| 摘要 |
An exhaust valve early-closure control brings about blowback of exhaust gas into an intake system. However, if the exhaust valve early-closure control is executed, for example, during a first idle operation immediately following the startup of the engine, or the like, the amount of blowback exhaust gas becomes excessively large. Therefore, when the post-startup increase amount has decreased to or below a lower-limit criterion value, the ECU prohibits the exhaust valve early-closure control, and changes the control to a usual valve timing control. As a result, during a period during which the combustion state has a stability margin and the amount of emission of HCs and the like is large, the exhaust emission quality can be bettered by the exhaust valve early-closure control. Besides, when the post-startup increase amount has decreased, the combustion state can be stabilized by prohibiting the exhaust valve early-closure control. |
