Automatic ignition timing advancing device in ignition system

Abstract

A device for automatically advancing the ignition timing in an ignition system for an internal combustion engine is disclosed, in which the ignition timing is fixed constant in a low speed range of the rotation of the engine, advanced in an intermediate speed range lower than a predetermined rotary speed, and fixed constant again in a high speed range higher than the predetermined rotary speed. In this automatic ignition timing advancing device, a positive pulse signal generated at a first phase corresponding to the ignition timing in the low speed range, a negative pulse signal generated at a second phase corresponding to the ignition timing in the high speed range, and a positive voltage signal having an amplitude increasing with time in the phase range including the first phase and second phase are combined to provide a composite signal used as a control signal for controlling the ignition timing. The negative pulse signal has a large pulse width so that the peak value of the control signal waveform appearing on the leading side of the second phase can be reduced to a level lower than a predetermined level.