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 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: P1 A=PL A + Ff P = P1 PL =

(B)meter-out

(Ps PL)A= P1 A + Ff P = (Ps PL ) P1= Q constant Ff =k(x0 x ) x

static performance E4 : due to flow force at large QE1 : due to the characteristic of the original throttle

(2)(Throttle valve)

(3)

1) (free reverse flow)

2)

3),

(two-way) (three-way)(a)Two-way: ()

(b)Three-way: ()

(deceleration valve)(a)

(b)symbols

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

(b)Priority flow divider valve