Patent ID: 8117833

Claim:
A method of controlling a system having an internal combustion engine, a filter arranged in an exhaust passage, which traps particulate matter contained in exhaust gas from said internal combustion engine, a reduction catalyst arranged in said exhaust passage downstream of said filter and which reduces nitrate oxide contained in the exhaust gas with reductant supplied thereto, the method comprising: in a first mode, combusting a first amount of particulate matter trapped in said filter and supplying a first amount of reductant to said reduction catalyst when an amount of particulate matter trapped in said filter is less than a predetermined trapping amount; and in a second mode, combusting a second amount of particulate matter trapped in said filter that is greater than said first amount of particulate matter and supplying a second amount of reductant that is greater than said first amount to said reduction catalyst when an amount of particulate matter trapped in said filter is equal to or greater than said predetermined trapping amount, wherein said internal combustion engine has a fuel injector which injects fuel directly into a combustion chamber, and the method further comprising: in said first mode, supplying fuel from said fuel injector to said combustion chamber so that an end of the fuel injection during a cylinder cycle is a first timing during a cylinder cycle and recirculating a first amount of exhaust gas from said exhaust passage upstream of said filter to an intake passage of said internal combustion engine; and in said second mode, supplying fuel from said fuel injector to said combustion chamber so that an end of the fuel injection during a cylinder cycle is a second timing that is later than said first timing during a cylinder cycle and recirculating a second amount of exhaust gas that is less than said first amount of exhaust gas from said exhaust passage upstream of said filter to said intake passage.