EXHAUST PURIFICATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

An exhaust purification device for an internal combustion engine is provided with an exhaust purification catalyst which contains an upstream catalyst and a downstream catalyst, and which reacts NOx with hydrocarbons. The upstream catalyst is capable of oxidation. In the downstream catalyst, precious metal catalyst particles are held on an exhaust circulation surface, and a basic exhaust circulation surface part is formed. The exhaust purification catalyst purifies NOx by fluctuating the concentration of hydrocarbons at a magnitude of fluctuation in a predetermined range and in a cycle in a predetermined range. The upstream catalyst has a high-efficiency temperature in which it is possible to partially oxide the hydrocarbons at a predetermined efficiency. The exhaust purification device controls the temperature of the upstream catalyst such that the temperature of the upstream catalyst is below the high-efficiency temperature while the hydrocarbon is being supplied and such that the temperature of the upstream catalyst is equal to or greater than the high-efficiency temperature after the hydrocarbons are supplied.