Programmed multi-firing and duty cycling for a coil-on-plug ignition

Abstract

An ignition system for multi-firing a spark plug of a spark ignition internal combustion engine and for detecting auto-ignition utilizing the spark plug as a feedback element. The ignition system includes a pulse transformer connected to a spark plug, a distribution element coupled to the transformer, a timing element connected to the distribution element, a controller, an engine position sensor and a spark discharge detection circuit. Based on engine parameters, the controller loads the timing element with the appropriate signals and triggers one of three timers. The triggered timer begins to count down and times-out at the appropriate engine position either ignition or simply for auto-ignition. This triggers a second timer which enables yet another timer that provides control signals to the distribution element to produce a series of voltage signals of a predetermined magnitude applied by the transformer at the spark plug. These control signals are continuously provided until the second timer times-out ending that cycle of the system. If auto-ignition is occurring in the combustion cylinder, at least one of the voltage signals applied at the spark plug will discharge. The discharge circuit will sense the discharge and provide a signal to the controller indicating auto-ignition thereby allowing the controller to respond accordingly.