Ngk Spark Plug Company, Limited

Shoma Tsumagari

Kuniharu Tanaka

Hironori Uegaki

Katsuya Takaoka

Kazuhiro Kurosawa

Kengo Fujimura

Seiji Nakano

An ignition plug comprising: an insulator having a through hole extending from a rear-end side toward a forward-end side; a center electrode inserted at least partially into a portion of the through hole on the forward-end side; a metal terminal member inserted at least partially into a portion of the through hole on the rear-end side; and a seal disposed within the through hole and in contact with the center electrode and an inner circumferential surface of the insulator. The seal contains a glass and an electrically conductive substance, and the glass contained in the seal contains Si in an amount of 50 mass % or more as reduced to SiOand Na in an amount of 0.1 mass % or more and less than 1 mass % as reduced to NaO.

Ignition plug

A spark plug has an insulator, a rod-shaped electrode member disposed in an axial hole of the insulator, and a cylindrical magnetic member disposed on an outer circumference of the electrode member within the axial hole. The insulator includes a large inner diameter region, a middle inner diameter region located frontward of the large inner diameter region and having an inner diameter smaller than that of the large inner diameter region, and a small inner diameter region located frontward of the middle inner diameter region and having an inner diameter smaller than that of the middle inner diameter region. The electrode member is retained on a step portion of the insulator between the middle inner diameter region and the small inner diameter region. The magnetic member is positioned in the axial hole at a location within the large inner diameter region.

Spark plug having the thickness of a magnetic member without excessively narrowing an electrode member

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Nagoya, Japan

Shoma Tsumagari