Rotor manufacturing method

Abstract

To provide a rotary electric machine which reduces windage loss and thereby improves energy conversion efficiency.SOLUTION: A rotor 12 constituting a rotary electric machine 10 has a rotary shaft 18, and a permanent magnet 30. On the rotary shaft 18, a sleeve 32 covering the outer surface of the permanent magnet 30 is mounted. On the outer peripheral wall of the sleeve 32, a resin coating layer 40 is provided. The resin coating layer 40 has a base 42, and a plurality of projections 44 formed on the outer peripheral wall of the base 42. Between the plurality of projections 44, riblets 46 which are recessed relatively to the plurality of projections 44 are formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine including a rotor and a stator, and also to a method for manufacturing a rotor that constitutes a rotating electric machine. [Background technology]

[0002] A rotating electric machine is known that includes a rotor and a stator disposed on the outer periphery of the rotor. In this case, the rotor has permanent magnets provided on the outer periphery wall of a rotating shaft. To prevent the permanent magnets from falling off the rotating shaft, a sleeve is attached to the rotating shaft. The sleeve covers the outer surface of the permanent magnet. The sleeve is formed from carbon fiber reinforced resin, for example, as described in Patent Document 1.

[0003] A certain 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, airflow occurs around the sleeve. When the rotating shaft rotates at a low speed, the airflow is laminar. In contrast, in aircraft and other aircraft, the rotating shaft is expected to rotate at high speeds. In this case, the airflow becomes turbulent. Under these conditions, the frictional resistance of the sleeve against the air layer increases. As a result, so-called windage loss occurs. When the permanent magnets become heated due to this windage loss, the energy conversion efficiency of the rotating electric machine decreases.

[0004] In order to reduce windage loss, riblets may be formed on the outer peripheral wall of a sleeve. For example, in the technology described in Patent Document 1, a prepreg is deformed into a cylindrical shape to obtain a sleeve, and then a transfer film is wrapped around the outer peripheral wall of the sleeve. A convex pattern is formed in advance on the transfer film, and the convex pattern is transferred to the outer peripheral wall of the sleeve, thereby forming riblets on the outer peripheral wall. The sleeve is then heated and cured, and the transfer film is removed from the sleeve.

[0005] Patent Document 2 describes that an armor made of a non-magnetic material is attached to the outer peripheral surface of the rotor. An annular protrusion is formed on the outer peripheral wall of the armor to promote heat dissipation. An annular recess that is recessed relative to the annular protrusion is a groove. According to the description in Patent Document 2, the groove suppresses an increase in windage loss. Titanium is exemplified as a material for the armor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-175603 [Patent Document 2] Japanese Patent Application Publication No. 11-150896 Summary of the Invention [Problem to be solved by the invention]

[0007] It is not easy to form a microstructure with high dimensional accuracy in a prepreg. Therefore, even if a fine irregularity is formed on a transfer film, it is not easy to transfer the fine irregularity to a prepreg. For these reasons, it is difficult to obtain a sleeve made of carbon fiber reinforced resin and having fine grooves.

[0008] Patent Document 2 describes the deposition and fixation of fine particles by thermal spraying or cold spraying to obtain an armor with fine irregularities formed on the outer peripheral wall. However, it is not easy to obtain an armor with sufficient rigidity to hold a permanent magnet using such a method. While rigidity can be ensured by using a cylindrical body made of a metal such as titanium as the armor, it is not easy to form fine irregularities by machining or the like titanium. Furthermore, in this case, the weight of the armor is large, which increases the weight of the rotor.

[0009] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0010] According to one embodiment of the present invention, there is provided a rotating electric machine comprising a rotor and a stator, wherein the rotor has a rotating shaft and a permanent magnet held by the rotating shaft, and the stator has an electromagnetic coil surrounding the permanent magnet, wherein the rotor comprises a sleeve that covers the outer surface of the permanent magnet on the rotating shaft and is spaced a predetermined distance from the stator, and a resin coating layer provided on the outer peripheral wall of the sleeve, wherein the sleeve is made of carbon fiber reinforced resin, and the resin coating layer has a base that covers the outer peripheral wall of the sleeve and a protrusion structure that protrudes from the outer peripheral wall of the base, and the protrusion structure consists of one or more convex portions that form a plurality of protrusions extending parallel to each other, and riblets that are recessed relative to the plurality of protrusions are formed between the plurality of protrusions.

[0011] According to another embodiment of the present invention, there is provided a method for manufacturing a rotor having a rotating shaft and a permanent magnet held by the rotating shaft and surrounded by a stator in a rotating electric machine, the method comprising: a sleeve attachment process for covering the outer surface of the permanent magnet with a sleeve made of carbon fiber reinforced resin; a resin coating process for coating the outer peripheral wall of the sleeve with a resin coating layer; and a protrusion forming process for removing a portion of the outer peripheral wall of the resin coating layer by processing to form in the resin coating layer a base that covers the outer peripheral wall of the sleeve and a protrusion structure that protrudes from the outer peripheral wall of the base, wherein in the protrusion forming process, the protrusion structure is provided as one or more convex portions that form multiple protrusions extending parallel to each other, thereby forming riblets that are recessed relatively to the multiple protrusions. [Effects of the Invention]

[0012] Since it is difficult to process a sleeve made of carbon fiber reinforced resin, it is not easy to form riblets (or protrusions) on the outer peripheral wall of the sleeve. In contrast, in the present invention, riblets are formed in a resin coating layer that covers the outer peripheral wall of the sleeve. Because the resin coating layer is separate from the sleeve, there is no need to perform processing such as cutting on the sleeve. Therefore, damage such as cracks to the sleeve is avoided.

[0013] Riblets can be easily formed by forming protrusions on the resin coating layer through machining or other processes. Furthermore, the resin coating layer is made of a resin that is lighter than metals, etc. This prevents the rotor from becoming too heavy.

[0014] The riblets reduce the turbulent vortices that occur around the rotor, even when the rotor rotates at high speed. This reduces turbulent friction viscosity and suppresses the generation of tiller vortices. For these reasons, windage loss can be reduced. As a result, heating of the permanent magnets is suppressed. Therefore, a decrease in the magnetic force of the permanent magnets is avoided, and the energy conversion efficiency of the rotating electric machine is sufficiently increased. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view of a rotating electric machine according to an embodiment of the present invention, viewed along the axial direction. [Figure 2] FIG. 2 is a schematic front view of the rotor as viewed from the axial direction. [Figure 3] FIG. 3 is an example of an enlarged view of a main part of the resin coating layer when viewed along the axial direction of the rotating shaft of the rotor. [Figure 4] FIG. 4 is another example of an enlarged view of a main part of the resin coating layer when viewed along the axial direction of the rotating shaft of the rotor. [Figure 5] FIG. 5 is another example of an enlarged view of a main part of the resin coating layer when viewed along the axial direction of the rotating shaft of the rotor. [Figure 6] FIG. 6 is an example of a cross-sectional view of a protrusion formed on a resin coating layer, as viewed from a direction perpendicular to the extending direction of the protrusion. [Figure 7] FIG. 7 is another example of a cross-sectional view of a protrusion formed on a resin coating layer, as viewed from a direction perpendicular to the extending direction of the protrusion. [Figure 8] FIG. 8 is another example of a cross-sectional view of a protrusion formed on a resin coating layer, as viewed from a direction perpendicular to the extending direction of the protrusion. [Figure 9] FIG. 9 is yet another example of a cross-sectional view of a protrusion formed on a resin coating layer, as viewed from a direction perpendicular to the extending direction of the protrusion. [Figure 10] FIG. 10 is yet another example of a cross-sectional view of a protrusion formed on a resin coating layer, as viewed from a direction perpendicular to the extending direction of the protrusion. [Figure 11] FIG. 11 is a schematic flow diagram of a method for manufacturing a rotor according to an embodiment of the present invention. [Figure 12] FIG. 12 is a cross-sectional view of a main part showing a state in which a resin coating layer is formed on the outer peripheral wall of the sleeve. [Figure 13] FIG. 13 is a cross-sectional view of a main part showing a state in which protrusions are formed on a resin coating layer. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1 to 13, some components may be exaggerated to facilitate understanding, and therefore, the actual scale of each component is not shown in FIGS.

[0017] 1 is a schematic cross-sectional view of a rotating electrical machine 10 according to this embodiment, viewed along an axial direction (described later). The rotating electrical machine 10 includes a rotor 12 and a stator 14. Most of the rotor 12 and the stator 14 are housed in a casing 16.

[0018] The rotor 12 has a rotating shaft 18. The rotating shaft 18 is a cylindrical body having a first small diameter portion 20, a large diameter portion 22, and a second small diameter portion 24. The centers of the first small diameter portion 20 and the second small diameter portion 24 coincide with the center of the large diameter portion 22. The direction in which the first small diameter portion 20, the large diameter portion 22, and the second small diameter portion 24 are aligned is the extension direction of the rotating shaft 18. Hereinafter, a line passing through the center of each of the first small diameter portion 20, the large diameter portion 22, and the second small diameter portion 24 and extending along the extension direction of the rotating shaft 18 will be referred to as the axis L, and a direction parallel to the axis L will sometimes be referred to as the axial direction. The axial direction is the direction of arrow X in FIG. 1. The diameters of the first small diameter portion 20, the large diameter portion 22, and the second small diameter portion 24 extend in a direction perpendicular to the axis L. Hereinafter, the direction in which the diameters extend will sometimes be referred to as the diameter direction. The diameter direction is the direction of arrow Y in FIG.

[0019] The rotating shaft 18 is rotatably supported by the casing 16 via a first bearing 26 and a second bearing 28. The tips of the first small diameter portion 20 and the second small diameter portion 24 of the rotating shaft 18 are passed through the first bearing 26 and the second bearing 28, respectively, and are exposed from the casing 16. To the tips exposed from the casing 16, for example, a propeller (not shown) is attached.

[0020] As shown in Figures 1 and 2, a permanent magnet 30 is disposed on the outer periphery of the large diameter portion 22. A sleeve 32 is further provided on the rotating shaft 18. The sleeve 32 covers the outer surface of the permanent magnet 30. The sleeve 32 is made of carbon fiber reinforced plastic (CFRP) and exhibits a certain degree of elasticity. CFRP is formed by impregnating carbon fibers with a matrix resin. An example of a suitable matrix resin is an epoxy resin. The glass transition temperature of epoxy resin is typically around 180°C.

[0021] No external force is acting on the sleeve 32 before it is passed through the rotating shaft 18. This state is the so-called natural state. In its natural state, the inner diameter of the sleeve 32 is slightly smaller than the outer diameter of the large-diameter portion 22. Therefore, when the sleeve 32 is passed through the large-diameter portion 22, it elastically deforms so as to expand slightly in diameter. Thereafter, the sleeve 32 contracts slightly in diameter due to its elastic restoring force. This elastic restoring force causes the sleeve 32 to press the permanent magnet 30 toward the rotating shaft 18. This pressing force causes the permanent magnet 30 to be held by the sleeve 32 on the outer periphery of the rotating shaft 18. The thickness T1 of the sleeve 32 (see FIG. 12) is typically about 0.5 mm to 5 mm.

[0022] 1, the stator 14 has an electromagnetic coil 34. The electromagnetic coil 34 is provided in a stator core (not shown). When the stator 14 is positioned and fixed to the casing 16 and the portion of the rotor 12 on which the permanent magnets 30 are provided is housed in the casing 16, the electromagnetic coil 34 surrounds the permanent magnets 30 via the sleeve 32. When the permanent magnets 30 and the rotating shaft 18 rotate integrally, an alternating magnetic field is generated between the permanent magnets 30 and the electromagnetic coil 34.

[0023] 1 and 2, a resin coating layer 40 is provided on the outer peripheral wall of the sleeve 32. The resin coating layer 40 covers the entire outer peripheral wall of the sleeve 32. As can be seen from FIG. 1, the sleeve 32 and the electromagnetic coil 34 are spaced apart by a predetermined distance. Therefore, an air layer AL is present between the sleeve 32 and the electromagnetic coil 34.

[0024] The base resin of the resin coating layer 40 is preferably a resin that causes less wear of a cutting tool than CFRP when the base resin and CFRP are cut under the same conditions. Specific examples of such resins include epoxy resins and paraxylene resins. The resin coating layer 40 does not contain reinforcing fibers such as carbon fibers.

[0025] FIG. 3 is an enlarged view of a main portion of the resin coating layer 40 when viewed along the axial direction of the rotating shaft 18. The resin coating layer 40 has a base 42 and a protrusion structure formed on the outer peripheral wall of the base 42. In the embodiment shown in FIG. 3, the protrusion structure consists of multiple protrusions that protrude annularly outward in the radial direction of the rotating shaft 18. Each protrusion forms one protrusion 44. Therefore, the protrusion structure shown in FIG. 3 has multiple protrusions 44 formed from multiple protrusions. The multiple protrusions are arranged at approximately equal intervals, so that two adjacent protrusions 44 extend parallel to each other. Between two adjacent protrusions 44 is a groove that is recessed relative to the two protrusions 44. In other words, multiple grooves are formed in the resin coating layer 40. The multiple grooves form riblets 46 that are recessed relative to the protrusions 44.

[0026] In the embodiment shown in Fig. 3, each protrusion 44 is perpendicular to the axial direction of the rotary shaft 18. That is, in this case, the intersection angle θ between the extension direction of the protrusion 44 and the axial direction of the rotary shaft 18 is 90°. Therefore, the protrusions 44 protrude outward in the radial direction of the rotary shaft 18 and the sleeve 32. However, the intersection angle θ may be 45° or greater and is not limited to 90°. For example, the intersection angle θ may be 75° as shown in Fig. 4 or 60° as shown in Fig. 5.

[0027] 4 and 5, it is also possible to form a spirally extending protrusion structure by forming a single protrusion in a spiral shape. Even in this case, when the rotating shaft 18 is viewed along the axial direction, multiple protrusions 44 appear on the resin coating layer 40. In other words, this configuration represents "multiple protrusions formed from a single protrusion." Therefore, this configuration is also included in the "multiple protrusions" in this specification.

[0028] 6 is a schematic longitudinal cross-sectional view of the sleeve 32 and the resin coating layer 40 cut along a direction perpendicular to the extending direction of the protrusions 44. In the embodiment shown in FIG. 6, the extending direction of the protrusions 44 corresponds to the diameter direction of the rotating shaft 18. The base 42 constituting the resin coating layer 40 is a cylindrical body that covers the outer peripheral wall of the sleeve 32.

[0029] As shown in Figure 6, in this case, a cross section along the protrusion direction of the protrusion 44 appears. The cross-sectional shape of the protrusion 44 in this case is typically an isosceles triangle. Figure 6 illustrates a case where the angle α of the apex 50 of the protrusion 44 that protrudes most radially outward from the rotary shaft 18 is 30°. However, α is not limited to 30°. As shown in Figure 7, α may be 45°. As shown in Figure 8, α may be 90°.

[0030] As shown in Fig. 9, the cross section of the protrusions 44 may be wave-shaped with rounded valley portions. As shown in Fig. 10, the cross section of the protrusions 44 may be columnar (or rod-shaped). As can be understood with reference to Figs. 6 to 10, the riblets 46 may be any of concave grooves with flat bottoms (Figs. 6, 7 and 10), V-shaped grooves (Fig. 8), or round grooves with arc-shaped curved bottoms (Fig. 9).

[0031] The distance S between the apex 50 of one protrusion 44 and the apex 50 of the protrusion 44 adjacent to that protrusion 44 is defined as the pitch. In order to sufficiently suppress windage loss when the rotating shaft 18 rotates at high speed, the pitch S is preferably 100 μm or less. However, if the pitch S is excessively small, it is difficult to form the protrusions 44. Therefore, the pitch S is preferably set within the range of 20 μm to 60 μm.

[0032] Furthermore, the amount of protrusion H of one protrusion 44 from the base 42 is defined as the height of the protrusion 44. In order to sufficiently reduce windage loss while sufficiently increasing the aspect ratio of the riblets 46, the height H is preferably 50 μm or less. Furthermore, it is preferable that the following relationship hold between the height H and the pitch S: H=0.5S When the pitch S is within the range of 20 μm to 60 μm, the preferred range of the height H is 10 μm to 30 μm.

[0033] The rotating electric machine 10 configured as described above is mounted on, for example, an aircraft and used as a motor. When the motor is driven, current is passed through the electromagnetic coil 34 shown in FIG. 1. This current passage generates a magnetic field around the electromagnetic coil 34. A repulsive or attractive force acts between this magnetic field and the permanent magnet 30, causing the rotating shaft 18 to begin rotating about the axis L. This generates a flow in the air layer AL between the stator 14 and the resin coating layer 40.

[0034] In an aircraft, a motor may be required to rotate at high speed. In this embodiment, riblets 46 are formed on the resin coating layer 40 provided on the outer peripheral wall of the sleeve 32. Furthermore, the pitch S between two adjacent protrusions 44 forming the riblets 46 is preferably 100 μm or less. Therefore, even when the rotating shaft 18 rotates at high speed, turbulent vortices generated around the rotor 12 are reduced. This reduces turbulent friction viscosity and suppresses the generation of tiller vortices. For these reasons, windage loss can be reduced.

[0035] That is, according to this embodiment, windage loss is sufficiently suppressed. As a result, heating of the permanent magnets 30 is suppressed. Therefore, a decrease in the magnetic force of the permanent magnets 30 is avoided, and the energy conversion efficiency of the rotating electric machine 10 is sufficiently increased. That is, the electrical energy input to the electromagnetic coils 34 is efficiently converted into a driving force that rotates the rotating shaft 18.

[0036] When the rotating electric machine 10 is used as a generator, the driving force that rotates the rotating shaft 18 is efficiently converted into electrical energy that is output from the electromagnetic coil 34. As described above, according to this embodiment, the response characteristics of the rotating electric machine 10 are improved.

[0037] When the base resin of the resin coating layer 40 is an epoxy-based resin or a paraxylene-based resin, the resin coating layer 40 exhibits excellent heat resistance. This is because epoxy-based resins and paraxylene-based resins have excellent heat resistance. Therefore, the shape of the protrusions 44 is maintained even when the rotor 12 rotates at high speed. Moreover, in this case, the resin coating layer 40 is firmly bonded to the sleeve 32 made of carbon fiber reinforced resin. Therefore, the resin coating layer 40 is prevented from falling off the sleeve 32 even when the rotor 12 rotates at high speed. For these reasons, an increase in windage loss during operation of the rotating electric machine 10 can be avoided even when the rotating electric machine 10 is operated continuously for a long period of time.

[0038] Next, a method for manufacturing the rotor 12 that constitutes the rotating electrical machine 10 will be described. Fig. 11 shows a schematic flow of the manufacturing method according to this embodiment. The method for manufacturing the rotor 12 includes a sleeve mounting process ST1, a resin coating process ST2, and a protrusion forming process ST3.

[0039] Here, to obtain the sleeve 32 made of carbon fiber reinforced resin, the prepreg is bent into a cylindrical shape and heat is applied to the prepreg in this state, thereby hardening the matrix resin in the prepreg, thereby obtaining the sleeve 32. The thickness T1 of the sleeve 32 shown in Fig. 12 is, for example, about 0.5 mm to 5 mm.

[0040] First, in the sleeve attachment step ST1, the outer surface of the permanent magnet 30 is covered with the sleeve 32 obtained as described above. That is, the sleeve 32 is passed through the large-diameter portion 22 on which the permanent magnet 30 is provided. As described above, at this time, the sleeve 32 expands slightly in diameter due to elastic deformation, and then contracts slightly in diameter due to elastic restoring force. As a result, the sleeve 32 presses the permanent magnet 30 toward the center of the rotating shaft 18. Accordingly, the permanent magnet 30 is held on the outer periphery of the large-diameter portion 22 by the sleeve 32.

[0041] Next, a resin coating step ST2 is performed. Specifically, for example, a resin that causes less wear of a cutting tool than CFRP when cut under the same conditions as CFRP is applied to the outer peripheral wall of the sleeve 32. Specific examples of such a resin include the above-mentioned epoxy resins and paraxylene resins. When the matrix resin in the prepreg is an epoxy resin, these resins are easily cut at the glass transition temperature (around 180°C) of the matrix resin.

[0042] Next, heat or the like is applied to the resin coating layer 40. This hardens the resin coating layer 40. If the base resin of the resin coating layer 40 is an ultraviolet-curable resin, ultraviolet light is irradiated onto the resin coating layer 40. As a result, a hardened resin coating layer 40 is formed on the outer peripheral wall of the sleeve 32, as shown in FIG. 12. At this point, the thickness T2 of the resin coating layer 40 may be greater than the thickness T1 of the sleeve 32.

[0043] Next, a protrusion forming step ST3 is performed. In this embodiment, as shown in FIG. 13, cutting is performed on the resin coating layer 40. The cutting tool 60 used at this time may be a cemented carbide tool, a cubic boron nitride (CBN) tool, or a single crystal diamond tool, with a single crystal diamond tool being particularly preferred. In this case, protrusions 44 with good dimensional accuracy can be easily obtained by cutting, and further, wear is relatively small even when cutting is repeated.

[0044] When the base resin of the resin coating layer 40 is an epoxy resin, a paraxylene resin, or the like, it is easy to perform cutting on the resin coating layer 40, as described above. Even when the thickness T2 of the resin coating layer 40 is large, it is easy to perform cutting on the resin coating layer 40. Moreover, cutting makes it possible to obtain protrusions 44 with better dimensional accuracy at a lower cost than other processing methods.

[0045] The cutting process is performed while rotating the rotating shaft 18, on which the resin coating layer 40 is formed, around the axis L (see FIG. 1). In this case, if the intersection angle θ between the extension direction of the protrusions 44 and the axial direction of the rotating shaft 18 is less than 45°, it is difficult for the cutting tool 60 to proceed along the cutting direction. Therefore, it is preferable to set the intersection angle θ to 45° or more. In other words, by setting the intersection angle θ to 45° to 90°, the protrusions 44 can be easily formed by cutting. The intersection angle θ can be, for example, 90° as shown in FIG. 3, 75° as shown in FIG. 4, or 60° as shown in FIG. 5.

[0046] Furthermore, it is preferable to form the protrusions 44 so as to obtain a triangular cross section in which the angle α of the apex 50 is 30° to 90° (see FIGS. 6 to 8). Alternatively, as shown in FIG. 9, it is also possible to form the protrusions 44 having a wave-shaped cross section so that the riblets 46 become round grooves. The protrusions 44 having such a cross section can be easily formed by cutting or the like. Note that, as shown in FIG. 10, the protrusions 44 may also be formed so as to have a columnar (or rod-shaped) cross section.

[0047] Furthermore, cutting is performed so that the pitch S between two adjacent protrusions 44 (see FIGS. 6 to 10) is preferably 100 μm or less, and more preferably 60 μm. However, it is not easy to make the pitch S less than 10 μm using cutting. Therefore, it is preferable to set the pitch S in the range of 20 μm to 60 μm.

[0048] Furthermore, cutting is performed so that the height H of the protrusions 44 is 50 μm or less, and preferably 0.5 times the pitch S. By setting the pitch S and height H to the values ​​described above, windage loss can be sufficiently suppressed even when the rotor 12 is rotated at high speed.

[0049] By forming the protrusions 44 on the outer peripheral wall of the base 42 in the above manner, riblets 46 are formed. The riblets 46 have a shape that is recessed relative to the protrusions 44.

[0050] Alternatively, laser processing, polishing, etc. may be performed in the protrusion forming step ST3. In the case of laser processing, polishing, etc., the processing speed can be made relatively high.

[0051] As described above, this embodiment discloses a rotating electric machine (10) comprising a rotor (12) and a stator (14), the rotor having a rotating shaft (18) and a permanent magnet (30) held by the rotating shaft, and the stator having an electromagnetic coil (34) surrounding the permanent magnet, the rotor comprising: a sleeve (32) that covers the outer surface of the permanent magnet on the rotating shaft and is spaced a predetermined distance from the stator; and a resin coating layer (40) provided on the outer peripheral wall of the sleeve, the sleeve being made of carbon fiber reinforced resin, the resin coating layer having a base (42) that covers the outer peripheral wall of the sleeve and a protrusion structure protruding from the outer peripheral wall of the base, the protrusion structure consisting of one or more convex portions that form a plurality of protrusions (44) extending parallel to one another, and riblets (46) that are recessed relative to the plurality of protrusions are formed between the plurality of protrusions.

[0052] Riblets are formed between two adjacent protrusions. These riblets reduce the turbulent vortices that occur around the rotor, even when the rotor rotates at high speed. This reduces turbulent friction viscosity and suppresses the occurrence of tiller vortices. For these reasons, windage loss can be reduced.

[0053] As a result, the permanent magnets are prevented from being heated, and therefore the magnetic force of the permanent magnets is prevented from decreasing, resulting in a sufficiently high energy conversion efficiency in the rotating electrical machine.

[0054] This embodiment discloses a method for manufacturing a rotor (12) that has a rotating shaft (18) and a permanent magnet (30) held by the rotating shaft and is surrounded by a stator (14) in a rotating electric machine (10), the method comprising: a sleeve attachment process (ST1) for covering the outer surface of the permanent magnet with a sleeve (32) made of carbon fiber reinforced resin; a resin coating process (ST2) for coating the outer peripheral wall of the sleeve with a resin coating layer (40); and a protrusion forming process (ST3) for forming, in the resin coating layer, a base (42) that covers the outer peripheral wall of the sleeve and a protrusion structure that protrudes from the outer peripheral wall of the base by removing a portion of the outer peripheral wall of the resin coating layer by processing; in the protrusion forming process, the protrusion structure is provided as one or more convex portions that form a plurality of protrusions (44) that extend parallel to each other, thereby forming riblets (46) that are recessed relatively to the plurality of protrusions.

[0055] In this embodiment, the sleeve is made of carbon fiber reinforced resin. Furthermore, the sleeve is generally thin-walled. It is generally difficult to perform machining, such as cutting, on thin-walled carbon fiber reinforced resin. Therefore, it is not easy to form protrusions on the outer peripheral wall of the sleeve.

[0056] In contrast, in this embodiment, the sleeve is coated with a resin coating layer, and protrusions are formed on this resin coating layer. For example, by forming the resin coating layer with a large thickness, the protrusions can be easily formed by cutting the resin coating layer. Furthermore, since there is no need to perform cutting or other processing on the sleeve, damage such as cracking of the sleeve can be avoided.

[0057] This embodiment discloses a rotating electric machine in which the extending direction of the plurality of protrusions intersects with the axial direction (X) of the rotating shaft at an angle (θ) of 45° to 90°.

[0058] This embodiment discloses a rotor manufacturing method in which, in the protrusion forming process, the multiple protrusions are formed so as to extend in a direction intersecting the axial direction (X) of the rotating shaft at an angle (θ) of 45° to 90°.

[0059] The protrusions are formed, for example, by cutting the resin coating layer while rotating the rotating shaft. In this cutting process, it is easy to form protrusions extending in the above-mentioned directions. That is, in this case, the protrusions can be easily formed.

[0060] This embodiment discloses a rotating electric machine in which, when the height of each of the plurality of protrusions is H and the pitch between two adjacent protrusions among the plurality of protrusions is S, S is 100 μm or less and the following formula holds: H=0.5S

[0061] This embodiment discloses a method for manufacturing a rotor, in which, when the height of each of the plurality of protrusions is H and the pitch between two adjacent protrusions among the plurality of protrusions is S, the plurality of protrusions are formed in the protrusion forming process so that the following formula holds: H=0.5S

[0062] By setting the pitch S to 100 μm or less, windage loss can be sufficiently reduced even when the rotor rotates at high speed. Furthermore, by setting the height H to 1 / 2 the pitch S, the aspect ratio of the riblets becomes sufficiently large. This also makes it possible to sufficiently reduce windage loss when the rotor rotates at high speed.

[0063] This embodiment discloses a rotating electric machine in which the cross-sectional shape of the plurality of protrusions is triangular when the plurality of protrusions are cut along a direction perpendicular to the direction in which the plurality of protrusions extend.

[0064] This embodiment discloses a method for manufacturing a rotor, in which the multiple protrusions are formed in the protrusion forming process so that when the multiple protrusions are cut along a direction perpendicular to the extension direction of the multiple protrusions, the cross-sectional shape of the multiple protrusions is triangular.

[0065] By making the cross section triangular, the protrusions can be formed more easily than protrusions with other cross sections.

[0066] This embodiment discloses a rotating electric machine in which, when the plurality of protrusions are cut along a direction perpendicular to the extension direction of the plurality of protrusions, the angle (α) of the apex (50) that protrudes most radially outward from the rotating shaft in the cross section of the plurality of protrusions is 30° to 90°.

[0067] This embodiment discloses a method for manufacturing a rotor, in which the protrusions are formed in the protrusion forming process so that when the protrusions are cut along a direction perpendicular to the extension direction of the protrusions, the angle (α) of the apex (50) that protrudes most radially outward from the rotating shaft in the cross section of the protrusions is 30° to 90°.

[0068] By setting the apex angle within this range, the protrusions can be formed more easily than protrusions with apex angles outside the above range.

[0069] This embodiment discloses a rotor manufacturing method in which, in the protrusion forming step, a part of the outer peripheral wall of the resin coating layer is removed by cutting.

[0070] By using cutting processing, it is possible to easily form protrusions with good dimensional accuracy at low cost.

[0071] This embodiment discloses a rotating electric machine in which the base resin of the resin coating layer is formed from a resin that causes less wear on a cutting tool than the carbon fiber reinforced resin when the base resin and the carbon fiber reinforced resin are subjected to cutting processing under the same conditions.

[0072] This embodiment discloses a method for manufacturing a rotor, in which the resin coating step is performed using a resin that causes less wear on a cutting tool than a carbon fiber reinforced resin when the base resin and a carbon fiber reinforced resin are subjected to cutting processing under the same conditions as the base resin of the resin coating layer, and the resin coating layer is formed using the resin.

[0073] In this case, the protrusions can be easily formed by cutting the resin coating layer.

[0074] This embodiment discloses a rotating electric machine in which the base resin is an epoxy-based resin or a paraxylene-based resin.

[0075] This embodiment discloses a method for manufacturing a rotor using an epoxy resin or a paraxylene resin as the base resin.

[0076] Epoxy-based resins and paraxylene-based resins are easily processable resins. Therefore, it is easy to perform cutting on the resin coating layer, making it easy to form regular protrusions with a predetermined pitch and height. Furthermore, epoxy-based resins and paraxylene-based resins have excellent heat resistance. Therefore, the shape of the protrusions is maintained even when the rotor rotates at high speed. Furthermore, when the base resin is epoxy-based resin or paraxylene-based resin, the resin coating layer is firmly bonded to the sleeve made of carbon fiber reinforced resin. Therefore, the resin coating layer is prevented from falling off the sleeve even when the rotor rotates at high speed.

[0077] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0078] 10... Rotating electric machine 12... Rotor 14... Stator 18... Rotating shaft 30...Permanent magnet 32...Sleeve 34...Electromagnetic coil 40...Resin coating layer 42...Base 44...Protrusion 46...Riblet 50...Top 60...Cutting tool AL...Air layer L…Axis line

Claims

1. A method for manufacturing a rotor having a rotating shaft and a permanent magnet held by the rotating shaft, the rotor being surrounded by a stator in a rotating electric machine, comprising: a sleeve attachment step of covering the outer surface of the permanent magnet with a sleeve made of carbon fiber reinforced resin; a resin coating step of coating an outer peripheral wall of the sleeve with a resin coating layer; a protrusion forming step of forming, in the resin coating layer, a base portion that covers the outer peripheral wall of the sleeve and a protrusion structure that protrudes from the outer peripheral wall of the base portion by processing and removing a portion of the outer peripheral wall of the resin coating layer; and A method for manufacturing a rotor, wherein in the protrusion forming process, the protrusion structure is provided as one or more convex portions that form multiple protrusions extending parallel to each other, thereby forming a riblet that is recessed relatively to the multiple protrusions.

2. 2. The manufacturing method of claim 1, wherein in the protrusion forming step, the plurality of protrusions are formed so as to extend in a direction intersecting the axial direction of the rotating shaft at an angle of 45° to 90°.

3. 2. A rotor manufacturing method according to claim 1, wherein, when the height of each of the plurality of protrusions is H and the pitch between two adjacent protrusions among the plurality of protrusions is S, the plurality of protrusions are formed in the protrusion forming step so that the following formula holds: H=0.5S

4. 2. The manufacturing method of claim 1, wherein the plurality of protrusions are formed in the protrusion forming step so that when the plurality of protrusions are cut along a direction perpendicular to the extension direction of the plurality of protrusions, the cross-sectional shape of the plurality of protrusions is triangular.

5. 5. A manufacturing method for a rotor according to claim 4, wherein the plurality of protrusions are formed in the protrusion forming step so that when the plurality of protrusions are cut along a direction perpendicular to the extension direction of the plurality of protrusions, the angle of the apex that protrudes most outward in the diameter direction of the rotating shaft in a cross section of the plurality of protrusions is 30° to 90°.

6. 6. The rotor manufacturing method according to claim 1, wherein in the protrusion forming step, a part of the outer peripheral wall of the resin coating layer is removed by cutting.

7. 7. A rotor manufacturing method according to claim 6, wherein the resin coating step is performed using a resin that causes less wear on a cutting tool than a carbon fiber reinforced resin when the base resin and a carbon fiber reinforced resin are cut under the same conditions as each other, to form the resin coating layer.

8. 8. The method of manufacturing a rotor according to claim 7, wherein the base resin is an epoxy resin or a paraxylene resin.

Images