| 摘要 |
PURPOSE:To enhance the NOx purifying rate of a lean NOx catalyst by providing a fuel injection rate control means for controlling a fuel injection device so that a high injection rate is forcibly obtained so as to increase HC in comparison with the conventional one when it is determined that a drive condition is a middle load condition. CONSTITUTION:There are provided an internal combustion engine 2 which can burn a lean mixture, a lean NOx catalyst 4 provided in an exhaust system of the internal combustion engine 2, a fuel injection device 6 which can change a fuel injection rate, a drive condition detecting means 8, a fuel injection rate control means 10 for controlling the fuel injection device 6 so that a high fuel injection rate is forcibly obtained when the drive condition detected by the drive condition detecting means 8 is a middle load drive condition. With this arrangement, fuel injection is forcibly carried out at a high injection rate in the middle load drive condition in which HC is insufficient during NOx purification of the lean NOx catalyst, thereby it is possible to enhance the NOx purifying rate. |
