INTERNAL COMBUSTION ENGINE EXHAUST PURIFICATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To curb a reduction in NOx purification capacity due to fuel poisoning of a selective reduction NOx catalyst when performing exhaust temperature increase treatment using an oxidation catalyst with fuel supplied to exhaust in an exhaust purification system comprising the selective reduction NOx catalyst and the oxidation catalyst at an upstream side thereof in an exhaust passage.SOLUTION: An exhaust purification system comprises: first fuel supply means which supplies fuel to exhaust flowing in an exhaust passage of an internal combustion engine through a supply valve installed therein; and second fuel supply means which supplies the fuel to the exhaust discharged to the exhaust passage by controlling a fuel injection condition of the internal combustion engine. In a temperature increasing process of a selective reduction NOx catalyst in association with exhaust temperature increase treatment, the exhaust purification system performs at least first control to supply the fuel through the first fuel supply means. In a temperature maintaining process of the selective reduction NOx catalyst in association with the exhaust temperature increase treatment, the exhaust purification system performs at least second control where a ratio of a fuel supply amount through the second fuel supply means to the same through the first supply means is higher than the same in the first control.SELECTED DRAWING: Figure 2