EXHAUST GAS PURIFICATION SYSTEM

Provided is an exhaust gas purification system in which control ranging from traveling automatic regeneration to idle automatic regeneration conducted during a stop can be accurately performed, and overshoot of the exhaust gas temperature can be prevented even when a transition is made from the idle automatic regeneration to the traveling automatic regeneration. A DPD 25 for collecting PM in exhaust gas is connected to an exhaust pipe 20 of a diesel engine 10, and when the amount of PM in the DPD 25 becomes equal to or greater than a predetermined amount, the exhaust gas temperature of the diesel engine 10 is increased by performing exhaust pipe injection and the DPD is automatically regenerated. In such an exhaust gas purification system, an exhaust gas temperature during DPD regeneration in automatic regeneration is detected, a difference between the detected exhaust gas temperature and a target regeneration temperature is determined, and in a case where an exhaust pipe injection amount is PID controlled based on the difference, when a transition is made from the traveling automatic regeneration to the idle automatic regeneration conducted during a stop, an integral control term in the PID control is reset to zero to control the exhaust pipe injection amount.