US-12620853-B2 - Rotating electric machine and method for manufacturing rotor

US12620853B2US 12620853 B2US12620853 B2US 12620853B2US-12620853-B2

Abstract

A rotor constituting a rotating electric machine includes a rotating shaft and a permanent magnet. A sleeve covering the outer surface of the permanent magnet is attached to the rotating shaft. A resin coating layer is formed on an outer circumferential wall of the sleeve. The resin coating layer includes a base portion and a plurality of ridges formed on the outer circumferential wall of the base portion. A riblet recessed relative to the plurality of ridges is formed between the plurality of ridges.

Inventors

Yuji Ono
Keiji Tada
Tsutomu Yoshino
Kimiaki Nakamura
Kaoru TOMIOKA
Tomoya Otani
Koichi Oku

Assignees

HONDA MOTOR CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20230607
Priority Date: 20220609

Claims (8)

1 . A method of manufacturing a rotor that includes a rotating shaft and a permanent magnet held on the rotating shaft and is surrounded by a stator in a rotating electric machine, the method comprising: covering an outer surface of the permanent magnet with a sleeve made of a carbon fiber reinforced polymer to attach the sleeve; coating an outer circumferential wall of the sleeve with a resin coating layer; and forming, in the resin coating layer, a base portion constituted by a cylindrical body covering the outer circumferential wall of the sleeve and a ridge structure protruding from an outer circumferential wall of the base portion, by processing and removing a part of an outer circumferential wall of the resin coating layer, wherein in the forming of the base portion and the ridge structure, by machining and removing the part of the outer circumferential wall of the resin coating layer the ridge structure is provided as one or a plurality of convex portions forming a plurality of ridges that extend in parallel to each other, thereby forming a riblet recessed relative to the plurality of ridges, and wherein a sum of a thickness of the base portion formed by machining the resin coating layer and a thickness of each of the plurality of ridges is smaller than a pre-machining thickness of the resin coating layer.
2 . The method of manufacturing the rotor according to claim 1 , wherein in the forming of the base portion and the ridge structure, the plurality of ridges are formed so as to extend in a direction intersecting an axial direction of the rotating shaft at an angle of 45° to 90°.
3 . The method of manufacturing the rotor according to claim 1 , wherein when a height of each of the plurality of ridges is H and a pitch between two adjacent ridges among the plurality of ridges is S, the plurality of ridges are formed so as to satisfy a following equation in the forming of the base portion and the ridge structure: H=0.5S.
4 . The method of manufacturing the rotor according to claim 1 , wherein when the plurality of ridges are cut in a direction orthogonal to an extending direction of the plurality of ridges, the plurality of ridges are formed in the forming of the base portion and the ridge structure, in a manner so that a cross-sectional shape of each of the plurality of ridges is a triangle.
5 . The method of manufacturing the rotor according to claim 4 , wherein when the plurality of ridges are cut in the direction orthogonal to the extending direction of the plurality of ridges, the plurality of ridges are formed in the forming of the base portion and the ridge structure, in a manner so that a top portion in a cross section of each of the ridges has an angle of 30° to 90°, the top portion protruding most outward in a diametrical direction of the rotating shaft.
6 . The method of manufacturing the rotor according to claim 1 , wherein the coating with the resin coating layer is performed to form the resin coating layer by using, as a base material resin of the resin coating layer, a resin that causes less wear of a cutting tool when machining is performed on the base material resin compared to wear of the cutting tool when machining is performed on the carbon fiber reinforced polymer under a same machining condition.
7 . The method of manufacturing the rotor according to claim 6 , wherein an epoxy-based resin or a paraxylene-based resin is used as the base material resin.
8 . The method of manufacturing the rotor according to claim 1 , wherein in the forming of the base portion and the ridge structure, a cutting tool having a shape that is capable of forming the base portion and the plurality of ridges is provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-093531 filed on Jun. 9, 2022, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a rotating electric machine including a rotor and a stator. The present invention also relates to a method of manufacturing a rotor constituting a rotating electric machine. Description of the Related Art A rotating electric machine including a rotor and a stator disposed outside of the rotor is known. In this case, the rotor has permanent magnets provided on an outer circumferential wall of the rotating shaft. To prevent the permanent magnets from falling off the rotating shaft, a sleeve is attached to the rotating shaft. The sleeve covers outer surfaces of the permanent magnets. The sleeve is formed of a carbon fiber reinforced polymer as described in, for example, JP 2020-175603 A. A predetermined clearance is formed between the sleeve and the stator. Therefore, an air layer is interposed between the sleeve and the stator. When the rotating shaft rotates in this state, an air flow is generated around the sleeve. In the case that a rotational speed of the rotating shaft is low, the air flow is laminar. On the other hand, in the case of an aircraft or the like, it is assumed that a rotating shaft is rotated at a high speed. In this case, the air flow becomes turbulent. Under this condition, frictional resistance of the sleeve with respect to the air layer increases. As a result, so-called windage loss occurs. If the permanent magnet is heated due to the windage loss, the energy conversion efficiency of the rotating electric machine decreases. In order to reduce windage loss, riblets may be formed on the outer circumferential wall of the sleeve. For example, in the prior art described in JP 2020-175603 A, a prepreg is deformed into a cylindrical shape to obtain a sleeve, and then a transfer film is wound around an outer circumferential wall of the sleeve. A convex pattern is formed in advance on the transfer film, and the convex pattern is transferred to the outer circumferential wall of the sleeve to form the riblets on the outer circumferential wall. Thereafter, the sleeve is thermally cured and the transfer film is removed from the sleeve. JP H11-150896 A describes that an armoring made of a non-magnetic material is attached to an outer circumferential surface of a rotor. Annular convex portions for promoting heat dissipation are formed on the outer circumferential wall of the armoring. The annular concave portions recessed relative to the annular convex portions are grooves. According to the description of JP H11-150896 A, an increase in windage loss is suppressed by the grooves. Titanium is exemplified as the material of the armoring. SUMMARY OF THE INVENTION It is not easy to form a fine structure in a prepreg with high dimensional accuracy. Therefore, even if fine irregularities are formed on the transfer film, it is not easy to transfer the fine irregularities to the prepreg. For this reason, it is difficult to obtain a sleeve made of a carbon fiber reinforced polymer and having fine grooves. JP H11-150896 A describes depositing and fixing fine particles by thermal spraying or cold spraying in order to obtain an armoring having fine irregularities formed on the outer circumferential wall. However, based on such a method, it is not easy to obtain an armoring having rigidity enough to hold the permanent magnets. When a cylindrical body made of a metal such as titanium is used as an armoring, rigidity can be secured, but it is not easy to form fine irregularities on titanium or the like by machining or the like. Further, in this case, since the weight of the armoring is large, the weight of the rotor increases. The present invention has the object of solving the aforementioned problems. According to an embodiment of the present invention, there is provided a rotating electric machine including a rotor and a stator, the rotor including a rotating shaft and a permanent magnet held on the rotating shaft, and the stator including an electromagnetic coil surrounding the permanent magnet, wherein the rotor includes a sleeve covering an outer surface of the permanent magnet on the rotating shaft and being spaced apart from the stator by a predetermined distance, and a resin coating layer provided on an outer circumferential wall of the sleeve, and wherein the sleeve is made of a carbon fiber reinforced polymer, the resin coating layer includes a base portion covering the outer circumferential wall of the sleeve and a ridge structure protruding from an outer circumferential wall of the base portion, the ridge structure includes one or a plurality of convex portions forming a plurality of ridges extending parallel to each other, and a riblet recessed relative to the plurality of ridges is formed