Rotor and motor

Abstract

This rotor is provided with a rotor core having a plurality of first holes and a plurality of second holes and a plurality of first permanent magnets respectively disposed in the plurality of first holes. The plurality of first holes and the plurality of second holes are provided radially about the rotational axis. The plurality of first holes each extend in the radial direction of the rotor core. The length of each of the plurality of second holes in the radial direction of the rotor core is smaller than the length of each of the plurality of first holes in the radial direction of the rotor core. Each of the plurality of second holes is located closer to the inner side in the radial direction of the rotor core with respect to a first hole of the plurality of first holes, said first hole being adjacent to a second hole in the circumferential direction of the rotor core, and has a projection portion projecting toward the first hole adjacent to the second hole in the circumferential direction of the rotor core.

Description

[Technical Field]

[0001] The present disclosure relates to a rotor and an electric motor including the rotor, and more particularly to a rotor of an embedded permanent magnet type in which permanent magnets are arranged in an iron core, and an electric motor including the rotor. [Background technology]

[0002] Electric motors are used in a variety of electrical appliances, including household and industrial equipment. A well-known example of an electric motor is an interior permanent magnet (IPM) motor, which has a rotor with a permanent magnet embedded in the iron core. In addition to the magnetic torque from the permanent magnet embedded in the iron core, an IPM motor can also generate reluctance torque due to the unevenness of the magnetic resistance generated in the iron core. This allows for the realization of a compact, highly efficient motor.

[0003] Conventionally, as a rotor for an IPM motor, an IPM rotor has been known which has an iron core with multiple first magnet arrangement holes and multiple second magnet arrangement holes arranged alternately in the circumferential direction, a first permanent magnet arranged in the first magnet arrangement hole and whose magnetic poles are oriented in the circumferential direction of the iron core, and a second permanent magnet arranged in the second magnet arrangement hole and whose magnetic poles are oriented in the radial direction of the iron core (for example, Patent Document 1).

[0004] However, in conventional IPM rotors, there is a problem that the area of ​​the iron core through which the magnetic flux of the first permanent magnet can pass is small between adjacent first and second permanent magnets, so the second magnet placement hole interferes with the magnetic flux of the first permanent magnet, reducing the interlinkage magnetic flux that links with the stator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-275419 Summary of the Invention

[0006] The present disclosure has been made to solve such problems, and has an object to provide a rotor and an electric motor that can increase the interlinkage magnetic flux.

[0007] In order to achieve the above-mentioned object, one aspect of a rotor according to the present disclosure comprises an iron core having a plurality of first holes and a plurality of second holes, a plurality of first permanent magnets respectively arranged in the plurality of first holes, and a rotating shaft fixed to the iron core, wherein the plurality of first holes and the plurality of second holes are arranged radially around the rotating shaft, each of the plurality of first holes extends radially around the iron core, the radial length of the iron core at each of the plurality of second holes is smaller than the radial length of the iron core at each of the plurality of first holes, and each of the plurality of second holes is located radially inward of the iron core relative to a first hole among the plurality of first holes that is circumferentially adjacent to the second hole, and has a protrusion that protrudes toward the second hole and the first hole that is circumferentially adjacent to the iron core.

[0008] Furthermore, one aspect of an electric motor according to the present disclosure includes one aspect of the rotor described above, and a stator arranged opposite the rotor via an air gap and generating a magnetic force acting on the rotor.

[0009] According to the present disclosure, the magnetic flux linkage can be increased. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of an electric motor according to an embodiment; [Figure 2] 1 is a cross-sectional view of an electric motor according to an embodiment. [Figure 3] FIG. 2 is a cross-sectional view of a rotor according to an embodiment. [Figure 4] 2A and 2B are an enlarged plan view showing a part of a rotor according to an embodiment, and a cross-sectional view taken along line AA of the enlarged plan view. [Figure 5] FIG. 10 is an enlarged plan view showing a part of the rotor of Comparative Example 1. [Figure 6]FIG. 10 is an enlarged plan view showing a part of the rotor of Comparative Example 2. [Figure 7] FIG. 2 is an enlarged plan view showing a portion of the rotor according to the embodiment. [Figure 8] FIG. 10 is an enlarged plan view showing a part of a rotor according to Modification 1. [Figure 9] FIG. 10 is an enlarged plan view showing a part of a rotor according to a second modification. [Figure 10] FIG. 11 is an enlarged plan view showing a part of a rotor according to a third modification. [Figure 11] FIG. 10 is an enlarged plan view showing a part of a rotor according to a fourth modification. [Figure 12] FIG. 10 is an enlarged plan view showing a part of a rotor according to a fifth modification. [Figure 13] FIG. 13 is an enlarged plan view showing a part of a rotor according to a sixth modification. [Figure 14] FIG. 13 is a partial cross-sectional view of a rotor according to a seventh modification. [Figure 15] FIG. 13 is a partial cross-sectional view of a rotor according to an eighth modification. [Figure 16] FIG. 13 is a partial cross-sectional view of a rotor according to a ninth modification. [Figure 17] FIG. 23 is an enlarged plan view showing a part of a rotor according to a tenth modification. [Figure 18] FIG. 20 is an enlarged plan view showing a part of a rotor according to an eleventh modification. [Figure 19] FIG. 23 is an enlarged plan view showing a part of a rotor according to a twelfth modification. [Figure 20] FIG. 23 is an enlarged plan view showing a part of a rotor according to a thirteenth modification. [Figure 21] FIG. 23 is a partial cross-sectional view of a stator in an electric motor according to a fourteenth modification. [Figure 22] FIG. 20 is a cross-sectional view of a rotor according to a fifteenth modification. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, components, the arrangement and connection of the components, the steps and the order of the steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the superordinate concept of the present disclosure will be described as optional components.

[0012] Furthermore, each drawing is a schematic diagram and is not necessarily a precise illustration. In each drawing, substantially the same components are denoted by the same reference numerals, and redundant explanations will be omitted or simplified.

[0013] (Embodiment) First, the schematic configuration of an electric motor 1 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view of the electric motor 1 according to an embodiment. Fig. 2 is a cross-sectional view of the electric motor 1. Fig. 2 shows a cross section taken along a plane perpendicular to a rotating shaft 10.

[0014] 1 and 2, the electric motor 1 includes a rotor 2 and a stator 3. The electric motor 1 is an inner rotor type motor in which the rotor 2 is disposed inside the stator 3. In other words, the stator 3 is configured to surround the rotor 2.

[0015] The rotor 2 rotates due to the magnetic force generated in the stator 3. Specifically, the rotor 2 has a rotating shaft 10, and rotates around an axis C of the rotating shaft 10 as the center of rotation.

[0016] The rotor 2 generates a magnetic force that acts on the stator 3. The rotor 2 is configured with a plurality of repeated north and south poles that form the main magnetic flux in the circumferential direction. The direction of the main magnetic flux generated by the rotor 2 is perpendicular to the direction of the axis C of the rotating shaft 10 (the direction of the rotating shaft).

[0017] The rotor 2 is disposed with an air gap between it and the stator 3. Specifically, a minute air gap exists between the surface of the rotor 2 and the surface of the stator 3. As will be described in detail later, the rotor 2 is an interior permanent magnet rotor (IPM rotor) in which permanent magnets are embedded in the iron core. Therefore, the electric motor 1 in this embodiment is an IPM motor.

[0018] The stator 3 is disposed opposite the rotor 2 via an air gap, and generates a magnetic force that acts on the rotor 2. Specifically, the stator 3 is disposed so as to surround the rotor core 20 of the rotor 2. The stator 3 and the rotor 2 form a magnetic circuit.

[0019] The stator 3 is configured so that N and S poles are generated alternately in the circumferential direction as main magnetic flux on the air gap surface. The stator 3 has a stator core 3a (stator core) and a winding coil 3b (stator coil).

[0020] The stator core 3a is provided with a plurality of teeth 3a1 that protrude toward the rotor core 20 of the rotor 2. Specifically, the plurality of teeth 3a1 are provided so as to protrude toward the axis C of the rotating shaft 10. The plurality of teeth 3a1 are also provided at equal intervals in the circumferential direction. Therefore, the plurality of teeth 3a1 extend radially in a direction perpendicular to the axis C of the rotating shaft 10 (radial direction).

[0021] The stator core 3a is made up of, for example, a plurality of steel plates stacked in the direction of the axis C of the rotating shaft 10. Each of the plurality of steel plates is, for example, an electromagnetic steel plate punched into a predetermined shape. Note that the stator core 3a is not limited to being a laminate of a plurality of steel plates, and may also be a bulk body made up of a magnetic material.

[0022] The winding coils 3b are wound around each of the multiple teeth 3a1 of the stator core 3a. Specifically, the winding coils 3b are wound around each tooth 3a1 via an insulator. Each winding coil 3b is composed of unit coils for three phases, U-phase, V-phase, and W-phase, which are electrically out of phase with each other by 120 degrees. In other words, the winding coils 3b wound around each tooth 3a1 are energized and driven by three-phase AC that is energized for each of the U-phase, V-phase, and W-phase. As a result, a main magnetic flux of the stator 3 is generated in each tooth 3a1.

[0023] In the electric motor 1 configured in this manner, when current is applied to the winding coil 3b of the stator 3, a field current flows through the winding coil 3b, generating a magnetic flux in the stator 3. The magnetic force generated by the interaction between the magnetic flux of the stator 3 and the magnetic flux of the rotor 2 becomes a torque that rotates the rotor 2, causing it to rotate.

[0024] Next, a detailed configuration of the rotor 2 according to this embodiment will be described using Figures 3 and 4, while also referring to Figures 1 and 2. Figure 3 is a cross-sectional view of the rotor 2 according to this embodiment. Figure 4 is an enlarged plan view showing an enlarged portion of the rotor 2, and a cross-sectional view taken along line AA of the enlarged plan view. Note that Figure 3 shows a cross-section taken along a plane perpendicular to the rotation axis 10.

[0025] As shown in FIGS. 1 to 3, the rotor 2 includes a rotating shaft 10, a rotor core 20, a plurality of first permanent magnets 30, and a plurality of second permanent magnets .

[0026] The rotating shaft 10 is a long shaft that serves as the center of rotation of the rotor 2. The rotating shaft 10 is, for example, a metal rod, and is fixed to the center of the rotor 2. Specifically, the rotating shaft 10 is fixed to the rotor core 20 in a state where it penetrates the center of the rotor core 20 of the rotor 2 so as to protrude on both sides of the rotor 2. The rotating shaft 10 is fixed to the rotor core 20 by press-fitting or shrink-fitting into a through-hole 20a formed in the center of the rotor core 20.

[0027] Although not shown, a first portion of the rotating shaft 10 protruding from one side of the rotor 2 is supported by a first bearing, and a second portion of the rotating shaft 10 protruding from the other side of the rotor 2 is supported by a second bearing. A load driven by the electric motor 1 is attached to the first or second portion of the rotating shaft 10.

[0028] The rotor core 20 (rotor core) is an iron core having a plurality of first holes 21 and a plurality of second holes 22. As shown in FIG. 4, the rotor core 20 is made up of a plurality of steel plates 20b stacked in the direction of the axis C of the rotating shaft 10. Specifically, the rotor core 20 is a substantially cylindrical laminate in which the plurality of steel plates 20b are stacked in the direction of the axis C of the rotating shaft 10. Each of the plurality of steel plates 20b is, for example, an electromagnetic steel plate punched into a predetermined shape, and is fixed to one another by caulking or the like.

[0029] As shown in FIG. 3, the plurality of first holes 21 and the plurality of second holes 22 are arranged radially around the rotating shaft 10. Here, the term "radial" is a concept that encompasses a substantially radial shape, and also includes shapes that are misaligned due to manufacturing errors, for example. The plurality of first holes 21 are arranged at equal intervals along the circumferential direction of the rotor core 20 (the direction of rotation of the rotating shaft 10). The plurality of second holes 22 are similarly arranged at equal intervals along the circumferential direction of the rotor core 20. The first holes 21 and the second holes 22 are arranged alternately along the circumferential direction. As shown in FIG. 4, each of the first holes 21 and the second holes 22 is a through-hole that penetrates the rotor core 20 along the direction of the axis C of the rotating shaft 10. Furthermore, in any cross section taken along a plane perpendicular to the rotating shaft 10, the cross-sectional shape of each of the first holes 21 is the same in the direction of the axis C of the rotating shaft 10, and the cross-sectional shape of each of the second holes 22 is the same in the direction of the axis C of the rotating shaft 10. Therefore, all of the steel plates 20b constituting the rotor core 20 have first holes 21 of the same shape and second holes 22 of the same shape formed therein.

[0030] As shown in Fig. 3, in a plan view, each of the multiple first holes 21 extends in the radial direction of the rotor core 20 (a direction perpendicular to the direction of the axis C of the rotating shaft 10). Therefore, the multiple long first holes 21 are formed in the shape of spokes centered on the rotating shaft 10. The plan view shape of each first hole 21 is a rectangle with the longitudinal direction aligned with the radial direction of the rotor core 20. The plan view shape of each of the multiple first holes 21 is the same as the others.

[0031] On the other hand, in plan view, the radial length of the rotor core 20 in each of the multiple second holes 22 is shorter than the length of the first holes 21. In other words, the radial length of the rotor core 20 in each of the multiple second holes 22 is shorter than the radial length of the rotor core 20 in each of the multiple first holes 21. In this embodiment, the radial length of the rotor core 20 in the second holes 22 is half or less of the radial length of the rotor core 20 in the first holes 21. The plan view shape of each of the multiple second holes 22 is the same as the others. The specific plan view shapes of the second holes 22 will be described later.

[0032] A plurality of first permanent magnets 30 are respectively arranged in the plurality of first holes 21. In other words, the first holes 21 are first magnet arrangement holes in which the first permanent magnets 30 are arranged. The first permanent magnets 30 are sintered magnets. Therefore, the first holes 21 are magnet insertion holes, and the first permanent magnets 30, which are sintered magnets, are inserted into the first holes 21. One first permanent magnet 30 is inserted into one first hole 21.

[0033] The first permanent magnet 30 is a main magnet in the rotor 2. Specifically, the first permanent magnet 30 is arranged so that the direction of its magnetic poles is the circumferential direction of the rotor core 20 (the direction of rotation of the rotating shaft 10). In other words, the first permanent magnet 30 is magnetized so that the direction of its magnetic poles is the circumferential direction of the rotor core 20. Note that the S and N poles of two adjacent first permanent magnets 30 are oriented in opposite directions.

[0034] The shape and size of the first permanent magnet 30 in a plan view are substantially the same as the shape and size of the first hole 21 in a plan view. The first permanent magnet 30 is fitted into the first hole 21. Therefore, the shape of the first permanent magnet 30 in a plan view is an elongated rectangle. As an example, the first permanent magnet 30 is a plate-like rectangular parallelepiped.

[0035] In each first hole 21, a small gap (clearance) may exist between the first permanent magnet 30 and the inner surface of the first hole 21. An adhesive may be provided in this gap to adhesively fix the first permanent magnet 30 to the first hole 21. On the other hand, no adhesive may be provided in this gap. The gap between the first permanent magnet 30 and the inner surface of the first hole 21 only needs to ensure the minimum dimensional tolerance required for manufacturing.

[0036] Furthermore, a plurality of second permanent magnets 40 are respectively arranged in the plurality of second holes 22. In other words, the second holes 22 are second magnet arrangement holes in which the second permanent magnets 40 are arranged. The second permanent magnets 40 are sintered magnets. Therefore, the second holes 22 are magnet insertion holes, and the second permanent magnets 40, which are sintered magnets, are inserted into the second holes 22. One second permanent magnet 40 is inserted into one second hole 22.

[0037] The second permanent magnets 40 are auxiliary magnets in the rotor 2. Specifically, the second permanent magnets 40 are arranged so that the direction of their magnetic poles is the radial direction of the rotor core 20 (the direction perpendicular to the rotation axis 10). In other words, the second permanent magnets 40 are magnetized so that the direction of their magnetic poles is the radial direction of the rotor core 20. Note that the S and N poles of two adjacent second permanent magnets 40 are oriented in opposite directions.

[0038] The shape of the second permanent magnet 40 in a plan view is different from the shape of the second hole 22. The shape of the second permanent magnet 40 in a plan view is a rectangle with a small aspect ratio. As an example, the second permanent magnet 40 is a rod-shaped rectangular parallelepiped.

[0039] Each of the plurality of second holes 22 has a protrusion 22a. In each second hole 22, the protrusion 22a is located radially inward of the rotor core 20 with respect to a first hole 21 that is adjacent to the second hole 22 in the circumferential direction of the rotor core 20 among the plurality of first holes 21, and protrudes toward the first hole 21 that is adjacent to the second hole 22 in the circumferential direction of the rotor core 20.

[0040] The planar shape of each second hole 22 is a shape obtained by adding a protrusion 22a to a shape equivalent to the planar shape of the second permanent magnet 40. In other words, the planar shape of each second hole 22 is a shape obtained by adding a protrusion 22a to a side of a rectangle with a small aspect ratio.

[0041] In each of the multiple second holes 22, the protrusion 22a is located radially inward of the rotor core 20. In other words, the protrusion 22a does not protrude from the entirety of one side of the rectangular portion of the second hole 22, but rather protrudes from a portion of one side of the rectangular portion of the second hole 22 that is closer to the inside.

[0042] In each second hole 22, the shape of the protrusion 22a in a plan view has a vertex and its width narrows toward the vertex. Furthermore, in each second hole 22, the protrusion 22a has an opposing side that faces one side of the first hole 21 adjacent to the second hole 22. The angle between the opposing side and one side of the adjacent first hole 21 is preferably between -5° and 5°. In this embodiment, the opposing side of the protrusion 22a is parallel to one side of the first hole 21 adjacent to the protrusion 22a. Specifically, the shape of the protrusion 22a in a plan view is triangular, and one side of the triangle is parallel to one side of the first hole 21. As a result, as shown in FIG. 4, the width of the bridge portion 20br, which is the portion between the protrusion 22a and the first hole 21, is constant.

[0043] In each of the multiple second holes 22, protrusions 22a are provided on both sides of a center line of the second hole 22 that extends in the radial direction of the rotor core 20. In other words, protrusions 22a protrude from each of two opposing sides of the rectangular portion of the second hole 22. Therefore, the shape of the second hole 22 in plan view is a combination of a rectangle with a small aspect ratio, which is the shape of the second permanent magnet 40 in plan view, and a triangle protruding from a portion of each of the two opposing sides of the rectangle near the inside.

[0044] In each of the plurality of second holes 22, the two protrusions 22a are provided symmetrically with respect to the center line of the second hole 22 extending in the radial direction of the rotor core 20.

[0045] The second permanent magnets 40 disposed in the second holes 22 are located in the rectangular portions of the second holes 22. Therefore, in each second hole 22, the protruding portions 22a are not occupied by the second permanent magnets 40 and remain as voids. In other words, the second permanent magnets 40 are not present in the protruding portions 22a, and the protruding portions 22a become voids (spatial regions).

[0046] In addition, in the rectangular portion of each second hole 22, a small gap (clearance) may exist between the second permanent magnet 40 and the inner surface of the second hole 22. An adhesive may be provided in this gap to adhesively fix the second permanent magnet 40 to the second hole 22. In this case, an adhesive may be provided in at least a portion of the protrusion 22a to fix the second permanent magnet 40 to the second hole 22. In the rectangular portion of each second hole 22, no adhesive may be provided in the gap between the second permanent magnet 40 and the inner surface of the second hole 22. In other words, in the rectangular portion of each second hole 22, the gap between the second permanent magnet 40 and the inner surface of the second hole 22 only needs to ensure the minimum dimensional tolerance required for manufacturing.

[0047] The rotor 2 configured in this manner is an eight-pole rotor with eight magnetic poles, and eight first permanent magnets 30 and eight second permanent magnets 40 are arranged circumferentially so that the south and north poles are alternately positioned in the circumferential direction as the main magnetic flux. In other words, eight first holes 21 and eight second holes 22 are alternately provided in the rotor core 20.

[0048] Next, the effects of the rotor 2 and the electric motor 1 according to this embodiment will be described with reference to Figs. 5 to 7, including the background to the development of this disclosure. Fig. 5 is an enlarged plan view showing a portion of the rotor 2X of Comparative Example 1. Fig. 6 is an enlarged plan view showing a portion of the rotor 2Y of Comparative Example 2. Fig. 7 is an enlarged plan view showing a portion of the rotor 2 according to this embodiment. In Figs. 5 to 7, arrows indicate the flow of magnetic flux.

[0049] 5, in the rotor 2X of Comparative Example 1, a rotor core 20X is provided with a first hole 21 and a second hole 22X, similar to the rotor 2 in the above embodiment. In the rotor 2X, a first permanent magnet 30 is arranged in the first hole 21, and a second permanent magnet 40X is arranged in the second hole 22X.

[0050] However, in the rotor 2X of Comparative Example 1, unlike the rotor 2 in the above embodiment, the second holes 22X and second permanent magnets 40X have trapezoidal shapes in plan view, and the entire side surface of the second holes 22X (the opposing sides facing the first holes 21) is parallel to the side surface of the first holes 21. For this reason, in the structure of the rotor 2X of Comparative Example 1 shown in Fig. 5, the flow of magnetic flux is obstructed at the corners of the base of the trapezoid of the second holes 22X (the portions indicated by the dashed circle in Fig. 5).

[0051] 6, in the rotor 2Y of Comparative Example 2, a rotor core 20Y is provided with a first hole 21 and a second hole 22Y, similar to the rotor 2 in the above embodiment. A first permanent magnet 30 is disposed in the first hole 21, and a second permanent magnet 40Y is disposed in the second hole 22Y.

[0052] However, unlike the rotor 2 in the above embodiment, the rotor 2Y in Comparative Example 2 has a rectangular second hole 22Y and a rectangular second permanent magnet 40Y in plan view. Therefore, in the rotor 2Y in Comparative Example 2 shown in FIG. 6 , the radially outer portion of the side surface of the second hole 22Y (the side facing the first hole 21) is significantly separated from the side surface of the first hole 22. As a result, the structure of the rotor 2Y in Comparative Example 2 increases leakage magnetic flux (indicated by the dashed arrow in FIG. 6 ). Therefore, in the adjacent first permanent magnet 30 and second permanent magnet 40Y, the magnetic flux of the first permanent magnet 30 and the magnetic flux of the second permanent magnet 40Y interfere with each other. Specifically, the magnetic flux of the second permanent magnet 40Y interferes with the magnetic flux of the first permanent magnet 30 adjacent to the second permanent magnet 40Y. This reduces the flux linkage that interlinks with the stator.

[0053] In contrast, in the rotor 2 of this embodiment, as shown in Figure 7, each of the multiple second holes 22 is located radially inward of the rotor core 20 relative to the first hole 21 among the multiple first holes 21 that is adjacent to the second hole 22 in the circumferential direction of the rotor core 20, and has a protrusion 22a that protrudes toward the first hole 21 that is adjacent to the second hole 22 in the circumferential direction of the rotor core 20.

[0054] With this configuration, the width between the second holes 22 and the first holes 21 can be increased at the radially outer side of the rotor core 20 in the second holes 22, while the width between the second holes 22 and the first holes 21 can be narrowed at the radially inner side of the rotor core 20 in the second holes 22. In other words, the width of the bridge portions 20br between the second holes 22 (protrusions 22a) and the first holes 21 can be narrowed only at the radially inner side of the rotor core 20 in the second holes 22. This makes it possible to prevent the shape of the second holes 22X from obstructing the flow of magnetic flux, as in the rotor 2X of Comparative Example 1 shown in FIG. 5, and also to prevent a reduction in the magnetic flux linking the stator due to interference between the magnetic flux of the first permanent magnet 30 and the magnetic flux of the second permanent magnet 40Y, as in the rotor 2Y of Comparative Example 2 shown in FIG. 6.

[0055] As described above, according to rotor 2 of this embodiment, it is possible to reduce leakage magnetic flux and increase the interlinkage magnetic flux that interlinks with stator 3.

[0056] Furthermore, in the rotor 2 according to the present embodiment, the opposing side of the protruding portion 22a of the second hole 22 that faces the first hole 21 is preferably parallel to the side surfaces of the first permanent magnet 30 and the first hole 21. In other words, the width of the bridge portion 20br is preferably constant.

[0057] This configuration can further reduce leakage flux, thereby further increasing the magnetic flux linking the stator 3.

[0058] In this case, the shape of the protrusion 22a in plan view may have a vertex and the width may narrow towards the vertex.

[0059] With this configuration, the side of the protruding portion 22a of the second hole 22 facing the first hole 21 can be easily made parallel to the side surfaces of the first permanent magnet 30 and the first hole 21. In other words, the width of the bridge portion 20br can be easily made constant.

[0060] Here, we have examined the length 1 of the portion of the bridge portion 20br between the second hole 22 (protrusion 22a) and the first hole 21, where the protrusion 22a faces the first permanent magnet 30. The results of this examination will be explained with reference to FIG. 7.

[0061] 7, if the length of the portion of the bridge portion 20br where the protrusion 22a faces the first permanent magnet 30 is l, then l is the distance between the inner peripheral end face of the first permanent magnet 30 and point P. Here, point P is the outer end of the projected image when the protrusion 22a is projected onto the facing side of the first hole 21 facing the second hole 22 from a direction perpendicular to the facing side.

[0062] The region of the first permanent magnet 30 where the short-circuit magnetic flux is generated (the region indicated by dotted hatching in FIG. 7) is referred to as region S. The length of the rotor core 20 in the radial direction in region S is l mgThe surface magnetic flux density of the first permanent magnet 30 is B' r Then, the amount of magnetic flux φ1 generated in area S is φ1=B' r ×l mg It is expressed as:

[0063] Also, the magnetic flux density of the magnetic saturation region MS of the bridge portion 20br is expressed as B' s and the width of the bridge portion 20br on the inner peripheral end face of the first permanent magnet 30 is w, the amount of magnetic flux φ2 passing through the magnetic saturation region MS is given by φ2=B' s It is expressed as ×w.

[0064] At this time, if the amount of magnetic flux that short-circuits through areas other than the magnetic saturation region MS is A (A>0), it can be expressed as φ1=φ2+A, resulting in the following (Equation 1).

[0065]

number

[0066] Here, the length l of the portion where the protrusion 22a of the bridge portion 20br faces the first permanent magnet 30 is the radial length l of the rotor core 20 in the region S where the short-circuit magnetic flux is generated in the first permanent magnet 30. mg Therefore, in the above (Equation 1), l = l mg By substituting the above, the length l of the portion where the protrusion 22a of the bridge portion 20br faces the first permanent magnet 30 can be expressed by the following (Equation 2).

[0067]

number

[0068] Furthermore, the residual magnetic flux density of the first permanent magnet 30 is B r and the saturation magnetization of the rotor core 20 is J s Then, B' r r , B' s >J s ​Therefore, since A>0, the above (Equation 2) can be expressed as the following (Equation 3).

[0069]

number

[0070] From the above, it is preferable that the length l of the portion where the protrusion of the bridge portion 20br faces the first permanent magnet satisfies the above-mentioned relational expression (Equation 3). By satisfying this relational expression (Equation 3), it is possible to reduce leakage flux and effectively increase the flux linkage that links with the stator.

[0071] As described above, the rotor 2 of this embodiment includes the rotor core 20 having a plurality of first holes 21 and a plurality of second holes 22, a plurality of first permanent magnets 30 respectively arranged in the plurality of first holes 21, and the rotating shaft 10 fixed to the rotor core 20, and the plurality of first holes 21 and the plurality of second holes 22 are provided radially around the rotating shaft 10, and each of the plurality of first holes 21 extends in the radial direction of the rotor core 20, and the plurality of second holes 22 are provided radially around the rotating shaft 10. The radial length of the rotor core 20 in each of the plurality of first holes 21 is smaller than the radial length of the rotor core 20 in each of the plurality of first holes 21, and each of the plurality of second holes 22 is located radially inward of the rotor core 20 relative to the first hole 21 that is circumferentially adjacent to the second hole 22 on the rotor core 20, and has a protrusion 22a that protrudes toward the first hole 21 that is circumferentially adjacent to the second hole 22 on the rotor core 20.

[0072] This makes it possible to increase the flux linkage.

[0073] In the rotor 2, in each of the plurality of second holes 22, the protrusion 22a is located closer to the inner side in the radial direction of the rotor core 20.

[0074] This configuration makes it possible to increase the interlinkage magnetic flux formed by the magnetic flux of the first permanent magnet 30 and the magnetic flux of the second permanent magnet 40.

[0075] In the rotor 2, in each of the plurality of second holes 22, the protrusions 22a include two protrusions 22a provided on both sides of a center line extending radially of the rotor core 20 in the second hole 22. In this case, the protrusions 22a may be provided symmetrically with respect to the center line extending radially of the rotor core 20 in the second hole 22.

[0076] With this configuration, leakage flux can be reduced and interlinkage flux can be increased even when the rotor 2 rotates both counterclockwise and clockwise. Note that the protrusions 22a may be provided on only one side, rather than on both sides. Also, second holes 22 having protrusions 22a only on one end and second holes 22 having protrusions 22a only on the other end may be provided alternately in the circumferential direction.

[0077] (Variation) The rotor 2 and the electric motor 1 according to the present disclosure have been described above based on the embodiments, but the present disclosure is not limited to the above-described embodiments.

[0078] For example, in the above embodiment, the second permanent magnets 40 are arranged in the second holes 22, but this is not limited to this. FIG. 8 is an enlarged plan view showing a portion of a rotor according to Modification 1. Specifically, as in the rotor 2A shown in FIG. 8, the second permanent magnets 40 may not be arranged in the second holes 22, and the first permanent magnets 30 may be arranged only in the first holes 21 of the first and second holes 22. That is, in FIG. 8, each of the multiple second holes 22 does not have a second permanent magnet 40, and the entire second hole 22 is an air gap (spatial region). In this case, although the main magnetic flux of the rotor 2A is reduced by the absence of the second permanent magnets 40, leakage magnetic flux can be reduced and interlinkage magnetic flux can be increased compared to the case in FIG. 8 where the second holes 22 are not provided with the protrusions 22a.

[0079] In the above embodiment, the bridge portions 20br are flush with other portions of the rotor core 20, but this is not limited to this. Fig. 9 is an enlarged plan view showing a portion of a rotor according to Modification 2. Specifically, as in the rotor 2B shown in Fig. 9, the surfaces of the bridge portions 20br in the rotor core 20B may be recessed in the direction of the axis C of the rotating shaft 10. For example, by applying press working to the rotor core 20B to form recesses 23 in the bridge portions 20br (areas indicated by dotted hatching in the plan view of Fig. 9), the surfaces of the bridge portions 20br can be recessed relative to other surfaces. As a result, the thickness t of the bridge portions 20br can be reduced. press The thickness t of the bridge portion 20br can be made thinner than the thickness t of the portion other than the bridge portion 20br. By recessing the bridge portion 20br to reduce its thickness in this way, it is possible to further reduce leakage magnetic flux and further increase interlinkage magnetic flux. Note that the entire surface of the bridge portion 20br need not be recessed, and at least a portion of the bridge portion 20br may be recessed.

[0080] In the above embodiment, as shown in Fig. 7, the portion of the protruding portion 22a located most radially inward of the rotor core 20 is near the surface on the inner circumferential side surface of the first permanent magnet 30, but this is not limited to this. Fig. 10 is an enlarged plan view showing a portion of a rotor according to Modification 3. Specifically, as in the rotor core 20C of the rotor 2C shown in Fig. 10, a portion of the protruding portion 22a may be located radially inward of the inner circumferential side surface of the first permanent magnet 30.

[0081] In the above embodiment, the planar shape of the protrusion 22a of the second hole 22 is a polygon consisting of only straight sides, and the side surface of the protrusion 22a is composed of only flat surfaces. However, this is not limited to this. FIG. 11 is an enlarged plan view showing a portion of a rotor according to Modification 4. For example, as in rotor core 20D of rotor 2D shown in FIG. 11, one of the side surfaces of the protrusion 22a may include a curved surface. In this case, as in the above embodiment, the side surface of the protrusion 22a facing the first hole 21 may be flat, and the side surface of the protrusion 22a facing the first hole 21 and the side surface of the first hole 21 may be parallel. In other words, in a planar view, the side of the protrusion 22a facing the first hole 21 and one side of the first hole 21 may be parallel.

[0082] In the above embodiment, the opposing side of protrusion 22a facing first hole 21 and one side of first hole 21 are parallel to each other. However, this is not limited to this. FIG. 12 is an enlarged plan view showing a part of a rotor according to Modification 5. For example, as in rotor core 20E of rotor 2E shown in FIG. 12, the opposing side of protrusion 22a facing first hole 21 and one side of first hole 21 do not have to be parallel to each other. FIG. 13 is an enlarged plan view showing a part of a rotor according to Modification 6. Similarly, as in rotor core 20F of rotor 2F shown in FIG. 13, the opposing side of protrusion 22a facing first hole 21 and one side of first hole 21 of rotor core 20F do not have to be parallel to each other. For example, as shown in Fig. 12, protrusion 22a may be provided so that the opposing side of protrusion 22a moves away from one side of first hole 21, or as shown in Fig. 13, protrusion 22a may be provided so that the opposing side of protrusion 22a moves closer to one side of first hole 21. Furthermore, although not shown, the opposing side of protrusion 22a may be formed by a plurality of straight lines. Furthermore, although not shown, the opposing side of protrusion 22a may be formed by a plurality of curved lines, or may be formed by a combination of one or more straight lines and one or more curved lines.

[0083] Furthermore, in the above embodiment, the cross-sectional shape of each of the second holes 22 was the same in the direction of the axis C of the rotating shaft 10 in any cross section when cut by a plane perpendicular to the rotating shaft 10, but this is not limited to this.

[0084] FIG. 14 is a partial cross-sectional view of a rotor according to Modification 7. For example, as in a rotor core 20H of a rotor 2H shown in FIG. 14, at least two of the plurality of steel plates 20b may not have second holes 22, and the steel plate 20b located between the two of the plurality of steel plates 20b without the second holes 22 may have the second holes 22, and the second permanent magnet 40 may be sandwiched between the two steel plates 20b without the second holes 22. Specifically, in the rotor core 20H in FIG. 14, the steel plates 20b at both ends of the plurality of steel plates 20b do not have second holes 22, and the second permanent magnet 40 is sandwiched between the steel plates 20b at one end and the steel plates 20b at the other end. This allows the second permanent magnet 40 to be held in the second holes 22 without using an adhesive.

[0085] FIG. 15 is a partial cross-sectional view of a rotor according to Modification 8. As in a rotor core 20I of a rotor 2I shown in FIG. 15, at least one of the multiple steel plates 20b may not have a second hole 22, and two second permanent magnets 40 may be arranged via the steel plate 20b that does not have a second hole 22. Specifically, in the rotor core 20I in FIG. 15, two second permanent magnets 40 are arranged in one second hole 22. This configuration makes it possible to easily insert multiple second permanent magnets 40 into one second hole 22. Note that three or more second permanent magnets 40 may be arranged in one second hole 22.

[0086] FIG. 16 is a partial cross-sectional view of a rotor according to Variation 9. As in a rotor core 20J of a rotor 2J shown in FIG. 16, at least one of the plurality of steel plates 20b may have a protrusion 24 that protrudes inward from a portion of the side of the second hole 22. Specifically, in the rotor core 20J shown in FIG. 16, the protrusion 24 is provided in the second hole 22 of one of the steel plates 20b located at both ends of the plurality of steel plates 20b. With this configuration, the protrusion 24 functions as a stopper when the second permanent magnet 40 is inserted into the second hole 22, making it easy to hold the second permanent magnet 40 in the second hole 22. The protrusions 24 do not necessarily have to be formed in all of the second holes 22 formed in one rotor core 20J, and may be formed in only some of the second holes 22.

[0087] In the above embodiment, the inner peripheral sides (rotation shaft 10 side) of the second holes 22 and the second permanent magnets 40 are positioned at the same positions as the inner peripheral sides of the first holes 21 and the first permanent magnets 30. However, this is not limited to this. FIG. 17 is an enlarged plan view showing a portion of a rotor according to Modification 10. For example, as in the rotor core 20K of the rotor 2K shown in FIG. 17, the inner peripheral sides of the second holes 22 and the second permanent magnets 40 may be positioned more inward (closer to the rotation shaft 10) than the inner peripheral sides of the first holes 21 and the first permanent magnets 30. In other words, the second holes 22 and the second permanent magnets 40 may be positioned more inward than the first holes 21 and the first permanent magnets 30. Alternatively, although not shown, the inner peripheral sides of the second holes 22 and the second permanent magnets 40 may be positioned more outward than the inner peripheral sides of the first holes 21 and the first permanent magnets 30.

[0088] In the above embodiment, no gap is formed in the first hole 21 into which the first permanent magnet 30 is inserted, but this is not limited to this. FIG. 18 is an enlarged plan view showing a portion of a rotor according to Modification 11. For example, as in the rotor core 20L of the rotor 2L shown in FIG. 18, gaps 21a may be formed as flux barriers at both ends of the outer peripheral edge of the first hole 21. With this configuration, even if torque ripple increases as a result of using the first permanent magnet 30 and the second permanent magnet 40 and providing the protrusion 22a in the second hole 22 to reduce leakage flux, the formation of gaps 21a in the first hole 21 can reduce torque ripple.

[0089] While the rotor 2 in the above embodiment uses a rotor core 20 whose outer circumferential shape in plan view is circular, this is not limiting. FIG. 19 is an enlarged plan view showing a portion of a rotor according to Modification 12. Specifically, as in rotor 2M shown in FIG. 19, a rotor core 20M may be used in which a flat surface 25 is formed on the outer circumferential portion so that a portion of the outer circumferential shape in plan view has a straight line. For example, in rotor core 20M shown in FIG. 19, flat surface 25 is formed on the portion facing first hole 21. With this configuration, even if torque ripple increases as a result of using first permanent magnet 30 and second permanent magnet 40 and providing protrusion 22a in second hole 22 to reduce leakage flux, forming flat surface 25 on the outer circumferential portion of rotor core 20M can reduce torque ripple.

[0090] Fig. 20 is an enlarged plan view showing a portion of a rotor according to Modification 13. As in rotor core 20N of rotor 2N shown in Fig. 20, torque ripple can be further reduced by forming bulging surfaces 26 on the outer periphery in addition to flat surfaces 25. Bulging surfaces 26 are curved surfaces that bulge outward, and in Fig. 20, they are formed in the portions facing second holes 22.

[0091] Although the stator 3 in the above-described embodiment is an open-slot stator in which an opening is provided between the tips of two adjacent teeth 3a1 in the stator core 3a, this is not limiting. FIG. 21 is a partial cross-sectional view of a stator in an electric motor according to Modification 14. For example, as in the stator 3O shown in FIG. 21, the stator may be a closed-slot stator in which the tips of two adjacent teeth 3a1 in the stator core 3a are connected. With this configuration, even if torque ripple increases as a result of using the first permanent magnet 30 and the second permanent magnet 40 and providing the protrusion 22a in the second hole 22 to reduce leakage magnetic flux, using a closed-slot stator as the stator 3O makes it possible to reduce torque ripple.

[0092] Although the rotor 2 in the above embodiment has eight magnetic poles, this is not limiting. FIG. 22 is a cross-sectional view of a rotor according to Modification 15. For example, the number of magnetic poles may be ten, as in the rotor 2P shown in FIG. 22. In this case, ten first permanent magnets 30 and ten second permanent magnets 40 are arranged circumferentially so that south and north poles are alternately positioned in the circumferential direction as the main magnetic flux. In other words, ten first holes 21 and ten second holes 22 are alternately provided in the rotor core 20P of the rotor 2P shown in FIG. 22. The number of magnetic poles of the rotor may be other than eight or ten, and any number may be used as long as the number is 2n (n is a natural number).

[0093] In the above embodiment, all of the second holes 22 provided in the rotor core 20 have the protrusions 22a, but this is not limited to this. For example, the plurality of second holes 22 may include a second hole 22 that does not have a protrusion 22a.

[0094] In the above embodiment, the protruding portions 22a of the second holes 22 are voids, but this is not limited thereto. For example, the second permanent magnets 40 may be embedded in the entirety of each second hole 22, including the protruding portions 22a. That is, the planar shape and size of the second permanent magnets 40 may be substantially the same as the planar shape and size of the second holes 22. In this case, the second permanent magnets 40 may be sintered magnets, but sintered magnets with shapes other than rectangular parallelepipeds are difficult to process and expensive. Therefore, when the second permanent magnets 40 are embedded in the entirety of each second hole 22, including the protruding portions 22a, it is preferable that the second permanent magnets 40 be bonded magnets. Note that the first permanent magnets 30 are not limited to sintered magnets, and may also be bonded magnets.

[0095] In addition, in the above embodiment, the first permanent magnet 30 is the main magnet and the second permanent magnet 40 is the auxiliary magnet, but this is not limiting. For example, the second permanent magnet 40 may be the main magnet and the first permanent magnet 30 may be the auxiliary magnet.

[0096] Furthermore, the electric motors including the rotors according to the above-described embodiments can be used in a variety of electrical appliances, such as household electrical appliances such as vacuum cleaners, air conditioners, and refrigerators, or industrial electrical appliances such as automotive equipment and robots. [Industrial Applicability]

[0097] The technology of the present disclosure can be used in rotors such as IPM rotors, etc. The technology of the present disclosure can be widely used not only in rotors but also in various products such as electric motors including rotors and electrical equipment including electric motors. [Explanation of symbols]

[0098] 1 electric motor 2, 2A, 2B, 2C, 2D, 2E, 2F, 2H, 2I, 2J, 2K, 2L, 2M, 2N, 2P rotor 3, 3O stator 3a stator core 3a1 Teeth 3b Wound coil 10 Rotation axis 20, 20B, 20C, 20D, 20E, 20F, 20H, 20I, 20J, 20K, 20L, 20M, 20N, 20P rotor core 20a through hole 20b steel plate 20br Bridge 21 Hole 1 21a Cavity 22 2nd hole 22a Protrusion 23 Recess 24 protrusions 25 flat surface 26 Bulging surface 30 First permanent magnet 40 Second permanent magnet

Claims

1. The present invention relates to an iron core having a plurality of first holes and a plurality of second holes, a plurality of first permanent magnets respectively arranged in the plurality of first holes, and a rotating shaft fixed to the iron core, wherein the plurality of first holes and the plurality of second holes are provided radially around the rotating shaft, each of the plurality of first holes extends in a radial direction of the iron core, the radial length of the iron core at each of the plurality of second holes is smaller than the radial length of the iron core at each of the plurality of first holes, and each of the plurality of second holes is located in front of a first hole among the plurality of first holes that is adjacent to the second hole in the circumferential direction of the iron core. a rotor having a protrusion located radially inward of the core and protruding toward the second hole and the first hole adjacent to the core in the circumferential direction, the protrusion having an opposing side opposing one side of the first hole, the protrusion being located radially inward of the core in each of the plurality of second holes and protruding from a part of the opposing side of the second hole located radially inward, the protrusion having a vertex on the radially inner side and narrowing toward the vertex, the angle formed by the opposing side and the one side being greater than or equal to -5° and less than 5°, and comprising a plurality of second permanent magnets respectively arranged in the plurality of second holes.

2. 2. The rotor according to claim 1, wherein in each of the plurality of second holes, the protrusion includes two protrusions provided on both sides of a center line of the second hole extending radially of the iron core.

3. The rotor according to claim 2 , wherein the two protrusions are provided symmetrically with respect to the center line.

4. The iron core has a bridge portion that is a portion between the protrusion and the first hole, and the following relational expression is satisfied when the radial length of the bridge portion where the adjacent first magnet and the protrusion face each other is defined as l, the width of the bridge portion at the portion where the adjacent first magnet and the protrusion face each other is defined as w, the residual magnetic flux density of the first permanent magnet is defined as Br, and the saturation magnetization of the iron core is defined as Js: [Equation 1] The rotor according to any one of claims 1 to 3.

5. The rotor according to claim 1 , wherein the opposing side and the one side are parallel to each other.

6. The rotor according to claim 1 , wherein the second permanent magnet is not present in the protruding portion.

7. The rotor according to claim 1 , wherein an adhesive for fixing the second hole and the second permanent magnet is present in at least a portion of the protrusion.

8. The rotor according to claim 1 , wherein the second hole is a through hole that penetrates the iron core.

9. 2. The rotor of claim 1, wherein the iron core is composed of a plurality of steel plates stacked in the axial direction of the rotating shaft, at least two of the plurality of steel plates do not have the second hole, and the steel plate located between two of the plurality of steel plates that do not have the second hole has the second hole, and the second permanent magnet is sandwiched between the two steel plates that do not have the second hole.

10. 2. The rotor of claim 1, wherein the iron core is composed of a plurality of steel plates stacked in the axial direction of the rotating shaft, at least one of the plurality of steel plates does not have the second hole, and two of the second permanent magnets are arranged via the steel plate that does not have the second hole.

11. 2. The rotor of claim 1, wherein the iron core is composed of a plurality of steel plates stacked in the axial direction of the rotating shaft, and at least one of the plurality of steel plates has a protrusion that protrudes from a portion of a side of the second hole toward the inside of the second hole.

12. A rotor as described in any one of claims 1 to 11, wherein the iron core has a bridge portion which is the portion between the protrusion and the first hole, and at least a portion of the surface of the bridge portion is recessed in the axial direction of the rotating shaft.

13. An electric motor comprising: a rotor according to any one of claims 1 to 12; and a stator disposed opposite the rotor via an air gap and generating a magnetic force acting on the rotor.

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