| 摘要 |
PROBLEM TO BE SOLVED: To provide an internal combustion engine exhaust emission control apparatus capable of activating a three-way catalyst at early timing and ensuring reduction purification of NOx adsorbed by a NOx catalyst downstream of the three-way catalyst.SOLUTION: An exhaust emission control apparatus 1 for an engine 2, comprises: a TWC 11 provided in an exhaust pipe 3 of the engine 2 and purifying NOx, HC, and CO contained in exhaust gas; a NOx catalyst 12 provided in the exhaust pipe 3 downstream of the TWC 11, having a carrier comprising zeolite and Pd carried on the carrier, adsorbing the NOx in the exhaust gas, and desorbing and purifying the adsorbed NOx when an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio; and an ECU 4 controlling the air-fuel ratio of the exhaust gas to be lean to activate the TWC 11 at early timing, the TWC 11 and NOx catalyst 12 being set such that until an early-timing activation control over the TWC 11 is completed, a temperature of the NOx catalyst 12 does not reach a NOx desorption start temperature at which the NOx adsorbed by the NOx catalyst 12 starts to be desorbed.SELECTED DRAWING: Figure 1 |
