WO2023276514A1

WO2023276514A1 - Rotor, method for manufacturing same, and electric motor

Info

Publication number: WO2023276514A1
Application number: PCT/JP2022/021825
Authority: WO
Inventors: 修悟福田
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2021-06-30
Filing date: 2022-05-27
Publication date: 2023-01-05
Also published as: JPWO2023276514A1

Abstract

The present invention reduces the cogging torque of a rotor and provides an electric motor provided with this rotor. The present invention comprises a rotor core (20) having a plurality of magnet placement holes (21), a plurality of permanent magnets (30) placed in the plurality of magnet placement holes (21), respectively, and a rotary shaft (10) fixed to the rotor core (20). The permanent magnet (30) placed inside each of the plurality of magnet placement holes (21) has two side surfaces facing at least the rotation direction, and the two side surfaces are covered with a magnetically conductive resin (31). The permanent magnet (30) is fixed to the magnet placement hole (21) by the magnetically conductive resin layer (31).

Description

ROTOR, MANUFACTURING METHOD THEREOF, AND ELECTRIC 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. a rotating shaft fixed to the 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, there has been known a spoke-type IPM motor having a rotor in which a plurality of magnet arrangement holes in a rotor iron core are radially provided (Patent Document 1). Since the spoke-type IPM motor has permanent magnets whose length in the radial direction is longer than their length in the circumferential direction, the surface area of the permanent magnets can be increased. Thereby, the magnetic flux of the permanent magnets passing through the stator, that is, the magnetic flux of the permanent magnets contributing to the torque can be increased.

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 a permanent magnet is inserted into the magnet placement hole, the permanent magnet is magnetically attracted to either the left or right inner surface of the magnet placement hole (left or right in the circumferential direction when viewed from the axial direction). In a plurality of magnet arrangement holes, if the attraction points of the permanent magnets vary in the circumferential direction, variations in the amount of magnetic flux density of the magnetic poles of the permanent magnets increase, resulting in a problem of increased cogging torque.

The present disclosure aims to solve the above problems, and aims to provide a rotor capable of reducing cogging torque, a method for manufacturing the same, and an electric motor.

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 respectively arranged in the plurality of magnet placement holes, and fixed to the rotor core and a rotating shaft. Each of the plurality of permanent magnets is covered with magnetically conductive resin on at least two side faces facing in the direction of rotation. Each of the plurality of permanent magnets is fixed to a corresponding one of the plurality of magnet placement holes by the magnetically conductive resin layer.

A method for manufacturing a rotor according to a second aspect of the present disclosure includes forming the magnetism-permeable resin layer on at least two side surfaces of the permanent magnets of the rotor facing in the rotation direction, and then magnetizing the permanent magnets. After that, the permanent magnet having the magnetically conductive resin layer formed on the two side surfaces is inserted into the magnet arrangement hole.

An electric motor according to a third aspect of the present disclosure includes the rotor, and a stator arranged to face the rotor and generating a magnetic force acting on the rotor.

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 same electric motor. A plan view of the main part of the rotor of the motor Sectional drawing which shows the manufacturing method of the rotor of the same electric motor. A plan view near a magnet arrangement hole of an electric motor according to a first modification of an embodiment of the present disclosure A plan view near a magnet arrangement hole of an electric motor according to a second modification of an embodiment of the present disclosure

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 placement 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 plan view shape of each of the plurality of magnet placement holes 21 is the same as each other.

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 the axis C of the rotating shaft 10 (above the paper surface), but the permanent magnet 30 may be inserted from below (above the paper surface).

　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 plan view shape of the permanent magnet 30 is substantially the same as the plan view shape of the magnet arrangement hole 21, and the size is slightly smaller. The permanent magnets 30 are fitted in the magnet placement holes 21 . 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 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.

In addition, the permanent magnet 30 is surrounded by a magnetically conductive resin layer 31 made of resin and a magnetically conductive material. The magnetically conductive material is composed of, for example, a ferromagnetic material such as iron or nickel. The resin is, for example, a thermoplastic resin having a melting point of 130° C. or higher, such as polyethylene, polypropylene, or polyamide.

The magnetically conductive material is, for example, powdery and dispersed in resin. As shown in FIG. 2, when the permanent magnets 30 are inserted into each of the magnet arrangement holes 21, the permanent magnets 30 are in a state where at least two side surfaces facing in the direction of rotation are covered with the magnetically conductive resin layer 31. .

As shown in FIG. 3, each magnet placement hole 21 is provided with two

inner surfaces

21a and 21b facing each other in the circumferential direction (rotating direction of the rotating shaft 10) in plan view. The permanent magnet 30 is arranged so as not to be in direct contact with the two

inner surfaces

21a and 21b. There are gaps between the two side surfaces of the permanent magnet 30 facing in the direction of rotation and the

inner surfaces

21a and 21b of the magnet arrangement hole 21, respectively, and the magnetism-permeable resin layer 31 is arranged in these gaps. That is, each magnet placement hole 21 is occupied by the permanent magnet 30 and the magnetically conductive resin layer 31 at least in the direction of rotation. The permanent magnet 30 is fixed in the magnet arrangement hole 21 by the magnetically conductive resin layer 31 .

In the circumferential direction, the total thickness of the permanent magnets 30 and the magnetism-permeable resin layer 31 is approximately equal to the width of the magnet placement hole 21 or slightly wider than the width of the magnet placement hole 21 . Even if the width of the magnet placement hole 21 is wider than the width of the magnet placement hole 21, the outer magnetism-permeable resin layer 31 has resin and is therefore flexible. A stress acts on the resin layer 31 . As a result, the magnetism-permeable resin layer 31 is pushed in by the

inner surfaces

21a and 21b, and after insertion, stress is also applied from the permanent magnet 30 side toward the

inner surfaces

21a and 21b of the magnet arrangement hole 21. are reliably held in the magnet placement hole 21 .

In addition, the magnetic flux density of the permanent magnet 30 is the innermost (outer in the radial direction) than the magnetic flux density of the outermost (outer in the radial direction) portion of the permanent magnet 30 including at least two side surfaces facing in the rotation direction. The magnetic flux density ratio of the portion is 0.7 or more.

In this embodiment, first, the periphery of the permanent magnet 30 is coated with a magnetically conductive resin layer 31 made of resin and a magnetically conductive material. After that, the magnetically conductive resin layer 31 is cured. The magnetically conductive resin layers 31 are formed on both surfaces of the permanent magnet 30 at least in the circumferential direction (rotational direction).

Next, the permanent magnet 30 is magnetized.

After that, as shown in FIG. 4, the permanent magnet 30 covered with the magnetically conductive resin layer 31 is inserted into the magnet placement hole 21 . At this time, the magnetism-permeable resin layer 31 is press-fitted so as to be in contact with the

inner surfaces

21 a and 21 b of the magnet arrangement hole 21 . Since the magnetism-permeable resin layer 31 contains resin, it is possible to prevent the

inner surfaces

21a and 21b from being damaged.

With the configuration as described above, the permanent magnets 30 inserted into the magnet placement holes 21 are securely fixed in the magnet placement holes 21 by the magnetically conductive resin layer 31 .

That is, since each magnet arrangement hole 21 is filled with the permanent magnet 30 and the magnetism-permeable resin layer 31 in the rotation direction, each permanent magnet 30 can be prevented from moving from the arrangement position in the circumferential direction.

Therefore, in each magnet placement hole 21, variations in the attraction points of the permanent magnets 30 can be suppressed. As a result, it is possible to reduce variations in the amount of magnetic flux density for each permanent magnet 30, and to prevent an increase in cogging torque.

Here, when the thermoplastic magnetically conductive resin is brought into contact with the magnetized permanent magnet, the permanent magnet is demagnetized by the heat generated when the resin hardens.

In the present embodiment, since the magnetically conductive resin layer 31 is coated and cured on the permanent magnet 30 before magnetization, thermal demagnetization can be avoided.

(first modification)
FIG. 5A shows a plan view of the vicinity of the magnet placement hole 21 in the electric motor 1 according to the first modification of the embodiment of the present disclosure. The configuration of the electric motor 1 is the same as that of the electric motor 1 shown in FIG. In the first modification, the permanent magnet 30 is in contact with only one surface of the magnet arrangement hole 21 in the radial direction, and three side surfaces of the permanent magnet 30 including the surface facing the inner surface 21 a and the inner surface 21 b are covered with the magnetically conductive resin layer 31 . shows the configured configuration. Also with this configuration, the permanent magnets 30 inserted into the respective magnet arrangement holes 21 are reliably fixed in the magnet arrangement holes 21 by the magnetically conductive resin layer 31 .

(Second modification)
FIG. 5B shows a plan view of the vicinity of the magnet placement hole 21 in the electric motor 1 according to the second modification of the embodiment of the present disclosure. The configuration of the electric motor 1 is the same as that of the electric motor 1 shown in FIG. A second modification shows a configuration in which the permanent magnet 30 is not in contact with the magnet placement hole 21 and the four side surfaces of the permanent magnet 30 are covered with the magnetically conductive resin layer 31 . Also with this configuration, the permanent magnets 30 inserted into the respective magnet arrangement holes 21 are reliably fixed in the magnet arrangement holes 21 by the magnetically conductive resin layer 31 .

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.

(mode of implementation)
Embodiments of the present disclosure are described below.

A rotor (2) according to a first aspect of the present disclosure includes a rotor core (20) having a plurality of magnet placement holes (21), and a plurality of permanent magnets respectively arranged in the plurality of magnet placement holes (21). It comprises a magnet (30) and a rotating shaft (10) fixed to a rotor core (20). Each of the plurality of permanent magnets (30) is covered with a magnetically conductive resin (31) on at least two side surfaces facing in the direction of rotation. Each of the plurality of permanent magnets (30) is fixed to a corresponding one of the plurality of magnet placement holes (20) by a magnetically conductive resin layer (31).

A method for manufacturing a rotor (2) according to a second aspect of the present disclosure includes forming a magnetically conductive resin layer (31) on at least two side surfaces of a permanent magnet (30) facing the rotation direction of the rotor (2). After that, the permanent magnet (30) is magnetized, and then the permanent magnet (30) having the magnetically conductive resin layer (31) formed on the two sides is inserted into the magnet arrangement hole (21).

An electric motor (1) according to a third aspect of the present disclosure is arranged to face the rotor (2) of the first aspect and the rotor (2), and generates a magnetic force acting on the rotor (2). a stator (3) that allows

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 arrangement hole

21a, 21b inner surface 30 permanent magnet 31 magnetically conductive resin layer

Claims

a rotor core having a plurality of magnet placement holes;
a plurality of permanent magnets respectively arranged in the plurality of magnet arrangement holes;
and a rotating shaft fixed to the rotor core,
each of the plurality of permanent magnets is covered with a magnetically conductive resin on at least two side faces facing the direction of rotation;
each of the plurality of permanent magnets is fixed to a corresponding one of the plurality of magnet placement holes by the magnetically conductive resin layer;
rotor.
2. The method of manufacturing a rotor according to claim 1, wherein after the magnetically conductive resin layer is formed on at least the two side surfaces of the permanent magnets facing in the direction of rotation, the permanent magnets are magnetized; The permanent magnet having the magnetically conductive resin layer formed on the two side surfaces is inserted into the magnet arrangement hole,
A rotor manufacturing method.
2. A rotor according to claim 1, and a stator arranged to face the rotor and generating a magnetic force acting on the rotor.
Electric motor.