Patent ID: 6901746
Filing Date: 2005-06-07
Classification: F01N,F02B,F02D,F02M,Y02T

Abstract:
1. An exhaust gas deNOx apparatus for an engine comprising an NOx adsorber catalyst in an exhaust pipe line of an engine, for adsorbing NOx when an air fuel ratio of an exhaust gas flowing therein is in a lean state and releasing NOx when the air fuel ratio of the exhaust gas flowing therein is in a rich state, the exhaust gas deNOx apparatus comprising: at least one exhaust gas recirculating circuit for mixing the exhaust gas into intake air; a plurality of recirculating circuit adjusting valves being arranged in parallel with said at least one exhaust gas recirculating circuit and operative to independently open and close each one of the adjusting valves; and exhaust gas recirculating amount control means for recirculating a predetermined amount of exhaust gas through said at least one exhaust gas recirculating circuit while maintaining one of said adjusting valves in an open position for reducing NOx when an adsorbed NOx accumulation amount is not more than a predetermined value, and for recirculating more than said predetermined amount of exhaust gas through said at least one exhaust gas recirculating circuit by opening said adjusting valves to the open position to bring the air fuel ratio into a rich state when the adsorbed NOx accumulation amount exceeds the predetermined value and the NOx is to be released.