Patent ID: 6854265

Claim:
A method for regenerating a filter provided in an exhaust pipe of an internal combustion engine, wherein particulate material is collected in the filter and incombustible impurity is contained in the collected particulate material, the method comprising steps of: detecting a first parameter whose value is correlative with and detectable an amount of the collected particulate material; detecting a second parameter whose value is correlative with and detectable of an amount of the incombustible impurity contained in the collected particulate material; and burning the collected particulate material through a partial regenerating process in which, unless the second parameter meets a predetermined condition, a burn of the collected particulate material starts, when the value of the first parameter exceeds a first threshold, and terminates, when the value of the first parameter falls below a second threshold that is smaller than the first threshold, whereby a part of the collected particulate material is burnt to an extent that the incombustible impurity can not easily pass through the filter.