Ignition timing control apparatus for an internal combustion engine

Claim 1

An ignition timing control apparatus for an internal combustion engine which comprises: a non-resonance type acceleration sensor which has a piezo-electric element as a vibration detecting element for said engine and a metric screw portion to be engaged with the same; a frequency filter having its central frequency in a range of from 10 KHz to 20 KHz and its band width of 1 KHz or higher, which selectively detects a knocking signal component contained in an output from said sensor; a gate means for interrupting a noise which disturbs detection of the knocking signal contained in an output signal from said frequency filter; a noise level detector for detecting, from an output from said gate means, the level of a mechanical vibration noise of the engine other than the knocking signal; a comparing and integrating means for integrating a pulse signal obtained by comparing an output voltage from said noise level detector with an output voltage from said gate means; a rotation signal generator for generating an ignition signal in response to a predetermined ignition advance angle characteristic; a waveform-shaping circuit for shaping the waveform of the output of said rotation signal generator and for controlling the closing angle of an ignition coil; a phase shifter for shifting with delay of time the output signal of said waveform-shaping circuit in response to the output of said comparing and integrating means so that a switching circuit for turning-on and off said ignition coil is actuated; and a gate timing controller triggered by the output of said phase shifter so as to interrupt the ignition noise by closing the gate of said gate means for a predetermined time from the time of ignition.