Exhaust gas purifying apparatus of lean-burn internal combustion engine

摘要

An exhaust gas purifying apparatus of a lean-burn internal combustion engine surely purifies nitrogen oxide occluded by a nitrogen oxide occluding/reducing catalyst without making a combustion of an air-fuel mixture unstable while utilizing a vapor fuel generated in a fuel tank. The exhaust gas purifying apparatus includes a gas state judging unit for judging a state of a vapor fuel gas supplied to an intake system of the lean-burn internal combustion engine, and an exhaust state control unit for setting, to a desired state, a state of the exhaust gas flowing to the nitrogen oxide occluding/reducing catalyst by selectively controlling the fuel injection valve and the gas supply unit in accordance with a state of the vapor fuel gas at the time when the nitrogen oxide occluded by the nitrogen oxide occluding/reducing catalyst provided in an exhaust system of the lean-burn internal combustion engine should be desorbed and purified.