Spark plug and a method of making of same

摘要

In a spark plug including a cylindrical metallic shell having an insulator in which a center electrode is placed, a front end of which somewhat extends beyond the insulator, a noble metal portion is bonded to an outer side wall of the front end of the center electrode by means of laser beams so as to form a spark gap between the noble metal portion and a ground electrode which is depended from the metallic shell. The noble metal portion has a molten alloy layer in which the center electrode is melted into the noble metal portion, and a diffused alloy layer in which the noble metal portion is diffused into the center electrode.