Patent ID: 8264132

Claim:
A plasma jet ignition plug comprising: an insulator having an axial bore extending therethrough in a direction of an axis; a center electrode inserted into the axial bore in such a manner that a front end thereof is located rearward of a front end of the insulator with respect to the direction of the axis; a metallic shell disposed externally of an outer circumference of the insulator; and a ground electrode fixed to a front end portion of the metallic shell; a cavity being defined by a wall surface of the axial bore and a front end surface of the center electrode; wherein the ground electrode comprises a rodlike body configured such that a proximal end portion thereof is fixed to the front end portion of the metallic shell, an intermediate portion thereof is bent, and a distal end portion thereof is disposed away from and frontward of the front end of the insulator with respect to the direction of the axis, and a protrusion protruding from a surface of the body, and as viewed on an imaginary plane which is orthogonal to the direction of the axis and onto which an opening of the cavity and the protrusion are projected, a projected image of the opening of the cavity and a projected image of the protrusion overlap at least partially.