Exhaust gas purifying apparatus of engine

摘要

An exhaust gas purifying apparatus (A) has a catalyst (25) of lean NOx type disposed in an exhaust passage (22) of an engine (1). The catalyst (25) absorbs NOx and SOx when the oxygen concentration in exhaust gas is higher, while it releases NOx when the oxygen concentration is lowered. If it is judged that sulfur poisoning is caused in the catalyst (25) in accordance with the history of working of the engine (1) and so on, and if the temperature of the catalyst (25) is high, the fuel injection quantity is corrected by feedback control in accordance with the signals from an O2 sensor (24) so that the air fuel ratio nearly coincides with the theoretical air fuel ratio. Further, the fuel to be injected is divided into two parts, and then the two parts are injected during the intake and compression strokes at every cylinder, respectively. Similarly, when NOx is released from the catalyst (25) also, the feedback control of the fuel injection quantity and the divisional fuel injection are performed. Hereupon, the catalyst (25) of two layer type has an outer catalytic layer (25c) supporting zeolite.