Installation Instructions
8 HYDRAULIC SYSTEM
B1700·B2100·B2400
WSM,11770
[6]
RELIEF
VALVE
B177F811
13.2
to
13.7
MPa
135
to
140
kgf/cm
2
1920
to
1991
psi
Maximum
45to
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
of
the 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.
Oil 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 -
D.C.: Damping Chamber
P:
Pump
Port
(1) Plug
(2) Washer
(3)
Shim
C: Cylinder Port
T:
Tank Port
(4) Hydraulic Cylinder Body
(5) Poppet
(6) Seat
8-M6