Installation Instructions
8 HYDRAULIC
SYSTEM
B1700·B2100·B2400 WSM,11772
[6]
RELIEF
VALVE
B177F811
13.2
to
13.7
MPa
135
to
140
kgf/cm
2
1920
to
1991
psi
Maximum
45
to
55°C
113
to
131°F
Engine speed:
Oil
temperature:
The Three
point
hydraulic
system
circuit
has
a
relief valve
to
restrict the maximum pressure in
the
circuit.
The
relief valve
is
located
top
of
the
hydraulic
cylinder body.
The
relief valve
is
of
the
guide piston type
with
damping effect.
Among
direct
acting
relief
valves,
this
type
is
suited
to
higher
pressure and has large capacity.
Furthermore,
this
type
is
free
from
unstable
operation,
such
as
chattering, which occurs often in
direct acting relief valves.
As
shown in
the
figure,
the
guide
is
attached
to
the poppet
(5)
and a valve chamber
D.C.
(called
the
damping chamber)
is
formed
at
the
bottom
of
the
guide piston.
The
inlet
of
the
valve leads
to
the
chamber via a clearance between
the
sliding
portion
of
the
guide
and
the
seat (6),
minimizing
valve
vibration
with
the
damping effect
ofthe
chamber.
When the oil pressure in
the
circuit
is
lower
than
the setting pressure
of
the
relief
valve,
the
relief
valve
is
not
operated and
the
oil fed
to
the
relief
valve
from
the
hydraulic
pump
flows
into
the
position control valve.
As
the oil pressure in
the
circuit increases,
so
does
the pressure in the damping chamber
D.C.
When
the
pressure
rises
above
the
valve setting and overcomes
the spring force,
the
valve opens. Qil then flows
out
to
the transmission
case
through
T port, preventing
any
further
rise
in pressure.
The
valve
closes
again
when enough oil
is
released
to
drop
pressure
below
the
valve setting.
(Reference)
• Relief Valve setting pressure:
4
2 3
I
T Port I
(To Transmission Case)
I
I
I
+
To Position Control
Valve
[-
From Hydraulic _
Pump
From Hydraulic
Pump
- L--.-cll.V----'"="
D.C.: Damping Chamber
P:
Pump Port
C:
Cylinder Port
T:
Tank Port
(1)
Plug
(2)
Washer
(3) Shim
(4)
Hydraulic Cylinder Body
(5)
Poppet
(6)
Seat
E8-M7