Patent ID: 8109080
Filing Date: 2012-02-07
Classification: B01D,F01N,Y02A,Y02T

Abstract:
1. A method of controlling a NOx purification system provided with a NOx occlusion reduction catalyst disposed in an exhaust passage of an internal combustion engine, which occludes NOx when an air/fuel ratio of an exhaust gas is in a lean state, and releases and reduces the occluded NOx when the air/fuel ratio is in a rich state, the method comprising the steps of: executing a NOx regeneration control for bringing the air/fuel ratio of the exhaust gas into a rich state in order to recover a NOx occlusion capacity of the NOx occlusion reduction catalyst; and executing a sulfur poisoning regeneration control for bringing the air/fuel ratio of the exhaust gas into a rich state in order to recover the deterioration of the NOx occlusion reduction catalyst caused by sulfur poisoning; disposing an oxygen concentration sensor and a reducing agent concentration sensor downstream of said NOx occlusion reduction catalyst; and determining a level of the deterioration of said NOx occlusion reduction catalyst caused by the sulfur poisoning based on a time between a time point at which said oxygen concentration sensor detects a marked decrease in the oxygen concentration and a time point at which said reducing agent concentration sensor detects a marked increase in the concentration of the reducing agent, upon execution of said NOx regeneration control.