| 摘要 |
A control apparatus according to an embodiment of the present invention comprises urea-SCR catalyst 44, a urea-water supply section 46, a low pressure gas recirculating section including a low pressure EGR pipe 61 forming a low pressure EGR passage and a low pressure EGR valve 62, and a control section. The control section controls, based on an engine operating parameter, "an amount of a fuel supplied to the engine, and an opening degree of the low pressure EGR valve." The control section supplies the urea-water to the urea-SCR catalyst in such a manner that ammonia of an amount required for reducing nitrogen oxides contained in an exhaust gas in the urea-SCR catalyst is produced in the urea-SCR catalyst (urea-water for reducing nitrogen oxides supply control). Further, the control section supplies the urea-water to the urea-SCR catalyst, the amount of the urea-water being larger than that of the urea-water for reducing nitrogen oxides supply control when an amount of an acid condensed water produced by a gas passing through the low pressure EGR passage is equal to or larger than an acid condensed water amount threshold (urea-water for producing ammonia supply control). This allows the ammonia flowing out from the urea-SCR catalyst to neutralize the acid condensed water. |
