Rotor and motor

Abstract

Provided are a rotor and a motor which are capable of reducing torque ripples while maintaining an average torque. In this rotor (3), a first circumferential end surface (23) and a second circumferential end surface (24) of each of a plurality of permanent magnets (11) protrude in the circumferential direction from a virtual plane (32) which connects the circumferential edge of an inner end surface (26) and the circumferential edge of an outer end surface (25). The first circumferential end surface (23) and the second circumferential end surface (24) are magnetic pole surfaces, and magnetic pole surfaces of the same pole of two permanent magnets (11), which are adjacent to each other in a circumferential direction (C1) among the plurality of permanent magnets (11), are disposed to face each other in the circumferential direction (C1). The circumferential length (L1) of the outer end surface (25) is shorter than the circumferential length (L2) of the inner end surface (26). In a rotor core (9), a plurality of holes (41), (42) are provided between the permanent magnets which are adjacent to each other in the circumferential direction (C1) of the plurality of permanent magnets (11).

Description

Rotor and motor

[0001] The present disclosure relates to a rotor and an electric motor, and more particularly to a rotor including a plurality of permanent magnets and an electric motor including the rotor.

[0002] Patent Document 1 discloses a rotor having a rotor core and multiple permanent magnets embedded inside the rotor core. One or the other of a pair of circumferential end faces of the permanent magnets protrudes circumferentially beyond a plane connecting the inner and outer ends of the end faces. The rotor core also has a large through-hole that penetrates the permanent magnets in the axial direction between them.

[0003] Japanese Patent No. 6083523

[0004] In the rotor described in Patent Document 1, one or both of a pair of circumferential end faces of the permanent magnets protrude circumferentially beyond the plane connecting the inner and outer ends of the end faces, increasing the volume of the permanent magnets. This increases the magnetic flux density in the rotor, resulting in an increase in the average torque of the motor. However, Patent Document 1 does not address or propose solutions to torque ripple, which can cause vibration and noise.

[0005] The present disclosure has been made in view of the above-mentioned points, and has an object to provide a rotor and an electric motor that can reduce torque ripple while maintaining average torque.

[0006] A rotor according to one aspect of the present disclosure includes a rotor core, a plurality of permanent magnets, and a rotating shaft. The rotor core has a plurality of magnet placement holes arranged circumferentially. The plurality of permanent magnets are respectively placed in the plurality of magnet placement holes. The rotating shaft is fixed to the rotor core and has a rotation center at its axis. Each of the plurality of permanent magnets has an inner end face, an outer end face, and a pair of side faces. The inner end face faces the axis of the rotating shaft. The outer end face faces in the opposite direction from the axis of the rotating shaft. The pair of side faces protrude circumferentially from an imaginary plane connecting the circumferential edge of the inner end face and the circumferential edge of the outer end face. The pair of side faces are magnetic pole faces, and magnetic pole faces of the same polarity of two circumferentially adjacent permanent magnets among the plurality of permanent magnets are arranged facing each other circumferentially. The circumferential length of the outer end face is shorter than the circumferential length of the inner end face. The rotor core has a plurality of holes circumferentially spaced between the plurality of permanent magnets.

[0007] An electric motor according to one aspect of the present disclosure includes the rotor and a stator.

[0008] According to a rotor and an electric motor according to an aspect of the present disclosure, torque ripple can be reduced while maintaining average torque.

[0009] FIG. 1 is a plan view of an electric motor according to a first embodiment. FIG. 2 is a partially enlarged plan view of a rotor of the electric motor according to the first embodiment. FIG. 3 is a perspective view of a permanent magnet of the rotor according to the first embodiment. FIG. 4 is a schematic diagram showing magnetic flux distribution in the electric motor according to the first embodiment. FIG. 5 is a partially enlarged schematic diagram showing magnetic flux distribution in the electric motor according to the first embodiment. FIG. 6 is a partially enlarged plan view of a rotor of an electric motor according to a second embodiment. FIG. 7 is a partially enlarged plan view of a rotor of an electric motor according to a third embodiment.

[0010] (Embodiments) Hereinafter, rotors and electric motors according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, each diagram described in the following embodiments is a schematic diagram, and the ratios of the sizes and thicknesses of the components do not necessarily reflect the actual dimensional ratios. Note that the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0011] (First embodiment) (1) Overview of electric motor An electric motor 1 according to a first embodiment of the present disclosure will be described using Figs. 1 to 3. The electric motor 1 is an inner rotor type motor. Fig. 1 is a plan view of the electric motor 1 according to the first embodiment. Fig. 2 is a partially enlarged plan view of the rotor 3 of the electric motor 1 according to the first embodiment. Fig. 3 is a perspective view of a permanent magnet 11 of the rotor 3 according to the first embodiment.

[0012] As shown in Figure 1, the electric motor 1 has a stator 2 and a rotor 3. In the following description, the direction in which an axis 14 (described below) of a rotating shaft 10 (described below) extends is referred to as the axial direction, and the circumferential direction of the rotor 3 is referred to as the circumferential direction C1. The case viewed from the axial direction is referred to as "in a plan view." The direction from a predetermined position on the electric motor 1 toward the axis is referred to as the "radially inner side." The direction facing away from the axis as viewed from a predetermined position on the electric motor 1 is referred to as the "radially outer side."

[0013] The stator 2 is a stator having a stator core 4 and a plurality of coils 5 (12 in FIG. 1 ). The stator core 4 is a laminated core in which a plurality of electromagnetic steel sheets are stacked in the thickness direction. The stator core 4 has an annular core back 7 and a plurality of teeth 8 (12 in FIG. 1 ), and is formed in a generally cylindrical column shape as a whole. The teeth 8 are arranged at regular intervals along the circumferential direction C1 on the inner peripheral surface of the core back 7 and extend radially inward. The coils 5 correspond to the teeth 8, respectively, and each coil 5 is formed by winding a conductor around the corresponding tooth 8.

[0014] The rotor 3 is an IPM (Interior Permanent Magnet) type rotor in which permanent magnets are embedded inside the rotor core. More specifically, the rotor 3 has a so-called spoke-type rotor structure in which a pair of magnetic pole faces of the magnets are arranged so that they face the circumferential direction. The rotor 3 is arranged radially inside the stator 2 and includes a rotor core 9, a rotating shaft 10, and multiple (ten in FIG. 1 ) permanent magnets 11. The permanent magnets 11 are components that generate magnetic flux that serves as the driving force for the rotor 3, and are magnetized so that the direction of their magnetic poles is along the circumferential direction C1 of the rotor core 9.

[0015] The electric motor 1 operates as follows: Three-phase currents, each having a phase difference of 120° electrical angle, are supplied to the coils 5 via a power supply connection, exciting the stator 2 and generating a rotating magnetic field. This rotating magnetic field interacts with the magnetic field generated by the permanent magnets 11 provided in the rotor 3, generating a rotational torque in the rotor 3, causing the rotor 3 to rotate about the axis 14.

[0016] (2) Rotor The configuration and function of the rotor 3 will be described.

[0017] (2-1) Rotor Core The rotor core 9 is a laminated core in which multiple electromagnetic steel sheets are stacked in the thickness direction. The stacking direction of the multiple electromagnetic steel sheets is along the axis (hereinafter referred to as the axial direction). The rotor core 9 has a circular axial hole 12 and is formed into a cylindrical shape. At the center of the rotor core 9, an axial hole 12 is formed, penetrating the rotor core 9 in the axial direction and opening at both end faces. The rotor core 9 has multiple (10 in FIG. 1 ) outer portions 91 and inner portions 92. The multiple outer portions 91 are aligned along the circumferential direction C1, and magnet arrangement holes 13 are formed between adjacent outer portions 91 in the circumferential direction C1. The inner portion 92 is an annular portion that connects the radially inner ends of the multiple outer portions 91, i.e., the portions of each of the multiple outer portions 91 closest to the axis 14. With the above configuration, multiple magnet arrangement holes 13 are formed aligned along the circumferential direction C1. In this embodiment, the magnet arrangement hole 13 is open on its radially outer side. Also, although the magnet arrangement hole 13 penetrates in the axial direction, it may have a bottom in the axial direction.

[0018] (2-2) Rotating Shaft The rotating shaft 10 is a cylindrical member having an axial center 14 that serves as the center of rotation. The rotating shaft 10 is inserted into the axial hole 12 of the rotor core 9 and fixed therein.

[0019] (2-3) Permanent Magnets The multiple permanent magnets 11 are each inserted into a corresponding one of the multiple magnet placement holes 13 in the rotor core 9 and fixed using an adhesive or the like. A sintered ferrite magnet is used as the permanent magnet 11. The permanent magnet 11 may also be a samarium-cobalt based permanent magnet, a neodymium magnet, or the like.

[0020] The permanent magnet 11 has substantially the same shape and dimensions as the magnet placement hole 13. Therefore, hereinafter, the shape of the permanent magnet 11 will be described in detail, and a description of the shape of the magnet placement hole 13 will be omitted.

[0021] The permanent magnets 11 are roughly rectangular parallelepiped-shaped, and when viewed from above, have the shape of radially elongated spokes (i.e., the longitudinal direction of the permanent magnets 11 is along the radial direction of the rotor 3), and are arranged along the circumferential direction C1.

[0022] The magnetization direction of the permanent magnets 11 is parallel to the circumferential direction C1 of the rotor 3. In other words, two adjacent permanent magnets 11 in the circumferential direction C1 are magnetized so that the two magnetic pole faces facing each other in the circumferential direction C1 have the same polarity. As shown in Figure 2, a magnetic pole center line 31, which is an imaginary line extending radially outward from the axis 14, exists between the two permanent magnets 11, and the two permanent magnets 11 are arranged symmetrically with respect to the magnetic pole center line 31 in a plan view.

[0023] 2 and 3 , the permanent magnet 11 has an upper surface 21, a lower surface 22, a first circumferential end face 23 (side face), a second circumferential end face 24 (side face), an outer end face 25 (radially outer end face), and an inner end face 26 (radially inner end face). In a plan view, the first circumferential end face 23 and the second circumferential end face 24 extend radially, while the outer end face 25 and the inner end face 26 extend in the circumferential direction C1. The lengths of the first circumferential end face 23 and the second circumferential end face 24 are at least two times and at most 20 times the lengths of the outer end face 25 and the inner end face 26. This allows the area of ​​the rotor core 9 to be used effectively.

[0024] The upper surface 21 and the lower surface 22 are flat surfaces and have the same shape in a plan view.

[0025] The first circumferential end face 23 and the second circumferential end face 24 are side faces facing the circumferential direction C1 and also serve as magnetic pole faces.

[0026] The first circumferential end face 23 is a protruding surface that protrudes in the circumferential direction C1 beyond an imaginary plane 32 connecting the inner end and outer end thereof. The second circumferential end face 24 is a protruding surface that protrudes in the circumferential direction C1 beyond an imaginary plane 32 connecting the inner end and outer end thereof. With the above structure, the effective area of ​​the magnetic pole face of the permanent magnet 11 is increased, thereby increasing the amount of magnetic flux and therefore the average torque of the electric motor 1.

[0027] The first circumferential end face 23 has a first curved surface 23A and a first flat surface 23B. The first curved surface 23A extends from the radially outer side toward the radially inner side. The first curved surface 23A is a smoothly curved surface that convex in the circumferential direction C1 and is curved in a plan view. The first flat surface 23B is located radially inward of the first curved surface 23A. The first flat surface 23B is a flat surface that is linear in a plan view. The first flat surface 23B is parallel to the magnetic pole center line 31 in a plan view. This configuration ensures a wide circumferential width in the radially inner portion of the permanent magnet 11, i.e., the portion closer to the axis 14 than the center of the permanent magnet 11. The radial length of the first flat surface 23B is 50% or less of the radial length of the entire first circumferential end face 23.

[0028] The second circumferential end face 24 has a second curved surface 24A and a second flat surface 24B. The second curved surface 24A extends from the radially outer side toward the radially inner side. The second curved surface 24A is a smoothly curved surface that is convex in the circumferential direction C1 and is curved in a plan view. The second flat surface 24B is located radially inward of the second curved surface 24A. The second flat surface 24B is a flat surface that is linear in a plan view. The second flat surface 24B is parallel to the magnetic pole center line 31 in a plan view. This configuration ensures a wide circumferential width of the radially inner portion of the permanent magnet 11. The radial length of the second flat surface 24B is 50% or less of the radial length of the entire second circumferential end face 24.

[0029] The outer end surface 25 is a flat surface and is located radially outward of the permanent magnet 11. The outer end surface 25 extends substantially along the circumferential direction C1 in a plan view.

[0030] The inner end surface 26 is a flat surface and is located radially inward of the permanent magnet 11. The inner end surface 26 extends substantially along the circumferential direction C1 in a plan view.

[0031] The circumferential length L1 of the outer end face 25 is shorter than the circumferential length L2 of the inner end face 26. Specifically, the circumferential length L1 of the outer end face 25 is in the range of 60 to 80% of the circumferential length L2 of the inner end face 26. With the above configuration, the normals of the first circumferential end face 23 and the second circumferential end face 24 face further radially outward. As a result, the magnetic flux emitted from the first curved surface 23A of the first circumferential end face 23 and the second curved surface 24A of the second circumferential end face 24 tends to face radially outward, that is, toward the stator 2. This further improves the torque of the electric motor 1.

[0032] (2-4) Holes Two holes 41, 42 are provided in the rotor core 9 between two adjacent permanent magnets 11 in the circumferential direction C1 among the multiple permanent magnets 11. Each of the two holes 41, 42 is a through hole extending along the axial direction of the rotating shaft 10. The two holes 41, 42 are provided on the outer periphery of the rotor core 9. The holes 41, 42 are aligned along the circumferential direction C1. The holes 41, 42 are significantly smaller than, for example, the magnet arrangement holes 13. For example, the total area of ​​the two holes 41, 42 is 20% or less of the area of ​​one magnet arrangement hole 13. The two holes 41, 42 are provided symmetrically with respect to the magnetic pole center line 31. In this embodiment, the holes 41, 42 are each circular in plan view.

[0033] The magnetic flux distribution in the rotor 3 is shown using Figures 4 and 5. Figure 4 is a schematic diagram showing the magnetic flux distribution in the electric motor 1 of the first embodiment. Figure 5 is a partially enlarged schematic diagram showing the magnetic flux distribution in the electric motor 1 of the first embodiment. Magnetic field lines M emerge from the permanent magnet 11 and extend radially outward from the permanent magnet 11. The magnetic field lines M then branch off to avoid the holes 41 and 42, which have a higher magnetic resistance than the surrounding holes. In other words, the magnetic field lines M branch off into three locations: between the holes 41 and 42, between the permanent magnet 11 and the hole 41, and between the permanent magnet 11 and the hole 42, and each of these serves as a path.

[0034] As described above, by providing the holes 41, 42 between the two permanent magnets 11 of the rotor core 9, multiple paths for magnetic flux can be secured between adjacent permanent magnets 11, thereby reducing torque ripple. Furthermore, when the difference in magnetic flux density between the three locations along the magnetic flux paths (between the holes 41, 42, between the permanent magnet 11 and the hole 41, and between the permanent magnet 11 and the hole 42) is reduced, torque ripple is reduced.

[0035] In particular, since the magnetic flux paths formed by the two holes 41 and 42 are symmetrical with respect to the magnetic pole center line 31, torque ripple is further reduced.

[0036] The two holes 41, 42 will now be described in more detail.

[0037] The two holes 41, 42 are positioned so that the magnetic flux density between the two holes 41, 42 when no load is present is within ±40% of the magnetic flux density between the permanent magnet 11 and the hole closest to this permanent magnet 11. This reduces the difference in magnetic flux density between the multiple magnetic flux paths, thereby reducing torque ripple. Note that the distance between the holes 41, 42 may be ±85% of the distance between the permanent magnet 11 and the hole 41 or hole 42.

[0038] The two holes 41, 42 are provided on the outer periphery of the rotor core 9, i.e., in a region within the rotor core 9 that is farther from the center of the rotor core 9 when viewed from the axis 14. In this way, since the multiple holes 41, 42 are provided at positions away from the axis 14, the flow of magnetic flux in the vicinity of the stator 2 can be adjusted, thereby reducing torque ripple. In particular, in this embodiment, the two holes 41, 42 are arranged near the outer periphery of the rotor core 9, which enhances the above-mentioned effect.

[0039] In this embodiment, the plurality of holes 41, 42 penetrate in the axial direction, which increases the effect of making the magnetic resistance different from that of the surroundings, thereby contributing to reducing torque ripple.

[0040] (Modifications) The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the above-described embodiment are listed below. The modifications described below can be applied in appropriate combinations.

[0041] (1) Modified Examples of Electric Motor The rotor core may be a dust core whose main component is a powder material obtained by compressing a powdered magnetic material.

[0042] (2) Modified Examples of Magnet Arrangement Holes The shapes, numbers, and positions of the magnet arrangement holes and permanent magnets are not limited.

[0043] The side surface of the permanent magnet may be composed of only a curved surface.

[0044] The pair of side surfaces of the permanent magnet may have different shapes.

[0045] All permanent magnets do not have to be the same shape or size.

[0046] (3) Modified Magnets The magnets may be bonded magnets made by mixing and kneading hard magnetic material magnet powder with a binder such as resin or rubber and molding the mixture, or may be sintered magnets made by baking the magnet powder at high temperatures.

[0047] Second Embodiment An electric motor 1 according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a partially enlarged plan view of the rotor 3 of the electric motor 1 according to the second embodiment. Note that the basic configuration and operation of the electric motor 1 according to the second embodiment are the same as those of the electric motor 1 according to the first embodiment, and therefore the following description will focus on the differences.

[0048] Two holes 41A, 42A are provided in the outer portion 91 of the rotor core 9 between two adjacent permanent magnets 11 in the circumferential direction C1 among the plurality of permanent magnets 11. Each of the two holes 41A, 42A is a through hole extending along the axial direction of the rotating shaft 10. The two holes 41A, 42A are provided on the outer periphery of the rotor core 9. The holes 41A, 42A are aligned along the circumferential direction C1. The holes 41A, 42A are significantly smaller than, for example, the magnet arrangement holes 13. The two holes 41A, 42A are provided symmetrically with respect to the magnetic pole center line 31. Each of the holes 41A, 42A is elliptical in plan view. Specifically, the major axes of the holes 41A, 42A are generally along the radial direction, and the minor axes are generally along the circumferential direction C1.

[0049] As described above, by providing holes 41A, 42A between permanent magnets 11 of rotor core 9, the magnetic resistance in those areas increases, ensuring multiple paths for magnetic flux and thereby reducing torque ripple. Furthermore, when the difference in magnetic flux density between the three locations along the magnetic flux paths (between holes 41A, 42A, between permanent magnet 11 and hole 41A, and between permanent magnet 11 and hole 42A) is reduced, torque ripple is reduced.

[0050] The two holes 41A and 42A will now be described in more detail.

[0051] The two holes 41A, 42A are provided at positions where the magnetic flux density between the two holes 41A, 42A when no load is present is within ±40% of the magnetic flux density when no load is present between the permanent magnet 11 and the hole closest to this permanent magnet 11. Therefore, the difference in magnetic flux density between the multiple magnetic flux paths is reduced, thereby reducing torque ripple.

[0052] The two holes 41A, 42A are provided on the outer periphery of the rotor core 9, i.e., in a region within the rotor core 9 that is farther from the center of the rotor core 9 when viewed from the axis 14. In this way, the multiple holes 41A, 42A are provided at positions away from the axis 14, which makes it possible to adjust the flow of magnetic flux near the stator 2 and thereby reduce torque ripple. In particular, in this embodiment, the two holes 41A, 42A are located near the outer periphery of the rotor core 9, which enhances the above-mentioned effect.

[0053] (Third embodiment) An electric motor 1 according to a third embodiment will be described using Fig. 7. Fig. 7 is a partially enlarged plan view of the rotor 3 of the electric motor 1 according to the third embodiment. Note that the basic configuration and operation of the electric motor 1 according to the third embodiment are similar to those of the electric motor 1 according to the first embodiment, and therefore the following description will focus on the differences.

[0054] The outer portion 91 of the rotor core 9 has four holes 41B, 42B, 43B, and 44B between two adjacent permanent magnets 11 in the circumferential direction C1 among the multiple permanent magnets 11. The four holes 41B, 42B, 43B, and 44B are through holes extending along the axial direction of the rotating shaft 10. The four holes 41B, 42B, 43B, and 44B are provided on the outer periphery of the rotor core 9. Each of the holes 41B, 42B, 43B, and 44B is aligned along the circumferential direction C1. The holes 41B and 42B are significantly smaller than, for example, the magnet arrangement holes 13. The pair of holes 41B and 42B and the pair of holes 43B and 44B are symmetrical with respect to the magnetic pole center line 31. The holes 41B, 42B, 43B, and 44B are each circular in plan view.

[0055] As described above, by providing holes 41B, 42B, 43B, and 44B between permanent magnets 11 of rotor core 9, the magnetic resistance in those areas increases, ensuring multiple paths for magnetic flux, thereby reducing torque ripple. Furthermore, when the difference in magnetic flux density at the five locations that form the magnetic flux paths is reduced, torque ripple is more likely to be reduced.

[0056] The four holes 41B, 42B, 43B, and 44B will now be described in more detail.

[0057] The four holes 41B, 42B, 43B, and 44B are provided at positions where the magnetic flux density between the four holes 41B, 42B, 43B, and 44B when no load is present is within ±40% of the magnetic flux density when no load is present between the permanent magnet 11 and the hole closest to this permanent magnet 11. Therefore, the difference in magnetic flux density between the multiple magnetic flux paths is reduced, thereby reducing torque ripple.

[0058] The four holes 41B, 42B, 43B, and 44B are provided on the outer periphery of the rotor core 9, i.e., in a region within the rotor core 9 that is farther from the center of the rotor core 9 when viewed from the axis 14. In this way, since a plurality of holes 41B, 42B, 43B, and 44B are provided at positions farther from the axis 14, the flow of magnetic flux in the vicinity of the stator 2 can be adjusted, thereby reducing torque ripple. In particular, in this embodiment, the four holes 41B, 42B, 43B, and 44B are arranged near the outer periphery of the rotor core 9, which enhances the above-mentioned effect.

[0059] (Modification of Holes) The number of holes may be three, or may be five or more.

[0060] The holes do not need to penetrate the rotor core 9 .

[0061] The shape of the holes is not limited to those in the first to third embodiments. For example, the holes may be polygonal or may have a shape obtained by combining curved and straight lines.

[0062] The holes are preferably arranged in the circumferential direction, but may be provided at different radial positions.

[0063] The plurality of holes do not all have to be the same shape or size, and may include holes of different shapes and sizes.

[0064] (Aspects) The present specification discloses the following aspects.

[0065] The rotor (3) according to the first aspect includes a rotor core (9), a plurality of permanent magnets (11), and a rotating shaft. The rotor core (9) has a plurality of magnet arrangement holes (13) arranged in a circumferential direction (C1). The plurality of permanent magnets (11) are respectively arranged in the plurality of magnet arrangement holes (13). The rotating shaft is fixed to the rotor core (9) and has an axial center (14) as its rotation center. Each of the plurality of permanent magnets (11) has an inner end face (26), an outer end face (25), and a pair of side faces (23, 24). The inner end face (26) faces the axial center (14) of the rotating shaft (10) in a plane having a normal that is a straight line coincident with the axial center (14) of the rotating shaft (10). The outer end surface (25) faces away from the axis (14) of the rotating shaft (10) in a plane normal to a straight line coinciding with the axis (14) of the rotating shaft (10). The pair of side surfaces (23, 24) protrude circumferentially from an imaginary plane (32) connecting the circumferential edges of the inner end surface (26) and the outer end surface (25). The pair of side surfaces (23, 24) are magnetic pole surfaces, and the magnetic pole surfaces of the same polarity of two permanent magnets (11) adjacent in the circumferential direction (C1) are arranged facing each other in the circumferential direction (C1). The circumferential length (L1) of the outer end surface (25) is shorter than the circumferential length (L2) of the inner end surface (26). The rotor core (9) is provided with a plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) between adjacent permanent magnets (11) in the circumferential direction (C1).

[0066] According to this aspect, because the pair of side surfaces (23, 24) protrude outward in the circumferential direction, the effective area of ​​the magnetic pole face of the permanent magnet (11) is increased, thereby increasing the amount of magnetic flux and, therefore, increasing the average torque of the electric motor (1). Furthermore, the further radially outward the pair of side surfaces (23, 24) are, the more radially outward the normals of the pair of side surfaces (23, 24) are. As a result, the magnetic flux emanating from the portion of the pair of side surfaces (23, 24) opposite the axis (14) is likely to be directed away from the axis (14). This can further improve the torque of the electric motor (1). Furthermore, by providing multiple holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B), the location of the magnetic flux flow can be adjusted. As a result, torque ripple can be reduced while maintaining average torque.

[0067] In the rotor (3) according to the second aspect, in the first aspect, the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are arranged symmetrically with respect to the magnetic pole center line (31) between the circumferentially adjacent permanent magnets of the plurality of permanent magnets (11).

[0068] According to this aspect, the magnetic flux paths formed by the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are symmetrical with respect to the magnetic pole center line (31), thereby reducing torque ripple.

[0069] In the rotor (3) according to the third aspect, in the first or second aspect, the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are provided at positions where the magnetic flux density in the no-load state between the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) is ±40% or less of the magnetic flux density in the no-load state between one permanent magnet (11) among the plurality of permanent magnets (11) and the hole closest to the permanent magnet (11).

[0070] According to this aspect, the difference in magnetic flux density in the magnetic flux paths formed by the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) is reduced, thereby reducing torque ripple.

[0071] In the rotor (3) according to the fourth aspect, in any of the first to third aspects, the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are provided in a region in the rotor core (9) farther from the center of the rotor core (9) as viewed from the axis (14).

[0072] According to this aspect, since the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are provided at positions away from the axis, the flow of magnetic flux in the vicinity of the stator (2) can be adjusted, thereby reducing torque ripple.

[0073] In the rotor (3) according to the fifth aspect, in any one of the first to fourth aspects, the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) are through holes extending along the axial direction of the rotating shaft (10).

[0074] According to this aspect, since the plurality of holes (41, 42, 41A, 42A, 41B, 42B, 43B, 44B) penetrate in the axial direction, the effect of making the magnetic resistance different from the surroundings is enhanced, and as a result, torque ripple can be reduced.

[0075] In the rotor (3) according to the sixth aspect, in any one of the first to fifth aspects, each of the pair of side surfaces (23, 24) has a curved surface or a combination of a curved surface and a flat surface.

[0076] According to this aspect, by adjusting the shape of the pair of side surfaces, the volume of the permanent magnet (11) and the orientation of the side surfaces can be appropriately set, and as a result, torque ripple can be reduced while maintaining the average torque.

[0077] In the rotor (3) according to the seventh aspect, in the sixth aspect, each of the pair of side surfaces (23, 24) has a curved surface (23A, 24A) that is convex outward in the circumferential direction, and a flat surface (23B, 24B) that is arranged on the axial center (14) side of the curved surface (23A, 24A).

[0078] According to this aspect, since each of the pair of side surfaces (23, 24) has a flat surface (23B, 24B), the portions of the side surfaces (23, 24) on the axis (14) side can be brought close to each other in the circumferential direction (C1), and as a result, the volume of the permanent magnet (11) can be increased.

[0079] In the rotor (3) according to the eighth aspect, in the seventh aspect, the planes (23B, 24B) are parallel to the magnetic pole center line (31) between the multiple permanent magnets (11) when viewed along the axial direction of the rotation shaft (10).

[0080] According to this aspect, the planes (23B, 24B) of the pair of side surfaces (23, 24) are parallel to the magnetic pole center line (31), so that the portions of the side surfaces (23, 24) on the axis (14) side can be brought close to each other in the circumferential direction (C1), thereby increasing the volume of the permanent magnet (11).

[0081] An electric motor (1) according to a ninth aspect includes a rotor (3) according to any one of the first to eighth aspects and a stator (2).

[0082] According to this aspect, the torque ripple can be reduced while maintaining the average torque.

[0083] The rotor and motor of the present disclosure can reduce torque ripple while maintaining average torque, making the rotor and motor of the present disclosure industrially useful.

[0084] 1: Electric motor 2: Stator 3: Rotor 9: Rotor core 10: Rotating shaft 11: Permanent magnet 13: Magnet placement hole 14: Axial center 23: First circumferential end surface (side surface) 23A: First curved surface 23B: First plane 24: Second circumferential end surface (side surface) 24A: Second curved surface 24B: Second plane 25: Outer end face 26: Inner end face 31: Magnetic pole center line 32: Virtual plane 41, 41A, 41B, 42, 42A, 42B, 43B, 44B: Hole C1: Circumferential direction

Claims

1. a rotor core having a plurality of magnet arrangement holes arranged in a circumferential direction; A plurality of permanent magnets respectively arranged in the plurality of magnet arrangement holes; A rotating shaft fixed to the rotor core and having an axis center as a rotation center, Each of the plurality of permanent magnets is an inner end surface facing the axis of the rotating shaft; an outer end surface facing away from the axis of the rotating shaft; a pair of side surfaces protruding in a circumferential direction from imaginary planes connecting a circumferential edge of the inner end surface and a circumferential edge of the outer end surface, The pair of side surfaces are magnetic pole faces, and the magnetic pole faces of the same polarity of two circumferentially adjacent permanent magnets among the plurality of permanent magnets are arranged to face each other in the circumferential direction, a circumferential length of the outer end surface is shorter than a circumferential length of the inner end surface, The rotor core is provided with a plurality of holes between adjacent permanent magnets in the circumferential direction of the plurality of permanent magnets. Rotor.

2. The plurality of holes are provided symmetrically with respect to a magnetic pole center line between the circumferentially adjacent permanent magnets. The rotor according to claim 1 .

3. the plurality of holes are provided at positions such that a magnetic flux density under no load between the plurality of holes is ±40% or less of a magnetic flux density under no load between one of the permanent magnets adjacent in the circumferential direction and the hole closest to the one permanent magnet, A rotor according to claim 1 or 2.

4. The plurality of holes are provided in the rotor core at positions farther from the center of the rotor core as viewed from the axis. A rotor according to claim 1 or 2.

5. The plurality of holes are through holes extending along the axial direction of the rotation shaft. A rotor according to claim 1 or 2.

6. Each of the pair of side surfaces has a curved surface or a combination of a curved surface and a flat surface. A rotor according to claim 1 or 2.

7. Each of the pair of side surfaces has a curved surface that is convex in the circumferential direction and a flat surface that is disposed on the axial center side of the curved surface. The rotor according to claim 6.

8. The plane is parallel to a magnetic pole center line between the permanent magnets adjacent in the circumferential direction when viewed along the axial direction of the rotation shaft. A rotor according to claim 7.

9. A rotor according to claim 1 or 2; A stator; Equipped with Electric motor.