Patent ID: 7146804

Claim:
An exhaust gas cleaning system of an internal combustion engine, the system comprising: a particulate filter disposed in an exhaust pipe of the engine for collecting particulate matters included in exhaust gas; operating state detecting means for detecting an operating state of the engine; regenerating means for regenerating the particulate filter; and regeneration controlling means for controlling the regeneration, the regeneration controlling means including collecting state determining means, regeneration suitability determining means and regeneration performing means, wherein; the collecting state determining means determines whether a collecting state parameter, which increases as a quantity of the collected particulate matters increases, is equal to or greater than a first threshold or a second threshold, which is greater than the first threshold, the regeneration suitability determining means determines whether the detected operating state is in a suitable area for the regeneration, in which high regenerating efficiency of the particulate filter is provided, the regeneration suitability determining means determining that the detected operating state is in the suitable area when an air intake amount is less than a predetermined value and temperature of the particulate filter is higher than a certain value, and the regeneration performing means performs the regeneration of the particulate filter with the regenerating means only when the detected operating state is in the suitable area in the case in which the collecting state parameter is equal to or greater than the first threshold and is less than the second threshold, and performs the regeneration when the collecting state parameter is equal to or greater than the second threshold regardless of the result of the determination performed by the regeneration suitability determining means.