Spark plug for an internal combustion engine

摘要

A spark plug has a cylindrical metal shell, a ground electrode and an insulator fixedly supported within the metal shell with a front end of the insulator extended beyond a front end of the metal shell. The insulator has an axial bore in which a center electrode is placed to form a spark gap with the ground electrode. The front end of the metal shell is generally flush with or somewhat recessed into an inner wall of a combustion chamber of an internal combustion engine when the spark plug is mounted on a cylinder head of the engine. The front end of the insulator extends at least 4.0 mm from the front end of the metal shell.