US 4,111,035 AGranted

Engine knock signal generating apparatus with noise channel inhibiting feedback

AssigneeGeneral Motors Corporation

InventorsGene A. West, Glen C. Hamren

Life of this patent

Estimating the term…

Loading patent…

Abstract

A vibration sensor mounted on an internal combustion engine characterized by knock-induced vibrations at a characteristic frequency and by other vibrations is tuned to resonate at substantially the characteristic frequency. A bandpass filter tuned to the characteristic frequency is connected to the vibration sensor output; and the output of the filter is provided to one input of a comparator and to average detector circuitry for generating a unidirectional noise reference signal representing noise at the characteristic frequency, which signal is provided to the other input of the comparator. The knock signal, obtained from the output of the comparator and comprising pulses corresponding to knock-induced peaks of amplitude greater than the unidirectional noise reference signal, is fed back through a low-pass filter to the average detector circuitry in sense to oppose increases in the unidirectional noise reference signal during said knock-induced peaks. The connection of the average detector circuitry to the output of the bandpass filter provides adaptability for mistuned sensors; and the negative feedback to the average detector circuitry reduces the distorting effect, amplified by the bandpass filter, of said knock-induced peaks on the unidirectional noise reference signal, which might otherwise distort the output knock signal.

Apparatus for use with an internal combustion engine having ringing knock-induced vibrations at a characteristic frequency and other vibrations, the apparatus being effective to generate knock signals representing the knock level therein and comprising, in combination:

a vibration sensor mounted on said engine and responsive to both said ringing knock-induced vibrations and said other vibrations to generate a signal;
a bandpass filter having maximum transmission at said characteristic frequency and responsive to the signal from said sensor during a knock-induced ringing vibration to generate a filtered sensor signal having attenuated components at frequencies other than the characteristic frequency compared with those at the characteristic frequency;
average detector means responsive to said bandpass filter for generating from the filtered sensor signal a unidirectional noise reference signal generally proportional to the average unidirectional amplitude of the filtered sensor signal at a higher amplitude than all but the peaks of those components due to knock-induced engine vibrations;
a comparator effective to compare the filtered sensor signal to the unidirectional noise reference signal and to generate knock signals when the filtered sensor output signal exceeds the unidirectional DC noise reference;
low-pass filter means responsive to said knock signals to generate a unidirectional noise reference inhibit signal therefrom;
feedback means connected to apply said unidirectional noise reference inhibit signal to said unidirectional DC noise reference signal generating means in sense to limit the unidirectional noise reference signal when knock signals are generated, whereby the tendency of components due to knock-induced vibrations in the filtered sensor signal to falsely increase the unidirectional noise reference is reduced and the knock signals more accurately represent the level of knock in said engine.

3 more elements

Abstract

Claims2