DETERIORATION EVALUATING METHOD OF CATALYST DEVICE FOR EXHAUST EMISSION CONTROL

摘要

PROBLEM TO BE SOLVED: To provide a deterioration evaluating method of a catalyst device for exhaust emission control, capable of properly evaluating the deteriorating condition of the catalyst device in a simple method using an exhaust gas sensor for detecting the concentration of gas components including EC, NOx, etc., to be purified by the exhaust emission control catalyst device. SOLUTION: The property of an output VS of an exhaust gas sensor 5 for the air/fuel ratio of an engine 1 is expressed by a secondary function, and parameters for the secondary function are identified in sequence by a sequential identification algorithm using data for the output VS of the exhaust gas sensor 5 and data for an output KACT of an air/fuel ratio sensor 4 for detecting the air/fuel ratio of the engine 1. Deterioration evaluation parameters having values changed with the deterioration of the catalyst device 3 is found in sequence from the identified values of the parameters for the secondary function and the deteriorating condition of the catalyst device 3 is evaluated in accordance with the deterioration evaluation parameters.