Engine ignition timing with knock control by combustion pressure harmonic amplitude ratio

摘要

An ignition timing control for an internal combustion engine subjects a combustion pressure signal to multiple switched capacitor bandpass filters with frequencies controlled in phase lock loop from engine speed to generate harmonic wave signals at frequencies which are constant multiples of the varying firing frequency. The phase difference between the peaks of two harmonics such as the second and fourth is used to control ignition timing to a phase difference of zero, in some cases with ignition pulses referenced to the detected peak of the first harmonic (fundamental) rather than a detected crankshaft position. The ratio of peak amplitudes between two harmonics such as the first and fourth is used to control dilution by EGR or variable valve lift to a predetermined ratio and may also be used to retard ignition timing from the normal timing to reduce knock. The ratio of the peak amplitude of subharmonics to the fundamental may be used as a roughness or driveability sensor.