| 摘要 |
PROBLEM TO BE SOLVED: To improve magnetic efficiency by making further thin the thickness of the cylindrical part of the inner dimensional side of a bobbin, and to prevent a bobbin from peeling from a yoke due to a thermal impact. SOLUTION: A bobbin 12 made of resin and yokes 14 and 15 are integrated by insert molding so that any clearance between the cylindrical part at the inner peripheral side of the bobbin 12 and the yokes 14 and 15 can be removed. Then, axial groove working or knurl working for forming axial grooves 14a and 15a is preliminarily operated to the outer periphery of the cylindrical part positioned at the inner peripheral side of the bobbin 12 of the yokes 14 and 15.
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