Patent ID: 6831397
Filing Date: 2004-12-14
Classification: H01T

Abstract:
A spark plug comprising:a tubular housing; a central electrode supported by said tubular housing in said tubular housing with electrical insulation therebetween; an earth electrode extending from one end of said tubular housing; a chip, arranged at an end surface of said earth electrode to face said central electrode, for providing a spark gap between said central electrode and said chip, said chip including a noble metal; and a fused junction layer between said earth electrode and said chip including components of said chip and said earth electrode to fix said chip to said earth electrode, wherein a cross-sectional area of said chip at a tip thereof on the opposite side of said fused junction layer is not less than 0.12 mm2 and not more than 1.15 mm2, and a length from said end surface to a top surface of said tip is not less than 0.3 mm and not more than 1.5 mm, and wherein said fused junction layer has a curved outer surface continuously connecting a peripheral outer surface of said chip to said end surface of said earth electrode, said curved outer surface being concave toward an axis of said chip, said curved outer surface being tapered toward said chip.