Device for automatic control of electronic spark ignition advance for internal combustion engines

Claim 1

Device for the automatic control of spark advance in an electronic ignition system for an internal combustion engine, of the type comprising an ignition spark discharge control circuit which controls the discharge, reference means located on a rotary part of the engine and comprising a protuberance phase-displaced in advance, with respect to a top dead centre reference on the rotary part, by an angle equal to the maximum spark advance angle required, at least one series of teeth located on the said rotary part, first and second electromagnetic pick-ups which cooperate with said protuberance and with said teeth to provide respective electrical output pulses, and a circuit connected to said pick-ups for variation of the instant of discharge, wherein the improvements consists in that the circuit for the variation of the instant of discharge comprises: pulse counter means for counting the pulses emitted by the second pick-up as said teeth pass the said pick-up, in each ignition cycle, means for enabling said counter for a predetermined period of time (T) commencing with the passage of the said protuberance past the first pick-up, memory means for storing the count of said counter means after this predetermined time (T) and for transforming the count into a signal representing a reference value of the required spark advance angle, a parking memory for storing the said reference value, reset means for resetting the said pulse counter means and clearing the memory means of the said reference value upon the next passage of the said protuberance in correspondence with the said first pick-up, comparator means for comparing the said reference value stored in the parking memory with the instantaneous count in the pulse counter means after said resetting thereof, and a spark discharge circuit connected to said comparator means, the latter initiating operation of said spark discharge circuit when said instantaneous count reaches parity with the reference value.