Chapter 8 Flow control valves limiting the fluid

Chapter 8 Flow control valves

— limiting the fluid volume flow rate from fixed displacement pumps accurately. — Applications: velocity control of cylinders; speed control of hydraulic motors — ; where Q : volume flow rate to actuator A : effective area of cylinder piston V : displacement of hydraulic motor § Type of flow control valves 1) Throttle valves Non-variable restriction(i. e. adjustable) —

2) Pressure compensated flow control valve Basic idea : Q constant , indep. of change in P Principle of operation :

Neglecting flow force , obtaining the eq. of force equilibrium on the pressure compensator: P 1 A=PL A + Ff P = P 1 – PL = ∵Ff =k(x 0 – x )且 x << x 0 (B)meter-out (Ps – PL)A= P 1 A + Ff P = (Ps – PL ) – P 1= Q constant (x 0 : Pre-compression)

— static performance E 4 : due to flow force at large Q E 1 : due to the characteristic of the original throttle

(2)節流閥(Throttle valve)

1)節流閥： (具備free reverse flow)

減速閥(deceleration valve)： (a)結構及 作原理

分流閥(flow divider valves) (a)Flow divider valve with equal flow division

(b)Priority flow divider valve