Patent ID: 9077157
Filing Date: 2015-07-07
Classification: H01T

Abstract:
1. An ignition plug comprising: an insulator having an axial bore extending in a direction of an axis; a metallic shell disposed externally of an outer circumference of the insulator; a terminal electrode having a leg portion inserted into a rear side of the axial bore, and a head portion formed on a rear side of the leg portion and having an outside diameter greater than that of the leg portion; and a rear trunk portion that is exposed from a rear end of the metallic shell and is provided in the insulator, said rear trunk portion having a maximum outside diameter of 9.5 mm or less, wherein the insulator has an end-surface seat portion located forward of a rear end of the insulator with respect to the direction of the axis and being in contact with a forward end surface of the head portion, and an outer circumferential portion into which at least a forward end portion of the head portion is inserted and which is located externally of an outer circumference of the head portion, wherein the insulator has a leg-portion insertion portion into which the leg portion is inserted and has a curved portion convexly curved toward the axis and formed between the leg-portion insertion portion and the end of the end-surface seat portion, and the end-surface seat portion is flat and extends along a direction orthogonal to the axis.