Ngk Spark Plug Company, Limited

Yuusuke Teranishi

Kazuhiko Mori

Hironobu Mizutani

Kentaro Kiuchi

A spark plug having a ceramic insulator held by a crimp portion of a metallic shell. The crimp portion satisfies a relation of A&#x2265;1.7 mm and a relation of t&#x2265;1.20 mm in a cross section of the crimp portion taken along a plane containing the axial line, where A is the distance between a closest point which is a point within the cross section closest to the ceramic insulator and an intersection at which a first orthogonal line passing through the closest point and orthogonal to the axial line intersects with an outer circumference of the crimp portion, and t is a thickness of the proximal end of the crimp portion.

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Aichi, Japan

Yuusuke Teranishi