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. 19, 2006
Filed:
Dec. 03, 2004
Hirofumi Suzuki, Kuwana, JP;
Seiji Amakusa, Kasugai, JP;
Hirofumi Suzuki, Kuwana, JP;
Seiji Amakusa, Kasugai, JP;
Denso Corporation, , JP;
Abstract
A spark plug includes a metallic housing, an insulator fixed in the metallic housing, a center electrode fixed in the insulator, a ground electrode opposed to the center electrode via a spark discharge gap, and a protective coat formed on the surfaces of a metallic housing and a gasket. The protective coat includes a galvanized film formed on the surfaces of the metallic housing and the gasket and a chromate film successively laminated on the galvanized film. The chromate film is hexavalent chromium-free and contains trivalent chromium as a major component. The chromate film has a film thickness not smaller than 0.05 μm and not greater than 0.18 μm, and the chromate film contains a metallic component which is robust against oxidation compared with zinc. Furthermore, the chromate film has a film hardness equal to or less than 1 GPa in the temperature range from a room temperature to 180° C.