Method of manufacturing rotor core and rotor core

Abstract

To provide a method of manufacturing a rotor core capable of improving the degree of orientation of a bond magnet incorporated in the rotor core, and to provide the rotor core.SOLUTION: The method for manufacturing a rotor core according to the present disclosure includes a step of injecting a bonded-magnet material into the magnet slot 111 and a step of applying a magnetic field to the injected bonded-magnet material. The magnet slot 111 includes a first region A1 located at an end and a second region A2 adjacent to the first region, and the magnet slot 111 in the first region A1 is narrower than the magnet slot 111 in the second region A2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a rotor core and a rotor core. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing a rotor core equipped with a bonded magnet. In the manufacturing method described in Patent Document 1, the bonded magnet is formed by injecting a bonded magnet material into magnet slots provided in the rotor core body while applying a magnetic field to the rotor core body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-162329 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application discovered that there are areas near the ends of the magnet slots where it is difficult to apply a magnetic field, and as a result, the degree of orientation of the bonded magnets in these areas decreases. In other words, the inventors of the present application have discovered a problem in that the degree of orientation of the bonded magnets provided in the rotor core cannot be sufficiently improved in the conventional technology. Patent Document 1 does not describe any technology that can solve the above-mentioned problems.

[0005] The present disclosure has been made to solve such problems, and aims to provide a rotor core manufacturing method and a rotor core that can improve the orientation of bonded magnets embedded in the rotor core. [Means for solving the problem]

[0006] A manufacturing method of a rotor core according to the present disclosure includes a step of injecting a bonded magnet material into a magnet slot and a step of applying a magnetic field to the injected bonded magnet material, and the cross section of the magnet slot has a first region located at an end and a second region adjacent to the first region, and the width of the cross section of the magnet slot in the first region is narrower than the width of the cross section of the magnet slot in the second region.

[0007] With this configuration, a sufficient magnetic field is applied to the bonded magnet material, resulting in improved alignment of the bonded magnets embedded in the rotor core.

[0008] In the manufacturing method of a rotor core according to the present disclosure, the cross section of the magnet slot may have a convex shape.

[0009] In the manufacturing method of a rotor core according to the present disclosure, the magnet slot may consist of a plurality of small magnet slots, and the curvature of the inner corner of the cross section of the small magnet slot located at the end may be greater than the curvature of the corresponding corner of the cross section of the other small magnet slots.

[0010] In the manufacturing method of a rotor core according to the present disclosure, the magnet slot may consist of a plurality of small magnet slots, the first region may be a small magnet slot provided at the end, and the second region may be another small magnet slot adjacent to the small magnet slot provided at the end.

[0011] The rotor core according to the present disclosure includes a rotor core body having magnet slots and bonded magnets filled in the magnet slots. The magnet slots have a first region located at an end and a second region adjacent to the first region, and the width of the magnet slot in the first region is narrower than the width of the magnet slot in the second region.

[0012] With this configuration, a sufficient magnetic field is applied to the bonded magnet material when molding the bonded magnet, which results in improved orientation of the bonded magnets embedded in the rotor core. [Effects of the Invention]

[0013] The present disclosure makes it possible to provide a rotor core manufacturing method and a rotor core that can improve the degree of orientation of bonded magnets built into the rotor core. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are a perspective view and a cross-sectional view showing the configuration of a rotor core according to a first embodiment. [Figure 2] 1 is a cross-sectional view showing the configuration of a rotor core according to a first embodiment. [Figure 3] 3 is a flowchart showing a method for manufacturing a rotor core according to the first embodiment. [Figure 4] 3A to 3C are cross-sectional views illustrating a method for manufacturing a rotor core according to the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of a rotor core according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] (First embodiment) <Rotor core configuration> Hereinafter, a first embodiment according to the present disclosure will be described in detail with reference to the drawings. First, the configuration of the rotor core according to this embodiment will be described in detail.

[0016] Fig. 1 is a perspective view and a cross-sectional view showing the configuration of a rotor core according to the first embodiment. More specifically, Fig. 1(a) is a perspective view showing the configuration of the rotor core according to this embodiment, and Fig. 1(b) is a cross-sectional view showing the configuration of the rotor core according to this embodiment. Naturally, the right-handed xyz Cartesian coordinate system shown in Figure 1 and other drawings is for the convenience of explaining the positional relationships of the components. Normally, the positive direction of the z axis is vertically upward, and the xy plane is the horizontal plane, which is common among the drawings.

[0017] The rotor core 1 is used as a rotor of a motor mounted on an electric vehicle such as a BEV (Battery Electric Vehicle), an HEV (Hybrid Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle), or an FCEV (Fuel Cell Electric Vehicle).

[0018] A rotor core 1, which is a component of the motor, is disposed inside a stator core (not shown), and rotates around a straight line X indicated by a broken line as a rotation axis. Hereinafter, in this specification, the direction parallel to the rotation axis, i.e., the direction parallel to the line X, will be referred to as the axial direction, and the direction perpendicular to the rotation axis, i.e., the direction perpendicular to the line X, will be referred to as the radial direction.

[0019] The rotor core 1 includes a rotor core body 11 and a bonded magnet 12 . The rotor core body 11 is a hollow cylindrical metal member and is formed by laminating, for example, annular electromagnetic steel sheets.

[0020] The rotor core body 11 is provided with magnet slots 111, and the magnet slots 111 are filled with bond magnets 12. 1(b), eight arc-shaped magnet slots 111 that convex inward in the system direction are provided along the circumferential direction in the rotor core body 11. Radially oriented bonded magnets 12 are filled in the magnet slots 111.

[0021] Naturally, in the rotor core according to the present disclosure, the number of magnet slots 111 that one rotor core has is not limited to eight, and one rotor core may have at least one magnet slot 111.

[0022] Fig. 2 is a cross-sectional view showing the configuration of the rotor core according to the first embodiment. More specifically, Fig. 2 is a cross-sectional view for explaining the cross-sectional shape of the magnet slot 111 according to the first embodiment, and is an enlarged view of Fig. 1(b). The cross-sectional shape of the magnet slot according to this embodiment will be described in more detail below using Fig. 2.

[0023] 2, the magnet slot 111 according to this embodiment is made up of a plurality of small magnet slots. More specifically, the magnet slot 111 is made up of two small magnet slots 111a and two small magnet slots 111b.

[0024] The small magnet slots 111a and 111b are each independently formed into four through holes in the rotor core body 11. The small magnet slots 111a and 111b are arranged side by side in an arc shape via a bridge structure to form one magnet slot 111.

[0025] To explain the small magnet slots 111a and 111b in more detail, the small magnet slot 111a is a through hole located at the end of the arc-shaped cross section of the magnet slot 111. The small magnet slot 111b is a through hole located in the center of the arc-shaped cross section of the magnet slot 111.

[0026] The cross section of the small magnet slot 111a has a first region A1 located at the end and a second region A2 adjacent to the first region, and the width of the magnet slot 111 in the first region A1 is narrower than the width of the magnet slot 111 in the second region. 2, the cross section of the small magnet slot 111a has a convex shape, which forms a first region A1 and a second region A2 with different widths in the cross section of the small magnet slot 111a.

[0027] As described above, the small magnet slot 111a is located at the end of the arc-shaped cross section of the magnet slot 111. Therefore, it can be said that the first region A1 located at the end of the small magnet slot 111a is located at the end of the cross section of the magnet slot 111. Therefore, the above-described configuration can be rephrased as follows: the cross section of the magnet slot 111 has a first region A1 located at the end and a second region adjacent to the first region, and the width of the cross section of the magnet slot 111 in the first region is narrower than the width of the cross section of the magnet slot 111 in the second region.

[0028] It should be noted that the magnet slot 111 according to the present disclosure does not necessarily have to be made up of multiple magnet slots, and may be made up of, for example, a single through hole. Furthermore, the cross-sectional shape of the magnet slot 111 according to the present disclosure does not necessarily have to be a substantially arc shape, but may be, for example, a substantially V-shape or a linear shape.

[0029] That is, the magnet slot 111 has a cross-sectional shape with an end, and includes a first region A1 located at the end and a second region A2 adjacent to the first region, and may have any cross-sectional shape as long as the cross-sectional width in the first region A1 is narrower than the cross-sectional width in the second region.

[0030] Although details will be described later, the bonded magnet according to this embodiment is manufactured by applying a magnetic field to the bonded magnetic material injected into magnet slot 111. Because magnet slot 111 has the cross-sectional shape described above, a magnetic field can be applied efficiently to the bonded magnetic material, and as a result, the degree of orientation of bonded magnet 12 is improved.

[0031] Bonded magnet 12 is filled in magnet slot 111 and is radially oriented outward in the radial direction. Bonded magnet 12 is formed by injecting a mixture of magnetic powder and binder into magnet slot 111 and then hardening it. Therefore, the shape of bonded magnet 12 roughly matches the shape of magnet slot 111.

[0032] As explained above, the rotor core 1 according to this embodiment includes a rotor core body 11 having magnet slots 111, and bonded magnets 12. In the rotor core 1 according to this embodiment, the cross section of the magnet slots 111 includes a first region A1 and a second region A2, and the width of the magnet slot in the first region A1 is narrower than the width of the magnet slot in the second region A2. Although details will be given later, with this configuration, a magnetic field is efficiently applied to the bonded magnet material when forming bonded magnet 12, resulting in an improved degree of orientation of the bonded magnet.

[0033] <Rotor core manufacturing method> Next, a detailed description will be given of the method for manufacturing the rotor core according to the first embodiment. Fig. 3 is a flowchart showing the method for manufacturing the rotor core according to the first embodiment.

[0034] In the manufacturing method of the rotor core according to this embodiment, first, a bonded magnet material is injected into the magnet slots (step S1). More specifically, the bonded magnet material, which is a mixture of magnetic powder and a binder, is injected into the hollow magnet slots 111. The rotor core body 11 can be manufactured, for example, by laminating electromagnetic steel sheets having through holes corresponding to the cross-sectional shapes of the magnet slots.

[0035] Furthermore, examples of magnetic powders that can be used as the bonded magnet material include, but are not limited to, ferrite-based magnetic powders such as barium ferrite and strontium ferrite, and rare earth-based magnetic powders such as samarium cobalt, neodymium, and samarium iron nitrogen. That is, in the bonded magnet material according to this embodiment, any magnetic powder may be used as long as it can form a bonded magnet having magnetic properties above a predetermined level.

[0036] Furthermore, binders that can be used as bonded magnet materials include, but are not limited to, thermosetting resins such as epoxy resins, and thermoplastic resins such as nylon resins, polyphenylene sulfide resins, and acrylate resins. That is, in the bonded magnet material according to this embodiment, any binder may be used as long as it can form a bonded magnet having magnetic properties above a predetermined level.

[0037] Next, a magnetic field is applied to the injected bonded magnet material (step S2). Figure 4 is a cross-sectional view illustrating the manufacturing method of the rotor core according to the first embodiment. More specifically, Figure 4(a) is a cross-sectional view illustrating the application of a magnetic field to the bonded magnet material injected into the magnet slot according to the present embodiment, and Figure 4(b) is a cross-sectional view illustrating the application of a magnetic field to the bonded magnet material injected into the magnet slot according to the comparative example.

[0038] As shown in Fig. 4(a), in the rotor core manufacturing method according to this embodiment, a magnetic field is applied to the magnet slots using an application device 2. Here, arrow B1 shown in Fig. 4(a) represents the flow of magnetic flux.

[0039] As shown in Figure 4(a), in the manufacturing method of the rotor core according to this embodiment, in the process of applying a magnetic field to the bonded magnet material, the magnetic flux B1 flowing from the application device 2 changes direction near the region A2 and flows to the corner of the magnet slot 111.

[0040] Therefore, in the manufacturing method of the rotor core according to this embodiment, a sufficient magnetic field is applied to the corners of magnet slots 111, and as a result, the degree of orientation of bonded magnets 12 after manufacturing is improved.

[0041] On the other hand, Fig. 4(b) shows the application of a magnetic field in a comparative example, which differs from the present embodiment in that the small magnet slot 111c, which is provided at a position corresponding to the small magnet slot 111a in the present embodiment, has a uniform width.

[0042] As shown in FIG. 4(b), in the manufacturing method of the rotor core according to the comparative example, in the step of applying a magnetic field to the bonded magnet material, magnetic flux B2 flowing from application device 2 branches near the corners of magnet slot 111.

[0043] Therefore, in the rotor core manufacturing method according to the comparative example, a magnetic field is not sufficiently applied to the corners of the magnet slot 111, resulting in a lower degree of orientation of the bond magnet 12 compared to when the rotor core manufacturing method according to the present embodiment is used.

[0044] After step S2 or simultaneously with step S2, the bonded magnet material is solidified, thereby completing rotor core 1 according to this embodiment. As a method for solidifying the bonded magnet material, a method that corresponds to the binding material contained in the bonded magnet material can be used.

[0045] As explained above, the manufacturing method of the rotor core according to this embodiment includes the steps of injecting a bonded magnet material into a magnet slot and applying a magnetic field to the bonded magnet material. The cross section of the magnet slot has a first region located at the end and a second region adjacent to the first region, and the width of the cross section of the magnet slot in the first region is narrower than the width of the cross section of the magnet slot in the second region.

[0046] With this configuration, the manufacturing method of the rotor core according to this embodiment can apply a sufficient magnetic field even to the corners of the magnet slots, which results in an improved degree of orientation of the bonded magnets.

[0047] (Other embodiments) FIG. 5 is a cross-sectional view showing the configuration of a rotor core according to another embodiment. More specifically, Figures 5(a), 5(b), and 5(c) are cross-sectional views for explaining the cross-sectional shape of the magnet slots according to other embodiments, and are cross-sectional views of the rotor core cut along a plane perpendicular to the axial direction.

[0048] The rotor cores according to the other embodiments have different cross-sectional shapes of the magnet slots from the first embodiment, but other configurations and manufacturing methods are similar to those of the first embodiment.

[0049] <Other embodiment 1> 5(a), in a rotor core and a manufacturing method of a rotor core according to another embodiment, the magnet slot 111 is made up of a plurality of small magnet slots 111a and 111b. The curvature of the inner corner A3 of the cross section of the small magnet slot 111a located at the end is greater than the curvature of the corresponding corner A4 of the cross section of the other small magnet slot 111b.

[0050] In this case, the portion of the small magnet slot 111a where the cross-sectional width is reduced due to the large curvature corresponds to the first region in the first embodiment, and the other portion of the small magnet slot 111a corresponds to the second region in the first embodiment.

[0051] Even with this configuration, in the step of applying a magnetic field to the bonded magnet material (step S2), a sufficient magnetic field can be applied to the corners of magnet slot 111. As a result, the rotor core and rotor core manufacturing method according to other embodiments can improve the degree of orientation of bonded magnet 12.

[0052] <Other embodiment 2> 5(b), in a rotor core and a manufacturing method of a rotor core according to another embodiment, the magnet slot 111 is made up of a plurality of small magnet slots 111a and 111b. The cross-sectional width of the magnet slot 111 at the small magnet slot 111a is narrower than the cross-sectional width of the magnet slot 111 at the small magnet slot 111b.

[0053] That is, in the other embodiment shown in FIG. 5(b), the first region in the first embodiment corresponds to the small magnet slot 111a provided at the end, and the second region in the first embodiment corresponds to another small magnet slot 111b adjacent to the small magnet slot 111a provided at the end.

[0054] With this configuration, in the step of applying a magnetic field to the bonded magnet material (step S2), a sufficient magnetic field can be applied to small magnet slots 111a. As a result, the rotor core and the manufacturing method of the rotor core according to the other embodiments can improve the degree of orientation of bonded magnets 12.

[0055] <Other embodiment 3> As shown in FIG. 5(c), in a rotor core and a manufacturing method of a rotor core according to another embodiment, the magnet slot 111 is made up of only a single through hole. The cross section of the magnet slot 111 according to the other embodiment includes a first region A5 located at the end and a second region A6 adjacent to the first region A5. The cross-sectional width of the magnet slot 111 in the first region A5 is narrower than the cross-sectional width of the magnet slot 111 in the second region A6.

[0056] Even with this configuration, the rotor core and rotor core manufacturing method according to the present disclosure can improve the degree of orientation of bonded magnets 12. In other words, in the rotor core and rotor core manufacturing method according to the present disclosure, the magnet slot does not need to be composed of multiple small magnet slots, but may be a single through hole.

[0057] The present invention has been described above in accordance with the above-described embodiments, but the present invention is not limited to the configurations of the above-described embodiments, and naturally includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the invention claimed in the claims of this application. [Explanation of symbols]

[0058] 1 rotor core 11 Rotor core body 111a, 111b Small magnet slot 12 Bonded Magnets A1 1st area A2 2nd area

Claims

1. Injecting a bonded magnet material into the magnet slots; applying a magnetic field to the injected bonded magnet material; a cross section of the magnet slot having a first region located at an end and a second region adjacent to the first region, and a width of the cross section of the magnet slot in the first region being narrower than a width of the cross section of the magnet slot in the second region; A manufacturing method of a rotor core.

2. The cross section of the magnet slot has a convex shape. The method for manufacturing a rotor core according to claim 1 .

3. the magnet slot comprises a plurality of small magnet slots; the curvature of the inner corner of the cross section of the small magnet slot located at the end is greater than the curvature of the corresponding corner of the cross section of the other small magnet slots; The method for manufacturing a rotor core according to claim 1 .

4. the magnet slot comprises a plurality of small magnet slots; the first region is a small magnet slot at the end; the second region is another small magnet slot adjacent to the small magnet slot provided at the end; The method for manufacturing a rotor core according to claim 1 .

5. a rotor core body having magnet slots; a bonded magnet filled in the magnet slot; A cross section of the magnet slot includes a first region located at an end and a second region adjacent to the first region, and the width of the magnet slot in the first region is narrower than the width of the magnet slot in the second region. Rotor core.

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