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:
Sep. 24, 2013
Filed:
Mar. 17, 2009
Makoto Kuribayashi, Aichi, JP;
Hirokazu Kurono, Aichi, JP;
Toshitaka Honda, Aichi, JP;
Tomoaki Kato, Aichi, JP;
Makoto Kuribayashi, Aichi, JP;
Hirokazu Kurono, Aichi, JP;
Toshitaka Honda, Aichi, JP;
Tomoaki Kato, Aichi, JP;
NGK Spark Plug Co., Ltd., Nagoya, JP;
Abstract
An isolation portion (P) of an insulator () of a spark plug () electrically insulatively isolates a front end portion () of a center electrode () and a holding portion () of a metallic shell () from each other and has an intermediate portion (P) which extends while its outside diameter varies, thereby ensuring an insulation distance between the two portions. The ratio (S/V) of the surface area (S) of the outer surface () of the isolation portion (P) to the volume (V) of the isolation portion (P) satisfies the relation 1.26 mm≦S/V, whereby the insulation distance between the front end portion () and the holding portion () is sufficiently ensured while existing dimensional conditions are held unchanged. Through satisfaction of the relation S/V≦1.40 mm, an increase in temperature of the center electrode () that accompanies an increase in the amount of heat received from a combustion chamber owing to an increase in the surface area (S) of the outer surface () is restrained, thereby maintaining a required heat value.