Ignition system for internal combustion engines

Claim 1

An ignition dwell control system for an internal combustion engine comprising in combination, an engine driven rotary position detector, a signal shaping circuit connected to said detector and adapted to emit pulses at a frequency proportional to the rotary speed of said detector, a tachometric generator connected to said signal shaping circuit and incorporating a current source adapted to draw current at a rate proportional to the frequency of the pulses emitted from said signal shaping circuit, a resistor and an integrating capacitor connected in series with said current source, means actuated in response to the pulses emitted from said signal shaping circuit for periodically resetting said capacitor when said position detector is at a reference position so that the voltage U1 across the capacitor is proportional to the angular displacement of the detector from the reference position, and the voltage U2 across the resistor is proportional to the rotary speed of the detector, a source of threshold voltage U3, a comparator connected to said resistor and integrating capacitor and to said source of threshold voltage, adapted to compare the sum of the position and speed voltages U1 and U2 with the threshold voltage U3 and to produce an output signal when the voltage sum exceeds the threshold voltage, an ignition coil connected to said comparator, and an amplifier interposed between the comparator and the ignition coil and being adapted to allow current to flow through the ignition coil when the comparator produces an output, said coil being adapted to produce an ignition spark output when the comparator ceases to produce an output.