Ngk Spark Plug Company, Limited

Kiyohiro Kondo

Akira Suzuki

Mamoru Musasa

Hideki Teramura

A spark plug used in an automotive internal combustion engine. The spark plug includes a center electrode. An insulator is disposed around the center electrode. A metal main body is disposed around the insulator. A ground electrode has a first end section connected to the metal main body, and a second end section located opposite to the center electrode. Additionally, a tip is formed of an alloy whose main component is Ir. The tip is secured to the ground electrode and serving as a spark consumption-resistant electrode material. The tip has an axis directed to the center electrode. In the spark plug, a molten and solidified section formed of alloy is disposed to fix the tip to the ground electrode. The molten and solidified section includes a surrounding molten and solidified section located surrounding a peripheral surface of a major part of the tip embedded in the ground electrode.

Spark plug having a welded electrode and the method of producing the same

A spark plug is disclosed in which, in a cross-section of the metallic shell of the spark plug, a crimped portion of the metallic shell is curved such that an end-side part of the crimped portion approaches the insulator, such that an exterior outline of the crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to the exterior outline at a base point of the crimped curve portion and a radial line perpendicular to the axis of the insulator form an angle of 50&deg;-110&deg;. Accordingly, most of a crimping force is imposed in the axial direction of the metallic shell during crimping, and stress generated in the metallic shell in a radial direction is very small. Thus, the metallic shell can be thin-walled and can maintain its shape with high accuracy after crimping.

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Aichi, Japan

Kiyohiro Kondo