US Patent 7325522 Valve drive for a cam-operated valve

A valve drive (1) for a cam-operated valve (2) of an internal combustion engine is provided, in which a closing force is applied to the valve (2) against the opening direction of the valve (2) by a valve spring (3). The valve drive includes a hydraulic force application device (4), with which a force can be applied directly or indirectly against the direction of the closing force onto the valve (2), and includes a piston (5) that is moveable in a displacement direction (R) relative to a cylinder (6) of the force application device (4) by the introduction of hydraulic fluid into the pressure chamber (7) formed between the piston (5) and the cylinder (6). The piston (5) can move relative to the cylinder (6) from a first end position (A) into a second end position (B). In order to achieve improved damping of the piston in the region of the end positions, a braking or damping system (8, 9) is provided with which the movement of the piston (5) can be braked relative to the cylinder (6) when a predetermined relative position between the piston (5) and cylinder (6) is reached and until one of the end positions (A, B) is reached.