PURPOSE: To manufacture a high performance rotary transformer with high dimensional accuracy through reduced number of machining process by forming a resin layer of thickness less than 1mm on the peripheral face of a cylindrical ferrite core opposing to the peripheral face onto which a winding is applied and on at least one axial end face thereof.
CONSTITUTION: Material ferrite powder is compression molded to produce a cylindrical core which is then baked and a resin layer 5 is integrally formed, through injection molding, on one axial end face and one peripheral face of cylindrical cores 1, 2. The resin layer 5 is formed thinner than 1mm with remarkably high dimensional accuracy. Axial end face and peripheral face, on which the resin layer 5 is not formed, are then polished with the surface of the resin layer 5 as a reference while furthermore coil grooves 3, 4 are made through grinding thus producing a core for a coaxial rotary transformer. Dimensional accuracy of thus injection molded resin layer is such that the dimensional allowance is less than ±0.003mm and the geometric allowance of circularity, flatness and cylindricity is less than 0.003mm.
TANAKA KATSUNORI
IKEMOTO OSAMU
MURAKAMI TOYOHIKO
