抄録
In this paper, flow force due to nozzle flow and its influence on the flapper-nozzle system for water hydraulic servovalves are discussed. The flow force acting on the flapper is estimated using the momentum theory, and expressed as a function of the nozzle pressure and flapper-nozzle gap. Analysis shows that the double nozzle flapper gives a quasi-linear characteristic to the relationship among the force on the flapper, the flapper gap and the spool velocity. The numerical result based on the theory is used to estimate the accuracy of the classical linear approximation. The moment due to the flow force resists input moment acting on the armature. Consequently the flow force reduces the magnitude of the change of the nozzle backpressures that drive the spool of the water hydraulic valve. Experimental verification of the theory is also presented.
