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:
Feb. 10, 2015
Filed:
Dec. 22, 2011
Takehito Kuno, Nagoya, JP;
Osamu Yoshimoto, Inazawa, JP;
Tomoo Tanaka, Kitanagoya, JP;
NGK Spark Plug Co., Ltd., Aichi, JP;
Abstract
It is an object of the present invention to provide a spark plug having a ground electrode joined securely by electric resistance welding. The spark plug includes a cylindrical metal shell and a ground electrode joined by electric resistance welding to an end portion of the metal shell. The metal shell has a high hardness region formed with a Vickers hardness of 3×10to 5×10Hv in the end portion thereof in such a manner that the high hardness region, when viewed in cross section along a plane including an axis of the spark plug and an axis of the ground electrode, has a length d of 0.3 to 0.8 mm from a ground electrode side welding boundary to a metal shell side welding boundary in a direction of load applied during the electric resistance welding.