Page 280 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

262 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

exhaust gases pollutants during heating up of the catalytic converter. The activation region
can be an auxiliary light-off catalytic converter located upstream of a main catalytic
converter, or it can be the front upstream part of the catalytic converter when no auxiliary
light-off catalytic converter exists
2 ) feeding the catalytic converter with an aidfuel mixture
3 1 determining the startup behavior of the catalytic converter depending on the influence that
the feeding of the aidfuel mixture has on the temperature T,,, of the startup activation
region. This is achieved by comparing
a) the difference of temperature T,, of the activation region from a
reference value T,f with a predetermined value and/or
b) the first and/or the second derivative in time of Teat with predetermined
values.
As T,f one of the following can be chosen:
a) the temperature T,,, when no conversion of air/fuel mixture takes place
in the startup activation region, or
b) the temperature T,,, just before feeding the ak/fbel mixture to the
catalytic converter, or
c) the temperature of the exhaust gases before they enter in the catalytic
converter

'cat

new catalytic converter

I \ medium deteriorated

Tstad

I tl time

Fig. 1 15 (from DE4330997)