WO2018043026A1

WO2018043026A1 - Surface magnet type motor

Info

Publication number: WO2018043026A1
Application number: PCT/JP2017/028248
Authority: WO
Inventors: 俊幸玉村; 裕一郎田代; 康一斉藤
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2016-08-29
Filing date: 2017-08-03
Publication date: 2018-03-08
Also published as: JPWO2018043026A1; CN109661760A; CN109661760B; JP6667084B2

Abstract

A stator core of a stator has a ring-shaped yoke and multiple teeth radially extending from the inner periphery of the yoke and having circumferentially broadened tooth-tip parts at the tip thereof, and windings are wound around the teeth. A rotor is provided with a rotor core, a shaft, magnets, and a rotor resin part. The multiple magnets held on the rotor core are circumferentially arranged along the outer peripheral surface of the rotor core with a predetermined gap from the tooth-tip parts, and the rotor resin part fixes the multiple magnets to the rotor core. Furthermore, each of the magnets is provided with a first main surface facing the outer peripheral surface of the rotor core and a second main surface facing the tooth-tip part. In this case, the first main surface includes a planar part, and the tooth-tip part and the second main surface include arc-shaped curved surfaces concentric with a magnetic pole surface. In addition, the rotor core and the multiple magnets are integrally formed such that the outer peripheries of the second main surfaces are covered by the rotor resin part.

Description

Surface magnet type motor

The present invention relates to a surface magnet type motor called an SPM motor, and more particularly to a surface magnet type motor in which a magnet having a D-shaped cross section is arranged on the outer periphery of a rotor.

Conventionally, a motor has been proposed in which the gap between the outer peripheral surface of the cylindrical magnet arranged on the outer periphery of the rotor and the inner peripheral surface of the stator is always equal in the circumferential direction, and the inner peripheral surface of the cylindrical magnet is a polygonal column shape. (For example, refer to Patent Document 1). In such a motor of Patent Document 1, the gap is always equally spaced as described above, so that the maximum magnetized state is achieved over the entire circumferential surface of the rotor, and the maximum effective magnetic force is utilized. Furthermore, in this patent document 1, it magnetizes so that one side of an internal peripheral surface may respond | correspond to one magnetic pole. In Patent Document 1, with such a configuration, the density distribution of the magnetic flux flowing between the rotor and the stator is brought close to a sine wave by the cylindrical magnet disposed on the outer periphery of the rotor. This is because the motor rotates smoothly and the cogging torque is reduced. When the cogging torque is reduced, for example, the efficiency of the motor is improved and noise during operation is suppressed. As described above, in Patent Document 1, the cross section of the magnet corresponding to one side of the polygonal column shape is formed in a D shape, thereby approximating the surface magnetic flux waveform to a sine wave waveform and the sound during motor rotation together with the cogging torque. And reduce vibration.

Further, there has been proposed a motor in which a plurality of magnets having a D-shaped cross section are arranged on the outer periphery of the rotor (see, for example, Patent Document 2). In such a motor of Patent Document 2, a magnet insertion part having a restricting body at the opening is formed in the rotor yoke. And the magnet is inserted in the magnet insertion part so that a control body may be fitted in the to-be-engaged part of a magnet. Here, these magnets are formed by cutting out an outer wall surface having the same radius as the outer periphery of the rotor yoke, a flat back wall surface on the opposite side of the outer wall surface, and a restricting body fitted at both ends in the circumferential direction of the outer wall surface. And the engaged portion. In Patent Document 2, with such a configuration, the magnet is reliably held in the rotor, a part of the magnet is exposed to the outer peripheral side of the rotor, and the outer wall surface of the magnet is brought close to the inner surface of the stator to be strong. It is a motor.

Further, there is a surface magnet type motor in which a plurality of arc-shaped magnets are arranged along the outer peripheral surface of the rotor yoke, and a motor that constitutes the rotor is proposed by fixing these magnets to the surface of the rotor yoke by a resin mold. (For example, see Patent Document 3). In such a motor of Patent Document 3, the outer peripheral part of the magnet is not made into a perfect circle with respect to the rotor center, and the radial thickness of the magnet is maximized near the center in the circumferential direction and becomes smaller at the end in the circumferential direction. Yes. And in patent document 3, resin is poured into at least the outer side of the circumferential direction edge part of a magnet, and an axial direction both ends, a magnet is fixed to a rotor yoke, and the rotor is formed.

Also, a motor that is a surface magnet type motor and has chamfered corners of the magnet has been proposed (for example, see Patent Document 4). In such a motor of Patent Document 4, the rotor core is cylindrical, and the surface of the magnet facing the outer peripheral surface of the rotor core is also a curved surface along the outer peripheral surface. And in patent document 4, chamfering is given to the corner | angular part of the radial direction outer side at the circumferential direction both ends. In Patent Document 4, such chamfering is used to efficiently concentrate magnetic flux and increase the demagnetization resistance.

Furthermore, there has been proposed a rotor provided with a plurality of magnets having a D-shaped cross section on the surface and provided with protrusions sandwiching the magnets on the outer peripheral surface of the rotor core (see, for example, Patent Document 5). Furthermore, a groove for adhesive is formed on the rotor core of Patent Document 5.

JP 2008-109838 A Japanese Patent Laying-Open No. 2015-50880 JP 2001-29887A Japanese Patent Laid-Open No. 2015-231253 US Patent Application Publication No. 2002/0067092

The surface magnet type motor of the present invention includes a stator and a rotor that is rotatably arranged on the inner peripheral side of the stator, and holds a plurality of magnets on the surface of the rotor. The stator includes a stator core and a winding. The stator core has a ring-shaped yoke and a plurality of teeth extending in the radial direction from the inner periphery of the yoke and having a tooth tip extending in the circumferential direction at the tip, and windings are wound around the teeth. It has been turned. The rotor includes a rotor core, a shaft, a magnet, and a rotor resin portion. Here, the rotor core holds a plurality of magnets, the shaft extends through the center of the rotor core, and the plurality of magnets are spaced apart from the teeth tip by a predetermined distance along the outer circumferential surface of the rotor core. Are arranged at equal intervals. And a rotor resin part fixes a some magnet to a rotor core.

Furthermore, each of the plurality of magnets includes a first main surface that faces the outer peripheral surface of the rotor core, and a second main surface that faces the tip of the teeth. Here, the first main surface includes a flat surface portion that forms a flat surface, and the tooth tip portion and the second main surface include curved surface portions that are concentric with the magnetic pole surface in a plane orthogonal to the shaft. The rotor core and the plurality of magnets are integrally molded by the rotor resin portion so that the rotor resin portion covers the peripheral edge portion of the second main surface.

According to such a configuration, a magnetic flux having a density distribution close to a sine wave can be generated between the rotor and the stator while securely attaching the plurality of magnets to the rotor core. Therefore, according to the present invention, a surface magnet motor with high torque, high efficiency, and reduced noise can be obtained.

FIG. 1 is a structural diagram showing a cross section of a surface magnet type motor according to an embodiment of the present invention. FIG. 2 is an exploded perspective view schematically showing a main part of the configuration of the SPM motor according to the present embodiment. 3 is a cross-sectional view taken along line XX of the SPM motor of FIG. FIG. 4A is a perspective view of a magnet according to the present embodiment. 4B is a cross-sectional view taken along line YY in FIG. 4A. FIG. 5 is an enlarged view of FIG. 4B. FIG. 6 is a graph showing an outline of the density distribution of the magnetic flux flowing from the magnet. FIG. 7A is a configuration diagram of the rotor. FIG. 7B is a diagram showing a detailed cross-sectional structure of the rotor body. FIG. 7C is a diagram illustrating a configuration of an outer rotor core, a magnet, and a part of the rotor resin portion in the rotor body viewed from the axial direction. FIG. 8 is a diagram showing a detailed structure between adjacent magnets arranged in the rotor core. FIG. 9A is a diagram for explaining the degree of adhesion with which the magnet is in close contact with the magnet holding surface based on the shape of the protrusion and the shape of the magnet in the rotor core according to the present embodiment. FIG. 9B is a diagram for explaining the degree of adhesion in which the magnet is in close contact with the magnet holding surface based on the shape of the protrusion and the shape of the magnet in the rotor core which is a comparative example.

The surface magnet type motor according to the embodiment of the present invention generates a magnetic flux having a density distribution close to a sine wave between the rotor and the stator while securely bringing a plurality of magnets into close contact with the rotor core by the configuration described later. Yes. As a result, the surface magnet motor of the present embodiment achieves higher torque and higher efficiency as well as lower noise.

That is, the conventional method including the above-described technique has the following points to be improved. That is, in the technique as disclosed in Patent Document 1, although a magnetic flux waveform close to a sine wave is obtained, since it is realized by one cylindrical magnet, it includes thin portions as many as the number of poles and is easily damaged. In addition, although the strength is improved by using a permanent magnet using a composite material, since the binder component is included, the magnetic characteristics are low, and it is not suitable for a motor for high torque.

Further, even with the technique as in Patent Document 2, a magnetic flux waveform close to a sine wave is obtained near the center of the magnet. However, since it is necessary to form engaged portions that are recessed inwardly at the both end positions of the magnet, the magnetic flux waveform is greatly disturbed from the sine wave waveform when it is away from the magnet center. For this reason, for example, there is a problem that noise during operation cannot be sufficiently suppressed.

Further, in the technique as in Patent Document 3, since the outer peripheral portion of the magnet is not a perfect circle with respect to the rotor center, the interval between the magnetic pole surface at the stator tooth tip and the outer peripheral surface of the rotor magnet is not constant. For this reason, in the location where the space | interval between both is wide, the magnetized magnetic flux cannot fully be utilized, and it will cause a deterioration of efficiency. Furthermore, the distance from the rotor rotation center to the outer circumference of the magnet decreases as the distance from the center in the circumferential direction of the magnet increases. For this reason, when resin molding using a mold is performed, a paper-like thin resin film is formed in the vicinity of the center in the circumferential direction of the magnet on the outer surface of the magnet. That is, a so-called burr, which is a thin thin piece of resin, is stuck to the magnet surface of the rotor after molding, and it peels off and becomes resin waste, causing problems such as defective rotation. It becomes easy to cause.

The magnet is usually formed by pressing a powdery raw material, followed by firing and molding into a desired shape. At this time, it is very difficult to mold a magnet having a curved surface along the outer peripheral surface of the rotor core as in Patent Document 4 with high accuracy. For example, if expansion or contraction occurs after press molding or after firing, the curvature of the curved surface changes and does not match the curved surface of the rotor core. Therefore, in the case of a configuration in which the curved surface of the magnet is arranged on the outer periphery of the rotor core as in Patent Document 4, the contact portion may be reduced due to a mismatch in curvature due to variations or the like, or in the worst case, contact may be made at a point. Maybe there is. And if the contact part of the curved surface of a magnet and the outer peripheral surface of the rotor core which arranges this is small, the backlash of a magnet may arise. The play of the magnet causes noise and reduces the efficiency of the SPM motor. Furthermore, when the curved surface of the magnet and the outer peripheral surface of the rotor core are in contact with each other at a point, in the subsequent SPM motor assembly process, stress tends to concentrate on the point-contacted portion. As a result, the magnet may be cracked or broken starting from the point contact portion.

Therefore, in the present embodiment, in the magnet held on the surface of the rotor, the inner surface is a flat surface, the outer surface is a curved surface that is concentric with the magnetic pole surface on the stator side, and the peripheral portion of the outer surface is made of resin. It is integrally molded with resin so as to cover it. Thus, according to the present embodiment, it is possible to realize a surface magnet type motor that achieves high torque and high efficiency as well as low noise.

Hereinafter, the surface magnet type motor of the present embodiment will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a structural diagram showing a cross section of a surface magnet type motor 100 according to an embodiment of the present invention. The surface magnet type motor 100 is an inner rotor type brushless motor called an SPM (Surface Permanent Magnet) motor. As shown in FIG. 1, a surface magnet type motor (hereinafter, appropriately referred to as an SPM motor) 100 includes a stator 30 and a rotor 20 that is rotatably disposed around the shaft 21 on the inner peripheral side of the stator 30. It comprises. The rotor 20 holds a plurality of permanent magnets (hereinafter simply referred to as magnets) 10 on the outer peripheral surface thereof.

FIG. 2 is an exploded perspective view schematically showing a main part of the configuration of the SPM motor 100 according to the present embodiment. FIG. 3 is a sectional view of the SPM motor 100 in FIG. is there. In FIG. 2, the surface cut by the XX line is indicated by a one-dot chain line. 2 and 3 show the stator core 31 in the stator 30, the rotor core 22 in the rotor 20, and the plurality of magnets 10 as the main parts.

Hereinafter, as shown in FIG. 1, the direction of A <b> 1 in which the shaft 21 that is the rotation axis extends is referred to as an axial direction. As shown in FIG. 3, the center of the rotation axis of the SPM motor 100 is a center point C when viewed from the axial direction on a plane orthogonal to the axial direction A1. Then, in the plane orthogonal to the axial direction A1, as shown in FIG. 3, the direction of D1 that circulates around the center point C will be described as the circumferential direction, and the direction of D2 spreading from the center C will be described as the radial direction.

First, as shown in FIG. 1, the stator 30 includes a stator core 31 and a winding 33. The stator core 31 is configured by stacking thin iron plates, for example. A winding 33 is wound around the stator core 31 via an insulator 32. Then, the stator core 31 around which the winding 33 is wound is fixed integrally with the other fixing members in the motor case 40, and the stator 30 having a substantially cylindrical outer shape is configured.

As shown in FIGS. 2 and 3, the stator core 31 has a ring-shaped yoke 31y and a plurality of teeth 31t extending in the radial direction from the inner peripheral surface of the yoke 31y.

The plurality of teeth 31t are arranged at equal intervals in the circumferential direction while forming slots 31s, which are openings, between each other. Further, a tooth tip portion 31tp that extends in the circumferential direction is formed at the extended tip portion of each tooth 31t so as to be wider than the extending tooth intermediate portion 31tm. The inner peripheral surface of the tooth tip portion 31tp is a magnetic pole surface 31t1 facing the magnet 10. The magnetic pole surface 31t1 is formed to be a curved surface located on the circumference centered at the center point C in a plane orthogonal to the axial direction. A coil is formed for each tooth 31t by winding the winding 33 around the tooth 31t while passing the winding 33 through the opening space of the slot 31s with respect to the stator core 31 having such a configuration. The winding method of the coil is not particularly limited, and may be distributed winding in which the winding 33 is wound between a plurality of teeth 31t, or concentrated winding in which the winding 33 is wound for each tooth 31t. There may be. Among these, concentrated winding is preferable because it is easy to increase the efficiency of the SPM motor 100.

Further, the number of slots, which is the number of slots 31s, is not particularly limited. For example, when the coil is concentrated winding and the rotor 20 is rotated using a three-phase alternating current, the number of slots is usually a multiple of three. In the above case, the number of slots is 3 or more, and preferably 12 or more. In the present embodiment, an example of a brushless motor in which the number of slots is 12 and the number of magnetic poles of the rotor 20 is 10 is given. Such a 10-pole, 12-slot brushless motor is preferable in that the cogging torque is reduced because the magnetic attractive force acting in the circumferential direction as the rotational direction is offset.

Next, as shown in FIG. 1, the rotor 20 is inserted inside the stator 30 at a predetermined interval in the radial direction from the tooth tip 31 tp. The rotor 20 includes a shaft 21 and a rotor body 20b. The rotor main body 20 b is provided with a rotor core 22, a plurality of magnets 10, and a rotor resin portion 23 around the shaft 21.

The rotor core 22 is configured by laminating thin iron plates having a substantially polygonal outer shape. More specifically, in the present embodiment, as shown in FIG. 1, the rotor core 22 includes an inner rotor core 22s and an outer rotor core 22m. Here, the inner rotor core 22 s is disposed on the inner peripheral side and is fixed to the shaft 21, and the outer rotor core 22 m is disposed on the outer peripheral side and holds the magnet 10. A portion of the rotor resin portion 23 occupies a portion between the inner rotor core 22s and the outer rotor core 22m in the radial direction. The configuration of the rotor main body 20b including the rotor core 22 in this embodiment will be described in detail below.

In such a central portion of the rotor core 22, the shaft 21 extends through the center point C in the stacking direction of the iron plates, that is, in the axial direction. In this way, the rotor core 22 is fixed around the shaft 21. Furthermore, in the outer peripheral part of the rotor core 22 whose outer shape is a polygonal column, a plurality of magnets 10 are arranged at equal intervals in the circumferential direction along the outer peripheral surface, as shown in FIGS. In particular, in the present embodiment, the arrangement configuration is such that the outer circumferential surface in the circumferential direction of each magnet 10 is concentric with the magnetic pole surface 31t1 of each tooth tip 31tp. Here, the outer curved surface of each magnet 10 faces the magnetic pole surface 31t1 in an exposed state. Further, although details will be described below, in the present embodiment, resin molding is performed so that the rotor resin portion 23 is formed using a mold resin in such an arrangement state. By such molding, the plurality of magnets 10 are tightly fixed to the outer peripheral surface of the rotor core 22 so that the rotor core 22 holds the plurality of magnets 10, and the rotor body 20b is formed.

Further, the shaft 21 to which such a rotor body 20 b is fastened is rotatably supported by two bearings 43. The bearing 43 is a bearing having a plurality of small diameter balls. Each bearing 43 has an outer ring fixed to, for example, a stator resin 45 or a metal bracket 46 that molds the stator side.

Further, FIG. 1 shows a configuration example in which the SPM motor 100 has the printed circuit board 48 built in the motor case 40. Components such as a drive circuit are mounted on the printed circuit board 48, and connection lines for applying a power supply voltage and a control signal are also connected.

By supplying a power supply voltage, a control signal, and the like to the SPM motor 100 configured as described above via a connection line, the winding 33 is energized and driven by the drive circuit of the printed circuit board 48. When the winding 33 is driven, a driving current flows through the winding 33 and a magnetic field is generated from the stator core 31. The magnetic field from the stator core 31 and the magnetic field from the magnet 10 of the rotor 20 generate an attractive force and a repulsive force according to the polarities of the magnetic fields, and the rotor 20 rotates in the circumferential direction around the shaft 21 by these forces. To do. As described above, the rotor 20 is a member that can rotate by the interaction with the magnetic force generated by the stator 30, and the rotation of the rotor 20 is transmitted to the outside of the motor via the shaft 21 and converted into mechanical energy. Is done.

Next, the configuration of the outer peripheral surface of the rotor core 22 and the magnet 10 fixed to the outer peripheral surface in the present embodiment will be described.

As described above, the plurality of magnets 10 are fixed to the outer peripheral surface of the rotor core 22 in parallel in the circumferential direction. That is, as shown in FIG. 2, the outer peripheral surface of the rotor core 22 has a polygonal columnar shape in which the magnet holding surfaces 220 for holding the magnets 10 are combined in a polygonal shape. Here, the magnet holding surface 220 is a square plane. The magnets 10 correspond to each other on a one-to-one basis so that one magnet 10 is paired with one magnet holding surface 220. For example, in the present embodiment, since the number of magnetic poles of the rotor 20 is 10, the rotor core 22 has a 10-prism shape, and 10 magnets 10 are arranged on the outer peripheral surface thereof.

Thus, the plurality of magnets 10 are regularly arranged along the circumferential direction of the rotor core 22 so as to cover the outer circumferential surface of the rotor core 22.

4A is a perspective view of the magnet 10 according to the present embodiment, and FIG. 4B is a cross-sectional view taken along line YY of FIG. 4A.

For example, as shown in FIGS. 2 and 4A, the magnet 10 is a substantially hexahedron having two

main surfaces

11 and 12, a side surface 13, and an upper and lower surface 14 that are substantially rectangular. As shown in FIG. 4B, one main surface (first main surface 11) of the magnet 10 includes a peripheral portion 111 provided on the four-side periphery so as to surround the flat portion 110 together with the flat portion 110 forming a flat surface. . The first main surface 11 faces the outer peripheral surface of the rotor core 22, that is, the magnet holding surface 220. On the other hand, the other main surface (second main surface 12) includes a curved surface portion 120 that is curved in an arc shape along the circumferential direction and has a curved surface that does not bend in the axial direction, and further surrounds the curved surface portion 120. A peripheral portion 121 is provided at the four-side periphery. And this 2nd main surface 12 opposes the magnetic pole surface 31t1 of teeth front-end | tip part 31tp. Further, the peripheral edge portion 111 on the first main surface 11 side of the magnet 10 may be chamfered so as to surround the flat surface portion 110. In other words, the first main surface 11 may include a region other than the flat portion 110.

Further, in the present embodiment, the second main surface 12 is also in the shape of the magnet 10 having the peripheral edge 121 as a region other than the curved surface portion 120. In the present embodiment, by providing the peripheral portion 121, in particular, the side portions 121 s that are the peripheral portions 121 on both sides in the circumferential direction, a magnetic flux density that more closely approximates a sinusoidal waveform is obtained, and the magnet 10 in the rotor 20 is obtained. The holding strength is also increased. Details of the side portion 121s will be further described below.

The magnet 10 having such a shape is magnetized in the thickness direction indicated by the normal direction Nv of the flat surface portion 110 in FIG. 4B so that the main surfaces become opposite magnetic poles. That is, in the first main surface 11 and the second main surface 12, if one surface is an S pole, the other surface is an N pole. Further, in the present embodiment, as shown in FIG. 2, the second main surface 12 is composed of two types of combinations of an S pole magnet 10 and a second main surface 12 of an N pole magnet 10. . And each magnet 10 is arrange | positioned at the rotor core 22 so that N pole and S pole may become alternate along the circumferential direction. Thereby, the magnetic flux generated by each magnet 10 flows in the space between the stator core 31 and the rotor core 22 so as to be approximately along the radial direction and the magnetic flux direction is reversed for each magnet 10. The number of magnets 10 and the number of teeth 31t may not correspond one-to-one. Therefore, the entire second main surface 12 of one magnet 10 may not face the magnetic pole surface 31t1 of one tooth 31t.

Further, as shown in FIG. 3, the curved surface portion 120 of the second main surface 12 is a magnetic pole surface of the tooth tip portion 31tp on a surface orthogonal to the axial direction, that is, a surface including the radial direction (a surface along the circumferential direction). It is bent so as to form a concentric arc shape with a predetermined gap G in the radial direction from 31t1. In summary, the SPM motor 100 according to the present embodiment has an outer periphery from the inner peripheral side centered on the center point C of the rotation axis of the rotor core 22 (and thus the SPM motor 100) in a plane orthogonal to the axial direction. The outer peripheral surface of the shaft 21, the curved surface portion 120 of the magnet 10, the magnetic pole surface 31 t 1 of the stator core 31, and the outer peripheral surface of the stator core 31 are arranged concentrically in this order.

On the other hand, the flat portion 110 of the first main surface 11 is a plane parallel to the axial direction without bending in the circumferential direction and the axial direction. Each of the magnets 10 is arranged on the outer peripheral surface of the rotor core 22 so that the flat portion 110 is in close contact with the magnet holding surface 220 of the rotor core 22.

As described above, in the present embodiment, the cross-section of the outer peripheral surface of the rotor core 22 is substantially polygonal, thereby achieving easy positioning of the magnet 10. Furthermore, the magnet holding surface 220 and the magnet 10 on the outer peripheral surface of the rotor core 22 both have a flat portion. In other words, after the magnet 10 is press-molded or fired, it is a flat surface unlike a curved surface whose curvature is likely to change. Therefore, even if expansion or contraction occurs, the flat state can be easily maintained. Thus, by providing the flat portion, the magnet 10 can be brought into contact with the magnet holding surface 220 while maintaining a large area. As a result, the magnet 10 having the flat portion 110 that can be manufactured easily and with high accuracy is realized as compared with a conventional magnet having a curved surface that comes into contact with the rotor core. Furthermore, since the contact portion of the magnet 10 with respect to the magnet holding surface 220 of the rotor core 22 can be increased, the magnet 10 can be more securely fixed to the magnet holding surface 220, and the play of the magnet 10 can be easily suppressed. As a result, noise during operation of the SPM motor 100 is reduced and efficiency is improved.

FIG. 5 is an enlarged view of FIG. 4B. In the magnet 10 in the present embodiment, the curved surface portion 120 and the flat surface portion 110 are arranged at positions corresponding to each other as described above within the range indicated by the central angle θ4 in FIG. Next, regarding the basic characteristics of the SPM motor 100 using the magnet 10 based on such a configuration, first, the motor characteristics in the range indicated by the central angle θ4 in FIG. 5 will be described.

As shown in FIG. 5, when the magnet 10 is viewed from the normal direction Nv of the flat surface portion 110 in the range indicated by the central angle θ <b> 4, all or most of the curved surface portion 120 overlaps with the flat surface portion 110. Therefore, the thickness of the magnet in the normal direction Nv changes along the circumferential direction so as to decrease as the distance from the central portion of the magnet 10 increases. Specifically, as shown in FIG. 5, it has a D-shaped cross section, and the thickness T in the radial direction of the central portion of the magnet 10 is the largest, and is thinner toward the end portion.

Here, the thickness of the magnet affects the magnitude of the magnetic flux generated by the magnet. That is, the greater the magnet thickness, the greater the magnetic flux. Therefore, also in the magnet 10, the magnetic flux generated from the central portion is usually larger than the magnetic flux generated from the end portion. That is, in FIG. 6, the waveform of the sine wave having the largest central portion is shown by a solid line, but the magnetic flux density of the magnet 10 has a distribution close to such a sine wave waveform. Therefore, the rotation of the rotor 20 becomes smooth, and the cogging torque is reduced. Further, when the magnetic flux density has a distribution close to a sine wave, the waveform of the induced voltage is also close to a sine wave. Therefore, the torque ripple that is the fluctuation range of the torque is reduced. That is, the magnet 10 in the present embodiment includes a curved surface portion 120 and a flat surface portion 110 that face each other, thereby forming a D-shaped cross-sectional shape. In the present embodiment, such a shape of the magnet 10 and the SPM motor 100 using the magnet 10 are used to achieve high efficiency and low noise. On the other hand, when the thickness of the magnet is constant, the magnetic flux density has a distribution close to a rectangular wave, as indicated by a broken line in FIG. FIG. 6 is a graph showing an outline of the density distribution of the magnetic flux flowing from the magnet 10.

Furthermore, as shown in FIG. 4B, in the present embodiment, in order to realize a magnetic flux density closer to a sine wave, the peripheral portions 121 on both sides in the circumferential direction are chamfered on the second main surface 12 side of the magnet 10. The side portion 121s has a different shape. That is, the 2nd main surface 12 is provided with two side parts 121s arrange | positioned so that at least the curved surface part 120 may be clamped by chamfering. In this case, as shown in FIG. 5, an acute angle θ2 formed between an arbitrary tangent L2 of the side portion 121s and the flat surface portion 110 is an acute angle θ1 formed between an arbitrary tangent L1 of the curved surface portion 120 and the flat surface portion 110. The side portion 121s is formed so as to be larger. That is, in this embodiment, the thickness of the end portion of the magnet 10 is further reduced by arranging the side portion 121s as described above. In other words, the amount of change in thickness that decreases as the distance from the center of the magnet 10 increases so that the amount of change outside the center angle θ4 is larger than the amount of change in the range indicated by the center angle θ4 in FIG. In addition, the side portion 121s is used. Further, from another viewpoint, the radial distance Dc from the center point C to the curved surface portion 120 in the range indicated by the center angle θ4 in FIG. 5 is constant, whereas the side portion 121s from the center point C is constant. The distance Ds in the radial direction becomes smaller as the side surface 13 is approached.

That is, as a characteristic of a sine wave that repeats positive and negative peaks in a wavy shape, for example, the amount of change in the middle of the positive and negative peaks such as Sin 180 ° is larger than the amount of change around the peak such as Sin 90 °. In the present embodiment, by reducing the thickness of the side portion 121s, the end portion of the magnet 10 corresponding to the middle of the positive / negative peak of the sine wave is compared with the central portion of the magnet 10 corresponding to the periphery of the peak of the sine wave. The amount of change in which the thickness is reduced is increased to approximate the sine wave characteristic. Therefore, the magnetic flux density of the magnet 10 is also closer to a sine wave.

The side portion 121s may be a flat surface, a curved surface, or may include a flat surface and a curved surface. In particular, by making the side portion 121s a flat surface, it can be approximated to the vicinity of Sin 180 ° that changes linearly, and can be processed and manufactured more easily than a curved surface. Further, in the present embodiment, a small curved surface as a so-called fillet (chamfering) is further included from the side portion 121s at the more circumferential end portion as shown by the end portion 121f in FIG. 4B. Then, by rounding the end, scratches and damage due to sharp corners are prevented. Thus, in the circumferential direction, it is preferable to provide the planar side portion 121s between the curved surface portion 120 and the end portion 121f provided with a fillet having a smaller diameter than the curved surface portion 120.

Further, in the present embodiment, in order to make the magnetic flux density of the magnet 10 close to a sine wave, the width of the side portion 121s in the circumferential direction is set as follows in terms of manufacturing. That is, it is preferable to set the width of the side portion 121s so that the central angle θ4 of the curved surface portion 120 is 50 to 80% of the central angle θ3 of the second main surface 12. This is because the magnetic flux density of the magnet 10 becomes closer to a sine wave. The central angle θ4 is more preferably 65 to 75% of the central angle θ3 of the second major surface 12. That is, in the second main surface 12, the ratio of the length in the circumferential direction occupied by the curved surface portion 120 is in a range from half to three-quarters of the length of the second main surface 12, and the other side portions 121s are the other. What is necessary is just to comprise so that it may occupy.

The central angle θ3 of the second main surface 12 is set according to the number of magnets 10 (number of rotor poles) fixed to the outer peripheral surface. For example, when the rotor has 10 poles, the central angle θ3 is approximately 36 ° (= 360 ° / 10).

Further, in the present embodiment, as shown in FIG. 4B, the pair of side surfaces 13 are inclined planes so that the distance on the curved surface part 120 side is wider than the distance on the flat surface part 110 side. That is, the pair of side surfaces 13 have a shape that is inclined so as to be closer to the central direction of the magnet 10 as the plane portion 110 is approached in a plane orthogonal to the axial direction. Thereby, in addition to the side portion 121 s, the side surface 13 becomes thinner as it goes to the circumferential end portion of the magnet 10. In the present embodiment, such a side surface 13 is also used to realize a magnetic flux density that is closer to a sine wave.

The magnetic flux generated by the magnet 10 is preferably oriented along the normal direction Nv of the flat portion 110. This is because the magnetic flux tends to have a magnitude corresponding to the thickness of the magnet 10 in the normal direction Nv. That is, by changing the thickness of the magnet 10 in the normal direction Nv along the circumferential direction, the magnitude of the magnetic flux flowing into the magnetic pole surface 31t1 can be changed along the circumferential direction. Therefore, it is easy to control the distribution of the magnetic flux density of the magnet 10 to a desired shape (in this case, a sine wave). The orientation of the magnetic flux can be controlled, for example, by magnetizing after obtaining the orientation of the magnetic material when the magnet is manufactured.

The material of the magnet 10 is not particularly limited as long as it is a conventionally known material used for the SPM motor 100. For example, as the magnet 10, a ferrite magnet, a neodymium magnet, a samarium cobalt magnet, or the like is used. Among these, ferrite magnets using iron oxide as a main raw material are preferable in terms of cost. These magnets are relatively easy to break. On the other hand, in the present embodiment, the magnet 10 and the magnet holding surface 220 of the rotor core 22 are brought into contact with each other as described above, and the magnet 10 is attached using the mold resin that becomes the rotor resin portion 23. The fixed structure prevents damage to the magnet 10. That is, if the shape adopted in the present embodiment is used, what has conventionally been point contact can be made surface contact. Therefore, since the contact area of the magnet 10 increases, stable fixation can be realized.

Next, the detailed configuration of the rotor body 20b including the rotor resin portion 23 will be described.

FIG. 7A is a configuration diagram of the rotor 20 configured as described above. FIG. 7B is a diagram showing a detailed cross-sectional structure of the rotor body 20 b including the rotor core 22 and the rotor resin portion 23. FIG. 7C is a diagram showing a configuration of the outer rotor core 22m, the magnet 10, and a part of the rotor resin portion 23 in the rotor body 20b as viewed from the axial direction.

First, as shown in FIG. 7A, a shaft 21 is inserted in the center of the rotor body 20b. In the rotor body 20b, the rotor resin portion 23 is formed by molding a predetermined portion with resin.

As shown in FIG. 7A, the rotor resin portion 23 includes an inter-magnet resin portion 231 and an end plate resin portion 232 with the curved surface portion 120 of the magnet 10 exposed, as shown in FIG. 7A. . Here, the end plate resin portion 232 is provided in a disc shape at both axial end portions of the rotor body 20b, and is disposed so as to sandwich the magnet 10 in the axial direction. The inter-magnet resin portion 231 is provided between the respective magnets 10 in the circumferential direction, and connects the end plate resin portions 232 with resin in the axial direction.

Furthermore, in the present embodiment, as shown in FIG. 7B, the rotor core 22 is formed with a through hole 22t. The through hole 22t is a hole that penetrates the rotor core 22 in the axial direction, and has an annular shape in the radial direction. That is, the through hole 22t is disposed so as to extend the inside of the rotor core 22 as a cylindrical space from one end face to the other end face. The resin of the rotor resin portion 23 is also filled in such a through hole 22t to form an internal resin portion 233 that forms a part of the rotor resin portion 23. Since the inner resin portion 233 has a cylindrical shape, the rotor core 22 is separated into an inner rotor core 22s and an outer rotor core 22m, as can be seen from FIG. 1 and FIG. 7A. The internal resin portion 233 is made of a resin material that is an electrical insulator. Therefore, in the rotor core 22, the inner rotor core 22 s and the outer rotor core 22 m are electrically insulated and separated by the inner resin portion 233. In the present embodiment, by including such a configuration, the electrical impedance of the rotor 20 is increased, and the occurrence of electrolytic corrosion in the bearing is suppressed.

As described above, the rotor resin portion 23 includes the pair of end plate resin portions 232 disposed on both end surfaces of the rotor core 22, the internal resin portion 233 disposed in a cylindrical shape inside the rotor core 22, and the surface of the rotor core 22. Is formed by integrally joining a plurality of inter-magnet resin portions 231 arranged at equal intervals in the circumferential direction. Such a rotor resin portion 23 is formed, for example, by resin molding as follows. That is, the rotor core 22 and the plurality of magnets 10 are arranged in a cylindrical mold. Then, after filling the mold with the thermosetting resin, the thermosetting resin is cured by the heat energy of the mold. By the resin molding based on such a process, the rotor main body 20b in which the inner rotor core 22s, the outer rotor core 22m, and the plurality of magnets 10 are fixed in a predetermined arrangement state is formed. That is, since the end plate resin portions 232 on both sides are connected to each other via the internal resin portion 233 and the inter-magnet resin portion 231, this structure allows the inner rotor core 22s, the outer rotor core 22m, and the respective magnets 10 to be located on both sides. It is fixed so as to be sandwiched between the end plate resin portions 232.

In the present embodiment, each member of the rotor body 20b is fixed by resin in such a process, so that the fixing work is not required and the number of assembling steps and the assembly time are not required as compared with the fixing method using screws or adhesives. Is also shortened. Moreover, in this Embodiment, since each member of the rotor main body 20b is integrally couple | bonded with resin within a metal mold | die, a dimensional accuracy etc. can be ensured easily. Further, in the present embodiment, the structure is such that the end plate resin parts 232 on both sides are connected to each other via the internal resin part 233 and the inter-magnet resin part 231, thereby enabling the rotor core 22 and the magnet to react to an axial external force. The holding strength of 10 is increased.

In particular, in detail with respect to the fixing of the magnet 10, the peripheral portion 121 provided around the curved surface portion 120 of the magnet 10 is used in the present embodiment. As shown in FIGS. 4A and 4B, the peripheral edge 121 is a peripheral edge that is thinner than the curved surface 120. In the present embodiment, the resin of the rotor resin portion 23 covers the peripheral portion 121 so as to hide the peripheral portion 121 of the magnet 10 with respect to the magnet 10. More specifically, the end plate resin portion 232 covers both peripheral edge portions 121 at the axial end portion of the magnet 10. Then, as shown in FIG. 7C, the inter-magnet resin portion 231 covers both peripheral edge portions 121 of the radial end portion of the magnet 10, that is, the side portion 121s. Thus, the magnet 10 is being fixed to the outer peripheral surface of the outer rotor core 22m by covering the peripheral part 121 of the magnet 10 with resin. In particular, during rotation, a centrifugal force is generated outward in the radial direction with respect to the magnet 10, but this centrifugal force is also compared with the holding by the end plate resin portion 232 only by covering the side portion 121s with resin. The strength against can be increased.

As described above, in the present embodiment, screws and adhesives are not used, and the magnet 10 is fixed to the rotor core 22 only by fixing the peripheral portion 121 of the magnet 10 with resin. For example, the first main surface 11 of the magnet 10 is in direct contact with the magnet holding surface 220 of the outer rotor core 22m without any intervention. Further, since direct contact is made in this way, a decrease in permeance can be suppressed as compared with a method in which an adhesive is interposed, and a decrease in efficiency can be suppressed accordingly.

FIG. 8 is a diagram showing a detailed structure between adjacent magnets 10 arranged on the rotor core 22.

As shown in FIG. 8, a protrusion 221 is formed on the outer peripheral surface of the outer rotor core 22m in order to determine the mounting position of the magnet 10. The protruding portions 221 protrude further outward from the outer peripheral surface of the outer rotor core 22m, and are formed to be the same number as the magnets 10 at equal intervals in the circumferential direction. As described above, the protrusions 221 are arranged so as to determine the attachment positions of the plurality of magnets 10, and the magnet holding surface 220 is formed between the adjacent protrusions 221. Thereby, the plurality of magnets 10 can be fixed to the outer peripheral surface of the rotor core 22 at equal intervals. Therefore, the deviation of the density distribution of the magnetic flux flowing from the individual magnets 10 toward the stator 30 is reduced, so that the efficiency of the SPM motor 100 is further improved and noise is reduced. Thus, the protrusions 221 are installed between the adjacent magnet holding surfaces 220, and the magnet 10 is fixed between the adjacent protrusions 221.

In particular, in the present embodiment, the protrusion 221 of the rotor core 22 has a tapered shape with a tapered width. That is, as shown in FIG. 8, the circumferential width of the protrusion 221 is such that the outer peripheral side is narrower than the inner peripheral side that is the root. Furthermore, the shape of the side surface 13 of the magnet 10 is also matched to the shape of the protrusion 221, and the side surface 13 is narrowed so that the circumferential width of the magnet 10 becomes narrower from the side portion 121 s toward the planar portion 110 in the radial direction. Forming. In the present embodiment, since the shape of the protruding portion 221 and the side surface 13 of the magnet 10 is used, the distance between the distal end portions of the adjacent protruding portions 221 with respect to the circumferential width Wb of the planar portion 110 of the magnet 10 is set. The circumferential width Wp at is sufficiently wide. Simply put, the outer opening of the width Wp of the magnet holding surface 220 is set to be wide in the circumferential direction with respect to the bottom of the width Wb of the magnet 10. That is, since the outer opening is wide, the magnet 10 can be easily inserted into the magnet holding surface 220, and further, the magnet 10 can be disposed so as to be in close contact with the magnet holding surface 220 after the insertion.

Furthermore, in order to improve the adhesion between the magnet 10 and the magnet holding surface 220, grooves 222 cut out inward are provided on both sides of the base of the protrusion 221 in the outer rotor core 22m. Next, the groove 222 provided in the outer rotor core 22m will be described. FIG. 9A is a diagram for explaining the degree of adhesion with which the magnet 10 is in close contact with the magnet holding surface 220 based on the shape of the protrusion on the rotor core 22 and the shape of the magnet 10. FIG. 9B shows a comparative example compared with FIG. 9A. Specifically, FIG. 9A shows the periphery of the protrusion 221 provided with the groove 222 in this embodiment, and FIG. 9B shows the periphery of the protrusion 921 not provided with a groove as a comparative example. Yes.

As described above, the rotor core 22 is configured by laminating thin iron plates having a desired shape. Moreover, these iron plates are made into the desired shape by punching out the raw iron plate by punching. In such a punching process, the corner portion is not usually a square shape, but strictly a curved shape. For this reason, the corner portion 922 from the protrusion 921 to the magnet holding surface 920 shown in the comparative example of FIG. 9B also has a curved shape as illustrated. On the other hand, the size of the magnet 10 and the rotor core 22 inevitably varies. For this reason, for example, when the magnet 10 varies so as to be large, the peripheral edge 111 of the magnet 10 comes into contact with the corner 922 as shown in the comparative example of FIG. 9B. As a result, a gap 929 as shown in the comparative example of FIG. 9B is formed between the flat portion 110 of the magnet 10 and the magnet holding surface 920, and the magnet 10 does not adhere to the magnet holding surface 220.

Therefore, in this embodiment, by providing the groove 222, the amount of bulge of the curved corner 922 as in the comparative example is suppressed. That is, in the punching process, punching is performed so that the grooves 222 are formed on both sides of the base of the protrusion 221. Thereby, with the formation of the groove 222, the bulge amount of the corner portion 922 in the comparative example is also reduced. As a result, even if the magnet 10 varies so as to become large, the magnet 10 does not come in contact with the vicinity of the base of the protruding portion 221, and the magnet 10 is placed on the magnet holding surface like the contact surface 229 shown in FIG. 9A. 220 can be securely attached to 220.

Further, as described above, in order to make the fixing of the magnet 10 more reliable, as shown in FIG. 8, the inter-magnet resin portion of the rotor resin portion 23 on the second main surface 12 side so as to straddle the adjacent magnets 10. 231 is arranged. The inter-magnet resin portion 231 is disposed so as to cover at least a part of the two side portions 121s facing each other of the adjacent magnets 10. Thereby, at least a part of the space 25 having a substantially triangular cross section formed by the two side parts 121s facing each other is filled with the resin part 231 between the magnets. That is, since the dispersion | variation in the space | interval of the stator 30 and the rotor 20 becomes small, the rotational load by the space 25 is suppressed, rotation of the rotor 20 becomes smoother, and the efficiency of the SPM motor 100 further improves. From the same viewpoint, the inter-magnet resin portion 231 is disposed so as not to protrude from the substantially triangular space 25.

In particular, in the present embodiment, since the thickness of the magnet 10 at the side portion 121s is reduced, the space 25 is widened compared to the case where the side portion 121s is not provided, and the radial thickness of the inter-magnet resin portion 231 is reduced. Can be increased. Therefore, since the thickness in the radial direction of the inter-magnet resin portion 231 can be sufficiently secured, the strength against the force acting on the radially outer side such as centrifugal force can be sufficiently secured. In addition, it is possible to prevent the resin of the inter-magnet resin portion 231 from being thinned like paper. That is, when the resin becomes paper-like, it becomes easy to be torn or peeled off, and it becomes a cause of trouble such as fine resin scraps that stop the rotation of the rotor 20. On the other hand, in this embodiment, since the resin does not become paper, such a problem can be prevented.

Thus, in this Embodiment, since it is set as the structure which provided the side part 121s in the magnet 10, while achieving the magnetic flux density close | similar to a sine wave, further suppressing generation | occurrence | production of the resin scrap, resin between magnets The holding strength of the magnet 10 by the part 231 can also be ensured.

In the present embodiment, the number of poles of the rotor (the number of magnets 10) has been described as 10. However, the number of poles is not particularly limited. As the number of poles increases, the deviation of the magnetic flux density entering the stator is reduced. Therefore, the number of poles is preferably multipolar from the viewpoint of dispersing electromagnetic force. Further, the cogging torque can be suppressed by appropriately combining the number of poles and the number of slots. The upper limit of the number of poles is determined by the motor specifications, particularly the motor rating. Specifically, the number of poles is, for example, four or more. Especially, from said viewpoint, it is preferable that the number of poles is 8 or more, and it is more preferable that it is 10 or more. In the illustrated example, the number of poles is 10 (10 poles). When the rotor 20 has 10 poles and the rotor 20 is rotated using a three-phase alternating current, the inner diameter of the stator 30 may be distorted during the operation of the SPM motor 100, and the stator 30 may vibrate in an annular shape. The ring vibration of the stator 30 can contribute to noise. However, according to the present embodiment, the cause of noise other than the ring vibration of the stator 30 is easily eliminated, and as a result, noise during operation of the SPM motor 100 is suppressed.

As described above, the number of poles is preferably multipolar from the viewpoint of dispersing electromagnetic force. On the other hand, as the number of magnets 10 increases, the mounting position easily shifts, and it is difficult to mount a large number of magnets 10 on the outer peripheral surface of the rotor core 22 with high accuracy. Therefore, it is more effective to provide the protrusions 221 as the number of poles is larger. In the present embodiment, the larger the number of poles, the closer the outer peripheral surface of the rotor core 22 is to a smooth arc. This is because the outer peripheral surface includes a flat magnet holding surface 220 corresponding to the flat portion 110 of the magnet 10. When the outer peripheral surface is close to an arc, the rotation of the rotor 20 becomes smooth and noise is reduced. Thus, the magnet 10 according to the present embodiment is particularly suitable for use in the rotor 20 having a large number of poles.

According to the surface magnet type motor of the present invention, a magnetic flux having a density distribution close to a sine wave can be generated between the rotor core and the stator core. Therefore, it is particularly effective for motors mounted on home appliances that require low noise and high efficiency.

DESCRIPTION OF SYMBOLS 10 Magnet 11 1st main surface 12 2nd main surface 13 Side surface 14 Upper and lower surfaces 20 Rotor 20b Rotor main body 21 Shaft 22 Rotor core 22m Outer rotor core 22s Inner rotor core 22t Through-hole 23 Rotor resin part 25 Space 30 Stator 31 Stator core 31s Slot 31t Teeth 31y Yoke 31t1 Magnetic pole surface 31tm Teeth intermediate part 31tp Teeth tip part 32 Insulator 33 Winding 40 Motor case 43 Bearing 45 Stator resin 46 Metal bracket 48 Printed circuit board 100 Surface magnet type (SPM) motor 110

Flat part

111, 121 Peripheral part 120 Curved surface Portion 121 s

Side portion

220, 920

Magnet holding surface

221, 921 Projection portion 222 Groove 229 Contact surface 231 Inter-magnet resin portion 232 Plate resin portion 233 inside the resin 922 corner 929 gap

Claims

A surface magnet type motor comprising a stator and a rotor rotatably disposed on an inner peripheral side of the stator, and holding a plurality of magnets on a surface of the rotor;
The stator is
A stator core having a ring-shaped yoke and a plurality of teeth each having a tooth tip portion extending radially from the inner periphery of the yoke and extending in the circumferential direction at the tip portion;
A winding wound around the teeth,
The rotor is
A rotor core holding the plurality of magnets;
A shaft extending through the center of the rotor core;
The plurality of magnets arranged at equal intervals in the circumferential direction along the outer peripheral surface of the rotor core, with a predetermined interval from the tooth tip.
A rotor resin portion for fixing the plurality of magnets to the rotor core,
Each of the plurality of magnets includes a first main surface that opposes the outer peripheral surface of the rotor core, and a second main surface that opposes the tooth tip.
The first main surface includes a plane portion forming a plane,
The teeth tip portion and the second main surface include a curved surface portion forming a concentric arc shape,
A surface magnet type motor in which the rotor core and the plurality of magnets are integrally molded by the rotor resin portion so that the rotor resin portion covers a peripheral edge portion of the second main surface.
The second main surface has the curved surface portion and two side portions arranged to sandwich the curved surface portion,
2. The surface magnet type motor according to claim 1, wherein the radial distance from the center of the rotor to the side portion decreases as the distance from the circumferential end of the magnet decreases.
The surface magnet type motor according to claim 2, wherein an acute angle formed between an arbitrary tangent of the side portion and the flat portion is larger than an acute angle formed between an arbitrary tangent of the curved portion and the flat portion. .
The surface magnet type motor according to claim 2, wherein the rotor resin portion is disposed so as to cover at least a part of the side portion with respect to the second main surface.
The surface magnet type motor according to claim 1, wherein a magnetic flux is oriented along a normal direction of the plane portion.
2. The surface magnet type motor according to claim 1, wherein the outer peripheral surface of the rotor core has a magnet holding surface corresponding to the flat portion on a one-to-one basis.
2. The surface magnet type motor according to claim 1, wherein the outer peripheral surface of the rotor core has a protrusion that defines a mounting position of each of the plurality of magnets.
The surface magnet type motor according to claim 7, wherein grooves formed on the inside are provided on both sides of the protrusion.
The number of poles of the rotor is 10,
The surface magnet type motor according to claim 1, wherein the stator has 12 slots.