WO2025204819A1 - Rotor and motor - Google Patents

Abstract

A rotor according to the present invention comprises: a rotary shaft extending in the axial direction; a rotor core including a plurality of core blocks and into which the rotary shaft is inserted; and a plurality of magnets annularly arrayed about the rotary shaft inside the rotor core. A plurality of holes are provided in each of the plurality of core blocks located between two adjacent magnets among the plurality of magnets in the rotor core. Taking 0% as the position of a straight line connecting end portions on the inner circumferential side of two adjacent magnets and 100% as the position of a straight line connecting end portions on the outer circumferential side of the two adjacent magnets, the plurality of holes are provided at positions from 55-95% in a radial direction crossing the axial direction.

Description

Rotor and Motor

The present disclosure relates to a rotor and a motor including the rotor.

Motors are used in a variety of electrical devices, including household and industrial equipment. One type of motor is the IPM (Interior Permanent Magnet) motor, which is a motor with embedded permanent magnets. IPM motors are equipped with an IPM-type rotor in which magnets are arranged in multiple magnet arrangement holes provided in the rotor core. Conventionally, a spoke-type rotor in which multiple magnets are arranged radially has been known as an IPM-type rotor.

As an IPM rotor of this type, a spoke-type rotor with holes between adjacent magnets in the rotor core has been proposed (see Patent Document 1).

In an IPM type rotor, by providing holes or through-holes between adjacent magnets in the rotor core, torque ripple can be reduced, although the average torque decreases due to the magnetic resistance of the holes or through-holes.

The inventors have discovered that, depending on the position of the holes or through-holes provided between adjacent magnets in the rotor core, it is possible to reduce torque ripple while maintaining a predetermined average torque without reducing the average torque.

JP 2014-230348 A

The objective of this disclosure is to provide a rotor and motor that can reduce torque ripple without reducing average torque.

In order to achieve the above object, one aspect of a rotor according to the present disclosure comprises a rotating shaft extending in an axial direction, a rotor core including multiple core blocks through which the rotating shaft is inserted, and multiple magnets arranged in a ring shape around the rotating shaft inside the rotor core, wherein each of the multiple core blocks located between two adjacent magnets among the multiple magnets in the rotor core has multiple holes, and when the position of a line connecting the inner ends of the two adjacent magnets is defined as 0% and the position of a line connecting the outer ends of the two adjacent magnets is defined as 100%, the multiple holes are located at positions between 55% and 95% in a radial direction intersecting the axial direction.

It is preferable that the multiple holes are located at positions that are 55% to 90% of the radial distance.

The plurality of holes may be arranged symmetrically between the two adjacent magnets with respect to the magnetic pole center lines generated by each of the two adjacent magnets.

The plurality of holes may extend through the rotor core along the axial direction.

It is preferable that the multiple holes are positioned so that the magnetic flux density between the multiple holes when no load is less than ±40% of the magnetic flux density when no load is present between one of the two adjacent magnets and the hole closest to that magnet.

Furthermore, a through hole penetrating in the axial direction may be provided between two adjacent magnets among the plurality of magnets in the rotor core, and the through hole may be located radially inward of the plurality of holes. When the position of a line connecting the inner circumferential ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer circumferential ends of the two adjacent magnets is set to 100%, the through hole may be located at a position that is 60% or less in the radial direction.

It is preferable that the through holes are located at a position no greater than 50% in the radial direction.

The rotor core may be molded with resin, and the through-holes may be filled with the resin, but the holes may not be filled with the resin.

Another aspect of the rotor according to the present disclosure comprises a rotating shaft extending in the axial direction, a rotor core through which the rotating shaft is inserted, and a plurality of magnets arranged inside the rotor core in a ring shape centered on the rotating shaft, wherein the rotor core has a through-hole penetrating in the axial direction between two adjacent magnets among the plurality of magnets, and when the position of a line connecting the inner circumferential ends of the two adjacent magnets is taken as 0% and the position of a line connecting the outer circumferential ends of the two adjacent magnets is taken as 100%, the through-hole is located at a position no greater than 60% in the radial direction intersecting the axial direction.

It is preferable that the through holes are located at a position no greater than 50% in the radial direction.

The rotor core may be molded with resin, and the through holes may be filled with the resin.

The rotor core may have a plurality of core blocks divided along the circumferential direction surrounding the axial direction, and the area between two adjacent core blocks among the plurality of core blocks may be a magnet placement hole in which the magnet is placed.

Furthermore, one aspect of the motor disclosed herein includes the above rotor and a stator that generates a magnetic force acting on the rotor.

The stator comprises a stator core having a plurality of teeth extending toward the rotating shaft, each of the plurality of teeth having an extension portion extending from its inner circumferential tip to both sides in the circumferential direction, and when the center between the extension portions of each of two adjacent teeth of the plurality of teeth coincides with the magnetic pole centerline between the two adjacent magnets of the rotor core, it is preferable that the tip of the extension portion be located between two tangent lines drawn from the axis of the rotating shaft to one of the plurality of holes.

According to this disclosure, torque ripple can be reduced without reducing average torque.

FIG. 1 is a cross-sectional view of a motor according to an embodiment. FIG. 2 is a perspective view of a core block used in a rotor core in a rotor according to an embodiment. FIG. 3 is a diagram schematically showing the magnetic flux distribution of the motor according to the embodiment. FIG. 4 is a diagram showing the relationship between the position of the holes in the rotor core and the average torque and torque ripple in the rotor according to the embodiment. FIG. 5 is a diagram showing the relationship between the position of the through-hole in the rotor core and the average torque and torque ripple in the rotor according to the embodiment. FIG. 6 is a diagram for explaining the positional relationship between the positions of the holes in the rotor core and the extensions and tips of the teeth in the stator in the rotor according to the embodiment. FIG. 7 is a diagram showing the relationship between the width of the openings in the teeth of the stator and the average torque and torque ripple in the rotor according to the embodiment.

Embodiments of the present disclosure will be described below with reference to the drawings. Each embodiment described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, component placement and connection configurations, 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 recited in the independent claims that represent the superordinate concept of the present disclosure will be described as optional components.

Each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scale and other details are not necessarily the same in each figure. In all figures, the same reference numerals are used to refer to substantially identical components, and duplicate explanations are omitted or simplified.

In this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial terms. In this embodiment, for convenience, the direction in which the axis C of the rotating shaft 10 extends is referred to as the upward/downward direction. However, this upward/downward direction may differ from the actual upward/downward direction depending on the usage state of the motor 1, etc. In this embodiment, the radial direction of the rotor 2 and stator 3 is referred to as the "radial direction," and the rotation direction of the rotor 2 is referred to as the "circumferential direction." In other words, the direction perpendicular to the axis C of the rotating shaft 10 of the rotor 2 is referred to as the "radial direction," and the direction circumferentially around the axis C of the rotating shaft 10 is referred to as the "circumferential direction." The direction in which the axis C of the rotating shaft 10 extends (the longitudinal direction of the rotating shaft 10) is referred to as the "axial direction."

(Embodiment)
First, the overall configuration of a motor 1 according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the motor 1 according to the embodiment. Figure 2 is a perspective view of a core block 20a used in a rotor core 20 in a rotor 2 according to the embodiment.

As shown in Figure 1, motor 1 comprises rotor 2 and stator 3. Motor 1 is an inner rotor type motor in which rotor 2 is positioned inside stator 3. In other words, stator 3 is configured to surround rotor 2. Motor 1 is a brushless motor that does not use brushes.

The rotor 2 rotates due to the magnetic force generated in the stator 3. Specifically, the rotor 2 has a rotating shaft 10. The rotor 2 rotates around the axis C of the rotating shaft 10.

The rotor 2 generates a magnetic force that acts on the stator 3. The rotor 2 is configured with multiple 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 in which the axis C of the rotating shaft 10 extends (radial direction).

The rotor 2 is positioned with an air gap between it and the stator 3. Specifically, there is a tiny air gap between the surface of the rotor 2 and the surface of the stator 3. As will be described in more detail below, the rotor 2 has a rotating shaft 10, a rotor core 20, and a magnet 30. The rotor 2 is an IPM type rotor in which the magnet 30 is embedded inside the rotor core 20. Therefore, the motor 1 is an IPM motor.

The stator 3 is positioned opposite the rotor 2 with an air gap between them. The stator 3 is positioned outside the rotor 2. Specifically, the stator 3 is positioned so as to surround the rotor core 20 of the rotor 2.

The stator 3 generates a magnetic force that acts on the rotor 2. The stator 3 is configured so that north and south poles are generated alternately in the circumferential direction on the air gap surface between the stator 3 and the rotor core 20 of the rotor 2. The stator 3 and the rotor 2 form a magnetic circuit.

The stator 3 has a stator core 100 (stator core) and a winding coil 200.

The stator core 100 of the stator 3 generates magnetic force to rotate the rotor 2. The stator core 100 has multiple teeth 110 and a yoke 120. The multiple teeth 110 are magnetic pole teeth. The yoke 120 is a back yoke formed on the outside of each tooth 110. The yoke 120 is formed in an annular shape centered on the axis C of the rotating shaft 10.

The multiple teeth 110 protrude from the yoke 120 toward the rotor 2. Specifically, the multiple teeth 110 extend toward the axis C of the rotating shaft 10. The multiple teeth 110 are arranged at equal intervals in the circumferential direction, with slots formed between two adjacent teeth 110. Therefore, the multiple teeth 110 extend radially in a direction perpendicular to the axis C of the rotating shaft 10 (radial direction). As an example, the stator core 100 is provided with 12 teeth 110.

In this embodiment, the stator core 100 is a divided core divided into multiple core blocks 100a along the circumferential direction. In other words, the stator core 100 is composed of multiple core blocks 100a. The multiple core blocks 100a are arranged in an annular shape as a whole. Specifically, 12 core blocks 100a are arranged to form an annular shape. Adjacent two core blocks 100a are connected to each other.

The stator core 100 is divided into individual teeth 110. Therefore, each of the multiple core blocks 100a has one tooth 110. Each of the multiple core blocks 100a has an arc portion that is part of the yoke 120. The ends of this arc portion of two adjacent core blocks 100a are connected to each other.

Each tooth 110 has an extension 111 that extends circumferentially from the tip of the tooth 110 on its inner periphery. In other words, a pair of extensions 111 is formed at the tip of the tooth 110 on its inner periphery that faces the rotor 2. Each of the pair of extensions 111 is formed so as to protrude circumferentially from the tip of the tooth 110 on its inner periphery. Between two adjacent teeth 110, an opening 130 (slot open) exists between the extension 111 of one tooth 110 and the extension 111 of the other tooth 110.

The stator core 100 is, for example, a laminated body in which multiple steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The multiple steel plates are magnetic. The multiple steel plates are, for example, punched electromagnetic steel plates formed into a predetermined shape. The stator core 100 is divided into multiple core blocks 100a. Each of the multiple core blocks 100a of the stator core 100 is constructed by stacking multiple steel plates. In other words, each core block 100a is a laminated body in which multiple steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The multiple steel plates are fixed to each other by crimping, welding, or the like. The stator core 100 is not limited to a laminated body in which multiple steel plates are stacked, but may also be a bulk body constructed of a magnetic material.

The winding coil 200 is a stator coil wound around the stator core 100. The winding coil 200 is wound around each of the multiple teeth 110 of the stator core 100. In other words, the winding coil 200 is wound around each tooth 110 of the multiple core blocks 100a. Specifically, the winding coil 200 is wound around each of the multiple teeth 110 via an insulator (not shown). Each winding coil 200 is a concentrated winding coil wound around the corresponding tooth 110. Each winding coil 200 is housed in a slot in the stator core 100.

When current is applied to the winding coils 200, magnetic force is generated from each of the multiple teeth 110 of the stator core 100. For example, the multiple winding coils 200 are electrically connected as a three-phase winding so that the rotor 2 rotates as a three-phase synchronous motor. In other words, the motor 1 is an interior permanent magnet synchronous motor (IPMSM). In this case, the multiple winding coils 200 are composed of unit coils for each of the three phases: U, V, and W, which are electrically out of phase with each other by 120 degrees. In other words, the winding coils 200 attached to each tooth 110 are energized and driven by three-phase alternating current that is applied to each of the U, V, and W phases. This generates a main magnetic flux in each tooth 110 as a stator 3.

In the motor 1 configured in this manner, when current is applied to the winding coil 200 of the stator 3, a field current flows through the winding coil 200, generating a magnetic field. This generates magnetic flux that flows from the stator 3 toward the rotor 2. Specifically, magnetic flux is generated from each of the multiple teeth 110 of the stator core 100 in the stator 3 toward the rotor core 20 of the rotor 2. Meanwhile, in the rotor 2, magnetic flux that passes through the stator 3 is generated by the magnet 30 embedded in the rotor core 20. The magnetic force generated by the interaction between the magnetic flux generated by the stator 3 and the magnetic flux generated by the magnet 30 of the rotor 2 becomes torque that rotates the rotor 2. This causes the rotor 2 to rotate.

Next, the detailed configuration of the rotor 2 will be described using Figure 2 while also referring to Figure 1. Figure 2 is a perspective view of the core block 20a used in the rotor core 20 in the rotor 2 according to the embodiment.

As shown in Figure 1, the rotor 2 comprises a rotating shaft 10, a rotor core 20 through which the rotating shaft 10 is inserted, and a plurality of magnets 30 held by the rotor core 20.

The rotating shaft 10 has an axis C about which the rotor 2 rotates. The rotating shaft 10 extends in the direction of the axis C. The rotating shaft 10 is a long shaft. The rotating shaft 10 is a metal rod made of a metal material such as SUS (Steel Use Stainless Steel). The rotating shaft 10 is fixed to the rotor core 20. Although not shown, the rotating shaft 10 is fixed to the rotor core 20, for example, by penetrating the center of the rotor core 20 so as to protrude on both sides of the rotor core 20. A first portion of the rotating shaft 10 protruding on one side of the rotor core 20 is supported by a first bearing. A second portion of the rotating shaft 10 protruding on the other side of the rotor core 20 is supported by a second bearing. A load, such as a rotary fan driven by the motor 1, is attached to the first or second portion of the rotating shaft 10.

As shown in FIG. 1, the rotor core 20 is arranged with an air gap between it and the stator core 100 of the stator 3. The rotor core 20 is provided with a plurality of magnet arrangement holes 23 in which magnets 30 are arranged. The magnet arrangement holes 23 are through-holes that pass through the rotor core 20 in the direction in which the axis C of the rotating shaft 10 extends. The magnets 30 are inserted into the magnet arrangement holes 23. In other words, the plurality of magnets 30 are arranged inside the rotor core 20.

The multiple magnet arrangement holes 23 and the multiple magnets 30 are arranged in a ring shape around the rotating shaft 10. The multiple magnet arrangement holes 23 and the multiple magnets 30 are arranged at equal intervals along the circumferential direction. Ten magnet arrangement holes 23 are provided in the rotor core 20. Therefore, ten magnets 30 are embedded in the rotor core 20 at equal intervals along the circumferential direction around the rotating shaft 10.

The multiple magnet arrangement holes 23 and magnets 30 are arranged radially around the rotating shaft 10. Specifically, each of the multiple magnet arrangement holes 23 extends radially. The multiple long magnet arrangement holes 23 are formed in a spoke shape around the rotating shaft 10. Therefore, each of the multiple magnets 30 inserted into the multiple magnet arrangement holes 23 also extends radially. The multiple magnets 30 are arranged in a spoke shape around the rotating shaft 10. In other words, the rotor 2 is a spoke-type rotor in which the multiple magnets 30 are arranged radially. In a plan view, each magnet 30 is arranged so that its longitudinal direction is the radial direction of the rotor core 20. As an example, the planar shape of each magnet arrangement hole 23 and each magnet 30 is a rectangle with its longitudinal direction aligned with the radial direction. The planar shape of each of the multiple magnet arrangement holes 23 is the same. The planar shape of each of the multiple magnets 30 is the same.

The rotor core 20 is composed of two cores: an outer core 21 and an inner core 22. The outer core 21 is a first core located radially outward from the inner core 22. The inner core 22 is a second core located radially inward from the outer core 21. The outer core 21 surrounds the inner core 22.

The outer core 21 is the main core of the rotor core 20. The outer core 21 holds multiple magnets 30. In other words, multiple magnet placement holes 23 are provided in the outer core 21.

The inner core 22 holds the rotating shaft 10. The rotating shaft 10 passes through the inner core 22. The rotating shaft 10 is fixed to the inner core 22. Specifically, an insertion hole 22a is provided in the inner core 22. The rotating shaft 10 is fixed to the inner core 22 by being press-fitted or shrink-fitted into this insertion hole 22a. The inner core 22 is a cylindrical member that is shaped as a whole.

The rotor core 20 has multiple core blocks 20a divided along the circumferential direction. The outer core 21 of the rotor core 20 is divided along the circumferential direction. The outer core 21 is made up of multiple core blocks 20a. The outer core 21 is divided into the same number of parts as the number of magnets 30. The rotor core 20 holds 10 magnets 30. Therefore, the outer core 21 is made up of 10 core blocks 20a. The multiple core blocks 20a are arranged in a circular ring shape as a whole. Specifically, the 10 core blocks 20a are arranged to form a circular ring.

The multiple core blocks 20a are arranged so that two adjacent core blocks 20a do not come into contact with each other. The area between two adjacent core blocks 20a among the multiple core blocks 20a forms a magnet arrangement hole 23 in which a magnet 30 is arranged. In other words, each magnet 30 is sandwiched between two adjacent core blocks 20a.

The rotor core 20 is, for example, a laminated body formed by stacking multiple steel plates in the direction in which the axis C of the rotating shaft 10 extends. The multiple steel plates are magnetic. The multiple steel plates are, for example, punched electromagnetic steel plates formed into a predetermined shape. In this embodiment, the outer core 21 and the inner core 22 are each formed by stacking multiple steel plates. Specifically, each core block 20a in the outer core 21 is formed by stacking multiple steel plates. In other words, each core block 20a is a laminated body formed by stacking multiple steel plates in the direction in which the axis C of the rotating shaft 10 extends. The multiple steel plates are fixed to each other by crimping, welding, or the like. The rotor core 20 is not limited to a laminated body formed by stacking multiple steel plates. The rotor core 20 may be a bulk body formed by a magnetic material. In other words, each core block 20a and the inner core 22 may be a bulk body.

The multiple core blocks 20a that make up the outer core 21 are fixed to one another by resin 40. Specifically, the multiple core blocks 20a are injection molded to mold the multiple core blocks 20a with resin 40. In this embodiment, both the outer core 21 and the inner core 22 are fixed with resin 40. In other words, the multiple core blocks 20a (outer core 21) and the inner core 22 are molded integrally with resin 40. Resin 40 is present between the outer core 21 and the inner core 22. In this way, the rotor core 20 is molded with resin 40. The resin 40 may cover the radially outer portions of the outer core 21 (core blocks 20a) and the magnet 30.

Resin 40 is made of an insulating resin material with excellent thermal conductivity, such as polyester resin or epoxy resin. Resin 40 is also made of a thermosetting resin. One example of resin 40 is BMC (Bulk Molding Compound), but it may also be made of polybutylene terephthalate (PBT) or similar.

As shown in FIG. 1, a plurality of holes 24 are provided between two adjacent magnets 30 among the plurality of magnets 30 in the rotor core 20. The plurality of holes 24 are provided in the outer core 21. Specifically, as shown in FIGS. 1 and 2, the plurality of holes 24 are provided in each of the plurality of core blocks 20a. In other words, the plurality of holes 24 are provided in each of the plurality of core blocks 20a located between two adjacent magnets 30.

The multiple holes 24 are through-holes that penetrate the rotor core 20 in the direction in which the axis C of the rotating shaft 10 extends. Specifically, the multiple holes 24 penetrate the core block 20a. Each of the multiple holes 24 has a circular shape in a plan view. The multiple holes 24 are all the same size.

As shown in FIG. 1, in each of the multiple core blocks 20a, the multiple holes 24 are arranged symmetrically with respect to the magnetic pole center line L1 between two adjacent magnets 30. The magnetic pole center line L1 is a line passing through the axis C of the rotating shaft 10 and the midpoint between two adjacent magnets 30. The magnetic pole center line L1 is generated from each of the two adjacent magnets 30. In this embodiment, two holes 24 are provided in each core block 20a. In each core block 20a, the two holes 24 are arranged symmetrically with respect to the magnetic pole center line L1 between two adjacent magnets 30.

The multiple holes 24 are holes (mold positioning holes) for positioning the rotor core 20 relative to the mold used when molding the rotor core 20 with resin 40. In other words, the multiple holes 24 are holes for positioning the multiple core blocks 20a in the mold used when integrally molding the multiple core blocks 20a (outer cores 21) and the inner core 22 with resin 40. Specifically, mold pins are inserted into the multiple holes 24. Therefore, although in this embodiment the multiple holes 24 are through holes that penetrate the core block 20a, as long as mold pins can be inserted into the multiple holes 24, the multiple holes 24 do not have to penetrate the core block 20a. In other words, the multiple holes 24 may be recesses formed in the core block 20a.

When the rotor core 20 is molded with resin 40, mold pins are inserted into the multiple holes 24, so as shown in Figure 1, the multiple holes 24 are not filled with resin 40 in the finished rotor 2. However, resin 40 may be present in part of the interior of the holes 24.

A through hole 25 is provided between two adjacent magnets 30 among the multiple magnets 30 in the rotor core 20. The through hole 25 penetrates in the direction in which the axis C of the rotating shaft 10 extends. The through hole 25 is provided in the outer core 21. Specifically, as shown in Figures 1 and 2, a through hole 25 is provided in each of the multiple core blocks 20a. The through hole 25 penetrates the core block 20a. One through hole 25 is provided for each core block 20a. In each core block 20a, the through hole 25 is located radially inward from the multiple holes 24. The through hole 25 has a planar shape that tapers radially inward so that the distance between each of the two adjacent magnets 30 is constant.

The through holes 25 are holes (resin through holes) that are provided to allow the resin 40 to easily flow around when the rotor core 20 is molded with the resin 40. Therefore, as shown in Figure 1, in the completed rotor 2, the through holes 25 are filled with resin 40.

When the rotor core 20 is molded with resin 40, the magnet 30 is fixed to the rotor core 20 by the resin 40. In other words, the magnet 30 is integrally formed with the multiple core blocks 20a (outer core 21) and the inner core 22 by the resin 40. Instead of fixing the magnet 30 to the rotor core 20 with resin 40, adhesive may be separately filled into the magnet arrangement hole 23 of a molded product formed by molding the multiple core blocks 20a (outer core 21) and the inner core 22 with resin 40, and the magnet 30 may be inserted into the magnet arrangement hole 23 to fix the magnet 30 to the rotor core 20.

The multiple magnets 30 embedded in the rotor core 20 are magnetized permanent magnets. The magnetization direction of each magnet 30 is parallel to the circumferential direction of the rotor 2. The multiple magnets 30 are arranged so that the magnetic pole faces of the same polarity between two adjacent magnets 30 face each other. In other words, between two adjacent magnets 30, the magnetic pole face that becomes the south pole of one magnet 30 faces the magnetic pole face that becomes the south pole of the other magnet 30, or the magnetic pole face that becomes the north pole of one magnet 30 faces the magnetic pole face that becomes the north pole of the other magnet 30.

Magnet 30 is a ferrite magnet made of sintered ferrite. However, magnet 30 is not limited to a ferrite magnet. For example, magnet 30 may be a rare earth magnet. In this case, magnet 30 can be a neodymium rare earth magnet whose main components are neodymium, iron, and boron (Nd-Fe-B).

The magnetic flux distribution of the motor 1 configured in this manner is shown in Figure 3. Figure 3 is a diagram that schematically shows the magnetic flux distribution of the motor 1 according to the embodiment. In Figure 3, the areas indicated by dotted hatching indicate areas with high magnetic flux density.

In the motor 1, as shown in FIG. 3, holes 24 and through holes 25 are provided in the rotor core 20 of the rotor 2. Specifically, two holes 24 and one through hole 25 are provided in each block core 20a. In the rotor core 20, the portions of the rotor core 20 where the holes 24 and through holes 25 are provided have higher magnetic resistance than the portions surrounding the holes 24 and through holes 25. For this reason, the magnetic field lines extending from the magnets 30 toward the teeth 110 of the stator core 100 extend so as to avoid the holes 24 and through holes 25, which have higher magnetic resistance. Therefore, as shown by the dotted hatching in FIG. 3, in the region between two adjacent magnets 30 in the rotor core 20 (i.e., the core block 20a), the magnetic flux density is high in the portion between the through hole 25 and the magnet 30, the portion between the magnet 30 and the hole 24, and the portion between the two holes 24.

In this way, by providing holes 24 and through holes 25 between two magnets 30 in the rotor core 20, multiple paths for magnetic flux can be secured between two adjacent magnets 30. This reduces torque ripple. In particular, the holes 24 located on the outer periphery of the through holes 25 have a large effect on the main magnetic flux generated by the rotor core 20, and since multiple such holes 24 are provided, torque ripple can be effectively reduced. In this case, by reducing the difference in magnetic flux density between three locations in each core block 20a: between one of the two holes 24 and one of the two magnets 30, between the two holes 24, and between the other of the two holes 24 and the other of the two magnets 30, torque ripple can be further effectively reduced.

The multiple holes 24 are arranged symmetrically with respect to the magnetic pole center line L1 between two adjacent magnets 30. This allows the magnetic flux path in each core block 20a to be symmetric with respect to the magnetic pole center line L1. This further reduces torque ripple.

The multiple holes 24 are positioned so that the magnetic flux density between the multiple holes 24 when no load is present is ±40% or less of the magnetic flux density when no load is present between one of two adjacent magnets 30 and the hole 24 closest to that magnet 30. This reduces the difference in magnetic flux density along the paths of the multiple magnetic fluxes. Therefore, torque ripple can be reduced. The distance between the two holes 24 may also be ±85% of the distance between the magnet 30 and one of the two holes 24.

In this way, by providing holes 24 or through holes 25 between adjacent magnets 30 in the rotor core 20, torque ripple can be reduced.

In this case, providing holes 24 or through holes 25 that create magnetic resistance between adjacent magnets 30 in the rotor core 20 can reduce torque ripple, but it is thought that this will result in a decrease in average torque.

However, the present inventors investigated whether it would be possible to reduce torque ripple while suppressing the decrease in average torque. They discovered that, depending on the position of the holes 24 or through-holes 25 provided between adjacent magnets 30 in the rotor core 20, it would be possible to reduce torque ripple while suppressing the decrease in average torque. The results of this investigation are explained below.

First, the results of the study on the position of the holes 24 in the rotor core 20 will be explained using Figure 4, while also referring to Figure 3. Figure 4 is a diagram showing the relationship between the position of the holes 24 in the rotor core 20 and the average torque and torque ripple in the rotor 2 according to the embodiment.

In Figure 4, the horizontal axis indicates the position of the holes 24 in the rotor core 20. Specifically, the positions of the multiple holes 24 indicate the radial position when the position of the line L2 connecting the inner circumferential ends of two adjacent magnets 30 is set to 0%, and the position of the line L3 connecting the outer circumferential ends of two adjacent magnets 30 is set to 100%, as shown in Figure 3. In Figure 4, the vertical axis indicates the average torque and torque ripple. The average torque is expressed as a percentage when the initial average torque of the motor 1 is set to 100%. The torque ripple is expressed as a percentage, obtained by dividing the difference between the maximum and minimum torque generated over one rotation of the motor 1 by the average torque generated over one rotation.

As shown in Figure 4, it is preferable that the holes 24 are located at a position between 55% and 95% in the radial direction. This allows the initial average torque of the motor 1 to be maintained without reducing the average torque, while effectively reducing torque ripple.

As shown in Figure 4, it is even better if the multiple holes 24 are located at a position between 55% and 90% of the radial distance. This allows torque ripple to be reduced to the maximum extent possible without reducing the average torque.

Next, the results of the study on the position of the through-holes 25 in the rotor core 20 will be explained using Figure 5. Figure 5 is a diagram showing the relationship between the position of the through-holes 25 in the rotor core 20 and the average torque and torque ripple in the rotor 2 according to the embodiment.

In Figure 5, the horizontal axis indicates the position of the through hole 25 in the rotor core 20. Specifically, as shown in Figure 3, the position of the through hole 25 indicates the radial position of the outermost edge of the through hole 25, when the position of the line L2 connecting the inner ends of two adjacent magnets 30 is set to 0%, and the position of the line L3 connecting the outer ends of two adjacent magnets 30 is set to 100%. The innermost part of the through hole 25 (the apex of the acute angle in Figure 3) is fixed and remains unchanged. In Figure 5, the vertical axis indicates the average torque and torque ripple. This average torque and torque ripple are defined in the same way as in Figure 4 and are shown as percentages.

As shown in Figure 5, the through holes 25 are preferably located at a position no greater than 60% in the radial direction. This allows the torque ripple to be effectively reduced while maintaining the desired average torque of the motor 1 without reducing the average torque.

As shown in Figure 5, it is even better if the through holes 25 are located at a position no greater than 50% in the radial direction. This allows torque ripple to be reduced to the maximum extent possible without reducing the average torque.

As a result of research conducted by the inventors of this application, it was found that the average torque and torque ripple are also affected by the relationship between the position of the holes 24 in the rotor core 20 and the width of the openings 130 (slot openings) in the teeth 110 of the stator 3. The results of this research are explained using Figures 6 and 7.

FIG. 6 is a diagram illustrating the positional relationship between the positions of the holes 24 in the rotor core 20 and the tips of the extensions 111 of the teeth 110 in the stator 3 in the rotor 2 according to the embodiment. FIG. 7 is a diagram illustrating the relationship between the width of the openings 130 (slot openings) in the teeth 110 of the stator 3 and the average torque and torque ripple in the rotor 2 according to the embodiment.

In Figure 7, the horizontal axis represents the width of the opening 130 (slot open), which is the distance between the extension portions 111 of two adjacent teeth 110 in the stator core 100. Specifically, the width of the opening 130 is expressed as 0% when the distance between the extension portions 111 of two adjacent teeth 110 is zero (when the tips of the extension portions 111 are in contact), and 100% when there are no extension portions 111 on two adjacent teeth 110. In Figure 7, the vertical axis represents the average torque and torque ripple. This average torque and torque ripple are defined in the same way as in Figure 4 and are shown as percentages.

As shown in Figure 6, when the magnetic pole center line L1 between two adjacent magnets 30 in the rotor core 20 coincides with the center between the extension portions 111 of each of two adjacent teeth 110 among the multiple teeth 110 in the stator core 100, two tangent lines drawn from the axis C of the rotating shaft 10 to one of the multiple circular holes 24 are defined as lines L4 and L5. In Figure 7, line L4 corresponds to the case where the width of the opening 130 is 32%, and line L5 corresponds to the case where the width of the opening 130 is 72%.

Therefore, by positioning the tip of the extension portion 111 of the tooth 110 between the two lines L4 and L5, the width of the opening 130 can be set to 32% or more and 72% or less, as shown in Figure 7. This makes it possible to effectively reduce torque ripple without substantially reducing the average torque, as shown in Figure 7.

(Modification)
The rotor 2 and the 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 embodiments.

For example, in the above embodiment, the outer core 21 of the rotor core 20 of the rotor 2 is divided into multiple core blocks 20a. However, this is not limited to this. In other words, the outer core 21 may be composed of a single core. In this case, rather than the rotor core 20 being composed of two cores, the outer core 21 and the inner core 22, the entire rotor core 20 may be composed of a single core.

Furthermore, in the above embodiment, the shape of the magnet 30 inserted into the rotor core 20 of the rotor 2 is rectangular when viewed from above. However, this is not limited to this. For example, the shape of the magnet 30 when viewed from above may be trapezoidal or barrel-shaped.

Furthermore, in the above embodiment, the stator core 100 is divided into multiple core blocks 100a. However, this is not limited to this. Specifically, the stator core 100 may be composed of a single core.

Furthermore, in the above embodiment, the winding coil 200 of the stator 3 is wound around the stator core 100 using concentrated winding. However, this is not limited to this. For example, the winding coil 200 of the stator 3 may also be wound around the stator core 100 using distributed winding.

In addition, this disclosure also includes forms obtained by applying various modifications that a person skilled in the art would conceive of to the above-described embodiments and variations, or forms realized by arbitrarily combining the components and functions of the embodiments within the scope of this disclosure. This disclosure also includes any combination of two or more claims from the multiple claims set forth in the claims at the time of filing, to the extent that there is no technical contradiction. For example, when a dependent-form claim set forth in the claims at the time of filing is made into a multiple claim or multiple-multiple claim that cites all of the superordinate claims within the scope of technical contradiction, this disclosure also includes all combinations of claims included in that multiple claim or multiple-multiple claim.

The technology disclosed herein can be widely used in motors used in a variety of electrical appliances, including household and industrial equipment.

REFERENCE SIGNS LIST 1 Motor 2 Rotor 3 Stator 10 Rotating shaft 20 Rotor core 20a Core block 21 Outer core 22 Inner core 22a Insertion hole 23 Magnet placement hole 24 Hole 25 Through hole 30 Magnet 40 Resin 100 Stator core 100a Core block 110 Teeth 120 Yoke 130 Opening 111 Extension 200 Winding coil

Claims (14)

a rotation axis extending in an axial direction;
a rotor core including a plurality of core blocks through which the rotary shaft is inserted;
a plurality of magnets arranged annularly around the rotation axis inside the rotor core,
a plurality of holes are provided in each of the plurality of core blocks located between two adjacent magnets among the plurality of magnets in the rotor core,
When the position of a line connecting the inner circumferential ends of the two adjacent magnets is defined as 0%, and the position of a line connecting the outer circumferential ends of the two adjacent magnets is defined as 100%, the plurality of holes are provided at positions that are 55% to 95% in a radial direction that intersects with the axial direction.
Rotor. The plurality of holes are provided at positions that are 55% or more and 90% or less in the radial direction.
The rotor of claim 1 . The plurality of holes are provided between the two adjacent magnets symmetrically with respect to a magnetic pole center line generated from each of the two adjacent magnets.
The rotor of claim 1 . the plurality of holes penetrate the rotor core along the axial direction.
The rotor of claim 1 . the plurality of holes are provided at positions such that the magnetic flux density between the plurality of holes when no load is equal to or less than ±40% of the magnetic flux density between one of the two adjacent magnets and the hole closest to the one magnet when no load is applied,
The rotor of claim 1 . Furthermore, a through hole penetrating in the axial direction is provided between two adjacent magnets among the plurality of magnets in the rotor core,
the through hole is located radially inward of the plurality of holes,
When the position of a line connecting the inner circumferential ends of the two adjacent magnets is defined as 0% and the position of a line connecting the outer circumferential ends of the two adjacent magnets is defined as 100%, the through hole is provided at a position that is 60% or less in the radial direction.
A rotor according to any one of claims 1 to 5. The through hole is provided at a position of 50% or less in the radial direction.
The rotor of claim 6. The rotor core is molded with resin,
The through-hole is filled with the resin,
The plurality of holes are not filled with the resin.
The rotor of claim 6. a rotation axis extending in an axial direction;
a rotor core through which the rotary shaft is inserted;
a plurality of magnets arranged annularly around the rotation axis inside the rotor core,
The rotor core is provided with a through hole penetrating in the axial direction between two adjacent magnets among the plurality of magnets,
When the position of a line connecting the inner circumferential ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer circumferential ends of the two adjacent magnets is set to 100%, the through hole is provided at a position that is 60% or less in a radial direction that intersects with the axial direction.
Rotor. The through hole is provided at a position of 50% or less in the radial direction.
The rotor of claim 9. The rotor core is molded with resin,
The through hole is filled with the resin.
The rotor of claim 9. the rotor core has a plurality of core blocks divided along a circumferential direction surrounding the axial direction,
A region between two adjacent core blocks among the plurality of core blocks is a magnet arrangement hole in which the magnet is arranged.
A rotor according to any one of claims 1 to 5 and 9 to 11. A rotor according to any one of claims 1 to 5 and 9 to 11;
a stator that generates a magnetic force acting on the rotor,
Motor. the stator includes a stator core having a plurality of teeth extending toward the rotation shaft;
Each of the plurality of teeth has an extension portion extending from a tip portion on an inner circumferential side to both sides in the circumferential direction,
When the center between the extension portions of each of two adjacent teeth among the plurality of teeth coincides with the magnetic pole center line between the two adjacent magnets in the rotor core, a tip end of the extension portion is located between two tangent lines drawn from the axis of the rotation shaft to one of the plurality of holes.
14. The motor of claim 13.