Patent ID: 8653724
Filing Date: 2014-02-18
Classification: H01T

Abstract:
1. A spark plug for an internal combustion engine comprising: a rodlike center electrode extending in a direction of an axis; a substantially cylindrical insulator provided externally of an outer circumference of the center electrode; a substantially cylindrical metallic shell provided externally of an outer circumference of the insulator; and a ground electrode extending from a front end portion of the metallic shell and forming a gap between a distal end portion thereof and a front end portion of the center electrode; wherein a protrusion projecting toward the center electrode and forming the gap in cooperation with the front end portion of the center electrode is formed at the distal end portion of the ground electrode from the same material as that used to form the ground electrode, at least the protrusion has an average crystal grain size of 20 μm to 200 μm inclusive, the ground electrode has a bent portion at substantially the middle thereof, and the protrusion is greater in average crystal grain size than the bent portion.