[Challenge] to enter the core one end of the coil bobbin to the pole hole of the case body surface, is brought into contact with the flange portion of the coil bobbin in case the body surface, and "strut combination of the case body by the magnetic generating means," "improvement of the magnetic efficiency" I will be both. The apparatus includes a magnetic action surface 2a is case body 2 provided, having a magnetic generator 3, which is built into the case body 2, a magnetic generating means 3, the spool section having a flange portion 4, 4 at both ends a coil bobbin 6 wire wound around the circumferential surface 5, with a core 7 which is fitted in the spool part 5 in a state where one end portion 7a is projected from the flange portion 4 of one of the coil bobbin 6, and projection of the core 7 one is allowed to enter the section 7a to the pole hole 8 formed on the inner surface of the magnetic working surface 2a of the case body 2, and to abut against one of the flange portion 4 on the inner surface of the magnetic working surface 2a of the case body 2, The dent to the inner surface of the magnetic working surface 2a, and to regulate the magnetic generating means 3, to form a protruding end portion 7a of the core 7 in a tapered shape, the magnetic working surface 2a of the inner surface of the pole hole 8 opening flared I have formed. [Selection Figure] Figure 1【課題】コイルボビンの鉄心一端をケース体内面の磁極孔に進入させ、コイルボビンの鍔部をケース体内面に当接させて、「磁気発生手段によるケース体の支柱兼用」と「磁気効率の向上」を両立する。【解決手段】磁気作用面2aが設けられたケース体2と、ケース体2に内蔵された磁気発生手段3を有し、磁気発生手段3は、両端に鍔部4、4を設けたスプール部5の周面に電線が巻かれたコイルボビン6と、コイルボビン6の一方の鍔部4から一端部7aが突出した状態でスプール部5内に嵌入される鉄心7を備え、鉄心7の突出した一端部7aをケース体2の磁気作用面2a側の内面に形成された磁極孔8に進入させ、且つ、一方の鍔部4をケース体2の磁気作用面2a側の内面に当接させて、磁気作用面2aの内面側への凹みを、磁気発生手段3で規制し、鉄心7の突出した一端部7aを先細り状に形成し、磁気作用面2a側の内面の磁極孔8を開口末広がり状に形成している。【選択図】図1
