Internal combustion engine knock sensing method and system

摘要

To recognize knocking conditions in signals derived from a knock sensor, which signals representative of knocking may be masked by background or noise signals, and to clearly distinguish the knocking signal from background or noise signals, the knocking signals are integrated with respect to measuring or strobing intervals during a predetermined angle of crankshaft rotation, digitized in an A/D converter (7) and then compared in a comparator (9) with the same signals which have been passed through a low-pass digital filter (8) to compare the integrated, digitized signal of a then occurring combustion process or event with similar signals of prior combustion processes or events to thereby recognize and distinguish knocking signal conditions from noise signal conditions; digital filtering and comparison as well as sequence timing can be carried out in a single microprocessor (FIGS. 2:14), earlier combustion events being weighted in accordance with the remoteness of their occurrence and/or engine speed and engine loading, the reference signal, for example, being generated in accordance with the formula: y(ti)=(1-k).y(ti-1)+kx(ti) wherein y(ti) is the reference signal; i is the count index of the respective number of combustion cycles of the respective cylinder; x(ti) is the instantaneous digitized integrated value; and k is the weighting factor with which the then pertaining digitized integrated value is weighted to form the new reference value. Combustion processes which resulted in knocking can be eliminated from forming part of the comparison.