JPS6483120A - Knocking detector - Google Patents

Abstract

PURPOSE:To detect knocking even in the high speed rotation region of an engine, by counting the number of the pulses from a comparing circuit over a plurality of ignitions and judging knocking when the number of pulses at a plurality of ignitions are a predetermined value or more. CONSTITUTION:A knocking gate circuit 8 (or noise gate circuit 9) gates the vibration signal (a) from a knocking sensor 1 from a knocking gate signal forming circuit 6 (or noise gate signal forming circuit 7) in synchronous relation to the rotation of an engine and extracts a vibration signal (b) [or (c)] within a range easy to generate knocking. The signal (c) is formed as the reference signal (d) of a noise level averaged by an amplifying offset rectifying and smoothing circuit 10. The levels of the signals (b), (d) are compared by a comparing circuit 11 and, when the level of the signal (b) is higher, a pulse signal (e) is generated and the number of the pulses from the circuit 11 are counted over a plurality of ignitions by a knocking judge means 12 and, when said numbers of the pulses are a predetermined value or more, knocking is judged. Therefore, even when the characteristic signal of knocking is out of the range of a knocking signal at one ignition, judge is performed as mentioned above and, therefore, knocking can be detected even in a high speed rotation region.