Insulator on spark plug electrode coated with zirconium and vanadium oxides

摘要

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.