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. 30, 2003
Filed:
Nov. 03, 2000
Hiroyuki Kameda, Aichi, JP;
Yoshihiro Matsubara, Yokkaichi, JP;
NGK Spark Plug Co., Ltd., Nagoya, JP;
Abstract
A spark plug includes a metallic shell having a stepped portion an insulator disposed inside the metallic shell, while being engaged with the stepped portion of the metallic shell, and having an axially extending through hole; a center electrode fixed within the through hole of the insulator; and a ground electrode having a tip end portion bent toward the center electrode to thereby form a spark discharge gap. The insulator is formed such that the outer diameter of the insulator decreases toward the tip end side from an engagement position at which the insulator engages the stepped portion and such that the diameter decreases stepwise at an axial position between the engagement position and the tip end of the insulator. The diameter reduction ratio Y =D /d is 0.6 or less in a region of at least 2 mm extending from the tip end surface of the insulator toward the base end side, wherein D represents the outer diameter of the insulator measured at an arbitrarily determined axial position, and d represents the inner diameter of the tip end portion of the metallic shell. Further, a clearance ratio Y =(d −D )/d is 0.4 or greater in a region of at least 1 mm extending from the tip end surface of the metallic shell toward the base end side.