The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 12, 1999
Filed:
Jan. 14, 1997
Kenichi Nishikawa, Aichi, JP;
Makoto Sugimoto, Aichi, JP;
NGK Spark Plug Co., Ltd., , JP;
Abstract
A spark plug for an internal combustion engine. The spark plug includes an insulator coated with glaze in an area extending from a head portion to a trunk portion of the insulator. Preferably, the glaze is prepared from B.sub.2 O.sub.3 --SiO.sub.2 glass containing two or more oxides selected from the group consisting of Al.sub.2 O.sub.3, Na.sub.2 O, CaO, ZnO, BaO, Li.sub.2 O and Bi.sub.2 O.sub.3. The glaze is prepared by dry-mixing a plurality of powder materials, melting the resultant mixture in water for vitrification, wet-powdering the resultant vitrification, and adding an organic binder to the resultant powder. The glaze is applied to the insulater and fired at a glost temperature of not more than 1150.degree. C. The Pb content of the glaze is not more than 10 wt. % in terms of PbO. Accordingly, even when a strong electric field is induced at the trunk portion of the insulator, the conversion of Pb to conductive substances is very little or zero. As a result, the flashover voltage between the terminal electrode and the metallic shell of the spark plug is less likely to decrease, thus preventing a spark failure of the spark plug.