Kubota KX080-4 Workshop Manual page 149

KX080-4, WSM
b) During boom down operation (return circuit
operation)
• The return oil from the control valve enters port A
(A), passes through the orifice (3) and is discharged
to port 1 (1). When it does, the resistance to passing
through the orifice (3) results in the pressure of
chamber a (a) being greater than that of chamber b
(b), so the plunger (4) moves downwards.
• The movement of the plunger (4) closes orifice c (c),
raising the pressure in chamber b (b).
• Once the pressures of chamber a (a) and chamber b
(b) equalize, the plunger (4) is returned toward
neutral by the spring (5). Repition of this dynamic
keeps the plunger (4) at a balanced position. As a
result, the pressure differential across the orifice (3)
is fixed, allowing the flow of oil through the orifice (3)
to be steady without maintaining the pilot pressure.
• When the pilot valve is returned to its neutral
position, no oil comes from the pilot valve and the
control valve tries to return to the neutral position.
• Return oil from port B flows to port 1 via the orifice
(3). The speed of the main spool of the control valve
is limited by passing through the orifice (3).
(Shockless function)
(1) Port 1
(2) Port 2
(3) Orifice
(4) Plunger
(5) Spring
3-M53
HYDRAULIC SYSTEM
(A) Port A
(B) Port B
(T) Port T
(a) Chamber a
(b) Chamber b
(c) Orifice c
RY9212148HYM0055US0
KiSC issued 08, 2015 A