| 摘要 |
PURPOSE:To detect knocking oscillation stably at high SN ratio, by setting up a waterproof type microphone in cooling water for an engine and detecting the pressure oscillation of water to detect knocking phenomenon. CONSTITUTION:An hydromicrophone consisting of a ceramic piezoelectric element 1, a signal wire 2, a signal wire holder 3 and an output cable 5 is inserted into a flow passage of cooling water for the engine. An output signal from the microphone is amplified by an amplifier circuit 7 and passed through a band pass filter 8 to cut off components other than a characteristic frequency component for knocking, one of outputs from the filter 8 is applied to an analog switch 9 and only the knocking generation timing is connected to a peak holding circuit 10 to hold the peak value and use the value as a knocking signal to be inputted to a comparator 11. The other output from the filter 8 is impressed to an integration circuit 12 to average the output signals of the filter 8 and the average output is impressed to the comparator 11 as a reference signal for the discrimination of the existence of knocking. |
