| 摘要 |
PURPOSE:To detect a knocking phenomenon with high accuracy over a wide range of rotational frequencies, by varying the band width of a BPF in response to the rotational frequency of an engine and detecting the natural frequency signal generated by the knocking. CONSTITUTION:The output signal of a vibration pickup 11 is amplified by an amplifier 13, and the natural frequency signal of knocking is extracted by a band width variable BPF 14. At the same time, the ignition timing input is converted into a rotational frequency. A control part 16 decides the band width of the BPF 14 by the information on the band width of a BPF corresponding to the rotational frequency written into an ROM 17 and on the basis of the output of rotational frequency counter 15. A comparator 20 compares the signal passed through an averaging circuit 18 and an amplifier 19 with the signal level of the BPF 14 to decide the knocking. In other words, the knocking detection accuracy can be improved over a wide range since an optimum band width of a filter can be set in response to the rotational frequency. |
