Method of evaluating deteriorated state of catalytic converter for purifying exhaust gas

摘要

The values of parameters of a model of an object exhaust system including a catalytic converter are identified from the data of outputs from an air-fuel ratio sensor and an O2 sensor which are disposed respectively upstream and downstream of the catalytic converter while an internal combustion engine associated with the catalytic converter is in operation. A deterioration evaluating parameter representing the degree of variation of time-series data of the identified parameters is determined from the time-series data of the identified parameters. The deteriorated state of the catalytic converter is evaluated based on the deterioration evaluating parameter.