Digital electronic ignition spark timing system

摘要

The output signal pulses of a constant frequency oscillator are counted between successive timing signals, each of which corresponds to a cylinder of an associated internal combustion engine. The total number of pulses counted during each count period is stored and employed to derive an engine speed advance binary code representation of the number of pulse counts corresponding to the predetermined number of degrees ignition spark engine speed advance for the speed at which the engine is operating. Vacuum advance binary code representation of the number of pulse counts corresponding to the predetermined number of degrees ignition spark vacuum advance is also produced and added to the engine speed advance binary code representation. The difference between the sum of the engine speed and vacuum advance binary code representations and the stored total number of pulses counted during the previous count period and the running total of pulses being counted during the present count period are applied to a comparator circuit which produces an output ignition initiating signal upon the detection of an equality. The oscillator circuit output signal pulses are also counted in another counter circuit between successive ignition initiating signals. The total number of pulses counted between successive ignition initiating signals is employed to derive a dwell initiating signal.