Patent ID: 6449944
Filing Date: 2002-09-17
Classification: F01N,F02D,Y02T

Abstract:
A method of evaluating a deteriorated state of a catalytic converter for purifying an exhaust gas produced when an air-fuel mixture is combusted, comprising the steps of:supplying the exhaust gas downstream to an exhaust passage which has a first exhaust gas sensor and a second exhaust gas sensor that are disposed respectively upstream and downstream of the catalytic converter, for generating respective outputs depending on components of the exhaust gas; detecting data of the outputs of said first exhaust gas sensor and said second exhaust gas sensor when the exhaust gas is supplied to said exhaust passage; identifying the value of at least one parameter to be set of a model that is constructed as representing a behavior of an object exhaust system which ranges from said first exhaust gas sensor to said second exhaust gas sensor and includes said catalytic converter in said exhaust passage, based on the detected data of the outputs of said first exhaust gas sensor and said second exhaust gas sensor; and determining a deteriorated state of said catalytic converter based on data of the identified value of said parameter; wherein said model comprises a model expressing said object exhaust system for generating the output of said second exhaust gas sensor from the output of said first exhaust gas sensor via at least one of a response delay element and a dead time element, and includes, as said parameter, at least one of a coefficient relative to the output of said first exhaust gas sensor and a coefficient relative to the output of said second exhaust gas sensor.