Valve timing control apparatus for engine

A method of controlling a valve timing of an engine, comprising:

• detecting that a first time period has elapsed after a cold-starting of the engine;
• advancing at least one of an opening timing of intake valves and a closing timing of exhaust valves to be earlier than an exhaust top dead center after detecting that the first time period has elapsed, such that valve timing is selectively switched between a first timing in which a minus overlap exists between the closing timing of the exhaust valves and the opening timing of the intake valves prior to an exhaust top dead center, and a second timing in which no overlap exists between the closing timing of the exhaust valves and the opening timing of the intake valves;
• detecting an actual engine speed of the engine;
• setting a target engine speed of the engine determined based on carburetion characteristics of fuel being used for the engine;
• comparing the set target speed of the engine with the detected actual engine speed;
• and
• switching, after the first time period, an advance angle to the first timing when the detected actual engine speed is less than the set target speed.

A valve timing control apparatus for an engine, comprising:

• a variable valve mechanism that varies at least one of an opening timing of intake valves and a closing timing of exhaust valves in the engine, such that valve timing is selectively switched between a first timing in which a minus overlap exists between the closing timing of the exhaust valves and the opening timing of the intake valves prior to an exhaust top dead
• an actual engine speed detecting device that detects an actual engine speed of the engine when the time period has elapsed;
• a target engine speed setting device that sets a target engine speed of the engine based on carburetion characteristics of fuel being used for the engine;
• means for comparing the detected actual engine speed with the set target engine speed, after the predetermined time period has elapsed;
• and
• a timing control device that switches the valve timing to the first timing for the predetermined time period, and, after the predetermined time period, maintains the valve timing at the first timing when the detected actual engine speed is lower than the target engine speed, and switches the valve timing to the second timing when the detected actual engine speed is equal to or greater than the target engine speed.