SPARK PLUG

摘要

A spark plug not using noble metal members for a center electrode and a ground electrode has improved ignitability. A spark plug has a center electrode, an insulator, a main body fitting, and a ground electrode having an electric discharge surface and forming a spark gap between the electric discharge surface and the tip of the center electrode.  Both the center electrode and the ground electrode are not provided with noble metal members, and the ground electrode is provided with a base joined to the main body fitting and located above the electric discharge surface and also with a tip connected to the base so as to be located below the base and having the electric discharge surface.  If a direction perpendicular to the axis direction and extending from the base toward the center electrode is a first direction, the width of the center electrode when viewed in the first direction is Da, and the width of the base when viewed in a first direction is Db, the spark plug satisfies the relationship of Db/Da = 0.92.