Valve timing control apparatus for engine

A valve timing control apparatus for an engine having a combustion chamber for combusting a mixture of fuel mist and air therein, an air intake passage for introducing the air to a combustion chamber and exhaust passage for exhausting gas from the combustion chamber, said passages respectively having an intake valve and an exhaust valve therein, and said intake valve and said exhaust valve being actuated in synchronism with the rotation of a crank shaft of the engine to be alternately opened and closed to regulate introduction of the air to and exhausting of the gas from the combustion chamber and to be simultaneously open during a valve overlap period causing a reverse flow of the air-fuel mixture from the combustion chamber to the air intake passage, wherein the fuel mist adheres to an inner surface of the air intake passage;

• said apparatus comprising:
• adjusting means for adjusting the valve timing at least one of the intake valve and the exhaust valve to obtain a valve overlap mode in which the valve timing is optimized and a non-overlap mode in which valve overlap is eliminated;
• temperature detecting means for detecting a temperature of the engine;
• first control means for controlling the adjusting means to operate within the valve overlap mode;
• second control means for controlling said adjusting means to operate in said non-overlap mode when the detected engine temperature is below a predetermined value;
• and
• wherein said predetermined value is based on a value selected such that the adhered fuel mist is substantially unchanged in amount before and after the valve timing is changed to the overlap mode from the non-overlap mode.

A valve timing control apparatus for an engine having a combustion chamber for combusting a mixture of fuel mist and air therein, an air intake passage for introducing the air to a combustion chamber and exhaust passage for exhausting gas from the combustion chamber, said passages respectively having an intake valve and an exhaust valve therein, and said intake valve and said exhaust valve being actuated in synchronism with the rotation of a crank shaft of the engine to be alternately opened and closed to regulate introduction of the air to and exhausting of the gas from the combustion chamber and to be simultaneously open during a valve overlap period causing a reverse flow of the air-fuel mixture from the combustion chamber to the air intake passage, wherein the fuel mist adheres to an inner surface of the air intake passage;

• said apparatus comprising:
• adjusting means for adjusting the valve timing at least one of the intake valve and the exhaust valve to obtain a valve overlap mode in which the valve timing is optimized and a non-overlap mode in which valve overlap is eliminated;
• condition detecting means for detecting a running condition of the engine;
• temperature detecting means for detecting a temperature of the engine;
• first computing means for computing a first target value of the valve timing to operate within the valve overlap mode based on said detected running condition when the detected engine temperature is above a predetermined value;
• second computing means for computing a second target value of the valve timing to operate within the non-overlap mode when the temperature is below said predetermined value;
• control means for controlling said adjusting means based on one of said first target value and said second target value;
• wherein said predetermined value is based on a value selected such that the adhered fuel mist is substantially unchanged in amount before and after the valve timing is changed to the overlap mode from the non-overlap mode.