| abstract |
PROBLEM TO BE SOLVED: To effectively perform NOx purification during lean operation without deteriorating drivability, with regard to an exhaust gas purification device for a lean combustion internal combustion engine. SOLUTION: When an exhaust system of a lean combustion internal combustion engine is operated in a lean combustion state, the NOx purification efficiency decreases with the passage of time, but the operation state is switched to a stoichiometric air fuel ratio or an operating state at a richer air fuel ratio than the stoichiometric air fuel ratio. And an NOx purification member having such characteristics that the NOx purification efficiency is restored, an air-fuel ratio control means for switching a mixing ratio of fuel air supplied to the internal combustion engine, and an output by reducing the amount of intake air to the internal combustion engine Output reduction means for reducing the output of the internal combustion engine during lean combustion operation, and temporarily switching to the stoichiometric state or rich state without changing the output of the internal combustion engine, and gradually switching the engine. Control means 25 is provided. [Selection] Figure 1 |