DETECTOR FOR KNOCKING

PURPOSE:To detect a reliable knocking, by a method wherein a circuit time constant of an output of a mean value of an oscillating sensor at a given crank angle range of an engine is made larger than that at other range to compare it with a sensor outut at a given crank angle range. CONSTITUTION:An oscillating sensor signal applied to an input terminal 21 is inputted to an amplifier 23 and a mean value output circuit 24 through a selection amplifier 22. Meanwhile, an ignition timing signal connected to a contact point is applied to an input terminal 38. A signal inputted to the circuit 24 is integrated after passing a rectifying circuit 25. At a given crank angle range, an analogue switch (S) 26 is closed, an S27 is opened, and at a crank angle range other than the given crank angle range, the S26 is opened, and the S27 is closed. Thus, a time constant is made large at the given crank angle range. A comparator 33 compares the circuits 23 and 24 with each other, and if a result exceeds a given ratio, an output pulse is outputted. A counter 35 counts a pulse at the given crank angle range to set an FF36, and a reliable detecting signal can be obtained at a knocking detecting output terminal 37.