| 摘要 |
An object of this invention is to appropriately control valve timings based on a fuel property and an engine temperature to improve exhaust emissions. An engine 10 is equipped with a function that drives variable valve mechanisms 36 and 38 to execute intake valve retarded-opening control and exhaust valve early-closing control. An ECU 60 variably sets a low-temperature determination value T1 based on an alcohol concentration in a fuel. If a water temperature Thw of the engine is equal to or less than the low-temperature determination value T1, the ECU 60 prohibits the intake valve retarded-opening control and permits the exhaust valve early-closing control. Consequently, during cold operation it is possible to avoid a deterioration in combustion properties (deterioration in in-cylinder turbulence) caused by intake valve control and thereby suppress a deterioration in exhaust emissions. Further, because exhaust valve control is permitted, for example, a negative overlap period that satisfies a control request can be secured by advancing the closing timing of the exhaust valve 34. Accordingly, exhaust emissions and catalyst warm-up performance can be improved. |
