Page 307 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Toyota Motor Co. Ltd. 289

4) determining a failure of the EHC converter system when a difference between the values of
the detected parameters of the two EHC converters exceeds a predetermined value
5) determining which of the EHC converters has failed when it is determined that the catalytic
converter system has failed

TEMPERATURE

ACTIVATING
TEMPERATURE

Fig. 130 (from U3.5447696)

Fig. 130 shows an embodiment of this method. When the engine starts, the exhaust gas
temperature starts to increase. The heating of the heater converter also starts to increase and
the difference between the exhaust gas temperature and the temperature of the heater
converter is maintained relatively small. After an appropriate time, the temperature of the
heater-converter reaches the activating temperature of the catalyst, then the temperature of the
heater-converter increases rapidly and becomes higher than the exhaust gas temperature.
Therefore, if the temperature of the heater converter is lower than the exhaust gas temperature
by more than a predetermined value even afler the heater is ON, it can be considered that the
converter system has failed.

The method described in patent application W09636863 (1996) concerns a durability test of a
catalytic converter. A relationship between the catalyst bed temperature and deterioration rate
of the catalyst is formed. The durability test takes place at a bed temperature higher than the