| 摘要 |
PROBLEM TO BE SOLVED: To provide a sparking plug which can solve the problem that the chip of a noble metal is difficult to weld on a discharge portion in its earth electrode because an Al-aggregation layer is formed on the surface layer of an alloy used for the earth electrode though the use of the alloy containing not less than 0.8 wt% of Al with the main component of Ni is effective in improving the performance of the sparking plug, and on the other hand if tried to remove the Al-aggregation layer completely, that a steep rise in a working cost is taken place, . SOLUTION: In this sparking plug, a noble metal chip 5 is welded onto at least an earth electrode 4 in a counter electrodes with the chip being disposed in a position facing a center electrode. Here, the opposing electrodes are composed of the center electrode and the earth electrode 4, and disposed in an opposing and spaced relationship with each other with a spark discharge gap formed therebetween. In addition, the base material of the earth electrode 4 is made of the alloy that contains not less than 0.8 wt% of Al with a main component of Ni and further has an Al-aggregation layer 4a in its surface layer, and the area occupancy ratio of Al-aggregation X in the region within 20μm beneath the noble metal chip 5 in the half section including the welded noble metal chip 5 is not more than 30%. COPYRIGHT: (C)2004,JPO&NCIPI
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