Electronic ignition system

Abstract

The timing of ignition pulses supplied to an engine is controlled in accordance with a plurality of different operating conditions of the engine to minimize undesirable exhaust pollutants. As the speed of the engine increases from a cranking speed toward an idling speed, the ignition pulses are produced in synchronism with reference timing signals indicating movement of a piston to a top dead center position in a combustion chamber, and upon further increases in engine speed the ignition pulses are produced in synchronism with advanced timing signals generated by an electronic advance means in accordance with the approximate instantaneous position of the piston in the combustion chamber and selected engine operating conditions. The control of the timing of the ignition pulses is transferred between the two different timing signals by a selector means operating in response to control signals indicative of engine speeds above or below a predetermined speed. The control signals are produced by control means in accordance with a speed signal generated in response to the reference timing signals and compared with a reference signal representative of the predetermined speed. To prevent an ignition pulse from being interrupted by changing control signals, the selector means includes a signal processor which responds to the control signals only in accordance with a clock pulse supplied in time lagging relation to the reference timing signals used in producing the control signals.