Patent ID: 8466608
Filing Date: 2013-06-18
Classification: H01T

Abstract:
1. A spark plug, comprising: a shaft-shaped center electrode; a ceramic insulator holding an outer circumference of the center electrode; a metal shell holding an outer circumference of the ceramic insulator; and a ground electrode joined to the metal shell so as to define a spark gap between the center electrode and the ground electrode, the ground electrode having an opposing surface facing a front end of the center electrode, a back surface located opposite from the front end of the center electrode, a protruding portion formed on the opposing surface by extrusion pressing and protruding from the opposing surface toward the front end of the center electrode and a press recessed portion made in the back surface due to the formation of the protruding portion by extrusion pressing and recessed from the back surface toward the front end of the center electrode, wherein a protrusion amount A of the protruding portion from the opposing surface satisfies a relationship of 0.4 mm≦A≦1.0 mm; and wherein a width B from a front end of the ground electrode to the press recessed portion satisfies a relationship of 0.4 mm≦B≦2.5 mm.