Patent ID: 7607295

Claim:
A particulate accumulation amount estimating method comprising: detecting a pressure difference across a particulate filter that is configured and arranged to capture particulate matter contained in exhaust gas discharged from an engine; estimating an ash accumulation amount of ash accumulated in the particulate filter; determining a change in an effective area of the particulate filter resulting from the ash accumulated in the particulate filter based on the estimated value of the ash accumulation amount; determining a pressure loss rate corresponding to a change in the effective area; determining an accumulated ash portion of the pressure difference that was detected due to the accumulated ash based on the estimated value of the ash accumulation amount; estimating a particulate accumulation amount of particulate matter accumulated in the particulate filter based on an amended pressure difference and the effective area change that was determined, the amended pressure difference resulting from amending the pressure difference based on the pressure loss rate; and calculating an accumulated particulate matter portion of the detected pressure difference due to the accumulated particulate matter by subtracting the accumulated ash portion of the detected pressure difference resulting from the accumulated ash from the amended pressure difference.