Patent ID: 7013638

Claim:
An exhaust gas purifying system comprising: an oxidation catalyst disposed in an exhaust passage of an engine; a filter disposed in said exhaust passage at a position downstream of said oxidation catalyst to collect a particulate matter contained in exhaust gas; a first additional fuel control means which injects a first additional fuel into a cylinder during a forced regeneration of said filter and after a main fuel injection in said engine; a second additional fuel control means which supplies a second additional fuel to said oxidation catalyst after a rise in temperature of said oxidation catalyst up to an activation temperature of the catalyst and after the injection of said first additional fuel; a temperature detecting means for detecting an outlet temperature of said oxidation catalyst; an engine speed detecting means for detecting an engine speed of said engine; a load detecting means for detecting a load of said engine; and a second additional fuel supply quantity setting means which sets a supply quantity of said second additional fuel in accordance with information provided from said revolution detecting means and said load detecting means and which changes the second additional fuel supply quantity in accordance with information provided from said temperature detecting means, wherein said second additional fuel supply quantity setting means provides first and second additional fuel quantity setting values, the second additional fuel quantity setting value being smaller than the first additional fuel quantity setting value, and wherein the second additional fuel supply quantity setting means applies the first additional fuel quantity setting value when the oxidation catalyst outlet temperature is lower than a predetermined value, and applies the second additional fuel quantity setting value when the oxidation catalyst outlet temperature is at or greater than the predetermined value.