PURPOSE: To prevent the scattering of the value of inductance by inserting a corn-shaped core into the coil wound in a corn-shell shape to prevent the positional deviation of a coil to the core.

CONSTITUTION: A corn-shaped core 3 is inserted into a coil 4 wound in a corn- shell shape. The coil 4 is wound in a size where the coil fits into the shape of the core 3 so that the core 3 and the coil 4 fit each other. Therefore, the position of the coil 4 is secured by the core 3 without positional deviation of the coil 4 to the core 3, thereby preventing the scattering of the value of inductance.