis, the distance between the outer surface of the magnetic pole formed on the outer surface of the magnetic pole portion and the rotation center gradually decreases as you move from the d-axis toward the q-axis.

4. The rotor according to claim 1, wherein in the plane, the first magnet and the second magnet are the same shape and of equal size.

5. The rotor according to claim 2, wherein, in the plane, L1a is the shortest distance between the first magnet and the d-axis, and L1b is the shortest distance between the d-axis and the second magnet, and L1a ≠ L1b.

6. The rotor according to claim 5, wherein the first magnet is positioned on the front side of the rotor core in the direction of rotation with respect to the d-axis, the second magnet is positioned on the rear side of the rotor core in the direction of rotation with respect to the d-axis, and the shortest distances L1a and L1b satisfy L1a < L1b.

7. The rotor according to claim 2, wherein, in the plane, L2a is the shortest distance between the first magnet and the center of rotation, and L2b is the shortest distance between the second magnet and the center of rotation, and L2a ≠ L2b.

8. The rotor according to claim 7, wherein the first magnet is positioned on the front side of the rotor core in the direction of rotation with respect to the d axis, the second magnet is positioned on the rear side of the rotor core in the direction of rotation with respect to the d axis, and the shortest distances L2a and L2b satisfy L2a < L2b.

9. The rotor according to claim 6 or 8, wherein the outer circumferential surface of each magnetic pole portion has a front outer circumferential surface located on the front side in the rotational direction with respect to the d axis, and a rear outer circumferential surface located on the rear side in the rotational direction with respect to the d axis, and when the magnetic pole portion is virtually folded back along the d axis in the plane and the front outer circumferential surface is superimposed on the rear outer circumferential surface, the front outer circumferential surface has a smaller diameter outer circumferential surface located inward from the rear outer circumferential surface in the radial direction of the rotor core.

10. The rotor according to claim 6 or 8, wherein the outer circumferential surface of the rotor core has grooves formed between adjacent magnetic pole portions in the circumferential direction, along the rotation center line, and when the q-axis is defined as the straight line connecting the center between adjacent magnetic pole portions in the circumferential direction and the rotation center, the outer circumferential surface of the rotor core has a groove region in which the grooves are formed such that the q-axis passes through the grooves, and the outer circumferential surface of each magnetic pole portion has a constant diameter region formed at a position through which the d-axis passes and at a constant distance from the rotation center, and a diameter-changing region formed between the groove region and the constant diameter region and at a constant distance from the rotation center.

11. An electric motor comprising: a rotor according to claim 1; and a stator having a plurality of teeth arranged on the outer circumference of the rotor.

12. The electric motor according to claim 11, wherein, when m is a natural number, the number of the plurality of magnetic poles is 2m and the number of the plurality of teeth is 3m.

13. A compressor comprising: an electric motor according to claim 11 or 12; a compression unit driven by the electric motor; and a container housing the electric motor and the compression unit.

Images