Patent ID: 6700317
Filing Date: 2004-03-02
Classification: H01T

Abstract:
A manufacturing method for a spark plug employed in an internal combustion engine, said spark plug comprising a center electrode and a ground electrode disposed in an opposed relationship, and an iridium alloy firing tip fixed to at least one of opposing portions of said electrodes by resistance welding, wherein said iridium alloy firing tip chiefly contains iridium, said iridium alloy firing tip comprises a stem and a head, said head being integrally formed from a base end of said stem with a diameter of said head larger than a diameter of said stem, said head having a cross-sectional area continuously decreasing with increasing distance from a maximum diameter portion positioned close to said stem to a distal end positioned remote from said stem, said manufacturing method comprising a welding operation for fixing said iridium firing tip to said opposing portion by resistance welding,said welding operation comprising the steps of: bringing said distal end of said head of said iridium alloy firing tip into contact with said opposing portion, and applying a pressing force to said head during resistance welding operation for forcing said maximum diameter portion to sink in a melted portion of said opposing portion until the base end of said stem extending from paid maximum diameter portion is embedded in said melted portion of said opposing portion; and further comprising a step of caulking said opposing portion after said head of the firing tip is embedded in said opposing portion, so that said base end of said stem extending from said maximum diameter portion is surrounded or wrapped by said opposing portion.