Patent ID: 8694226

Claim:
A control apparatus for an internal-combustion engine, comprising: an air-fuel ratio detector configured to detect an air-fuel ratio of the internal-combustion engine having a plurality of cylinders; an intake air amount detector provided in an intake passage of the internal-combustion engine and configured to detect an intake air amount; an atmospheric pressure detector configured to detect an atmospheric pressure; and a first diagnosis device configured to diagnose whether cylinder-to-cylinder air-fuel ratio imbalance occurs, the first diagnosis device comprising: an exhaust flow rate calculator configured to calculate an exhaust flow rate that reflects a volume flow amount of exhaust gas flowing through an exhaust passage of the internal-combustion engine by performing volume-correction of the intake air amount detected by the intake air amount detector based on at least the atmospheric pressure detected by the atmospheric pressure detector; a first filter configured to filter a signal representing the air-fuel ratio detected by the air-fuel ratio detector using a first bandpass filter so that a 0.5th-order frequency component of engine speed of the internal-combustion engine is extracted from the signal; a first integrator configured to accumulate a filtered signal filtered by the first filter for a predetermined first period of time to compute a first integration value; a corrector configured to correct the first integration value in accordance with the exhaust flow rate calculated by the exhaust flow rate calculator to compute a corrected first integration value each time the first integration value is computed by the first integrator; and a first determination section configured to determine that cylinder-to-cylinder air-fuel ratio imbalance occurs in the plurality of cylinders if the corrected first integration value is greater than a predetermined first threshold value after the predetermined first period of time has elapsed.