Denso Corporation

Hirotaka Aida

Tsunenobu Hori

Ken Hanashi

Satoru Kadowaki

Hiroya Ishiguro

Kenka Tsubota

A method of manufacturing a spark plug having an attachment fitting, an insulator, a center electrodeand an earth electrode. While fixed to attachment fitting, earth electrodehas a convex partformed by projecting a part of an opposed surfacetoward center electrode, and a concave partformed toward the opposed surfacefrom the earth electrode's back surface. The convex partis disposed so that the extension of a shaft center of the convex partpasses through the area in which the concave partis formed. The relation Ss is realized when an area of an opening of the concave partis set to Sand an average cross-section area of a cross section of the convex partperpendicular to an axial direction of the spark plug is set to s.

Method for manufacturing spark plug for internal-combustion engine

A spark plug for an internal-combustion engine comprises an attachment fitting, an insulator, a center electrodeand an earth electrode. While fixed to the attachment fitting, the earth electrodehas a convex partformed by projecting toward the center electrodea part of the opposed surface, which faces the center electrode, of the earth electrode and a concave partformed toward the opposed surfacefrom the earth electrode's back surfacewhich is the reverse side of the opposed surfaceof the earth electrode. The convex partis disposed so that the extension of a shaft center of the convex partmay pass through the area in which the concave partis formed. A relation of S&#x3e;=s is realized when an area of an opening of the concave partis set to Sand an average cross-section area of a cross section of the convex partperpendicular to an axial direction of the spark plug is set to s.

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Toyota, Japan

Hirotaka Aida