Rotor structure of an interior magnet motor and its manufacturing method

Abstract

To provide a rotor structure of a magnet embedded type motor (IMP motor) which has a simple structure and can achieve reduction in weight.SOLUTION: A rotor structure of a magnet embedded type motor includes a shaft 10, and a rotor 20 having a rotor core 21 mounted on the shaft 10, wherein the rotor core 21 is an electromagnetic steel plate laminate having a cylindrical outer peripheral surface, and has a through hole 211 penetrating in an axial direction of the shaft 10, a resin iron core 23 and a permanent magnet 22 are sequentially arranged from the shaft 10 side to the radial outside in the through hole 211, and the resin iron core 23 is a resin molding including a soft magnetic material.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotor structure of an interior magnet motor and a manufacturing method thereof. [Background technology]

[0002] Interior Permanent Magnet Motors (IPM motors), which have permanent magnets embedded in the rotor core, are used in a variety of fields because they can utilize both magnetic torque generated by the magnetic flux of the permanent magnet and reluctance torque generated by changes in the magnetic resistance (reluctance) of the rotor core as rotational force.

[0003] BACKGROUND ART There have been known applications that aim to reduce the weight of rotors in interior permanent magnet motors (IPM motors) (see, for example, Patent Documents 1 to 3).

[0004] In Patent Document 1 (FIG. 2), the rotor core 14 is constructed by stacking magnetic steel plates 22 in the axial direction, and magnet storage holes 18 are formed in the rotor core 14 at predetermined intervals in the circumferential direction, and hollow holes 20 are formed radially inward of the magnet storage holes 18 at predetermined intervals in the circumferential direction to reduce the weight of the rotor 10.

[0005] In Patent Document 2 (FIG. 5), weight reduction is achieved by forming through holes 42 in a laminated core 31. Furthermore, outer edge through holes 39 provided near the outer edge of the laminated core 31 are filled with resin magnets 40.

[0006] In Patent Document 3 (FIG. 2), the rotor 5 is composed of flat plate members 10 made of polygonally arranged permanent magnets 3, a resin material 19 between them, magnetically permeable laminated members 9 made of silicon steel plates with excellent magnetic permeability and arranged on the outside of the polygonal flat plate members 10, reinforcing members 4 made of a non-magnetic material arranged on the outer periphery of the magnetically permeable laminated members 9, and a magnetically permeable member 8 arranged inside the polygonally arranged flat plate members 10 and fixed to the rotating shaft 2. Because the magnetically permeable member 8 can be made of a porous material impregnated with a resin material, the rotor 5 can be made light in weight even if it is configured with a large diameter. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-100634 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-016810 [Patent Document 3] Japanese Patent Application Publication No. 11-196555 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in Patent Document 1, weight reduction of the rotor is attempted by forming holes in the rotor core, and although weight reduction can be promoted by forming larger holes, if the holes are too large there is a risk of the strength of the rotor core being reduced. Similarly to Patent Document 1, Patent Document 2 attempts to weight reduction of the rotor by forming holes in the laminated iron core, which is the rotor core, and weight reduction can be promoted by forming larger holes, but if the holes are too large there is a risk of the strength of the rotor core being reduced.

[0009] In Patent Document 3, the magnetically permeable member 8 can be made of ceramic or metal, and can be made of a porous material so that it can be impregnated with a resin material. However, because it is made of ceramic or metal even if it is porous, it is difficult to say that it sufficiently reduces the weight of the rotor. Also, in Patent Document 3, the silicon steel plate 22 is made of a plurality of arc-shaped members 23, each of which has a flat surface that contacts the flat plate member 10 in its entire stacked shape and an arc-shaped outer periphery, and the arc-shaped members 23 are arranged corresponding to the flat plate member 10, and the edges extending in the longitudinal direction of the arc-shaped members 23 are joined to each other by welding 24 or the like. This requires welding work.

[0010] In view of the above problems, an object of the present invention is to provide a rotor structure for an interior permanent magnet motor (IPM motor) that is simple in structure and lightweight. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the object, a rotor structure according to one aspect of the present invention includes a shaft and a rotor having a rotor core attached to the shaft, the rotor core being an electromagnetic steel sheet laminate having a cylindrical outer surface and having a through hole that passes through the axial direction of the shaft, a resin core and a permanent magnet being arranged in the through hole in that order from the shaft side toward the radially outward side, and the resin core being a resin molded body containing a soft magnetic material. [Effects of the Invention]

[0012] According to one aspect of the present invention, a rotor structure for an interior permanent magnet motor (IPM motor) that is simple in structure and lightweight can be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a rotor structure according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the rotor core in the first embodiment. [Figure 3]FIG. 3 is a diagram for explaining a manufacturing method of the rotor structure according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing a schematic configuration of a rotor structure according to the second embodiment. [Figure 5-1] FIG. 5-1 is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 5-2] FIG. 5-2 is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 6-1] FIG. 6A is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 6-2] FIG. 6-2 is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 7-1] FIG. 7-1 is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 7-2] FIG. 7-2 is a diagram for explaining a manufacturing method of the rotor structure according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing a 1 / 8 model of the rotor structure used in the magnetic field analysis. [Figure 9] FIG. 9 is a diagram showing the analysis results of the surface magnetic flux density of the magnet in the example. [Figure 10] FIG. 10 is a diagram showing the analysis results of the back electromotive force in the example. [Figure 11] FIG. 11 is a diagram for explaining a manufacturing method of the rotor structure according to the third embodiment. [Figure 12] FIG. 12 is a diagram for explaining a manufacturing method of the rotor structure according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0015] [Embodiment] A rotor structure according to an embodiment includes a shaft and a rotor having a rotor core attached to the shaft, the rotor core being a laminate of magnetic steel sheets having a cylindrical outer circumferential surface and having a through hole penetrating the shaft in the axial direction, a resin core and a permanent magnet disposed in this order from the shaft side toward the radially outward side in the through hole, and the resin core being a resin molded body containing a soft magnetic material. More specific embodiments 1 to 3 are described below.

[0016] [Embodiment 1] Fig. 1 is a cross-sectional view showing a schematic configuration of a rotor structure according to embodiment 1. As shown in Fig. 1, the rotor structure includes a shaft 10 and a rotor 20 attached to the shaft 10. The rotor 20 is composed of a rotor core 21, a permanent magnet 22, and a resin core 23. Specifically, in the rotor structure shown in Fig. 1, the rotor core 21 made of laminated electromagnetic steel sheets is disposed on the outside of the permanent magnet 22, and the resin core 23 mixed with a soft magnetic material is disposed on the inside of the permanent magnet 22.

[0017] The shaft 10 is typically made of metal (for example, stainless steel, etc.). The outer circumferential surface of the shaft 10, which is the bonding surface with the molded resin core 23, is preferably knurled (fleur-de-lis) to improve bonding strength and prevent rotation.

[0018] FIG. 2 is a cross-sectional view showing a rotor core in the first embodiment. As shown in FIG. 2, the rotor core 21 has a cylindrical outer peripheral surface and is a laminate of thin steel plates (for example, electromagnetic steel plates), i.e., an electromagnetic steel plate laminate. The rotor core 21 has outer core portions 212 at multiple locations (four locations in FIG. 2, but not limited to this) on the outer peripheral side, and adjacent outer core portions 212 are connected to each other by connecting portions 213. The rotor core 21 has one through hole 211 surrounded by the outer core portion 212 and the connecting portion 213. The through hole 211 penetrates the rotor core 21 in the axial direction of the shaft 10. That is, the through hole 211 communicates over the entire axial length of the rotor core 21. The rotor core 21 has a resin core 23 formed in a part of the through hole 211. The rotor core 21 is obtained using a core that is press-formed into a predetermined shape from an electromagnetic steel plate having a predetermined thickness. Specifically, rotor core 21 is configured as an electromagnetic steel sheet laminate by stacking a predetermined number of cores in the axial direction and caulking them together. In the rotor structure according to the first embodiment, flux barriers (gaps) 214 are formed in connecting portions 213 of rotor core 21. Flux barriers 214 correspond to portions of through-holes 211 that are not filled with shaft 10, permanent magnets 22, and resin core 23.

[0019] The permanent magnet 22 is rectangular in plan view, specifically a bulk material in the shape of a rectangular parallelepiped. Ferrite magnets, rare earth magnets, etc. can be used as the permanent magnet 22. Rare earth magnets include SmCo5 magnets, Sm2Co 17Permanent magnets such as rare earth iron-based magnets (NdFeB-based magnets and SmFeN-based magnets) can be used. The permanent magnets 22 may be bonded magnets made by mixing and bonding thermosetting resin and magnet powder, or sintered magnets. The permanent magnets 22 may be anisotropic magnets or isotropic magnets. The permanent magnets 22 may be pre-magnetized permanent magnets, or may be magnetized after molding. To prevent the permanent magnets 22 from coming off, it is preferable to form at least one groove in the direction perpendicular to the axial direction of the rotor 20 (the axial direction of the shaft 10) on the surface of the rectangular parallelepiped permanent magnets 22 that contact the resin core 23. Of these, anisotropic SmFeN-based bonded magnets are preferably used. Although the number of permanent magnets 22 shown in FIG. 1 is four, this is not limiting.

[0020] The resin core 23 is a resin molded body containing a soft magnetic material. The soft magnetic material may be a powder primarily composed of iron (iron powder, pure iron powder), or a powder of silicon steel (Fe-Si alloy), Sendust (Fe-Si-Al alloy), Permalloy (Fe-Ni alloy), or the like. The soft magnetic material has a predetermined particle size. The resin contained in the resin molded body together with the soft magnetic material is preferably a thermoplastic resin (e.g., polyamide (PA) resin such as PA12, PA6, or PA66, or polyphenylene sulfide (PPS) resin). If the resin core 23 requires additional heat resistance, heat-resistant nylon (PA6, PA66) or PPS resin can be used instead of PA12. The soft magnetic material is preferably contained in an amount of 40% to 60% by volume and the resin is preferably contained in an amount of 40% to 60% by volume in a 100% by volume resin molded body. If the volume of the soft magnetic material exceeds 60%, the fluidity of the resin material decreases when molding the resin core 23, and the resin core may not be molded well. On the other hand, if it is less than 40%, the ratio of the soft magnetic material decreases, and the resin core may not achieve sufficient saturation magnetic flux density, and may not function adequately as a back yoke. More specifically, the volume of the pure iron powder and the volume of the polyamide 12 (PA12) resin can each be 50%.

[0021] The manufacturing method of the rotor structure according to the first embodiment includes a step of fabricating a resin core 23, which is a resin-molded body containing a soft magnetic material, from a resin material containing a soft magnetic material and a resin. FIG. 3 is a diagram illustrating the manufacturing method of the rotor structure according to the first embodiment. Specifically, as shown in FIG. 3, first, the rotor core 21 is set in the cavity of a mold (not shown), and the shaft 10 and rectangular parallelepiped permanent magnets 22 corresponding to the number of poles are set at predetermined positions within the through holes 211 of the rotor core 21. Next, the resin core 23 is formed in the through holes 211 of the rotor core 21. First, a resin material is prepared by mixing a soft magnetic material having a predetermined particle size with a thermoplastic resin. Preferably, the soft magnetic material is contained in an amount of 40% to 60% by volume and the resin is contained in an amount of 40% to 60% by volume, based on 100% by volume of the resin material. If the volume of the soft magnetic material exceeds 60%, the fluidity of the resin material decreases when molding the resin core 23, which may result in an insufficient molding of the resin core. On the other hand, if the ratio is less than 40%, the ratio of soft magnetic material decreases, and the resin core may not achieve sufficient saturation magnetic flux density, resulting in an insufficient function as a back yoke. More specifically, the volume of pure iron powder and the volume of polyamide 12 (PA12) resin can be used at 50% each. The above mixture ratio is usually maintained in the resin core 23. Next, resin material is injected into the through-holes 211 from one end face side of the rotor core 21, and the resin core 23 is injection-molded. In this way, the molded body shown in FIG. 1 is obtained.

[0022] [Embodiment 2] Fig. 4 is a perspective view showing a schematic configuration of a rotor structure according to embodiment 2. As shown in Fig. 4, the rotor structure includes a shaft 10 and a rotor 20 attached to the shaft 10. The rotor 20 is composed of a rotor core 21, permanent magnets 22, and a resin core 23. Specifically, the rotor structure shown in Fig. 4 has the rotor core 21 made of laminated electromagnetic steel sheets arranged on the outside of the permanent magnets 22, and the resin core 23 mixed with a soft magnetic material arranged on the inside of the permanent magnets 22. The shape of the permanent magnets 22 differs from that of embodiment 1 shown in Fig. 1; the permanent magnets 22 are bonded magnets that are U-shaped in plan view.

[0023] The manufacturing method of the rotor structure according to the second embodiment includes a step of manufacturing a resin core 23, which is a resin molded body containing a soft magnetic material, from a resin material containing a soft magnetic material and a resin. Next, after manufacturing the resin core 23, a step of manufacturing a permanent magnet 22, which is a bonded magnet, from a magnet molding resin material in which a magnetic powder and a thermoplastic resin are mixed, thereby obtaining a rotor. Figures 5-1, 5-2, 6-1, 6-2, 7-1, and 7-2 are diagrams for explaining the manufacturing method of the rotor structure according to the second embodiment. Figure 5-2 is a partially enlarged cross-sectional view of the diagram shown in Figure 5-1, Figure 6-2 is a partially enlarged cross-sectional view of the diagram shown in Figure 6-1, and Figure 7-2 is a partially enlarged cross-sectional view of the diagram shown in Figure 7-1.

[0024] Specifically, first, as shown in Figures 5-1 and 5-2, the rotor core 21 is set in the cavity of a mold (not shown), and the shaft 10 is set at a predetermined position in the through hole 211 of the rotor core 21. Furthermore, to ensure a space for forming the resin core 23, a insert 30 having a shape corresponding to the shape of the permanent magnet 22 is also set.

[0025] The rotor core 21 has a cylindrical outer peripheral surface and is a laminate of thin steel plates (for example, electromagnetic steel plates), i.e., an electromagnetic steel plate laminate. The rotor core 21 has a plurality of (eight in FIG. 5-1 , but not limited to) generally fan-shaped outer core portions 212 on the outer peripheral side, and adjacent outer core portions 212 are connected to each other by connecting portions 213. The rotor core 21 has one through hole 211 surrounded by the outer core portion 212 and the connecting portion 213. The through hole 211 penetrates the rotor core 21 in the axial direction of the shaft 10. That is, the through hole 211 communicates over the entire axial length of the rotor core 21. The rotor core 21 has a resin core 23 formed in a part of the through hole 211. The rotor core 21 is obtained using a core that is press-formed into a predetermined shape from an electromagnetic steel plate having a predetermined thickness. Specifically, rotor core 21 is formed as an electromagnetic steel sheet laminate by laminating a predetermined number of cores in the axial direction and fixing them by caulking.

[0026] The shaft 10 is typically made of metal (for example, stainless steel, etc.). The outer circumferential surface of the shaft 10, which is the bonding surface with the molded resin core 23, is preferably knurled (fleur-de-lis) to improve bonding strength and prevent rotation.

[0027] Next, the resin core 23 is formed in the through-hole 211 of the rotor core 21. First, a resin material is prepared by mixing a soft magnetic material having a predetermined particle size with a thermoplastic resin. The soft magnetic material is preferably contained in an amount of 40% to 60% by volume and the resin is preferably contained in an amount of 40% to 60% by volume, relative to 100% by volume of the resin material. If the volume of the soft magnetic material exceeds 60%, the fluidity of the resin material may decrease when molding the resin core 23, potentially resulting in an insufficient molding of the resin core. On the other hand, if the volume is less than 40%, the proportion of the soft magnetic material decreases, resulting in an insufficient saturation magnetic flux density of the resin core, potentially resulting in an insufficient function as a back yoke. More specifically, the volume of pure iron powder and the volume of polyamide 12 (PA12) resin may each be 50%. The above-mentioned mixing ratio is typically maintained in the resin core 23. Next, a resin material is injected into the through-holes 211 from one end face side of the rotor core 21 to injection-mold the resin core 23. The insert 30 prevents the resin material from flowing into the space for forming the permanent magnets 22, which will be described later.

[0028] The soft magnetic material may be a powder mainly composed of iron (iron powder, pure iron powder), or a powder of silicon steel (Fe-Si alloy), sendust (Fe-Si-Al alloy), permalloy (Fe-Ni alloy), or the like. The soft magnetic material has a predetermined particle size. The resin contained in the resin molded body together with the soft magnetic material is preferably a thermoplastic resin (for example, polyamide (PA) resin such as PA12, PA6, or PA66, or polyphenylene sulfide (PPS) resin). If the resin core 23 requires further heat resistance, heat-resistant nylon (PA6, PA66) or PPS resin can be used instead of PA12.

[0029] Next, a U-shaped space is formed in the area where the insert 30 was removed (see FIGS. 6-1 and 6-2). A permanent magnet 22 (bonded magnet), also U-shaped in plan view, is formed in this U-shaped space. First, a magnet molding resin material is prepared by mixing magnet powder with a predetermined particle size distribution with thermoplastic resin. In 100% by mass of the magnet molding resin material, the magnet powder preferably accounts for approximately 90% by mass and the resin for approximately 10% by mass. This mixture ratio is typically maintained for the permanent magnet 22. Next, the magnet molding resin material is injected and filled into the U-shaped space in the through hole 211 from one end face of the rotor core 21, thereby forming the permanent magnet 22 by injection molding (see FIGS. 7-1 and 7-2). In this way, the molded body shown in FIG. 4 is obtained. The resin core 23 and the permanent magnet 22 can be formed using a so-called two-shot molding technique. This improves workability when forming the resin core 23 and the permanent magnet 22.

[0030] Furthermore, the manufacturing method of the rotor structure according to the second embodiment preferably further includes the steps of producing resin core 23 and bonded magnets as permanent magnets 22 to obtain rotor 20, demagnetizing the obtained rotor 20, and then magnetizing the rotor 20 so that it is magnetized in a predetermined direction from the outer periphery of rotor core 21. That is, after forming permanent magnets 22 (bonded magnets), it is preferable to remove the compact from the mold and demagnetize the compact in advance to remove irregular magnetization. Next, it is preferable to set the demagnetized compact in a magnetizing yoke (not shown) around which a magnetizing coil is wound, and apply a pulse current to the magnetizing coil to magnetize the rotor core 21 so that it is magnetized in a predetermined direction from the outer periphery.

[0031] Here, an example of the rotor structure according to the second embodiment shown in Fig. 4 will be described. In the example, a magnetic field analysis was performed using an 8-pole, 24-slot IPM motor as a model, with the rotor 20 having an outer diameter of φ36 mm, the axial length of the rotor 20 being 40 mm, and the shaft 10 having an outer diameter of φ8 mm. Fig. 8 is a diagram showing a 1 / 8 model of the rotor structure used in the magnetic field analysis. The surface magnetic flux density of the magnet was analyzed with a magnet thickness of T = 3 mm and a distance from the magnet to the shaft of D = 2, 4, and 8 mm. Figure 9 shows the analysis results of the surface magnetic flux density of the magnet in this example. As shown in Figure 9, there was no significant difference between D = 2 and 4 mm. Because the magnet volume increases as the D value decreases, D = 4 mm is preferred in this model from the perspective of magnet cost. Furthermore, the back electromotive force was analyzed with D = 4 mm and T = 1 mm to 4.5 mm. Figure 10 shows the analysis results of the back electromotive force in this example. As shown in Figure 10, it is maximized at T = 2 mm. When evaluating motor characteristics, considering the magnetic path including the surrounding magnetic stator, a T = 2 mm is preferred when evaluating back electromotive force. This model shows that when using rare earth magnetic powder, even if the volume of the bonded magnet mixed with rare earth magnetic powder, which is expensive, is reduced, the magnetic properties are not reduced and the desired magnetic properties are maintained.

[0032] [Embodiment 3] The rotor structure according to the third embodiment is the same as the rotor structure according to the second embodiment. The manufacturing method of the rotor structure according to the third embodiment is also the same as the manufacturing method of the rotor structure according to the second embodiment in that it includes a step of manufacturing a resin core 23, which is a resin molded body containing a soft magnetic material, from a resin material containing a soft magnetic material and a resin. On the other hand, the manufacturing method of the rotor structure according to the second embodiment forms the resin core 23 and then forms the permanent magnets 22 (bonded magnets), whereas the manufacturing method of the rotor structure according to the third embodiment differs in that the resin core 23 is formed after the permanent magnets 22 (bonded magnets). Below, the differences between the third embodiment and the second embodiment will be described, and the same points will not be described again or will be simplified.

[0033] The manufacturing method of the rotor structure according to the third embodiment includes a step of fabricating a permanent magnet 22, which is a bonded magnet, from a magnet molding resin material obtained by mixing magnet powder and a thermoplastic resin. Next, after fabricating the permanent magnet 22, a step of fabricating a resin core 23, which is a resin-molded body containing a soft magnetic material, from a resin material containing a soft magnetic material and a resin, thereby obtaining a rotor. FIGS. 11 and 12 are diagrams illustrating the manufacturing method of the rotor structure according to the third embodiment. Specifically, as shown in FIG. 11, the rotor core 21 is first set in the cavity of a mold (not shown). Furthermore, to ensure a space for forming the resin core 23 after forming the permanent magnet 22 (bonded magnet), a insert is set in the through hole 211 to prevent the magnet molding resin material from flowing into this space. The rotor core 21 and the insert form a U-shaped space, and the permanent magnet 22 (bonded magnet), which is U-shaped in plan view, is formed in this U-shaped space. First, a magnet molding resin material is prepared by mixing magnet powder having a predetermined particle size distribution with a thermoplastic resin. Next, a magnet molding resin material is injected and filled into the U-shaped space in the through-hole 211 from one end face side of the rotor core 21, thereby injection-molding the permanent magnet 22 (see FIG. 11).

[0034] Next, the shaft 10 is set in a predetermined position in the space left by the insert. The resin core 23 is formed in the space between the shaft 10 and the permanent magnet 22. First, a resin material is prepared by mixing a soft magnetic material having a predetermined particle size with a thermoplastic resin. Next, the resin material is injected into the through-hole 211 from one end face side of the rotor core 21, and the resin core 23 is injection molded (see FIG. 12). In this way, the molded body shown in FIG. 4 is obtained. The permanent magnet 22 and the resin core 23 can be formed using so-called two-color molding technology. This improves workability when forming the resin core 23 and the permanent magnet 22.

[0035] Furthermore, the manufacturing method of the rotor structure according to the third embodiment also preferably includes the steps of producing a bonded magnet and a resin core 23 as permanent magnets 22, obtaining rotor 20, demagnetizing the obtained rotor 20, and then magnetizing rotor core 21 so that it is magnetized in a predetermined direction from the outer periphery. That is, after forming resin core 23, it is preferable to remove the molded body from the mold and demagnetize the molded body in advance to remove irregular magnetization. Next, it is preferable to set the demagnetized molded body in a magnetizing yoke (not shown) around which a magnetizing coil is wound, and apply a pulse current to the magnetizing coil to magnetize rotor core 21 so that it is magnetized in a predetermined direction from the outer periphery.

[0036] As described above, in embodiments 2 and 3, thermoplastic resin is used when forming the resin core 23 and the permanent magnet 22. The thermoplastic resin used in the earlier step is preferably selected so that its injection temperature is the same as or higher than that of the thermoplastic resin used in the later step. That is, in embodiment 2, the thermoplastic resin used to form the resin core 23 is preferably selected so that its injection temperature is the same as or higher than that of the thermoplastic resin used to form the permanent magnet 22 (bonded magnet). Furthermore, in embodiment 3, the thermoplastic resin used to form the permanent magnet 22 (bonded magnet) is preferably selected so that its injection temperature is the same as or higher than that of the thermoplastic resin used to form the resin core 23.

[0037] In the rotor structure according to the embodiment, the region radially outward of the permanent magnets (e.g., bonded magnets) is constructed from laminated electromagnetic steel sheets. This outer region is the region through which the magnetic flux that contributes to torque passes and where the magnetic flux changes drastically, so it must be made of a material with high permeability and low loss in the high frequency range. Specifically, the magnetic flux that contributes to torque includes magnetic flux that contributes to reluctance torque when a current is applied to a coil wound around a stator tooth that faces the outer circumferential surface of the rotor via a predetermined cap. The magnetic flux flows from the stator tooth through the laminated body to an adjacent tooth, and magnetic flux that flows from the permanent magnet toward the stator tooth.

[0038] In contrast, the region radially inward of the permanent magnet (e.g., bonded magnet) is constructed with a resin core made of a resin molded body containing a soft magnetic material. This inner region has less magnetic flux fluctuation than a laminated core made of laminated electromagnetic steel sheets, and this region primarily functions as a back yoke for the permanent magnet. For this reason, a soft magnetic material powder with high magnetic permeability is mixed into the resin core to function as a magnetic path. Furthermore, because the resin core is formed by mixing soft magnetic material powder into resin, it can be significantly lighter than a configuration formed with laminated electromagnetic steel sheets. Furthermore, because the resin core contains resin and soft magnetic material, it can have a higher electrical resistance than if this portion were formed with electromagnetic steel sheets. This suppresses the generation of eddy currents and reduces iron loss.

[0039] As described above, the rotor structure according to the embodiment is constructed with laminated electromagnetic steel sheets only in the region radially outward of the permanent magnets, thereby making it possible to reduce the weight of the entire rotor. [Explanation of symbols]

[0040] 10 shaft, 20 rotor, 21 rotor core, 211 through hole, 212 outer core portion, 213 connecting portion, 22 permanent magnet, 23 resin core, 30 insert

Claims

1. a shaft; and a rotor having a rotor core attached to the shaft, the rotor core is an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface, and has a through hole penetrating in the axial direction of the shaft; A resin core and a permanent magnet are disposed in this order in the through hole from the shaft side toward the outside in the radial direction, the resin core is a resin molded body containing a soft magnetic material, The resin core and the permanent magnet are in contact with each other. Rotor structure of an embedded magnet motor.

2. The permanent magnet is a bonded magnet containing resin and magnetic powder. The rotor structure of the magnet embedded motor according to claim 1.

3. The soft magnetic material is a powder containing iron as a main component.

3. A rotor structure for an embedded magnet motor according to claim 1 or 2.

4. A method for manufacturing a rotor structure of an embedded magnet motor, comprising: a shaft; and a rotor having a rotor core attached to the shaft, the rotor core being an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface, and having a through hole penetrating in the axial direction of the shaft, a resin core and a permanent magnet being disposed in this order in the through hole from the shaft side toward the outside in the radial direction, the resin core and the permanent magnet being in contact with each other, a step of producing the resin core, which is a resin molded body containing the soft magnetic material, from a resin material containing the soft magnetic material and resin; A manufacturing method for the rotor structure of an interior magnet motor.

5. The method further includes a step of producing the resin core and a bonded magnet as the permanent magnet to obtain a rotor, demagnetizing the rotor, and then magnetizing the rotor core from the outer periphery in a predetermined direction. A method for manufacturing the rotor structure of the magnet embedded motor according to claim 4.

6. The permanent magnet is a U-shaped bonded magnet.

3. A rotor structure for an embedded magnet motor according to claim 1 or 2.

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