Abstract: A method and apparatus for manufacturing a spark plug which avoids depth insufficiency of the weld metal portion or thickness insufficiency of the spark portion and which thus enhances the weld strength and service life of the spark portion. According to the method, a noble metal chip is attached to a chip joint face formed on a distal end of a center electrode of a spark plug workpiece, along the direction of the longitudinal axis of the workpiece, so as to form a chip-attached assembly. The chip-attached assembly is irradiated with a laser beam LB so as to form a laser-beam weld metal portion intruding into the noble metal chip and into the chip joint face, thereby forming a noble-metal spark portion having a discharge face.

Abstract: A method for manufacturing a spark plug which reduces the generation of spatters and the possibility of insufficient weld strength resulting from penetration depth insufficiency of a weld metal portion is disclosed. In accordance with the method, a chip joint face formation portion of a center electrode is formed from a heat-resistant alloy predominantly containing Fe or Ni. A noble metal chip is attached to a chip joint face of the chip joint face formation portion to thereby form a chip-attached assembly. A full-circled laser-beam weld metal portion is formed on the chip-attached assembly in such a manner as to intrude into the noble metal chip and into the chip joint face formation portion. A graded-index-type fiber optic cable is used as an optical transmission path extending between a laser beam generator and an optical emission section. A laser beam which is transmitted from the laser beam generator through the cable irradiates the chip-attached assembly while being condensed.

Abstract: A method for manufacturing a spark plug which reduces the generation of spatters and the possibility of insufficient weld strength resulting from penetration depth insufficiency of a weld metal portion is disclosed. In accordance with the method, a chip joint face formation portion of a center electrode is formed from a heat-resistant alloy predominantly containing Fe or Ni. A noble metal chip is attached to a chip joint face of the chip joint face formation portion to thereby form a chip-attached assembly. A full-circled laser-beam weld metal portion is formed on the chip-attached assembly in such a manner as to intrude into the noble metal chip and into the chip joint face formation portion. A graded-index-type fiber optic cable is used as an optical transmission path extending between a laser beam generator and an optical emission section. A laser beam which is transmitted from the laser beam generator through the cable irradiates the chip-attached assembly while being condensed.

Abstract: A method and apparatus for manufacturing a spark plug which avoids depth insufficiency of the weld metal portion or thickness insufficiency of the spark portion and which thus enhances the weld strength and service life of the spark portion. According to the method, a noble metal chip is attached to a chip joint face formed on a distal end of a center electrode of a spark plug workpiece, along the direction of the longitudinal axis of the workpiece, so as to form a chip-attached assembly. The chip-attached assembly is irradiated with a laser beam LB so as to form a laser-beam weld metal portion intruding into the noble metal chip and into the chip joint face, thereby forming a noble-metal spark portion having a discharge face.