EXHAUST EMISSION CONTROL DEVICE FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To quickly improve purification characteristics of NOx when the temperature of an oxygen occluded substance in a three-way catalyst is shifted to a predetermined temperature, in an exhaust emission control device for engine in which the three-way catalyst is arranged in an exhaust passage. SOLUTION: This exhaust emission control device comprises: a fuel injection control means 40 for controlling the oxygen concentration of exhaust gas in the upstream of the three-way catalyst 25; and a shift determining means 43 for determining that the temperature of the oxygen occluded substance is shifted to more than the predetermined temperature. An oxygen concentration control means 44 controls the oxygen concentration of the exhaust gas such that oxygen is released from the oxygen occluded substance until a predetermined period is elapsed from a time point in which the shift of the temperature of the oxygen occluded substance of the three-way catalyst 25 to more than the predetermined temperature is determined by the shift determining means 43.