To restore a catalyst from the poisoned state as well as to prevent an NOx catalyst for processing exhaust gas of a diesel engine from being poisoned by sticking of HC(hydrocarbon).
In case of an engine mounted in a vehicle, since the temperature of exhaust gas is lowered when the engine is in the decelerating state, HC to be added to exhaust gas on the upstream side of a catalyst for processing NOx is easily stacked on the catalyst. When a judging means detects (S202) the poisoned state when an estimated value QHC of the HC sticking amount becomes the specified value or more, and also when it detects (S204) the decelerating state, an intake throttle valve is full closed, and an EGR valve is full opened (S205) Therefore, the temperature drop of exhaust gas and the catalyst is prevented. Moreover, since the temperature of the catalyst is raised by the oxidation action generated by separation of HC stuck to the catalyst, the catalyst can be prevented from being poisoned caused by sticking of HC even in the decelerating state.
HIROTA SHINYA
IWASAKI EIJI
TOYOTA MOTOR CORP
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