Rotor and rotor manufacturing method

Abstract

To easily manufacture a rotor while maintaining and improving a force for retaining a permanent magnet.SOLUTION: A rotor 1 includes a rotor shaft 11, a rotor core 12 including a magnet housing hole 122, a permanent magnet 13 housed in the magnet housing hole with a gap therebetween, and a resin part 14 that fixes the permanent magnet. The resin part 14 includes a core end surface resin section 141 disposed on an end surface of the rotor core, and an intra-core resin section 143 disposed so as to fill the space between the permanent magnet and the magnet housing hole. The core end surface resin section 141 is configured to, in an axial direction view, cover a portion of an end surface 131 of the permanent magnet 13 by covering a portion of the magnet housing hole 122, and expose at least two corners C1 and C3 of the end surface 131 of the permanent magnet 13 without covering a portion of long sides S1, S2 and short sides S3, S4 defining the respective corners.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rotor that constitutes a motor and a method for manufacturing the rotor. [Background technology]

[0002] The main components that make up a motor are the stator and the rotor. For example, the stator is provided with a coil that generates a magnetic field when a current is passed through it. The rotor is provided with a permanent magnet that reacts with the magnetic field generated by the coil. The rotor rotates when the permanent magnet reacts with the magnetic field generated by the coil. There are various methods for attaching a permanent magnet to the rotor. One known attachment method is to embed the permanent magnet inside the rotor core with resin. This type of rotor is disclosed, for example, in Patent Document 1.

[0003] The rotor of Patent Document 1 has a magnet accommodating hole provided in a rotor core formed by laminating electromagnetic steel sheets. The magnet accommodating hole has an oval shape when viewed in the rotor axial direction, and penetrates the rotor core in the rotor axial direction. A permanent magnet is accommodated inside the magnet accommodating hole and is filled with resin. The filled resin forms a magnet fixing resin part that holds the permanent magnet in the rotor molded product. A roughly annular rotor core clamping resin part is provided on both end faces in the axial direction of the rotor core so as to follow the outer periphery of the rotor core. The rotor core clamping resin part is provided so as to cover both end ends of the opening of the magnet accommodating hole. No rotor core clamping resin part is provided in the center of the opening of the magnet accommodating hole, and the center part of the permanent magnet is exposed.

[0004] This rotor is manufactured as follows. First, the rotor core is placed on a lower mold engraved with the shape of one of the rotor core clamping resin parts. Next, a permanent magnet is inserted into the magnet accommodating hole, and an upper mold engraved with the shape of the other rotor core clamping resin part is placed. The upper and lower molds contact the central parts of the upper and lower surfaces of the permanent magnet, respectively, and sandwich and position the permanent magnet. This contact part corresponds to the exposed part of the permanent magnet in the molded rotor. Next, resin is injected into the mold, and the two rotor core clamping resin parts and the magnet fixing resin part are injection molded. In the mold, the space for molding the two rotor core clamping resin parts and the space for molding the magnet fixing resin part are connected via both ends of the magnet accommodating hole. Therefore, the two rotor core clamping resin parts and the magnet fixing resin part are molded integrally. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-142038 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the rotor of Patent Document 1, the two rotor core clamping resin parts and the magnet fixing resin part are molded at the same time, so that the rotor manufacturing efficiency can be improved, the manufacturing cost can be reduced, and the weight can be reduced. In addition, in the rotor manufacturing method of Patent Document 1, the central parts of the upper and lower surfaces of the permanent magnet are abutted against a mold, and the permanent magnet is sandwiched between the upper and lower sides and positioned. Since this method does not require a positioning pin for the permanent magnet, a hole for the positioning pin is not provided in the rotor core clamping resin part. As a result, even if the parts that hold the permanent magnet, such as the two rotor core clamping resin parts and the magnet fixing resin part, are made of resin, the holding force of the permanent magnet can be maintained or improved. The present inventor has studied a method for facilitating the manufacturing of a rotor while maintaining or improving the holding force of the permanent magnet by a method different from that of Patent Document 1.

[0007] An object of the present invention is to provide a rotor and a method for manufacturing a rotor that facilitates the manufacture of the rotor while maintaining or improving the holding force of a permanent magnet. [Means for solving the problem]

[0008] (1) The rotor of the present invention is a rotor for a motor including a rotor shaft, a rotor core including a magnet accommodating hole penetrating the rotor shaft in the axial direction and fixed to the rotor shaft, a permanent magnet accommodated in the magnet accommodating hole with a gap therebetween and having four corners defined by long sides and short sides that respectively constitute the end face on at least one end face in the axial direction, and a resin part that fixes the permanent magnet. The resin part includes a core end face resin part provided on at least one end face of the rotor core in the axial direction, and an inner-core resin part that is provided so as to fill the gap and is connected to the core end face resin part. The core end face resin part is configured to cover a part of the end face of the permanent magnet by covering a part of the magnet accommodating hole as viewed in the axial direction, and to expose at least two corners of the end face of the permanent magnet by not covering a part of the long sides and short sides that define each corner.

[0009] In the rotor described above, at least two corners are exposed on the end face of the permanent magnet. These exposed parts are formed by abutting the permanent magnet and a die when forming the resin part. That is, in the manufacturing process, when the permanent magnet is accommodated in the magnet accommodation hole before molding the resin part, at least two exposed parts on the end face (lower face) of the permanent magnet are supported by the lower die. For example, two corners located diagonally on the end face of the permanent magnet are supported by the die, or both corners of one long side of the end face and a part of the other long side are supported by the die. Therefore, even if the support area is small, the die can support the permanent magnet, and molding of the resin part becomes easy. In addition, since the exposed area of ​​the permanent magnet can be reduced when viewed in the axial direction, the area of ​​the core end face resin part can be increased, and even if the part holding the permanent magnet is made of resin, the holding force of the permanent magnet is not likely to decrease. Therefore, according to the rotor described above, it is possible to easily manufacture the rotor while maintaining or improving the holding force of the permanent magnet.

[0010] (2) In the rotor of (1) above, the core end face resin portion may be configured to expose at least two diagonally opposite corners on the end face of the permanent magnet when viewed in the axial direction by not covering a portion of the long side and short side defining each corner.

[0011] In the rotor (2) above, both ends of the diagonal at the end face of the permanent magnet are supported by the die. Because both ends of the diagonal, which is the longest imaginary line at the end face of the permanent magnet, are supported by the die, the die can support the permanent magnet even if the exposed area of ​​the permanent magnet is made smaller. Therefore, with the rotor described above, it is possible to easily manufacture the rotor while maintaining or improving the holding force of the permanent magnet.

[0012] (3) In the rotor of (1) or (2) above, the core end surface resin portion may be configured so that an exposed area of ​​the end face of the permanent magnet is smaller than an area that the core end surface resin portion covers the magnet accommodating hole.

[0013] In the rotor of (3) above, the exposed area of ​​the permanent magnet can be reduced, and therefore the area of ​​the core end face resin portion can be increased. Therefore, the rotor described above can be easily manufactured while maintaining or improving the holding force of the permanent magnet. The core end face resin portion may be configured such that the exposed area of ​​the end face of the permanent magnet is smaller than the area where the core end face resin portion covers the end face of the permanent magnet.

[0014] (4) In any of the rotors (1) to (3) above, the core end face resin portion may be configured to expose at least two corners by not covering up to ¼ of the long sides and not more than ½ of the short sides defining each corner.

[0015] In the rotor of (4) above, the exposed area of ​​the permanent magnet can be reduced, and therefore the area of ​​the core end face resin portion can be increased, making it easier to manufacture the rotor while maintaining or improving the retention force of the permanent magnet.

[0016] (5) In any of the rotors (1) to (4) above, a gap may be provided between an inner surface of the magnet accommodating hole and at least one short side of an end face of the permanent magnet when viewed in the axial direction. The core end face resin portion may be configured to cover a part of the one short side and to cover at least a part of the gap when viewed in the axial direction.

[0017] In the rotor of (5) above, the resin portion in the core formed by the resin filled in the gap adjacent to the short side mainly plays a role in fixing the permanent magnet. Therefore, for example, the gap between the long side and the inner surface of the magnet accommodating hole can be reduced when viewed in the axial direction. By reducing the gap adjacent to the long side, the position of the permanent magnet is easily maintained when the permanent magnet is accommodated in the magnet accommodating hole in the absence of the resin portion. Therefore, according to the rotor described above, it is possible to easily manufacture the rotor while maintaining or improving the holding force of the permanent magnet.

[0018] (6) In the rotor according to any one of the above (1) to (5), the core end surface resin portion may have an annular shape and be provided on the end surface of the rotor core in a circumferential direction of the rotor core. The core end surface resin portion may have an outer circumferential edge having a continuous uneven shape along the circumferential direction of the rotor shaft.

[0019] In the rotor of (6) above, for example, the portion requiring strength, such as the connection portion between the core end face resin portion and the core internal resin portion, can be made into a convex shape that is long in the radial direction of the rotor shaft, and the portion requiring less strength can be made into a concave shape that is short in the radial direction. In other words, more resin is supplied to the portion requiring strength, and less resin is supplied to the portion requiring less strength. Therefore, according to the rotor described above, it is possible to easily manufacture the rotor while maintaining or improving the holding force of the permanent magnets, and to reduce the weight of the rotor.

[0020] (7) In any of the rotors (1) to (6) above, the core end face resin portion may include, on an end face in the axial direction, a reference portion that serves as a cutting reference position for adjusting the weight balance of the rotor.

[0021] After the rotor is manufactured, the rotational balance is adjusted and the rotor is made into a product. The rotational balance is adjusted, for example, by cutting a part of the core end face resin part of the rotor. In the rotor of (7) above, a reference part is provided as a cutting reference position. Therefore, with the rotor, it is possible to easily manufacture the rotor while maintaining or improving the holding force of the permanent magnet, and it is also possible to easily adjust the rotational balance of the rotor. In particular, in the case of a rotor in which the core end face resin part has an uneven outer periphery, by providing a reference part in the convex part where a large amount of resin is supplied, it is possible to easily adjust the rotational balance of the rotor while maintaining or improving the holding force of the permanent magnet.

[0022] The method for manufacturing a rotor for a motor according to the present invention includes the steps of preparing a mold including an upper mold and a lower mold, arranging a rotor core including a magnet accommodating hole that axially penetrates a rotor shaft through hole that attaches a rotor shaft to the lower mold, and accommodating a permanent magnet having four corners defined by long sides and short sides that constitute at least one end face in the axial direction, with the end face facing the lower mold, in the magnet accommodating hole of the rotor core arranged in the lower mold with a gap therebetween, and combining the upper mold with the lower mold, injecting resin into the mold, and fixing the permanent magnet accommodated in the magnet accommodating hole. In the step of preparing the mold, a lower mold is prepared that includes a support portion that supports the end face of the permanent magnet and is engraved with the shape of a core end face resin portion that is provided on the end face of the rotor core that abuts against the lower mold. In the step of fixing the permanent magnet, the resin is injected into the mold to fill the magnet accommodating hole through the gap, and an internal core resin portion that is provided in the rotor so as to fill the gap and is connected to the core end face resin portion is molded integrally with the core end face resin portion. In the process of accommodating a permanent magnet, when viewed in the axial direction, a space is provided between a part of the magnet accommodating hole and the lower mold so that a part of the end face of the permanent magnet is not abutted against the lower mold, while at least two corners of the end face of the permanent magnet are abutted against the lower mold so that a part of the long side and a part of the short side defining each corner are supported by support portions.

[0023] Each component and terminology of the present invention will be described below.

[0024] The "rotor shaft" has, for example, a cylindrical shape. The rotor shaft may have, for example, a cylindrical shape. The rotor shaft includes, for example, a rotation shaft of a rotor. For example, the rotor rotates when the rotor shaft rotates. The rotor shaft corresponds to, for example, an output shaft of a motor.

[0025] The "rotor core" rotates integrally with, for example, the rotor shaft. The rotor core is formed, for example, by laminating a plurality of electromagnetic steel plates. The rotor core has, for example, a cylindrical shape. The rotor core includes, for example, a rotor shaft through hole through which the rotor shaft passes and is fixed. The rotor shaft through hole opens, for example, at both end faces in the axial direction of the rotor shaft. The rotor shaft through hole is provided, for example, such that its central axis substantially coincides with the central axis of the rotor core.

[0026] The rotor core includes, for example, at least one magnet accommodating hole. The at least one magnet accommodating hole opens, for example, to both end faces in the axial direction of the rotor shaft. When the rotor core includes multiple magnet accommodating holes, the multiple magnet accommodating holes are arranged, for example, along the circumferential direction of the rotor core. In a cross section perpendicular to the axial direction of the rotor shaft, the shape of the at least one magnet accommodating hole is not particularly limited. However, in a cross section perpendicular to the axial direction of the rotor shaft, the cross-sectional area of ​​the at least one magnet accommodating hole is larger than the cross-sectional area of ​​the permanent magnet. The at least one magnet accommodating hole has, for example, a volume larger than the permanent magnet.

[0027] The "permanent magnet" is housed in, for example, a magnet accommodating hole. When multiple magnet accommodating holes are provided, multiple permanent magnets are also provided. The multiple permanent magnets are each housed in a corresponding magnet accommodating hole. The type of permanent magnet is not particularly limited. The permanent magnet is, for example, a neodymium magnet. The permanent magnet may be, for example, a ferrite magnet. The permanent magnet may be, for example, a sintered magnet or a bonded magnet. The shape of the permanent magnet is not particularly limited. The permanent magnet has, for example, a rectangular parallelepiped shape. The permanent magnet may have, for example, a curved shape in a cross section perpendicular to the axial direction of the rotor shaft.

[0028] At least one end face of the permanent magnet in the axial direction of the rotor shaft has, for example, four corners. That is, at least one end face of the permanent magnet in the axial direction of the rotor shaft is composed of, for example, four sides. At least one end face of the permanent magnet in the axial direction of the rotor shaft is composed of, for example, two long sides and two short sides. The lengths of the two long sides may be the same or different. The two long sides refer to, for example, the two longest sides of the four sides. The two long sides refer to, for example, the longest side and the second longest side of the four sides. The two long sides may be straight or curved. The lengths of the two short sides may be the same or different. The two short sides refer to, for example, the two shortest sides of the four sides. The two short sides refer to, for example, the shortest side and the second shortest side of the four sides. The two short sides may be straight or curved. The angle may be, for example, a right angle, an acute angle, or an obtuse angle when viewed in the axial direction of the rotor shaft. The corners may be, for example, chamfered or rounded. A diagonal angle may be defined, for example, by a first corner and a second corner defined by a second long side and a second short side that are different from the first long side and the first short side that define the first corner.

[0029] The permanent magnet has, for example, substantially the same length as the rotor core in the axial direction of the rotor shaft. However, the permanent magnet may be, for example, longer or shorter than the rotor core in the axial direction of the rotor shaft. In the axial direction of the rotor shaft, at least one end face of the permanent magnet is, for example, located at substantially the same position as the corresponding end face of the rotor core. In the axial direction of the rotor shaft, at least one end face of the permanent magnet is, for example, located on substantially the same plane as the corresponding end face of the rotor core. However, at least one end face of the permanent magnet may protrude or recede from the corresponding end face of the rotor core in the axial direction of the rotor shaft.

[0030] The permanent magnet is accommodated, for example, in a magnet accommodating hole with a gap therebetween when viewed in the axial direction of the rotor shaft. The gap is provided, for example, at least between the inner surface of the magnet accommodating hole and a side surface including a short side of the permanent magnet. The gap is provided, for example, between the magnet accommodating hole and at least one short side of at least one end face of the permanent magnet when viewed in the axial direction of the rotor shaft. The gap may be provided, for example, at least between a side surface including a long side of the permanent magnet and the inner surface of the magnet accommodating hole. The gap is provided, for example, at least between the side surface including the long side of the permanent magnet and the magnet accommodating hole so that the permanent magnet does not fall over when the gap is not filled with resin.

[0031] The arrangement of the multiple permanent magnets is not particularly limited. The multiple permanent magnets are arranged, for example, along the circumferential direction of the rotor shaft. The magnetization direction of the multiple permanent magnets may be, for example, the radial direction or the axial direction of the rotor shaft. The multiple permanent magnets are arranged, for example, such that the orientation of the magnetic poles is alternately reversed. The multiple permanent magnets may be arranged, for example, such that a pair of adjacent permanent magnets constitutes one magnetic pole. The arrangement of the multiple permanent magnets may be, for example, a Halbach array.

[0032] The orientation of the permanent magnet is not particularly limited. When viewed in the axial direction of the rotor shaft, the long side of the permanent magnet may be inclined with respect to the circumferential direction of the rotor shaft (the tangent direction at the center of gravity of the permanent magnet on a virtual circle having a radius from the central axis of the rotor shaft to the center of gravity of the permanent magnet). When viewed in the axial direction of the rotor shaft, the permanent magnet may be arranged such that the distance between the central axis of the rotor shaft and one end of the long side is different from the distance between the central axis of the rotor shaft and the other end of the long side. The multiple permanent magnets may be arranged such that the distance between a pair of permanent magnets constituting one magnetic pole increases or decreases as it moves outward in the radial direction of the rotor shaft.

[0033] The "resin portion" includes, for example, at least one core end face resin portion and an inner core resin portion. The core end face resin portion fixes a permanent magnet, for example, in the axial direction of the rotor shaft. The core end face resin portion may be provided, for example, on one end face of the rotor core, or on both end faces, in the axial direction of the rotor shaft. The shape of the core end face resin portion is not particularly limited. The core end face resin portion has, for example, a ring shape. The core end face resin portion has, for example, a plate-like ring shape. The core end face resin portion includes, for example, a convex portion and a concave portion. The convex portion and the concave portion are arranged, for example, along the circumferential direction of the rotor shaft. The convex portion and the concave portion are arranged, for example, alternately along the circumferential direction of the rotor shaft. The convex portion and the concave portion are, for example, smoothly connected. The convex portion protrudes, for example, outward in the radial direction of the rotor shaft more than the concave portion. The convex portion has, for example, a larger area than the concave portion. In the radial direction of the rotor shaft, the length of the convex portion is, for example, longer than the concave portion.

[0034] The core end surface resin portion covers at least a part of the end surface of the rotor core, for example. The core end surface resin portion covers at least a part of the gap between the magnet accommodating hole and the permanent magnet, for example. The core end surface resin portion covers at least a part of the gap provided between the magnet accommodating hole and one short side of at least one end surface of the permanent magnet, for example. The core end surface resin portion covers a part of the end surface of the permanent magnet so that at least two exposed areas are exposed, for example. One exposed area is, for example, an area including one corner on the end surface of the permanent magnet. The exposed area is, for example, an area within a predetermined range from the corner. The exposed area is, for example, provided so as to include at least a part of the long side and at least a part of the short side on the end surface of the permanent magnet. The area of ​​one exposed area is, for example, smaller than the area of ​​the gap when viewed in the axial direction of the rotor shaft. The area of ​​one exposed area is, for example, smaller than the area of ​​the gap provided between the magnet accommodating hole and one short side when viewed in the axial direction of the rotor shaft.

[0035] One exposed area is provided at an end of one long side, and the other exposed area is provided at an end of the other long side. At least two exposed areas are provided diagonally on an end face of the permanent magnet, for example. At least two exposed areas are provided at both ends of one short side, for example. However, at least two exposed areas may be provided at both ends of one long side, for example. Three or more exposed areas may be provided. One or more additional exposed areas added to the above-mentioned two exposed areas may be provided to include one long side, for example, or may be provided to include one short side. At least two exposed areas are provided to surround the center of gravity of the permanent magnet, for example, when viewed in the axial direction of the rotor shaft. At least two exposed areas are provided so that the permanent magnet can maintain its position in the mold by being supported by the mold, for example, without the resin part being provided. At least two exposed areas are provided so that the mold (lower mold) can support the permanent magnet, for example. The area of ​​the at least two exposed regions is, for example, equal to or greater than the area of ​​the die (lower die) capable of supporting a permanent magnet.

[0036] The internal core resin portion fixes the permanent magnet, for example, in the radial direction of the rotor shaft. The internal core resin portion fixes the permanent magnet, for example, in the circumferential direction of the rotor shaft. The internal core resin portion is formed, for example, by resin filled in the magnet accommodating hole. More specifically, the internal core resin portion is formed, for example, by resin filled in the gap between the magnet accommodating hole and the permanent magnet. The internal core resin portion has, for example, a shape corresponding to the magnet accommodating hole.

[0037] The core internal resin portion includes at least one overlapping region that overlaps with the core end face resin portion, for example, when viewed in the axial direction of the rotor shaft. The core internal resin portion is connected to the core end face resin portion, for example, at the overlapping region. The shape of the overlapping region is not particularly limited. The area of ​​one overlapping region is, for example, larger than the area of ​​one exposed region. However, the area of ​​one overlapping region may be, for example, substantially the same as or smaller than the area of ​​one exposed region. At least one overlapping region overlaps with at least a portion of the magnet accommodating hole, for example, when viewed in the axial direction of the rotor shaft. At least one overlapping region overlaps with at least a portion of the gap between the magnet accommodating hole and the permanent magnet, for example, when viewed in the axial direction of the rotor shaft. At least a portion of the at least one overlapping region is provided so as to be in contact with one short side at the end face of the permanent magnet. At least one overlapping region may be provided so as not to overlap with the magnet accommodating hole, for example. That is, at least one overlapping region may be provided so as to penetrate the rotor core in the axial direction of the rotor shaft and overlap with a through hole different from the magnet accommodating hole, for example, when viewed in the axial direction of the rotor shaft. Effect of the Invention

[0038] According to the present invention, it is possible to easily manufacture a rotor while maintaining or improving the holding force of a permanent magnet. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a cross-sectional view of a rotor according to this embodiment, taken along a plane including the rotor shaft. [Diagram 2] FIG. 2 is a view of the rotor of this embodiment as viewed from the axial direction of the rotor shaft. [Diagram 3] FIG. 3 is a partially enlarged view of FIG. [Figure 4] FIG. 4 is a diagram illustrating a method for manufacturing the rotor of this embodiment. [Diagram 5] FIG. 5 is a diagram showing exposed areas of permanent magnets in a rotor according to a modified example of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, a rotor according to an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example. The present invention should not be construed as being limited in any way by the embodiment described below.

[0041] 1 is a cross-sectional view of a rotor according to this embodiment, cut along a plane including the rotor shaft. The rotor 1 constitutes a motor together with a stator (not shown). The rotor 1 includes a rotor shaft 11, a rotor core 12, a plurality of permanent magnets 13 (hatching omitted), and a resin part 14.

[0042] The rotor shaft 11 has a cylindrical shape. The central axis of the rotor shaft 11 is the center of rotation of the rotor 1.

[0043] The rotor core 12 is fixed to the rotor shaft 11. The rotor core 12 has a cylindrical shape. A rotor shaft through hole 121 is provided in the center of the rotor core 12 when viewed in the axial direction of the rotor shaft 11. The rotor shaft 11 is passed through and fixed in the rotor shaft through hole 121. The rotor core 12 is provided outward of the rotor shaft 11 in the radial direction of the rotor shaft 11. The rotor core 12 is configured to be rotatable together with the rotor shaft 11. The rotor core 12 is configured by laminating electromagnetic steel sheets. The rotor core 12 includes a plurality of magnet accommodating holes 122. The plurality of magnet accommodating holes 122 penetrate the rotor core 12 in the axial direction of the rotor shaft 11. A permanent magnet 13 is accommodated in each of the plurality of magnet accommodating holes 122. The plurality of permanent magnets 13 have a rectangular parallelepiped shape. In the axial direction of the rotor shaft 11, both end faces of the plurality of permanent magnets 13 are located substantially on the same plane as the corresponding end faces of the rotor core 12.

[0044] The resin portion 14 fixes the permanent magnet 13. The resin portion 14 includes two core end face resin portions 141, 142 and an internal core resin portion 143. In the axial direction of the rotor shaft 11, the core end face resin portion 141 is provided on the lower end face of the rotor core 12, and the core end face resin portion 142 is provided on the upper end face of the rotor core 12. The internal core resin portion 143 is provided so as to fill the gap between the magnet accommodating hole 122 and the permanent magnet 13. The internal core resin portion 143 connects the core end face resin portion 141 and the core end face resin portion 142. Note that the two core end face resin portions 141, 142 have the same configuration, so the following description will focus on the core end face resin portion 141.

[0045] 2 is a view of the rotor of this embodiment viewed from the axial direction of the rotor shaft. The multiple magnet accommodating holes 122 are arranged along the circumferential direction of the rotor shaft 11. The multiple magnet accommodating holes 122 have a uniform cross-sectional shape in the axial direction of the rotor shaft 11. A permanent magnet 13 is accommodated in each of the multiple magnet accommodating holes 122. Two adjacent permanent magnets 13 function as a pair of permanent magnets that constitute one magnetic pole. The pair of permanent magnets are arranged in a V-shape with the distance between the permanent magnets widening as it goes radially outward of the rotor shaft 11.

[0046] The core end surface resin part 141 has a ring shape. The core end surface resin part 141 is provided around the rotor core 12 in the circumferential direction. The core end surface resin part 141 has an outer peripheral edge 1411 having a continuous concave and convex shape along the circumferential direction of the rotor shaft 11. The concave portion of the outer peripheral edge 1411 in the core end surface resin part 141 constitutes a recess 1412. The convex portion of the outer peripheral edge 1411 in the core end surface resin part 141 constitutes a convex portion 1413. The convex portion 1413 protrudes outward from the recess in the radial direction of the rotor shaft 11. The convex portion 1413 is provided with a reference portion 1414 that serves as a cutting reference position for adjusting the weight balance of the rotor. The reference portion 1414 is recessed in the axial direction of the rotor shaft 11. A plurality of reference portions 1414 may be provided.

[0047] 3 is a partially enlarged view of FIG. 2. In the figure, the core end face resin part 141 is indicated by a broken line. Four corners C1, C2, C3, and C4 are provided on the end face 131 of the permanent magnet 13. The four corners C1, C2, C3, and C4 are defined by the long sides S1 and S2 and the short sides S3 and S4 constituting the end face 131, respectively. A small gap is provided between the side of the permanent magnet 13 including the long side S1 and the inner surface of the magnet accommodating hole 122, and between the side of the permanent magnet 13 including the long side S2 and the inner surface of the magnet accommodating hole 122. A gap larger than the gap provided between the long sides S1 and S2 and the magnet accommodating hole 122 is provided between the side of the permanent magnet 13 including the short side S3 and the inner surface of the magnet accommodating hole 122, and between the side of the permanent magnet 13 including the short side S4 and the inner surface of the magnet accommodating hole 122. The gaps provided between the long sides S1, S2 and the magnet accommodating hole 122 and the gaps provided between the short sides S3, S4 and the magnet accommodating hole 122 are all connected, thereby forming a gap 1311 between the permanent magnet 13 and the magnet accommodating hole 122.

[0048] The core end surface resin part 141 covers a part of the end surface 131 of the permanent magnet 13 by covering a part of the magnet accommodating hole 122 when viewed in the axial direction of the rotor shaft 11. The core end surface resin part 141 is configured to expose two corners C1 and C3 of the end surface 131 of the permanent magnet 13 by not covering a part of the long side S1 and the short side S3, and a part of the long side S2 and the short side S4 that define the respective corners. The two corners C1 and C3 form diagonal angles on the end surface 131 of the permanent magnet 13. The core end surface resin part 141 exposes the corner C1 by not covering ¼ or less of the long side S1 and ½ or less of the short side S3 that define the corner C1. The same applies to the corner C3. The core end surface resin part 141 is also configured to cover a part of the short side S3 and to cover at least a part of the gap 1311 provided at least between the magnet accommodating hole 122 and the short side S3. The core end surface resin portion 141 is configured so that the exposed area (total exposed area) of the end surface 131 of the permanent magnet 13 is smaller than the area (total area) that the core end surface resin portion 141 covers the magnet accommodating hole 122.

[0049] 4 is a diagram illustrating a method for manufacturing a rotor according to this embodiment. The manufacturing process proceeds in the order of (A), (B), and (C). The manufacturing method includes a preparation process, a placement process, a housing process, and a fixing process.

[0050] Referring to (A), in the preparation step, a mold 2 including an upper mold 21 and a lower mold 22 is prepared. The upper mold 21 and the lower mold 22 are engraved with shapes corresponding to the core end surface resin portions 141, 142, respectively. The lower mold 22 includes a support portion 221 that supports the end surface 131 of the permanent magnet 13.

[0051] In the arrangement step, rotor core 12 is arranged in lower die 22. Rotor core 12 includes magnet accommodating holes 122 that pass through in the axial direction of a rotor shaft through hole to which rotor shaft 11 is attached.

[0052] 2B, in the accommodating step, the permanent magnet 13 is accommodated in the magnet accommodating hole 122 of the rotor core 12 with a gap therebetween, with the end face 131 facing the lower die 22. In this state, the end face 131 of the permanent magnet 13 abuts against and is supported by the support portion 221. Two corners C1, C3 of the end face 131 of the permanent magnet 13 abut against the lower die 22 such that parts of the long sides and short sides defining each corner are supported by the support portion 221. A predetermined range of the end face 131 of the permanent magnet 13 from the corner C1 and a predetermined range of the end face 131 of the permanent magnet 13 abut against and are supported by the support portion 221. Other areas of the end face 131 of the permanent magnet 13 do not abut against the lower die 22.

[0053] Referring to (C), in the fixing step, the upper die 21 is lowered and combined with the lower die 22. Thereafter, resin is injected into the mold 2. The resin is, for example, a thermosetting resin. However, the type of resin is not limited and is appropriately selected as necessary. A gate for injecting the resin is provided in the part of the lower die 22 where the shape of the core end face resin part 141 is engraved. However, the position of the gate is not particularly limited. When the resin is injected from the gate, the resin is first filled in the part of the lower die 22 where the core end face resin part 141 is formed. Next, the resin flows into the gap between the magnet accommodating hole 122 and the permanent magnet 13, and is filled in the part where the core internal resin part 143 is formed. Finally, the resin is filled in the part of the upper die 21 where the core end face resin part 142 is formed. Thereafter, the mold 2 is heated to harden the resin, and the permanent magnet 13 accommodated in the magnet accommodating hole 122 is fixed. As a result, the core end face resin parts 141, 142 and the core internal resin part 143 are integrally molded.

[0054] <Modification> 5 is a diagram showing exposed areas of the permanent magnets in a rotor according to a modified example of this embodiment. In the above embodiment, a configuration has been described in which corners C1 and C2 located diagonally opposite each other are exposed on the end face 131 of the permanent magnet 13. However, the corners to be exposed are not limited to this.

[0055] Referring to (A), for example, corners C1 and C4 may be exposed on end surface 131. Corner C4 is an angle defined by long side S1 and short side S4. Corners C1 and C4 are corners located at both ends of long side S1. In addition, a part of long side S2 different from long side S1 is exposed. That is, area A1 within a predetermined range from corner C1, area A2 within a predetermined range from corner C4, and area A3 within a predetermined range from a part of long side S2 are exposed.

[0056] With reference to (B), for example, corners C1 and C2 may be exposed on end surface 131. Corner C2 is an angle defined by long side S2 and short side S3. Corners C1 and C2 are corners located at both ends of short side S3. In addition, a part of short side S4 different from short side S3 is exposed. That is, area A4 within a predetermined range from corner C1, area A5 within a predetermined range from corner C2, and area A6 within a predetermined range from a part of short side S4 are exposed.

[0057] Referring to (C), for example, corners C1, C3, and C4 may be exposed on end surface 131. Corner C3 is an angle defined by long side S2 and short side S4. Corners C3 and C4 are corners located at both ends of short side S4. That is, a region A7 within a predetermined range from corner C1, a region A8 within a predetermined range from corner C3, and a region A9 within a predetermined range from corner C4 are exposed. Although not shown, all four corners C1, C2, C3, and C4 may be exposed. In short, it is sufficient that at least two corners are exposed on end surface 131 of permanent magnet 13. [Explanation of symbols]

[0058] 1: Rotor 11: Rotor shaft 12: Rotor core 121: Rotor shaft through hole 122: Magnet receiving hole 13: Permanent magnet 131: End face 1311: Gap 14: Resin part 141, 142: Core end surface resin part 1411: Outer edge 1412: Recess 1413: Convex 1414 :Reference part 143: Resin part inside the core 2: Mold 21: Upper mold 22: Lower mold 221: Support part C1-C4: Corner S1, S2: Long side S3, S4: Short side

Claims

1. A rotor shaft; a rotor core including a magnet accommodating hole penetrating in an axial direction of the rotor shaft and fixed to the rotor shaft; a permanent magnet that is accommodated in the magnet accommodating hole with a gap therebetween and has four corners defined by long sides and short sides that constitute at least one end face in the axial direction; A rotor for a motor comprising: a resin portion to which the permanent magnet is fixed, The resin portion is a core end surface resin portion provided on at least one end surface of the rotor core in the axial direction; a core inner resin portion provided to fill the gap and connected to the core end surface resin portion, The core end surface resin portion is A rotor configured such that, when viewed in the axial direction, a portion of the end face of the permanent magnet is covered by covering a portion of the magnet accommodating hole, and at least two corners of the end face of the permanent magnet are exposed by leaving uncovered portions of the long sides and short sides that define each corner.

2. 2. The rotor of claim 1, The core end surface resin portion is A rotor configured such that, when viewed in the axial direction, at least two diagonally opposite corners on the end face of the permanent magnet are exposed by not covering a portion of the long and short sides that define each corner.

3. A rotor according to claim 1 or 2, The core end surface resin portion is A rotor configured so that an exposed area of ​​an end face of the permanent magnet is smaller than an area where the core end face resin portion covers the magnet accommodating hole.

4. A rotor according to any one of claims 1 to 3, The core end surface resin portion is The rotor is configured to expose the at least two corners by leaving uncovered no more than ¼ of the long sides and no more than ½ of the short sides defining each corner.

5. A rotor according to any one of claims 1 to 4, When viewed in the axial direction, the gap is provided at least between an inner surface of the magnet accommodating hole and at least one short side of an end face of the permanent magnet, The core end surface resin portion is A rotor configured to cover a portion of the one short side and to cover at least a portion of the gap when viewed in the axial direction.

6. A rotor according to any one of claims 1 to 5, The core end surface resin portion is a ring-shaped groove provided on an end surface of the rotor core in a circumferential direction of the rotor core; A rotor having an outer peripheral edge with a continuous uneven shape along the circumferential direction of the rotor shaft.

7. A rotor according to any one of claims 1 to 6, The core end surface resin portion is A rotor including a reference portion on an end surface in the axial direction, the reference portion being a cutting reference position for adjusting the weight balance of the rotor.

8. Preparing a mold including an upper mold and a lower mold; a step of disposing a rotor core in the lower die, the rotor core including a magnet accommodating hole passing through the rotor shaft in an axial direction of a rotor shaft through hole for attaching the rotor shaft; a step of accommodating a permanent magnet, at least one of whose end faces in the axial direction has four corners defined by long sides and short sides that constitute the end face, in the magnet accommodating hole of the rotor core arranged in the lower die with the end face facing the lower die, with a gap therebetween; a step of combining the upper die with the lower die, injecting a resin into the die, and fixing the permanent magnet accommodated in the magnet accommodating hole, In the step of preparing the mold, preparing a lower die including a support portion for supporting an end face of the permanent magnet, the lower die being engraved with a shape of a core end face resin portion to be provided on the end face of the rotor core that comes into contact with the lower die; In the step of fixing the permanent magnet, The resin is injected into the mold to fill the magnet accommodating hole through the gap, and an inner-core resin portion that is provided in the rotor so as to fill the gap and is connected to the core end surface resin portion is molded integrally with the core end surface resin portion; In the step of housing the permanent magnet, A rotor manufacturing method in which, when viewed in the axial direction, a space is provided between a portion of the magnet accommodating hole and the lower mold so that a portion of the end face of the permanent magnet is not abutted against the lower mold, while at least two corners of the end face of the permanent magnet are abutted against the lower mold so that portions of the long sides and short sides defining each corner are supported by the support portions.

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