| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technique capable of clogging prevention of control considering easiness of clogging of injection holes of respective injection valves, in an exhaust emission control system for an internal combustion engine performing the clogging prevention control to suppress clogging of the injection holes by injecting a reducing agent from the plurality of reducing agent injection valves. <P>SOLUTION: The exhaust emission control system is provided with an NSR 3 provided in an exhaust pipe 2 of the engine 1, an SCR 4 provided in an exhaust pipe 2 on the downstream side from the NSR 3, an upstream injection valve 11 for injecting a reducing agent from an injection hole 34 placed upstream from the NSR 3 and facing inside of the exhaust pipe 2, and a downstream injection valve 21 for injecting a reducing agent from an injection hole 44 placed between the NSR 3 and the SCR 4 and facing inside of the exhaust pipe 2; and controls the clogging prevention. Injection amount of the reducing agent related to the clogging prevention control of each injection valve is adjusted so that total injection amount of the reducing agent injected from the upstream side injection valve 11 for a reference period Δtm becomes larger than that from the downstream side injection valve 21. <P>COPYRIGHT: (C)2009,JPO&INPIT |
