Spark plug

摘要

A spark plug includes an insulator; a center electrode; a metallic shell; a ground electrode disposed at a forward end portion of the metallic shell and forming a gap in cooperation with a forward end portion of the center electrode; and a tip at least a portion of which is joined to at least the one of two side surfaces of the ground electrode which is disposed downstream with respect to fuel gas flow. In a first imaginary plane which contains a forward end surface of the center electrode and on which a discharge surface of the tip is projected, at least a portion of a projected image of the discharge surface is located within a range of 2.5G from the outer circumference of the forward end surface of the center electrode, where G (mm) is the size of the gap.

主权项

1. A spark plug comprising:
a tubular insulator having an axial hole extending therethrough in the direction of an axial line; a center electrode inserted into a forward end portion of the axial hole; a tubular metallic shell provided on an outer circumference of the insulator; and a ground electrode disposed at a forward end portion of the metallic shell and adapted to form a gap in cooperation with a forward end portion of the center electrode; the spark plug being characterized by further comprising a tip at least a portion of which is joined to at least the one of two side surfaces of the ground electrode which is disposed downstream with respect to fuel gas flow, and characterized in that in an imaginary plane which contains a forward end surface of the center electrode and on which a discharge surface of the tip is projected along an axial line, at least a portion of a projected image of the discharge surface is located within a range of 2.5G from an outer circumference of the forward end surface of the center electrode, where G (mm) is a size of the gap.