Knock control with AGC having reduced knock dependence

Claim 1

A knock control for a spark ignited, internal combustion engine of the type in which knock induced and other bursts of engine vibrations occur, the knock control comprising, in combination: sensing means responsive to the knock induced and other bursts of engine vibrations to generate an electric signal thereof; amplifying means for the electric signal having a gain controllable by an AGC signal voltage; demodulating means responsive to the output of the amplifying means to generate pulses corresponding to the envelopes of such knock induced and other burst of engine vibrations; signal processing means effective to emphasize the components in the demodulated signal due to knock relative to other components therein; means effective to generate an error signal from the difference between the processed output of the demodulating means and a desired signal voltage level; comparator means effective to compare the processed output of the demodulating means with a fixed knock reference voltage to output a pulsed knock signal; integrator means effective to integrate the pulsed knock signal and generate therefrom an AGC control voltage, the integrator means including integration rate control means responsive to the pulsed knock signal output of the comparator means to slow the integration rate during each pulse thereof and thus reduce the effect of knock on the AGC control voltage and thus stabilize the AGC control; and means effective to generate from the pulsed knock signal output of the comparator means a retard signal and adjust engine spark timing thereby to control knock to a predetermined level.