Patent ID: 8209954
Filing Date: 2012-07-03
Classification: B01D,F01N,F02D,Y02A,Y02T

Abstract:
1. An exhaust purification device of an internal combustion engine, the exhaust purification device comprising: an NOx storing catalyst disposed in an engine exhaust passage and which stores NOx contained in exhaust gas when an air-fuel ratio of an inflowing exhaust gas is lean and releases stored NOx when the air-fuel ratio of the inflowing exhaust gas is a stoichiometric air-fuel ratio or rich; an NOx selective reducing catalyst disposed in the engine exhaust passage downstream of the NOx storing catalyst, the NOx selective reducing catalyst able to selectively reduce NOx in the exhaust gas with adsorbed ammonia; and an electronic control unit configured to control the air-fuel ratio of the exhaust gas flowing into the NOx storing catalyst to be temporarily switched from lean to rich to release NOx from the NOx storing catalyst, the electronic control unit configured to calculate an amount of NOx passing straight through the NOx storing catalyst under a lean air-fuel ratio of the exhaust gas, and when a calculated NOx amount reaches a predetermined threshold sufficient to remove a predetermined amount of ammonia adsorbed on the NOx selective reducing catalyst, the electronic control unit temporarily switches the air-fuel ratio of the exhaust gas from lean to rich, wherein the electronic control unit is configured to perform an ammonia removal control by which ammonia adsorbed on the NOx selective reducing catalyst is removed from the NOx selective reducing catalyst by feeding the predetermined threshold amount of NOx before the air-fuel ratio of the exhaust gas flowing into the NOx storing catalyst is temporarily switched from lean to rich.