Abstract: A mechanism for switching valve operating modes in an internal combustion engine that has a valve operating mechanism with high- and low-speed cams having different cam profiles corresponding to rotational speed ranges of the engine, a pair of valves disposed in intake or exhaust ports of a combustion chamber and a normally urged to be closed by spring means, a directly moving transmitting member for imparting the lift of the low-speed cam to the valve, a pair of idling transmitting members for transmitting the lift of said high-speed cam on the pair of valves and a selective coupling mechanism for selectively connecting the transmitting members when mutually adjacent portions of the transmitting members are in a predetermined positional relationship.

Abstract: An angular adjustment is provided between a crankshaft and camshaft by a hydraulically operated rotary vane, which is pivotably mounted on the camshaft and is supported on a sprocket wheel carrier driven by a crankshaft rotation of the vane causing a relative rotation to take place between the crankshaft and camshaft. The rotary vane is held in each of its two end positions by a spring device.

Abstract: A method and apparatus for controlling valve operation in an internal combustion engine having a crankshaft during with a cam for opening and closing an intake or exhaust valve which is spring-biased in a closing direction. The method comprises the steps of varying the angular phase of the crankshaft and the camshaft to control the timing of the opening of the valve and releasing the force applied by the cam to open the valve while it is being opened to control the timing of the closing of the intake or exhaust valve. The apparatus includes a phase control mechanism disposed between the crankshaft and the camshaft and a lift control mechanism disposed between the cam and the intake or exhaust valve. Both mechanisms are hydraulically operated and controlled in response to engine operating conditions.