Komatsu Galeo BR380JG-1E0 Shop Manual page 130

SEN01352-00
Unload valve
1. When the unload valve is actuating
1. LS circuit
2. Valve
3. Pump circuit
Function
Drains an oil discharge for the portion of the
q
minimum pump swash plate angle while all
control valves are in the holding.
The pump pressure will correspond to a set
q
load of spring (5) inside the valve (this pres-
sure will be P1).
Since LS pressure is drained from the LS
q
bypass valve, LS pressure
2
MPa{0 kg/cm }.
20
tank pressure C 0
C
10 Structure, function and maintenance standard
4. Tank circuit
5. Spring
Operation
Pressure of pump circuit (3) is received by the
q
end of valve (2).
Since the control valve is in neutral position,
q
pressure of LS circuit (1) is 0 MPa{0 kg/cm
Pressurized oil of pump circuit (3) stops at
q
valve (2), and the pressure rises as no relief is
available.
When this pressure becomes larger than the
q
force of spring (5), valve (2) moves to the left.
Ports (b) and (c) are interconnected and the
q
pump pressure flows to tank circuit (4).
The pressurized oil of LS circuit (1) passes
q
from orifice (a) through port (c) and is drained
to the tank circuit (4).
When actuated, LS pressure C tank pressure.
q
Since the pump discharge pressure – LS cir-
q
cuit pressure during unloading is larger than
the pump LS control pressure, the signal is
output to minimize the pump swash plate
angle.
2
}.
BR380JG-1E0