Ignition timing control apparatus with a knock sensor for an internal

Abstract

An ignition timing control apparatus for an internal combustion engine can precisely sense an abnormality or fault in a knock sensing system, and properly control the ignition timing so as to prevent any possible knocking even if there is an abnormality in the knock sensing system. The apparatus includes a first switch for controlling the power supply to an ignition coil, a signal generator for generating an ignition signal in synchrony with the rotation of the engine to open and close the swtich, a resonance type acceleration senor for sensing a vibrational acceleration of the engine and generating a corresponding output signal, a controller for controlling the first switch based on the output signal of the acceleration sensor so that the engine is properly ignited by the ignition coil, a capacitance load having one end connected through a second switch to the output side of the acceleration sensor and the other end thereof connected to ground, an abnormality sensor for sensing an abnormality in a knock sensing system including the acceleration sensor and the controller based on a change in the output of the acceleration sensor in response to the closure of the second switch, whereby the controller controls the first switch based on the output signal from the abnormality sensor in such a manner that it retards the ignition timing of the engine by a prescribed extend from a normal ignition timing at which ignition takes place when there is no output from the abnormality sensor.