Erosion resistant pencil coil having external secondary winding and shield

Abstract

A method for inhibiting or eliminating case erosion in a pencil ignition coil having an internal primary winding and an external secondary winding and shield. Three alternative means for resisting damage due to the partial discharge phenomenon arising from a high electric field in such coil configurations are provided: (i) applying an ozone resistant coating on the case; (ii) applying a coating on the case for eliminating partial discharge under the shield; and (iii) applying a polyimide tape covering to the case for resisting partial discharge under the shield. Several significant benefits include: an increased commercial value by allowing the use of an efficient internal primary winding which increases energy density and eliminates the need for a spool, thereby lowering the manufacturing costs, the processing costs falling well beneath that of liquid polymer processing, the ease of processing by coating or molding, the reduction of electrical noise, the improved durability even through thermal cycling, and the lowering of case manufacturing costs by allowing the use of lower cost plastic.

Dependencies are inferred from the claim text.