Ignition timing control system for internal combustion engines

Claim 1

In an ignition timing control system for an internal combustion engine including means for detecting a first set of engine operating parameters and for generating an engine condition signal indicative thereof; means, responsive to said engine condition signal, for computing a base advance angle and for generating a digital signal representative thereof; first counter means for counting the digital signal from said base advance computing means and for generating an output signal when said first counter means reaches a predetermined count value; and igniter means, responsive to the output signal of said first counter means, for generating an ignition signal; the improvement comprising: means for detecting the occurrence of an engine knock and generating a knock detection signal indicative thereof; second counter means for counting the number of output signals from said first said counter means and for generating an output signal when a number m of said output signals from said first counter are counted; timing means, connected to said second counter means, for determining the number m to which said counter means counts; third counter means, connected to said knock detecting means and to said counter means, for counting the number n of said knock detection signals during a period that said second counter means counts the number m; dividing means, connected to said timing means and to said third counter means, for computing a knocking ratio expressed by n/m; comparator means, connected to said dividing means, for comparing the knocking ratio n/m with an upper and a lower level; and means, connected to said comparator means and to said first counter means, for altering the count value of said first counter means in accordance with a comparison result from said comparator means.