Relief Valve - wsm STW37 Workshop Manual

STW34, STW37, STW40, WSM

[4] RELIEF VALVE

The 3-point hydraulic circuit has a relief valve to
restrict the maximum pressure in its circuit.
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.
(Reference)
• Relief valve setting pressure:
16.7 to 17.2 MPa (170 to 175 kgf/cm
2417.4 to 2488.5 psi)
• Engine speed:
Maximum
• Oil temperature:
40 to 60 °C (104 to 140 °F)
(1) Washer
(2) Shim
(3) Plug
(4) Seat
(5) Poppet
(6) Damping Chamber
8-M15
HYDRAULIC SYSTEM
2
,
T: Tank Port
P0: P0 Port (Pump Port)
P1: P1 Port (To Auxiliary
Control Valve)
9Y1211109HYM0014US0
KiSC issued 11, 2014 A