Rotor and motor

Abstract

To provide a rotor that makes it difficult for irreversible demagnetization to occur in a magnetic pole part while ensuring a torque of a motor.SOLUTION: The rotor includes a rotor body 2 that rotates around a rotation axis and a plurality of magnetic pole parts 4 arranged in the rotor body 2. Each of the magnetic pole parts 4 includes a first magnet 41 and a second magnet 42 disposed inside the first magnet 41 in the radial direction around the rotation axis. In the rotor body 2, there are formed a first arrangement hole 21 in which the first magnet 41 is disposed, and a second arrangement hole 22 in which the second magnet 42 is disposed. The rotor body 2 has a dividing wall 29 that divides the second arrangement hole 22. The first arrangement hole 21 is a single undivided hole. When an intersection of the outer circumference of the rotor body 2 and a d-axis of the magnetic pole part 4 is taken as a reference point P, a dimension t1a of a part of the first magnet 41 located between the reference point P and the dividing wall 29 in a magnetization direction is greater than a dimension t1b of the other parts of the first magnet 41 in the magnetization direction.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The technology disclosed herein relates to a rotor and a motor.

Background Art

[0002] Patent Document 1 discloses a motor. The motor includes a rotor and a stator. The rotor is of an embedded magnet type and includes a rotor core and a plurality of magnetic pole portions provided on the rotor core. The magnetic pole portion has two magnets arranged in the radial direction of the rotor core.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] By the way, in the rotor disclosed in Patent Document 1, there is a high possibility that irreversible demagnetization of the magnetic pole portion occurs due to a counter magnetic field such as a rotating magnetic field formed by the stator.

[0005] The technology disclosed herein has been made in view of such a point, and the object thereof is to make it difficult for irreversible demagnetization of the magnetic pole portion to occur while ensuring the torque of the motor.

[0006] The rotor disclosed herein includes a rotor body that rotates around a rotation axis, and a plurality of magnetic pole portions that are arranged in a circumferential direction centered on the rotation axis in the rotor body and form alternately different magnetic poles in the circumferential direction. The magnetic pole portion includes a first magnet and a second magnet disposed inside the first magnet in a radial direction centered on the rotation axis. In the rotor body, a first arrangement hole for disposing the first magnet and a second arrangement hole for disposing the second magnet are formed. The rotor body has a partition wall that connects a portion of the second arrangement hole located on the first magnet side and a portion of the second arrangement hole located on the side opposite to the first magnet to divide the second arrangement hole. The first arrangement hole is one undivided hole. When a reference point is a point of intersection of the outer peripheral surface of the rotor body with the d-axis of the magnetic pole portion, a dimension of a magnetization direction of a portion of the first magnet located between the reference point and the partition wall is larger than a dimension of a magnetization direction of another portion of the first magnet.

[0007] The motor disclosed herein includes the rotor and a stator that drives the rotor.

[0008] The rotor can prevent irreversible demagnetization of the magnetic pole portion while ensuring the torque of the motor.

[0009] The motor can prevent irreversible demagnetization of the magnetic pole portion while ensuring the torque.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

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Figure 10

Figure 11

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Figure 14

Figure 15

[0011] Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. FIG. 1 shows a motor 100 according to an embodiment. The motor 100 includes a rotor 1 that rotates about a predetermined rotation axis X, and a stator 6 that rotates the rotor 1 about the rotation axis X. Permanent magnets are embedded in the rotor 1. That is, the motor 100 is an IPM (Interior Permanent Magnet) motor. The motor 100 may further include a motor case 7. The motor case 7 houses the rotor 1 and the stator 6. The stator 6 is fixed to the motor case 7. The rotor 1 is rotatably supported by the motor case 7.

[0012] Hereinafter, the direction in which the rotation axis X extends is referred to as the "rotation axis direction". The circumferential direction centered on the rotation axis X is simply referred to as the "circumferential direction". The radial direction centered on the rotation axis X is simply referred to as the "radial direction". The side facing the rotation axis X in the radial direction is referred to as the "radial inner side". The side opposite to the rotation axis X in the radial direction is referred to as the "radial outer side". A cross-section orthogonal to the rotation axis X is referred to as an "orthogonal cross-section". The shape of each element of the motor 100 in the orthogonal cross-section is simply referred to as the "cross-sectional shape".

[0013] The stator 6 includes a stator core 61 and a winding 62. The stator core 61 is a soft magnetic material. The stator core 61 is formed of, for example, a plurality of laminated electromagnetic steel sheets.

[0014] The stator core 61 is formed in an annular shape. Specifically, the stator core 61 is formed in a cylindrical shape. The stator core 61 is fixed to the motor case 7. A plurality of teeth 61a protruding toward the inside of the stator core 61 are formed on the stator core 61. The plurality of teeth 61a are arranged at intervals in the circumferential direction on the stator core 61. The winding 62 is wound around the plurality of teeth 61a. When an electric current is supplied to the winding 62, the stator 6 forms a rotating magnetic field that rotates the rotor 1.

[0015] The rotor 1 includes a rotor body 2 that rotates around the rotation axis X, and a plurality of magnetic pole portions 4 that are arranged in the circumferential direction on the rotor body 2 and form alternately different magnetic poles in the circumferential direction. In this example, the rotor 1 includes six magnetic pole portions 4 arranged at equal intervals in the circumferential direction. The rotor 1 may further include a plurality of auxiliary magnets 5a, 5b separately from the magnetic pole portions 4. In this example, the rotor 1 includes six auxiliary magnets 5a and six auxiliary magnets 5b.

[0016] At least a part of the rotor body 2 is formed of a soft magnetic material. The rotor body 2 has magnetic salient poles. The rotor body 2 generates reluctance torque in the rotating magnetic field formed by the stator 6. The rotor body 2 includes a rotor core 20 and a shaft 11.

[0017] The rotor core 20 is made of a soft magnetic material. The rotor core 20 is formed, for example, from a plurality of electromagnetic steel sheets laminated on one another. The rotor core 20 is formed in an annular shape surrounding the rotation axis X. Specifically, the rotor core 20 is formed in a cylindrical shape concentric with the stator core 61. The outer peripheral surface 28 of the rotor core 20 forms the outer peripheral surface of the rotor body 2. The cross-sectional shape of the rotor core 20 is the same over the entire length of the rotor core 20 in the rotation axis direction. An air gap 10 is formed between the outer peripheral surface 28 of the rotor core 20 and the inner peripheral surface of the stator core 61.

[0018] The shaft 11 is fitted inside the rotor core 20. The shaft 11 is fixed to the rotor core 20. The axis of the shaft 11 coincides with the rotation axis X. The shaft 11 is rotatably supported by the motor case 7 via a bearing or the like. The rotor core 20 rotates about the rotation axis X together with the shaft 11. The shaft 11 is made of a soft magnetic material.

[0019] A plurality of magnetic pole portions 4 are provided on the rotor core 20. The plurality of magnetic pole portions 4 generate a magnetic torque in the rotating magnetic field formed by the stator 6. The plurality of magnetic pole portions 4 are arranged at equal intervals in the circumferential direction.

[0020] FIG. 2 is an enlarged cross-sectional view of the motor 100. FIG. 3 is an enlarged cross-sectional view of the rotor 1. Each magnetic pole portion 4 of the rotor 1 has a line-symmetric shape centered on a symmetry axis extending in the radial direction. Each magnetic pole portion 4 includes a plurality of magnets. Specifically, each magnetic pole portion 4 includes two magnets, a first magnet 41 and a second magnet 42. The first magnet 41 and the second magnet 42 are arranged side by side with a space therebetween in the radial direction. The second magnet 42 is arranged inside the first magnet 41 in the radial direction. The first magnet 41 and the second magnet 42 are formed in a layered manner. That is, the magnetic pole portion 4 has two magnet layers of the first magnet 41 and the second magnet 42.

[0021] Each of the first magnet 41 and the second magnet 42 is a bonded magnet. The bonded magnet is formed of a magnet material including magnet powder and a binder that binds the magnet powder. The magnet powder is, for example, powder of a neodymium magnet, a samarium iron nitrogen-based magnet, a samarium cobalt-based magnet, a ferrite magnet, an alnico magnet, or the like, or a mixture of two or more of these powders. The binder is, for example, a thermosetting resin such as an epoxy resin, a thermoplastic resin such as a polyamide resin, or rubber.

[0022] In the rotor core 20, a first arrangement hole 21 in which the first magnet 41 is arranged and a second arrangement hole 22 in which the second magnet 42 is arranged are formed. Each of the first arrangement hole 21 and the second arrangement hole 22 is a hole penetrating the rotor core 20 in the rotation axis direction. The cross-sectional shape 3 of the first arrangement hole 21 is the same as the cross-sectional shape of the first magnet 41. The cross-sectional shape of the second arrangement hole 22 is the same as the cross-sectional shape of the second magnet 42.

[0023] The first magnet 41 and the second magnet 42 are formed, for example, by insert molding. Specifically, the first magnet 41 and the second magnet 42 are formed by injecting the magnet material of the bonded magnet into a mold in which the rotor core 20 is accommodated. The first magnet 41 and the second magnet 42 are each a cured product of the magnet material filled in the first arrangement hole 21 and the second arrangement hole 22 of the rotor core 20, respectively. The first arrangement hole 21 is filled with the first magnet 41. The second arrangement hole 22 is filled with the second magnet 42.

[0024] Each of the first magnet 41 and the second magnet 42 is formed in a plate shape extending along the rotation axis X. The cross-sectional shape of the first magnet 41 is the same over the entire length of the first magnet 41 in the rotation axis direction. The cross-sectional shape of the second magnet 42 is the same over the entire length of the second magnet 42 in the rotation axis direction.

[0025] The cross-sectional shape of each of the first magnet 41 and the second magnet 42 is linear. That is, the cross-sectional shape of the first magnet 41 has a shape extending along a predetermined first reference line R1. The cross-sectional shape of the second magnet 42 has a shape extending along a predetermined second reference line R2. Each of the first reference line R1 and the second reference line R2 extends in a direction intersecting a predetermined reference line R that passes through the rotation axis X and extends in the radial direction. Hereinafter, in the first magnet 41, the direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the first reference line R1 is also referred to as the "thickness direction". In the second magnet 42, the direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the second reference line R2 is also referred to as the "thickness direction".

[0026] The first magnet 41 has two end portions 41a and 41b in the direction in which the first reference line R1 extends, and an intermediate portion 41c located between the two end portions 41a and 41b. Hereinafter, when distinguishing between the two end portions 41a and 41b, they are respectively referred to as the "first end portion 41a" and the "second end portion 41b". The second magnet 42 has two end portions 42a and 42b in the direction in which the second reference line R2 extends, and an intermediate portion 42c located between the two end portions 42a and 42b. Hereinafter, when distinguishing between the two end portions 42a and 42b, they are respectively referred to as the "first end portion 42a" and the "second end portion 42b".

[0027] Note that the intermediate portion 41c does not refer to all of the remaining portions of the first magnet 41 excluding the two end portions 41a and 41b, but refers to at least a part of the remaining portions excluding the two end portions 41a and 41b. The intermediate portion 41c may or may not include the center in the direction in which the first reference line R1 extends in the first magnet 41. The intermediate portion 42c does not refer to all of the remaining portions of the second magnet 42 excluding the two end portions 42a and 42b, but refers to at least a part of the remaining portions excluding the two end portions 42a and 42b. The intermediate portion 42c may or may not include the center in the direction in which the second reference line R2 extends in the second magnet 42.

[0028] The first magnet 41 is curved or bent so as to be concave toward the inner side in the radial direction. The intermediate portion 41c is located more radially inward than the two end portions 41a and 41b. That is, the first magnet 41 is curved or bent such that the two end portions 41a and 41b approach the outer peripheral surface 28 of the rotor core 20 more than the intermediate portion 41c. Specifically, the cross-sectional shape of the first magnet 41 is substantially U-shaped. That is, the first magnet 41 is formed in an arc shape that curves so as to be concave toward the inner side in the radial direction. The cross-sectional shape of the first magnet 41 is a line-symmetric shape centered on a symmetry axis extending in the radial direction.

[0029] Similarly, the second magnet 42 is curved or bent so as to be concave toward the inner side in the radial direction. The intermediate portion 42c is located more radially inward than the two end portions 42a and 42b. That is, the second magnet 42 is curved or bent such that the two end portions 42a and 42b approach the outer peripheral surface 28 of the rotor core 20 more than the intermediate portion 42c. Specifically, the cross-sectional shape of the second magnet 42 is substantially U-shaped. That is, the second magnet 42 is formed in an arc shape that curves so as to be concave toward the inner side in the radial direction. The cross-sectional shape of the second magnet 42 is a line-symmetric shape centered on a symmetry axis extending in the radial direction. The symmetry axis that is the center of the line-symmetric shape of the second magnet 42 coincides with the symmetry axis that is the center of the line-symmetric shape of the first magnet 41.

[0030] FIG. 4 is an explanatory view showing an enlarged cross-section of the rotor 1. In FIG. 4, for clarity of the lines used for explanation, the hatching representing the cross-section is omitted. The first magnet 41 is magnetized in a direction intersecting the first reference line R1. Specifically, as shown by the dashed arrow in FIG. 4, the first magnet 41 is magnetized in a direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the first reference line R1. That is, the magnetization direction of the first magnet 41 is the thickness direction of the first magnet 41. The second magnet 42 is magnetized in a direction intersecting the second reference line R2. Specifically, as shown by the dashed arrow in FIG. 4, the second magnet 42 is magnetized in a direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the second reference line R2. That is, the magnetization direction of the second magnet 42 is the thickness direction of the second magnet 42.

[0031] The direction of the magnetic flux generated by the magnetic pole portion 4 is determined by the magnetic field formed by the first magnet 41 and the magnetic field formed by the second magnet 42. Specifically, as shown in FIGS. 1 and 3, each magnetic pole portion 4 has a d-axis extending in the direction of the magnetic flux created by the magnetic pole portion 4 and a q-axis that is electrically and magnetically orthogonal to the d-axis.

[0032] The d-axis is the magnetic pole center line of the magnetic pole portion 4 and extends in the radial direction. In this example, in the orthogonal cross-section, the d-axis coincides with the central axis of the shape of the magnetic pole portion 4. Specifically, the d-axis coincides with the axis of symmetry that is the center of the line-symmetric shape of the first magnet 41. The d-axis also coincides with the axis of symmetry that is the center of the line-symmetric shape of the second magnet 42.

[0033] The q-axis is an axis that is shifted by 90 degrees in the electrical angle with respect to the d-axis. The q-axis extends in the radial direction and passes between the circumferentially adjacent magnetic pole portions 4 in the orthogonal cross-section. In this example, the q-axis passes through the center between the circumferentially adjacent magnetic pole portions 4 in the orthogonal cross-section.

[0034] The first magnet 41 is continuous over the direction in which the first reference line R1 extends. That is, the first magnet 41 is not divided. In contrast, the second magnet 42 is divided midway in the direction in which the second reference line R2 extends.

[0035] The rotor core 20 has a dividing wall 29 that divides the second placement hole 22. The dividing wall 29 connects the portion of the rotor core 20 located on the first magnet 41 side of the second placement hole 22 and the portion of the rotor core 20 located on the side opposite to the first magnet 41 of the second placement hole 22. In other words, the dividing wall 29 connects the portion inside the radial direction of the second placement hole 22 (that is, the portion opposite to the outer peripheral surface 28) and the portion outside the radial direction of the second placement hole 22 (that is, the portion on the outer peripheral surface 28 side).

[0036] The dividing wall 29 is disposed at the center in the direction in which the second reference line R2 extends in the second arrangement hole 22. Specifically, the dividing wall 29 is located on the d-axis of the magnetic pole portion 4. In the orthogonal cross-section, the dividing wall 29 extends in a direction intersecting the second reference line R2, specifically, in a direction orthogonal to the second reference line R2. That is, the dividing wall 29 extends in the radial direction. The second arrangement hole 22 is divided by the dividing wall 29 into two dividing holes 22a and 22b arranged in the direction in which the second reference line R2 extends.

[0037] The second magnet 42 is divided by the dividing wall 29 into two magnet pieces 48 and 49 arranged in the direction in which the second reference line R2 extends. The two magnet pieces 48 and 49 are respectively disposed in the two dividing holes 22a and 22b. The dividing holes 22a and 22b are respectively filled with the magnet pieces 48 and 49.

[0038] As shown in FIG. 4, when the intersection point of the outer peripheral surface 28 of the rotor core 20 with the d-axis of the magnetic pole portion 4 is used as the reference point P, the dimension t1a of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the dividing wall 29 is larger than the dimension t1b of the magnetization direction of the other portion of the first magnet 41. That is, the first magnet 41 has at least one thin portion 44 and a thick portion 45 having a magnetization direction dimension t1a larger than the magnetization direction dimension t1b of the thin portion 44. Specifically, the first magnet 41 has two thin portions 44 spaced apart in the direction in which the first reference line R1 extends and one thick portion 45 located between the two thin portions 44.

[0039] The two thin portions 44 are located on both sides of the first magnet 41 with respect to the virtual straight line S connecting the reference point P and the dividing wall 29. The dimension t1a of the magnetization direction of each thin portion 44 is constant over the direction in which the first reference line R1 extends. The dimension t1a is also the minimum value of the magnetization direction dimension in the first magnet 41.

[0040] The thick portion 45 is located at the central portion of the first magnet 41 in the direction in which the first reference line R1 extends. Specifically, a protrusion 46 protruding toward the reference point P is formed at the portion of the first magnet 41 that intersects the virtual straight line S. The protrusion 46 has a semi-circular cross-sectional shape. The portion of the first magnet 41 where the protrusion 46 is formed is the thick portion 45. The dimension t1a is the maximum value of the dimension in the magnetization direction in the thick portion 45. The dimension t1a is also the maximum value of the dimension in the magnetization direction in the first magnet 41.

[0041] The dimension t2 of the magnetization direction of the second magnet 42 is constant over the direction in which the second reference line R2 extends. The dimension t2 is also the minimum value, the maximum value, and the average value of the dimension in the magnetization direction in the second magnet 42.

[0042] The average value of the dimension in the magnetization direction of the second magnet 42 (i.e., the average value over the direction of the second reference line R2) is larger than the average value of the dimension in the magnetization direction of the first magnet 41 (i.e., the average value over the direction of the first reference line R1). The minimum value of the dimension in the magnetization direction of the second magnet 42 (i.e., the dimension t2) is larger than the minimum value of the dimension in the magnetization direction of the first magnet 41 (i.e., the dimension t1b). The volume of the second placement hole 22 is larger than the volume of the first placement hole 21. Therefore, the volume of the second magnet 42 is larger than the volume of the first magnet 41, and the mass of the second magnet 42 is larger than the mass of the first magnet 41.

[0043] As shown in FIG. 3, the two end portions 41a and 41b of the first magnet 41 and the two end portions 42a and 42b of the second magnet 42 are arranged close to the outer peripheral surface 28 of the rotor body 2. That is, the two end portions 41a and 41b of the first magnet 41 and the two end portions 42a and 42b of the second magnet 42 are arranged to face the outer peripheral surface 28 from the radially inner side. The two end portions 41a and 41b of the first magnet 41 are arranged between the two end portions 42a and 42b of the second magnet 42 in the circumferential direction.

[0044] Notches 24 are formed in portions of the rotor core 20 that are located radially outside the two end portions 41a and 41b of the first magnet 41. Notches 25 are formed in portions of the rotor core 20 that are located radially outside the two end portions 42a and 42b of the second magnet 42. The notches 24 and 25 are formed on the outer peripheral surface 28 of the rotor core 20. The notches 24 and 25 open toward the radially outer side of the rotor core 20. The notches 24 and 25 are formed over the entire length of the rotor core 20 in the rotational axis direction.

[0045] The cross-sectional shape of the notches 24 and 25 is, for example, rectangular. By forming the notch 24 on the outer peripheral surface 28 of the rotor core 20, the two end portions 41a and 41b of the first magnet 41 are located radially inwardly away from the outer peripheral surface 28 of the rotor body 2. By forming the notch 25 on the outer peripheral surface of the rotor core 20, the two end portions 42a and 42b of the second magnet 42 are located radially inwardly away from the outer peripheral surface 28 of the rotor body 2. The rotor core 20 has portions 33 and 34 that are located radially outside the two end portions 41a and 42b of the first magnet 41. The rotor core 20 has portions 35 and 36 that are located radially outside the two end portions 42a and 42b of the second magnet 42.

[0046] The first end portion 41a of the first magnet 41 and the first end portion 42a of the second magnet 42 are adjacent to each other in the circumferential direction. The second end portion 41b of the first magnet 41 and the second end portion 42b of the second magnet 42 are adjacent to each other in the circumferential direction. A portion 31 between the first end portion 41a and the first end portion 42a of the rotor core 20 protrudes radially outward more than the portions 33, 34, 35, and 36 of the rotor core 20. A portion 32 between the second end portion 41b and the second end portion 42b of the rotor core 20 protrudes radially outward more than the portions 33, 34, 35, and 36 of the rotor core 20. In this example, the portion between the notch 24 and the notch 25 of the rotor core 20 is a protruding portion that protrudes toward the radially outer side.

[0047] As shown in FIG. 1, a plurality of auxiliary magnets 5a are arranged in the circumferential direction on the rotor body 2. One auxiliary magnet 5a is provided for each magnetic pole portion 4. The auxiliary magnet 5a is disposed radially inside the second magnet 42 of the corresponding magnetic pole portion 4. Specifically, the auxiliary magnet 5a is disposed between the partition wall 29 and the rotation axis X. The auxiliary magnet 5a is disposed on the d-axis of the corresponding magnetic pole portion 4.

[0048] A plurality of auxiliary magnets 5b are arranged in the circumferential direction on the rotor body 2. The auxiliary magnet 5b is disposed between the second magnets 42 of the adjacent magnetic pole portions 4 in the circumferential direction. That is, the auxiliary magnet 5b is an interpolar magnet disposed between the adjacent magnetic pole portions 4. Specifically, the auxiliary magnet 5b is disposed on the q-axis of the magnetic pole portion 4. An auxiliary magnet 5a is disposed between the auxiliary magnets 5b adjacent in the circumferential direction. The auxiliary magnet 5a and the auxiliary magnet 5b are separated in the circumferential direction.

[0049] The auxiliary magnets 5a and 5b are bonded magnets. The auxiliary magnets 5a and 5b are formed of, for example, the same material as the first magnet 41 and the second magnet 42.

[0050] As shown in FIG. 3, the rotor core 20 is formed with arrangement holes 30 in which the auxiliary magnets 5a and 5b are arranged. The arrangement holes 30 penetrate the rotor core 20 in the rotation axis direction. The cross-sectional shape of the arrangement holes 30 is the same as the cross-sectional shape of the auxiliary magnets 5a and 5b.

[0051] The auxiliary magnets 5a and 5b are formed, for example, by insert molding in the same manner as the first magnet 41 and the second magnet 42. That is, the auxiliary magnets 5a and 5b are formed by injecting a magnet material that becomes a bonded magnet into a mold in which the rotor core 20 is accommodated. The auxiliary magnets 5a and 5b are cured products of the magnet material filled in the arrangement holes 30 of the rotor core 20. The arrangement holes 30 are filled with the auxiliary magnets 5a and 5b.

[0052] The cross-sectional shape of the auxiliary magnet 5a is the same over the entire length of the auxiliary magnet 5a in the direction of its rotation axis. The cross-sectional shape of the auxiliary magnet 5a is a shape extending in a direction intersecting the radial direction. Specifically, the cross-sectional shape of the auxiliary magnet 5a is a rectangular shape having a longitudinal direction orthogonal to the radial direction. The entire auxiliary magnet 5a is disposed radially inward of the second magnet 42. The auxiliary magnet 5a is magnetized in a direction intersecting the circumferential direction, that is, in a direction intersecting the longitudinal direction of the auxiliary magnet 5a. Specifically, the auxiliary magnet 5a is magnetized in the radial direction as indicated by the dashed arrow in FIG. 4.

[0053] The cross-sectional shape of the auxiliary magnet 5b is the same over the entire length of the auxiliary magnet 5b in the direction of its rotation axis. The cross-sectional shape of the auxiliary magnet 5b is a shape extending in a direction intersecting the circumferential direction. Specifically, the cross-sectional shape of the auxiliary magnet 5b is a rectangular shape having a longitudinal direction coinciding with the radial direction. A part of the auxiliary magnet 5b is located radially inward of the second magnet 42. Note that the auxiliary magnet 5b may not have a portion located radially inward of the second magnet 42. That is, the entire auxiliary magnet 5b may be disposed between the second magnets 42 of the mutually adjacent magnetic pole portions 4 in the circumferential direction. The auxiliary magnet 5b is magnetized in a direction intersecting the radial direction, that is, in a direction intersecting the longitudinal direction of the auxiliary magnet 5b. Specifically, the auxiliary magnet 5b is magnetized in the circumferential direction as indicated by the dashed arrow in FIG. 4.

[0054] The magnetic fluxes of the auxiliary magnets 5a and 5b pass through a portion of the rotor core 20 located on the first magnet 41 side with respect to the second placement hole 22, the partition wall 29, and a portion of the rotor core 20 located on the side opposite to the first magnet 41 with respect to the second placement hole 22. That is, the auxiliary magnets 5a and 5b are magnetized so as to increase the amount of magnetic flux passing through the partition wall 29.

[0055] When current is supplied to the winding 62 of the stator 6 to form a rotating magnetic field, a magnetic torque is generated by the plurality of magnetic pole portions 4 and the plurality of auxiliary magnets 5a and 5b, and a reluctance torque is generated by the rotor body 2. The rotor 1 rotates about the rotation axis X by the magnetic torque and the reluctance torque. In this case, each magnetic pole portion 4 includes a plurality of magnets arranged in the radial direction, and the magnetic flux of the stator 6 passes between the plurality of magnets. Therefore, a reluctance torque is more easily obtained as compared with the case where the magnetic pole portion 4 is formed of one magnet.

[0056] In the rotor 1 having the above configuration, a dividing wall 29 that divides the second arrangement hole 22 is formed in the rotor body 2. The magnetic permeability of the dividing wall 29 is higher than the magnetic permeability of the second magnet 42. Therefore, the magnetic flux of the stator 6 easily passes through the dividing wall 29 and hardly passes through the second magnet 42. Accordingly, it is possible to prevent the demagnetization of the second magnet 42 due to the counter magnetic field of the magnetic flux of the stator 6.

[0057] Assume a case where the dividing wall 29 is not formed in the rotor body 2 and the second magnet 42 is a single magnet that is not divided. In this case, since the magnetic flux passing through the first magnet 41 among the magnetic fluxes of the stator 6 also passes through the second magnet 42, the magnetic resistance to this magnetic flux increases. Therefore, the magnetic flux of the stator 6 hardly passes through the first magnet 41, and the demagnetization of the first magnet 41 due to the magnetic flux of the stator 6 hardly occurs. On the other hand, the magnetic flux of the stator 6 also passes through the portion between the first magnet 41 and the second magnet 42 in the rotor body 2. The magnetic flux of the stator 6 passing through this portion passes only through the second magnet 42 without passing through the first magnet 41. Therefore, the magnetic resistance to the magnetic flux of the stator 6 passing through the second magnet 42 is small. That is, when the dividing wall 29 is not formed, the magnetic flux of the stator 6 more easily passes through the second magnet 42 than the first magnet 41, and the second magnet 42 is more likely to be demagnetized due to the counter magnetic field of the magnetic flux of the stator 6 as compared with the first magnet 41. Therefore, the fact that the dividing wall 29 can reduce the demagnetization of the second magnet 42 is particularly effective in reducing the demagnetization of the magnetic pole portion 4 having the first magnet 41 and the second magnet 42.

[0058] As described above, the dividing wall 29 prevents the reverse magnetic field demagnetization of the second magnet 42. However, if the dividing wall 29 is provided inside the first magnet 41 in the radial direction, the magnetic flux of the stator 6 passing through the dividing wall 29 will easily pass through the first magnet 41. In particular, since the magnetic flux of the stator 6 concentrates at the reference point P that intersects the d-axis of the magnetic pole portion 4 on the outer peripheral surface 28 of the rotor core 20, the magnetic flux of the stator 6 passing through the dividing wall 29 easily passes through the portion between the reference point P and the dividing wall 29 in the first magnet 41. However, in the rotor 1 of the present disclosure, the dimension of the magnetization direction of the portion between the reference point P and the dividing wall 29 in the first magnet 41 is larger than the dimension of the magnetization direction of the other portions of the first magnet 41. Therefore, the permeability coefficient of the portion between the reference point P and the dividing wall 29 in the first magnet 41 can be increased. Thus, it is possible to prevent the reverse magnetic field demagnetization of the first magnet 41 caused by the magnetic flux passing through the dividing wall 29.

[0059] Furthermore, the first placement hole 21 in which the first magnet 41 is placed is one undivided hole. Therefore, the amount of the first magnet 41 can be increased, the magnet torque can be improved, and thus the torque of the motor 100 can be improved. That is, by providing the dividing wall 29 only in the second placement hole 22 out of the first placement hole 21 and the second placement hole 22, and providing the thick portion 45 in the first magnet 41, the torque of the motor 100 can be ensured and the reverse magnetic field demagnetization of the magnetic pole portion 4 can be made difficult to occur.

[0060] Specifically, a protrusion 46 is formed in the portion of the first magnet 41 located between the reference point P and the dividing wall 29, and the thick portion 45 is the portion of the first magnet 41 where the protrusion 46 is formed. Therefore, it is possible to make only the portion where the magnetic flux of the stator 6 passing through the dividing wall 29 particularly easily passes through into the portion with a large dimension in the magnetization direction. Thus, it is possible to prevent the reverse magnetic field demagnetization of the first magnet 41 while reducing the increase in the amount of the first magnet 41.

[0061] Further, the partition wall 29 connects a portion of the rotor body 2 located on the first magnet 41 side of the second placement hole 22 and a portion of the rotor body 2 located on the side opposite to the first magnet 41 of the second placement hole 22. Therefore, the strength of the rotor core 20 can be improved against the centrifugal force acting on the magnetic pole portion 4 during the rotation of the rotor 1. In particular, when the mass of the second magnet 42 is larger than the mass of the first magnet 41, a large centrifugal force acts on the second magnet 42, but the partition wall 29 can appropriately improve the strength of the rotor core 20 against the centrifugal force acting on the second magnet 42.

[0062] Furthermore, since the second placement hole 22 in which the second magnet 42 is arranged is divided by the partition wall 29, the volume of the second magnet 42 arranged in the second placement hole 22 can be reduced, and the mass of the second magnet 42 can be reduced. Therefore, the centrifugal force acting on the second magnet 42 can be reduced.

[0063] Also, the average value of the dimensions in the magnetization direction of the second magnet 42 (that is, the dimension t2) is larger than the average value of the dimensions in the magnetization direction of the first magnet 41. Therefore, the permeability coefficient of the second magnet 42 can be increased to make it difficult for irreversible demagnetization of the second magnet 42 to occur. That is, the magnetic permeability of the magnet is substantially the same as the magnetic permeability of air. When the first magnet 41 is located in the magnetic circuit formed by the second magnet 42, the first magnet 41 is regarded as an air gap, and the permeability coefficient of the second magnet 42 tends to be small. However, by increasing the dimension of the second magnet 42 in the magnetization direction, the permeability coefficient of the second magnet 42 can be increased to make it difficult for irreversible demagnetization of the second magnet 42 to occur. In addition, since the average value of the dimensions in the magnetization direction of the first magnet 41 is smaller than the average value of the dimensions in the magnetization direction of the second magnet 42, the volume of the rotor body 2 can be increased, and the reluctance torque generated by the rotor body 2 can be improved.

[0064] In addition, the magnetic fluxes of the auxiliary magnets 5a and 5b passing through the partition wall 29 contribute to the generation of magnetic torque. Therefore, compared with a rotor without the auxiliary magnets 5a and 5b, magnetic torque can be more easily obtained. Thus, the torque of the motor 100 can be further improved. Furthermore, the auxiliary magnet 5b is disposed between the second magnets 42 of the magnetic pole portions 4 adjacent to each other in the circumferential direction. Therefore, the auxiliary magnet 5b can be provided by utilizing the space between the second magnets 42 adjacent to each other in the circumferential direction in the rotor body 2, and the increase in the size of the rotor 1 due to the provision of the auxiliary magnet 5b can be reduced.

[0065] Also, among the magnetic fluxes of the stator 6 that contribute to the reluctance torque, as shown by the arrow of the two-dot chain line in FIG. 4, it flows between the first magnet 41 and the second magnet 42, and also flows along the edge of the second magnet 42 on the side opposite to the first magnet 41. If the auxiliary magnets 5a and 5b with a large magnetic resistance are disposed at the positions through which the q-axis magnetic flux passes, the q-axis inductance decreases and the reluctance torque decreases. However, in this example, the auxiliary magnet 5a is disposed radially inward of the second magnet 42, and it is difficult for the q-axis magnetic flux to pass through. Also, a part of the auxiliary magnet 5b is disposed radially inward of the second magnet 42, and the portion through which the q-axis magnetic flux passes is small. Therefore, it is difficult for the q-axis inductance to decrease, and the reluctance torque can be improved.

[0066] Also, in the rotor as disclosed in Patent Document 1, in the radial outer side of the end of the magnet in the orthogonal cross-section of the rotor core, the magnetic flux generated by the stator (i.e., the magnetic flux in the opposite direction to the magnetic flux generated by the magnet) passes through, and due to this magnetic flux, the end of the magnet may cause demagnetization by the reverse magnetic field. On the other hand, in the rotor 1 of this example, notches 24 and 25 are formed in portions 33 and 34 located on the radial outer side of the two ends 41a and 41b of the first magnet 41 and portions 35 and 36 located on the radial outer side of the two ends 42a and 42b of the second magnet 42 in the rotor body 2. Therefore, the distances L1 from the ends 41a and 41b of the first magnet 41 to the stator 6 and the distance L2 from the ends 42a and 42b of the second magnet 42 to the stator 6 can be increased. Accordingly, it is possible to make it difficult for each of the first magnet 41 and the second magnet 42 to be demagnetized by the reverse magnetic field of the stator 6.

[0067] Here, the notches 24 and 25 increase the magnetic resistance in the outer regions of each of the two ends 41a and 41b of the first magnet 41 and the two ends 41a and 41b of the second magnet 42. Therefore, it is difficult for the magnetic flux generated by the stator 6 to pass through the outer regions of the ends 41a, 41b, 42a, and 42b of each of the first magnet 41 and the second magnet 42. Accordingly, it is possible to make it difficult for each of the first magnet 41 and the second magnet 42 to be demagnetized by the reverse magnetic field. Also, if the rotor body 2 does not exist in the outer regions of the ends 41a, 41b, 42a, and 42b of each of the first magnet 41 and the second magnet 42, the air gap 10 formed between the rotor core 20 and the inner peripheral surface of the stator core 61 becomes large, and it becomes difficult for the magnetic flux generated by the stator 6 to flow to the rotor 1. However, in this example, the portions 33 and 34 of the rotor body 2 are located on the radial outer side of the two ends 41a and 41b of the first magnet 41, and the portions 35 and 36 of the rotor body 2 are located on the radial outer side of the two ends 42a and 42b of the second magnet 42. Therefore, the air gap 10 formed between the rotor core 20 and the inner peripheral surface of the stator core 61 can be reduced, the magnetic flux generated by the stator 6 can easily flow to the rotor 1, and the torque of the motor 100 can be efficiently generated.

[0068] In order to make it difficult for each of the first magnet 41 and the second magnet 42 to generate reverse magnetic field demagnetization, the first placement hole 21 and the second placement hole 22 are each formed larger than the first magnet 41 and the second magnet 42, and a part of the first placement hole 21 and the second placement hole 22 may be used as a gap adjacent to the end portions 41a, 41b of the first magnet 41 and a gap adjacent to the end portion of the second magnet 42. However, when the first magnet 41 and the second magnet 42 are bonded magnets formed by filling the first placement hole 21 and the second placement hole 22 with a magnet material, since the bonded magnets are formed in the entire first placement hole 21 and the second placement hole 22, it is difficult to form the gaps. Therefore, when the first magnet 41 and the second magnet 42 are bonded magnets, it is preferable to form notches 24, 25 in the rotor body 2.

[0069] Also, portions 31, 32 between the two end portions 41a, 41b of the first magnet 41 and the two end portions 42a, 42b of the second magnet 42 protrude radially outward more than the radially outer portions 33, 34 of the two end portions 41a, 41b of the first magnet 41 in the rotor body 2 and the radially outer portions 35, 36 of the two end portions 42a, 42b of the second magnet 42 in the rotor body 2. Therefore, the air gap 10 between the portions 31, 32 and the stator core 61 can be reduced, and the torque of the motor 100 can be generated more efficiently.

[0070] Also, each of the first magnet 41 and the second magnet 42 is a bonded magnet. The bonded magnet can be molded like resin and has a higher degree of freedom in shape compared to a sintered magnet. Therefore, it is easy to form each of the first magnet 41 and the second magnet 42 into a desired shape.

[0071] Subsequently, motors 100A to 100K of Modification Examples 1 to 11 will be described. The basic configuration of motors 100A to 100K is the same as that of the motor 100. Therefore, hereinafter, motors 100A to 100K will be described mainly focusing on the differences from the motor 100.

[0072] FIG. 5 is a cross-sectional view of a motor 100A including a rotor 1A according to Modification 1. In this example, the protrusion 46 of the rotor 1A protrudes toward the partition wall 29.

[0073] FIG. 6 is a cross-sectional view of a motor 100B including a rotor 1B according to Modification 2. In this example, the protrusion 46 includes an outward protrusion 46a protruding toward the reference point P and an inward protrusion 46b protruding toward the partition wall 29.

[0074] FIG. 7 is a cross-sectional view of a motor 100C including a rotor 1C according to Modification 3. In this example, the partition wall 29 has a first partition wall 29a and a second partition wall 29b spaced apart in the direction in which the second reference line R2 extends.

[0075] The first partition wall 29a and the second partition wall 29b are arranged to be spaced apart with the d-axis interposed therebetween in the direction in which the second reference line R2 extends. Each of the first partition wall 29a and the second partition wall 29b extends in a direction intersecting the second reference line R2. Specifically, each of the first partition wall 29a and the second partition wall 29b extends in a direction orthogonal to the second reference line R2. Each of the first partition wall 29a and the second partition wall 29b connects a portion of the rotor core 20 located on the first magnet 41 side of the second placement hole 22 and a portion of the rotor core 20 located on the side opposite to the first magnet 41 of the second placement hole 22.

[0076] The second placement hole 22 is divided by the first partition wall 29a and the second partition wall 29b into three divided holes arranged in the direction in which the second reference line R2 extends. That is, the second magnet 42 is divided by the first partition wall 29a and the second partition wall 29b into three magnet pieces arranged in the direction in which the second reference line R2 extends.

[0077] The dimension of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the first partition wall 29a and the dimension of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the second partition wall 29b are each larger than the dimension of the magnetization direction of the other portions of the first magnet 41.

[0078] Specifically, the first magnet 41 has three thin portions 44 and two thick portions 45. The three thin portions 44 are spaced apart from each other in the direction in which the first reference line R1 extends. The thick portions 45 are disposed between the thin portions 44 adjacent to each other in the direction in which the first reference line R1 extends. One of the two thick portions 45 is located on a virtual straight line S1 connecting the reference point P and the first partition wall 29a, and the other is located on a virtual straight line S2 connecting the reference point P and the second partition wall 29b.

[0079] Specifically, the protrusion 46 includes a first protrusion 46c and a second protrusion 46d that are spaced apart from each other in the direction in which the second reference line R2 extends. The first protrusion 46c is formed at a portion of the first magnet 41 that intersects the virtual straight line S1. The first protrusion 46c protrudes toward the reference point P. The second protrusion 46d is formed at a portion of the first magnet 41 that intersects the virtual straight line S2. The second protrusion 46d protrudes toward the reference point P. The portions of the first magnet 41 where the first protrusion 46c and the second protrusion 46d are respectively formed are the thick portions 45.

[0080] In this example, two partition walls, i.e., the first partition wall 29a and the second partition wall 29b, are formed, and the magnetic flux of the stator 6 passing through the reference point P passes through each of the first partition wall 29a and the second partition wall 29b. Therefore, also in this example, it is difficult for the magnetic flux of the stator 6 to pass through the second magnet 42, and it is difficult for the counter magnetic field demagnetization of the second magnet 42 to occur. Further, the portion of the first magnet 41 between the reference point P and the first partition wall 29a has a magnetization direction dimension larger than the magnetization direction dimensions of the other portions, and has a high permeability coefficient. Therefore, it is possible to prevent the counter magnetic field demagnetization of the first magnet 41 from occurring due to the magnetic flux of the stator 6 passing through the first partition wall 29a. Similarly, the portion of the first magnet 41 between the reference point P and the second partition wall 29b has a magnetization direction dimension larger than the magnetization direction dimensions of the other portions, and has a high permeability coefficient. Therefore, it is possible to prevent the counter magnetic field demagnetization of the first magnet 41 from occurring due to the magnetic flux of the stator 6 passing through the second partition wall 29b.

[0081] FIG. 8 is an enlarged cross-sectional view of a motor 100D including a rotor 1D according to Modification 4. The basic configuration of the rotor 1D in this example is the same as that of the rotor 1C in Modification 3. However, in this example, the first protrusion 46c protrudes toward the first partition wall 29a, and the second protrusion 46d protrudes toward the second partition wall 29b.

[0082] FIG. 9 is an enlarged cross-sectional view of a motor 100E including a rotor 1E according to Modification 5. The basic configuration of the rotor 1E in this example is the same as that of the rotor 1C in Modification 3. However, in this example, the first protrusion 46c includes an outward protrusion 46c1 protruding toward the reference point P and an inward protrusion 46c2 protruding toward the first partition wall 29a. Further, the second protrusion 46d includes an outward protrusion 46d1 protruding toward the reference point P and an inward protrusion 46d2 protruding toward the first partition wall 29a.

[0083] FIG. 10 is an enlarged cross-sectional view of a motor 100F including a rotor 1F according to Modification 6. In this example, no protrusion 46 is formed on the first magnet 41, and the dimension of the first magnet 41 in the magnetization direction becomes continuously smaller toward both ends of the first magnet 41 in the direction in which the first reference line R1 extends from the portion of the first magnet 41 that intersects the virtual straight line S. Here, "becomes continuously smaller" means that the dimension of the first magnet 41 in the magnetization direction gradually decreases at a constant rate or decreases gradually without steps. In this example, although the boundary between the thick portion 45 and the thin portion 44 does not clearly appear on the appearance, the central portion including the portion of the first magnet 41 that intersects the virtual straight line S becomes the thick portion 45, and each of the both side portions of the first magnet 41 sandwiching the thick portion 45 becomes the thin portion 44.

[0084] FIG. 11 is an enlarged cross-sectional view of a motor 100G including a rotor 1G according to Modification 7. In this example, the rotor 1G does not include the auxiliary magnets 5a and 5b.

[0085] FIG. 12 is an enlarged cross-sectional view of a motor 100H including a rotor 1H according to Modification 8. In this example, the magnetic pole portion 4 includes a third magnet 43 in addition to the first magnet 41 and the second magnet 42.

[0086] The third magnet 43 is disposed radially inside the second magnet 42 in the rotor core 20. The third magnet 43 is formed in a layered manner. That is, the magnetic pole portion 4 has three magnet layers of the first magnet 41, the second magnet 42, and the third magnet 43.

[0087] The third magnet 43 is a bonded magnet. The magnet material of the third magnet 43 is the same as, for example, the magnet materials of the first magnet 41 and the second magnet 42, respectively. In the rotor core 20, a third placement hole 23 in which the third magnet 43 is disposed is formed. The third placement hole 23 is a hole that penetrates the rotor core 20 in the rotation axis direction. The cross-sectional shape of the third placement hole 23 is the same as the cross-sectional shape of the third magnet 43. The third magnet 43 is a cured product of a magnet material filled in the third placement hole 23 of the rotor core 20.

[0088] The third magnet 43 is formed in a plate shape extending along the rotation axis X. The cross-sectional shape of the third magnet 43 is the same over the entire length in the rotation axis direction of the first magnet 41. The cross-sectional shape of the third magnet 43 is linear. That is, the cross-sectional shape of the third magnet 43 has a shape extending along a predetermined third reference line R3.

[0089] The third magnet 43 has two end portions 43a, 43b in the direction in which the third reference line R3 extends, and an intermediate portion 43c located between the two end portions 43a, 43b. Note that the intermediate portion 43c does not refer to all of the remaining portions of the third magnet 43 excluding the two end portions 43a, 43b, but refers to at least a part of the remaining portions excluding the two end portions 43a, 43b. The intermediate portion 43c may or may not include the center in the direction in which the third reference line R3 extends in the third magnet 43. Also, in the third magnet 43, the direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the third reference line R3 is also referred to as the "thickness direction".

[0090] The third magnet 43 is curved or bent so as to be concave toward the inner side in the radial direction. The intermediate portion 43c is located closer to the inner side in the radial direction than the two end portions 43a and 43b are. That is, the third magnet 43 is curved or bent such that the two end portions 43a and 43b approach the outer peripheral surface 28 of the rotor core 20 more than the intermediate portion 43c does. Specifically, the third magnet 43 is formed in a substantially U shape. That is, the third magnet 43 is formed in an arc shape that is curved so as to be concave toward the inner side in the radial direction. The cross-sectional shape of the third magnet 43 is a line-symmetric shape centered on a symmetry axis extending in the radial direction.

[0091] The third magnet 43 is magnetized in a direction intersecting the third reference line R3. Specifically, the third magnet 43 is magnetized in a direction parallel to the plane orthogonal to the rotation axis X and orthogonal to the third reference line R3. That is, the magnetization direction of the third magnet 43 is the thickness direction of the third magnet 43.

[0092] The rotor core 20 further has a partition wall 37 that divides the third placement hole 23. The partition wall 37 is disposed at the center in the direction in which the third reference line R3 extends in the third placement hole 23. The partition wall 37 connects the portion of the rotor core 20 located on the second magnet 42 side of the third placement hole 23 and the portion of the rotor core 20 located on the side opposite to the second magnet 42 in the third placement hole 23.

[0093] The partition wall 37 is located on the d-axis of the magnetic pole portion 4. The partition wall 37 extends in a direction intersecting the third reference line R3 in the orthogonal cross-section, more specifically, in a direction orthogonal to the third reference line R3. The third placement hole 23 is divided by the partition wall 37 into two divided holes arranged in the direction in which the third reference line R3 extends. The third magnet 43 is divided by the partition wall 37 into two magnet pieces arranged in the direction in which the third reference line R3 extends. The thick portion 45 of the first magnet 41 is located between the partition wall 37 and the reference point P. That is, in the orthogonal cross-section, the thick portion 45, the partition wall 29, and the partition wall 37 are arranged on the same straight line.

[0094] The dimension of the magnetization direction of the third magnet 43 is constant in the direction in which the third reference line R3 extends. The average value of the dimension of the magnetization direction of the third magnet 43 is larger than the average value of the dimension of the magnetization direction of the second magnet 42. Note that the average value of the dimension of the magnetization direction of the third magnet 43 may be the same as the average value of the dimension of the magnetization direction of the second magnet 42, or may be smaller than the average value of the dimension of the magnetization direction of the second magnet 42.

[0095] In this example, a partition wall 37 that divides the third placement hole 23 is formed in the rotor body 2. Therefore, the magnetic flux of the stator 6 easily passes through the partition wall 37 and hardly passes through the third magnet 43. Therefore, it is possible to prevent the third magnet 43 from being demagnetized by the reverse magnetic field of the stator 6.

[0096] FIG. 13 is an enlarged cross-sectional view of a motor 100I including a rotor 1I of Modification 9. In this example, holes 26 and 27 are formed in the rotor body 2 instead of the notches 24 and 25. Similar to the notches 24 and 25, the holes 26 and 27 make it difficult for the stator 6 of each of the first magnet 41 and the second magnet 42 to cause demagnetization due to the reverse magnetic field.

[0097] FIG. 14 is an enlarged cross-sectional view of a motor 100J including a rotor 1J of Modification 10. In this example, the magnetic pole portion 4 has only the second magnet 42 among the first magnet 41 and the second magnet 42. That is, the magnetic pole portion 4 has only a single-layer magnet layer formed by the second magnet 42. Also in this example, the magnetic flux of the auxiliary magnets 5a and 5b passing through the partition wall 29 contributes to the generation of the magnet torque and can improve the torque of the motor 100.

[0098] FIG. 15 is an enlarged cross-sectional view of a motor 100K including a rotor 1K according to Modification 11. In this example, instead of the auxiliary magnets 5a and 5b, the rotor 1K includes a plurality of auxiliary magnets 5c and 5d. The auxiliary magnets 5c and 5d are provided one by one in each magnetic pole portion 4. That is, the rotor 1K includes six auxiliary magnets 5c and six auxiliary magnets 5d. The auxiliary magnets 5c and 5d are disposed between the second magnet 42 and the rotation axis X. Specifically, the auxiliary magnet 5c is disposed between the magnet piece 48 and the rotation axis X. The auxiliary magnet 5d is disposed between the magnet piece 49 and the rotation axis X. The auxiliary magnets 5c and 5d are arranged side by side in the circumferential direction. The auxiliary magnets 5c and 5d are spaced apart from each other across the extension line Sa of the virtual straight line S in the circumferential direction.

[0099] The auxiliary magnets 5c and 5d are bonded magnets. The auxiliary magnets 5c and 5d are formed of, for example, the same material as the first magnet 41 and the second magnet 42. The auxiliary magnets 5c and 5d are formed, for example, in the same manner as the auxiliary magnets 5a and 5b by injecting a magnet material that becomes a bonded magnet into a mold in which the rotor core 20 is accommodated.

[0100] The cross-sectional shape of the auxiliary magnets 5c and 5d is the same over the entire length of the auxiliary magnets 5c and 5d in the rotation axis direction. The cross-sectional shape of the auxiliary magnets 5c and 5d is a shape that extends away from the extension line Sa in the circumferential direction as it goes toward the outer side in the radial direction. That is, the interval between the auxiliary magnets 5c and 5d in the circumferential direction becomes wider as it goes toward the outer side in the radial direction. Specifically, the cross-sectional shape of the auxiliary magnets 5c and 5d is a rectangular shape having a longitudinal direction that intersects the radial direction and the circumferential direction. A part of the auxiliary magnets 5c and 5d is disposed between the second magnets 42 of the adjacent magnetic pole portions 4 in the circumferential direction. Also, a part of the auxiliary magnets 5c and 5d is disposed inside the corresponding magnetic pole portion 4 in the radial direction. The auxiliary magnets 5c and 5d are magnetized in a direction orthogonal to the longitudinal direction of the auxiliary magnets 5c and 5d as indicated by the dashed arrow in FIG. 15.

[0101] The magnetic fluxes of the auxiliary magnets 5c and 5d pass through a portion of the rotor core 20 located on the first magnet 41 side with respect to the second placement hole 22, the partition wall 29, and a portion of the rotor core 20 located on the side opposite to the first magnet 41 with respect to the second placement hole 22. That is, the auxiliary magnets 5c and 5d are also magnetized so as to increase the amount of magnetic flux passing through the partition wall 29. Also in this example, the magnetic fluxes of the auxiliary magnets 5c and 5d passing through the partition wall 29 contribute to the generation of magnetic torque and can improve the torque of the motor 100.

[0102] 《Other Embodiments》 As described above, embodiments and modifications have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited thereto, and is also applicable to embodiments in which changes, replacements, additions, omissions, etc. are made as appropriate. Further, it is also possible to combine the respective components described in the embodiments and modifications to form a new embodiment. Also, among the components described in the accompanying drawings and the detailed description, there may be included not only the components essential for solving the problems but also the components not essential for solving the problems for the purpose of exemplifying the technology. Therefore, it should not be immediately determined that those non-essential components are essential just because they are described in the accompanying drawings and the detailed description.

[0103] The rotor body 2 may be formed only of the rotor core 20 without including the shaft 11. The rotor body 2 may be formed only of the shaft 11 without including the rotor core 20. The shaft 11 does not have to be a soft magnetic material. The shaft 11 may be integrally formed with the rotor core 20.

[0104] The rotor core 20 may have four or more partition walls 29. That is, the second magnet 42 may be divided at three or more positions in the direction in which the second reference line R2 extends, and the second magnet 42 may have four or more magnet pieces. In this case, the magnetization direction dimension of the portion between the reference point P and each partition wall of the first magnet 41 may be larger than the magnetization direction dimension of the other portions of the first magnet 41.

[0105] The number of magnetic pole portions 4 of the rotor 1 is not limited. The number of magnet layers of the magnetic pole portion 4 is not limited. The magnetic pole portion 4 may include four or more magnet layers. The d-axis of the magnetic pole portion 4 does not have to coincide with the central axis of the shape of the magnetic pole portion 4. The q-axis of the magnetic pole portion 4 does not have to pass through the center between the circumferentially adjacent magnetic pole portions 4 in the orthogonal cross-section.

[0106] Each of the first magnet 41 and the second magnet 42 may be an anisotropic bonded magnet or an isotropic bonded magnet. Each of the first magnet 41 and the second magnet 42 may be a sintered magnet formed by sintering magnetic powder.

[0107] The cross-sectional shape of each of the first magnet 41 and the second magnet 42 is not limited. The cross-sectional shape of each of the first magnet 41 and the second magnet 42 may be, for example, substantially V-shaped or substantially W-shaped. The symmetry axis of the first magnet 41 does not have to coincide with the d-axis of the magnetic pole portion 4. The symmetry axis of the second magnet 42 does not have to coincide with the d-axis of the magnetic pole portion 4.

[0108] The number of the thin portions 44 of the first magnet 41 is not limited. The dimension in the magnetization direction of the thin portion 44 does not have to be constant. The number of the thick portions 45 of the first magnet 41 is not limited. The dimension in the magnetization direction of the thick portion 45 may be constant over the direction in which the first reference line R1 extends.

[0109] The dimension t2 in the magnetization direction of the second magnet 42 does not have to be constant. The dimension t2 in the magnetization direction of the second magnet 42 may be larger than the maximum value of the dimension in the magnetization direction of the first magnet 41. The average value of the dimension in the magnetization direction of the second magnet 42 may be smaller than the average value of the dimension in the magnetization direction of the first magnet 41 or may be the same as the average value of the dimension in the magnetization direction of the first magnet 41. The dimension in the magnetization direction of the second magnet 42 may change in the direction in which the second reference line R2 extends.

[0110] The auxiliary magnets 5a to 5d may be anisotropic bonded magnets or isotropic bonded magnets. The auxiliary magnets 5a to 5d may be sintered magnets formed by sintering magnetic powder. The shape, position, size, etc. of the auxiliary magnets 5a to 5d are not limited. The magnetization direction of the auxiliary magnets 5a to 5d is not limited as long as the amount of magnetic flux passing through the dividing wall 29 by the auxiliary magnets 5a to 5d is increased. The rotors 1A to 1F, 1H to 1K of Modifications 1 to 6, 8 to 12 may not include the auxiliary magnets 5a to 5d.

[0111] The notches 24 and 25 or the holes 26 and 27 may be formed in at least one of the portions 33 and 34 located outside the end portions 41a and 41b of the first magnet 41 and the portions 35 and 36 located outside the end portions 42a and 42b of the second magnet 42 in the rotor core 20. Further, the cross-sectional shape of each of the notches 24 and 25 and the holes 26 and 27 is not limited, and may be, for example, a triangular shape or a semi-circular shape. The notches 24 and 25 and the holes 26 and 27 can be omitted.

[0112] The rotors 1, 1A to 1I, 1K according to the first aspect of the technology of the present disclosure include a rotor body 2 that rotates around the rotation axis X, and a plurality of magnetic pole portions 4 that are arranged in the circumferential direction around the rotation axis X in the rotor body 2 and form different magnetic poles alternately in the circumferential direction. The magnetic pole portions 4 include a first magnet 41 and a second magnet 42 arranged inside the first magnet 41 in the radial direction centered on the rotation axis X. In the rotor body 2, a first arrangement hole 21 in which the first magnet 41 is arranged and a second arrangement hole 22 in which the second magnet 42 is arranged are formed. The rotor body 2 has a dividing wall 29 that connects a portion of the second arrangement hole 22 located on the first magnet 41 side and a portion of the second arrangement hole 22 located on the side opposite to the first magnet 41 to divide the second arrangement hole 22. The first arrangement hole 21 is one undivided hole. When the intersection point of the outer peripheral surface of the rotor body 2 with the d-axis of the magnetic pole portion 4 is used as a reference point P, the dimension t1a of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the dividing wall 29 is larger than the dimension t1b of the magnetization direction of the other portion of the first magnet 41.

[0113] According to this configuration, the magnetic flux of the stator 6 easily passes through the dividing wall 29 and hardly passes through the second magnet 42 disposed in the second arrangement hole 22. Therefore, it is possible to hardly cause demagnetization of the second magnet 42 due to the counter magnetic field. Further, since the dimension t1a of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the dividing wall 29 is larger than the dimension t1b of the magnetization direction of the other portion of the first magnet 41, the permeability coefficient of this portion can be increased. Therefore, it is possible to prevent demagnetization of the first magnet 41 due to the magnetic flux of the stator 6. Furthermore, since the first arrangement hole 21 is a single undivided hole, the volume of the first magnet 41 disposed in the first arrangement hole 21 can be increased, the magnet torque can be improved, and thus the torque of the motor 100 can be improved.

[0114] Also, in the rotors 1, 1A to 1E, 1G to 1I, 1K according to the second aspect of the technology of the present disclosure, in the rotors 1, 1A to 1E, 1G to 1I, 1K according to the first aspect, a protrusion 46 protruding toward the reference point P or the dividing wall 29 is formed in the portion of the first magnet 41 located between the reference point P and the dividing wall 29.

[0115] According to this configuration, it is possible to make only the portion through which the magnetic flux passing through the dividing wall 29 of the first magnet 41 particularly easily passes, a portion having a large dimension in the magnetization direction. Therefore, it is possible to prevent demagnetization of the first magnet 41 due to the counter magnetic field while reducing an increase in the amount of the first magnet 41.

[0116] Further, in the rotors 1C to 1E according to the third aspect of the technology of the present disclosure, in the rotors 1C to 1E according to the first or second aspect, the first magnet 41 has a shape extending along a predetermined first reference line R1 in a cross section orthogonal to the rotation axis X, the second magnet 42 has a shape extending along a predetermined second reference line R2 in a cross section orthogonal to the rotation axis X, the partition wall 29 includes a first partition wall 29a and a second partition wall 29b spaced apart in the extending direction of the second reference line R2, and each of the first partition wall 29a and the second partition wall 29b connects a portion located on the first magnet 41 side of the second placement hole 22 and a portion located on the side opposite to the first magnet 41 of the second placement hole 22. Each of the dimension of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the first partition wall 29a and the dimension of the magnetization direction of the portion of the first magnet 41 located between the reference point P and the second partition wall 29b is larger than the dimension of the magnetization direction of the other portion of the first magnet 41.

[0117] According to this configuration, since two partition walls, i.e., the first partition wall 29a and the second partition wall 29b, are formed, the magnetic flux of the stator 6 becomes more difficult to pass through the second magnet 42, and it is possible to further make it difficult to generate demagnetization of the counter magnetic field of the second magnet 42. Further, by increasing the dimension of the magnetization direction of the portion of the first magnet 41 between the reference point P and the first partition wall 29a, the permeability coefficient of this portion can be increased and demagnetization of the counter magnetic field can be made difficult to occur. Similarly, by increasing the dimension of the magnetization direction of the portion of the first magnet 41 between the reference point P and the second partition wall 29b, the permeability coefficient of this portion can be increased and demagnetization of the counter magnetic field can be made difficult to occur. Therefore, it is possible to make it difficult for the first magnet 41 to be demagnetized by the counter magnetic field.

[0118] Further, in the rotors 1, 1A to 1I, 1K according to the fourth aspect of the technology of the present disclosure, in the rotors 1, 1A to 1I, 1K according to any one of the first to third aspects, the average value of the dimension of the magnetization direction of the second magnet 42 is larger than the average value of the dimension of the magnetization direction of the first magnet 41.

[0119] According to this configuration, since the thick portion 45, which is the portion of the first magnet 41 where the magnetization dimension has increased, has a large magnetic resistance, the permeability coefficient of the portion of the second magnet 42 through which the magnetic flux passing through the thick portion 45 passes is likely to be small. However, by increasing the average value of the dimension in the magnetization direction of the second magnet 42, the permeability coefficient of the second magnet 42 can be increased, making it difficult for irreversible demagnetization of the second magnet 42 to occur. In addition, since the average value of the dimension in the magnetization direction of the first magnet 41 is smaller than the average value of the dimension in the magnetization direction of the second magnet 42, the volume of the rotor body 2 can be increased, and the reluctance torque generated by the rotor body 2 can be improved.

[0120] Further, the rotors 1, 1A to 1F, 1H, 1I, 1K according to the fifth aspect of the technology of the present disclosure are provided with auxiliary magnets 5a to 5d that are provided between the magnetic pole portions 4 adjacent to each other in the radial direction or in the circumferential direction inside the second magnet 42 in the rotor body 2 in the rotors 1, 1A to 1F, 1H, 1I, 1K according to any one of the first to fourth aspects, and increase the amount of magnetic flux passing through the partition wall 29.

[0121] In other words, the rotors 1, 1A to 1F, 1H to 1K include a rotor body 2 that rotates around the rotation axis X, and a plurality of second magnets 42 (magnets) that are arranged in the circumferential direction around the rotation axis X in the rotor body 2 and form different magnetic poles alternately in the circumferential direction. In the rotor body 2, a second arrangement hole 22 (arrangement hole) in which the second magnet 42 is arranged is formed. The rotor body 2 has a partition wall 29 that connects a portion located outside the second arrangement hole 22 in the radial direction and a portion located inside the second arrangement hole 22 in the radial direction to divide the second arrangement hole 22. Auxiliary magnets 5a to 5d that increase the amount of magnetic flux passing through the partition wall 29 are provided between the second magnets 42 adjacent to each other in the radial direction or in the circumferential direction inside the second magnet 42 in the rotor body 2.

[0122] According to this configuration, the magnet torque can be improved by the auxiliary magnets 5a to 5d, and thus the torque of the motor 100 can be improved. Further, the auxiliary magnet 5b can be provided by using the space between the magnetic pole portions 4 adjacent to each other in the circumferential direction in the rotor main body 2, and the increase in the size of the rotor 1 can be reduced.

[0123] Also, the motors 100, 100A to 100I, 100K according to the sixth aspect of the technology of the present disclosure include the rotors 1, 1A to 1I, 1K of any one of the first to fifth aspects, and the stator 6 that drives the rotors 1A to 1I, 1K.

Explanation of reference numerals

[0124] 100, 100A to 100K Motors 1, 1A to 1K Rotors 2 Rotor main body 21 First arrangement hole 22 Second arrangement hole 29 Partition wall 29a First partition wall 29b Second partition wall 4 Magnetic pole portions 41 First magnet 42 Second magnet 5a to 5d Auxiliary magnets 6 Stator t1a Dimension t1b Dimension t2 Dimension P Reference point R1 First reference line R2 Second reference line X Rotation axis

Claims

1. A rotor body that rotates around a rotation axis, and a plurality of magnetic pole portions arranged in a circumferential direction centered on the rotation axis in the rotor body, and forming alternately different magnetic poles in the circumferential direction. The magnetic pole portion includes a first magnet and a second magnet arranged inside the first magnet in a radial direction centered on the rotation axis. In the rotor body, a first arrangement hole in which the first magnet is arranged and a second arrangement hole in which the second magnet is arranged are formed. The rotor body has a partition wall that connects a portion of the second arrangement hole located on the first magnet side and a portion of the second arrangement hole located on the side opposite to the first magnet to divide the second arrangement hole. The first arrangement hole is one undivided hole. When the intersection point with the d-axis of the magnetic pole portion on the outer peripheral surface of the rotor body is used as a reference point, the dimension of the magnetization direction of the portion of the first magnet located between the reference point and the partition wall is larger than the dimension of the magnetization direction of other portions of the first magnet. A rotor in which the dimension of the magnetization direction of other portions of the first magnet is smaller than the dimension of the magnetization direction of the second magnet, and the dimension of the magnetization direction of the portion of the first magnet located between the reference point and the partition wall is larger than the dimension of the magnetization direction of the second magnet.

2. In the rotor according to Claim 1, a protrusion protruding toward the reference point or the partition wall is formed in the portion of the first magnet located between the reference point and the partition wall.

3. In the rotor according to Claim 1 or Claim 2, The first magnet has a shape extending along a predetermined first reference line in a cross section perpendicular to the rotation axis. The second magnet has a shape extending along a predetermined second reference line in a cross section perpendicular to the rotation axis. The partition wall includes a first partition wall and a second partition wall spaced apart in the extending direction of the second reference line. Each of the first partition wall and the second partition wall connects a portion of the second arrangement hole located on the first magnet side and a portion of the second arrangement hole located on the side opposite to the first magnet. A rotor in which the dimension of the magnetization direction of the portion of the first magnet located between the reference point and the first partition wall and the dimension of the magnetization direction of the portion of the first magnet located between the reference point and the second partition wall are each larger than the dimension of the magnetization direction of other portions of the first magnet.

4. In the rotor according to Claim 1 or Claim 2, A rotor in which an average value of dimensions in a magnetization direction of the second magnet is larger than an average value of dimensions in a magnetization direction of the first magnet.

5. In the rotor according to claim 1 or claim 2, A rotor further comprising an auxiliary magnet provided inside the second magnet in the radial direction or between the second magnets of the magnetic pole portions adjacent to each other in the circumferential direction in the rotor body, and increasing an amount of magnetic flux passing through the partition wall.

6. A motor comprising the rotor according to claim 1 or claim 2, and a stator for driving the rotor.

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