Engine ignition system with anti-knock timing shift

Abstract

The operation of the interrupting switch in the primary circuit of an ignition coil triggers a first timing circuit having a fixed interval or one sometimes modified by engine loading, at the end of which a timing interval signal is generated which lasts for a second interval. The latter is applied to switch a resistor across the timing wave generator to load down its output voltage. In this manner, an engine equipped with a simple ignition shift providing spark advance in the low speed region and then steady or slightly retarding timing thereafter, can be caused to provide a retarding priming shift that sets in at a medium speed, increases and then tapers off with higher speeds so as to cover a speed range in which the engine is particularly sensitive to engine knock and avoiding the inefficiencies which would be necessary if the simple ignition shift system had to be backed off to avoid intersecting the knock boundary. It is also possible to utilize the first timing interval to charge or discharge a capacitor to produce an engine speed signal for biasing the threshold of the interrupter switch for control of the dwell angle with respect to engine speed. Two timing intervals can be determined by a single digital counter reset by each ignition pulse and connected with a decoder set to recognize the ends of successive intervals.