Patent ID: 7477006
Filing Date: 2009-01-13
Classification: H01T

Abstract:
1. A spark plug for an internal combustion engine comprising: a cylindrical insulator having an axial hole penetrating in a direction of an axis; a center electrode insertedly provided in the axial hole; a cylindrical metal shell provided on an outer periphery of the insulator and having, on an outer periphery of the metal shell, an externally threaded portion for mounting; and a ground electrode provided on the metal shell such that a portion of the ground electrode opposes a leading end portion of the center electrode, in which a spark discharge gap is provided between the ground electrode and the leading end portion of the center electrode, an annular gasket receiving portion projecting radially outward being provided on a rear end side of the externally threaded portion of the metal shell, and a metallic gasket capable of abutting against the gasket receiving portion being provided on the outer periphery of the metal shell, wherein the gasket has a solid annular shape, an inside diameter of the gasket is smaller than an outside diameter of the externally threaded portion, and a groove portion whose depth coincides with the direction of the axis is provided over an entire circumference of the gasket, and wherein the gasket comprises an inner peripheral side portion on an inner peripheral side of the groove portion and an outer peripheral side portion on an outer peripheral side of the groove portion, and a thickness of the outer peripheral side portion in the direction of the axis is greater than a thickness of the inner peripheral side portion in the direction of the axis.