Rotor and motor

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

[0001] The present disclosure relates to a rotor and a motor including the rotor.

[0002] Motors are used in a variety of electrical appliances, such as household appliances and industrial equipment. One type of motor is known as an interior permanent magnet (IPM) motor, which is a motor with embedded permanent magnets. The IPM motor includes an IPM-type rotor in which magnets are arranged in multiple magnet arrangement holes provided in a rotor core. A conventional IPM-type rotor is a spoke-type rotor in which multiple magnets are arranged radially.

[0003] As this type of IPM rotor, a spoke-type rotor in which holes are provided between adjacent magnets in a rotor core has been proposed (see Patent Document 1).

[0004] 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.

[0005] The inventors of the present application 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.

[0006] JP 2014-230348 A

[0007] An object of the present disclosure is to provide a rotor and a motor that can reduce torque ripple without reducing average torque.

[0008] In order to achieve the above object, one aspect of the rotor according to the present disclosure comprises a rotating shaft extending in an axial direction, a rotor core including a plurality of core blocks through which the rotating shaft is inserted, and a plurality of magnets arranged in a ring shape inside the rotor core around the rotating shaft, wherein each of the core blocks located between two adjacent magnets among the plurality of magnets in the rotor core has a plurality of holes, and when the position of a line connecting the inner ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer ends of the two adjacent magnets is set to 100%, the plurality of holes are located at positions between 55% and 95% in a radial direction intersecting the axial direction.

[0009] It is preferable that the plurality of holes are provided at positions that are 55% to 90% inclusive in the radial direction.

[0010] The plurality of holes may be provided between the two adjacent magnets symmetrically with respect to a magnetic pole center line generated from each of the two adjacent magnets.

[0011] The plurality of holes may penetrate the rotor core along the axial direction.

[0012] It is preferable that the multiple holes are arranged at positions where the magnetic flux density between the multiple holes at no load is ±40% or less of the magnetic flux density between one of the two adjacent magnets and the hole closest to that magnet at no load.

[0013] Furthermore, a through hole penetrating in the axial direction may be provided between two adjacent magnets among the multiple magnets in the rotor core, and the through hole may be located radially inward of the multiple holes, and when the position of a line connecting the inner ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer 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.

[0014] The through holes are preferably provided at positions that are 50% or less in the radial direction.

[0015] 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.

[0016] Another aspect of the rotor according to the present disclosure comprises a rotating shaft extending in an axial direction, a rotor core through which the rotating shaft is inserted, and a plurality of magnets arranged in a ring shape inside the rotor core 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 ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer ends of the two adjacent magnets is set to 100%, the through hole is located at a position that is 60% or less in a radial direction that intersects with the axial direction.

[0017] The through holes are preferably provided at positions that are 50% or less in the radial direction.

[0018] The rotor core may be molded with resin, and the through holes may be filled with the resin.

[0019] The rotor core may have a plurality of core blocks divided along a circumferential direction surrounding the axial direction, and the area between two adjacent core blocks among the plurality of core blocks may be a magnet arrangement hole in which the magnet is arranged.

[0020] Moreover, one aspect of a motor according to the present disclosure includes the rotor described above and a stator that generates a magnetic force acting on the rotor.

[0021] 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 among the plurality of teeth coincides with the magnetic pole center line between the two adjacent magnets in the rotor core, it is preferable that the tip of the extension portion is located between two tangent lines drawn from the axis of the rotating shaft to one of the plurality of holes.

[0022] According to the present disclosure, torque ripple can be reduced without reducing average torque.

[0023] 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 magnetic flux distribution in a motor according to an embodiment. FIG. 4 is a diagram showing the relationship between the position of a hole in a rotor core and average torque and torque ripple in a rotor according to an embodiment. FIG. 5 is a diagram showing the relationship between the position of a through hole in a rotor core and average torque and torque ripple in a rotor according to an embodiment. FIG. 6 is a diagram for explaining the positional relationship between the position of a hole in a rotor core and the extensions and tips of teeth in a stator in a rotor according to an embodiment. FIG. 7 is a diagram showing the relationship between the width of an opening in a stator tooth and average torque and torque ripple in a rotor according to an embodiment.

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, 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.

[0025] Each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scales and the like are not necessarily the same in each figure. In all figures, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0026] 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 recognition. In this embodiment, for convenience, the direction in which the axis C of the rotating shaft 10 extends is defined as the up-down direction. However, this up-down direction may differ from the actual up-down direction depending on the usage state of the motor 1, etc. In this embodiment, the radial direction of the rotor 2 and the stator 3 is defined as the "radial direction," and the rotation direction of the rotor 2 is defined as the "circumferential direction." In other words, the direction perpendicular to the axis C of the rotating shaft 10 of the rotor 2 is defined as the "radial direction," and the direction orbiting the axis C of the rotating shaft 10 is defined 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 defined as the "axial direction."

[0027] (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.

[0028] As shown in Fig. 1, the motor 1 includes a rotor 2 and a stator 3. The 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. The motor 1 is a brushless motor that does not use brushes.

[0029] The rotor 2 rotates due to a magnetic force generated in the stator 3. Specifically, the rotor 2 has a rotating shaft 10. The rotor 2 rotates around an axis C of the rotating shaft 10 as the center of rotation.

[0030] The rotor 2 generates a magnetic force that acts on the stator 3. The rotor 2 has a configuration in which a plurality of N and S poles, which form the main magnetic flux, are repeated 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).

[0031] 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 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.

[0032] The stator 3 is disposed opposite the rotor 2 with an air gap between them. The stator 3 is disposed outside the rotor 2. Specifically, the stator 3 is disposed so as to surround the rotor core 20 of the rotor 2.

[0033] 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.

[0034] The stator 3 includes a stator core 100 (stator core) and a winding coil 200 .

[0035] The stator core 100 of the stator 3 generates a magnetic force for rotating the rotor 2. The stator core 100 has a plurality of teeth 110 and a yoke 120. The plurality of 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.

[0036] The teeth 110 protrude from the yoke 120 toward the rotor 2. Specifically, the teeth 110 extend toward the axis C of the rotating shaft 10. The teeth 110 are arranged at equal intervals in the circumferential direction, with slots formed between two adjacent teeth 110. Therefore, the teeth 110 extend radially in a direction (radial direction) perpendicular to the axis C of the rotating shaft 10. As an example, the stator core 100 is provided with 12 teeth 110.

[0037] In this embodiment, the stator core 100 is a divided core divided into a plurality of core blocks 100a along the circumferential direction. That is, the stator core 100 is composed of a plurality of core blocks 100a. The plurality of core blocks 100a are arranged in an annular shape as a whole. Specifically, 12 core blocks 100a are arranged to form an annular shape. Two adjacent core blocks 100a are connected to each other.

[0038] 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 the arc portions of two adjacent core blocks 100a are connected to each other.

[0039] Each tooth 110 has an extension 111 that extends from the tip of the inner periphery of the tooth 110 to both sides in the circumferential direction. That is, a pair of extensions 111 is formed at the tip of the inner periphery of the tooth 110 that faces the rotor 2. Each of the pair of extensions 111 is formed to protrude in the circumferential direction from the tip of the inner periphery of the tooth 110. 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.

[0040] The stator core 100 is, for example, a laminated body in which a plurality of steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The plurality of steel plates are magnetic materials. The plurality of steel plates are, for example, punched electromagnetic steel plates formed into a predetermined shape. The stator core 100 is divided into a plurality of core blocks 100a. Each of the plurality of core blocks 100a of the stator core 100 is formed by stacking a plurality of steel plates. In other words, each core block 100a is a laminated body in which a plurality of steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The plurality of steel plates are fixed to one another by caulking, welding, or the like. The stator core 100 is not limited to a laminated body in which a plurality of steel plates are stacked, but may be a bulk body made of a magnetic material.

[0041] 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 of the stator core 100.

[0042] When current is applied to the winding coils 200, magnetic forces are 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 configured by unit coils for each of the 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 200 attached to each tooth 110 are energized and driven by three-phase alternating current that is applied to each of the U-phase, V-phase, and W-phase units. As a result, a main magnetic flux is generated in each tooth 110 as a stator 3.

[0043] In the motor 1 configured as described above, 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 a 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. A magnetic force generated by the interaction between the magnetic flux generated in the stator 3 and the magnetic flux generated by the magnet 30 of the rotor 2 becomes a torque that rotates the rotor 2. This causes the rotor 2 to rotate.

[0044] Next, a detailed configuration of the rotor 2 will be described with reference to Fig. 1 and Fig. 2. Fig. 2 is a perspective view of a core block 20a used in the rotor core 20 in the rotor 2 according to the embodiment.

[0045] As shown in FIG. 1 , the rotor 2 includes 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 .

[0046] 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 in a state where it penetrates the center of the rotor core 20 and protrudes to both sides of the rotor core 20. A first portion of the rotating shaft 10 protruding to one side of the rotor core 20 is supported by a first bearing. A second portion of the rotating shaft 10 protruding to 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.

[0047] As shown in Fig. 1 , rotor core 20 is arranged with an air gap between it and stator core 100 of stator 3. Rotor core 20 is provided with a plurality of magnet arrangement holes 23 in which magnets 30 are arranged. Magnet arrangement holes 23 are through-holes that pass through rotor core 20 along the direction in which axis C of rotating shaft 10 extends. Magnets 30 are inserted into magnet arrangement holes 23. In other words, the plurality of magnets 30 are arranged inside rotor core 20.

[0048] The multiple magnet arrangement holes 23 and the multiple magnets 30 are arranged in an annular shape around the rotating shaft 10. The multiple magnet arrangement holes 23 and the multiple magnets 30 are provided 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.

[0049] 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 in the radial direction. The multiple elongated 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 in the radial direction. 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 plan view shape of each magnet arrangement hole 23 and the plan view shape of each magnet 30 are both rectangular with the longitudinal direction aligned with the radial direction. The plan view shape of each of the multiple magnet arrangement holes 23 is the same. The plan view shape of each of the multiple magnets 30 is the same.

[0050] 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.

[0051] The outer core 21 is a main core of the rotor core 20. The outer core 21 holds a plurality of magnets 30. That is, a plurality of magnet arrangement holes 23 are provided in the outer core 21.

[0052] 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 having an overall cylindrical shape.

[0053] The rotor core 20 has a plurality of 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 composed of a plurality of 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 ten magnets 30. Therefore, the outer core 21 is composed of ten core blocks 20a. The plurality of core blocks 20a are arranged in an annular shape as a whole. Specifically, the ten core blocks 20a are arranged to form an annular shape.

[0054] 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.

[0055] The rotor core 20 is, for example, a laminated body in which a plurality of steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The plurality of steel plates are magnetic materials. The plurality of 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 a plurality of steel plates. Specifically, each core block 20a in the outer core 21 is formed by stacking a plurality of steel plates. That is, each core block 20a is a laminated body in which a plurality of steel plates are stacked in the direction in which the axis C of the rotating shaft 10 extends. The plurality of steel plates are fixed to one another by caulking, welding, or the like. The rotor core 20 is not limited to a laminated body in which a plurality of steel plates are stacked. The rotor core 20 may be a bulk body formed of a magnetic material. That is, each core block 20a and the inner core 22 may be a bulk body.

[0056] The multiple core blocks 20a constituting the outer core 21 are fixed to one another by the resin 40. Specifically, the multiple core blocks 20a are injection molded to mold the multiple core blocks 20a with the resin 40. In this embodiment, both the outer core 21 and the inner core 22 are fixed by the resin 40. That is, the multiple core blocks 20a (outer core 21) and the inner core 22 are integrally molded with the resin 40. The resin 40 is present between the outer core 21 and the inner core 22. In this manner, the rotor core 20 is molded with the resin 40. The resin 40 may cover the radially outer portions of the outer core 21 (core blocks 20a) and the magnet 30.

[0057] The resin 40 is made of an insulating resin material with excellent thermal conductivity, such as polyester resin or epoxy resin. The resin 40 is also made of a thermosetting resin. For example, the resin 40 is made of BMC (Bulk Molding Compound), but it may also be made of polybutylene terephthalate (PBT) or the like.

[0058] 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 the two adjacent magnets 30.

[0059] The holes 24 are through holes that penetrate the rotor core 20 along the direction in which the axis C of the rotating shaft 10 extends. Specifically, the holes 24 penetrate the core block 20a. Each of the holes 24 has a circular shape in a plan view. The holes 24 are all the same size.

[0060] As shown in FIG. 1 , in each of the multiple core blocks 20a, the multiple holes 24 are provided 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 the present embodiment, two holes 24 are provided in each core block 20a. In each core block 20a, the two holes 24 are provided symmetrically with respect to the magnetic pole center line L1 between two adjacent magnets 30.

[0061] The multiple holes 24 are holes (mold positioning holes) for positioning the rotor core 20 relative to a 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 a 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 the multiple holes 24 are through holes that penetrate the core block 20a in this embodiment, the multiple holes 24 do not have to penetrate the core block 20a as long as mold pins can be inserted into the multiple holes 24. In other words, the multiple holes 24 may be recesses formed in the core block 20a.

[0062] When the rotor core 20 is molded with the resin 40, mold pins are inserted into the holes 24, so that in the completed rotor 2, the holes 24 are not filled with the resin 40, as shown in Fig. 1. Note that the resin 40 may be present in part of the interior of the holes 24.

[0063] Of the multiple magnets 30 in the rotor core 20, a through hole 25 is provided between two adjacent magnets 30. 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 FIGS. 1 and 2 , the 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 with respect to the multiple holes 24. The shape of the through hole 25 in a plan view is tapered radially inward so that the distance between each of the two adjacent magnets 30 is constant.

[0064] 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 FIG. 1 , in the completed rotor 2, the through holes 25 are filled with the resin 40.

[0065] When the rotor core 20 is molded with the resin 40, the magnet 30 is fixed to the rotor core 20 by the resin 40. That is, the magnet 30 is integrally formed with the plurality of core blocks 20a (outer cores 21) and the inner core 22 by the resin 40. Instead of fixing the magnet 30 to the rotor core 20 by the resin 40, an adhesive may be separately filled into the magnet arrangement hole 23 of a molded product obtained by molding the plurality of core blocks 20a (outer cores 21) and the inner core 22 with the 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.

[0066] 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.

[0067] The magnet 30 is a ferrite magnet made of sintered ferrite. However, the magnet 30 is not limited to a ferrite magnet. For example, the magnet 30 may be a rare earth magnet. In this case, a neodymium rare earth magnet whose main components are neodymium, iron, and boron (Nd—Fe—B) can be used as the magnet 30.

[0068] The magnetic flux distribution of the motor 1 configured as above 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.

[0069] 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. Therefore, 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.

[0070] In this way, by providing the holes 24 and through holes 25 between the two magnets 30 in the rotor core 20, multiple paths for magnetic flux can be secured between the two adjacent magnets 30. This makes it possible to reduce torque ripple. In particular, the holes 24 located on the outer circumferential side of the through holes 25 have a large effect on the main magnetic flux generated by the rotor core 20, and since multiple holes 24 are provided, torque ripple can be effectively reduced. In this case, by reducing the difference in magnetic flux density among three locations in each core block 20a, namely, 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.

[0071] The holes 24 are arranged symmetrically with respect to the magnetic pole center line L1 between two adjacent magnets 30. This allows the magnetic flux paths in each core block 20a to be symmetrical with respect to the magnetic pole center line L1, thereby further reducing torque ripple.

[0072] The multiple holes 24 are positioned so that the magnetic flux density between the multiple holes 24 when no load is present is within ±40% of the magnetic flux density between one of two adjacent magnets 30 and the hole 24 closest to that magnet 30 when no load is present. This reduces the difference in magnetic flux density along the paths of the multiple magnetic flux. Therefore, torque ripple can be reduced. Note that the distance between the two holes 24 may be ±85% of the distance between the magnet 30 and one of the two holes 24.

[0073] In this way, by providing the holes 24 or through holes 25 between adjacent magnets 30 in the rotor core 20, torque ripple can be reduced.

[0074] In this case, if holes 24 or through holes 25 that create magnetic resistance are provided between adjacent magnets 30 in the rotor core 20, the torque ripple can be reduced, but it is thought that the average torque will decrease.

[0075] However, the present inventors have investigated whether it is possible to reduce torque ripple while suppressing a decrease in average torque, and have found that it is possible to reduce torque ripple while suppressing a decrease in average torque depending on the positions of the holes 24 or through holes 25 provided between adjacent magnets 30 in rotor core 20. The results of this investigation are described below.

[0076] First, the results of the study on the positions of the holes 24 in the rotor core 20 will be described using Fig. 4 while also referring to Fig. 3. Fig. 4 is a diagram showing the relationship between the positions of the holes 24 in the rotor core 20 and the average torque and torque ripple in the rotor 2 according to the embodiment.

[0077] In Fig. 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 radial positions when the position of a line L2 connecting the inner circumferential ends of two adjacent magnets 30 is set to 0% and the position of a line L3 connecting the outer circumferential ends of two adjacent magnets 30 is set to 100%, as shown in Fig. 3. In Fig. 4, the vertical axis indicates 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 torque and the minimum torque generated over one rotation of the motor 1 by the average torque generated over one rotation.

[0078] 4, the holes 24 are preferably provided at positions between 55% and 95% of the diameter of the rotor 1. This allows the torque ripple to be effectively reduced while maintaining the initial average torque of the motor 1 without reducing the average torque.

[0079] 4, it is more preferable that the holes 24 are provided at positions between 55% and 90% in the radial direction, which allows the torque ripple to be reduced to the maximum extent possible without reducing the average torque.

[0080] Next, the results of examining the positions of the through holes 25 of the rotor core 20 will be described with reference to Fig. 5. Fig. 5 is a diagram showing the relationship between the positions of the through holes 25 of the rotor core 20 and the average torque and torque ripple in the rotor 2 according to the embodiment.

[0081] In Fig. 5, the horizontal axis indicates the position of the through hole 25 in the rotor core 20. Specifically, the position of the through hole 25 indicates the radial position of the outermost side 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% as shown in Fig. 3, and the position of the line L3 connecting the outer ends of two adjacent magnets 30 is set to 100%. The innermost portion of the through hole 25 (the apex of the acute angle in Fig. 3) is fixed and remains unchanged. In Fig. 5, the vertical axis indicates the average torque and torque ripple. The average torque and torque ripple are defined in the same way as in Fig. 4 and are shown as percentages.

[0082] 5, the through holes 25 are preferably provided at a position not greater than 60% in the radial direction, which allows the motor 1 to maintain the desired average torque without reducing the average torque, while effectively reducing torque ripple.

[0083] 5, it is more preferable that the through holes 25 are provided at a position not exceeding 50% in the radial direction, thereby minimizing torque ripple without reducing the average torque.

[0084] As a result of investigations by the present inventors, it was found that the average torque and torque ripple are also affected by the relationship between the positions 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 investigation will be explained using FIGS. 6 and 7.

[0085] 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.

[0086] 7, the horizontal axis represents the width of the opening 130 (slot open), which is the distance between the extensions 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 extensions 111 of two adjacent teeth 110 is zero (when the tips of the extensions 111 are in contact), and as 100% when the extensions 111 are not present on the two adjacent teeth 110. In FIG. 7, the vertical axis represents the average torque and torque ripple. The average torque and torque ripple are defined in the same way as in FIG. 4 and are expressed as percentages.

[0087] As shown in Fig. 6, when the magnetic pole center line L1 between two adjacent magnets 30 in rotor core 20 coincides with the center between extension portions 111 of each of two adjacent teeth 110 among the plurality of teeth 110 in stator core 100, two tangent lines drawn from the axis C of rotating shaft 10 to one of the plurality of circular holes 24 are defined as lines L4 and L5. In Fig. 7, line L4 corresponds to the case where the width of opening 130 is 32%, and line L5 corresponds to the case where the width of opening 130 is 72%.

[0088] Therefore, by positioning the tip of the extension 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 Fig. 7. This makes it possible to effectively reduce torque ripple without substantially reducing the average torque, as shown in Fig. 7.

[0089] (Modification) The rotor 2 and the motor 1 according to the present disclosure have been described above based on the embodiment, but the present disclosure is not limited to the above embodiment.

[0090] 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. That is, the outer core 21 may be formed from a single core. In this case, instead of forming the rotor core 20 from two cores, the outer core 21 and the inner core 22, the entire rotor core 20 may be formed from a single core.

[0091] 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 limiting. For example, the shape of the magnet 30 when viewed from above may be trapezoidal or barrel-shaped.

[0092] In the above embodiment, the stator core 100 is divided into a plurality of core blocks 100a. However, this is not limiting. Specifically, the stator core 100 may be formed by a single core.

[0093] In the above embodiment, the winding coil 200 of the stator 3 is wound around the stator core 100 in a concentrated winding manner. However, this is not limiting. For example, the winding coil 200 of the stator 3 may be wound around the stator core 100 in a distributed winding manner.

[0094] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments and variations that would occur to a person skilled in the art, or forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. The present disclosure also includes any combination of two or more claims from the multiple claims set forth in the claims at the time of filing, provided that there is no technical contradiction. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of the technical contradiction, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claim.

[0095] The technology of the present disclosure can be widely applied to motors used in various electrical appliances such as household appliances and industrial appliances.

[0096] 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

1. A rotor comprising: a rotating shaft extending in an axial direction; a rotor core including a plurality of core blocks through which the rotating shaft is inserted; and a plurality of magnets arranged in a ring shape around the rotating shaft inside the rotor core, wherein each of the core blocks located between two adjacent magnets among the plurality of magnets in the rotor core has a plurality of holes, and when the position of a line connecting the inner ends of the two adjacent magnets is set to 0% and the position of a line connecting the outer ends of the two adjacent magnets is set to 100%, the plurality of holes are located at positions between 55% and 95% in a radial direction intersecting the axial direction.

2. The rotor according to claim 1, wherein the plurality of holes are provided at positions that are 55% to 90% of the total in the radial direction.

3. The rotor according to claim 1, wherein the plurality of holes are provided between the two adjacent magnets symmetrically with respect to the magnetic pole center lines generated by each of the two adjacent magnets.

4. The rotor according to claim 1, wherein the plurality of holes penetrate the rotor core along the axial direction.

5. A rotor as claimed in claim 1, wherein 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 said one magnet when no load is applied.

6. A rotor according to any one of claims 1 to 5, further comprising a through-hole penetrating in the axial direction between two adjacent magnets of the plurality of magnets in the rotor core, the through-hole being located radially inward of the plurality of holes, and the through-hole being located at a position that is 60% or less in the radial direction 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%.

7. The rotor according to claim 6, wherein the through holes are provided at positions that are 50% or less in the radial direction.

8. The rotor according to claim 6, wherein the rotor core is molded with resin, the through holes are filled with the resin, and the plurality of holes are not filled with the resin.

9. A rotor comprising: a rotating shaft extending in an axial direction; a rotor core through which the rotating shaft is inserted; and a plurality of magnets arranged in a ring shape around the rotating shaft inside the rotor core, 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 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 located at a position that is 60% or less in a radial direction that intersects with the axial direction.

10. The rotor according to claim 9, wherein the through holes are provided at positions that are 50% or less in the radial direction.

11. The rotor according to claim 9, wherein the rotor core is molded with resin, and the through holes are filled with the resin.

12. A rotor according to any one of claims 1 to 5 and 9 to 11, wherein the rotor core has a plurality of core blocks divided circumferentially around the axial direction, and the area between two adjacent core blocks among the plurality of core blocks is a magnet arrangement hole in which the magnet is arranged.

13. A motor comprising: a rotor according to any one of claims 1 to 5 and 9 to 11; and a stator that generates a magnetic force acting on the rotor.

14. The motor described in claim 13, wherein 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 an inner peripheral tip portion 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 center line between the two adjacent magnets in the rotor core, the tip of the extension portion is located between two tangent lines drawn from the axis of the rotating shaft to one of the plurality of holes.

Images