Rotor and method of manufacturing the rotor

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 a stator and a rotor. For example, the stator is equipped with coils that generate a magnetic field when a current is passed through them. The rotor is equipped with permanent magnets that react with the magnetic field generated by the coils. The rotor rotates when the permanent magnets react with the magnetic field generated by the coils. There are various methods for attaching permanent magnets to the rotor. One known attachment method is to embed the permanent magnets inside the rotor core using 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 portion that holds the permanent magnet in the molded rotor. A roughly annular rotor core clamping resin portion is provided on both axial end faces of the rotor core so as to follow the outer periphery of the rotor core. The rotor core clamping resin portion is provided so as to cover both end ends of the opening of the magnet accommodating hole. No rotor core clamping resin portion is provided in the center of the opening of the magnet accommodating hole, leaving the center portion of the permanent magnet exposed.

[0004] This rotor is manufactured as follows: First, the rotor core is placed in a lower mold engraved with the shape of one of the rotor core clamping resin portions. 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 portion is placed. The upper and lower molds contact the centers of the top and bottom surfaces of the permanent magnet, sandwiching and positioning it. This contact area corresponds to the exposed portion of the permanent magnet in the molded rotor. Next, resin is injected into the mold, and the two rotor core clamping resin portions and the magnet fixing resin portion are injection molded. Within the mold, the space for molding the two rotor core clamping resin portions and the space for molding the magnet fixing resin portion are connected via both ends of the magnet accommodating hole. Therefore, the two rotor core clamping resin portions and the magnet fixing resin portion are molded integrally. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-142038 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the rotor of Patent Document 1, two rotor core clamping resin portions and a magnet fixing resin portion are molded simultaneously, thereby improving rotor manufacturing efficiency, reducing manufacturing costs, and reducing rotor weight. Furthermore, in the rotor manufacturing method of Patent Document 1, the central portions of the upper and lower surfaces of the permanent magnet are abutted against a mold, sandwiching and positioning the permanent magnet between them. This method eliminates the need for positioning pins for the permanent magnet, and therefore does not require drilling holes for positioning pins in the rotor core clamping resin portion. As a result, even if the portions that hold the permanent magnets, such as the two rotor core clamping resin portions and the magnet fixing resin portion, are made of resin, the holding force of the permanent magnets can be maintained or improved. The inventors have investigated a method different from Patent Document 1 that facilitates rotor manufacturing while maintaining or improving the holding force of the permanent magnets.

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

[0008] (1) The rotor of the present invention is a rotor for a motor, comprising: 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 and short sides that respectively constitute the end face on at least one axial end face; and a resin portion that secures the permanent magnet. The resin portion includes a core end-face resin portion provided on at least one axial end face of the rotor core, and an internal-core resin portion that is provided to fill the gap and connect to the core end-face resin portion. The core end-face resin portion is configured to cover a portion of the magnet accommodating hole to cover a portion of the end face of the permanent magnet, and to expose at least two corners of the end face of the permanent magnet by not covering a portion of the long 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 portions are formed by the contact between the permanent magnet and a mold when the resin portion is formed. That is, in the manufacturing process, when the permanent magnet is placed in the magnet receiving hole before molding the resin portion, at least two exposed portions on the end face (lower surface) of the permanent magnet are supported by the lower mold. For example, two diagonally opposite corners on the end face of the permanent magnet may be supported by the mold, or both corners of one long side of the end face and a portion of the other long side may be supported by the mold. This allows the mold to support the permanent magnet even with a small support area, facilitating molding of the resin portion. Furthermore, because the exposed area of ​​the permanent magnet can be reduced in the axial view, the area of ​​the core end face resin portion can be increased, and the holding force of the permanent magnet is less likely to decrease even if the portion holding the permanent magnet is made of resin. Therefore, the rotor described above facilitates rotor manufacturing 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 and short sides that define each corner.

[0011] In the rotor (2) above, both ends of a diagonal line at the end face of the permanent magnet are supported by the mold. Because both ends of the diagonal line, which is the longest imaginary line at the end face of the permanent magnet, are supported by the mold, the mold can support the permanent magnet even if the exposed area of ​​the permanent magnet is reduced. Therefore, with this rotor, 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 the exposed area of ​​the end face of the permanent magnet is smaller than the area that the core end surface resin portion covers the magnet accommodating hole.

[0013] In the rotor described above in (3), the exposed area of ​​the permanent magnet can be reduced, allowing the area of ​​the core end surface resin portion to be increased. Therefore, the rotor described above can facilitate rotor manufacture while maintaining or improving the holding force of the permanent magnet. The core end surface resin portion may be configured so that the exposed area of ​​the end face of the permanent magnet is smaller than the area where the core end surface 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 more than 1 / 4 of the long sides and less than 1 / 2 of the short sides that define each corner.

[0015] In the rotor of (4) above, the exposed area of ​​the permanent magnet can be reduced, allowing the area of ​​the core end surface resin portion to be increased, thereby facilitating the manufacture of the rotor while maintaining or improving the holding force of the permanent magnet.

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

[0017] In the rotor described above in (5), the resin portion within the core, formed by the resin filling the gaps adjacent to the short sides, primarily serves to secure the permanent magnets. Therefore, for example, the gap between the long sides and the inner surface of the magnet accommodating hole can be reduced when viewed in the axial direction. By reducing the gaps adjacent to the long sides, the orientation of the permanent magnets is more easily maintained when the permanent magnets are accommodated in the magnet accommodating holes without the resin portion present. Therefore, the rotor described above can be easily manufactured while maintaining or improving the holding force of the permanent magnets.

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

[0019] In the rotor (6) described above, for example, the portions requiring strength, such as the connection between the core end-face resin portion and the core internal resin portion, can be made convex in the radial direction of the rotor shaft, while the portions not requiring as much strength can be made concave in the radial direction. In other words, more resin is supplied to the portions requiring strength, and less resin is supplied to the portions not requiring as much strength. Therefore, with 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 rotor's weight.

[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 being manufactured, the rotor is adjusted for rotational balance before being completed as a finished product. The rotational balance is adjusted, for example, by cutting a portion of the rotor's core end surface resin portion. In the rotor described in (7) above, a reference portion is provided as a cutting reference position. Therefore, with this 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 whose core end surface resin portion has an uneven outer periphery, by providing a reference portion in the convex portion 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 includes the steps of: preparing a mold including an upper mold and a lower mold; placing a rotor core having magnet accommodating holes axially penetrating a rotor shaft through-hole for mounting the rotor shaft in the lower mold; placing permanent magnets, each having four corners defined by long and short sides constituting an end face on at least one axial end face, facing the lower mold and inserting them into the magnet accommodating holes of the rotor core arranged in the lower mold with a gap; and combining the upper mold with the lower mold, injecting resin into the mold to fix the permanent magnets in the magnet accommodating holes. In the mold preparation step, a lower mold is prepared, which includes a support for supporting the end faces of the permanent magnets and is engraved with the shape of a core end-face resin portion to be provided on the end face of the rotor core that abuts against the lower mold. In the permanent magnet fixation step, resin is injected into the mold to fill the magnet accommodating holes through the gap, thereby forming an internal-core resin portion in the rotor that fills the gap and is connected to the core end-face resin portion, integrally with the core end-face resin portion. In the process of accommodating the permanent magnet, a space is provided between a part of the magnet accommodating hole and the lower mold when viewed in the axial direction, so that a part of the end face of the permanent magnet does not abut 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] Hereinafter, each configuration and terminology of the present invention will be explained.

[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, the rotation axis of the rotor. When the rotor shaft rotates, for example, the rotor rotates. The rotor shaft corresponds to, for example, the 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 multiple 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, on both end surfaces of the rotor shaft in the axial direction. The rotor shaft through-hole is, for example, arranged so 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 is open, for example, to both end surfaces 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 housing hole. When multiple magnet housing holes are provided, multiple permanent magnets are also provided. Each of the multiple permanent magnets is housed in a corresponding magnet housing 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 angles may be, for example, right angles, acute angles, or obtuse angles when viewed in the axial direction of the rotor shaft. The corners may be, for example, chamfered or rounded. A diagonal angle is 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] For example, the permanent magnet has substantially the same length as the rotor core in the axial direction of the rotor shaft. However, the permanent magnet may be 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 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 located at 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 the magnet accommodating hole with a gap therebetween when viewed in the axial direction of the rotor shaft. The gap is provided, for example, between the inner surface of the magnet accommodating hole and a side surface including a short side of the permanent magnet. When viewed in the axial direction of the rotor shaft, 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. For example, the gap may be provided at least between the side surface including the long side of the permanent magnet and the inner surface of the magnet accommodating hole. For example, the gap is provided 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 tip 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 may be 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 may be arranged, for example, so that the orientation of the magnetic poles alternates. The multiple permanent magnets may be arranged, for example, so that a pair of adjacent permanent magnets constitutes one magnetic pole. The multiple permanent magnets may be arranged, for example, in a Halbach array.

[0032] The orientation of the permanent magnet is not particularly limited. When viewed in the axial direction of the rotor shaft, for example, 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 an imaginary circle whose radius is 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, for example, the permanent magnet may be arranged so 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. For example, the multiple permanent magnets may be arranged so that the distance between a pair of permanent magnets that constitute one magnetic pole increases or decreases as the distance increases radially outward along the rotor shaft.

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

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

[0035] For example, one exposed area is provided at the end of one long side, and the other exposed area is provided at the end of the other long side. At least two exposed areas are provided, for example, diagonally on the end face of the permanent magnet. At least two exposed areas are provided, for example, at both ends of one short side. However, at least two exposed areas may also be provided, for example, 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 two exposed areas described above may be provided to include, for example, one long side or one short side. For example, the at least two exposed areas are provided so as to surround the center of gravity of the permanent magnet when viewed in the axial direction of the rotor shaft. For example, the at least two exposed areas are provided so that the permanent magnet can maintain its position within the mold when the at least two exposed areas are supported by a mold without a resin portion. For example, the at least two exposed areas are provided so that the mold (lower mold) can support the permanent magnet. The area of ​​the at least two exposed regions is, for example, equal to or greater than the area of ​​the mold (lower mold) that can support 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 into the magnet accommodating hole. More specifically, the internal core resin portion is formed, for example, by resin filled into 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 internal-core 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 internal-core 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 arranged to contact one short side of the end face of the permanent magnet. At least one overlapping region may be arranged so as not to overlap with the magnet accommodating hole, for example. That is, at least one overlapping region may be arranged so as to overlap with a through hole that penetrates the rotor core in the axial direction of the rotor shaft and is different from the magnet accommodating hole, for example, when viewed in the axial direction of the rotor shaft. [Effects 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 explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a cross-sectional view of the rotor of this embodiment taken along a plane including the rotor shaft. [Figure 2] FIG. 2 is a view of the rotor of this embodiment as seen from the axial direction of the rotor shaft. [Figure 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. [Figure 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 INVENTION

[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, taken 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 formed 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 positioned substantially flush with 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 as seen 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 spacing between the permanent magnets widening as they extend radially outward around the rotor shaft 11.

[0046] The core end surface resin portion 141 has an annular shape. The core end surface resin portion 141 is provided around the circumferential direction of the rotor core 12. The core end surface resin portion 141 has an outer peripheral edge 1411 that is continuously uneven along the circumferential direction of the rotor shaft 11. The concave portion of the outer peripheral edge 1411 of the core end surface resin portion 141 forms a recess 1412. The convex portion of the outer peripheral edge 1411 of the core end surface resin portion 141 forms a protrusion 1413. The protrusion 1413 protrudes outward from the recess in the radial direction of the rotor shaft 11. The protrusion 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. Multiple reference portions 1414 may be provided.

[0047] FIG. 3 is a partially enlarged view of FIG. 2. In the figure, the core end-face resin portion 141 is indicated by dashed lines. 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 that constitute the end face 131, respectively. Small gaps are provided between the side face of the permanent magnet 13, including the long side S1, and the inner surface of the magnet accommodating hole 122, and between the side face of the permanent magnet 13, including the long side S2, and the inner surface of the magnet accommodating hole 122. Larger gaps are provided between the side face of the permanent magnet 13, including the short side S3, and the inner surface of the magnet accommodating hole 122, and between the side face of the permanent magnet 13, including the short side S4, and the inner surface of the magnet accommodating hole 122, than the gaps provided between the long sides S1 and S2 and the magnet accommodating hole 122. The gaps between the long sides S1, S2 and the magnet accommodating hole 122 and the gaps between the short sides S3, S4 and the magnet accommodating hole 122 are all connected, and these form the gap 1311 between the permanent magnet 13 and the magnet accommodating hole 122.

[0048] When viewed in the axial direction of the rotor shaft 11, the core end-face resin portion 141 covers a portion of the magnet accommodating hole 122, thereby covering a portion of the end face 131 of the permanent magnet 13. The core end-face resin portion 141 is configured to expose two corners C1 and C3 of the end face 131 of the permanent magnet 13 by not covering a portion of the long side S1 and short side S3, and a portion of the long side S2 and short side S4, which define the respective corners. The two corners C1 and C3 form diagonal angles on the end face 131 of the permanent magnet 13. The core end-face resin portion 141 exposes corner C1 by not covering a quarter or less of the long side S1 and a half or less of the short side S3, which define corner C1. The same applies to corner C3. The core end-face resin portion 141 is also configured to cover a portion of the short side S3 and at least a portion of the gap 1311 provided 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 over the magnet accommodating hole 122.

[0049] 4A to 4C are diagrams 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, an arrangement 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. Shapes corresponding to the core end surface resin portions 141, 142 are engraved in the upper mold 21 and the lower mold 22, respectively. The lower mold 22 includes a support portion 221 that supports the end surface 131 of the permanent magnet 13.

[0051] In the placement step, rotor core 12 is placed in lower mold 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] Referring to (B), in the accommodating step, the permanent magnet 13 is accommodated in the magnet accommodating hole 122 of the rotor core 12 with the end face 131 facing the lower mold 22, with a gap therebetween. 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 mold 22 so that parts of the long sides and short sides that define each corner are supported by the support portion 221. A predetermined range area of ​​the end face 131 of the permanent magnet 13 from the corner C1 and a predetermined range area 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 mold 22.

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

[0054] <Modification> 5 is a diagram showing exposed areas of the permanent magnet in a rotor according to a modified example of this embodiment. In the above-described embodiment, a configuration has been described in which diagonally opposite corners C1 and C2 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 portion of long side S2, which is different from long side S1, is exposed. That is, a predetermined area A1 from corner C1, a predetermined area A2 from corner C4, and a predetermined area A3 from a portion of long side S2 are exposed.

[0056] Referring 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 portion of short side S4 different from short side S3 is exposed. That is, a region A4 within a predetermined range from corner C1, a region A5 within a predetermined range from corner C2, and a region A6 within a predetermined range from a portion 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 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 predetermined area A7 from corner C1, a predetermined area A8 from corner C3, and a predetermined area A9 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 part 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 that penetrates the rotor shaft in the axial direction and is 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 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; an inner-core resin portion provided to fill the gap and connected to the core end surface resin portion, and molded using a mold; The core end surface resin portion is 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 not covering a portion of a long side and a portion of a short side that define each corner, The rotor, wherein the at least two exposed corners are formed by contacting the resin portion with the mold when molding the resin portion.

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 leaving uncovered a portion of the long side and a portion of the short side defining each corner.

3. 3. The rotor according to claim 1 or 2, The core end surface resin portion is The rotor is configured so 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 magnet accommodating hole.

4. 2. The rotor of claim 1, The core end surface resin portion is The rotor is configured to expose the at least two corners by leaving uncovered not more than ¼ of the long sides and not more than ½ of the short sides defining each corner.

5. 2. The rotor of claim 1, 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 at least a portion of the gap when viewed in the axial direction.

6. 2. The rotor of claim 1, The core end surface resin portion is a ring-shaped rotor core 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 concave-convex shape along the circumferential direction of the rotor shaft.

7. 2. The rotor of claim 1, The core end surface resin portion is The rotor includes a reference portion on an end surface in the axial direction, the reference portion serving as 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 placing a rotor core in the lower mold, the rotor core including magnet accommodating holes that pass through in the axial direction of a rotor shaft through hole for attaching a rotor shaft; a step of accommodating a permanent magnet, the permanent magnet having four corners defined by long sides and short sides on at least one end face in the axial direction, with the end face facing the lower mold and spaced apart from one another in the magnet accommodating hole of the rotor core arranged in the lower mold; combining the upper mold with the lower mold, injecting resin into the mold, and fixing the permanent magnets accommodated in the magnet accommodating holes, In the step of preparing the mold, a lower mold including a support portion for supporting an end face of the permanent magnet, the lower mold 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 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 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 method for manufacturing a rotor, 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 does not abut 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 portion of the long side and a portion of the short side defining each corner are supported by the support portion.

Images