Page 272 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

254 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

In the method of JP1232106 (1989) and US5060473 (1991) a first temperature sensor is
arranged inside the catalytic converter (fig. 1 IO). The following steps are considered:
1 ) monitoring the temperature of the catalytic converter to produce a temperature indicative
signal. The temperature monitoring takes place by means of the first temperature sensor of
fig. 110 by measuring:
a) a temperature in the vicinity of the upstream side of said catalytic converter, or
b) a temperature at a position in the vicinity of where the temperature of the catalytic
converter becomes maximum when the catalytic converter is in a normal state
2) monitoring engine driving condition for producing an engine driving condition indicative
signal
3) generating a reference value signal representative of a temperature criterion for
determination of a deteriorated catalytic converter, and said reference signal value being
generated on the basis of the engine driving condition indicative signal value
4) comparing the catalytic converter temperature indicative signal value with said reference
value to produce an alarm when the catalytic converter temperature indicative signal value
is smaller than the reference value.

catalyfic converter

sensor sensor

alarm

m
condition
, sensor I

Fig. I IO (from US5060473)