Patent ID: 7557496

Claim:
A spark plug comprising: a center electrode; an insulator having an axial hole extending in an axial direction of the center electrode and holding the center electrode in the axial hole; a cylindrical metal shell surrounding the insulator, and a ground electrode having first and second end portions, an end face of one end portion being joined to a tip face of the metal shell and the other end portion being opposed to the center electrode, wherein an axial line of the metal shell and an axial line of the insulator deviate from one another so that a relationship A>B is satisfied for distances A and B which are defined on a line connecting the center of an inner circle of the tip face of the metal shell and the center of the end face of the one end portion of the ground electrode, where: the distance A is defined as a distance on the side of the ground electrode between the inner circle of the tip face of the metal shell and an intersection line of an outer circumferential surface of the insulator and a plane including the tip face of the metal shell or a projection, onto the plane, of an intersection line of an extended surface of the outer circumferential surface of the insulator and a plane including a tip face of the insulator; and the distance B is defined as a distance on a side opposite the ground electrode between the inner circle of the tip face of the metal shell and the intersection line of the outer circumferential surface of the insulator and the plane including the tip face of the metal shell or the projection, onto the plane, of the intersection line of the extended surface of the outer circumferential surface of the insulator and the plane including the tip face of the insulator, wherein a distance between the inner circle of the tip face of the metal shell and the intersection line of the outer circumferential surface of the insulator and the plane including the tip face of the metal shell or the projection, onto the plane, of the intersection line of the extended surface of the outer circumferential surface of the insulator and the plane including the tip face of the insulator is shorter than or equal to 1.5 mm.