Patent ID: 7145426

Claim:
An ignition coil for an internal combustion engine comprising: a cylinder-shaped first housing enclosing a center core, a primary coil disposed outside of the center core and a secondary coil disposed outside of the center core therein; a second housing having an install portion and a cylinder-shaped fitting portion fitted to an outer circumference of a top end portion of the first housing; a holder laid over top ends of the primary and secondary coils to define relative positions thereof; a ring-shaped insulating resin charged in an annular cavity defined at least by an uppermost portions of the primary and secondary coils, the top end portion of the first housing, the fitting portion of the second housing and the holder and in an intimate contact with the fitting portion, and a crack extension restrictor formed by a part of the fitting portion of the second housing and a part of the holder and disposed above the fitting faces of the fitting portion and the top end portion to restrict a crack extension starting at a top end of the top end portion and extending along the adhering faces of the fitting portion and the insulating resin toward the install portion.