Page 268 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

250 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

The method of DE4308661 (1994) and US5560200 (1996) proceeds as follows:
1) measuring the temperature 7; of the catalytic coating at a certain point of the catalytic
converter by means of a temperature sensor integrated in the structure of the catalytic
converter
2) measuring the temperature TI of the exhaust gases upstream of the catalytic converter
3) forming the time derivatives

dT, dT,
--
dt ’ dt

4) forming the difference

5) specifying the elapsed time ti after the engine start up, at which the difference AV changes
sign
6) measuring the temperature 72 of the catalytic coating at time point ti after the engine start
up, at which the difference A V changes sign
7) determining deterioration of the catalytic converter by comparing the temperature Tz of the
catalytic coating measured at time point ti with predetermined values.
Instead of measuring the temperature directly, one can estimate the exhaust gas temperature
upstream of the catalytic converter from engine operating parameters like: air flow, fuel flow,
speed, engine temperature etc. The data can be stored in a memory device and be processed
later at a workshop.

The method of DE4302779 (1 994) comprises the following steps:
1) operating the internal-combustion engine during a first time period and determining a first
operating condition of the internal-combustion engine via one or more parameters of the
internal-combustion engine and the exhaust gas train.
2) operating the internal-combustion engine during a second time period in the first operating
condition, if at least one of the sensed parameters corresponds to a specified desired value,
or if said at least one of the sensed parameters does not correspond to the specified desired
value. Then the internal-combustion engine is adjusted into a second operating condition by
changing a value of at least one of the sensed parameters of the internal-combustion engine
and, recognizing the second operating condition by comparing the up-to-date parameter