JPH0332892B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to the improvement of anisotropic ferrite magnets with an arcuate cross section, which are often used in motors, generators, etc.
The present invention relates to an anisotropic ferrite magnet having an arcuate cross section, in which the surface magnetic flux distribution characteristics in the circumferential direction of the inner and outer circumferential surfaces of an arc in a surface magnetic flux distribution diagram are shaped into a specific shape, and the magnetic properties of the inner circumferential surface of the arc are significantly improved.

Conventional technology In recent years, smaller size and higher performance have become essential for rotating electrical equipment such as motors and generators, and the anisotropic ferrite magnets with an arcuate cross section used in such equipment also have low total magnetic flux (φ) _T and magnetic flux density. (Bg), the magnetic properties were improved by flattening the surface magnetic flux distribution. That is, consideration was given to uniformly exhibiting high magnetic properties throughout the magnet by using molding apparatuses having various configurations as shown in Japanese Patent Publication No. 17118/1983.

Furthermore, today, there is a new desire to improve the magnetic properties of the inner circumferential arcuate surface, which is the surface facing the coil etc. in the anisotropic ferrite magnet having an arcuate cross section.

That is, the magnetic properties of the inner circumferential surface of a conventional anisotropic fluorite magnet with an arcuate cross section are, for example, the surface magnetic flux distribution state in the circumferential direction of the inner circumferential surface (the X direction in the arcuate cross section magnet of FIG. As shown in Figure A, the highest values are at both ends, and the area between the highest values is flat with a large drop. In addition, the magnetic flux distribution in the axial direction of the inner circumferential surface (the Y direction perpendicular to the X direction in Figure 2) has its highest value at both ends, as shown in Figure B in Figure 3, and the distance between the highest values is It has fallen significantly.

Furthermore, the difference in magnetic properties between the inner circumferential surface and the outer circumferential surface of a magnet is usually small, and a difference of a few percent may occur due to the effects of water removal during compression molding of the magnet. It cannot actively improve magnetic properties.

Problems to be Solved by the Invention The present invention aims to provide an anisotropic filtrite magnet with an arcuate cross section and magnetic properties suitable for downsizing and improving the performance of rotating electrical equipment, etc. The objective is to create an anisotropic ferrite magnet with an arcuate cross-section that significantly improves the magnetic properties of the inner circumferential surface by actively creating property differences.

Means for Solving the Problems This invention has an arcuate cross section and anisotropy in the radial direction of the circular arc surface,
In an anisotropic filtrate magnet whose inner circumferential surface is a ferromagnetic surface and whose outer circumferential surface is a weakly magnetic surface, the highest value of the surface magnetic flux distribution characteristic in the circumferential direction of the inner circumferential surface of the arc in the surface magnetic flux distribution diagram is the maximum value of the distribution. An anisotropic filtrite magnet having a characteristic of forming a convex shape at the center, and a surface magnetic flux distribution characteristic of the circumferential direction of the arcuate outer peripheral surface having a characteristic of forming a concave shape at the center of the distribution. .

Function Generally, the difference in magnetic properties between the inner and outer circumferential surfaces of conventionally known anisotropic fluorite magnets with an arcuate cross section is slight, and due to the effects of water removal during compression molding of the magnet, the difference is only a few percent. However, it did not actively improve the magnetic properties of the inner circumferential surface.

This invention was based on the discovery that the above-mentioned difference in magnetic properties can be actively utilized, and by using the conventionally known slurry magnet raw material, the magnetic field strength on the upper and lower surfaces of the compact is changed in the die. During compression molding, a non-magnetic filter made of stainless steel or the like with a bow-shaped cross section is placed between the upper punch and the magnet raw material.
By compressing and molding the non-magnetic material through a non-magnetic filter with a thick central part by making the center point of the arc on the outer circumferential surface eccentric and the center point of the circular arc on the inner circumferential surface eccentric, the magnetic field on the inner circumferential surface side is A cross-section arcuate anisotropic filtrite magnet whose properties are greatly improved compared to the outer circumferential surface is obtained.

The magnetic properties of the inner circumferential surface of the anisotropic fluorite magnet according to the present invention having the arcuate cross-section shown in FIG. 2 are as follows: As shown by the solid line a in Figure 1A, the magnetic flux distribution state has the highest value in the center, forming a large convex shape, and the surface magnetic flux distribution in the X direction of the outer peripheral surface is as follows. As shown by the broken line b in Figure 1A, the central part exhibits the characteristic of forming a concave shape, and the difference in magnetic properties between the inner circumferential surface and the outer circumferential surface is large, and the magnetic properties of the inner circumferential surface are significantly improved. I understand.

Furthermore, compared to the same distribution of conventional magnets in which the range between the maximum values at both ends is flat with a large drop, characteristics are obtained in which the maximum value is high and the average value is also high.

In addition, in the axial direction of the inner circumferential surface, that is,
The magnetic flux distribution in the Y direction perpendicular to the direction is shown in Figure 1B.
As shown by the solid line a in Figure B, almost flat characteristics were obtained including the maximum value, and the surface magnetic flux distribution in the Y direction on the outer circumferential surface showed the characteristics shown by the broken line b in Figure B. It can be seen that the magnetic properties of the surface are significantly improved. Furthermore, compared to the same distribution of conventional magnets in which the maximum value at both ends is greatly depressed, the maximum value is equal to or higher than that, and the average value is extremely high.

Example When compression molding a slurry magnet raw material in a die by changing the magnetic field strength on the upper and lower surfaces of the molded object, an arc-shaped cross section made of stainless steel is used between the upper punch and the magnet raw material to reduce the thickness of the non-magnetic material. The arc surface is magnetized in the radial direction by a wet molding method in which the center point of the arc on the outer circumferential surface and the center point of the arc on the inner circumferential surface are made eccentric, and a non-magnetic filter with a thick central portion is interposed and compression molded. A cross-section arcuate anisotropic fluorite magnet with an outer diameter of 65 mm, an inner diameter of 30 mm, and a height of 36 mm was prepared, and the surface magnetic flux distribution on the inner and outer circumferential surfaces was measured, and the magnetic flux distribution diagram shown in FIG. 1 was obtained.

In addition, when we manufactured a conventional magnet with the same dimensions and measured the surface magnetic flux distribution on the inner and outer circumferential surfaces and compared it with that of the present invention, we found that the magnetic flux at the center of the inner circumferential surface was
15% higher, and Φ _T of the inner peripheral surface also showed a 6% higher value.
Further, while the difference in magnetic flux between the central part of the inner circumferential surface and the central part of the outer circumferential surface is about 100 G in conventional magnets, the difference in magnetic flux between the central part of the inner circumferential surface and the central part of the outer circumferential surface is 300 G or more in the magnet of the present invention.

Effects of the Invention The present invention provides an anisotropic fluorite magnet having an arcuate cross-section and anisotropy in the radial direction of the arcuate surface. None, and by making the surface magnetic flux distribution in the circumferential direction of the arcuate outer circumferential surface have a characteristic of forming a concave shape at the center, the difference in magnetic properties between the inner circumferential surface and the outer circumferential surface becomes large, as is clear from the examples, and the inner circumferential surface The magnetic properties of the material are significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a surface magnetic flux distribution diagram of a fluorite magnet having an anisotropic arcuate cross section according to the present invention, in which A shows the case in the X direction and B shows the case in the Y direction. FIG. 2 is a perspective view of a cross-section arcuate magnet. FIG. 3 is a surface magnetic flux distribution diagram of the inner circumferential surface of a conventional anisotropic fluorite magnet having an arcuate cross section, where A shows the case in the X direction and FIG. 3 B shows the case in the Y direction.

Claims (1)

[Scope of Claims] 1. In an anisotropic ferrite magnet having an arcuate cross section and anisotropy in the radial direction of the arcuate surface, the inner peripheral surface of the arc is a ferromagnetic surface and the outer peripheral surface is a weakly magnetic surface, the surface magnetic flux In the distribution diagram, the highest value part of the surface magnetic flux distribution characteristic in the circumferential direction of the inner circumferential surface of the arc has the characteristic of forming a convex shape at the center of the distribution, and the surface magnetic flux distribution characteristic in the circumferential direction of the outer circumferential surface of the arc has the characteristic of forming a convex shape at the center of the distribution. An anisotropic ferrite magnet characterized by having a characteristic of forming a concave shape in the central part.