Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Mechanical Design and Production

High frequency hydraulic control valves can be realized when the required stroking forces and displacements of the valving elements, whether poppets or spools, are small enough to cope with the capabilities of compact actuating devices. A new class of valves are proposed and analyzed in this work, in which the valving elements are subjected to the high inlet pressure on both sides that have small area difference. This would result in reducing both the required driving forces and the strength needs of these valving elements. The return of the valving elements to their initial positions in this case results from the small pressure and flow forces unbalance only, or with the assistance of an additional spring force. A valve design with long control edge is developed to allow obtaining appreciable large control orifice area from a small valving element displacement, and hence a high flow gain is realized. The small valving element displacement reduces the demands imposed on the actuating devices and allows the use of piezoelectric actuators of short stroke or electromagnetic driving devices that generate high forces at narrow gaps and reasonable ampere-turn values. The configurations of the proposed fast switching valves well fit the requirements of the pulse width modulation control techniques

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