Patent ID: 7329836
Filing Date: 2008-02-12
Classification: F23Q

Abstract:
1. A glow plug comprising: a tubular metallic shell including an axial hole extending through the metallic shell along an axis; a rod-shaped center shaft extending along the axis and disposed in the axial hole of the metallic shell with a clearance between the center shaft and a wall surface of the axial hole, one end portion of the center shaft projecting from a rear end surface of the metallic shell; an O-ring disposed at a rear end of the axial hole between the wall surface of the axial hole and the center shaft, the O-ring being in close contact with the wall surface of the axial hole and an outer circumferential surface of the center shaft; and an annular press member including an insertion hole into which the center shaft is inserted, the press member being at least partially disposed between the wall surface of the axial hole and the center shaft and including an end surface for pressing against the O-ring from the rear thereof; at least one of a portion of the wall surface of the axial hole with which the O-ring is close contact and a portion of the outer circumferential surface of the center shaft with which the O-ring is close contact comprising a tapered surface that increases the clearance between the wall surface of the axial hole and the center shaft toward the rear end side along the axis; and the O-ring being of an annular shape extending circumferentially around said axis, and a radial direction of the O-ring being defined as extending radially from said axis, said O-ring having a transverse cross section of a contour which satisfies a relation V>H wherein V represents a distance defined between two spaced tangential lines which are parallel to the radial direction of the O-ring and are tangent to said contour and H represents a distance between two spaced tangential lines which are perpendicular to said radial direction and are tangent to said contour.