Rotor and motor

Abstract

A rotor 2 comprises: a rotor body 3 that rotates about a rotational axis X; a plurality of main magnets 41 and a plurality of auxiliary magnets 42 which are arranged, on a peripheral surface of the rotor body 3, alternatingly in a circumferential direction centered on the rotational axis X; and magnetic bodies 43 that, for main magnets 41 and auxiliary magnets 42 which are adjacent in the circumferential direction, are disposed at at least one of a first position L1 which is between an auxiliary magnet 42 and the rotor body 3 and which is further toward a main magnet 41 than the circumferential direction center C2 of the auxiliary magnet 42 and a second position L2 which is between the main magnet 41 and the rotor body 3 and which is further toward the auxiliary magnet 42 than the circumferential direction center C1 of the main magnet 41. The plurality of main magnets 41 are each magnetized along a radial direction centered on the rotational axis X. The plurality of auxiliary magnets 42 are each magnetized in a direction differing from the radial direction. The plurality of main magnets 41 and the plurality of auxiliary magnets 42 are arranged in a Halbach array such that a magnetic field on the opposite side from the rotor body 3 is stronger than a magnetic field on the rotor body 3 side.

Description

Rotor and motor

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

[0002] Patent Document 1 discloses a motor including a rotor and a stator that faces the rotor and rotates the rotor. The rotor has a rotor core that rotates about a rotation axis and multiple permanent magnets arranged on the circumferential surface of the rotor core facing the stator. The multiple permanent magnets are arranged in a Halbach array so that the magnetic field on the stator side of the multiple permanent magnets is stronger than the magnetic field on the opposite side of the multiple permanent magnets from the stator. Specifically, the multiple permanent magnets include main magnets and auxiliary magnets arranged alternately in the circumferential direction of the rotor core. The main magnets are magnetized radially about the rotation axis. The auxiliary magnets are magnetized circumferentially.

[0003] Japanese Patent Application Laid-Open No. 2021-40413

[0004] However, in the motor described above, there is a risk of the main magnet being demagnetized on the side opposite the stator where the magnetic field is weaker. Specifically, on the side opposite the stator, part of the magnetic flux of the auxiliary magnets passing through the main magnet cancels out the magnetic flux of the main magnet, causing the main magnet to be demagnetized. If the main magnet is demagnetized, there is a risk that the performance of the motor will be affected.

[0005] The technology disclosed herein has been made in consideration of these points, and its purpose is to reduce demagnetization of the main magnet.

[0006] The rotor disclosed herein comprises a rotor body that rotates around a rotation axis, a plurality of main magnets and a plurality of auxiliary magnets that are alternately arranged on the peripheral surface of the rotor body along a circumferential direction centered on the rotation axis, and a magnetic body that is arranged in at least one of a first position between the auxiliary magnet and the rotor body and located closer to the main magnet with respect to the circumferential center of the auxiliary magnet, and a second position between the main magnet and the rotor body and located closer to the auxiliary magnet with respect to the circumferential center of the main magnet, each of the plurality of main magnets being magnetized in a radial direction centered on the rotation axis, and each of the plurality of auxiliary magnets being magnetized in a direction different from the radial direction, and the plurality of main magnets and the plurality of auxiliary magnets being arranged in a Halbach array so that the magnetic field on the side opposite the rotor body with respect to the plurality of main magnets and the plurality of auxiliary magnets is stronger than the magnetic field on the rotor body side with respect to the plurality of main magnets and the plurality of auxiliary magnets.

[0007] The motor disclosed herein includes a rotor that rotates around a rotation axis, and a stator that faces the rotor and rotates the rotor around the rotation axis, the rotor including a rotor body, a plurality of main magnets and a plurality of auxiliary magnets that are alternately arranged along a circumferential direction about the rotation axis on a peripheral surface of the rotor body that faces the stator, and a first position or a second position of the main magnets that are adjacent to each other in the circumferential direction and are located between the auxiliary magnets and the rotor body and closer to the main magnets with respect to the circumferential center of the auxiliary magnets. and a magnetic body arranged at least in one of the second positions between the stone and the rotor body and located closer to the auxiliary magnet with respect to the circumferential center of the main magnet, wherein each of the plurality of main magnets is magnetized in a radial direction centered on the rotation axis, and each of the plurality of auxiliary magnets is magnetized in a direction different from the radial direction, and the plurality of main magnets and the plurality of auxiliary magnets are arranged in a Halbach array so that the magnetic field on the stator side relative to the plurality of main magnets and the plurality of auxiliary magnets is stronger than the magnetic field on the rotor body side relative to the plurality of main magnets and the plurality of auxiliary magnets.

[0008] The rotor and the motor can reduce demagnetization of the main magnet.

[0009] FIG. 1 is a cross-sectional view of a motor according to an embodiment. FIG. 2 is a cross-sectional view of a rotor according to an embodiment. FIG. 3 is an enlarged view of a portion of FIG. 2. FIG. 4 is a developed view of a partial cross section of a rotor illustrating the flow of magnetic flux of an auxiliary magnet. FIG. 5 is a developed view of a partial cross section of a rotor according to Modification 1. FIG. 6 is a developed view of a partial cross section of a rotor according to Modification 2. FIG. 7 is a developed view of a partial cross section of a rotor according to Modification 3. FIG. 8 is a developed view of a partial cross section of a rotor according to Modification 4. FIG. 9 is a developed view of a partial cross section of a rotor according to Modification 5. FIG. 10 is a developed view of a partial cross section of a rotor according to Modification 6. FIG. 11 is an enlarged cross-sectional view of a portion of a rotor according to Modification 7. FIG. 12 is an enlarged cross-sectional view of a portion of a rotor according to Modification 8. FIG. 13 is a diagram showing analysis results of motor torque waveforms in examples when the rotor according to the embodiment, the rotor according to Modification 7, and the rotor according to Modification 8 are applied to motors. FIG. 14 is a diagram showing analysis results of the demagnetization factor of the main magnet in an example when the rotor according to the embodiment is applied to a motor. FIG. 15 is a diagram showing the analysis results of the demagnetization factor of the main magnet in a comparative example when a rotor without a magnetic body is applied to a motor.

[0010] An exemplary embodiment will be described in detail below with reference to the drawings. Fig. 1 is a cross-sectional view of a motor 100. In Fig. 1, main magnets and auxiliary magnets, which will be described later, are indicated by dots instead of hatching. The same applies to the other figures.

[0011] The motor 100 includes a rotor 2 that rotates about a rotation axis X, and a stator 6 that faces the rotor 2 and rotates the rotor 2 about the rotation axis X. Hereinafter, the direction in which the rotation axis X extends will be referred to as the "rotation axis direction." The circumferential direction about the rotation axis X will be simply referred to as the "circumferential direction." The radial direction about the rotation axis X will be simply referred to as the "radial direction." The motor 100 may further include a motor case 7 that houses the rotor 2 and the stator 6.

[0012] The stator 6 has a stator core 61 and windings 62. The stator core 61 is made of a soft magnetic material. The stator core 61 is, for example, a plurality of laminated electromagnetic steel plates. The stator core 61 is formed in a cylindrical shape centered on the rotation axis X. The stator core 61 is fixed to, for example, the motor case 7. The stator core 61 is formed with a plurality of teeth 61a that protrude toward the inside of the stator core 61. The plurality of teeth 61a are arranged at intervals in the circumferential direction. The windings 62 are wound around the plurality of teeth 61a. The windings 62 are formed by winding a conductor around each tooth 61a. When a current is supplied to the windings 62 of the stator 6, a rotating magnetic field that rotates the rotor 2 is generated.

[0013] FIG. 2 is a cross-sectional view of the rotor 2. Note that "N" and "S" in FIG. 2 indicate the polarity of the magnetic poles formed on the rotor 2. The arrows drawn on the magnets in FIG. 2 indicate the magnetization direction. The rotor 2 is disposed inside the stator core 61. In other words, the rotor 2 is an inner rotor. The rotor 2 includes a rotor body 3 that rotates around the rotation axis X, a plurality of main magnets 41 and a plurality of auxiliary magnets 42 disposed on the rotor body 3, and a plurality of magnetic bodies 43 disposed on the rotor body 3. The rotor 2 may further include a sleeve 5 that covers the plurality of main magnets 41 and the plurality of auxiliary magnets 42 from the radial outside.

[0014] The rotor body 3 includes a rotor core 31 and a shaft 32. The rotor core 31 is a soft magnetic material. The rotor core 31 is, for example, an iron core. The rotor core 31 is formed, for example, from a plurality of electromagnetic steel plates stacked on top of each other. The rotor core 31 is formed in a cylindrical shape. Specifically, the rotor core 31 is formed in a cylindrical shape with the rotation axis X as its axis. The outer peripheral surface of the rotor core 31 is the outer peripheral surface of the rotor body 3. The rotor core 31 is arranged so that the outer peripheral surface of the rotor core 31 faces the inner peripheral surface of the stator 6. In other words, the outer peripheral surface of the rotor body 3 is the peripheral surface of the rotor body 3 on the stator 6 side.

[0015] The shaft 32 is fitted inside the rotor core 31. The shaft 32 is fixed to the rotor core 31. The shaft 32 is made of a soft magnetic material. The axis of the shaft 32 coincides with the rotation axis X. The shaft 32 is rotatably supported by the motor case 7 via bearings or the like. The rotor core 31 rotates around the rotation axis X together with the shaft 32.

[0016] The multiple main magnets 41 and the multiple auxiliary magnets 42 are arranged on the circumferential surface of the rotor body 3, specifically, on the outer circumferential surface of the rotor body 3. The multiple main magnets 41 and the multiple auxiliary magnets 42 are arranged alternately along the circumferential direction. In other words, the motor 100 is an SPM (Surface Permanent Magnet) motor. The main magnets 41 and the auxiliary magnets 42 are, for example, neodymium magnets, samarium-iron-nitrogen magnets, samarium-cobalt magnets, ferrite magnets, or alnico magnets. The main magnets 41 and the auxiliary magnets 42 are, for example, sintered magnets formed by sintering magnetic powder.

[0017] The main magnet 41 and the auxiliary magnet 42 are formed in a plate shape. The main magnet 41 and the auxiliary magnet 42 have length, width, and thickness directions that are perpendicular to one another. The main magnet 41 and the auxiliary magnet 42 extend in an arc shape in the width direction. The length direction of the main magnet 41 and the auxiliary magnet 42 coincides with the direction of the rotation axis X. The width direction of the main magnet 41 and the auxiliary magnet 42 coincides with the circumferential direction. The thickness direction of the main magnet 41 and the auxiliary magnet 42 coincides with the radial direction. The main magnet 41 and the auxiliary magnet 42 face the stator 6.

[0018] The main magnets 41 and the auxiliary magnets 42 are arranged in a Halbach array along the circumferential direction. A "Halbach array" is an array that increases the magnetic field strength in a specific direction by adjusting the magnetization direction of each magnet. Specifically, the main magnets 41 and the auxiliary magnets 42 are arranged in a Halbach array so that the magnetic field on the side opposite the rotor body 3 (i.e., the stator 6 side) of the main magnets 41 and the auxiliary magnets 42 is stronger than the magnetic field on the rotor body 3 side of the main magnets 41 and the auxiliary magnets 42.

[0019] Each of the multiple main magnets 41 is magnetized in a radial direction centered on the rotation axis X. Here, "magnetized in a radial direction" means magnetized in a direction that substantially coincides with the radial direction, and is not limited to magnetization in a direction that completely coincides with the radial direction.

[0020] Specifically, the main magnets 41 forming the N poles are magnetized from the radially inner side toward the radially outer side. The main magnets 41 forming the N poles are hereinafter also referred to as first main magnets 41a. The magnetization direction of the first main magnets 41a is linear, and extends from the radially inner side toward the radially outer side. In this example, the rotor 2 has five first main magnets 41a.

[0021] The main magnets 41 forming the south poles are magnetized from the radially outer side toward the radially inner side. The main magnets 41 forming the south poles are hereinafter also referred to as second main magnets 41b. The magnetization direction of the second main magnets 41b is linear, and is from the radially outer side toward the radially inner side. In this example, the rotor 2 has five second main magnets 41b, the same number as the first main magnets 41a.

[0022] With respect to the multiple main magnets 41, the first main magnets 41a and the second main magnets 41b are arranged alternately in the circumferential direction. In other words, the polarities of the first main magnets 41a and the second main magnets 41b are alternately different in the circumferential direction. When there is no need to distinguish between the first main magnets 41a and the second main magnets 41b, they will be simply referred to as the "main magnets 41."

[0023] Each of the multiple auxiliary magnets 42 is magnetized in a direction different from the radial direction. In this example, the auxiliary magnets 42 are magnetized in the circumferential direction. More specifically, the auxiliary magnets 42 are magnetized in a direction perpendicular to the radial direction when viewed from the direction of the rotation axis X. Here, "magnetized in the circumferential direction" means being magnetized in a direction that substantially coincides with the circumferential direction, and is not limited to being magnetized in a direction that completely coincides with the circumferential direction.

[0024] Specifically, each auxiliary magnet 42 is disposed between the first main magnet 41 a and the second main magnet 41 b. The auxiliary magnets 42 are magnetized from the second main magnet 41 b toward the first main magnet 41 a. The magnetization direction of the auxiliary magnets 42 is linear, from the second main magnet 41 b toward the first main magnet 41 a. In this example, the rotor 2 has ten auxiliary magnets 42, the same number as the main magnets 41.

[0025] When a current is supplied to the windings 62 of the stator 6, a rotating magnetic field is generated by the stator 6, and a magnetic torque is generated by the plurality of main magnets 41 and the plurality of auxiliary magnets 42. This magnetic torque causes the rotor 2 to rotate about the rotation axis X.

[0026] The sleeve 5 covers the periphery of the multiple main magnets 41 and the multiple auxiliary magnets 42. The sleeve 5 is made of, for example, high-strength metal or FRP (Fiber Reinforced Plastics). The sleeve 5 can prevent the multiple main magnets 41 and the multiple auxiliary magnets 42 from scattering radially outward even if the multiple main magnets 41 and the multiple auxiliary magnets 42 are subjected to centrifugal force during rotation of the rotor. The multiple main magnets 41 and the multiple auxiliary magnets 42 may be fixed to the outer circumferential surface of the rotor body 3 with an adhesive.

[0027] The magnetic body 43 is formed, for example, from a material different from that of the rotor body 3. The material of the magnetic body 43 is, for example, a powder iron core or stainless steel. The magnetic permeability or saturation magnetic flux density of the magnetic body 43 is, for example, higher than the magnetic permeability or saturation magnetic flux density of the rotor body 3. In this case, magnetic flux passes through the magnetic body 43 more easily than through the rotor body 3. Note that the magnetic body 43 may be formed, for example, from the same material as the rotor body 3.

[0028] The magnetic body 43 has a length direction, a width direction, and a thickness direction that are perpendicular to one another. The length direction of the magnetic body 43 coincides with the direction of the rotation axis X. The width direction of the magnetic body 43 coincides with the circumferential direction. The thickness direction of the magnetic body 43 coincides with the radial direction.

[0029] The magnetic body 43 is arranged in circumferentially adjacent main magnets 41 and auxiliary magnets 42 among the multiple main magnets 41 and multiple auxiliary magnets 42 at at least one of a first position located between the auxiliary magnet 42 and the rotor body 3 and closer to the main magnet 41 with respect to the circumferential center of the auxiliary magnet 42, or a second position located between the main magnet 41 and the rotor body 3 and closer to the auxiliary magnet 42 with respect to the circumferential center of the main magnet 41. In this example, the magnetic body 43 is arranged at either the first position or the second position. More specifically, the magnetic body 43 is arranged at the first position. All of the magnetic bodies 43 are arranged at the first position. The magnetic body 43 is arranged only at the first position.

[0030] Figure 3 is an enlarged view of a portion of Figure 2. Two magnetic bodies 43 are arranged between one auxiliary magnet 42 and the rotor main body 3. One of the two magnetic bodies 43 will hereinafter also be referred to as a first magnetic body 43a. The other of the two magnetic bodies 43 will hereinafter also be referred to as a second magnetic body 43b. When there is no need to distinguish between the first magnetic body 43a and the second magnetic body 43b, they will simply be referred to as "magnetic bodies 43."

[0031] The first magnetic body 43a is disposed at a first position L1 between the auxiliary magnet 42 and the rotor body 3, in the first main magnet 41a and the auxiliary magnet 42, which are adjacent to each other in the circumferential direction. The first magnetic body 43a faces the first main magnet 41a. In this example, the rotor 2 has ten first magnetic bodies 43a.

[0032] The second magnetic body 43b is disposed at a first position L1 between the auxiliary magnet 42 and the rotor body 3, the first position L1 being closer to the second main magnet 41b than the circumferential center C2 of the auxiliary magnet 42, in the second main magnet 41b and the auxiliary magnet 42, which are adjacent to each other in the circumferential direction. The second magnetic body 43b faces the second main magnet 41b. In this example, the rotor 2 has ten second magnetic bodies 43b, the same number as the first magnetic bodies 43a.

[0033] In this way, when one auxiliary magnet 42 is used as a reference, the main magnets 41 are adjacent to the left and right of the reference auxiliary magnet 42 in the circumferential direction, and therefore the first positions L1 are located on the left and right of the reference auxiliary magnet 42 in the circumferential direction. In other words, the two first positions L1 are located at positions symmetrical in the circumferential direction with respect to the center C2 of the reference auxiliary magnet 42.

[0034] The auxiliary magnet 42 has a groove 421 provided on the surface of the auxiliary magnet 42 facing the rotor body 3. The groove 421 opens on the surface of the auxiliary magnet 42 facing the rotor body 3 and on the surface of the auxiliary magnet 42 facing the main magnet 41. The magnetic body 43 is fitted into the groove 421. In this way, the groove 421 corresponds to the first position L1.

[0035] Specifically, the auxiliary magnet 42 has two grooves 421. One of the two grooves 421 opens to a surface of the auxiliary magnet 42 facing the rotor body 3 and a surface of the auxiliary magnet 42 facing the first main magnet 41a. The other of the two grooves 421 opens to a surface of the auxiliary magnet 42 facing the rotor body 3 and a surface of the auxiliary magnet 42 facing the second main magnet 41b. The first magnetic body 43a is fitted into one of the grooves 421. The second magnetic body 43b is fitted into the other groove 421. The first magnetic body 43a contacts the first main magnet 41a and the auxiliary magnet 42 and the rotor core 31 of the rotor body 3. The second magnetic body 43b contacts the second main magnet 41b and the auxiliary magnet 42 and the rotor core 31 of the rotor body 3.

[0036] The circumferential width of the radially outer portion of the groove 421 is narrower than the circumferential width of the radially inner portion of the groove 421. Specifically, the circumferential width of the groove 421 continuously narrows from the radially inner side to the radially outer side. In this example, the cross section of the groove 421 is triangular. One groove 421 and the other groove 421 have shapes that are circumferentially symmetrical with respect to the center C2 of the auxiliary magnet 42. Note that the circumferential width of the groove 421 may narrow stepwise from the radially inner side to the radially outer side, and the cross section of the groove 421 is not limited to a triangle.

[0037] The circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43. Specifically, the circumferential width of the magnetic body 43 continuously narrows from the radially inner side to the radially outer side. In this example, the cross section of the magnetic body 43 is triangular. The first magnetic body 43a and the second magnetic body 43b have shapes that are circumferentially symmetrical with respect to the center C2 of the auxiliary magnet 42. Note that the circumferential width of the magnetic body 43 may narrow stepwise from the radially inner side to the radially outer side, and the cross section of the magnetic body 43 is not limited to a triangle.

[0038] Figure 4 is a partially cross-sectional development of the rotor 2, illustrating the flow of magnetic flux in the auxiliary magnet 42. Although Figure 4 is a cross-sectional view, hatching has been omitted. Figure 4 shows the circumferential direction of the rotor 2, developed in a linear direction. In Figure 4, the solid arrow drawn on the main magnet 41 indicates the magnetization direction of the main magnet 41, the solid arrow drawn on the auxiliary magnet 42 indicates the magnetization direction of the auxiliary magnet 42, and the dotted arrow indicates the magnetic flux lines of the auxiliary magnet 42. The "N" and "S" shown in Figure 4 indicate the polarities of the magnetic poles formed in each magnet 41, 42.

[0039] The magnetic flux of the auxiliary magnet 42 that flows on the stator 6 side, i.e., the upper side in Figure 4, flows in the same direction as the magnetization direction of the main magnet 41, and therefore the magnetic field on the stator 6 side is strengthened. On the other hand, the magnetic flux of the auxiliary magnet 42 that flows on the rotor body 3 side, i.e., the lower side in Figure 4, flows in the opposite direction to the magnetization direction of the main magnet 41, and therefore the magnetic field on the rotor body 3 side is weakened.

[0040] Since the magnetic body 43 is disposed between the auxiliary magnet 42 and the rotor body 3 and closer to the main magnet 41, the magnetic flux of the auxiliary magnet 42 that flows on the rotor body 3 side passes through the rotor body 3 via the magnetic body 43 without passing through the main magnet 41. This makes it possible to mitigate the magnetic flux of the auxiliary magnet 42 canceling out the magnetic flux of the main magnet 41 on the rotor body 3 side. Therefore, demagnetization of the main magnet 41 can be reduced.

[0041] More specifically, if the magnetic body 43 is not provided, the magnetic flux of the auxiliary magnet 42 that flows on the rotor body 3 side passes through the main magnet 41, as shown by the two-dot chain arrow. As a result, the magnetic flux of the auxiliary magnet 42 that passes through the main magnet 41 on the rotor body 3 side cancels out the magnetic flux of the main magnet 41, demagnetizing the main magnet 41. In contrast, by providing the magnetic body 43 as shown in Figure 4, the magnetic flux of the auxiliary magnet 42 that passes through the main magnet 41 on the rotor body 3 side can be reduced, and demagnetization of the portion of the main magnet 41 on the rotor body 3 side, more specifically, the portion A surrounded by an ellipse, can be reduced.

[0042] According to the rotor 2 described above, the magnetic body 43 is disposed at the first position L1, so that, on the rotor body 3 side, with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42, some of the magnetic flux of the auxiliary magnets 42 can pass to the rotor body 3 via the magnetic body 43 without passing through the main magnets 41. This makes it possible to mitigate the magnetic flux of the auxiliary magnets 42 canceling out the magnetic flux of the main magnets 41 on the rotor body 3 side. Therefore, demagnetization of the main magnets 41 can be reduced.

[0043] Furthermore, because the magnetic body 43 is disposed at the first position L1, a groove 421 can be formed on the surface of the auxiliary magnet 42 facing the rotor body 3, and the magnetic body 43 can be attached to the groove 421. In this case, compared to when the magnetic body 43 is disposed at the first position L1 and the second position, it is not necessary to form a groove on the surface of the main magnet 41 facing the rotor body 3, and the effort required to form the groove can be reduced.

[0044] Furthermore, because the magnetic body 43 is disposed at the first position L1, a groove 421 can be provided on the surface of the auxiliary magnet 42 facing the rotor body 3, and the magnetic body 43 can be attached to the groove 421. In this case, it is not necessary to provide a groove on the surface of the main magnet 41 facing the rotor body 3, and a reduction in the volume of the main magnet 41 can be suppressed. This can improve the torque performance of the rotor 2. In particular, because the main magnet 41 contributes more to the torque performance of the rotor 2 than the auxiliary magnet 42, even if the volume of the auxiliary magnet 42 is reduced, the torque performance of the rotor 2 can be improved by suppressing a reduction in the volume of the main magnet 41.

[0045] The motor 100 described above has the rotor 2 described above, which can reduce demagnetization of the main magnet 41. By reducing the demagnetization of the main magnet 41, the torque performance of the rotor 2 is improved, and the performance of the motor 100 is improved.

[0046] <<Modification 1>> Fig. 5 is a development view of a partial cross section of a rotor 2A according to Modification 1. Fig. 5 shows the rotor 2A developed linearly in the circumferential direction. The rotor 2A according to Modification 1 differs from the rotor 2 according to the embodiment in the configuration of the magnetic body 43. The following description will focus on the configuration of the rotor 2A according to Modification 1 that differs from the rotor 2 according to the embodiment. Note that the other configurations are the same as the rotor 2 according to the embodiment, and therefore description thereof will be omitted.

[0047] In the rotor 2A according to the first modification, the magnetic bodies 43 are integrated with the rotor body 3. For example, the magnetic bodies 43 are integrally molded with the rotor body 3. Preferably, all of the magnetic bodies 43 are integrated with the rotor body 3. Note that at least one of all the magnetic bodies 43 may be integrated with the rotor body 3.

[0048] According to the rotor 2A of variant 1, the magnetic body 43 is arranged on the outer peripheral surface of the rotor body 3 together with the main magnet 41 and the auxiliary magnet 42, and even if the magnetic body 43 is subjected to centrifugal force when the rotor 2A rotates, the magnetic body 43 is integrated with the rotor body 3, so that the magnetic body 43 can be prevented from scattering radially outward.

[0049] Furthermore, since the only parts that may fly outward in the radial direction when the rotor 2A rotates are the main magnets 41 and the auxiliary magnets 42, the total weight of the parts that fly off is reduced, and the centrifugal force acting on the sleeve 5 that surrounds the outer periphery of the main magnets 41 and the auxiliary magnets 42 is reduced.

[0050] Furthermore, since the magnetic body 43 is integrated with the rotor body 3, the number of parts can be reduced, and the manufacturability of the rotor 2A can be improved.

[0051] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2 according to the embodiment can be used to describe the rotor 2A according to the first modified example.

[0052] <<Modification 2>> Fig. 6 is a partial cross-sectional development of a rotor 2B according to Modification 2. Fig. 6 shows the rotor 2B expanded linearly in the circumferential direction. The rotor 2B according to Modification 2 differs from the rotor 2A according to Modification 1 in the configuration of the magnetic body 43 and the grooves 421 of the auxiliary magnets 42. The following description will focus on the configuration of the rotor 2B according to Modification 2 that differs from the rotor 2A according to Modification 1. Note that the other configurations are the same as those of the rotor 2A according to Modification 1, and therefore description thereof will be omitted.

[0053] In the rotor 2B according to the second modification, the magnetic body 43 is integrated with the rotor main body 3, and the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43. Specifically, the circumferential width of the magnetic body 43 increases continuously from the radially inner side to the radially outer side. In this example, the cross section of the magnetic body 43 is trapezoidal. The first magnetic body 43a and the second magnetic body 43b have shapes that are circumferentially symmetrical with respect to C2 of the auxiliary magnet 42. Note that the circumferential width of the magnetic body 43 may increase stepwise from the radially inner side to the radially outer side, and the cross section of the magnetic body 43 is not limited to a trapezoid.

[0054] The circumferential width of the radially outer portion of the groove 421 is wider than the circumferential width of the radially inner portion of the groove 421. Specifically, the circumferential width of the groove 421 increases continuously from the radially inner side to the radially outer side. In this example, the cross section of the groove 421 is trapezoidal. One groove 421 and the other groove 421 have shapes that are circumferentially symmetrical with respect to the center C2 of the auxiliary magnet 42. Note that the circumferential width of the groove 421 may increase stepwise from the radially inner side to the radially outer side, and the cross section of the groove 421 is not limited to a trapezoid.

[0055] Preferably, all of the magnetic bodies 43 have the above-described shape. However, at least one of all of the magnetic bodies 43 may have the above-described shape.

[0056] According to the rotor 2B of the second variant, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43. Therefore, even if the auxiliary magnet 42 is subjected to centrifugal force when the rotor 2B rotates, the auxiliary magnet 42 is engaged with the magnetic body 43, thereby preventing the auxiliary magnet 42 from scattering radially outward.

[0057] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2A according to the first modification can be used to describe the rotor 2B according to the second modification.

[0058] <<Modification 3>> Fig. 7 is a development view of a partial cross section of a rotor 2C according to Modification 3. Fig. 7 shows the rotor 2C developed linearly in the circumferential direction. The rotor 2C according to Modification 3 differs from the rotor 2 according to the embodiment in the configuration of the magnetic body 43 and the grooves 421 of the auxiliary magnets 42, and also differs in that the rotor body 3 has grooves 311. The following description will focus on the configuration of the rotor 2C according to Modification 3 that differs from the rotor 2 according to the embodiment. Note that the other configurations are the same as those of the rotor 2 according to the embodiment, and therefore description thereof will be omitted.

[0059] In the rotor 2C according to the third modification, the auxiliary magnet 42 has a groove 421 provided on a surface of the auxiliary magnet 42 facing the rotor body 3. The groove 421 is an example of a first groove. The rotor body 3 has a groove 311 provided on a surface of the rotor body 3 facing the auxiliary magnet 42 and facing the groove 421. The groove 311 is an example of a second groove. The magnetic body 43 is fitted into the groove 421 and the groove 311.

[0060] Specifically, the groove 421 opens to a surface of the auxiliary magnet 42 facing the rotor body 3 and a surface of the auxiliary magnet 42 facing the main magnet 41. In this example, the cross section of the groove 421 is rectangular. However, the cross section of the groove 421 is not limited to a rectangular shape.

[0061] The groove 311 opens to a surface of the rotor core 31 facing the auxiliary magnet 42. The groove 311 communicates with the groove 421. In this example, the cross section of the groove 311 is rectangular. However, the cross section of the groove 311 is not limited to a rectangular shape.

[0062] The magnetic body 43 is fitted across both the groove 421 and the groove 311. The cross section of the magnetic body 43 corresponds to the shapes of the grooves 311 and 421. In this example, the cross section of the magnetic body 43 is rectangular. However, the cross section of the magnetic body 43 is not limited to a rectangular shape.

[0063] Preferably, grooves 311 are provided opposite all of the grooves 421, and all of the magnetic bodies 43 are fitted into the grooves 421 and grooves 311. Alternatively, grooves 311 may be provided opposite at least one of all of the grooves 421, and at least one of all of the magnetic bodies 43 may be fitted into the grooves 421 and grooves 311.

[0064] According to the rotor 2C of the third modification, the magnetic body 43 is fitted into the groove 421 and the groove 311, which increases the contact area of ​​the magnetic body 43 with the auxiliary magnet 42 and the rotor body 3. This increases the magnetic flux of the auxiliary magnet 42 passing through the magnetic body 43 and the rotor body 3 on the rotor body 3 side, and further reduces the magnetic flux of the auxiliary magnet 42 from canceling out the magnetic flux of the main magnet 41 on the rotor body 3 side. Therefore, demagnetization of the main magnet 41 can be further reduced.

[0065] Furthermore, since the magnetic body 43 is fitted into the groove 311, the magnetic body 43 is positioned relative to the rotor body 3. Since the magnetic body 43 is fitted into the groove 421, the auxiliary magnet 42 is positioned relative to the rotor body 3 by the magnetic body 43. Therefore, the accuracy of positioning the auxiliary magnet 42 relative to the rotor body 3 is improved.

[0066] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2 according to the embodiment can be used to describe the rotor 2C according to the third modified example.

[0067] <<Modification 4>> Fig. 8 is a development view of a partial cross section of a rotor 2D according to Modification 4. Fig. 8 shows the rotor 2D developed linearly in the circumferential direction. The rotor 2D according to Modification 4 differs from the rotor 2C according to Modification 3 in the configuration of the magnetic body 43 and the grooves 421 of the auxiliary magnets 42. The following description will focus on the configuration of the rotor 2D according to Modification 4 that differs from the rotor 2C according to Modification 3. Note that the other configurations are the same as those of the rotor 2C according to Modification 3, and therefore description thereof will be omitted.

[0068] In the rotor 2D according to the fourth modification, in the region of the magnetic body 43 fitted in the groove 421, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43. In the region of the magnetic body 43 fitted in the groove 311, the circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43.

[0069] Specifically, the circumferential width of the radially outer portion of the groove 421 is wider than the circumferential width of the radially inner portion of the groove 421. More specifically, the circumferential width of the groove 421 increases continuously from the radially inner side to the radially outer side. In this example, the cross section of the groove 421 is trapezoidal. Note that the circumferential width of the groove 421 may increase stepwise from the radially inner side to the radially outer side, and the cross section of the groove 421 is not limited to a trapezoid.

[0070] One groove 421 into which the first magnetic body 43a is fitted and the other groove 421 into which the second magnetic body 43b is fitted have shapes that are symmetrical in the circumferential direction with respect to the center C2 of the auxiliary magnet 42. Note that the one groove 421 and the other groove 421 may have shapes that are asymmetrical in the circumferential direction with respect to C2 of the auxiliary magnet 42.

[0071] The circumferential width of the radially outer portion of the groove 311 is narrower than the circumferential width of the radially inner portion of the groove 311. Specifically, the circumferential width of the groove 311 continuously narrows from the radially inner side to the radially outer side. In this example, the cross section of the groove 311 is trapezoidal. Note that the circumferential width of the groove 311 may narrow stepwise from the radially inner side to the radially outer side, and the cross section of the groove 311 is not limited to a trapezoid.

[0072] One groove 311 into which the first magnetic body 43a is fitted and the other groove 311 into which the second magnetic body 43b is fitted have shapes that are symmetrical in the circumferential direction with respect to the center C2 of the auxiliary magnet 42. Note that the one groove 311 and the other groove 311 may have shapes that are asymmetrical in the circumferential direction with respect to C2 of the auxiliary magnet 42.

[0073] In the region of the magnetic body 43 that is fitted into the groove 421, the circumferential width of the magnetic body 43 increases continuously from the inside to the outside in the radial direction. In this example, the cross section of the magnetic body 43 is trapezoidal. Note that the circumferential width of the magnetic body 43 may increase stepwise from the inside to the outside in the radial direction, and the cross section of the magnetic body 43 is not limited to a trapezoid.

[0074] In the region of the magnetic body 43 that is fitted into the groove 311, the circumferential width of the magnetic body 43 continuously narrows from the inside to the outside in the radial direction. In this example, the cross section of the magnetic body 43 is trapezoidal. Note that the circumferential width of the magnetic body 43 may narrow stepwise from the inside to the outside in the radial direction, and the cross section of the magnetic body 43 is not limited to a trapezoid.

[0075] The first magnetic body 43a and the second magnetic body 43b have shapes that are symmetrical in the circumferential direction with respect to C2 of the auxiliary magnet 42. Note that the first magnetic body 43a and the second magnetic body 43b may have shapes that are asymmetrical in the circumferential direction with respect to C2 of the auxiliary magnet 42.

[0076] Preferably, all of the magnetic bodies 43 have the above-described shape. However, at least one of all of the magnetic bodies 43 may have the above-described shape.

[0077] According to the rotor 2D of variant example 4, in the region of the magnetic body 43 that is fitted into the groove 311, the circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43. Therefore, even if the magnetic body 43 is subjected to centrifugal force when the rotor 2D rotates, the magnetic body 43 is engaged in the groove 311, preventing the magnetic body 43 from scattering radially outward.

[0078] Furthermore, in the region of the magnetic body 43 that is fitted into the groove 421, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43, so that even if the auxiliary magnet 42 is subjected to centrifugal force when the rotor 2D rotates, the auxiliary magnet 42 is engaged with the magnetic body 43, preventing the auxiliary magnet 42 from scattering radially outward.

[0079] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2C according to the third modification can be used to describe the rotor 2D according to the fourth modification.

[0080] <<Modification 5>> Fig. 9 is a development view of a partial cross section of a rotor 2E according to Modification 5. Fig. 9 shows the rotor 2E developed linearly in the circumferential direction. In Fig. 9, the solid arrows drawn on the auxiliary magnets 42 indicate the magnetization direction of the auxiliary magnets 42. The rotor 2E according to Modification 5 differs from the rotor 2 according to the embodiment in the configuration of the auxiliary magnets 42. The following description will focus on the configuration of the rotor 2E according to Modification 5 that differs from the rotor 2 according to the embodiment. Note that the other configurations are the same as the rotor 2 according to the embodiment, and therefore description thereof will be omitted.

[0081] In a rotor 2E according to Modification 5, the auxiliary magnet 42 includes a plurality of segments 420a, 420b divided in the circumferential direction. In this example, the auxiliary magnet 42 includes a first segment 420a and a second segment 420b. The first segment 420a is disposed opposite the first main magnet 41a, and the second segment 420b is disposed opposite the second main magnet 41b. The auxiliary magnet 42 may include three or more segments.

[0082] The magnetization directions of the first and second segments 420a and 420b are inclined relative to the circumferential direction. Specifically, the magnetization direction of the first segment 420a is from the second main magnet 41b toward the first main magnet 41a, and is inclined relative to the circumferential direction so that it is more radially outward as it approaches the first main magnet 41a. The magnetization direction of the second segment 420b is from the second main magnet 41b toward the first main magnet 41a, and is inclined relative to the circumferential direction so that it is more radially inward as it approaches the first main magnet 41a.

[0083] Each of the first divided body 420a and the second divided body 420b has a groove 421. A magnetic body 43 is fitted into each of the grooves 421 of the first divided body 420a and the second divided body 420b.

[0084] According to the rotor 2E of the fifth modification, the auxiliary magnet 42 includes the divided bodies 420 a, 420 b, so that the magnetization direction of each divided body 420 a, 420 b can be set individually. This makes it easy to adjust the direction of the magnetic flux of the auxiliary magnet 42 that flows on the stator 6 side, and to easily strengthen the magnetic field on the stator 6 side.

[0085] Although the description of other configurations, actions, and effects will be omitted, the description of the rotor 2 according to the embodiment can be used to describe the rotor 2E according to the fifth modified example.

[0086] <<Modification 6>> Fig. 10 is a development view of a partial cross section of a rotor 2F according to Modification 6. Fig. 10 shows the rotor 2F developed linearly in the circumferential direction. In Fig. 10, the sleeve 5 is not omitted. The rotor 2F according to Modification 6 differs from the rotor 2E according to Modification 5 in the configuration of the magnetic body 43 and in the presence of a partition wall 45. The following description will focus on the configuration of the rotor 2F according to Modification 6 that differs from the rotor 2E according to Modification 5. Note that the other configurations are the same as those of the rotor 2E according to Modification 5, and therefore description thereof will be omitted.

[0087] In a rotor 2F according to the sixth modification, the magnetic body 43 is integrated with the rotor body 3. The magnetic body 43 is, for example, molded integrally with the rotor body 3.

[0088] The partition wall 45 is located between the divided bodies 420a and 420b of the auxiliary magnet 42. Specifically, the partition wall 45 is located between the first divided body 420a and the second divided body 420b.

[0089] The partition wall 45 extends in the direction of the rotation axis X. The partition wall 45 also extends radially outward from the outer peripheral surface of the rotor body 3. Specifically, the partition wall 45 extends from the outer peripheral surface of the rotor body 3 to the inner peripheral surface of the sleeve 5. The partition wall 45 contacts the inner peripheral surface of the sleeve 5.

[0090] The partition wall 45 is integrated with the rotor body 3. For example, the partition wall 45 is molded integrally with the rotor body 3.

[0091] According to the rotor 2F of variant example 6, the magnetic body 43 is arranged on the outer peripheral surface of the rotor main body 3 together with the main magnet 41 and the auxiliary magnet 42, and even if the magnetic body 43 is subjected to centrifugal force when the rotor 2F rotates, the magnetic body 43 is integrated with the rotor main body 3, so that the magnetic body 43 can be prevented from scattering radially outward.

[0092] Furthermore, since the only parts that may fly outward in the radial direction when the rotor 2F rotates are the main magnets 41 and the auxiliary magnets 42, the total weight of the parts that fly off is reduced. This reduces the centrifugal force acting on the sleeve 5 that surrounds the outer peripheries of the main magnets 41 and the auxiliary magnets 42.

[0093] Furthermore, since the magnetic body 43 is integrated with the rotor body 3, the number of parts can be reduced, and the manufacturability of the rotor 2F can be improved.

[0094] Furthermore, since the partition wall 45 is located between the divided bodies 420a, 420b, the partition wall 45 absorbs the gap between the circumferentially adjacent divided bodies 420a, 420b, and the partition wall 45 can reduce the circumferential rattle of the divided bodies 420a, 420b.

[0095] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2E according to the fifth modification can be used to describe the rotor 2F according to the sixth modification.

[0096] <<Modification 7>> Figure 11 is an enlarged cross-sectional view of a portion of a rotor 2G according to Modification 7. Figure 11 shows the rotor 2G expanded linearly in the circumferential direction. The rotor 2G according to Modification 7 differs from the rotor 2 according to the embodiment in the position of the magnetic body 43. The following description will focus on the configuration of the rotor 2G according to Modification 7 that differs from the rotor 2 according to the embodiment. Note that the other configurations are the same as the rotor 2 according to the embodiment, and therefore description thereof will be omitted.

[0097] In the rotor 2G according to the seventh modification, the magnetic bodies 43 are arranged at the second position L2 instead of the first position L1. All of the magnetic bodies 43 are arranged at the second position L2. The magnetic bodies 43 are arranged only at the second position L2. Specifically, two magnetic bodies 43 are arranged between one main magnet 41 and the rotor body 3. The two magnetic bodies 43 include one magnetic body 43 and the other magnetic body 43. While FIG. 11 shows the first main magnet 41a, the second main magnet 41b has a similar configuration.

[0098] One main magnet 41 is adjacent to an auxiliary magnet 42 on both the left and right sides in the circumferential direction. The auxiliary magnet 42 adjacent to the main magnet 41 on either the left or right side in the circumferential direction will be referred to below as one auxiliary magnet 42. The auxiliary magnet 42 adjacent to the main magnet 41 on the other left or right side in the circumferential direction will be referred to below as the other auxiliary magnet 42. In Figure 11, one auxiliary magnet 42 is the auxiliary magnet 42 on the left side of the main magnet 41, and the other auxiliary magnet 42 is the auxiliary magnet 42 on the right side of the main magnet 41.

[0099] One magnetic body 43 is disposed at a second position L2 between the main magnet 41 and the rotor body 3, in the one auxiliary magnet 42 and the main magnet 41 that are adjacent to each other in the circumferential direction, and closer to the one auxiliary magnet 42 with respect to the circumferential center C1 of the main magnet 41. The one magnetic body 43 faces the one auxiliary magnet 42. In FIG. 11 , the one magnetic body 43 is the magnetic body 43 on the left side of the main magnet 41.

[0100] The other magnetic body 43 is disposed at a second position L2 between the main magnet 41 and the rotor body 3, in the other auxiliary magnet 42 and the main magnet 41 that are adjacent to each other in the circumferential direction, and closer to the other auxiliary magnet 42 with respect to the circumferential center C1 of the main magnet 41. The other magnetic body 43 faces the other auxiliary magnet 42. In FIG. 11 , the other magnetic body 43 is the magnetic body 43 on the right side of the main magnet 41.

[0101] In this way, when one main magnet 41 is used as a reference, the auxiliary magnets 42 are adjacent to each other on the left and right sides of the reference main magnet 41 in the circumferential direction, and therefore the second positions L2 are located on the left and right sides of the reference main magnet 41 in the circumferential direction. In other words, the two second positions L2 are located at positions symmetrical in the circumferential direction with respect to the center C1 of the reference main magnet 41.

[0102] The main magnet 41 has a groove 411 provided on the surface of the main magnet 41 facing the rotor body 3. The groove 411 opens on the surface of the main magnet 41 facing the rotor body 3 and on the surface of the main magnet 41 facing the auxiliary magnet 42. The magnetic body 43 is fitted into the groove 411. In this way, the groove 411 corresponds to the second position L2.

[0103] Specifically, the main magnet 41 has two grooves 411. One of the two grooves 411 opens to the surface of the main magnet 41 facing the rotor body 3 and the surface of the main magnet 41 facing one of the auxiliary magnets 42. The other of the two grooves 411 opens to the surface of the main magnet 41 facing the rotor body 3 and the surface of the main magnet 41 facing the other auxiliary magnet 42. One magnetic body 43 is fitted into one groove 411. The other magnetic body 43 is fitted into the other groove 411. One magnetic body 43 contacts one of the auxiliary magnets 42 and the main magnet 41 and the rotor core 31 of the rotor body 3. The other magnetic body 43 contacts the other auxiliary magnet 42 and the main magnet 41 and the rotor core 31 of the rotor body 3.

[0104] The circumferential width of the radially outer portion of the groove 411 is narrower than the circumferential width of the radially inner portion of the groove 411. Specifically, the circumferential width of the groove 411 continuously narrows from the radially inner side to the radially outer side. In this example, the cross section of the groove 411 is triangular. One groove 411 and the other groove 411 have shapes that are circumferentially symmetrical with respect to the center C1 of the main magnet 41. Note that the circumferential width of the groove 411 may narrow stepwise from the radially inner side to the radially outer side, and the cross section of the groove 411 is not limited to a triangle.

[0105] The circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43. Specifically, the circumferential width of the magnetic body 43 continuously narrows from the radially inner side to the radially outer side. In this example, the cross section of the magnetic body 43 is triangular. One magnetic body 43 and the other magnetic body 43 have shapes that are circumferentially symmetrical with respect to the center C1 of the main magnet 41. Note that the circumferential width of the magnetic body 43 may narrow stepwise from the radially inner side to the radially outer side, and the cross section of the magnetic body 43 is not limited to a triangle.

[0106] According to the rotor 2G of the seventh modification, the magnetic body 43 is disposed at the second position L2, so similar to the rotor 2 according to the embodiment, on the rotor body 3 side of the plurality of main magnets 41 and the plurality of auxiliary magnets 42, some of the magnetic flux of the auxiliary magnets 42 can pass to the rotor body 3 via the magnetic body 43 without passing through the main magnets 41. This makes it possible to mitigate the magnetic flux of the auxiliary magnets 42 canceling out the magnetic flux of the main magnets 41 on the rotor body 3 side. Therefore, demagnetization of the main magnets 41 can be reduced.

[0107] Furthermore, because the magnetic body 43 is positioned at the second position L2, a groove 411 can be formed on the surface of the main magnet 41 facing the rotor body 3, and the magnetic body 43 can be attached to the groove 411. In this case, assuming that the volume of the main magnet 41 is fixed, the reduction in the volume of the main magnet 41 due to the formation of the groove 411 can be added to the volume of the central portion of the main magnet 41 so that the thickness of the central portion of the main magnet 41 increases. This allows the volume of the central portion of the main magnet 41, which contributes to the overall magnetic force of the main magnet 41, to be larger than the volume of the circumferential end portions of the main magnet 41, thereby improving the magnetic force of the main magnet 41. This improves the torque performance of the rotor 2G. Specifically, magnetic force is more concentrated in the central portion of the main magnet 41 than in the end portions of the main magnet 41. Therefore, by increasing the volume of the central portion where magnetic force is concentrated, the magnetic force of the main magnet 41 can be improved.

[0108] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2 according to the embodiment can be used to describe the rotor 2G according to the seventh modified example.

[0109] <<Modification 8>> Figure 12 is an enlarged cross-sectional view of a portion of a rotor 2H according to Modification 8. Figure 12 shows the rotor 2H expanded linearly in the circumferential direction. The rotor 2H according to Modification 8 differs from the rotor 2 according to the embodiment in the position of the magnetic body 43. The following description will focus on the configuration of the rotor 2H according to Modification 8 that differs from the rotor 2 according to the embodiment. Note that the other configurations are the same as the rotor 2 according to the embodiment, and therefore description thereof will be omitted.

[0110] In the rotor 2H according to Modification 8, the magnetic bodies 43 are arranged at both the first position L1 and the second position L2. The magnetic bodies 43 straddle the first position L1 and the second position L2. All of the magnetic bodies 43 are arranged at both the first position L1 and the second position L2. The magnetic bodies 43 are arranged only at both the first position L1 and the second position L2. Specifically, as described in the embodiment, the auxiliary magnet 42 has a groove 421, which corresponds to the first position L1. Also, as described in Modification 7, the main magnet 41 has a groove 411, which corresponds to the second position L2. The groove 411 and the groove 421 are connected to each other. Detailed descriptions of the groove 411 and the second position L2 have been given in Modification 7, and therefore will not be repeated here. Detailed descriptions of the groove 421 and the first position L1 have been given in the embodiment, and therefore will not be repeated here.

[0111] According to the rotor 2H of Modification 8, the magnetic body 43 is disposed at both the first position L1 and the second position L2, so similar to the rotor 2 according to the embodiment, on the rotor body 3 side with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42, some of the magnetic flux of the auxiliary magnets 42 can pass to the rotor body 3 via the magnetic body 43 without passing through the main magnets 41. This makes it possible to mitigate the magnetic flux of the auxiliary magnets 42 canceling out the magnetic flux of the main magnets 41 on the rotor body 3 side. Therefore, demagnetization of the main magnets 41 can be reduced.

[0112] Furthermore, since the magnetic body 43 is disposed at both the first position L1 and the second position L2, it is possible to increase the magnetic flux of the auxiliary magnet 42 passing through the magnetic body 43. This makes it possible to further mitigate the magnetic flux of the auxiliary magnet 42 canceling out the magnetic flux of the main magnet 41 on the rotor body 3 side. Therefore, it is possible to further reduce demagnetization of the main magnet 41.

[0113] The description of the other configurations, actions, and effects will be omitted, but the description of the rotor 2 according to the embodiment can be used to describe the rotor 2H according to the eighth modified example.

[0114] Next, an example will be described in which the rotor 2 of the embodiment, the rotor 2G of the seventh modification, and the rotor 2H of the eighth modification are each applied to a motor. In the rotor 2 of the embodiment, the magnetic body 43 is arranged at the first position L1. In the rotor 2G of the seventh modification, the magnetic body 43 is arranged at the second position L2. In the rotor 2H of the eighth modification, the magnetic body 43 is arranged at both the first position L1 and the second position L2.

[0115] 13 is a diagram showing analysis results of motor torque waveforms in examples where the rotor 2 of the embodiment, the rotor 2G of Modification 7, and the rotor 2H of Modification 8 are applied to motors. In FIG. 13, the horizontal axis represents time [s], and the vertical axis represents motor torque [p.u.]. The solid line N1 is a graph of the example where the rotor 2 is applied. The dashed-dotted line N2 is a graph of the example where the rotor 2G is applied. The dotted line N3 is a graph of the example where the rotor 2H is applied.

[0116] In each example, the same conditions were used for the stator shape, current conditions, etc., except for the position of the magnetic material 43. Specifically, a concentrated winding SPM motor was used. The rotor rotation speed was set to the rated rotation speed. For example, the rotation speed was set to 1000 rpm. The current flowing through the winding was set to the rated current. For example, the current was set to 100 Arms. The current phase β was set to β = 0° during torque analysis. The current phase β is defined as the phase difference between the current Ia on the d- and q-axes of the permanent magnet synchronous motor and the q-axis.

[0117] 13, it was confirmed that the torque indicated by the solid line N1 was the highest, the torque indicated by the dashed-dotted line N2 was the second highest, and the torque indicated by the dotted line N3 was the third highest. Thus, the torque was highest when the magnetic body 43 was located at the first position L1. The torque was next highest when the magnetic body 43 was located at the second position L2, and the torque was next highest when the magnetic body 43 was located at both the first position L1 and the second position L2.

[0118] Fig. 14 is a diagram showing the analysis results of the demagnetization factor of the main magnet 41 in an example in which the rotor 2 of the embodiment is applied to a motor. Fig. 15 is a diagram showing the analysis results of the demagnetization factor of the main magnet 41 in a comparative example in which a rotor without a magnetic body is applied to a motor. In Figs. 14 and 15, the demagnetization factor in the cross section of the main magnet 41 is shown by hatching. In Figs. 14 and 15, the upper side of the main magnet 41 indicates the radially outer side, and the lower side of the main magnet 41 indicates the radially inner side.

[0119] The demagnetization factor of the main magnet 41 was calculated as the difference between the magnetic force of the main magnet 41 after it was demagnetized and the magnetic force of the main magnet 41 before it was demagnetized. In Figures 14 and 15, the larger the demagnetization factor, i.e., the larger the difference, the denser the hatching on the cross section of the main magnet 41.

[0120] In the example and comparative example, the conditions such as the shape of the stator and the current conditions were the same, except for the presence or absence of a magnetic body. Specifically, a concentrated winding SPM motor was used. The rotor rotation speed was set to the rated rotation speed. For example, the rotation speed was set to 1000 rpm. The current flowing through the winding was set to the rated current. For example, the current was set to 100 Arms. The current phase β was set to β = 90° during the demagnetization analysis. The current phase β is defined as the phase difference between the current Ia on the d- and q-axes of the permanent magnet synchronous motor and the q-axis.

[0121] It was confirmed that the demagnetization factor of the main magnet 41 of the example shown in Figure 14 was smaller than that of the main magnet 41 of the comparative example shown in Figure 15. Specifically, the total area of ​​the regions with a large demagnetization factor of the main magnet 41 of the example was smaller than the total area of ​​the regions with a large demagnetization factor of the main magnet 41 of the comparative example. In this way, the demagnetization factor of the main magnet 41 was smaller when the magnetic body 43 was placed at the first position L1. Furthermore, the demagnetization factor of the main magnet 41 was larger when the magnetic body 43 was not provided.

[0122] Other Embodiments As described above, the above-described embodiments have been described as examples of the technology disclosed in the present application. However, the technology disclosed herein is not limited to these embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described embodiments can be combined to create new embodiments. Furthermore, the components described in the accompanying 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 exemplify the technology. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately determining that these non-essential components are essential.

[0123] For example, there is no limit to the number of the main magnets 41, the auxiliary magnets 42, and the magnetic bodies 43. Furthermore, the shaft 32 may be integrated with the rotor core 31.

[0124] Furthermore, the rotor 2 is an inner rotor, but may also be an outer rotor. That is, the rotor 2 is arranged radially outside the stator 6. In this case, the multiple main magnets 41 and the multiple auxiliary magnets 42 are arranged on the inner circumferential surface of the rotor body 3, which is the circumferential surface on the stator 6 side. In this case, the multiple main magnets 41 and the multiple auxiliary magnets 42 are magnetized so that the magnetic field radially inward relative to the multiple main magnets 41 and the multiple auxiliary magnets 42 is stronger than the magnetic field radially outward relative to the multiple main magnets 41 and the multiple auxiliary magnets 42.

[0125] Furthermore, although the rotor 2 has a sleeve 5, the rotor 2 does not necessarily have to have a sleeve 5. In this case, the plurality of main magnets 41 and the plurality of auxiliary magnets 42 may be fixed to the rotor body 3 by adhesive or the like.

[0126] In addition, the rotor 2 may combine at least two magnetic bodies 43 from among a magnetic body 43 arranged at the first position L1, a magnetic body 43 arranged at the second position L2, and a magnetic body 43 arranged across the first position L1 and the second position L2.

[0127] Furthermore, the magnetization direction of the auxiliary magnet 42 is the circumferential direction, but it may be a direction inclined relative to the circumferential direction, or may be any direction different from the radial direction.

[0128] In the embodiment, at least one of the components described in each of the first to sixth modifications may be combined.

[0129] In the seventh modification, at least one of the components described in each of the first to sixth modifications may be combined.

[0130] In the eighth modification, at least one of the components described in each of the first to sixth modifications may be combined.

[0131] [Aspects] The above-described embodiments are specific examples of the following aspects.

[0132] (Aspect 1) Each of the rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H includes a rotor body 3 that rotates around a rotation axis X, a plurality of main magnets 41 and a plurality of auxiliary magnets 42 that are alternately arranged on a peripheral surface of the rotor body 3 along a circumferential direction centered on the rotation axis X, and a first position L1 between the auxiliary magnet 42 and the rotor body 3 and closer to the main magnet 41 with respect to a circumferential center C2 of the auxiliary magnet 42, or a second position L2 between the main magnet 41 and the rotor body 3 and closer to the main magnet 41 with respect to a circumferential center C2 of the auxiliary magnet 42. and a magnetic body 43 arranged at least at one of second positions L2 located closer to the auxiliary magnet 42 with respect to the circumferential center C1 of the rotor 1, wherein each of the plurality of main magnets 41 is magnetized in a radial direction centered on the rotation axis X, and each of the plurality of auxiliary magnets 42 is magnetized in a direction different from the radial direction, and the plurality of main magnets 41 and the plurality of auxiliary magnets 42 are arranged in a Halbach array such that the magnetic field on the side opposite to the rotor body 3 with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42 is stronger than the magnetic field on the rotor body 3 side with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42.

[0133] According to this configuration, the magnetic body 43 is disposed at least at the first position L1 or the second position L2, that is, the magnetic body 43 is disposed at both or either of the first position L1 and the second position L2, so that, on the rotor body 3 side with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42, some of the magnetic flux of the auxiliary magnets 42 can pass to the rotor body 3 via the magnetic body 43 without passing through the main magnets 41. This makes it possible to mitigate the magnetic flux of the auxiliary magnets 42 canceling out the magnetic flux of the main magnets 41 on the rotor body 3 side. Therefore, demagnetization of the main magnets 41 can be reduced.

[0134] (Aspect 2) In the rotor 2H according to aspect 1, the magnetic bodies 43 are disposed at both the first position L1 and the second position L2.

[0135] With this configuration, the magnetic body 43 is disposed at both the first position L1 and the second position L2, which increases the magnetic flux of the auxiliary magnet 42 passing through the magnetic body 43. This further reduces the magnetic flux of the auxiliary magnet 42 from canceling out the magnetic flux of the main magnet 41 on the rotor body 3 side. Therefore, demagnetization of the main magnet 41 can be further reduced.

[0136] (Aspect 3) In the rotor 2, 2A, 2B, 2C, 2D, 2G according to aspect 1 or aspect 2, the magnetic body 43 is disposed at either the first position L1 or the second position L2.

[0137] According to this configuration, when the magnetic body 43 is disposed at either the first position L1 or the second position L2, a groove can be formed, for example, on the surface of the auxiliary magnet 42 facing the rotor body 3 or on the surface of the main magnet 41 facing the rotor body 3, and the magnetic body 43 can be attached to the groove. In this case, it is sufficient to form the groove in either the auxiliary magnet 42 or the main magnet 41, thereby reducing the effort required to form the groove.

[0138] (Aspect 4) In the rotor 2G according to any one of Aspects 1 to 3, the magnetic body 43 is disposed at the second position L2.

[0139] With this configuration, when the magnetic body 43 is disposed at the second position L2, for example, a groove can be formed on the surface of the main magnet 41 facing the rotor body 3, and the magnetic body 43 can be attached to the groove. In this case, assuming that the volume of the main magnet 41 is fixed, the reduction in the volume of the main magnet 41 due to the formation of the groove can be added to the volume of the central portion of the main magnet 41 so that the thickness of the central portion of the main magnet 41 in the circumferential direction increases. This makes it possible to make the volume of the central portion of the main magnet 41, which contributes to the overall magnetic force of the main magnet 41, larger than the volume of the circumferential end portions of the main magnet 41, thereby improving the magnetic force of the main magnet 41. This improves the torque performance of the rotor 2G.

[0140] (Aspect 5) In the rotor 2, 2A, 2B, 2C, 2D according to any one of Aspects 1 to 4, the magnetic body 43 is disposed at the first position L1.

[0141] With this configuration, when the magnetic body 43 is disposed at the first position L1, for example, a groove can be formed on the surface of the auxiliary magnet 42 that faces the rotor body 3, and the magnetic body 43 can be attached to the groove. In this case, it is not necessary to form a groove on the surface of the main magnet 41 that faces the rotor body 3, and a reduction in the volume of the main magnet 41 can be suppressed. This improves the torque performance of the rotors 2, 2A, 2B, 2C, and 2D.

[0142] (Aspect 6) In the rotor 2A according to any one of Aspects 1 to 5, the magnetic body 43 is integrated with the rotor body 3.

[0143] According to this configuration, when the magnetic body 43 is arranged on the outer peripheral surface of the rotor body 3 together with the main magnet 41 and the auxiliary magnet 42, even if the magnetic body 43 is subjected to centrifugal force when the rotor 2A rotates, the magnetic body 43 is integrated with the rotor body 3, and therefore the magnetic body 43 can be prevented from scattering radially outward.

[0144] (Aspect 7) In the rotor 2B described in any one of Aspects 1 to 6, the plurality of main magnets 41 and the plurality of auxiliary magnets 42 are arranged on the outer peripheral surface of the rotor body 3, the auxiliary magnets 42 have grooves 421 provided on the surface of the auxiliary magnet 42 facing the rotor body 3, the magnetic body 43 is fitted into the grooves 421, and the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43.

[0145] According to this configuration, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43, so that even if the auxiliary magnet 42 is subjected to centrifugal force when the rotor 2B rotates, the auxiliary magnet 42 can be prevented from scattering radially outward.

[0146] (Mode 8) In rotors 2C, 2D described in any one of modes 1 to 7, the auxiliary magnet 42 has a first groove 421 provided on the surface of the auxiliary magnet 42 facing the rotor main body 3, the rotor main body 3 has a second groove 311 provided on the surface of the rotor main body 3 facing the auxiliary magnet 42 and facing the first groove 421, and the magnetic body 43 is fitted into the first groove 421 and the second groove 311.

[0147] With this configuration, the magnetic body 43 is fitted into the first groove 421 and the second groove 311, which increases the contact area of ​​the magnetic body 43 with the auxiliary magnet 42 and the rotor body 3. This increases the magnetic flux of the auxiliary magnet 42 passing through the magnetic body 43 and the rotor body 3 on the rotor body 3 side, and further reduces the magnetic flux of the auxiliary magnet 42 from canceling out the magnetic flux of the main magnet 41 on the rotor body 3 side. Therefore, demagnetization of the main magnet 41 can be further reduced.

[0148] (Aspect 9) In the rotor 2D described in any one of aspects 1 to 8, the multiple main magnets 41 and the multiple auxiliary magnets 42 are arranged on the outer peripheral surface of the rotor body 3, and in the region of the magnetic body 43 that is fitted into the first groove 421, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43, and in the region of the magnetic body 43 that is fitted into the second groove 311, the circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43.

[0149] According to this configuration, in the region of the magnetic body 43 that is fitted into the second groove 311, the circumferential width of the radially outer portion of the magnetic body 43 is narrower than the circumferential width of the radially inner portion of the magnetic body 43, so that even if the magnetic body 43 is subjected to centrifugal force when the rotor 2D rotates, the magnetic body 43 can be prevented from scattering radially outward.

[0150] Furthermore, in the region of the magnetic body 43 that is fitted into the first groove 421, the circumferential width of the radially outer portion of the magnetic body 43 is wider than the circumferential width of the radially inner portion of the magnetic body 43, so that even if the auxiliary magnet 42 is subjected to centrifugal force when the rotor 2D rotates, the auxiliary magnet 42 can be prevented from scattering radially outward.

[0151] (Aspect 10) A motor 100 includes rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H that rotate around a rotation axis X, and a stator 6 that faces the rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H and rotates the rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H around the rotation axis X, and the rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H include a rotor body 3, a plurality of main magnets 41 and a plurality of auxiliary magnets 42 that are alternately arranged along a circumferential direction about the rotation axis X on a peripheral surface of the rotor body 3 that faces the stator 6, and a plurality of main magnets 41 and a plurality of auxiliary magnets 42 that are adjacent to each other in the circumferential direction, between the auxiliary magnet 42 and the rotor body 3, and a magnetic body 43 arranged at least in one of a first position L1 located closer to the main magnet 41 with respect to the circumferential center C2 of the auxiliary magnet 42, or a second position L2 located between the main magnet 41 and the rotor body 3 and closer to the auxiliary magnet 42 with respect to the circumferential center C1 of the main magnet 41, wherein each of the plurality of main magnets 41 is magnetized in a radial direction centered on the rotation axis X, and each of the plurality of auxiliary magnets 42 is magnetized in a direction different from the radial direction, and the plurality of main magnets 41 and the plurality of auxiliary magnets 42 are arranged in a Halbach array such that the magnetic field on the stator 6 side with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42 is stronger than the magnetic field on the rotor body 3 side with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42.

[0152] With this configuration, the magnetic body 43 is disposed at least at the first position L1 or the second position L2, so that, on the rotor body 3 side, with respect to the plurality of main magnets 41 and the plurality of auxiliary magnets 42, some of the magnetic flux of the auxiliary magnets 42 can pass to the rotor body 3 via the magnetic body 43 without passing through the main magnets 41. This reduces the possibility that the magnetic flux of the auxiliary magnets 42 will cancel out the magnetic flux of the main magnets 41 on the rotor body 3 side. Therefore, demagnetization of the main magnets 41 can be reduced. Furthermore, reducing the demagnetization of the main magnets 41 improves the torque performance of the rotors 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H, thereby improving the performance of the motor 100.

[0153] 100 Motor 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H Rotor 3 Rotor body 311 Groove (second groove) 41 Main magnet 42 Auxiliary magnet 421 Groove (first groove) 43 Magnetic body 6 Stator C1 Circumferential center of main magnet C2 Circumferential center of auxiliary magnet L1 First position L2 Second position X Rotation axis

Claims

1. A rotor comprising: a rotor body that rotates around a rotation axis; a plurality of main magnets and a plurality of auxiliary magnets that are alternately arranged on the peripheral surface of the rotor body along a circumferential direction centered on the rotation axis; and magnetic bodies that are arranged in at least one of a first position between the auxiliary magnet and the rotor body and closer to the main magnet with respect to the circumferential center of the auxiliary magnet, and a second position between the main magnet and the rotor body and closer to the auxiliary magnet with respect to the circumferential center of the main magnet, wherein each of the plurality of main magnets is magnetized in a radial direction centered on the rotation axis, and each of the plurality of auxiliary magnets is magnetized in a direction different from the radial direction, and the plurality of main magnets and the plurality of auxiliary magnets are arranged in a Halbach array so that the magnetic field on the side opposite the rotor body with respect to the plurality of main magnets and the plurality of auxiliary magnets is stronger than the magnetic field on the rotor body side with respect to the plurality of main magnets and the plurality of auxiliary magnets.

2. A rotor according to claim 1, wherein the magnetic body is disposed at both the first position and the second position.

3. A rotor according to claim 1, wherein the magnetic body is disposed at either the first position or the second position.

4. A rotor according to claim 3, wherein the magnetic body is disposed at the second position.

5. A rotor according to claim 3, wherein the magnetic body is disposed at the first position.

6. A rotor according to claim 5, wherein the magnetic body is integrated into the rotor body.

7. A rotor as described in claim 6, wherein the plurality of main magnets and the plurality of auxiliary magnets are arranged on the outer peripheral surface of the rotor body, the auxiliary magnets have grooves provided on the surfaces of the auxiliary magnets facing the rotor body, the magnetic body is fitted into the grooves, and the circumferential width of the radially outer portion of the magnetic body is wider than the circumferential width of the radially inner portion of the magnetic body.

8. A rotor as described in claim 5, wherein the auxiliary magnet has a first groove provided on a surface of the auxiliary magnet facing the rotor body, the rotor body has a second groove provided on a surface of the rotor body facing the auxiliary magnet and facing the first groove, and the magnetic body is fitted into the first groove and the second groove.

9. A rotor as described in claim 8, wherein the plurality of main magnets and the plurality of auxiliary magnets are arranged on the outer peripheral surface of the rotor body, and in the region of the magnetic body that is fitted into the first groove, the circumferential width of the radially outer portion of the magnetic body is wider than the circumferential width of the radially inner portion of the magnetic body, and in the region of the magnetic body that is fitted into the second groove, the circumferential width of the radially outer portion of the magnetic body is narrower than the circumferential width of the radially inner portion of the magnetic body.

10. A rotor that rotates around a rotation axis, and a stator that faces the rotor and rotates the rotor around the rotation axis, the rotor comprising: a rotor body; a plurality of main magnets and a plurality of auxiliary magnets that are alternately arranged along a circumferential direction centered on the rotation axis on the peripheral surface of the rotor body facing the stator; and a magnetic body that is arranged in at least one of a first position between the auxiliary magnet and the rotor body and located closer to the main magnet with respect to the circumferential center of the auxiliary magnet, and a second position between the main magnet and the rotor body and located closer to the auxiliary magnet with respect to the circumferential center of the main magnet, each of the plurality of main magnets being magnetized in a radial direction centered on the rotation axis, and each of the plurality of auxiliary magnets being magnetized in a direction different from the radial direction, The motor in which the plurality of main magnets and the plurality of auxiliary magnets are arranged in a Halbach array such that the magnetic field on the stator side relative to the plurality of main magnets and the plurality of auxiliary magnets is stronger than the magnetic field on the rotor body side relative to the plurality of main magnets and the plurality of auxiliary magnets.

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