Patent ID: 7395661

Claim:
A soot accumulation amount estimation method for an exhaust gas purification filter, comprising: a first step of burning soot collected in pores of the exhaust gas purification filter to regenerate the filter; a second step of detecting a temperature of exhaust gas flowing into the filter, to judge whether or not the exhaust gas temperature is equal to or lower than a predetermined temperature at which a soot amount flowing into the filter is substantially equal to a soot amount to be burnt in the filter; a third step of adding up a period of time during which the exhaust gas temperature is equal to or lower than the predetermined temperature, when the exhaust gas temperature is equal to or lower than the predetermined temperature; a fourth step of judging whether or not the added up period of time is equal to or longer than a period of time during which a predetermined amount of soot is accumulated in the pores after the first step; and a fifth step of estimating a soot accumulation amount of the filter based on a pressure loss through the filter, when the added up period of time is equal to or longer than the period of time during which the predetermined amount of soot is accumulated.