Patent ID: 6389805
Filing Date: 2002-05-21
Classification: F01N,Y02T

Abstract:
A method for the diagnosis of an exhaust gas purification system in an internal combustion engine, comprising a pre-catalyst (3) and a main catalyst (5) disposed along an exhaust duct (4) of an internal combustion engine (2), first temperature detection means (12) disposed at the input of the pre-catalyst (3) and generating a first temperature signal (VI) representative of an input temperature (TI) of the exhaust gases at the input of the pre-catalyst (3), second temperature detection means (8) disposed at the output of the pre-catalyst (3) and generating a second temperature signal (VO) representative of an output temperature (TO) of the exhaust gases at the output of the pre-catalyst (3), oxygen sensor means, disposed at the input of the pre-catalyst (3) and generating an exhaust gas composition signal (V1), representative of an input oxygen titre (&lgr;I), a control unit (10) receiving as input the first and second temperature signals and the exhaust gas composition signal (V1) and supplying as output an error signal (E), the method comprising the stages of:a) determining a real heat (QR) supplied to the exhaust gases in the pre-catalyst (3) as a function of the input temperature (TI) and output temperature (TO) (130); b) determining a nominal heat (QNOM) corresponding to nominal operating conditions of the pre-catalyst (3)(150); and c) determining an index (I), representative of a state of wear of the pre-catalyst (3), on the basis of a ratio between the real heat (QR) and the nominal heat (QNOM) (160).