| 摘要 |
PROBLEM TO BE SOLVED: To provide a knocking detecting device for an internal combustion engine to set a knock decision period without using a crank angle sensor. SOLUTION: A washer type piezoelectric element mounted on an internal combustion engine is used through an ignition plug as a detecting element 2, a pressure in a cylinder is detected. A knocking detecting device coverts an output from the detecting element 2 into a voltage signal (a detecting signal S1) by a charge amplifier 4. By comparing the signal component of a knocking frequency zone overlapped with the detecting signal S1 with a knock decision level, knock decision is carried out. Further, during a knock decision period, a capacitor C10 is first charged by means the detecting signal S1 by a gate signal generating circuit 10, a charged electric charge is discharged at a specified time constant through a resistor R11, and further, the voltage value Vd of the capacitor 10 is divided by resistors R12 and R13. A voltage value Vg after the division and the detecting signal S1 are compared with each other by a comparator CMP, and the comparing result is outputted as a gate signal to represent a knock decision period. Decision is effected, in order, described above.
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