| 摘要 |
PROBLEM TO BE SOLVED: To improve the ratio of S/N by optimizing a detection range and enhance the accuracy of the detection of a combustion state, knocking in particular, of an internal combustion engine. SOLUTION: This device is provided with ignition plugs 4 to ignite the air- fuel mixture in the cylinders of an internal combustion engine by discharging electricity due to the application of high voltage for ignition, as bias circuit 5 to apply bias voltage to the ignition plugs 4, an electric current detection circuit 21 to detect the ion electric current corresponding to the quantity of the ion generated in the cylinder in which air-fuel mixture is burning as an ion electric current detection signal, knock signal processing means 24 to 27 to generate knock judging signals showing the knock generation state in the internal combustion engine based on the ion electric current detection signals, and an ECU 15 to detect the combustion state in ignition plugs based on the ion electric current signals and knock judging signals. Through this constitution, the knock signal processing means 24 to 27 sets the detection interval of knock judging signals based on the integral value of the ion electric current signals.
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