Spark plug including electrode with protruding portion for holding noble metallic chip, and method of making the same

摘要

Center and earth electrodes are melted at the predetermined regions on the tip thereof where noble metallic chips are fixed. Then, the noble metallic chips are sunk in the melted portions of these center and earth electrodes so as to form protruding portions along outer peripheries of the noble metallic chips. Thus, the noble metallic chips are fixed to the electrodes through the protruding portions. Next, the noble metallic chips are irradiated by energy-condensing light through the protruding portions thus formed. With this irradiation, the center electrode is welded to one noble metallic chip, while the earth electrode is welded to the other noble metallic chip.