Page 279 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Robert Bosch GmbH 26 1

1) operating the engine under such conditions that the temperature of the catalytic converter
is lower than the activation temperature of a new converter
2) measuring the time interval At to reach a predetermined temperature, which is higher than
the activation temperature of a new catalytic converter
3) comparing the measured time interval At with a predetermined value At0
4) determining that the catalytic converter is hnctional when the measured time interval At is
smaller than the predetermined value At0

The third embodiment comprises the following steps:
1) operating the engine under such conditions that the temperature of the catalytic converter is
lower than the activation temperature of a new converter
2) calculating the temperature Tt, of the catalytic converter by means of a theoretical model.
Actual values of operating parameters of the engine and the converter are given to the
theoretical model in order to calculate the temperature T,,
3) checking the actual temperature T of the catalytic converter when the calculated
temperature T,,,, reaches a predetermined value To, which lies above the activation
temperature of a new catalytic converter
4) determining that the catalytic converter is hnctional when the actual temperature T of the
catalytic converter is greater than the predetermined value TO

not deteriorated (new)
not deteriorated
(new)
900

very
very deteriorated
deteriorated

0 5 5 t (min)
(min)
t
0
Fig. 1 I4 (from DE42 1 1092)

The method of DE4330997 (1995) monitors the behavior of a catalytic converter during
startup of the engine and comprises the following steps:
1) determining a temperature T,, of the activation region of the catalytic converter. This
activation region represents the region of the catalytic converter which in principle treats the