| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of suppressing coat peeling from a selective reduction type catalyst.SOLUTION: A urea vaporization period ureaintf is set as an addition interval, and a value obtained by subtracting a urea arrival time ureaintb from the urea vaporization period ureaintf is set as an upper limit value ureaints for a single urea addition period. On that basis, the single urea addition period is calculated to satisfy a urea addition amount required value. Herein, the urea arrival time ureaintb is a time required for urea injected by a reductant addition valve to arrive at a SCR, and the urea vaporization period ureaintf is set to be a value which is greater as the temperature of the SCR is lower. On that account, as the temperature of the SCR is lower, the addition interval and the upper limit value ureaints are set to be values which are greater.SELECTED DRAWING: Figure 6 |
