Importance

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Abstract

An apparatus for detecting a misfire in an internal combustion engine arranged so that a leak current caused when the insulation of an ignition plug is compensated. An ion current and the leak current can easily be discriminated from each other, whereby the ion current detection accuracy can be improved. The apparatus is provided with a biasing capacitor which is charged with a current flowing at the time of discharge through the ignition plug, a Zener diode for setting the voltage at which the capacitor is charged by this charging, a first semiconductor integrated circuit which detects the charging current flowing through the capacitor and thereafter outputs a control current through a predetermined time period, and which holds a peak value of a voltage converted from the ion current and detects the ion current by comparing the converted voltage value of the ion current and the held peak value.

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First Claim