Patent ID: 8020375

Claim:
An exhaust gas purification system for an internal combustion engine, comprising: an exhaust gas purification apparatus provided in an exhaust passage of an internal combustion engine and including a catalyst having an oxidizing function; a fuel injection valve that injects fuel directly into a cylinder of said internal combustion engine; a fuel addition valve that adds fuel into exhaust gas, said fuel addition valve being provided in said exhaust passage upstream of said exhaust gas purification apparatus; target fuel supply quantity calculation unit for calculating a target fuel supply quantity defined as the quantity of fuel that is required to be supplied to said exhaust gas purification apparatus to recover performance of said exhaust gas purification apparatus; upper limit value setting unit for setting an upper limit value of the fuel addition quantity in a case where fuel addition by said fuel addition valve is performed at a time when the intake air quantity of said internal combustion engine is increasing, wherein in a case where the performance of said exhaust gas purification apparatus is to be recovered at a time when the intake air quantity of said internal combustion engine is increasing, if the target fuel supply quantity calculated by said target fuel supply quantity calculation unit is larger than the upper limit value set by said upper limit value setting unit, a quantity of fuel equal to said upper limit value is added by said fuel addition valve, and a quantity of fuel equal to the shortfall of fuel supply is injected by performing sub fuel injection by said fuel injection valve at a time after main fuel injection and at which injected fuel is discharged from said cylinder.