Abstract: The invention relates to a hydraulic actuator for actuating a gas exchange valve (1) of an internal combustion engine, which valve is especially closed by the effect of a spring. The actuator is configured by a feed pump (6) with intermittent and thus variable delivery. The feed pump (6) has a high frequency and can be equipped for this purpose with piezoelectric, magnetorestrictive and/or electrochemical actuators as the feed elements. Optionally, the feed pump (6) can be operated with a stop valve (7) that is disposed downstream of the gas exchange valve (1) and that is controlled or regulated depending on the feed pump.

Abstract: The invention relates to a hydraulic actuator for actuating a gas exchange valve (1) of an internal combustion engine, which valve is especially closed by the effect of a spring. Said actuator is configured by a feed pump (6) with intermittent and thus variable delivery. Said feed pump (6) has a high frequency and can be equipped for this purpose with piezoelectric, magnetorestrictive and/or electrochemical actuators as the feed elements. Optionally, the feed pump (6) can be operated with a stop valve (7) that is disposed downstream of the gas exchange valve (1) and that is controlled or regulated depending on the feed pump.

Abstract: A two-tube shock absorber for automotive vehicles is furnished with a shock absorber valve positioned at the lower end of its power cylinder and comprising a pilot control stage, a main stage to adjust its "soft" characteristic curve which is desired for reasons of driving comfort, or a special characteristic curve out of a field of potential characteristic curves. According to the invention, in a lower range of piston speed the shock absorbing power is determined exclusively by the variable cross-sectional area of flow of the pilot control stage wherein the main stage remains closed. In an upper range of piston speed the shock absorbing power is determined by the variable flow cross-sectional areas both of the main stage and of the pilot control stage.

Abstract: A two-tube shock absorber for automotive vehicles is furnished with a shock absorber piston and an electromagnetically actuatable unidirectional shock absorber valve to adjust a "smooth" characteristic which is desired for enhancing driving comfort. The shock absorber valve is alternatively configurated in the shape of a single-stage, or a two-stage slide valve. The position of the slide depends on the hydraulic pressure differential which decreases above the shock absorber valve, the volumetric stream which flows through the shock absorber valve, and the actuating current of the electromagnetic actuating unit. The inventive shock absorber allows the selection of a special characteristic curve out of a family of potential characteristic curves. Simultaneously, the sensitivity of the shock absorber to errors of the electromagnetic actuation is eliminated.