Patent ID: 6731052
Filing Date: 2004-05-04
Classification: H01T

Abstract:
A spark plug for an internal combustion engine comprising:a metallic shell having an externally threaded portion; an insulator disposed within the metallic shell and having an axial bore; a center electrode disposed within the axial bore of the insulator; and a ground electrode connected to a front end face of the metallic shell and having an end opposite to a front end face of the center electrode; wherein a cross section of the ground electrode is so shaped as to provide a side surface at one of opposite sides which faces an outer circumferential periphery of the front end face of the metallic shell, with a narrower central side surface section than that of a side surface at the other of the opposite sides, the central side surface section at one of the opposite sides being parallel and opposite to the central side surface section at the other of the opposite sides, and wherein the cross section of the ground electrode is so shaped as to satisfy (L/2)2+{t+(B/2)}2=(A/2)2,L=2[(A/2)2âˆ’{(B/2)+t}2]Â½,(Aâˆ’B)/32âˆ’{(B/2)+t}2]Â½2âˆ’{(B/2)+t}2]Â½, (Mâˆ’1.7 P)&lE;A