Abstract
The conventional way to diagnose catalyst deterioration in internal combustion engines is to intentionally control the amount of fuel injected under specific operating conditions and determine the delay from the start of catalysis to the
end of catalysis by observing the oxygen concentration signal. Problems with this conventional method include the large size of the catalytic converter, degradation of drivability, degradation of the exhaust gas, obtaining diagnoses
with adequate frequency, lengthened development time, and a large computational load on the engine control computer. These raise a variety of issues in such areas as marketability, government regulations, and development costs.
In this study we applied the MT method, focusing on the fact that the degree of deterioration can be determined by observing the oxygen concentration signal before and after catalysis during normal operation, without controlling the
amount of fuel injected as in the conventional method. As a result, we were able to develop a method that solves all the above problems at once and can be implemented on board the vehicle to obtain a real-time diagnosis.
