Engine knock control with detector and filter

摘要

A spark ignited internal combustion engine includes apparatus effective to generate a signal from knock-induced and other ringing vibration bursts with amplification over a wide passband around the characteristic knock frequency. The signal is demodulated to obtain the envelope pulses of the knock and other vibration bursts and filtered in a low pass filter having a half power frequency from 60-200 Hertz. The output of this filter, in which other pulses are significantly attenuated with respect to knock pulses, is further processed to obtain a knock control signal which controls spark retard apparatus to limit knock intensity.