Patent ID: 7346983
Filing Date: 2008-03-25
Classification: H01T,Y10T

Abstract:
1. A method for manufacturing a spark plug provided with a housing, a substantially cylindrical center electrode held in an insulated manner in the housing with a tip of the center electrode protruding from the housing, an earth electrode having one end joined to the housing, and a noble metal chip joined on a first end-side surface of an other end of the earth electrode, the earth electrode being bent to form a spark gap between the noble metal chip and the tip of the center electrode, comprising: providing, for a provisional bending process for the manufacture, the spark plug as a work in a condition where the earth electrode is straight and substantially in parallel with an axial line of the center electrode; arranging two searchers individually facing the tip of the center electrode with the tip located therebetween, positions of the searchers in a first direction perpendicular to the axial line being adjusted for every spark plug; driving a bending punch to press a second end-side surface of the other end of the earth electrode down to the searchers so that the earth electrode is provisionally bent at a substantially perpendicular angle to the axial line, the second end-surface being opposite to the first end-side surface; performing a main bending process to adjust dimensions of a spark gap between the tip of the earth electrode and the tip of the center electrode in the axial line direction of the center electrode; measuring, after performing the main bending process, a second shift amount between the noble metal chip and the tip of the center electrode in the first direction along which the searchers are adjusted during at least one of the arranging step and the driving step; and correcting, on the basis of the measured second shift amount, the positions of the searchers for the work to be manufactured next.