Importance

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Abstract

A precision valve control for an hermetically sealed hydraulic valve system which operates with a solenoid driven magnetic actuator. The magnetic actuator forms a toroidal magnetic force field of varying strength which causes controlled movement of a core rod linked to a pilot. The pilot, in turn, causes actuation of the main disc to the desired valve position. Actual valve position is remotely ascertained, by position of the magnet (or core) within the magnetic field, by means of a Linear Variable Differential Transformer (LVDT). The LVDT creates variable voltages predeterminately related to position of the rod within the magnetic field. The LVDT voltage is compared, by an electronic comparator, to an input command voltage, calibrated to a specific valve position. Deviation between the LVDT voltage feedback signal and input command voltage signal causes generation of an error signal which is amplified and applied to the solenoid to vary the magnetic field to correct the valve position. The fast, continuous feedback control permits constant accurate positioning of the main valve to an accuracy within 0.5% of the valve's command position. The LVDT feedback and comparator control permits, steady state electronic current limiting to prevent excessive heating of the solenoid coil. Other features include direct acting/reverse acting control, as well as control of slew rate and valve seat protection.

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First Claim