| 摘要 |
PURPOSE:To detect knocking at a high accuracy in a wide range of revolutions of the engine by making the center frequency of a band pass filter variable according to revolutions of the engine to match the frequency of the knocking. CONSTITUTION:An output signal of a vibration pickup 11 is passed through an amplifier 13 and the natural frequency of the knocking are detected with a f0 variable band pass filter 14. The ignition timing input 12 is converted into revolutions with a revolution meter 15 and information is read out on the f0 value of a band pass filter corresponding to the revolutions written into an ROM17 from the output thereof through a control section 16 to set the f0 value of the filter 14. A comparator 20 compares the signal amplified with an amplifier 19 via an amplifier 13 and an averaging circuit 18 with an output signal of the filter 14 in the level and outputs a signal for the output of the judgement of the knocking. The used of the variable band pass filter 14 allows a highly accurate detection of the knocking in a wide range of revolutions of the engine. |
