JPS55151169A - Digital ignition timing controlling system - Google Patents

Abstract

PURPOSE:To simplify the circuitry of a digital ignition timing controlling system of the type employing two counters and setting a dwell time on the basis of phase difference of the outputs of the above two counters, by controlling operation of the two counters by a single ignition timing setting means. CONSTITUTION:Output of sensor 1 for detecting a fixed rotational position of crank shaft is given via wave-form shaping circuit 2 to phase locked loop (PLL) 3 and counters 9, 10. The phase locked loop PLL3 is constituted by a phase detector 4, low-pass filter 5, a first voltage-controlled oscillator 6, and frequency divider 7 which divides the frequency of the output of said oscillator 6 and gives it to detector 4. When output pulses of the first and a second voltage controlled oscillators 6, 8 are counted from a setting value, afforded from a common ignition timing setting means to preset terminals Ps of oscillators 6, 8, to number n, counters 9, 10 produce output ''1''. On the other hand, FF12 gives output ''1'' to ignition circuit 14 continuously from the time when it is reset by the output of counter 10 to the time when it is set by the output of counter 9.