Ngk Spark Plug Company, Limited

Takuya Kawade

Yuichi Yamada

Naofumi Yamamura

A spark plug includes an insulator, a metal shell surrounding the insulator, a center electrode disposed in the insulator, with a front end thereof exposed outside from the insulator, a ground electrode having a fixed end portion fixed to the metal shell and a free end portion located at a predetermined gap apart from the center electrode, and a coating part formed of noble metal or noble metal alloy so as to cover at least a region of an inner surface of the ground electrode from a first intersection to a second intersection, where the first intersection is an intersection at which an imaginary line extending from an outer circumference of the center electrode intersects the ground electrode; and the second intersection is an intersection at which an imaginary plane extending through a midpoint of the predetermined gap in parallel with the front end intersects the ground electrode.

Spark plug

An ignition plug having a ground electrode that includes a base material layer and an erosion-resistant layer having a thermal conductivity of 40 w/m&#xb7;K or more. The erosion-resistant layer extends at least from the center-electrode-facing portion to a location closer to the fixed end than a front end of the center electrode and 0.2 mm&#x2266;thickness tof the erosion-resistant layer&#x2266;thickness T of the ground electrode&#x2212;0.6 mm is satisfied.

Growing community of inventors

Hashima, Japan

Takuya Kawade