| 摘要 |
PROBLEM TO BE SOLVED: To detect the occurrence of variation (imbalance) of air-fuel ratios among cylinders in a multiple cylinder internal combustion engine, without providing a temperature sensor in an exhaust gas purification catalyst.SOLUTION: In a multiple cylinder internal combustion engine including a plurality of cylinders; an exhaust gas purification catalyst provided in an exhaust passage; an oxygen concentration sensor provided downstream of the exhaust gas purification catalyst in the exhaust passage; and a control unit controlling electric power supplied to an electric heater heating the oxygen concentration sensor, thereby controlling a temperature of the oxygen concentration sensor to match a predetermined target temperature, it is determined imbalance occurs if a difference between standard electric power supplied to the electric heater determined to correspond to an intake amount of the internal combustion engine and actual electric power supplied to the electric heater is greater than a predetermined threshold.SELECTED DRAWING: Figure 3 |
