Page 189 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Siemens Automotive SA - Siemens AG 171

level. The catalytic converter is capable of absorbing the minimum of
the quantity of oxygen stored defining a non-deteriorated catalytic
converter provided that in a subsequent validating time interval At?,
the output signal Vo2 of the downstream sensor switches clearly from
one level to the other following a new offset still in the same
direction. The value frhl of the base injection time is taken now as
center of the forced deviation of the opening time I, (fig. 77b).
The amplitude of this deviation remains the same throughout all time intervals At
Concluding, during progressive and monotonically modified evolution of the base injection
time used during successive time intervals Ai,, AI2,..,d/,,, a catalytic converter is considered as
non-deteriorated when the output signal of the downstream sensor switches clearly from one
level to another, whereas a catalytic converter is considered as deteriorated when at an
intermediate time interval e.g. dl2 the output signal of the downstream sensor oscillates.

A procedure is also presented for indirectly detecting the limits Q,,,," and &,,, and for
calculating the base injection time to be used in this method.

upstream
02 sensor
voltage II !i min

Q ")
02 quantity . max
stored in
catalyst
min 1 $ ji li j/ i
i I! II I: I!
downstream
02 sensor
voltage
time

Fig. 77 (from W09309335)