To materialize a configuration suitable for miniaturization and stabilization of a discharge position, in a spark plug wherein cylinder parts are provided in a portion where a center electrode faces a grounding electrode, and one end faces of both cylinder parts face each other through a discharge gap.
The diameter T1 of the cylinder part 35 on the center electrode 30 side and the diameter T2 of the cylinder part 45 on the grounding electrode 40 side are both 1.1 mm or less. The axis 35b of the cylinder part 35 on the center electrode 30 side is mutually parallel with the axis 45b of the cylinder part 45 on the grounding electrode 40 side, and they are shifted from each other so that when either one of the axes is extended, the other axis does not exist on the extended line. The displacement x of both of these axes 35b, 45b is 0.05 mm or more, and is not more than the radius of the thicker cylinder part out of both cylinder parts 35, 45.
OKABE SHINICHI
MORITA HITOSHI
BORIKO MADOKA
NIPPON SOKEN
Takahiro Miura
Fumihiro Mizuno