Patent ID: 7394342

Claim:
An ignition coil comprising: primary and secondary coils; a case that receives the primary and secondary coils; a central core that is made of a magnetic material and is positioned radially inward of the primary and secondary coils; a sheet that relieves a thermal stress and is wound around the central core, wherein: at least one of axial end portions of the sheet forms a folded end portion, which is folded against a corresponding axial end surface of the central core or an axially outer end surface of a connecting member connected to the corresponding axial end surface of the central core; the folded end portion includes a plurality of generally arcuate segments, which are folded one after another on one circumferential side thereof; a first circumferential end and a second circumferential end of each generally arcuate segment are folded in such a manner that the first circumferential end of the generally arcuate segment is folded over a second circumferential end of an adjacent one of the plurality of generally arcuate segments located on a first circumferential end side of the generally arcuate segment, and the second circumferential end of the generally arcuate segment is folded beneath a first circumferential end of another adjacent one of the plurality of generally arcuate segments located on a second circumferential end side of the generally arcuate segment; and thermoset resin that is filled in spaces in the case.