Detection of knock in internal combustion engines

Claim 1

Apparatus for detecting the presence of knock in a spark ignition engine comprising: a. input terminal means arranged to be connected to at least one pressure transducer mounted within a combustion chamber of said engine for direct reception of pressure waves generated in the chamber and adapted to provide signals indicative of pressure in the engine; b. differentiating means providing from said pressure-indicative signals a varying waveform representative of the rate of change of pressure in the engine; c. gating means including a tuned amplifier resonant at a frequency characteristic of knock operative to extract from said varying waveform only those peaked portions thereof representative of knock; d. a threshold level detector coupled to said gating means and effective to provide an output only in response to knock peaks exceeding a predetermined amplitude; e. signal generator means connected to said threshold level detector and arranged to provide constant amplitude pulses in proportion to the number of peaks in the output from said threshold level detector; and f. electroacoustic indicator means connected to receive said constant amplitude pulses and providing therefrom an aural indication of any knock.