Patent ID: 6570474
Filing Date: 2003-05-27
Classification: F01L,F16K

Abstract:
A magnetostrictive valve actuator comprising:a body having a first cavity and a second cavity, the first cavity having a distal end and a proximal end forming a longitudinal axis and the second cavity forming a hydraulic chamber in communication with the first cavity via a first bore having a first sealing diameter; a first piston positioned in the first bore, the first piston being displaceable in the direction of the longitudinal axis; a second bore having a second sealing diameter, the second bore being in communication with the hydraulic chamber; a second piston positioned in the second bore, the second piston being displaceable within the second bore in response to changes in hydraulic pressure within the hydraulic chamber; a magnetostrictive member having a predetermined length disposed substantially in the direction of the longitudinal axis of the first cavity, the magnetostrictive member being in operative contact with the first piston; a coil that generates a magnetic field disposed proximate the magnetostrictive element such that magnetic flux passes through the magnetostrictive element upon excitation of the coil, causing the predetermined length to increase, forcing the first piston to be displaced toward the hydraulic chamber and the second piston to move under the influence of the hydraulic pressure created by the displacement of the first piston; and biasing means disposed in the body and operatively arranged to exert a predetermined prestress force on the magnetostrictive member, wherein the prestress force is in the range of 5-15 MPa.