Knock detection apparatus for an internal combustion engine

Abstract

To obtain a knock detection apparatus for an internal combustion engine which may obtain a good knock pulse S/N even if an ionic current generation amount is changed by the change of a kind of fuel or plugs, a vibratory component superimposed on an ionic current generated by combustion of fuel is extracted and shaped in waveform into a pulse waveform by comparison with a threshold value, the number of the pulses in the pulse waveform is calculated by a calculation unit, and a control of an ignition timing is performed on the basis of an output result of the calculation unit. The knock detection apparatus for an internal combustion engine comprises an integration circuit for integrating (charging) the vibratory component superimposed on the ionic current and a discharge circuit for discharging a predetermined amount of charge from the integrated charge. The threshold value is self-adjusted by a balance of charge/discharge between the integration circuit and the discharge circuit.

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