EMISSION CONTROL APPARATUS OF AN INTERNAL COMBUSTION ENGINE AND METHOD FOR DELAYING DETERIORATION OF THE EMISSION CONTROL CATALYST

摘要

In an emission control apparatus of an internal combustion engine in which an emission control catalyst (3) is disposed in an engine exhaust passage (2), if the fuel supply shutdown is performed during an engine deceleration operation when the temperature of the emission control catalyst (3) must be reduced rapidly by a secondary air supply device (7) supplying fresh air to the emission control catalyst ( 3) during the engine deceleration operation, the supply of fresh air from the secondary air supply device (7) intended for the emission control catalyst (3) is started after an execution condition of the fuel supply cutoff is satisfied but before the fuel supply cutout is actually carried out. As a result, the temperature of the catalyst (3) is reduced before the air-fuel ratio of the exhaust gases moves to the lean side due to the execution of the fuel supply cut-off. Thus, exposure of the emission control catalyst (3) to a condition of high temperature deterioration and lean air-fuel ratio is prevented.