Variable valve timing control device for an engine

Abstract

The variable valve timing control device according to the present invention controls the valve timing of the intake valves of the engine based on the optimum valve timing at the full load operation of the engine. Namely, the variable valve timing control device of the present invention determines the valve timing in accordance with the combination of the present engine load and the present engine speed in such a manner that the deviation of the valve timing from the optimum valve timing when the engine is operated in full load at the present speed does not exceed a predetermined maximum allowable value. Since the valve timing of the engine is always set within a range determined by the maximum allowable deviation from the optimum valve timing for the full load operation, when the engine is accelerated to the full load condition the amount of the change, i.e., the amount of the operation of the variable valve timing control device is kept always within the range determined by the maximum allowable deviation. Therefore, the time required for changing the valve timing to the optimum valve timing for the full load operation is always short regardless of the present operating condition of the engine. Consequently, the response of the valve timing control can be improved without increasing the operating speed of the variable valve timing control device.