Komatsu Galeo BR380JG-1E0 Shop Manual page 131

10 Structure, function and maintenance standard
During operation (a work within a scope of dis-
q
charge by a minimum swash plate angle), the
discharge pressure for the portion of minimum
pump swash plate angle is set to LS pressure
+ P1 pressure.
LS control differential pressure (dPLS) of dis-
q
charge for the portion of minimum swash plate
angle will be equal to P1 pressure.
BR380JG-1E0
2. Operation of relief valve
(Cut-off Control Actuated)
Function
When cut-off control is being carried out on the
q
pump by the PC valve, the pump swash plate
angle is at the minimum.
The relief valve acts to relieve the oil flow when
q
the pump is at the minimum swash plate angle
in order to maintain the balance.
Operation
When the cylinder reaches the stroke end, the
q
main relief valve opens.
The pump delivery (Q) is relieved to the tank.
q
(See the system diagram)
When pump discharge pressure (PP) comes
q
close to the relief pressure, the engine throttle
and pump controller sends a signal to the sole-
noid of the PC valve.
Carries out the cut-off function to make pump
q
delivery (Q) the minimum.
The pump discharge pressure (PP) and LS
q
pressure (PLS) become approximately the
same as each has not flow at the upstream and
downstream of the spool, and LS differential
pressure (dPLS) becomes 0 MPa{0 kg/cm
As LS differential pressure (dPLS) is lower
q
than the LS set pressure of LS valve, LS valve
is actuated to maximize the pump swash plate
angle.
Mechanically, operation of PC valve have the
q
prevalence to that of LS valve.
The pump is held at a minimum swash plate
q
angle by the cut-off function of PC valve.
SEN01352-00
2
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