| 摘要 |
PROBLEM TO BE SOLVED: To provide a system and a method for purifying exhaust gas of an internal combustion engine capable of reducing NOx discharged from the internal combustion engine when a generation amount of the NOx is temporarily increased because a vehicle is accelerated from normal travel in a low-speed and low-load operation state with a low exhaust gas temperature.SOLUTION: A system for purifying exhaust gas of an internal combustion engine has, in an order from an upstream side on an exhaust passage 15 of the internal combustion engine 10, hydrocarbon supply means 32, an upstream side catalyst unit 31a such as an oxidation catalyst or a NOx reduction catalyst and a particulate collection filter 31b with a catalyst having a hydrocarbon absorption function. When a vehicle mounted with the engine 10 is accelerated after continued travel for a preliminarily set period ta with a temperature Tg1 of the exhaust gas G not more than a preliminarily set exhaust gas temperature T0, the system: starts supply of hydrocarbon to the exhaust gas G when an exhaust gas temperature Tg becomes not less than a preliminarily set first set temperature T1; and stops the supply of the hydrocarbon when a preliminarily set stop condition is met. |
