| 摘要 |
PROBLEM TO BE SOLVED: To supply required HC even in a fuel-cut region at deceleration time, by correctly grasping an HC amount required for NOx reduction catalyst. SOLUTION: In an exhaust passage 52 of an engine 51, an HC adsorbing material 53 and NOx reduction catalyst 54 are disposed from the upstream side of the exhaust passage 52 in this order. While an adsorbing material temperature sensor 55 detects a temperature of the HC adsorbing material 53, an HC generation amount and a NOx generation amount are calculated based on an operational condition of the engine 51. Based on the HC generation amount and the temperature of the HC adsorbing material 53, an inflow rate of HC flowing into NOx reduction catalyst 54 is calculated, and based on a ratio of the NOx generation amount to HC inflow amount (HC/NOx), the determination is made whether or not an HC amount required for reduction of NOx by the NOx reduction catalyst 54 is short. When it is determined that the HC amount is short, a little amount of fuel is injected from a fuel injection valve 1 even in a fuel-cut region at deceleration time. |
