Digital ignition control for a magnetopowered ignition system of an internal combustion engine

Claim 1

In an ignition system for an internal combustion engine having a magneto generator driven by said engine for powering and timing ignition for said engine, said magneto generator having an AC voltage wave output of a repetition rate corresponding to the engine speed, and means for creating a spark in response to a spark initiation signal: apparatus for creating said spark initiation signal comprising means (32) connected to said output of said magneto generator for deriving a reference signal at a predetermined point in each repetition of said AC voltage wave; means (36,41) furnishing clock signals; digital speed counter means (35) for counting said clock pulses from receipt of a speed counter activating signal until receipt of a speed counter stop signal; storage means (38) for storing a plurality of constants each signifying a desired timing advance at a given motor speed; digital timing counter means (40) connected for activation in response to each reference signal produced by said reference signal deriving means, and digital control means (33) connected to said digital speed counter means, said storage means, and said digital timing counter means for furnishing said speed counter activating and stop signals in response to selected ones of said reference signals so that the count on said digital speed counter means upon receipt of said speed counter stop signal constitutes a motor speed specifying signal, addressing said storage means with said motor speed specifying signal, thereby reading out a count value indicative of said desired timing advance at said then present motor speed, furnishing said timing advance count value to said digital timing counter means for entry at the times of its activation by said reference signals, and furnishing said spark initiating signal when said timing counter means reaches a count indicative of the end of a time interval corresponding to said count value.