| 摘要 |
PROBLEM TO BE SOLVED: To provide a PM accumulation quantity estimation device that can prevent an excessively accumulated state when an operating state where PM accumulation quantity cannot be estimated from a pressure difference between before and after a filter is continued and that can prevent overheating of a filter unit, etc., and an exhaust emission control system for an internal combustion engine.SOLUTION: A PM accumulation quantity estimation device is used for estimating PM accumulation quantity by selectively adopting first estimation processing and second estimation processing. In the first estimation processing, a DPF pressure difference value dp1 corresponding to the PM accumulation quantity and first PM accumulation quantity pmdp are calculated based on a detected pressure difference obtained by a differential pressure sensor. In the second estimation processing, second PM accumulation quantity pmdp and a DPF pressure difference value dp2 corresponding to the second PM accumulation quantity pmdp are calculated based on an engine operating condition, whether or not differential pressure use permitting frequency dpfrq that is adoption frequency of the first estimation processing is a predetermined value thf or lower is determined, and when the frequency dpfrq is lowered to the predetermined value thf or less, increase correction of the second PM accumulation quantity pmdp is performed. |
