Rotor

Abstract

A rotor (10) comprises a rotor core (12) and a magnet (14) embedded in the rotor core. The rotor core has an accommodation hole (18) positioned closer to the outer circumferential surface (12A) side of the rotor core than the central portion of the rotor core. The magnet is accommodated in the accommodation hole. A foamable resin (20) having foaming properties is filled between the magnet and the inner surface of the accommodation hole. A clearance groove (22) recessed toward the outer circumferential surface side is formed on an outer side surface (18A) of the inner surface positioned on the outer circumferential surface side.

Description

rotor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-080161 filed on May 16, 2024 and Japanese Patent Application No. 2024-081775 filed on May 20, 2024, the entire contents of which are incorporated herein by reference.

[0002] The technology of the present disclosure relates to a rotor, and more particularly to an embedded magnet rotor.

[0003] In the technical field of embedded magnet rotors, embedded magnet rotors having a rotor core and a magnet embedded in the rotor core are known (see, for example, JP 2023-027913 A, JP 2021-197880 A, JP 2018-57256 A, and JP 2016-537950 A). In these rotors, the rotor core has an accommodating hole located closer to the outer circumferential surface of the rotor core than the center of the rotor core, and the magnet is accommodated in the accommodating hole.

[0004] In addition, the rotor described in JP 2021-197880 A uses a leaf spring to move the magnet closer to the outer circumferential surface of the rotor core. The reason for arranging the magnet closer to the outer circumferential surface of the rotor core is to improve the performance of the brushless motor by bringing the magnet closer to the stator located radially outside the rotor.

[0005] As a result of detailed investigations by the inventors, the following problem was found: If a leaf spring is used to move the magnet closer to the outer peripheral surface of the rotor core, there is a risk that the cost will increase due to the leaf spring.

[0006] Furthermore, when the rotor rotates, centrifugal force acts on the magnet. Therefore, in order to hold the magnet, it is conceivable to ensure a sufficient thickness for the portion of the rotor core radially outside the accommodating hole to ensure a holding force for the magnet. However, in this case, the distance between the outer circumferential surface of the rotor core and the magnet becomes longer, which in turn increases the distance between the stator disposed radially outside the rotor and the magnet, which may result in a decrease in the performance of the brushless motor. Therefore, there is room for improvement in preventing the distance between the outer circumferential surface of the rotor core and the magnet from becoming longer.

[0007] In addition, in a rotor in which a thin-walled outer bridge portion with its thickness aligned with the radial direction of the rotor core is formed between the circumferential ends of the rotor core and the outer peripheral surface of the rotor core, when the rotor rotates and centrifugal force acts on the magnet, stress concentrates on the outer bridge portion. Increasing the thickness of the outer bridge portion is considered to ensure a sufficient holding force for the magnet. However, this increases the leakage flux of the magnet passing through the outer bridge portion, which may degrade the performance of the brushless motor or increase torque ripple. Therefore, there is room for improvement in suppressing stress concentration on the outer bridge portion.

[0008] A first aspect of the technology of the present disclosure is to provide a rotor that allows magnets to be disposed closer to the outer peripheral surface of the rotor core at lower cost than when using leaf springs.

[0009] A second aspect of the technology of the present disclosure is to provide a rotor that can prevent the distance between the outer peripheral surface of the rotor core and the magnet from becoming long.

[0010] In a third aspect, the technique of the present disclosure provides a rotor that can suppress stress concentration on the outer circumferential bridge portion.

[0011] A first aspect of the technology disclosed herein is a rotor comprising a rotor core and a magnet embedded in the rotor core, wherein the rotor core has an accommodating hole located closer to the outer circumferential surface of the rotor core than the center of the rotor core, the magnet is accommodated in the accommodating hole, a foamable resin having foaming properties is filled between the inner surface of the accommodating hole and the magnet, and an escape groove recessed toward the outer circumferential surface is formed on the outer surface of the inner surface located closer to the outer circumferential surface.

[0012] A second aspect of the technology of the present disclosure is a rotor comprising a rotor core and a magnet embedded in the rotor core, wherein the rotor core has an accommodating hole located closer to the outer surface of the rotor core than the center of the rotor core, and the magnet is accommodated in the accommodating hole and held from the outer surface of the rotor core by a holding member separate from the rotor core.

[0013] A third aspect of the technology disclosed herein is a rotor comprising a rotor core and a magnet embedded in the rotor core, wherein the magnet has an outer surface facing radially outward from the rotor core, the outer surface having a first circumferential end located on one circumferential side of the rotor core and a second circumferential end located on the other circumferential side of the rotor core, wherein a first line is a line extending from the center of the rotational axis of the rotor core through the first circumferential end to the radially outward side of the rotor core, and a second line is a line extending from the center of the rotational axis of the rotor core through the second circumferential end to the radially outward side of the rotor core, and a limiting portion is provided in the range between the first line and the second line when viewed in the axial direction of the rotor core to limit the expansion of the magnet radially outward from the rotor core.

[0014] According to the technology of the present disclosure, a rotor is provided in which magnets can be arranged closer to the outer peripheral surface of the rotor core at a lower cost than when using leaf springs.

[0015] According to the technique of the present disclosure, a rotor is provided that can prevent the distance between the outer peripheral surface of the rotor core and the magnet from becoming long.

[0016] According to the technique of the present disclosure, a rotor is provided that can suppress stress concentration on the outer circumferential bridge portion.

[0017] 5 is a plan view of a rotor according to a first embodiment of the technology of the present disclosure. FIG. 6 is a plan view of a rotor core enlarging part A of FIG. 1. FIG. 7 is a plan view of a rotor enlarging part A of FIG. 1. FIG. 8 is an exploded perspective view of a rotor according to a second embodiment of the technology of the present disclosure. FIG. 9 is a plan view of a rotor (a view in which a connecting member is omitted). FIG. 10 is a plan view of a rotor core enlarging part A of FIG. 1. FIG. 11 is a plan view of a rotor enlarging part A of FIG. 5 (a view in which a connecting member is omitted). FIG. 12 is an exploded perspective view of a rotor according to a third embodiment of the technology of the present disclosure. FIG. 13 is an enlarged plan view of a main part of a rotor according to the third embodiment of the technology of the present disclosure. FIG. 14 is a longitudinal cross-sectional view of a rotor according to the third embodiment of the technology of the present disclosure. FIG. 15 is a diagram showing a range between a first line and a second line in an axial view of a rotor core according to the third embodiment of the technology of the present disclosure. FIG. 16 is an enlarged exploded perspective view of a main part of a rotor according to the third embodiment of the technology of the present disclosure. FIG. 17 is an enlarged longitudinal cross-sectional view of a main part of a rotor according to the third embodiment of the technology of the present disclosure. FIG. 18 is a diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure. A diagram showing a modified example of a rotor according to the third embodiment of the technology of the present disclosure.

[0018] First Embodiment A first embodiment of the technology of the present disclosure will be described below.

[0019] The rotor 10 according to the first embodiment shown in Fig. 1 is an interior permanent magnet (IPM) rotor used in an inner rotor brushless motor. The rotor 10 includes a rotor core 12 and a plurality of magnets 14. The magnets 14 are embedded in the rotor core 12.

[0020] The rotor core 12 is a laminated body formed by stacking a plurality of core sheets in the axial direction of the rotor core 12. An outer peripheral surface 12A of the rotor core 12 is formed in a circular shape when viewed from the axial direction of the rotor core 12.

[0021] The rotor core 12 has an insertion hole 16 and a plurality of accommodating holes 18. The insertion hole 16 and the plurality of accommodating holes 18 penetrate the rotor core 12 in the axial direction. A shaft is inserted into the insertion hole 16. The insertion hole 16 is formed in the center of the rotor core 12.

[0022] The multiple accommodating holes 18 are aligned in the circumferential direction of the rotor core 12 along the outer peripheral surface 12A of the rotor core 12. Each accommodating hole 18 is located closer to the outer peripheral surface 12A than the center of the rotor core 12. As will be described later, arranging the magnets 14 accommodated in the accommodating holes 18 closer to the stator, which is located radially outward of the rotor 10, improves the performance of the brushless motor, so the accommodating holes 18 are formed in positions closer to the outer peripheral surface 12A of the rotor core 12.

[0023] Each magnet 14 is housed in a housing hole 18. The magnets 14 are formed in a flat plate shape and extend in a width direction that is tangent to the rotor core 12. Half of each magnet 14 on the outer peripheral surface 12A side is formed by one of the north and south magnetic poles (e.g., north pole), and the other half of each magnet 14 opposite the outer peripheral surface 12A is formed by the other of the north and south magnetic poles (e.g., south pole). The magnetic pole of the other half of each magnet 14 on the outer peripheral surface 12A side (e.g., north pole) of one of the adjacent magnets 14 is set to a different magnetic pole from the magnetic pole of the other half of the adjacent magnet 14 on the outer peripheral surface 12A side (e.g., south pole).

[0024] The gap between the inner surface of each accommodating hole 18 and the magnet 14 is filled with foamable resin 20. The foamable resin 20 is a resin that has foaming properties. The foamable resin 20 is injected between the inner surface of each accommodating hole 18 and the magnet 14 before foaming, and then foams after being injected, filling the gap between the inner surface of each accommodating hole 18 and the magnet 14. Each magnet 14 is fixed to the inner surface of the accommodating hole 18 via the foamable resin 20.

[0025] 2, the inner surface of the accommodating hole 18 more specifically has an outer surface 18A, an inner surface 18B, and a pair of lateral surfaces 18C. The outer surface 18A is the surface of the inner surface of the accommodating hole 18 that is located on the outer peripheral surface 12A side, the inner surface 18B is the surface of the inner surface of the accommodating hole 18 that is located on the opposite side from the outer peripheral surface 12A (i.e., on the central side of the rotor core 12), and the pair of lateral surfaces 18C are surfaces that are located on both sides of the accommodating hole 18 in the lateral width direction.

[0026] A pair of relief grooves 22 are formed in the outer surface 18A. Each relief groove 22 is formed in a concave shape recessed toward the outer peripheral surface 12A. Each relief groove 22 is formed at each end on both sides of the outer surface 18A in the width direction of the accommodation hole 18.

[0027] As shown in FIG. 3 , both ends of the outer surface 18A in the width direction of the accommodating hole 18 correspond to the portions of the outer surface 18A that correspond to the ends 14A of the magnets 14 in the width direction. That is, each relief groove 22 is formed in a portion of the outer surface 18A that corresponds to the ends 14A of the magnets 14 in the width direction. Each relief groove 22 serves to allow the foamable resin 20 filled between the inner surface of the accommodating hole 18 and the magnets 14 (particularly between the outer surface 18A and the magnets 14) to escape toward the outer peripheral surface 12A of the rotor core 12. For this reason, the magnets 14 are positioned closer to the outer peripheral surface 12A of the rotor core 12, and a gap 24 between the outer surface 18A and the magnets 14 is smaller than a gap 26 between the inner surface 18B and the magnets 14.

[0028] The magnet 14 is positioned closer to the outer peripheral surface 12A of the rotor core 12 in order to improve the performance of the brushless motor by bringing the magnet 14 closer to the stator, which is positioned radially outside the rotor 10.

[0029] A pair of recesses 28 are formed in the inner surface 18B. Each recess 28 is formed in a concave shape recessed on the opposite side from the outer peripheral surface 12A. Each recess 28 is formed at each end of the inner surface 18B in the width direction of the accommodating hole 18. The ends of the inner surface 18B in the width direction of the accommodating hole 18 correspond to the portions of the inner surface 18B corresponding to the ends 14A of the magnet 14 in the width direction. In other words, each recess 28 is formed in a portion of the inner surface 18B corresponding to the ends 14A of the magnet 14 in the width direction. The recesses 28 are formed to prevent the ends 14A of the magnet 14 in the width direction (especially the corners) from interfering with the inner surface 18B.

[0030] Furthermore, a flux barrier 30 is formed on each lateral side surface 18C. Each flux barrier 30 is formed in a concave shape that is recessed on the side away from the magnet 14 along the circumferential direction of the rotor core 12. The flux barrier 30 is a groove that ensures a gap that prevents magnetic flux from passing from the north pole to the south pole of the magnet 14.

[0031] Next, the effects of the first embodiment will be described.

[0032] As described above in detail, in the rotor 10 according to the first embodiment, the space between the inner surface of the accommodating hole 18 and the magnet 14 is filled with foamable resin 20, and the outer surface 18A of the inner surface of the accommodating hole 18, which is located on the outer peripheral surface 12A side of the rotor core 12, is formed with an escape groove 22 recessed toward the outer peripheral surface 12A. Therefore, the foamable resin 20 filled between the inner surface of the accommodating hole 18 and the magnet 14 (particularly between the outer surface 18A and the magnet 14) can escape to the outer peripheral surface 12A side of the rotor core 12. This allows the magnet 14 to be positioned closer to the outer peripheral surface 12A of the rotor core 12.

[0033] Here, it is possible to consider using a leaf spring to position the magnet 14 closer to the outer peripheral surface 12A of the rotor core 12, but if a leaf spring is used, processing etc. is required to mold the leaf spring into a predetermined shape, making it more expensive than the foamable resin 20.

[0034] In this regard, in the rotor 10 according to the first embodiment, a foamable resin 20 is used to position the magnet 14 close to the outer peripheral surface 12A of the rotor core 12, so no processing is required to mold it into a predetermined shape, and the magnet 14 can be positioned close to the outer peripheral surface 12A of the rotor core 12 at a lower cost than when a leaf spring is used.

[0035] Furthermore, magnet 14 extends with the tangential direction of rotor core 12 as its width direction, and relief groove 22 is formed in a portion of outer surface 18A that corresponds to end 14A in the width direction of magnet 14. Therefore, relief groove 22 is disposed between outer peripheral surface 12A of rotor core 12 and end 14A in the width direction of magnet 14, and relief groove 22 can be used as a configuration for suppressing leakage of magnetic flux from the north pole to the south pole of magnet 14.

[0036] Furthermore, because the magnet 14 is disposed closer to the outer peripheral surface 12A of the rotor core 12, the gap 24 between the outer surface 18A of the accommodating hole 18 and the magnet 14 is smaller than the gap 26 between the inner surface 18B of the accommodating hole 18 and the magnet 14. This allows the magnet 14 to be closer to the stator, which is disposed radially outward of the rotor 10, thereby improving the performance of the brushless motor.

[0037] In the above embodiment, a pair of relief grooves 22 are formed on the outer surface 18A, but the number of relief grooves 22 may be one, or three or more. Furthermore, the relief grooves 22 may be formed at locations on the outer surface 18A other than those described above.

[0038] Second Embodiment Next, a second embodiment of the technique of the present disclosure will be described.

[0039] A rotor 110 according to a second embodiment shown in Figures 4 and 5 is an interior permanent magnet (IPM) rotor used in an inner rotor brushless motor. The rotor 110 includes a rotor core 112, a plurality of magnets 114, and a holder 130. The plurality of magnets 114 are embedded in the rotor core 112.

[0040] The rotor core 112 is a laminated body formed by stacking a plurality of core sheets in the axial direction of the rotor core 112. An outer peripheral surface 112A of the rotor core 112 is formed in a circular shape when viewed from the axial direction of the rotor core 112.

[0041] The rotor core 112 has an insertion hole 116 and a plurality of accommodating holes 118. The insertion hole 116 and the plurality of accommodating holes 118 penetrate the rotor core 112 in the axial direction. A shaft is inserted into the insertion hole 116. The insertion hole 116 is formed in the center of the rotor core 112.

[0042] The multiple accommodating holes 118 are aligned in the circumferential direction of the rotor core 112 along the outer peripheral surface 112A of the rotor core 112. Each accommodating hole 118 is located closer to the outer peripheral surface 112A than the center of the rotor core 112. As will be described later, if the magnets 114 accommodated in the accommodating holes 118 are positioned closer to the stator, which is positioned radially outward of the rotor 110, the performance of the brushless motor improves. Therefore, the accommodating holes 118 are formed in positions closer to the outer peripheral surface 112A of the rotor core 112.

[0043] Each magnet 114 is housed in a housing hole 118. The magnets 114 are formed in a flat plate shape and extend in a width direction that is tangent to the rotor core 112. Half of the magnet 114 on the outer circumferential surface 112A side is formed by one of the north and south magnetic poles (e.g., north pole), and the half of the magnet 114 opposite the outer circumferential surface 112A is formed by the other of the north and south magnetic poles (e.g., south pole). The magnetic pole (e.g., north pole) of the half of the outer circumferential surface 112A side of one of the adjacent magnets 114 is set to a different magnetic pole from the magnetic pole (e.g., south pole) of the half of the outer circumferential surface 112A side of the other adjacent magnet 114.

[0044] 6 and 7 , the inner surface of the accommodating hole 118 more specifically has an outer surface 118A, an inner surface 118B, and a pair of lateral surfaces 118C. The outer surface 118A is the surface of the inner surface of the accommodating hole 118 that is located on the outer circumferential surface 112A side, the inner surface 118B is the surface of the inner surface of the accommodating hole 118 that is located on the opposite side from the outer circumferential surface 112A (i.e., on the central side of the rotor core 112), and the pair of lateral surfaces 118C are surfaces that are located on both sides of the accommodating hole 118 in the lateral width direction.

[0045] A pair of first recesses 120 are formed in the outer surface 118A. Each first recess 120 is formed in a concave shape recessed toward the outer peripheral surface 112A. Each first recess 120 is formed at each end on either side of the outer surface 118A in the width direction of the accommodating hole 118. The ends on either side of the outer surface 118A in the width direction of the accommodating hole 118 correspond to the portions of the outer surface 118A that correspond to the ends 114A of the magnet 114 in the width direction. In other words, each first recess 120 is formed in a portion of the inner surface 118B that corresponds to the ends 114A of the magnet 114 in the width direction.

[0046] A pair of second recesses 122 are formed in the inner surface 118B. Each second recess 122 is formed in a concave shape recessed on the opposite side from the outer peripheral surface 112A. Each second recess 122 is formed at each end of the inner surface 118B in the width direction of the accommodating hole 118. The ends of the inner surface 118B in the width direction of the accommodating hole 118 correspond to the portions of the inner surface 118B corresponding to the ends 114A of the magnet 114 in the width direction. In other words, each second recess 122 is formed in a portion of the inner surface 118B corresponding to the ends 114A of the magnet 114 in the width direction. The second recesses 122 are formed to prevent the ends 114A (particularly corners) of the magnet 114 in the width direction from interfering with the inner surface 118B.

[0047] A flux barrier 124 is formed on each lateral side surface 118C. Each flux barrier 124 is formed in a concave shape that is recessed on the side away from the magnet 114 along the circumferential direction of the rotor core 112. The flux barrier 124 is a groove that ensures a gap that prevents magnetic flux from passing from the north pole to the south pole of the magnet 114.

[0048] The holder 130 (see FIG. 4 ) is a separate member from the rotor core 112. The holder 130 is formed of a non-magnetic material such as aluminum or stainless steel. The holder 130 has a plurality of holding members 132 and a connecting member 134. Each holding member 132 is inserted into the first recess 120 (see FIG. 7 ). Each holding member 132 holds the magnet 114 from the outer peripheral surface 112A side of the rotor core 112. That is, each holding member 132 restrains the magnet 114 from the outer peripheral surface 112A side of the rotor core 112. A pair of holding members 132 is provided for each magnet 114, and the pair of holding members 132 hold both end portions 114A of the magnet 114 in the width direction.

[0049] The connecting member 134 is formed in an annular shape. As an example, the connecting member 134 is formed in a circular annular shape. Each of the accommodating holes 118 is open in the axial direction of the rotor core 112, and the connecting member 134 closes each of the accommodating holes 118.

[0050] Next, the effects of the second embodiment will be described.

[0051] As described above in detail, in the rotor 110 according to the second embodiment, the magnet 114 is held from the outer peripheral surface 112A side of the rotor core 112 by a holding member 132 separate from the rotor core 112. Therefore, a holding force for the magnet 114 can be ensured, and it is not necessary to ensure a thickness for the portion outside the accommodating hole 118, compared to when the holding member 132 is not provided. This makes it possible to prevent the distance between the outer peripheral surface 112A of the rotor core 112 and the magnet 114 from becoming too long, and allows the magnet 114 to be closer to the stator disposed radially outward of the rotor 110, thereby improving the performance of the brushless motor.

[0052] Furthermore, by reducing the thickness of the portion outside accommodation hole 118, it is possible to reduce the thickness of the portion between outer peripheral surface 112A of rotor core 112 and flux barrier 124, for example, to the manufacturing limit. This makes it possible to prevent magnetic flux from leaking from the north pole to the south pole of magnet 114 through the portion between outer peripheral surface 112A of rotor core 112 and flux barrier 124.

[0053] Furthermore, magnet 114 extends with the tangential direction of rotor core 112 as its width direction, and retaining member 132 retains the width direction end of magnet 114. Therefore, retaining member 132, which is made of a non-magnetic material, is disposed between outer peripheral surface 112A of rotor core 112 and width direction end 114A of magnet 114, and therefore retaining member 132 can be used as a member for suppressing leakage of magnetic flux from the north pole to the south pole of magnet 114.

[0054] Furthermore, a pair of holding members 132 is provided for each magnet 114, and the pair of holding members 132 holds end portions 114A on both sides in the width direction of the magnet 114. Therefore, each magnet 114 can be held in a balanced manner in the width direction of the magnet 114 by the pair of holding members 132.

[0055] Furthermore, the holder 130 has connecting members 134 that connect the multiple holding members 132. Therefore, the multiple holding members 132 can be more easily assembled to the rotor core 112 than, for example, when the connecting members 134 are omitted and the multiple holding members 132 are independent members.

[0056] Furthermore, the accommodating hole 118 is open in the axial direction of the rotor core 112, and the connecting member 134 closes the accommodating hole 118. Therefore, the connecting member 134 can prevent the magnet 114 from jumping out of the accommodating hole 118.

[0057] Third Embodiment Next, a third embodiment of the technique of the present disclosure will be described.

[0058] A rotor 210 according to a second embodiment shown in Fig. 8 is an interior permanent magnet (IPM) rotor used in an inner rotor brushless motor. The rotor 210 includes a rotor core 212, a plurality of magnets 214, and a pair of holders 230. The plurality of magnets 214 are embedded in the rotor core 212.

[0059] The rotor core 212 is a laminated body formed by stacking a plurality of core sheets in the axial direction of the rotor core 212. An outer peripheral surface 212A of the rotor core 212 is formed in a circular shape when viewed from the axial direction of the rotor core 212.

[0060] The rotor core 212 has an insertion hole 216 and a plurality of accommodating holes 218. The insertion hole 216 and the plurality of accommodating holes 218 penetrate the rotor core 212 in the axial direction. A shaft is inserted into the insertion hole 216. The insertion hole 216 is formed in the center of the rotor core 212.

[0061] The multiple accommodating holes 218 are aligned in the circumferential direction of the rotor core 212 along the outer peripheral surface 212A of the rotor core 212. Each accommodating hole 218 is located closer to the outer peripheral surface 212A than the center of the rotor core 212. As will be described later, if the magnets 214 accommodated in the accommodating holes 218 are positioned closer to the stator, which is positioned radially outward of the rotor 210, the performance of the brushless motor improves, so the accommodating holes 218 are formed at positions closer to the outer peripheral surface 212A of the rotor core 212. Each accommodating hole 218 penetrates the rotor core 212 in the axial direction.

[0062] Each magnet 214 is housed in a housing hole 218. The magnets 214 are formed in a flat plate shape and extend with the tangent direction of the rotor core 212 as the width direction. Half of the magnet 214 on the outer circumferential surface 212A side is formed by one of the north and south magnetic poles (e.g., north pole), and the half of the magnet 214 opposite the outer circumferential surface 212A is formed by the other of the north and south magnetic poles (e.g., south pole). The magnetic pole (e.g., north pole) of the half of the outer circumferential surface 212A side of one of the adjacent magnets 214 is set to a different magnetic pole from the magnetic pole (e.g., south pole) of the half of the outer circumferential surface 212A side of the other adjacent magnet 214.

[0063] 8, the number of the plurality of magnets 214 is eight, but the number of the plurality of magnets 214 may be other than eight. For example, the number of the plurality of magnets 214 may be four, six, or ten.

[0064] 9 , the inner surface of the accommodating hole 218 more specifically has an outer surface 218A, an inner surface 218B, and a pair of lateral surfaces 218C. The outer surface 218A is the surface of the inner surface of the accommodating hole 218 that is located on the outer peripheral surface 212A side, the inner surface 218B is the surface of the inner surface of the accommodating hole 218 that is located on the opposite side from the outer peripheral surface 212A (i.e., on the central side of the rotor core 212), and the pair of lateral surfaces 218C are surfaces that are located on both sides of the accommodating hole 218 in the lateral width direction.

[0065] A pair of first recesses 220 are formed in the outer surface 218A. Each first recess 220 is formed in a concave shape recessed toward the outer peripheral surface 212A. Each first recess 220 is formed at each end of the outer surface 218A in the width direction of the accommodating hole 218. The ends of the outer surface 218A in the width direction of the accommodating hole 218 correspond to the portions of the outer surface 218A corresponding to the ends 214A of the magnet 214 in the width direction. In other words, each first recess 220 is formed in a portion of the inner surface 218B corresponding to the ends 214A of the magnet 214 in the width direction. The first recesses 220 are formed to prevent the ends 214A of the magnet 214 in the width direction (particularly the corners 294) from interfering with the outer surface 218A.

[0066] A pair of second recesses 222 are formed in the inner surface 218B. Each second recess 222 is formed in a concave shape recessed on the opposite side from the outer peripheral surface 212A. Each second recess 222 is formed at each end of the inner surface 218B in the width direction of the accommodating hole 218. The ends of the inner surface 218B in the width direction of the accommodating hole 218 correspond to the portions of the inner surface 218B corresponding to the ends 214A of the magnet 214 in the width direction. In other words, each second recess 222 is formed in a portion of the inner surface 218B corresponding to the ends 214A of the magnet 214 in the width direction. The second recesses 222 are formed to prevent the ends 214A of the magnet 214 in the width direction (particularly the corners 294) from interfering with the inner surface 218B.

[0067] The magnet 214 has an outer surface 214A facing radially outward from the rotor core 212, an inner surface 214B facing radially inward from the rotor core 212, and a pair of lateral surfaces 214C facing both circumferential sides of the rotor core 212 (in other words, both tangential sides of the rotor core 212). The outer surface 214A is supported by an outer surface 218A of the inner surface of the accommodating hole 218, the inner surface 214B is supported by an inner surface 218B of the inner surface of the accommodating hole 218, and the lateral surface 214C is supported by a lateral surface 218C of the inner surface of the accommodating hole 218.

[0068] A flux barrier 224 is formed on each lateral side surface 218C. Each flux barrier 224 is formed in a concave shape that is recessed on the side away from the magnet 214 along the circumferential direction of the rotor core 212. The flux barrier 224 is a groove that ensures a gap that prevents magnetic flux from passing from the north pole to the south pole of the magnet 214. Each flux barrier 224 forms the end portion on both sides of the accommodation hole 218 in the circumferential direction of the rotor core 212.

[0069] The portions between the ends on both sides of the accommodation hole 218 in the circumferential direction of the rotor core 212 (specifically, the flux barriers 224) and the outer circumferential surface 212A of the rotor core 212 are formed as outer circumferential bridge portions 226. The outer circumferential bridge portions 226 are formed in a thin-walled shape with the thickness direction being the radial direction of the rotor core 212.

[0070] When rotor 210 rotates and centrifugal force acts on magnet 214, stress is concentrated on outer periphery bridge portion 226. That is, stress corresponding to the mass of the area including magnet 214 and the portion of rotor core 212 radially outward of magnet 214 is concentrated on outer periphery bridge portion 226.

[0071] Here, it is conceivable to increase the thickness of the outer periphery bridge portion 226 in order to ensure the holding force for the magnet 214. However, in this case, there is a risk that the leakage flux of the magnet 214 passing through the outer periphery bridge portion 226 will increase, degrading the characteristics of the brushless motor and increasing torque ripple. Therefore, there is room for improvement in suppressing stress concentration in the outer periphery bridge portion 226. The rotor 210 according to the third embodiment has the following configuration in order to suppress an increase in the thickness of the outer periphery bridge portion 226 or to reduce the thickness by suppressing stress concentration in the outer periphery bridge portion 226. This will be specifically described below.

[0072] The pair of holders 230 (see FIG. 8 ) are separate members from the rotor core 212. Hereinafter, when the pair of holders 230 are described separately, one of the pair of holders 230 will be referred to as the "first holder 230A," and the other of the pair of holders 230 will be referred to as the "second holder 230B." The first holder 230A and the second holder 230B are formed symmetrically in the axial direction of the rotor core 212. The first holder 230A is disposed on one axial side of the rotor core 212, and the second holder 230B is disposed on the other axial side of the rotor core 212.

[0073] Each holder 230 is formed of a non-magnetic material such as aluminum or stainless steel. Each holder 230 has a plurality of pressing portions 232 and an end plate 234. Hereinafter, when the end plate 234 of the first holder 230A and the end plate 234 of the second holder 230B are described separately, the end plate 234 of the first holder 230A will be referred to as the "first end plate 234A," and the end plate 234 of the second holder 230B will be referred to as the "second end plate 234B." Furthermore, when the pressing portions 232 of the first holder 230A and the pressing portions 232 of the second holder 230B are described separately, the pressing portions 232 of the first holder 230A will be referred to as the "first pressing portion 232A," and the pressing portions 232 of the second holder 230B will be referred to as the "second pressing portion 232B."

[0074] The end plate 234 is an example of an "end member" according to the technology of the present disclosure, the first end plate 234A is an example of a "first end member" according to the technology of the present disclosure, and the second end plate 234B is an example of a "second end member" according to the technology of the present disclosure. The pressing portion 232 is an example of a "restricting portion" according to the technology of the present disclosure.

[0075] The end plate 234 is formed in an annular shape. As an example, the end plate 234 is formed in an annular shape. The end plate 234 is also formed in a plate shape. The end plate 234 is provided on an end face 213A on one axial side of the rotor core 212, with the axial direction of the rotor core 212 being the plate thickness direction. The end plate 234 closes each of the accommodating holes 218 from one axial side of the rotor core 212. The second end plate 234B is provided on an end face 213B on the other axial side of the rotor core 212, and closes each of the accommodating holes 218 from one axial side of the rotor core 212.

[0076] The rotor core 212 has a plurality of through holes 236. The plurality of through holes 236 are formed in a line in the circumferential direction of the rotor core 212. As an example, the plurality of through holes 236 are formed at equal intervals in the circumferential direction of the rotor core 212. Each of the through holes 236 penetrates the rotor core 212 in the axial direction. The plurality of through holes 236 are located radially inward of the rotor core 212 with respect to the plurality of magnets 214.

[0077] Each end plate 234 has a plurality of through holes 238. The plurality of through holes 238 are formed in a line in the circumferential direction of the end plate 234. As an example, the plurality of through holes 238 are formed at equal intervals in the circumferential direction of the rotor core 212. Each through hole 238 penetrates the end plate 234 in the plate thickness direction. The plate thickness direction of the end plate 234 is the same direction as the axial direction of the rotor core 212. Each through hole 238 is formed at a position aligned with each other.

[0078] With the first end plate 234A covering the end face 213A on one axial side of the rotor core 212 and the second end plate 234B covering the end face 213B on the other axial side of the rotor core 212, rivets 240 are inserted into each of the through holes 236 and each of the through holes 238 from one axial side of the rotor core 212. Then, the tip of the rivet 240 protruding on the other axial side of the rotor core 212 is crimped. As a result, the first end plate 234A is fixed in a state where it is pressed against the end face 213A on one axial side of the rotor core 212 by the head of the rivet 240, and the second end plate 234B is fixed in a state where it is pressed against the end face 213B on the other axial side of the rotor core 212 by the crimped portion formed on the tip of the rivet 240.

[0079] The first end plate 234A covers the plurality of magnets 214 from one axial side of the rotor core 212, and the second end plate 234B covers the plurality of magnets 214 from the other axial side of the rotor core 212. The first end plate 234A prevents the magnets 214 from scattering to one axial side of the rotor core 212, and the second end plate 234B prevents the magnets 214 from scattering to the other axial side of the rotor core 212.

[0080] In each holder 230, the multiple pressing portions 232 are arranged side by side in the circumferential direction of the rotor core 212. As an example, they are arranged at equal intervals in the circumferential direction of the rotor core 212. As an example, the number of the multiple pressing portions 232 is the same as the number of the multiple magnets 214. The pressing portions 232 extend from the end plate 234 in the axial direction of the rotor core 212. Specifically, the first pressing portion 232A extends from the first end plate 234A to the other axial side of the rotor core 212, and the second pressing portion 232B extends from the second end plate 234B to one axial side of the rotor core 212.

[0081] In each holder 230, the multiple pressing portions 232 are located radially outward of the rotor core 212 relative to the multiple magnets 214. In each holder 230, the multiple pressing portions 232 may be formed integrally with the end plate 234 or may be separate. As an example, the cross-sectional shape of the pressing portion 232 is rectangular. Note that the cross-sectional shape of the groove 242 may be round, triangular, arc-shaped, or the like, other than rectangular.

[0082] The rotor core 212 has a plurality of grooves 242. The grooves 242 are an example of an "opening" according to the technology of the present disclosure. The plurality of grooves 242 are aligned in the circumferential direction of the rotor core 212. As an example, the plurality of grooves 242 are formed at equal intervals in the circumferential direction of the rotor core 212. As an example, the number of the plurality of grooves 242 is the same as the number of the plurality of retaining portions 232 (in other words, the number of magnets 214). The plurality of grooves 242 are located radially outward of the rotor core 212 relative to the plurality of magnets 214. The grooves 242 are formed in the outer peripheral surface 212A of the rotor core 212. The grooves 242 have the same cross-sectional shape as the retaining portions 232. As an example, the cross-sectional shape of the grooves 242 is rectangular. Note that the cross-sectional shape of the grooves 242 may be round, triangular, arc-shaped, or the like, in addition to a rectangular shape.

[0083] Groove 242 may penetrate rotor core 212 in the axial direction (see FIG. 10A) or may terminate at the center of rotor core 212 in the axial direction (see FIG. 10B). Hereinafter, when distinguishing between groove 242 that opens on one axial side of rotor core 212 and groove 242 that opens on the other axial side of rotor core 212, groove 242 that opens on one axial side of rotor core 212 will be referred to as "first groove 242A" and groove 242 that opens on the other axial side of rotor core 212 will be referred to as "second groove 242B".

[0084] As shown in FIG. 11 , the outer surface 214A of the magnet 214 has a first circumferential end 214A1 located on one circumferential side of the rotor core 212 and a second circumferential end 214A2 located on the other circumferential side of the rotor core 212. Here, a line extending from the rotational axis center 212C of the rotor core 212 through the first circumferential end 214A1 to the radially outer side of the rotor core 212 is referred to as a first line L1. Furthermore, a line extending from the rotational axis center 212C of the rotor core 212 through the second circumferential end 214A2 to the radially outer side of the rotor core 212 is referred to as a second line L2. The groove 242 is formed in a range R between the first line L1 and the second line L2 when viewed axially of the rotor core 212. As an example, the groove 242 is formed at a position corresponding to the center of the magnet 214 in the circumferential direction of the rotor core 212.

[0085] As shown in Figure 12, the pressing portion 232 is inserted into the groove 242. By being inserted into the groove 242, the pressing portion 232 is positioned in a range R between a first line L1 and a second line L2 when viewed in the axial direction of the rotor core 212. By being inserted into the groove 242, the pressing portion 232 is provided at a position corresponding to the center of the magnet 214 in the circumferential direction of the rotor core 212. As an example, the cross-sectional shape of the pressing portion 232 is the same as the cross-sectional shape of the groove 242. Note that the cross-sectional shape of the pressing portion 232 may be different from the cross-sectional shape of the groove 242. The pressing portion 232 is a separate part from the part of the rotor core 212 that is radially outward of the magnet 214.

[0086] When centrifugal force acts on magnet 214 due to rotation of rotor 210, pressing portion 232 receives a load from magnet 214 and thereby applies a restraining force to magnet 214 from the radially outer side of rotor core 212. In other words, pressing portion 232 plays a role in restricting the spread of rotor core 212 and magnet 214 radially outward of rotor core 212, even when centrifugal force acts on magnet 214 due to rotation of rotor 210.

[0087] 13 , the end plate 234 is fixed to the rotor core 212 by a rivet 240, radially inward of the magnet 214. The end plate 234 extends from a position radially inward of the rotor core 212 relative to the magnet 214, straddling the magnet 214, to a position radially outward of the rotor core 212 relative to the magnet 214 (i.e., in the direction of the arrow OUT). The end plate 234 has a radial overlap portion 244 that overlaps with the magnet 214 in the radial direction of the rotor core 212.

[0088] The pressing portion 232 is provided on the outer periphery of the end plate 234 (i.e., the portion on the outer periphery side). The pressing portion 232 has a tip portion 246 and a main body portion 248. The main body portion 248 is the remaining portion of the pressing portion 232 excluding the tip portion 246, and is located closer to the end plate 234 than the tip portion 246. The main body portion 248 has an axial overlap portion 250 that overlaps with the magnet 214 in the axial direction of the rotor core 212. More specifically, the axial overlap portion 250 is a portion that overlaps with a straight portion of the magnet 214 (i.e., a portion excluding the arc-shaped corner portions). The axial overlap portion 250 is an example of an "overlap portion" according to the technology of the present disclosure.

[0089] The tip portion 246 has an inclined surface 246A facing radially inward of the rotor core 212. The inclined surface 246A is inclined radially outward of the rotor core 212 toward the tip side of the tip portion 246. The main body portion 248, including the axial overlap portion 250, has an abutment surface 248A facing radially inward of the rotor core 212. The abutment surface 248A abuts against the rotor core 212 (specifically, the outer peripheral surface 212A of the rotor core 212, the bottom surface of the groove 242) from the radially outer side of the rotor core 212. The abutment surface 248A is formed linearly along the axial direction of the rotor core 212. When the abutment surface 248A abuts against the rotor core 212 from the radially outer side of the rotor core 212, the pressing portion 232 applies a restraining force to the magnet 214 from the radially outer side of the rotor core 212.

[0090] Next, the effects of the third embodiment will be described.

[0091] As described above in detail, the rotor 210 according to the third embodiment includes a retaining portion 232 in the range R between the first line L1 and the second line L2 of the rotor core 212 when viewed in the axial direction. The retaining portion 232 limits the radial outward expansion of the magnet 214 from the rotor core 212, even when the rotor 210 rotates and centrifugal force acts on the magnet 214. This prevents stress from concentrating on the outer bridge portion 226. This eliminates the need to increase the thickness of the outer bridge portion 226 to ensure a holding force for the magnet 214, allowing the outer bridge portion 226 to be thinner. This prevents an increase in leakage flux from the magnet 214 passing through the outer bridge portion 226, thereby preventing a deterioration in the brushless motor characteristics and an increase in torque ripple.

[0092] Furthermore, the end plate 234 is fixed to the rotor core 212 radially inward of the magnet 214, and extends radially outward of the rotor core 212 beyond the magnet 214, straddling the magnet 214. The rotor core 212 is located radially outward of the magnet 214 and has a groove 242 that opens in the axial direction of the rotor core 212, and the retaining portion 232 extends from the end plate 234 in the axial direction of the rotor core 212 and is inserted into the groove 242. With this configuration, the retaining portion 232, which is located radially outward of the rotor core 212 beyond the magnet 214, can apply a restraining force to the magnet 214 from the radially outer side of the rotor core 212. This allows the retaining portion 232 to limit the extension of the magnet 214 radially outward of the rotor core 212.

[0093] Furthermore, the pressing portion 232 has an axial overlap portion 250 that overlaps with the magnet 214 in the axial direction of the rotor core 212. This allows for a stronger restraining force on the magnet 214 than when, for example, the length of the pressing portion 232 is insufficient and the pressing portion 232 does not overlap with the magnet 214 in the axial direction of the rotor core 212. Furthermore, the axial overlap portion 250 has an abutment surface 248A that abuts against the rotor core 212 from the radially outer side of the rotor core 212. This allows for a stronger restraining force on the magnet 214 than when, for example, a gap is generated between the axial overlap portion 250 and the rotor core 212 and the axial overlap portion 250 does not abut against the rotor core 212.

[0094] The rotor 210 also includes a first retainer 230A and a second retainer 230B. The first retainer 230A has a first end plate 234A provided on an end face 213A on one axial side of the rotor core 212 and a first pressing portion 232A extending from the first end plate 234A to the other axial side of the rotor core 212. The second retainer 230B has a second end plate 234B provided on an end face 213B on the other axial side of the rotor core 212 and a second pressing portion 232B extending from the second end plate 234B to one axial side of the rotor core 212. The first pressing portion 232A is inserted into a first groove 242A, and the second pressing portion 232B is inserted into a second groove 242B. This allows a restraining force to be applied to the magnets 214 on both axial sides of the rotor core 212, making it possible to more effectively restrict the spread of the magnets 214 radially outward from the rotor core 212.

[0095] Furthermore, the holder 230 including the end plate 234 and the pressing portion 232 is made of a non-magnetic material, which makes it possible to prevent the magnetic flux of the magnet 214 from leaking through the holder 230.

[0096] Next, a modification of the third embodiment will be described.

[0097] As shown in FIG. 14A , in the third embodiment, a groove 242 is formed in the outer peripheral surface 212A of the rotor core 212, and the pressing portion 232 is inserted into the groove 242. However, as shown in FIG. 14B , a hole 252 opening in the axial direction of the rotor core 212 may be formed between the magnet 214 and the outer peripheral surface 212A in the radial direction of the rotor core 212, and the pressing portion 232 may be inserted into the hole 252. The hole 252 may penetrate the rotor core 212 in the axial direction or may terminate at the center of the rotor core 212 in the axial direction. As an example, the cross-sectional shape of the hole 252 is rectangular, but the cross-sectional shape of the hole 252 may be round, triangular, arc-shaped, or the like, other than rectangular. The hole 252 is an example of an "opening" according to the technology of the present disclosure.

[0098] 14(C), groove 242 may be formed on outer surface 218A of accommodating hole 218, or as shown in Fig. 14(D), groove 242 may be formed on outer surface 214A of magnet 214. As shown in Fig. 14(E), hole 252 may be formed in magnet 214. The modifications shown in Figs. 14(C) to 14(E) can contribute to the relaxation of radially outward stress corresponding only to the mass of magnet 214.

[0099] 14B to 14E, the expansion of the magnets 214 radially outward from the rotor core 212 can be restricted by the retaining portions 232. In the modified examples shown in FIGS.

[0100] In the third embodiment, the magnet 214 is formed in a flat plate shape and extends with the tangential direction of the rotor core 212 as the width direction (see FIG. 9 ). However, as shown in FIGS. 15A to 15C , the magnet 214 may be formed in a V-shape. As shown in FIG. 15A , a groove 242 may be formed in the outer peripheral surface 212A of the rotor core 212, and the retaining portion 232 may be inserted into the groove 242. As shown in FIG. 15B , a hole 252 opening in the axial direction of the rotor core 212 may be formed between the magnet 214 and the outer peripheral surface 212A in the radial direction of the rotor core 212, and the retaining portion 232 may be inserted into the hole 252.

[0101] 15(C), the groove 242 may be formed in the outer surface 218A of the accommodating hole 218. Alternatively, a plurality of grooves 242 may be formed in the outer surface 218A of the accommodating hole 218, and the pressing portion 232 may be inserted into each groove 242. Alternatively, two grooves 242 may be formed in the outer surface 218A of the accommodating hole 218, and the two grooves 242 may be formed in symmetrical positions about the center of the magnet 214 in the circumferential direction of the rotor core 212. In the modified example shown in FIG. 15(C), the number of the plurality of grooves 242 is two, but the number of the plurality of grooves 242 may be any number.

[0102] 15, the groove 242 may be formed on the outer surface 214A of the magnet 214. The hole 252 may be formed in the magnet 214.

[0103] 15(A) to 15(C) also make it possible to limit the radial outward expansion of magnet 214 from rotor core 212 by means of retaining portion 232. Furthermore, the modification shown in Fig. 15(C) can contribute to alleviating radial outward stress corresponding only to the mass of magnet 214.

[0104] 16(A) to 16(C), the magnet 214 may be formed in a U-shape. As shown in FIG. 16(A), a groove 242 may be formed in the outer peripheral surface 212A of the rotor core 212, and the retaining portion 232 may be inserted into the groove 242. As shown in FIG. 16(B), a hole 252 opening in the axial direction of the rotor core 212 may be formed between the magnet 214 and the outer peripheral surface 212A in the radial direction of the rotor core 212, and the retaining portion 232 may be inserted into the hole 252. As shown in FIG. 16(C), the groove 242 may be formed in the outer surface 218A of the accommodation hole 218.

[0105] 16, although not specifically shown, the groove 242 may be formed on the outer surface 214A of the magnet 214. The hole 252 may also be formed in the magnet 214.

[0106] 16(A) to 16(C) also make it possible to limit the radial outward expansion of magnet 214 from rotor core 212 by means of retaining portion 232. Furthermore, the modification shown in Fig. 16(C) can contribute to alleviating radial outward stress corresponding only to the mass of magnet 214.

[0107] As shown in FIG. 17A , in the third embodiment, a plurality of grooves 242 are formed in the outer peripheral surface 212A of the rotor core 212, and a plurality of pressing portions 232 are inserted into the plurality of grooves 242. However, as shown in FIGS. 17B and 17C , the pressing portions 232 may be formed in an annular shape along the circumferential direction of the rotor core 212 and fitted to the outer peripheral surface 212A of the rotor core 212. As shown in FIG. 17B , the inner peripheral surface of the pressing portion 232 and the outer peripheral surface 212A of the rotor core 212 may be formed in a circular shape, or as shown in FIG. 17C , they may be formed in a polygonal shape. As shown in FIG. 17D , the grooves 242 may be omitted from the outer peripheral surface 212A of the rotor core 212, and the plurality of pressing portions 232 may be fitted to the outer peripheral surface 212A of the rotor core 212. Note that the magnet 214 is not shown in FIG. 17 .

[0108] 17(B) to 17(D) also make it possible to restrict the expansion of magnet 214 radially outward from rotor core 212 by means of retaining portion 232. In particular, as shown in Figures 17(B) and 17(C), when retaining portion 232 is formed in an annular shape, the rigidity of retaining portion 232 can be increased compared to when multiple retaining portions 232 are used, and therefore the restraining force on magnet 214 can be increased.

[0109] 17(A), if a plurality of grooves 242 are formed in the outer peripheral surface 212A of the rotor core 212 and a plurality of pressing portions 232 are inserted into the plurality of grooves 242, each pressing portion 232 can be deformed when assembling the holder 230 to the rotor core 212, thereby improving the ease of assembly of the holder 230. Similarly, as shown in FIG. 17(D), if a plurality of pressing portions 232 are fitted into the outer peripheral surface 212A of the rotor core 212, each pressing portion 232 can be deformed when assembling the holder 230 to the rotor core 212, thereby improving the ease of assembly of the holder 230.

[0110] 17(A), when a plurality of grooves 242 are formed in the outer peripheral surface 212A of the rotor core 212 and a plurality of pressing portions 232 are inserted into the plurality of grooves 242, the holder 230 can be positioned in the circumferential direction of the rotor core 212. Similarly, when the inner peripheral surfaces of the pressing portions 232 and the outer peripheral surface 212A of the rotor core 212 are formed in a polygonal shape, as shown in FIG.

[0111] 18(A), the pressing portion 232 may extend with the tangential direction of the rotor core 212 as the width direction. Also, as shown in FIG. 18(B), the cross-sectional shape of the pressing portion 232 may be rectangular with the radial direction of the rotor core 212 as the longitudinal direction. This configuration increases the restraining force on the magnet 214 compared to when the cross-sectional shape of the pressing portion 232 is rectangular with the radial direction of the rotor core 212 as the short side direction. Also, as shown in FIG. 18(C), the pressing portion 232 may be located at a position offset in the circumferential direction of the rotor core 212 from the center of the magnet 214 in the circumferential direction of the rotor core 212.

[0112] 18(D), a plurality of grooves 242 may be formed in the outer peripheral surface 212A of the rotor core 212 for each magnet 214, and a pressing portion 232 may be inserted into each groove 242. Alternatively, two grooves 242 may be formed in the outer peripheral surface 212A of the rotor core 212 for each magnet 214, and the two grooves 242 may be formed at positions symmetrical with respect to the center of the magnet 214 in the circumferential direction of the rotor core 212. In the modified example shown in FIG. 18(D), the number of grooves 242 is two, but the number of grooves 242 may be any number.

[0113] 18A to 18D, the expansion of the magnets 214 radially outward from the rotor core 212 can be restricted by the retaining portions 232. In the modified examples shown in FIGS.

[0114] 19(A), the positions of the holding portions 232 in the circumferential direction of the rotor core 212 may be different between the first holder 230A and the second holder 230B. Also, as shown in FIG. 19(B), only a second end plate 234B may be provided on the end face 213B on the other axial side of the rotor core 212, instead of the second holder 230B. Also, as shown in FIG. 19(C), only a first end plate 234A may be provided on the end face 213A on one axial side of the rotor core 212, instead of the first holder 230A.

[0115] 20(A) , in a configuration in which magnet 214 is formed in a V-shape, rivet 240 may be inserted into hole 252 formed between magnet 214 and outer peripheral surface 212A in the radial direction of rotor core 212. Similarly, as shown in FIG. 20(B) , in a configuration in which magnet 214 is formed in a U-shape, rivet 240 may be inserted into hole 252 formed between magnet 214 and outer peripheral surface 212A in the radial direction of rotor core 212. Then, rivet 240 may limit the expansion of magnet 214 radially outward of rotor core 212. In the modified examples shown in FIGS. 20(A) and 20(B) , rivet 240 is an example of a "limiting portion" and a "holding portion" according to the technology of the present disclosure.

[0116] The modified example shown in FIGS. 20A and 20B also makes it possible to limit the radial outward expansion of the magnets 214 from the rotor core 212.

[0117] 21(A) to 21(C), a balancer 260 may be provided on the end plate 234. The balancer 260 may be provided on a portion of the end plate 234 in the circumferential direction. As shown in Fig. 21(A), the balancer 260 may be formed in a block shape, or as shown in Fig. 21(B), the balancer 260 may be formed by a laminate in which a plurality of plate members 262 are stacked.

[0118] 21(A) and 21(B), the balancer 260 may be configured as a separate body from the end plate 234, or as shown in Fig. 21(C), the balancer 260 may be formed integrally with the end plate 234. When the balancer 260 is formed integrally with the end plate 234, the number of parts can be reduced compared to when the balancer 260 and the end plate 234 are separate bodies.

[0119] 21A to 21C, the end plate 234 may be made of a non-magnetic material. This makes it possible to prevent the magnetic flux of the magnet 214 from leaking through the end plate 234. Furthermore, when the end plate 234 is made of a non-magnetic material, the balancer 260 may be made of a magnetic material.

[0120] 21(D), a balancer 270 may be used instead of the end plate 234, and multiple retaining portions 232 may be provided on the balancer 270. Like the end plate 234, the balancer 270 may be fixed to the rotor core 212 radially inward of the magnet 214, and may extend across the magnet 214 radially outward of the rotor core 212. This reduces the number of parts compared to using the end plate 234 and the balancer 270. Similarly to the end plate 234, the balancer 270 may cover multiple magnets 214. This prevents the magnet 214 from flying off. The balancer 270 is an example of an "end member" according to the technology disclosed herein.

[0121] The balancer 270 may also be made of a non-magnetic material. In this way, leakage of magnetic flux from the magnet 214 through the balancer 270 can be suppressed. The balancer 270 may also have a negative balance portion 272. The negative balance portion 272 may be formed in a concave shape that opens in the axial direction of the balancer 270. The negative balance portion 272 may also be formed radially inward of the outer periphery of the balancer 270. Furthermore, the negative balance portion 272 may be provided on a portion of the balancer 270 in the circumferential direction.

[0122] 22(A), when balancer 260 is used on the other axial side of rotor core 212, jig 274 is required to align the height of rotor core 212 with when balancer 260 is not used. In contrast, when balancer 270 is used, as shown in FIG. 22(B), the balance of rotor core 212 can be adjusted by changing the depth, position, shape, etc. of negative balance portion 272. This allows the components used as balancer 270 to be standardized, making jig 274 unnecessary.

[0123] 23A , instead of restricting the radial outward expansion of the magnet 214 from the rotor core 212 by the retaining portion 232, the magnet 214 may have a convex engaging portion 280 that protrudes in the axial direction of the rotor core 212, and the end plate 234 may have a concave engaged portion 282 that opens in the axial direction of the rotor core 212. The engaging portion 280 and the engaged portion 282 form an engaging structure 284. When the engaging portion 280 is engaged with the engaged portion 282, the radial outer side of the engaging portion 280 may abut against the radial inner side of the engaged portion 282, thereby restricting the radial outward expansion of the magnet 214 from the rotor core 212. The fitting structure 284 is an example of a "restricting portion" according to the technology of the present disclosure.

[0124] 23(B), the magnet 214 may have a recessed fitting portion 286 that opens in the axial direction of the rotor core 212, and the end plate 234 may have a convex fitted portion 288 that protrudes in the axial direction of the rotor core 212. The fitting portion 286 and the fitted portion 288 form a fitting structure 290. The fitting portion 286 may be fitted into the fitted portion 288, thereby restricting the magnet 214 from expanding radially outward from the rotor core 212. The fitting structure 290 is an example of a "restricting portion" according to the technology of the present disclosure.

[0125] 24 , the end plate 234 may have a bent portion 292 bent toward the magnet 214. The bent portion 292 may be a cut-and-raised piece formed at a position corresponding to the magnet 214. Furthermore, a corner 294 of the magnet 214 located radially outward from the rotor core 212 may be chamfered more, and the tip of the bent portion 292 may be hooked onto the corner 294. Then, by hooking the tip of the bent portion 292 onto the corner 294, the extension of the magnet 214 radially outward from the rotor core 212 may be restricted. The bent portion 292 is an example of a "restricting portion" according to the technology of the present disclosure.

[0126] 25(A), the magnet 214 and the rotor core 212 may be fixed with an adhesive 296. For example, the inner surface 214B of the magnet 214 and the inner surface 218B of the accommodating hole 218 may be fixed with the adhesive 296. Furthermore, as shown in FIG. 25(B), the magnet 214 and the end plate 234 may be fixed together by providing an adhesive 296 between the magnet 214 and the end plate 234 in the axial direction of the rotor core 212. The adhesive 296 may then limit the expansion of the magnet 214 radially outward from the rotor core 212. The adhesive 296 is an example of a "limiting portion" according to the technology of the present disclosure.

[0127] 26 , the end plate 234 and the rotor core 212 may be fixed by a weld 298. The weld 298 may be formed by various types of welding, such as arc welding, laser welding, or electron beam welding. The weld 298 may be formed across the outer circumferential surface of the end plate 234 and the outer circumferential surface 212A of the rotor core 212. The weld 298 may extend in the axial direction of the rotor core 212. The weld 298 may limit the expansion of the magnet 214 radially outward from the rotor core 212. The weld 298 is an example of a "limiting portion" according to the technology of the present disclosure.

[0128] Furthermore, the welded portion 298 may have an axial overlap portion 300 that overlaps with the magnet 214 in the axial direction of the rotor core 212. The axial overlap portion 300 may be a portion that overlaps with a straight portion of the magnet 214 (i.e., a portion excluding the arc-shaped corner portions). When the welded portion 298 has the axial overlap portion 300, the restraining force on the magnet 214 can be increased compared to when the length of the welded portion 298 is insufficient and the welded portion 298 does not overlap with the magnet 214 in the axial direction of the rotor core 212. The axial overlap portion is an example of an "overlap portion" according to the technology of the present disclosure.

[0129] 27 , the rotor core 212 may have a convex mating portion 302 that protrudes in the axial direction of the rotor core 212, and the end plate 234 may have a recessed or hole-shaped mated portion 304 that opens in the axial direction of the rotor core 212. The mating portion 302 is located radially outward of the rotor core 212 relative to the magnet 214. The mating portion 302 and the mated portion 304 form a mating structure 306. The mating portion 302 may be mated with the mated portion 304 to restrict the magnet 214 from expanding radially outward of the rotor core 212. The mating structure 306 is an example of a "restricting portion" according to the technology of the present disclosure.

[0130] Furthermore, rotor core 212 may be configured by a plurality of core sheets 308, and the plurality of core sheets 308 may be fixed to one another by crimped portions 310. Furthermore, fitting portion 302 may be formed by crimped portions 310 formed on core sheets 308 located at the axial end portions of rotor core 212.

[0131] 28 , the end plate 234 may have a bent portion 312 bent toward the magnet 214. The bent portion 312 may be formed by bending or the like. Furthermore, the axial length of the magnet 214 may be shorter than the axial length of the rotor core 212, thereby providing a step portion 314 between the rotor core 212 and the magnet 214 in the axial direction of the rotor core 212, and the bent portion 312 may be fitted into the step portion 314. The bent portion 312 formed on the first end plate 234A and the bent portion 312 formed on the second end plate 234B may sandwich the magnet 214 from both axial sides of the rotor core 212. By sandwiching the magnet 214 between the pair of bent portions 312, the magnet 214 may be limited from expanding radially outward from the rotor core 212. The pair of bent portions 312 constitute a sandwiching structure 316 that sandwiches and fixes the magnet 214. The sandwiching structure 316 is an example of a "restriction portion" according to the technology of the present disclosure.

[0132] 29A , a convex mating portion 318 may be formed on the inner surface 214B of the magnet 214, and a concave mated portion 320 may be formed on the inner surface 218B of the accommodating hole 218 facing the inner surface 214B of the magnet 214. The mating portion 318 and the mated portion 320 constitute a mating structure 322. The mating portion 318 and the mated portion 320 may be formed in a tapered shape that narrows toward the radially outward direction of the rotor core 212. The mating portion 318 may be mated with the mated portion 320 to limit the radially outward expansion of the magnet 214. The mating structure 322 is an example of a "limiting portion" according to the technology of the present disclosure. The inner surface 218B of the accommodating hole 218 is an example of a "facing surface" according to the technology of the present disclosure.

[0133] 29(B), a concave fitting portion 324 may be formed on the inner surface 214B of the magnet 214, and a convex fitted portion 326 may be formed on the inner surface 218B of the accommodating hole 218 facing the inner surface 214B of the magnet 214. The fitting portion 324 and the fitted portion 326 constitute a fitting structure 328. The fitting portion 324 and the fitted portion 326 may be formed in a tapered shape that widens radially outward of the rotor core 212. The fitting portion 324 may be fitted into the fitted portion 326 to limit the radial outward expansion of the magnet 214. The fitting structure 328 is an example of a "limiting portion" according to the technology of the present disclosure. The inner surface 218B of the accommodating hole 218 is an example of a "facing surface" according to the technology of the present disclosure.

[0134] Among the modifications described for the third embodiment, modifications that can be combined may be combined as appropriate.

[0135] The above describes one embodiment of the technology of the present disclosure, but the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modified forms within the scope of the gist of the present disclosure.

[0136] The following are supplementary notes regarding the technology of the present disclosure. (Supplementary Note 1) A rotor (10) comprising: a rotor core (12); and a magnet (14) embedded in the rotor core, wherein the rotor core has an accommodating hole (18) located closer to the outer peripheral surface (12A) of the rotor core than the center of the rotor core, the magnet is accommodated in the accommodating hole, a foamable resin (20) having foamability is filled between the inner surface of the accommodating hole and the magnet, and an outer surface (18A) of the inner surface located on the outer peripheral surface side is formed with a relief groove (22) recessed toward the outer peripheral surface. (Supplementary Note 2) The magnet extends with a tangential direction of the rotor core as its width direction, and the relief groove is formed in a portion of the outer surface corresponding to an end (14A) of the magnet in the width direction. (Supplementary Note 3) The rotor according to Supplementary Note 1 or Supplementary Note 2, wherein a gap (24) between the outer surface and the magnet is smaller than a gap (26) between the magnet and an inner surface (18B) of the inner surface located closer to the center. (Supplementary Note 4) A rotor (10) comprising: a rotor core (112); and a magnet (114) embedded in the rotor core, the rotor core having an accommodating hole (118) located closer to the outer surface (112A) of the rotor core than the center of the rotor core, the magnet being accommodated in the accommodating hole and held from the outer surface side of the rotor core by a holding member (132) separate from the rotor core. (Supplementary Note 5) The rotor according to Supplementary Note 4, wherein the magnet extends with a tangential direction of the rotor core as a width direction, and the holding member holds an end (114A) of the magnet in the width direction. (Supplementary Note 6) The rotor according to Supplementary Note 5, wherein a pair of the holding members is provided for one of the magnets, and the pair of the holding members holds both end portions of the magnet in the width direction.(Supplementary Note 7) The rotor according to any one of Supplementary Notes 4 to 6, wherein the rotor comprises: a plurality of the magnets; and a holder (30) having a plurality of the holding members that respectively hold the plurality of magnets, wherein the holder has a connecting member (134) that connects the plurality of holding members. (Supplementary Note 8) The rotor according to Supplementary Note 7, wherein the accommodating hole opens in the axial direction of the rotor core, and the connecting member closes the accommodating hole. (Supplementary Note 9) The rotor according to any one of Supplementary Notes 4 to 8, wherein the holding member is formed of a non-magnetic material. (Supplementary Note 10) A rotor core (212) comprising: a magnet (214) embedded in the rotor core, wherein the magnet has an outer surface (214A) facing radially outward of the rotor core, the outer surface having a first circumferential end (214A1) located on one circumferential side of the rotor core and a second circumferential end (214A2) located on the other circumferential side of the rotor core, A rotor (210) in which, when a line extending from the rotational axis center (212C) of the rotor core through the first circumferential end to the radially outer side of the rotor core is defined as a first line (L1), and a line extending from the rotational axis center of the rotor core through the second circumferential end to the radially outer side of the rotor core is defined as a second line (L2), a range (R) between the first line and the second line when viewed in the axial direction of the rotor core is provided with limiting portions (232, 240, 284, 290, 292, 296, 298, 306, 316, 322, 328) that limit the spread of the magnets radially outward of the rotor core.(Supplementary Note 11) The rotor according to Supplementary Note 10, comprising an end member (234, 270) provided on an axial end surface of the rotor core and covering the magnet, the end member being fixed to the rotor core radially inward of the magnet and spanning the magnet and extending radially outward of the rotor core beyond the magnet, the rotor core being located radially outward of the magnet from the rotor core and having an opening (242, 252) that opens in the axial direction of the rotor core, and the limiting portion having a pressing portion (232, 240) extending from the end member in the axial direction of the rotor core and inserted into the opening. (Supplementary Note 12) The rotor according to Supplementary Note 11, wherein the pressing portion has an axial overlap portion (250) that overlaps with the magnet in the axial direction of the rotor core, and the overlap portion has an abutment surface (248A) that abuts against the rotor core from the radially outer side of the rotor core. (Supplementary Note 13) The rotor according to Supplementary Note 11 or Supplementary Note 12, comprising: a first end member (234A) as the end member provided on an end face on one axial side of the rotor core; and a second end member (234B) as the end member provided on an end face on the other axial side of the rotor core, wherein a first pressing portion (232A) as the pressing portion extends from the first end member, and a second pressing portion (232B) as the pressing portion extends from the second end member. (Supplementary Note 14) The rotor according to any one of Supplementary Notes 11 to 13, wherein the end member and the pressing portion are formed of a non-magnetic material. (Supplementary Note 15) The rotor according to Supplementary Note 10, wherein the magnet has an inner surface (214B) facing radially inward of the rotor core, the rotor core has an opposing surface (218B) opposing the inner surface, and the limiting portion has: an engaging portion (318, 324) formed on the inner surface; and an engaged portion (320, 326) formed on the opposing surface and engaged with the engaging portion.

Claims

1. A rotor (10) comprising: a rotor core (12); and a magnet (14) embedded in the rotor core, wherein the rotor core has a housing hole (18) located closer to the outer peripheral surface (12A) of the rotor core than the center of the rotor core; the magnet is housed in the housing hole; a foamable resin (20) having foaming properties is filled between the inner surface of the housing hole and the magnet; and an outer surface (18A) of the inner surface located on the outer peripheral surface side is formed with an escape groove (22) recessed toward the outer peripheral surface.

2. A rotor as set forth in claim 1, wherein the magnet extends in a width direction that is tangent to the rotor core, and the relief groove is formed in a portion of the outer surface that corresponds to the end (14A) of the magnet in the width direction.

3. A rotor according to claim 1 or claim 2, wherein a gap (24) between the outer surface and the magnet is smaller than a gap (26) between the magnet and an inner surface (18B) of the inner surface located closer to the center.

4. A rotor (110) comprising: a rotor core (112); and a magnet (114) embedded in the rotor core, wherein the rotor core has an accommodating hole (118) located closer to the outer peripheral surface (112A) of the rotor core than the center of the rotor core; and the magnet is accommodated in the accommodating hole and is held from the outer peripheral surface side of the rotor core by a holding member (132) separate from the rotor core.

5. A rotor according to claim 4, wherein the magnet extends in a width direction that is tangent to the rotor core, and the holding member holds an end (114A) of the magnet in the width direction.

6. A rotor according to claim 5, wherein a pair of the holding members is provided for each of the magnets, and the pair of holding members holds both end portions of the magnet in the width direction.

7. The rotor according to claim 4, wherein the rotor comprises: a plurality of the magnets; and a holder (130) having a plurality of the holding members that respectively hold the plurality of the magnets, and the holder has connecting members (134) that connect the plurality of the holding members.

8. The rotor according to claim 4, wherein the accommodating hole is open in the axial direction of the rotor core, and the connecting member closes the accommodating hole.

9. The rotor according to claim 4, wherein the retaining member is made of a non-magnetic material.

10. A rotor core (212) and a magnet (214) embedded in the rotor core, wherein the magnet has an outer surface (214A) facing radially outward from the rotor core, and the outer surface has a first circumferential end (214A1) located on one circumferential side of the rotor core and a second circumferential end (214A2) located on the other circumferential side of the rotor core, A rotor (210) in which, when a line extending from the rotational axis center (212C) of the rotor core through the first circumferential end to the radially outer side of the rotor core is defined as a first line (L1), and a line extending from the rotational axis center of the rotor core through the second circumferential end to the radially outer side of the rotor core is defined as a second line (L2), a range (R) between the first line and the second line when viewed in the axial direction of the rotor core is provided with limiting portions (232, 240, 284, 290, 292, 296, 298, 306, 316, 322, 328) that limit the spread of the magnets radially outward of the rotor core.

11. A rotor as set forth in claim 10, comprising an end member (234, 270) provided on an axial end face of the rotor core and covering the magnet, the end member being fixed to the rotor core radially inward of the magnet and extending radially outward of the rotor core beyond the magnet, straddling the magnet, the rotor core being located radially outward of the magnet and having an opening (242, 252) that opens in the axial direction of the rotor core, and the limiting portion having a pressing portion (232, 240) that extends from the end member in the axial direction of the rotor core and is inserted into the opening.

12. A rotor as set forth in claim 11, wherein the pressing portion has an axial overlap portion (250) that overlaps with the magnet in the axial direction of the rotor core, and the overlap portion has an abutment surface (248A) that abuts against the rotor core from the radial outside of the rotor core.

13. A rotor as set forth in claim 11 or claim 12, comprising: a first end member (234A) as the end member provided on an end face on one axial side of the rotor core; and a second end member (234B) as the end member provided on an end face on the other axial side of the rotor core, wherein a first pressing portion (232A) as the pressing portion extends from the first end member, and a second pressing portion (232B) as the pressing portion extends from the second end member.

14. A rotor according to any one of claims 11 to 13, wherein the end members and the pressing portions are made of non-magnetic materials.

15. A rotor as set forth in claim 10, wherein the magnet has an inner surface (214B) facing radially inward of the rotor core, the rotor core has an opposing surface (218B) opposing the inner surface, and the restricting portion has: an engaging portion (318, 324) formed on the inner surface; and an engaged portion (320, 326) formed on the opposing surface and engaged with the engaging portion.