IGNITION DEVICE HAVING AN ELECTRODE TIP FORMED FROM AN IRIDIUM-BASED ALLOY

摘要

An ignition device such as a spark plug (10) having center and ground electrodes (16, 18), at least one of which includes a firing tip (20, 22) formed from an alloy containing iridium, rhodium, tungsten, and zirconium. With the inclusion of tungsten and zirconium in the alloy, the percentage of rhodium can be kept relatively low without sacrificing the erosion resistance or reduced sparking voltage of the firing tip. In one embodiment, the firing tip (20, 22) contains 2 wt % rhodium, 0.3 wt tungsten, 0.02 wt % zirconium, and the balance iridium.