METHOD FOR MANUFACTURING A CENTER ELECTRODE FOR A SPARK PLUG

摘要

A method of manufacturing an electrode (20) for a spark plug (32) wherein a platinum cup member or (54) cap is attached to a tip (12) that extends from an extruded inconel body (10). The inconel body (10) is sequentially extruded from a cylindrical blank to produce a tip (12) on a first end (12) and a cup shaped (16) opening that extends from a second end (14) toward the first end (12). A copper core (18) is inserted into the cup (16) and the cylindrical blank (10) thereafter extruded to a substantially final length for the resulting center wire (20). In order to assure a uniform thickness, a source of platinum (38) is rolled into a thin strip and a (44) disc is punched therefrom. The disc (44) is formed into a cap member (54) which has the shape of a cup. The resulting cap member (54) and center wire (20) are placed in a fixture and the cap member (54) is moved toward the center wire (20) until the cap member surrounds the tip (12). Thereafter electrical current is passed through the cylindrical body (20) and cap member (54). The electrical current is terminated when the thermal energy heats the inconel adjacent the junction to its melting point. A compressive force is maintained on the center wire (20) and cap member (54) causing the cap member to fuse to the tip (12) and complete the manufacture of the electrode (20).