Patent ID: 8432091
Filing Date: 2013-04-30
Classification: H01T

Abstract:
1. A spark plug comprising: a center electrode; an insulator having an axial hole extending in an axial direction and holding the center electrode in the axial hole; a metal shell which holds the insulator and surrounds a radial periphery of the insulator in a circumferential direction; a ground electrode comprising a first end portion joined to the metal shell and a second end portion, the ground electrode being bent such that the second end portion faces a leading end portion of the center electrode; and an electrode chip joined to the ground electrode such that the electrode chip is engaged in a recess portion formed in the second end portion of the ground electrode at a position opposing the leading end portion of the center electrode, wherein the electrode chip is formed by previously welding a chip body portion formed of noble metal or an alloy containing a noble metal as a main component and a chip holding portion formed of Ni or an alloy containing Ni as a main component prior to joining the electrode chip to the ground electrode, wherein the chip holding portion has a recess portion or has an annular shape such that when the chip body portion is welded to the chip holding portion, the chip holding portion surrounds an outer periphery of the chip body portion, wherein a first molten bond is formed by welding the chip body portion and the chip holding portion, and in the axial direction, the first molten bond is positioned so that a surface of the ground electrode which faces the leading end portion of the center electrode is closer to the leading end portion of the center electrode than the first molten bond, and wherein the first molten bond is placed in the recess portion of the second end portion of the ground electrode so as not to be exposed to an outside environment.