Magnetostructure material, and process for producing the same

Details Magnetostructure material, and process for producing the same Magnetostructure material, and process for producing the same

1998-03-06

2000-11-21

Sheehan, John

Metal treatment

Stock

Magnetic

148101, 148122, H01F 1053

Patent

active

061497363

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1.Field of the Invention
The present invention relates to a magnetostrictive material, and particularly, to a magnetostrictive material including a rare earth element and a transition metal element, and a process for producing the same.
2.Description of the Related Art
This type of magnetostrictive material is conventionally known as disclosed in, for example, Japanese Patent Application Laid-open No.1-246342.
However, the known magnetostrictive material suffers from a problem that when a magnetic field is applied thereto, this material is deformed, with its volume remaining substantially constant, in a direction of the magnetic field due to the fact that the density is set at approximately 100% with respect to a theoretical density in order to make its mechanical strength high, and hence, the magnetostriction amount is relatively small.
The magnetostrictive material is used for forming a fuel injection valve in an engine for an automobile, as disclosed in, for example, Japanese Utility Model Application Laid-open No.3-35260 and Japanese Patent Application Laid-open No.6-58445. The mechanical strength required for the fuel injection valve or he like may be relatively low and hence, it is required that the magnetostrictive material used for the fuel injection valve or the like have only a practical mechanical strength and moreover, have a larger magnetostriction amount.
Accordingly, it is an object of the present invention to provide a magnetostrictive material which has a practical mechanical strength and also has a substantially increased magnetostriction amount.


SUMMARY OF THE INVENTION

To achieve the above object, according to the present invention, there is provided a magnetostrictive material including a rare earth element and a transition metal element, wherein the magnetostrictive material has a plurality of spherical voids dispersed in an entire volume thereof, a void content Vc being in a range of 10%.ltoreq.Vc.ltoreq.40%. The spherical voids may include a plurality of voids connected together into an elongated configuration.
If the magnetostrictive material is formed into a porous configuration, so that it has a void content Vc falling in the above range, the deforming ability of the magnetostrictive material is increased as compared with that of a high-density magnetostrictive material. Thus, it is possible to increase the magnetostriction amount of the magnetostrictive material.
When the magnetostrictive material is used, for example, as a material for forming a fuel injection valve of an engine in an automobile, the practical mechanical strength required for the magnetostrictive material can be satisfied by setting the void content Vc in the above-described range.
However, if the void content Vc<5%, the strength is increased, but the magnetostriction amount is decreased. On the other hand, if the void content Vc>40%, both the strength and the magnetostriction amount are decreased. In such range of the void content Vc, the magnetostrictive material having the spherical voids has a higher strength and a larger magnetostriction amount than those of a magnetostrictive material having flake-like voids.
It is another object of the present invention to provide a producing process of the above-described type, which is capable of easily producing a porous magnetostrictive material of the above-described type.
To achieve the above object, according to the present invention, there is provided a process for producing a magnetostrictive material, comprising the steps of producing by casting a blank including a transition metal element and an excessive amount of Sm larger than a final amount of Sm, and subjecting the blank to a thermal treatment in which an extra amount of Sm is removed to form a plurality of spherical voids.
With this process, it is possible to easily produce a porous magnetostrictive material of the above-described type.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an Sm--Fe based binary equilibrium state diagram;
FIGS. 2(a), 2(b), 2(c) and 2(d) are

REFERENCES:
patent: 4075042 (1978-02-01), Das
patent: 5201962 (1993-04-01), Yamashita et al.
patent: 5834663 (1998-11-01), Fukuno et al.
patent: 5888417 (1999-03-01), Akioka et al.
Chemical Abstracts, vol. 88, No. 24, Jun. 12, 1978, "Liquid Phase Sintering Of Rare Earth-Iron . . . Magnetostrictive Materials" No. XP002109147.
Chemical Abstracts, vol. 88, No. 18, May 1, 1978 "Microstructure and Magnetoacoustic Oscillations in Cobalt-Doped Copper, Nickel Ferrite", XP002109148.
Database WPI, Section PQ, Week 9438, Derwent Publications, Ltd., XP002109149 May 15, 1993.
Database WPI, Section Ch, Week 8216, Derwent Publications, Ltd., XP002109150 Jun. 23, 1981.
European Search Report Applications No. EP 96 94 1178 Jul. 14, 1999.

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