METHOD OF JUDGING DETERIORATION OF EMISSION GAS CONTROL CATALYST DEVICE

摘要

A behavior of an exhaust system (E) is implemented by modeling the exhaust system (E) containing a catalyst device (3), a first emission gas sensor (5) (air/fuel ratio sensor) on the upstream side of the catalyst device (3) and a second emission gas sensor (6) (O2 sensor) on the downstream side thereof. During the operation of an internal combustion engine (1), parameters to be set for a model of the exhaust system (E) are sequentially identified based on output data from the emission gas sensors (5, 6) and the deterioration condition of the catalyst device (3) is judged based on the identified value data. In addition, in parallel with the deterioration condition judging, a target air/fuel ratio of the internal combustion engine (1) is sequentially determined so as to converge an output from the emission gas sensor (5) to a preset target value and an air/fuel ratio of the engine (1) is controlled so as to converge an output (air/fuel ratio detection value) from the first emission gas sensor (5) to the target air/fuel ratio to thereby ensure an optimum purifying performance of the catalyst device (3), whereby it is possible to judge the deterioration conditions of the catalyst device (3) in various operating conditions of the internal combustion engine (1).