Patent ID: 6962046

Claim:
A method of cleaning exhaust gas of an internal combustion engine having a particulate filter, which is disposed in an exhaust passage for collecting exhaust particulate matters included in exhaust gas discharged from cylinders of an engine main body and is regenerated at predetermined timing by eliminating the collected exhaust particulate matters, the method comprising: detecting an operating state of the engine; calculating a collecting state parameter, which increases as a quantity of the collected exhaust particulate matters increases, based on the detected operating state; calculating a detection accuracy determination value as a reference of detection accuracy of the collecting state parameter based on the detected operating state; resetting a regeneration start value so that the regeneration start value is decreased as the detection accuracy decreases, in accordance with the detection accuracy determination value; determining whether the collecting state parameter is greater than the regeneration start value or not; and starting the regeneration of the particulate filter if the collecting state parameter is determined to be greater than the regeneration start value; wherein resetting the regeneration start value includes correcting the regeneration start value by a correction value, which is calculated based on a pre-stored correspondence between the detection accuracy determination value and the correction value, and determining whether the detection accuracy is higher than a threshold detection accuracy or not by comparing the detection accuracy determination value with a threshold value, and for prohibiting the correction of the regeneration start value if the detection accuracy is determined to be higher than the threshold detection accuracy.