Patent ID: 6973900
Filing Date: 2005-12-13
Classification: F01L

Abstract:
1. A valve drive system for an internal combustion engine, comprising: a plurality of valves; springs urging each of the valves towards a middle position between a fully open position and a fully closed position; magnets each supplied with current to generate electromagnetic force to retain each of the valves at the fully open or closed position against the urging force of each spring; a controller that is adapted to stop application of current to at least one magnet for a first valve or a first valve group among the valves at a first timing and stop application of current to at least one magnet for a second valve or a second valve group among the valves at a second timing that is different from the first timing when the internal combustion engine is to be stopped; and a valve displacement detector that detects an amount that the valve is displaced due to its free oscillation, wherein the controller is further adapted to determine based on the valve displacement amount detected by the valve displacement detector that the free oscillation of the first valve or the first valve group has decayed to a specific level.