Patent ID: 8350455
Filing Date: 2013-01-08
Classification: H01T

Abstract:
1. A spark plug, comprising: a center electrode; a ground electrode bent to define a spark gap between a front end of the center electrode and an inner surface of the ground electrode facing the center electrode, wherein the ground electrode has a protrusion and a hole formed by extrusion process on a front end portion thereof; wherein the protrusion protrudes by a protruding length A of 0.4 to 1 mm from the inner surface of the ground electrode toward the front end of the center electrode and includes a first straight portion formed in such a manner that a width of the protrusion in a cross section through a center axis of the protrusion is uniform along a center axis direction of the protrusion and that the first straight portion has a projected first straight portion area S wherein the hole has an opening formed at an outer surface of the ground electrode opposite the inner surface in such a manner that a contour of the first straight portion of the protrusion projected onto an imaginary plane perpendicular to the protruding direction of the protrusion is located inside of a contour of the opening projected on said imaginary plane and that a ratio (S