MISFIRE DETECTING APPARATUS FOR INTERNAL-COMBUSTION ENGINE

PURPOSE:To detect misfire by installing two pairs of fail-signal generating circuits of an ignition apparatus having an intermediate tap and setting the trigger voltage lower than the second peak value in the primary voltage wave-form in case of misfire and comparing and discriminating the both. CONSTITUTION:Electric-current control circuits 3a and 3b repete switching alternately on the basis of the signal supplied from a revolution-angle sensor 1, and fail-signal generating circuits 4a and 4b generate the pulses which are synchronized with ignition and has a constant time width. In normal ignition, pulses are generated on two fail-signal lines C and D alternately. When a trouble is generated because of an anomaly, the vibration wave-form having a reverse phase is generated, and when each trigger voltage of the fail-signal generating circuits 4a and 4b is set lower than the second peak voltage in the primary voltage wave-form, pulses are generated at the same time and can be detected by a spark trouble detecting circuit 5. Therefore, the engine can be stopped in case of spark trouble, and therefore, the secondary trouble can be prevented.