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:
Jul. 24, 2001
Filed:
Apr. 29, 1999
Hirohito Ito, Nagoya, JP;
Hiroyuki Tanabe, Nagoya, JP;
NGK Spark Plug Co., Ltd., Nagoya, JP;
Abstract
The invention provides a spark plug having an insulator which is composed mainly of alumina, and which is more superior in voltage endurance characteristics at high temperatures as compared with the prior-art materials. An insulator,of a spark plug,is made of an insulating material which is composed mainly of alumina, and which contains Al component within a range of 95 to 99.7 wt % in weight converted to Al,O,, and in which an area ratio occupied by alumina base principal-phase particles with particle size not less than 20 &mgr;m is not less than 50% as a cross-sectional structure of the insulator is observed. By making the alumina base principal-phase particles appropriately coarse like this, the voltage endurance characteristics of the insulator can be remarkably improved.