EXHAUST GAS PURIFIER FOR INTERNAL COMBUSTION ENGINE

摘要

An exhaust purification system of an internal combustion engine of the present invention is provided with a selective reduction type NO x catalyst device 1 which can hold ammonia and a storage reduction type NO x catalyst device 3 which is arranged at an upstream side of the selective reduction type NO x catalyst device, which makes an air-fuel ratio of exhaust gas which flows into the storage reduction type NO x catalyst device change from a lean air-fuel ratio to a rich air-fuel ratio for starting an ammonia generation period, and which makes an air-fuel ratio of exhaust gas which flows into the storage reduction type NO x catalyst device change from a rich air-fuel ratio to a lean air-fuel ratio for ending the ammonia generation period. An amount of NO x which is held at the storage reduction type NO x catalyst device for starting the ammonia generation period when a temperature of the storage reduction type NO x catalyst device is less than a set temperature is smaller than that when a temperature of the storage reduction type NO x catalyst device is the set temperature or more.