CN111566902A

CN111566902A - Axial gap type rotating electric machine

Info

Publication number: CN111566902A
Application number: CN201880084944.8A
Authority: CN
Inventors: 佐藤大祐; 床井博洋; 榎本裕治; 相马宪一
Original assignee: Hitachi Industrial Equipment Systems Co Ltd
Current assignee: Hitachi Industrial Equipment Systems Co Ltd
Priority date: 2018-03-08
Filing date: 2018-11-28
Publication date: 2020-08-21
Also published as: JP2019161723A; WO2019171673A1

Abstract

The axial gap type rotating electrical machine of the present invention includes: a yoke having a plurality of magnets arranged in a circumferential direction and a magnetic path between the magnets; and a stator disposed opposite to the rotor with a gap therebetween in a rotation axis direction, wherein the yoke includes a first yoke and a second yoke having a lower electric conductivity than the first yoke, and a surface of the magnet is disposed in contact with a surface of the first yoke on the stator side and in contact with a surface of the second yoke on the stator side.

Description

Axial gap type rotating electric machine

Technical Field

The present invention relates to a rotating electrical machine, and more particularly to an axial gap type rotating electrical machine.

Background

An axial gap type rotating electrical machine is configured such that a disk-shaped rotor and a cylindrical stator face each other in a rotation axis direction. Since the clearance surface for generating torque increases approximately in proportion to the square of the diameter, it is effective particularly for reducing the size and increasing the efficiency of a thin rotating electric machine. In addition, in a double rotor type axial gap rotary electric machine in which a stator is sandwiched by 2 rotors, the stator core can be formed in a simple columnar shape.

Patent document 1 discloses an axial gap type rotating electrical machine in which attachment of a rotor and replacement of a permanent magnet are facilitated. In the above, a configuration is disclosed in which a recess is formed in the rotor, a back yoke is disposed in the recess, and a magnet is disposed on the surface of the back yoke.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2012-152020

Disclosure of Invention

Problems to be solved by the invention

In a double-rotor type axial gap rotary electric machine and an axial gap rotary electric machine in which 1 rotor faces 1 stator, a magnetic path is formed by arranging a yoke on the back surface of a magnet of the rotor. The magnetic flux in the yoke is mainly composed of a direct current component generated by the magnet, but an alternating current component is also generated due to the interaction with the stator core. The ac component causes eddy current to occur on the yoke surface, resulting in a decrease in output and an increase in loss, i.e., a decrease in efficiency. In particular, in the simple stator core as described above, since the magnetic resistance of the stator is distributed largely as viewed in the circumferential direction, the ac component in the yoke increases, and the efficiency is remarkably lowered.

In the structure described in patent document 1, in order to reduce the eddy current on the yoke surface, it is conceivable to dispose a material having low conductivity as the back yoke disposed in the recess. However, in this case, the following problems exist.

When the yoke fastened to the rotating shaft is a low-conductivity yoke, the magnets are laminated in the rotating shaft direction, and therefore, the distance between the magnets and the stator core, that is, the gap length tends to vary due to the unevenness of the thickness dimension of the low-conductivity yoke, the unevenness of the surface, and the gaps between the members caused by the adhesive or the like. The variation in the gap length is a cause of variation in motor characteristics and collision of the magnet with the stator.

There are actually used low-conductivity yoke members, such as those obtained by laminating electromagnetic steel sheets in the circumferential direction or the radial direction, those obtained by compression-molding iron powder coated with an insulating coating, and those obtained by compression-molding and sintering magnetic SUS powder having low conductivity. The precision can be improved by additionally processing the surface of the molded product, but this increases the cost.

On the other hand, in order to improve the dimensional accuracy in the direction of the rotation axis, the height of the yoke recess portion having high conductivity can be made larger than the thickness of the yoke having low conductivity, and the magnet can be configured to contact the yoke. However, in this case, a gap is formed between the magnet and the low-conductivity yoke, and the magnetic resistance increases, thereby reducing the motor output and the motor efficiency.

The invention aims to provide an axial gap type rotating electric machine which reduces eddy current on the surface of a yoke, has small characteristic unevenness and has high efficiency.

Means for solving the problems

A preferred example of the present invention is an axial gap type rotating electrical machine including: a rotor having a plurality of magnets arranged in a circumferential direction and a yoke constituting a magnetic path between the magnets; and a stator disposed to face the rotor with a gap therebetween in a rotation axis direction, wherein the yoke includes a first yoke and a second yoke having a lower electric conductivity than the first yoke, and a surface of the magnet is disposed to be in contact with a surface of the first yoke on the stator side and in contact with a surface of the second yoke on the stator side.

Effects of the invention

According to the present invention, an axial gap type rotating electrical machine having a small variation in characteristics and high efficiency can be obtained while reducing eddy currents on the yoke surface.

Drawings

Fig. 1 is a structural diagram of a rotating shaft direction of a rotating electric machine in embodiment 1.

Fig. 2 is a view showing a radial structure of a rotor of a rotating electric machine according to embodiment 1.

Fig. 3 is a structural diagram of the rotating shaft direction of the rotating electric machine in embodiment 2.

Fig. 4 is a view showing a radial structure of a rotor of a rotating electric machine according to embodiment 2.

Fig. 5 is a view showing a radial direction of a rotor of a rotating electric machine in example 3 and explaining a positional relationship between a magnet and a yoke.

Fig. 6 is a view showing a radial structure of a rotor of a rotating electric machine according to embodiment 4.

Fig. 7 is a view showing a radial structure of a rotor of a rotating electric machine according to embodiment 5.

Detailed Description

Hereinafter, embodiments of an axial gap type rotating electrical machine will be described with reference to the drawings.

Example 1

Fig. 1 is a structural diagram of a rotating shaft direction 40 of a rotating electric machine 1 in embodiment 1. The rotating electrical machine 1 is a double-rotor single-stator axial gap type rotating electrical machine including a

stator

2 and 1 pair of rotors 3 arranged with a gap of a predetermined gap length in the rotating axis direction 40 from the stator 2.

The stator 2 is configured by arranging a plurality of stator windings 21 around the outer circumference of the stator core 22 in the circumferential direction, and is fixed to the housing 4 by being filled with an insulating resin. The stator core 22 is formed of, for example, a laminate of magnetic thin plates such as electromagnetic steel plates and amorphous foil tapes, or a powder magnetic core obtained by compression molding iron powder coated with an insulating coating, in order to suppress the generation of eddy current.

The rotor 3 is composed of a yoke a31 coupled to the rotating shaft 5, a yoke b32 made of a material different from that of the yoke a31, and a magnet 33. The magnet 33 is formed in a ring shape, and is magnetized in the rotation axis direction 40 so that the poles adjacent in the circumferential direction are in opposite directions. The surface of magnet 33 facing stator 2 of yoke a31, i.e., the surface on the stator 2 side, is held in contact with it.

The yoke b32 is disposed in a through hole formed in the rotation axis direction 40 of the yoke a31, and the surface of the yoke b32 on the stator 2 side is disposed in contact with the back surface of the magnet 33. After magnet 33 is held in contact with the stator 2 side surface of yoke a31, when yoke b32 is inserted through the through hole until magnet 33 comes into contact, magnet 33 can be reliably brought into contact with yoke b 32. The surface of the yoke b32 opposite to the back surface side of the magnet 33 in the rotation axis direction 40 is not in contact with the yoke a31 or the like. That is, an open structure having a space. Thus, unevenness in the thickness dimension of the yoke b32 and unevenness in the surface occur on the open side without affecting the unevenness in the gap length. The adjacent magnetic poles of the magnet 33 face in opposite directions, and the yoke a31 and the yoke b32 form a magnetic path between the adjacent magnetic poles. The housing 4 is provided with a through hole through which the rotary shaft 5 passes, and the through hole is provided with a bearing 6. The rotary shaft 5 is rotatably held by a bearing 6.

Fig. 2 is a view showing a radial structure of the rotor 3 of the rotating electric machine 1 according to embodiment 1. The radial direction is a direction of the diameter of the circular rotor 3 as one cross section of fig. 2. The yoke a31 has a structure in which a plurality of through holes are formed in the circumferential direction 41, side surfaces of the through holes are arranged to face the side surfaces of the yoke b32, and the yoke b32 is held by bonding the side surfaces to each other. The material of the yoke b32 is made of, for example, an electromagnetic steel plate, a dust core, electromagnetic SUS, or the like, which has a smaller electrical conductivity than the yoke a 31. On the other hand, the yoke a31 is made of a structural material having magnetic properties and higher electrical conductivity than the yoke b32, such as a mechanical structural carbon steel such as S45C or a general structural rolled steel such as SS 400. Further, the dimensional accuracy of the yoke a31 in the rotation axis direction is higher than that of the yoke b 32.

With the above configuration, the resistance of the rotor 3 formed of the yoke b32 made of a low-conductivity material is increased, and an eddy current generated in the rotor 3 can be suppressed. Further, the magnet 33 and the yoke a31 are bonded via an adhesive layer of an adhesive. Therefore, the gap length is not affected by the variation in the thickness dimension of the yoke b 32. Since the yoke b32 is held in contact with the magnet 33 with reliability, the magnetic resistance is not increased by the gap. Thus, high efficiency and reduced characteristic unevenness can be achieved.

Example 2

Fig. 3 is a structural diagram showing a rotating shaft direction 40 of the rotating electric machine 1 in embodiment 2. Fig. 4 is a view showing a radial structure of the rotor 3 of the rotating electric machine 1. The insulating layer 34, for example, resin, ceramic, or metal oxide is formed on the side surface of the yoke a31 or the yoke b 32.

The insulating layer 34 electrically insulates the yoke a31 and the yoke b32 from each other. The resistance of the rotor 3 increases because the path through which the eddy current flows is a narrow region. This can suppress an eddy current generated in the rotor 3.

Example 3

Fig. 5 is a diagram showing a radial direction of the rotor 3 of the rotating electric machine 1 in example 3 and illustrating positional relationships among the magnet 33, the yoke a31, and the yoke b 32. The magnetic poles 33a of the magnets 33 are arranged in the circumferential direction 41. The magnetic flux passing through the yoke is directed in the magnetic flux direction 33 b. When the boundary lines between the adjacent magnetic poles 33a are projected in the rotation axis direction, the yoke b32 is disposed so as to overlap the boundary lines between the adjacent magnetic poles 33 a.

The magnetic resistance between the side surfaces of the yoke a31 and the yoke b32 is higher than that of the yoke a31 and the yoke b32 due to the gap between the side surfaces. In example 3, the opposing side surfaces of the yoke a31 and the yoke b32 were arranged between the equilateral boundaries in the vicinity of the center of the plurality of boundaries, so as to be away from the magnetic path between the adjacent magnetic poles 33a having a high magnetic flux density. This prevents a magnetic flux from decreasing between the side surfaces of the yoke a31 and the yoke b32, and thus suppresses a decrease in output torque.

Example 4

Fig. 6 is a diagram showing a radial structure of the rotor 3 of the rotating electric machine 1 according to embodiment 4. The through hole formed in the yoke a31 and the yoke b32 are circular in shape in the radial direction of the rotor 3.

The through hole of the yoke a31 can be formed by a general cutting process. This can reduce the manufacturing cost of the yoke a 31. In the compression molding of the yoke b32, since a mold can be manufactured by a general cutting process and the yoke b32 can be uniformly pressed, the manufacturing cost of the yoke b32 can be reduced.

Example 5

Fig. 7 is a diagram showing a radial structure of the rotor 3 of the rotating electric machine 1 according to embodiment 5. Fig. 7 (b) shows a rotor 3 of a type in which the rotating electric machine 1 has a larger diameter than that of fig. 7 (a). The yoke b32 has a size that can be set to 2 or more in the radial direction of the rotor 3.

By changing the number of the yokes b32 arranged on the rotor 3, the yokes b32 can be applied to rotors 3 having different diameters. This reduces the number of types of yokes b32, and reduces manufacturing cost.

In the above embodiment, the description has been given using the example of the double-rotor single-stator axial gap type rotating electrical machine, but the present invention can also be applied to other axial gap type rotating electrical machines such as the single-rotor single-stator type.

Description of the reference numerals

1 … rotating electrical machine, 2 … stator, 3 … rotor, 5 … rotating shaft, 6 … bearing, 21 … stator winding, 22 … stator iron core, 31 … magnetic yoke a, 32 … magnetic yoke b, 33 … magnet and 34 … insulating layer.

Claims

1. An axial gap type rotating electrical machine, comprising:

a rotor having a plurality of magnets arranged in a circumferential direction and a yoke constituting a magnetic path between the magnets; and

a stator disposed opposite to the rotor with a gap in a rotation axis direction,

the yoke includes a first yoke and a second yoke having a lower electrical conductivity than the first yoke,

the surface of the magnet is disposed in contact with the stator-side surface of the first yoke and in contact with the stator-side surface of the second yoke.

2. The axial gap type rotating electric machine according to claim 1, characterized in that:

an insulating layer is disposed on a surface of the first yoke facing the second yoke.

3. The axial gap type rotating electric machine according to claim 1, characterized in that:

the boundary between adjacent magnetic poles of the magnet is disposed on the stator side of the second yoke.

4. The axial gap type rotating electric machine according to claim 1, characterized in that:

the second yoke having a circular shape is arranged in the circumferential direction of the rotor.

5. The axial gap type rotating electric machine according to claim 1, characterized in that:

a plurality of the second yokes are arranged in a radial direction of the rotor.

6. The axial gap type rotating electric machine according to claim 1, characterized in that:

the second yoke has an open surface on the side opposite to the stator side.

7. The axial gap type rotating electric machine according to claim 6, characterized in that:

the second yoke is disposed in a through hole provided in the rotor.

8. The axial gap type rotating electric machine according to claim 3, characterized in that:

the surface of the first yoke facing the second yoke is disposed between the boundaries.

9. The axial gap type rotating electric machine according to claim 1, characterized in that:

an adhesive layer is provided between the first yoke and the magnet, and the first yoke is coupled to the rotating shaft.