Patent ID: 7040086
Filing Date: 2006-05-09
Classification: F02D

Abstract:
1. In an internal combustion engine system comprising an exhaust purifying device arranged in an exhaust gas passage extending from the engine, the exhaust purifying device including a NOx trapping catalyst that traps NOx in the exhaust gas when an exhaust air/fuel ratio is leaner than stoichiometric and releases the trapped NOx therefrom when the exhaust air/fuel ratio is richer than stoichiometric, and a particulate filter that collects a particulate matter in the exhaust gas; a condition detecting device that detects an amount of the particulate matter that would be deposited on the particulate filter; and an exhaust air/fuel ratio control device that controls the exhaust gas from the engine in such a manner that the exhaust gas has a target exhaust air/fuel ratio, a method for controlling the exhaust air/fuel ratio control device comprising: starting to increase the temperature of the particulate filter for burning the particulate matter in the filter when the amount of the deposited particulate matter detected by the condition detecting device reaches a predetermined amount; and varying the exhaust air/fuel ratio under the leaner air/fuel ratio exhaust condition in accordance with the detected amount of the deposited particulate matter upon sensing a change of the exhaust air/fuel ratio from a stoichiometric or richer side to a leaner side and sensing an excess of the detected amount of the deposited particulate matter over a predetermined lower limit.