Patent ID: 6502388
Filing Date: 2003-01-07
Classification: F01N,F02D,Y02T

Abstract:
An engine exhaust gas cleaning system, comprising:an NOx trapping agent arranged inside an exhaust gas passage of an engine, said NOx trapping agent trapping by absorbing or adsorbing NOx in an exhaust gas when an air-fuel ratio of the exhaust gas flowing thereinto is a lean air-fuel ratio, purging by at least one of releasing and reducing the trapped NOx when a concentration of oxygen in the exhaust gas is reduced; an air-fuel ratio changing means for temporarily changing the air-fuel ratio of the exhaust gas from a lean air-fuel ratio to a stoichiometric air-fuel ratio or a rich air-fuel ratio with a preset period; a concentration detecting means for detecting a concentration of a specified component in the exhaust gas at a position downstream of said NOx trapping agent in the exhaust gas passage; an operating control parameter changing means for changing operating control parameters of said engine in order to change an amount of NOx trapped to said NOx trapping agent with the lean air-fuel ratio; and an NOx trapping amount change detecting means for detecting change in the amount of NOx trapped to said NOx trapping agent based on change in detected results of said concentration detecting means at the time of said air-fuel ratio changing means temporarily changing the air-fuel ratio of the exhaust gas to the stoichiometric air-fuel ratio or the rich air-fuel ratio when said operating control parameter changing means changes the operating control parameters to change the amount of trapped NOx.