The electrohydraulic servo valve 072-559A has high pressure efficiency and volumetric efficiency, which can generate greater control pressure and flow, improving the driving force and anti-pollution ability of the power valve. From the perspective of the impact of early wear on performance, the wear of the nozzle end face and the receiving end face of the electro-hydraulic servo valve has little impact on performance, resulting in stable operation, small drift, and long service life.
An electrical command signal (flow rate set point) is applied to the torque motor coils, and creates a magnetic force which acts on the ends of the pilot stage armature. This causes a deflection of armature/flapper assembly within the flexure tube. Deflection of the flapper restricts fluid flow through one nozzle which is carried through to one spool end, displacing the spool.
Movement of the spool opens the supply pressure port (P) to one control port, while simultaneously opening the tank port (T) to the other control port. The spool motion also applies a force to the cantilever spring, creating a restoring torque on the armature/flapper assembly. Once the restoring
torque becomes equal to the torque from the magnetic forces, the armature/flapper assembly moves back to the neutral position, and the spool is held open in a state of equilibrium until the command signal changes to a new level.
In summary, the spool position is proportional to the input current and with constant pressure drop across the valve; flow to the load is proportional to the spool position.