Hydraulic Control Valve; Relief Valve - Kubota RTV1140CPX Workshop Manual

RTV1140CPX, WSM

4. HYDRAULIC CONTROL VALVE

[1] RELIEF VALVE

The hydraulic raising and lowering circuit is fitted
with a relief valve to control the maximum pressure.
This is a guide piston relief valve with damper, a
direct acting relief valve suitable for relatively high
pressure and capacity, and constructed so as to prevent
chattering and other unstableness associated with direct
acting relief valves. As shown in the diagram, poppet (5)
has a guide, and there is a valve chamber called a
damping chamber (6) in the base of this guide piston.
The valve inlet is connected to this chamber through the
clearance between the guide surface and the seat so
that the chamber provides a damping effect, controlling
valve vibration.
When the pressure in the circuit rises, the pressure
in the damping chamber also rises, and when it exceeds
the relief pressure setting the spring is compressed,
making a clearance between the poppet and the seat.
The hydraulic oil can escape to the transmission case
through this clearance, controlling the pressure rise.
• Relief valve setting pressure
14.5 to 15.5 MPa
148 to 158 kgf/cm
2110 to 2240 psi
Condition
• Engine speed
−1
3000 min (rpm)
• Oil temperature
45 to 55 °C (113 to 131 °F)
(1) Relief Valve
(2) Shim
(3) Plug
(4) Seat
(5) Poppet
(6) Damping Chamber
7-M4
HYDRAULIC SYSTEM
2
(a) Normal State
(b) Active State
T: T Port
(To Transmission Case)
P: P Port (From Pump)
9Y1210293HYM0009US0
KiSC issued 05, 2014 A