WO2022219942A1

WO2022219942A1 - Rotor and electric motor

Info

Publication number: WO2022219942A1
Application number: PCT/JP2022/007903
Authority: WO
Inventors: 慶一郎額田; 修悟福田; 浩司植田
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2021-04-13
Filing date: 2022-02-25
Publication date: 2022-10-20
Also published as: JPWO2022219942A1

Abstract

Provided is a rotor and an electric motor capable of reducing torque ripple. The rotor comprises: a rotor core (20) having a plurality of magnet placement holes (21); a plurality of permanent magnets (30) respectively placed inside the plurality of magnet placement holes (21); and a rotating shaft (10) fixed to the rotor core (20). The plurality of magnet placement holes (21) are radially provided about the rotating shaft (10), and the permanent magnets (30) are each provided with a projection portion (32) at a corner portion (30a) in a plan view.

Description

rotor and motor

The present disclosure relates to rotors and electric motors used in various devices including household electrical devices and industrial devices.

Electric motors are used in various electrical equipment such as household equipment and industrial equipment. An IPM (Interior Permanent Magnet) motor is known as an electric motor. The rotor of the IPM motor includes, for example, a rotor core, permanent magnets arranged in each of a plurality of magnet arrangement holes provided in the rotor core, and magnets extending through the rotor core. and a rotating shaft fixed to. In the IPM motor, magnetic flux generated by the permanent magnet of the rotor is passed through the stator to generate torque for rotating the rotor.

Conventionally, as this type of motor, an IPM motor is known which includes a rotor in which a plurality of magnet arrangement holes in a rotor core are radially provided (Patent Document 1).

JP 2017-46386 A

In conventional rotors, a predetermined space is sometimes provided between the rotor core and the permanent magnets in order to improve the insertability of the permanent magnets into the magnet placement holes. In this case, when the permanent magnets are inserted into the magnet arrangement holes, there is a possibility that the arrangement positions of the permanent magnets in the magnet arrangement holes vary. As a result, the difference in magnetic flux density between the magnetic poles of each permanent magnet and that of the other permanent magnets is increased, resulting in a problem of increased cogging torque.

The present disclosure is intended to solve the above problems, and aims to provide a rotor and an electric motor that can reduce cogging torque.

A rotor according to a first aspect of the present disclosure includes a rotor core having a plurality of magnet placement holes, a plurality of permanent magnets arranged inside the plurality of magnet placement holes, and fixed to the rotor core. and a rotating shaft, and each of the plurality of permanent magnets is provided with a protrusion at a corner in a plan view.

In the rotor according to the second aspect of the present disclosure, in the first aspect, the outer peripheral surface of the projecting portion is arcuate.

In the electric motor according to a third aspect of the present disclosure, in the second aspect, the corners of the inner surface of each of the plurality of magnet placement holes are arcuate, and the radius of curvature of the corners of the inner surface of the magnet placement holes is greater than the radius of curvature of the protrusion. The radius of curvature of the outer peripheral surface is larger.

In any one of the first to third aspects of the electric motor according to the fourth aspect of the present disclosure, the plurality of magnet arrangement holes are provided radially around the rotation axis.

An electric motor according to a fifth aspect of the present disclosure, in any one of the first to fourth aspects, is characterized in that the surface of the permanent magnet is covered with a coating layer made of resin or metal, and the projecting portion is composed of the coating layer. there is

An electric motor according to a sixth aspect of the present disclosure includes the rotor according to any one of the first to fifth aspects, and a stator arranged to face the rotor and generating a magnetic force acting on the rotor. ing.

According to the present disclosure, it is possible to provide a rotor and an electric motor that can reduce cogging torque.

1 is a perspective view of an electric motor according to an embodiment of the present disclosure; FIG. A perspective view of a rotor of the motor A plan view of the main part of the rotor of the motor An enlarged plan view of the main part of the rotor of the same electric motor.

An embodiment of the present disclosure will be described below. It should be noted that each of the embodiments described below is a specific example of the present disclosure. Therefore, numerical values, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are examples and are not intended to limit the present disclosure. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in independent claims representing the highest concept of the present disclosure will be described as optional constituent elements.

In addition, each figure is a schematic diagram and is not necessarily strictly illustrated. In addition, in each figure, the same code|symbol is attached|subjected to the substantially same structure as other figures, and the overlapping description is abbreviate|omitted or simplified.

(Embodiment)
First, a schematic configuration of an electric motor 1 according to an embodiment will be described with reference to FIG. 1 . FIG. 1 is a perspective view of an electric motor 1 according to an embodiment.

As shown in FIG. 1, the electric motor 1 includes a rotor 2 and a stator 3. Electric motor 1 in the present embodiment is an inner rotor type motor in which rotor 2 is arranged inside stator 3 . That is, the stator 3 is configured to surround the rotor 2 .

The rotor 2 (rotor) is rotated by the magnetic force generated in the stator 3. Specifically, the rotor 2 has a rotating shaft 10 and rotates about an axis C of the rotating shaft 10 as a rotation center.

The rotor 2 generates a magnetic force that acts on the stator 3. The rotor 2 has a structure in which a plurality of N poles and S poles, which are main magnetic fluxes, are repeatedly present in the circumferential direction. In the present embodiment, the direction of the main magnetic flux generated by the rotor 2 is perpendicular to the direction of the axis C of the rotating shaft 10 (rotating shaft direction). That is, the direction of the main magnetic flux generated by the rotor 2 is the radial direction.

The rotor 2 is arranged with the stator 3 through an air gap. Specifically, a minute air gap exists between the surface of the rotor 2 and the surface of the stator 3 . Although details will be described later, the rotor 2 is an embedded permanent magnet rotor (IPM rotor) in which permanent magnets are embedded in an iron core. Therefore, electric motor 1 in the present embodiment is an IPM motor.

The stator 3 (stator) is arranged to face the rotor 2 via an air gap, and generates magnetic force acting on the rotor 2 . Specifically, the stator 3 is arranged so as to surround the rotor core 20 of the rotor 2 . The stator 3 forms a magnetic circuit together with the rotor 2 .

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

A plurality of teeth 3a1 projecting toward the rotor core 20 of the rotor 2 are provided on the stator core 3a. Specifically, the plurality of teeth 3 a 1 are provided so as to protrude toward the axis C of the rotating shaft 10 . Moreover, the plurality of teeth 3a1 are provided at regular intervals in the circumferential direction. Therefore, the multiple teeth 3a1 radially extend in a direction perpendicular to the axis C of the rotating shaft 10 (radial direction).

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

The winding coil 3b is wound around each of the plurality of teeth 3a1 of the stator core 3a. Specifically, the winding coil 3b is wound around each tooth 3a1 via an insulator. Each winding coil 3b is composed of unit coils of three phases, U-phase, V-phase and W-phase, which are electrically 120 degrees out of phase with each other. That is, the winding coil 3b wound around each tooth 3a1 is energized and driven by a three-phase alternating current that is energized in phase units of the U phase, the V phase, and the W phase. Thereby, the main magnetic flux of the stator 3 is generated in each tooth 3a1.

The winding coil 3b is made of a metal material such as copper whose surface is coated with an insulating film, and has a circular or rectangular cross section.

In the electric motor 1 configured in this manner, when the winding coil 3b of the stator 3 is energized, a field current flows through the winding coil 3b to generate a magnetic field. Thereby, a magnetic flux is generated from the stator 3 toward the rotor 2 . On the other hand, the rotor 2 generates a magnetic flux directed toward the stator 3 . That is, the permanent magnets of rotor 2 generate a magnetic flux that passes through stator 3 . The magnetic force generated by the interaction between the magnetic flux generated by the stator 3 and the magnetic flux generated by the rotor 2 becomes torque for rotating the rotor 2 , and the rotor 2 rotates about the rotation axis 10 .

Next, the detailed configuration of the rotor 2 according to the present embodiment will be described using FIGS. 2 and 3 while referring to FIG. 1. FIG. FIG. 2 is a perspective view of the rotor 2 according to the embodiment. FIG. 3 is a plan view of main parts of the rotor 2 according to the embodiment. 2 and 3, the rotating shaft 10 is omitted.

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

The rotating shaft 10 is a long shaft that serves as the center when the rotor 2 rotates. The rotating shaft 10 is, for example, a metal rod and fixed to the center of the rotor 2 . Specifically, the rotating shaft 10 is fixed to the rotor core 20 . In the present embodiment, rotating shaft 10 is fixed to rotor core 20 while penetrating through the center of rotor core 20 so as to protrude from both sides of rotor 2 . The rotating shaft 10 is fixed to the rotor core 20 by being press-fitted into a through hole 20a formed in the center of the rotor core 20 or by shrink fitting.

Although not shown, a first portion of the rotating shaft 10 projecting to one side of the rotor 2 is supported by a first bearing, and a second portion of the rotating shaft 10 projecting to the other side of the rotor 2 is supported by a first bearing. It is supported by two bearings. A load driven by the electric motor 1 is attached to the first portion or the second portion of the rotating shaft 10 .

The rotor core 20 (rotor core) is composed of, for example, a plurality of steel plates laminated in the direction of the axis C of the rotating shaft 10 . Each of the plurality of steel plates is, for example, an electromagnetic steel plate punched into a predetermined shape, and fixed to each other by caulking or the like. Note that the rotor core 20 is not limited to a laminate of a plurality of steel plates, and may be a bulk body made of a magnetic material.

The rotor core 20 is a core having a plurality of magnet placement holes 21. A plurality of magnet arrangement holes 21 are holes for magnet arrangement in which permanent magnets 30 are arranged. Specifically, a permanent magnet 30 is inserted into the magnet placement hole 21 . That is, the magnet arrangement hole 21 is a magnet insertion hole into which the permanent magnet 30 is inserted. One permanent magnet 30 is inserted into each magnet placement hole 21 . As an example, the rotor 2 is a ten-pole rotor having ten magnetic poles. Therefore, the rotor core 20 is provided with 10 magnet placement holes 21 and 10 permanent magnets 30 . Note that the present invention is not particularly limited to this, and can be applied to other numbers of magnetic poles.

Also, in the present embodiment, the magnet placement hole 21 is a through hole that penetrates the rotor core 20 along the direction of the axis C of the rotating shaft 10 . Therefore, the cross-sectional shape of the magnet arrangement hole 21 is the same in the direction of the axis C of the rotating shaft 10 in any cross section taken along a plane orthogonal to the rotating shaft 10 . In other words, all the steel plates forming the rotor core 20 are formed with the magnet arrangement holes 21 having the same shape. Note that the magnet arrangement hole 21 may not be a through hole as long as the permanent magnet 30 can be arranged.

As shown in FIGS. 1 and 2, the plurality of magnet arrangement holes 21 are radially provided around the rotating shaft 10. As shown in FIGS. Also, the plurality of magnet placement holes 21 are provided at regular intervals along the circumferential direction of the rotor core 20 (the rotation direction of the rotating shaft 10). Each of the plurality of magnet arrangement holes 21 extends in the radial direction of the rotor core 20 (the direction orthogonal to the direction of the axis C of the rotating shaft 10) in plan view. That is, the magnet placement holes 21 are elongated in the radial direction of the rotor core 20, and the length in the radial direction is longer than the length in the rotational direction (circumferential direction). The magnet arrangement hole 21 may be elongated in the rotational direction (circumferential direction) of the rotor core 20, and the length in the rotational direction (circumferential direction) may be longer than the radial length.

A plurality of elongated magnet placement holes 21 are formed in the shape of spokes around the rotating shaft 10 . That is, the rotor 2 is a spoke-type IPM rotor, and the electric motor 1 is a spoke-type IPM motor. In the present embodiment, the plan view shape of each magnet placement hole 21 is substantially rectangular with the radial direction of the rotor core 20 as its longitudinal direction. In addition, the planar view shapes of the plurality of magnet placement holes 21 are the same.

As shown in FIG. 2 , a permanent magnet 30 is inserted into each of the magnet arrangement holes 21 of the rotor 2 along the direction of the axis C of the rotating shaft 10 , and the permanent magnets 30 are inserted into each of the plurality of magnet arrangement holes 21 . placed. In the present embodiment, the permanent magnet 30 is inserted from above (above the paper) the axis C of the rotating shaft 10, but the permanent magnet 30 may be inserted from below (below the paper).

　In the present embodiment, the permanent magnet 30 is, for example, a sintered magnet. The plurality of permanent magnets 30 are arranged such that the magnetic pole direction is in the circumferential direction of the rotor core 20 (the rotation direction of the rotating shaft 10). That is, the permanent magnet 30 is magnetized so that the direction of the magnetic poles is the circumferential direction of the rotor core 20 . It should be noted that the two adjacent permanent magnets 30 have opposite magnetic pole directions of the S pole and the N pole.

The planar view shape and size of the permanent magnet 30 are substantially the same as the planar view shape and size of the magnet placement hole 21 , and the permanent magnet 30 is fitted in the magnet placement hole 21 . Therefore, the planar view shape of the permanent magnet 30 is an elongated substantially rectangular shape. As an example, the permanent magnet 30 is a plate-like rectangular parallelepiped having a thickness in a direction perpendicular to the radial direction of the rotor core 20 . Note that the permanent magnet 30 in each magnet placement hole 21 may be divided into a plurality of pieces.

In each magnet placement hole 21 , there is a gap (space, clearance) of a certain size between the outer surface of the permanent magnet 30 and the inner surface of the magnet placement hole 21 . An adhesive may be provided in this gap for adhesively fixing the permanent magnet 30 to the magnet arrangement hole 21 . On the other hand, the adhesive may not be provided in this gap.

The permanent magnet 30 is composed of, for example, a Nd--Fe--B based sintered magnet or ferrite sintered magnet. Alternatively, it may be a bonded magnet formed of magnet powder such as Nd--Fe--B magnet powder or ferrite magnet powder, a resin material and a small amount of additives.

The permanent magnets 30 may be magnetized after being placed in the magnet placement holes 21, or may be magnetized in advance before the permanent magnets 30 are inserted into the magnet placement holes 21. However, considering the workability of inserting the permanent magnet 30 into the magnet arrangement hole 21, it is better to magnetize the permanent magnet 30 after inserting it into the magnet arrangement hole 21. FIG.

Also, the permanent magnet 30 is covered with a covering material made of resin to form a covering layer 31 to cover the periphery of the permanent magnet 30 .

As shown in FIG. 3, each permanent magnet 30 has a projecting portion 32 at each of four corners 30a in a plan view (viewed from the direction of the axis C of the rotating shaft 10). The protruding portion 32 has an arc-shaped outer peripheral surface. The protruding portion 32 protrudes from the permanent magnet 30 along a line connecting the center of the permanent magnet 30 and the corner portion 30a in plan view. The permanent magnet 30 is fixed to the inner surface of the magnet placement hole 21 by the four protrusions 32 .

The projecting portion 32 is formed entirely along the direction of the axis C of the rotating shaft 10 . That is, the projecting portion 32 is provided over the entire permanent magnet 30 in the vertical direction (rotational axis direction). Note that the projecting portions 32 may be formed only on the upper and lower portions of the permanent magnet 30 in the vertical direction (rotational axis direction).

The protruding part 32 is configured by molding a part of the covering layer 31 so as to protrude. Although the permanent magnet 30 itself may be configured to partially protrude, it is preferable to form it on the coating layer 31 from the viewpoint of ease of production. The four protrusions 32 are substantially the same in shape and size.

The projecting portion 32 is in contact with the corner portion 21 a of the inner surface of the magnet placement hole 21 . Specifically, the projecting portion 32 is in contact with two inner surfaces of the magnet placement hole 21 that are connected via the corner portion 21a. Since the outer peripheral surface of the protruding portion 32 is arcuate, the area of the contact portion between the inner surface of the magnet placement hole 21 and the protruding portion 32 in a plan view can be reduced. As a result, friction when inserting the permanent magnets 30 into the magnet arrangement holes 21 can be reduced, and problems such as damage to the coating layer 31 covering the permanent magnets 30 and deformation of the rotor core 20 are less likely to occur. Furthermore, since the projecting portion 32 is composed of the coating layer 31 made of resin, it is possible to prevent damage to the rotor core 20 during insertion.

FIG. 4 is a partially enlarged plan view of the rotor 2 showing another example of the present embodiment. As shown in FIG. 4, the inner peripheral surface of the corner 21a of the inner surface of the magnet placement hole 21 is arcuate. Furthermore, as shown in FIG. 4 , the radius of curvature of the outer peripheral surface of the projecting portion 32 is larger than the radius of curvature of the corners 21 a of the inner surface of the magnet placement hole 21 . The radius of curvature represents the radius of the arc. Thereby, the position of the projecting portion 32 (permanent magnet 30) is fixed.

Conversely, if the radius of curvature of the outer peripheral surface of the protruding portion 32 is smaller, the corner portion 21a of the inner surface of the arc-shaped magnet placement hole 21 and the outer peripheral surface of the arc-shaped protruding portion 32 will come into contact with each other. It may rotate along the corner 21a and be fixed in a rotated state. At this time, the rotating state of each permanent magnet 30 becomes uneven. As a result, the difference in the amount of magnetic flux density between the magnetic poles of each permanent magnet 30 and the other permanent magnets 30 increases, resulting in an increase in cogging torque.

With the configuration as described above, the permanent magnets 30 inserted into the respective magnet arrangement holes 21 are reliably fixed substantially in the center of the magnet arrangement holes 21 .

Therefore, in each magnet placement hole 21, variations in placement locations of the permanent magnets 30 can be suppressed. As a result, the difference in the amount of magnetic flux density between each permanent magnet 30 and the other permanent magnets 30 can be reduced, and it is possible to prevent an increase in torque ripple and an increase in cogging torque.

Furthermore, since there is a space between the portion of the permanent magnet 30 where the projecting portion 32 is not formed and the inner surface of the magnet arranging hole 21, if an adhesive is formed in this space, the permanent magnet 30 can be removed from the magnet arranging hole. 21 can be held securely.

On the other hand, if the protruding portion 32 is not formed and there is no space, there is a possibility that the permanent magnet 30 cannot be held because there is no adhesive allowance.

In the above embodiment, the surface of the permanent magnet 30 is covered with the coating layer 31 made of resin, but the coating layer 31 is not limited to resin, and may be made of metal or may contain metal. That is, the surface of the permanent magnet 30 may be covered with a coating layer 31 made of metal, or may be covered with a coating layer 31 made of resin containing metal. In addition, copper, nickel, or aluminum is mentioned as a metal used here.

It should be noted that the above embodiment is merely an example, and the present disclosure is not limited to this, and can be modified as appropriate. For example, part of the configurations of the above embodiments may be replaced with other known configurations. Configurations not mentioned in the above embodiments are optional, and for example, known configurations can be appropriately selected and combined with the present disclosure.

The rotor and the electric motor according to the present disclosure can be widely used in electric motors and the like used in various devices including household electrical equipment and industrial equipment.

Reference Signs List 1 electric motor 2 rotor 3 stator 3a stator core 3a1 tooth 3b winding coil 10 rotating shaft 20 rotor core 21 magnet placement hole 21a corner 30 permanent magnet 30a corner 31 coating layer 32 protrusion

Claims

a rotor core having a plurality of magnet placement holes;
a plurality of permanent magnets respectively arranged inside the plurality of magnet arrangement holes;
and a rotating shaft fixed to the rotor core,
Each of the plurality of permanent magnets has a protrusion at a corner in a plan view,
rotor.
The rotor according to claim 1, wherein the outer peripheral surface of the protrusion is arcuate.
3. The method according to claim 2, wherein the corners of the inner surface of the magnet arrangement hole are arcuate, and the radius of curvature of the outer peripheral surface of the protrusion is larger than the radius of curvature of the corners of the inner surface of the magnet arrangement hole. rotor.
The rotor according to any one of claims 1 to 3, wherein the plurality of magnet arrangement holes are provided radially around the rotation axis.
The rotor according to any one of claims 1 to 4, wherein the surface of said permanent magnet is covered with a coating layer made of resin or metal, and said protruding portions are constituted by said coating layer.
An electric motor, comprising: the rotor according to any one of claims 1 to 5; and a stator arranged to face the rotor and generating a magnetic force acting on the rotor.