| 摘要 |
When the engine is cold, fuel attachment on piston is increased due to low fuel temperature, whereby PM is increased. While the fuel attachment can be decreased by promoting vaporization by injecting fuel in a period after the exhaust valve is closed and before the intake valve is opened, exhaust and fuel economy may be degraded by an increase in residual gas if an increase of the fuel injection period is addressed solely by advancing the angle of the exhaust valve. Under the cold condition of a cylinder direct injection engine, the period between the exhaust valve closing timing and the intake valve opening timing is designated as a fuel injection-enabled period. The fuel injection period is set such that all or most of the fuel can be injected in the fuel injection-enabled period. When the amount of advance of the exhaust valve from a reference position is α [deg], the amount of retardation of the intake valve is &bgr; [deg], and the amount of increase of the fuel injection period is γ [deg] with reference to the exhaust valve closing timing, the intake valve opening timing, and the fuel injection period under the condition that the fuel injection period is minimized, the intake and exhaust valves are controlled such that α + &bgr; is also increased as γ is increased, where &bgr; > α under the condition that γ as an applicable range upper limit is maximized. |
