Rotor and motor

Abstract

The present invention reduces the occurrence of the leakage flux of a permanent magnet and thereby mitigates the reduction of magnetic torque. A rotor 1 comprises: a rotor body 2 that rotates about a rotational axis A; and a plurality of permanent magnets 4 that are arranged in the rotor body 2 in the circumferential direction about the rotational axis A and form magnetic poles alternately different from each other in the circumferential direction. The cross-sectional shape of the permanent magnets 4, which is orthogonal to the rotational axis A, has a shape extending along a predetermined reference line. The permanent magnets 4 are magnetized in a direction intersecting with the reference line in the cross-section orthogonal to the rotational axis A. At least one end portion of each of the permanent magnets 4 in the reference line direction is exposed from the outer circumferential surface 28 of the rotor body 2.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a motor. This motor includes a rotor and a stator. The rotor is of an embedded magnet type and includes a rotor core and a plurality of permanent magnets provided on 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 leakage flux (flux short circuit) in which the magnetic flux generated by the permanent magnet returns to the permanent magnet without linking to the stator coil, and thus, there is a risk that the magnet torque generated by the permanent magnet becomes small.

[0005] The technology disclosed herein is made in view of such a point, and the object thereof is to reduce the generation of leakage flux of the permanent magnet and reduce the decrease in magnet torque.

[0006] The technology disclosed herein includes a rotor body that rotates around a rotation axis, and a plurality of permanent magnets 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 cross-sectional shape of the permanent magnet orthogonal to the rotation axis has a shape extending along a predetermined reference line. The permanent magnet is magnetized in a direction intersecting the reference line in a cross-section orthogonal to the rotation axis, and at least one end of the permanent magnet in the direction of the reference line is exposed from the outer peripheral surface of the rotor body.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. FIG. 1 shows a motor 100 according to an embodiment.

[0009] The motor 100 includes a rotor 1 that rotates around a predetermined rotation axis A, and a stator 6 that rotates the rotor 1 around the rotation axis A. A permanent magnet 4 is 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.

[0010] Hereinafter, the direction in which the rotation axis A extends is referred to as the "rotation axis direction". The circumferential direction centered on the rotation axis A is referred to as the "circumferential direction". The radial direction centered on the rotation axis A is referred to as the "radial direction". The side facing the rotation axis A in the radial direction is referred to as the "radial inner side", and the side opposite to the rotation axis A is referred to as the "radial outer side".

[0011] 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.

[0012] 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 of the stator core 61. The winding 62 is wound around the plurality of teeth 61a. When a current is supplied to the winding 62, the stator 6 forms a rotating magnetic field that rotates the rotor 1.

[0013] The rotor 1 includes a rotor body 2 that rotates around the rotation axis A, and a plurality of permanent magnets 4 that are arranged in the circumferential direction on the rotor body 2 and form alternately different magnetic poles in the circumferential direction.

[0014] At least a part of the rotor body 2 is formed of a soft magnetic material. The rotor body 2 has magnetic salient poles and 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 5.

[0015] The rotor core 20 is a soft magnetic material. The rotor core 20 is formed of, for example, a plurality of electromagnetic steel sheets laminated on each other. The rotor core 20 is formed in an annular shape surrounding the rotation axis A. Specifically, the rotor core 20 is formed in a cylindrical shape concentric with the stator core 61. The outer peripheral surface of the rotor core 20 forms the outer peripheral surface 28 of the rotor body 2. The shape of the cross section of the rotor core 20 perpendicular to the rotation axis A 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 of the rotor core 20 and the inner peripheral surface of the stator core 61.

[0016] The shaft 5 is fitted inside the rotor core 20. The shaft 5 is fixed to the rotor core 20. The axis of the shaft 5 coincides with the rotation axis A. The shaft 5 is rotatably supported by the motor case 7 via a bearing or the like. The rotor core 20 rotates around the rotation axis A together with the shaft 5. The shaft 5 is a soft magnetic material.

[0017] A plurality of permanent magnets 4 are provided on the rotor core 20. The plurality of permanent magnets 4 generate a magnet torque in a rotating magnetic field formed by the stator 6. The rotor 1 includes six permanent magnets 4. The plurality of permanent magnets 4 are arranged at equal intervals in the circumferential direction.

[0018] The permanent magnet 4 is a bonded magnet. The bonded magnet is a permanent magnet 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 nitride-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.

[0019] The permanent magnet 4 is formed, for example, by insert molding. In this case, the permanent magnet 4 is formed by injecting a magnet material that becomes a bonded magnet into a mold 8 (see FIGS. 4 and 5) in which the rotor core 20 is accommodated. That is, the permanent magnet 4 is a cured product of a magnet material filled inside the rotor core 20.

[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. The permanent magnet 4 is formed in a plate shape extending along the rotation axis A. The permanent magnet 4 is formed over the entire length of the rotor core 20 in the rotation axis direction.

[0021] The cross-sectional shape orthogonal to the rotation axis A of the rotor 1 will be described below. Unless otherwise specified, the "cross-sectional shape" means the cross-sectional shape orthogonal to the rotation axis A. The shape of the cross-section of the permanent magnet 4 orthogonal to the rotation axis A is the same over the entire length in the rotation axis direction of the permanent magnet 4.

[0022] The cross-sectional shape of the permanent magnet 4 is linear. That is, the cross-sectional shape of the permanent magnet 4 has a shape extending along a predetermined reference line R. The permanent magnet 4 has two end portions 41, 42 and an intermediate portion 43 located between the two end portions 41, 42 in the direction in which the reference line R extends. Note that the intermediate portion 43 does not refer to all of the remaining portions of the permanent magnet 4 excluding the two end portions 41, 42, but refers to at least a part of the remaining portions excluding the two end portions 41, 42. The intermediate portion 43 may or may not include the center in the direction in which the reference line R extends of the permanent magnet 4.

[0023] The cross-sectional shape of the permanent magnet 4 is curved or bent so as to be concave toward the inner side in the radial direction. That is, the permanent magnet 4 is curved or bent such that the two end portions 41, 42 approach the outer peripheral surface 28 of the rotor main body 2 (that is, the outer peripheral surface of the rotor core 20) more than the intermediate portion 43. Specifically, the cross-sectional shape of the permanent magnet 4 is formed in a U shape concave toward the inner side in the radial direction. More specifically, the cross-sectional shape of the permanent magnet 4 is a line-symmetric shape centered on the symmetry axis extending in the radial direction.

[0024] The dimension of the permanent magnet 4 in the direction parallel to the plane orthogonal to the rotation axis A and orthogonal to the reference line R (hereinafter, this dimension is also referred to as the thickness) is substantially constant. At least one of the two end portions 41, 42 of the permanent magnet 4 is exposed from the outer peripheral surface 28 of the rotor main body 2. In this example, both of the two end portions 41, 42 of the permanent magnet 4 are exposed from the outer peripheral surface 28 of the rotor main body 2. The radially outer surfaces of the two end portions 41, 42 of the permanent magnet 4 are flush with the outer peripheral surface 28 of the rotor main body 2.

[0025] The permanent magnet 4 is magnetized in a direction intersecting the reference line R in a cross-section orthogonal to the rotation axis A. Specifically, the magnetization direction of the permanent magnet 4 is orthogonal to the reference line R. The symmetry axis, which is the center of the line-symmetric shape of the permanent magnet 4, is set to the d-axis of the rotor 1, for example.

[0026] The rotor body 2 includes a first portion 21 and a second portion 22 divided by a plurality of permanent magnets 4. The rotor body 2 includes the same number of second portions 22 as the permanent magnets 4.

[0027] The first portion 21 is a portion of the rotor body 2 that includes or encloses the rotation axis A. The first portion 21 also includes a shaft 5. The outer peripheral surface of the first portion 21 is formed by a plurality of curved surfaces 23 that coincide with the outer peripheral surface of a single virtual cylinder centered on the rotation axis A, and a plurality of recesses 24 that are recessed radially inward. The curved surfaces 23 and the recesses 24 are alternately arranged in the circumferential direction. That is, one curved surface 23 is arranged between every two adjacent recesses 24. In other words, one recess 24 is arranged between every two adjacent curved surfaces 23.

[0028] The plurality of curved surfaces 23 are arranged at equal intervals in the circumferential direction. The plurality of curved surfaces 23 are arranged on the outer peripheral surface of a single virtual cylinder centered on the rotation axis A. The number of curved surfaces 23 is the same as the number of permanent magnets 4. The plurality of recesses 24 are arranged at equal intervals in the circumferential direction. Each recess 24 extends in the rotation axis direction and opens radially outward. The number of recesses 24 is the same as the number of permanent magnets 4.

[0029] The permanent magnets 4 are accommodated in the recesses 24. The cross-sectional shape of the permanent magnet 4 is curved or bent so as to be recessed radially inward as described above. That is, the permanent magnet 4 has a shape that fits into the recess 24. The permanent magnet 4 is in close contact with the inner surface 24a of the recess 24.

[0030] The permanent magnet 4 extends in the direction of the rotation axis and has a recess 44 that opens radially outward. The second part 22 is accommodated in the recess 44. The second part 22 is located radially outside the intermediate part 43 of the permanent magnet 4. The second part 22 has a shape that fits into the recess 44. The second part 22 has an inner surface 22a located within the recess 44 and an outer surface 22b that is exposed radially outward from the recess 44. The inner surface 22a is in close contact with the permanent magnet 4. The outer surface 22b, together with the curved surface 23 of the first part 21, forms the outer peripheral surface of a single virtual cylinder centered on the rotation axis A. The outer peripheral surface 28 of the rotor body 2 is formed by the curved surface 23 and the outer surface 22b.

[0031] The permanent magnet 4 is interposed between the first part 21 and the second part 22. The second part 22 is separated from the first part 21 and is not connected to the first part 21. The inner surface 24a of the recess 24 of the first part 21 is adhered to the permanent magnet 4. The inner surface 22a of the second part 22 is adhered to the permanent magnet 4. By these means, the first part 21, the second part 22, and the permanent magnet 4 are integrally fixed.

[0032] The end portions 41, 42 of the permanent magnet 4 are exposed radially outward from between the first part 21 and the second part 22. Specifically, the end portion 41 has an end surface 41a located at one end in the direction of the reference line R. The end portion 42 has an end surface 42a located at the other end in the direction of the reference line R. The end surface 41a and the end surface 42a are smoothly connected to the curved surface 23 of the first part 21 and the outer surface 22b of the second part 22 to form a single curved surface. Specifically, the curved surface 23, the outer surface 22b, the end surface 41a, and the end surface 42a form the outer peripheral surface of a single virtual cylinder centered on the rotation axis A.

[0033] The cross-sectional shape of each of the two ends 41, 42 of the permanent magnet 4 is linear. In a cross-section perpendicular to the rotation axis A, the two ends 41, 42 are each inclined with respect to the radial direction. The circumferential width (i.e., the width in the circumferential direction from one end 41 to the other end 42) W1 of the two ends 41, 42 becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2 (i.e., as it moves away from the rotation axis A). Since the permanent magnet 4 is in close contact with the inner surface 24a of the recess 24, the circumferential interval of the recess 24 (i.e., the inner surface 24a) also becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2. Also, since the thickness of the ends 41, 42 is constant, the circumferential interval of the recess 44 of the permanent magnet 4, i.e., the interval between the inner sides of the two ends 41, 42 in the circumferential direction, also becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2. Since the second portion 22 is in close contact with the recess 44, the circumferential width of the portion 22c of the second portion 22 sandwiched between the two ends 41, 42 also becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2.

[0034] FIG. 4 is a cross-sectional view showing a state in which the rotor core 20 is set in the molding die 8. FIG. 5 is a cross-sectional view showing a state in which the molding die 8 is filled with a magnet material to form the permanent magnet 4. The permanent magnet 4 is formed using the molding die 8 as shown in FIGS. 4 and 5, for example. First, as shown in FIG. 4, the second portion 22 and the first portion 21 of the rotor core 20 are set in the molding die 8. At this time, the second portion 22 is disposed in the recess 24 of the first portion 21 in a state where a cavity 81 for forming the permanent magnet 4 is formed between the second portion 22 and the first portion 21. Subsequently, as shown in FIG. 5, a magnet material to form the permanent magnet 4 is injected into the cavity 81 in the molding die 8, whereby the permanent magnet 4 is integrally formed with the rotor core 20.

[0035] When a current is supplied to the winding 62 of the stator 6 to form a rotating magnetic field, a magnet torque is generated by the plurality of permanent magnets 4 and a reluctance torque is generated by the rotor core 20. The rotor 1 rotates about the rotation axis A by these magnet torque and reluctance torque.

[0036] As described above, since the end portions 41 and 42 of the permanent magnet 4 are exposed from the outer peripheral surface 28 of the rotor body 2, a leakage magnetic flux (magnetic flux short circuit) in which the magnetic flux generated by the permanent magnet 4 returns to the permanent magnet 4 without linking to the winding 62 of the stator 6 is less likely to occur. Specifically, from the viewpoint of magnet torque, it is preferable that more magnetic flux exits from the permanent magnet 4 to the outside of the outer peripheral surface 28 of the rotor body 2 and more magnetic flux enters the permanent magnet 4 from the outside of the outer peripheral surface 28. However, when the end portions 41 and 42 of the permanent magnet 4 magnetized in the direction intersecting the reference line R are completely surrounded by the rotor body 2, a part of the magnetic flux generated by the permanent magnet 4 can wrap around the portion outside the end portions 41 and 42 in the rotor body 2 and immediately return to the permanent magnet 4. When such a leakage magnetic flux occurs, the magnetic flux contributing to the magnet torque decreases. On the other hand, in this example, the end portions 41 and 42 of the permanent magnet 4 are exposed from the outer peripheral surface 28 of the rotor body 2. There is no rotor body 2 with a higher magnetic permeability than the permanent magnet 4 on the radially outer side of the exposed end portions 41 and 42. For this reason, a magnetic flux that wraps around the outside of the end portions 41 and 42 and immediately returns to the permanent magnet 4, that is, a leakage magnetic flux is less likely to occur. As a result, the amount of magnetic flux passing through the d-axis of the permanent magnet 4 increases, and the magnet torque is improved. In particular, in this example, since both of the two end portions 41 and 42 of the permanent magnet 4 are exposed from the outer peripheral surface 28 of the rotor body 2, the leakage magnetic flux around both end portions 41 and 42 is reduced. As a result, the magnet torque is further improved.

[0037] Incidentally, when two end portions 41 and 42 of the permanent magnet 4 that are curved or bent inward in the radial direction are exposed from the outer peripheral surface 28 of the rotor body 2, the rotor body 2 is divided into a first portion 21 and a second portion 22 by the permanent magnet 4. For this reason, there is a risk that the second portion 22 that has received centrifugal force during rotation of the rotor 1 may come off and separate from the permanent magnet 4. Further, when the permanent magnet 4 receives centrifugal force during rotation of the rotor 1, there is a risk that the permanent magnet 4 may come off and separate from the first portion 21. However, in this example, the width W1 in the circumferential direction from one end portion 41 to the other end portion 42 of the two end portions 41 and 42 of the permanent magnet 4 becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2. For this reason, when the permanent magnet 4 receives centrifugal force during rotation of the rotor 1, the permanent magnet 4 is supported from the outside in the radial direction by the rotor body 2 (specifically, the portions that contact the two end portions 41 and 42 on the inner surface 24a of the recess 24). Therefore, it becomes difficult for the permanent magnet 4 to come off from the first portion 21 of the rotor body 2.

[0038] Further, the width W2 in the circumferential direction of the portion 22c of the second portion 22 of the rotor body 2 that is sandwiched between the two end portions 41 and 42 of the permanent magnet 4 becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2. When the second portion 22 receives centrifugal force during rotation of the rotor 1, the second portion 22 is supported from the outside in the radial direction by the two end portions 41 and 42 of the permanent magnet 4. Therefore, it becomes difficult for the second portion 22 to come off from the permanent magnet 4.

[0039] Fig. 6 shows an enlarged cross-sectional view of the motor of the modified example. As shown in Fig. 6, at least one of the two end portions 41 and 42 of the permanent magnet 4 may be located radially inward of the outer peripheral surface 28 of the rotor body 2. In this example, both of the two end portions 41 and 42 of the permanent magnet 4 (specifically, both of the end faces 41a and 42a) are located radially inward of the outer peripheral surface 28 of the rotor body 2. In this case, the distance from the end portions 41 and 42 of the permanent magnet 4 to the stator 6 can be increased. Therefore, it is possible to make it difficult for the reverse magnetic field demagnetization of the permanent magnet 4 by the stator 6 to occur. Incidentally, the rotor 1 shown in Fig. 3 is advantageous in that the air resistance during the rotation of the rotor 1 can be reduced when the end faces 41a and 42a of the two end portions 41 and 42 of the permanent magnet 4 are flush with the outer peripheral surface 28 of the rotor body 2.

[0040] As described above, the rotor 1 includes a rotor body 2 that rotates around the rotation axis A, and a plurality of permanent magnets 4 that are arranged in the circumferential direction around the rotation axis A in the rotor body 2 and form different magnetic poles alternately in the circumferential direction. The cross-sectional shape of the permanent magnet 4 that is orthogonal to the rotation axis A has a shape that extends along a predetermined reference line R. The permanent magnet 4 is magnetized in a direction that intersects the reference line R in a cross-section orthogonal to the rotation axis A. At least one of the end portions 41 (or 42) of the permanent magnet 4 in the direction of the reference line R is exposed from the outer peripheral surface 28 of the rotor body 2.

[0041] The motor 100 also includes a rotor 1 and a stator 6 that drives the rotor 1.

[0042] According to these configurations, it is difficult for leakage magnetic flux generated by the magnetic flux generated by the permanent magnet 4 to pass through the radially outer sides of the end portions 41 and 42. Therefore, the magnet torque generated by the magnetic flux of the permanent magnet 4 can be improved.

[0043] Further, the permanent magnet 4 is curved or bent such that the two end portions 41 and 42 in the direction of the reference line R approach the outer peripheral surface 28 of the rotor body 2 more than the intermediate portion 43, and both of the two end portions 41 and 42 are exposed from the outer peripheral surface 28 of the rotor body 2. Each of the two end portions 41 and 42 of the permanent magnet 4 is exposed outside the rotor body 2.

[0044] According to this configuration, by forming the cross-sectional shape of the permanent magnet 4 into a shape that is curved or bent such that the two end portions 41 and 42 are closer to the outer peripheral surface 28 of the rotor body 2 than the intermediate portion 43, both of the two end portions 41 and 42 of the permanent magnet 4 can be exposed from the outer peripheral surface 28 of the rotor body 2. As a result, it is possible to further reduce the occurrence of leakage magnetic flux of the permanent magnet 4.

[0045] Further, the width W1 in the circumferential direction from one end portion 41 to the other end portion 42 of the two end portions 41 and 42 of the permanent magnet 4 becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2.

[0046] According to this configuration, when the permanent magnet 4 receives a centrifugal force during the rotation of the rotor 1, the permanent magnet 4 can be supported by the rotor body 2 from the radially outer side, and thereby, it is possible to make it difficult for the permanent magnet 4 to come off from the rotor body 2.

[0047] Further, the width W2 in the circumferential direction of the portion 22c of the rotor body 2 sandwiched between the two end portions 41 and 42 of the permanent magnet 4 becomes smaller as it approaches the outer peripheral surface 28 of the rotor body 2.

[0048] According to this configuration, when the portion 22c receives a centrifugal force during the rotation of the rotor 1, the portion 22c can be supported by the two end portions 41 and 42 of the permanent magnet 4 from the radially outer side, and thereby, it becomes difficult for the portion 22c to come off from the permanent magnet 4.

[0049] According to this configuration, it is possible to make it difficult for the permanent magnet 4 to be demagnetized by the counter magnetic field of the stator 6.

[0050] Further, at least one of the two end portions 41 and 42 of the permanent magnet 4 is located radially inward of the outer peripheral surface 28 of the rotor body 2 about the rotation axis A.

[0051] According to this configuration, the distance from the ends 41, 42 of the permanent magnet 4 to the stator 6 can be increased. Therefore, it is possible to make it difficult for the demagnetization of the permanent magnet 4 due to the stator 6 to occur.

[0052] In addition, the permanent magnet 4 is a bonded magnet.

[0053] According to this configuration, the permanent magnet 4 is easily formed into a desired shape.

[0054] 《Other embodiments》 As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are appropriately performed. It is also possible to combine the components described in the above embodiment to create a new embodiment. In addition, the components described in the attached drawings and detailed description may include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are described in the attached drawings or detailed description should not be used to immediately determine that these non-essential components are essential.

[0055] The rotor body 2 may be formed only by the rotor core 20 without including the shaft 5. The rotor body 2 may be formed only by the shaft 5 without including the rotor core 20. The shaft 5 does not have to be made of a soft magnetic material. The shaft 5 may be integrally formed with the rotor core 20. The first part 21 and the second part 22 of the rotor body 2 are not limited to being separated. As shown in FIG. 7, the permanent magnet 4 may have a connecting portion 27 that connects the first part 21 and the second part 22. In this case, since the second part 22 is connected to the first part 21 via the connecting portion 27, the second part 22 does not come off from the permanent magnet 4 when the rotor 1 rotates. Also, since the permanent magnet 4 is held by the mutually connected first part 21 and second part 22, the permanent magnet 4 also does not come off from the first part 21. Therefore, when the first part 21 and the second part 22 are connected by the connecting portion 27 in this way, the width W1 of the two end portions 41, 42 of the permanent magnet 4 does not have to become smaller as it approaches the outer peripheral surface of the rotor body 2, and the width W2 in the circumferential direction of the portion 22c of the rotor body 2 sandwiched between the two end portions 41, 42 of the permanent magnet 4 does not have to become smaller as it approaches the outer peripheral surface of the rotor body 2.

[0056] The number of permanent magnets 4 included in the rotor 1 is not limited. The permanent magnet 4 may be an anisotropic bonded magnet or an isotropic bonded magnet. The permanent magnet 4 may be a sintered magnet formed by sintering magnetic powder. The cross-sectional shape of the permanent magnet 4 is not limited. The cross-sectional shape of the permanent magnet 4 may be, for example, V-shaped or W-shaped. Only one of the two end portions 41, 42 of the permanent magnet 4 may be exposed from the outer peripheral surface 28 of the rotor body 2. For example, the permanent magnet 4 may be flat (i.e., the cross-sectional shape is linear), and only one of the end portions at both ends in the cross-sectional shape may be exposed from the outer peripheral surface 28 of the rotor body 2.

[0057] The width W1 of the two end portions 41, 42 of the permanent magnet 4 does not have to become smaller as it approaches the outer peripheral surface of the rotor body 2. The width W2 in the circumferential direction of the portion 22c of the rotor body 2 sandwiched between the two end portions 41, 42 of the permanent magnet 4 does not have to become smaller as it approaches the outer peripheral surface of the rotor body 2.

Description of Symbols

[0058] 100 Motor 1 Rotor 2 Rotor Body 22c Portion 28 Outer Peripheral Surface 4 Permanent Magnet 41 End 42 End 43 Middle Portion 6 Stator R Reference Line A Rotation Axis W1 Width W2 Width

Claims

1. A rotor body that rotates around a rotation axis; a plurality of permanent magnets arranged in a circumferential direction around the rotation axis in the rotor body and forming magnetic poles that are alternately different in the circumferential direction, A cross-sectional shape of the permanent magnet perpendicular to the rotation axis extends along a predetermined reference line, the permanent magnet is magnetized in a direction intersecting the reference line in a cross section perpendicular to the rotation axis, the permanent magnet is curved or bent such that two ends in the direction of the reference line are closer to the outer circumferential surface of the rotor body than a middle portion of the permanent magnet, Both of the two ends are exposed from the outer circumferential surface of the rotor body, A rotor in which the circumferential width from the circumferentially outer side surface of one of the two ends of the permanent magnet to the circumferentially outer side surface of the other end decreases with increasing distance from the rotation axis.

2. 2. The rotor according to claim 1, A rotor in which the width in the circumferential direction of a portion of the rotor body sandwiched between the two ends of the permanent magnet decreases with increasing distance from the rotation axis.

3. In claim 1 or 2, A rotor in which at least one of the two ends of the permanent magnet is located radially inward about the rotation axis than the outer circumferential surface of the rotor body.

4. A rotor according to any one of claims 1 to 3, The rotor, wherein the permanent magnet is a bonded magnet.

5. A rotor according to any one of claims 1 to 4; and a stator that drives the rotor.

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