Patent ID: 6078129
Filing Date: 2000-06-20
Classification: H01T

Abstract:
A spark plug for an internal combustion engine comprising:an insulator having a through-hole formed therein;a center electrode, disposed at one end of the through-hole;a metal housing holding the insulator therein;a ground electrode connected to the metal housing and disposed to face the center electrode, forming a spark gap therebetween; anda noble metal chip bonded on at least either the center electrode or the ground electrode so that the noble metal chip faces the spark gap, wherein:the noble metal chip is bonded with a molten bond formed by laser beam welding;the noble metal chip is made of an iridium alloy having a melting point higher than 2,200.degree. C.;the molten bond contains a noble metal, the amount of which is larger than 1-weight-percent of the molten bond, the noble metal having a melting point in a range from 1,500 to 2,100.degree. C. and a linear expansion coefficient in a range from 8.times.10.sup.-6 to 11.times.10.sup.-6 /.degree.C.; anda thickness of the molten bond in which more than 1-weight-percent noble metal is contained, measured at a position half a radius of the noble metal chip from a center thereof, is greater than 0.2 mm.