Abstract
Pressure reducing valve is the most widely used self-operating regulator, but its characteristics do not seems to be revealed clearly in publications. It has a intrinsic drawback, that is, the reduction of offset by means of increasing gain cannot be attained without increasing its instability because of its proportional control mode. It often oscillates abruptly, and the oscillation occurs in most cases, if the friction caused by the pressure-sealing O-ring is removed. But the friction causes at the same time the dead zone and hysterisis. Therefore, the desirable thing is the reducing valve, which causes small offset and at the same time has a good stability without friction.
Dynamics of a direct-operated pressure reducing valve is analysed here linearly, and the stability conditions are derived and simplified by neglecting very small terms. The simplified stability condition indicates the improving policy of the valve characteristics, that consists of the reduction of mass of the moving parts, the increase of resistance of the port which introduces output pressure into the diaphragm chamber, and the increase of the damping factor of the moving parts.
Experimental data show well the tendency predicted by the analysis.
