Nippondenso Co., Ltd.

Kabushiki Kaisha Toyota Chuo

Kabushiki Kaisha Toyota Chuo Kenkyusho and Nippondenso Co., Ltd.

Tomoji Ishiguro

Kanji Higuchi

Minoru Nagai

Tokuhiko Okamoto

Minoru Konaka

Koichi Nakajima

Kenji Sasaki

A spark plug for an internal combustion engine comprises (a) an insulator surrounding a central electrode and (b) a housing having a grounded electrode and disposed on the periphery of the insulator. A taper-nose portion of the insulator, which is designed to be exposed to unburnt carbon in combustion gases of a combustion chamber, is modified to facilitate carbon removal from the taper-nose portion and to maintain excellent electrical insulation. The modification comprises a coating of a mixture of vanadium oxide and zirconium oxide in the form of a porous layer or a sponge-like porous layer having an irregularly-shaped structure with pores; it is fixed to the exposed surface of the taper-nose portion to improve the self-cleaning ability of the spark plug without decreasing the degree of electrical insulation provided by the insulator. The coating of the mixture having the porous structure is formed by applying a suspension of the mixture to the taper-nose portion of the spark plug and by drying the same in situ. The resulting coating is then heated further to obtain a more adherent coating of increased durability and better self-cleaning ability.

Insulator on spark plug electrode coated with zirconium and vanadium

A spark plug, wherein a central electrode is electrically insulated from an uter electrically-conductive casing (ground to an internal combustion engine when in use) by an insulator sealed in the casing, separating the central electrode from the casing and having a taper-nose portion which is designed to be exposed to unburnt carbon in combustion gases of a combustion chamber, is modified to facilitate carbon removal from the taper-nose portion. Discrete isolated particles or isolated aggregates of particles of vanadium oxide are adhered over the exposed surface of the taper-nose portion to improve the self-cleaning ability of the spark plug without decreasing the degree of electrical insulation provided by the insulator. The particles of vanadium oxide are formed from a suspension which is applied to the surface of the taper-nose portion of the spark plug. The resulting coating is then dried in situ. Further heating results in having vanadium oxide particles, in insular form, firmly adhered to the surface of the taper-nose portion.

Spark plug having vanadium oxide islands on central insulator

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Aichi, Japan

Tomoji Ishiguro