Patent ID: 7441552

Claim:
An ignition coil apparatus for an internal combustion engine comprising: a transformer having a primary winding, a secondary winding and an iron core; a case main body with said transformer received therein; a high voltage tower that is formed integrally with said casing main body, and holds therein a high voltage output terminal for outputting a high voltage generated upon interruption of an excitation current flowing through said primary winding to the outside; and a cylindrical plug boot that has one end attached to said high voltage tower; wherein said plug boot is mounted on an internal combustion engine main body through a head cover having upstanding wall portions by being inserted into a plug hole formed in said internal combustion engine main body; and a pair of protrusions for restricting the rotation of said casing main body around an axis of said plug hole are formed on a surface of said casing main body in opposition to said wall portions.