Page 284 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

266 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

catalytic converter catalytic converter
/

.hole
aligned with h lole

Fig. 1 17 (from DE4 I 0024 1 )

In the method of DE4100397 (1992) the following steps are considered:
I) heating up the catalytic converter to its activation temperature
2) suppressing at least one ignition during a deceleration phase of operation of the engine,
causing a defined amount of unburned aidfuel mixture to be supplied to the catalytic
converter
3) measuring the temperature of the exhaust gases upstream (first sensor) and downstream of
the catalytic converter (second sensor)
4) forming the difference of the two temperatures and judging that the catalytic converter is
deteriorated when the difference is lower than a certain value.

In an alternative embodiment the second sensor is installed inside the catalyst matrix and the
unburned fuel is injected directly in the exhaust pipe by means of a fuel injector.

The method of DE4122787 (1992) comprises the following steps:
1) measuring the temperature of the exhaust gases upstream of the catalytic converter by
means of a first temperature sensor
2) measuring the quantity of the exhaust gases flowing through the catalytic converter
3) calculating a temperature value of the exhaust gases downstream of the catalytic converter
by making use of the measured upstream temperature of the exhaust gases, the exhaust
gases flow rate through the catalytic converter, the geometry and the thermal capacity of
the catalytic converter
4) measuring the temperature of the exhaust gases downstream of the catalytic converter by
means of a temperature sensor