PURPOSE: To make small heat stress at joint part by jointing a magnet to a spacer made of magnetic substance with thermal coefficient of expansion which is close to that of a magnet and by fixing the spacer and housing at a cylindrical joint face each other.
CONSTITUTION: A disk-like protrusion 34 which protrudes toward the inside at the center of a flat bottom 32 within a housing 28 is formed. And the protrusion 34 is smaller than the diameter of a disk-like magnet 14 and is provided with a circular spacer 36. The circular plane of the spacer 36 is formed by the plane of the magnet 14 and an adhesive and both cylindrical parts, namely the inner wall of opening of the spacer 36 and outer wall of the protrusion 34 of the housing 28, are joined by such welding means as laser welding and the plane of the permanent magnet 14 and that of the protrusion 34 are not joined. Namely, the permanent magnet 14 is sealed to the housing 2 through the spacer 36. It will allow heat stress at the joint part to be ignored since the thermal coefficient of expansion of the permanent magnet 14 and that of the spacer 36 are close each other although the thermal coefficient of expansion of the permanent magnet 14 and that of the housing 28 differ greatly.
ITO HIROHITO
KAMASU MITSUAKI
KURAMOTO KENJI
| JPS477871A |