Combustion condition detecting apparatus for an internal combustion engine

Abstract

To provide a combustion condition detecting apparatus for an internal combustion engine, which may well detect the combustion conditions such as discrimination of a combustion cylinder and knock generating condition and may reduce a circuit scale therefor, there are provided an ignition coil 21 provided for each cylinder; an ignition plug 20 for discharging by the application of the ignition high tension voltage to ignite mixture within the cylinder; a bias circuit 1 provided for each cylinder for applying a bias voltage to the ignition plug 20; an ionic current detection circuit 2 provided for each cylinder for detecting as an ionic current detection signal an ionic current 6 generated in the cylinder that is immediately after the combustion of the mixture; a knock signal processing circuit 4 provided one for a combination of a plurality of cylinders that are every two or more cylinders in ignition order on the basis of a sum of the ionic current detection signals; and an ECU 5 for detecting the combustion condition of the ignition plug on the basis of the knock signal.

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