Page 260 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

242 Methods for Monitoring and Diagnosing the Efficiency of Catalytic Converters

In patent application DE4027207 (1992) two methods are presented. The first one, also
described in US5339628 (1995). comprises the following steps:
1) measuring the temperature at least at two locations by temperature measuring sensors of
which at least one is disposed in the catalytic converter and which sensors are spaced apart
in flow direction
2) periodically repeatedly determining a temperature measuring variable from signals issued by
the sensors during operation of the engine with an engine monitoring system
3) averaging the temperature measuring variable over a sufficiently long period of engine
operation to form a mean temperature value which is substantially unaffected by short-term
load conditions e.g. forming mean temperature by integrating the temperature measuring
variable over an observation period or by executing the following process:
a) observing the temperature measuring variable over a given period of time
b) periodically determining the temperature measuring variable at time intervals
being substantially shorter than the given observation period and recording the
temperature measuring variable in a memory of a multiple channel analyzer
belonging to the engine monitoring system
c) forming the mean temperature value from the contents of the memory, after the
observation period has elapsed
d) erasing the memory
4) comparing the mean temperature value with a predetermined limit value
5) indicating if a mean temperature value does not correspond to the limit value and
ascertaining a catalytic activity of the catalytic converter.

I Vemp.

sensor
sensor 1 1 I

sensor I

,,et 21” jacket surface
I
2

catalytic converter

Fig. 103 (from DE4027207)