Patent ID: 7626481

Claim:
An ignition coil comprising: a coil body that includes a center core made of a soft magnetic material, a primary coil and a secondary coil, which are located in a coil case, the coil body being transversely arranged outside a plug hole of an engine; and a plug connection portion protruding in a direction perpendicular to an axial direction of the coil body and adapted to bring a high-voltage side winding end of the secondary coil into conduction with a spark plug, the plug connection portion being inserted into and arranged in the plug hole, wherein the primary coil is arranged on an inner peripheral side of the secondary coil, and the center core is arranged on an inner peripheral side of the primary coil, in the coil body, wherein the plug connection portion is provided to protrude substantially from an intermediate position in the axial direction of the coil body, wherein the secondary coil has a maximum outer diameter portion with a maximum winding diameter arranged in the intermediate position in the axial direction, and an inclined outer diameter portion arranged on two sides of the maximum outer diameter portion in the axial direction, the inclined outer diameter portion having a winding diameter decreasing toward two ends in the axial direction of the coil body, wherein the secondary coil includes a secondary electric wire with an insulating film, wound around an outer periphery of a secondary spool, and is provided in an obliquely wound state where reduced winding parts and enlarged winding parts are alternately superimposed on each other, and wherein the reduced winding part including the secondary electric wire is wound with a winding diameter decreasing obliquely from one side to the other side of the secondary spool in the axial direction, and the enlarged winding part including the secondary electric wire is wound with a winding diameter increasing obliquely from the other side to the one side of the secondary spool in the axial direction.