Patent ID: 6952919

Claim:
A method of operating an exhaust gas purifying system for an internal combustion engine, the exhaust gas purifying system including a particulate filter disposed in an exhaust gas passageway of the engine to collect particulates in exhaust gas flowing through the exhaust gas passageway, the collected particulates being burnt off to be removed by raising a temperature of exhaust gas in a condition in connection with the particulate filter; and a plurality of devices for raising the temperature of exhaust gas to be introduced into the particulate filter through the exhaust gas passageway when the collected particulates are burned off to be removed, the operating method comprising: selecting at least one of the devices in accordance with an engine operating region; and preferentially operating the selected at least one of the devices to raise the exhaust gas temperature; setting a target exhaust gas temperature when the collected particulates are burned off to be removed; comparing the target exhaust gas temperature with an actual exhaust gas temperature which has been raised by the preferentially operated at least one of the devices; and adding a separate device to be operated for raising the exhaust gas temperature when a degree at which the exhaust gas temperature is raised by the preferentially operated at least one of the devices is lower than a level.