Patent ID: 8766521
Filing Date: 2014-07-01
Classification: F16J,H01T

Abstract:
1. A spark plug, comprising: a center electrode; an insulator having an axial hole, said insulator holding the center electrode within a front end side of the axial hole; a cylindrical metal shell that surrounds and holds the insulator in a circumferential direction, said cylindrical metal shell having: a ground electrode that forms a spark discharge gap between the ground electrode and the center electrode; and a seal member having an annular configuration formed by folding an annular plate in a thickness direction a plurality of times, and concentrically mounted on a region of the metal shell between the screw thread and the protrusion part from outside, in which in a state where the metal shell is threadably fitted into an internally threaded mounting hole, the seal member is compressed between the protrusion part and an opening periphery of the mounting hole, and seals a space between the protrusion part and the opening periphery, wherein surfaces of the seal member that face each other by folding are not in contact with each other, when the seal member is in an uncompressed state prior to threadably fitting the metal shell into the mounting hole, wherein during a process of threadably fitting the metal shell into the mounting hole, in a state where the seal member is uncompressed while being interposed between the protrusion part of the metal shell and the opening periphery of the mounting hole,