Patent ID: 8307638

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; a precatalyst having oxidizing ability provided in the exhaust passage upstream of the exhaust gas purification apparatus; reducing agent supply apparatus for supplying reducing agent to the precatalyst; at least one controller configured to: execute a recovery control in which the reducing agent is supplied to the precatalyst by the reducing agent supply apparatus to thereby raise the temperature of the exhaust gas purification apparatus, whereby a capability of the exhaust gas purification apparatus is recovered; detect a degree of deterioration of the precatalyst; and set a recovery control prohibition range that is an operation range of the internal combustion engine in which execution of the recovery control by the at least one controller is prohibited, based on the degree of deterioration of the precatalyst detected by the at least one controller, wherein the higher the degree of deterioration of the precatalyst is, the higher the maximum values of the engine torque and the engine revolution number in the recovery control prohibition range set by the at least one controller are.