JPS6118115A - Magnetic substrate having heat stress absorbing section - Google Patents

Abstract

PURPOSE:To provide magnetic member which does not result in cracks when sintering it even at a magnetic orientation rate of 100%, by forming air gaps on a circumference being approximately middle between the inner and outer circumferences of a cylinder, going through the cylinder in the longitudinal direction. CONSTITUTION:When ferrite magnetic powder is compressed and molded in magnetic field, one or more of air gaps pi or R are formed on an approximate middle position of magnetic member thickness in the direction applying the magnetic field, and in a plane rectangular to the magnetic field applying direction. Thus, distortion which may result from the sintering of the molding can be absorbed in the air gaps so as to reduce cracks.

Description

DETAILED DESCRIPTION OF THE INVENTION The longer the cylinder length and the thinner the wall thickness of the cylindrical ferrite magnetic material, the more difficult it becomes to mold and the larger the molding distortion. If this molded body is already distorted in its green state, problems such as cracking or bending will occur during sintering.

Furthermore, uneven distribution of powder due to non-uniform distribution of the magnetic field also causes distortion in the compact. The state of strain after sintering is shown in the opening of Figure 1. However, even if these phenomena are solved, the second problem will still be encountered. That is, when a cylinder is molded by applying a magnetic field radially from the center line of its circumference, sintering causes the inner and outer surface layers to undergo strong tensile strain characteristic of anisotropic magnetic materials.

This strain is particularly large at the outer periphery, and is 100% of the magnetic orientation degree.
% cracks during cooling following sintering. 1st
This is shown in Figure O. If the magnet is isotropic, it will hardly break even if it is rapidly cooled.

From this, it is easy to understand that if the degree of orientation is adjusted, there is an appropriate degree of orientation in which cracks do not occur.

Its value is generally a degree of orientation of 70-80%.

The inventor of the present invention does not break the orientation at all even if the degree of orientation is 100%! I
ll! As shown in Figure 2, the construction method is to create a gap on the circumference approximately halfway between the inner circumference and the outer circumference of the cylinder (in a plane perpendicular to the direction of the magnetic field, or a trace thereof, or a gap between the two). A method was devised to provide the state by partially penetrating the cylinder in the length direction.

This air gap may be of the π type, which is perpendicular to the magnetic field, or the R type, which is parallel to the magnetic field, as shown in FIG.

However, in general, when the π method is used as a magnet, the characteristics deteriorate slightly, so the R method is preferable. In addition, these anisotropic magnetic materials are less prone to cracking by providing air gaps in both the upper and lower portions of the cylindrical shape. This is the case when the strain is absorbed at the ends of the plate. However, if the shape is large and thick, cracks are likely to occur. In such a case, an air gap is provided parallel to the applied magnetic field as shown in 8 in FIG. Another good method is to fill the molded body with a substance that easily evaporates at low temperatures as shown in the figure. As the embedding material, strips or thin pieces of plastic, paper, wood, bamboo, etc. may be embedded. Another feature is that this embedded material evaporates or burns away as the temperature rises, creating virtually no voids.

When the molded products shown above are fired, the surface of the molded product contracts as sintering progresses, and the strain generated during shrinkage presses both walls of the cavity, resulting in a trace state as sintering progresses. Sintering progresses until

Further, if the scratches in the trace state are parallel to the magnetic field, the deterioration of the magnetic properties is slight and there is no problem at all in practice.

As mentioned above, the reason why the void part sinters to a trace state is due to the unique fact that the magnetic material shrinks by 23% in the direction of magnetization (thickness direction), while in the direction perpendicular to it, it shrinks by 11-13%. This is due to a phenomenon. Therefore, the difference is approximately 1
It is preferable to disperse voids equivalent to 0% in the middle part of the thickness of the magnetic material and throughout the magnetic material.

By employing the present invention, even in the case of 100% defective products with 100% orientation, it is easy to convert all the products into non-defective products.

[Brief explanation of the drawing]

The structure is shown as R type. 5b is +4. USp is on the side of the same figure. This shows the case where it is provided in some parts. FIG. 3 shows a case in which a void portion is attached to a flat plate-shaped molded body. Ne: S-1st

Claims (1)

[Claims] 1) In compression molding ferrite magnetic powder in a magnetic field,
A gap is formed at one or more locations at a position approximately in the middle of the thickness of the magnetic body in the direction of application of the magnetic field, and in a plane perpendicular to the direction of application of the magnetic field. An anisotropic magnetic material that reduces cracks and cracks by absorbing the strain caused by the voids. 2) When compression molding ferrite magnetic powder in a magnetic field,
A gap is formed at one or more locations at a position approximately in the middle of the thickness of the magnetic body in the direction of application of the magnetic field, and in a plane perpendicular to the direction of application of the magnetic field. A method for producing an anisotropic magnetic material in which the strain absorbed by the void is absorbed to reduce cracks and cracks. 3) A cylindrical magnetic body that satisfies the conditions set forth in claim 1. 4) A flux-strengthened magnetic material according to claim 1, in which a flux is added to the gap portion so that an excess amount of the flux can be melted out during sintering and shrinkage of the magnetic material. 5) The magnetic material according to claim 1, in which a portion corresponding to the void portion according to claim 1 is filled with a substance that disappears upon heating.