| 摘要 |
PURPOSE:To reliably prevent preignition by judging as abnormal combustion when an output is generated by an ion sensor prior to ignition and correcting the air-fuel ratio to the rich side by a predetermined quantity when this judgment is made. CONSTITUTION:An ion sensor 10 outputting a pulse signal whenever it detects an ion current is installed in a combustion chamber at a position apart from an ignition plug 9 by a predetermined distance, and the combustion speed is detected by measuring the propagation time of flames from the ignition plug 9 to the ion sensor 10 with a control unit 12. The control unit 12 is also constituted so as to judge as abnormal ignition when an output is generated by the ion sensor 10 prior to ignition. When abnormal combustion is judged, a fuel injection valve 6 is controlled to correct the air-fuel ratio of the air-fuel mixture to the rich side by a predetermined quantity.
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