Page 226 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

208 Methods for Monitoring and Diagnosing the Etficiency of Catalytic Converters

An engine controller includes a central processing unit CPU, random access memory RAM,
read only memory ROM , and non-volatile random access memory NVRAM. The controller
processes engine control and diagnostic routines, such as through execution of step-by-step
program instructions stored in ROM. The instructions provide for the processing of input
signals indicative of the state of engine operating parameters, and for the generation of control
commands applied to various generally known engine control actuators.

I CONTRaLCR I
air co

mrpressure sensor
coolant temperature

I
catalytic converter

Fig. 92 (from US543101 1)

In the method of US543101 1 (1995) the following steps are considered:
1 ) periodically generating oxygen content signals by sampling an oxygen content of engine
emissions that have passed through the catalytic converter
2) transforming the oxygen content signal into a signal indicating oxygen storage and release
capacity of the catalytic converter by
a) passing the signals through a differentiation process for estimating a rate of
magnitude change between oxygen content signals