To manufacture a closed magnetic circuit core of an ignition coil for an internal combustion engine by efficiently eliminating the useless part from a material plate of a silicon steel plate in blanking the core plate.
An integral core plate 11 consisting of a belt-like narrow width insertion part 12 having a 1/2 width of the inner peripheral width w of an inside coil bobbin 1' of a primary and a secondary coils 1, 2 concentrically fitted in, and a belt-like half-round surrounding part 13 connected to one end of the insertion part 12 at right angles is formed by blanking from the material plate 5. Two laminated bodies 14-1, 14-2 are formed by laminating the core plates 11 up to the thickness corresponding to the inner peripheral height of the coil bobbin 1', and both the belt-like narrow width insertion parts 12 of the laminated bodies 14-1, 14-2 are aligned in parallel and inserted into the inner peripheral part of the coil bobbin 1'. And then the belt-like half-round surrounding parts 13 positioned outside the coil bobbin 1' are bent horizontally as the belt-like states so that each laminated body surrounds the outside of each half-round of the primary and secondary coils 1, 2.
YAMADA KINSAKU
Shinichi Fukuda
Takemichi Fukuda