Komatsu Galeo PC138US-8 Shop Manual page 155

10 Structure, function and maintenance standard
2. When work equipment valve is operated
Function
When any work equipment valve is operated if
q
the demand flow for the actuator becomes
greater than the pump discharge from the min-
imum swash plate angle, the oil flow to tank cir-
cuit (T) is cut off, and all pump delivery (Q)
flows to the actuator circuit.
Since the pump merge-divider valve is at the
q
merge position, pump discharge pressures
(P1) and (P2) are merged. LS pressures (LS1),
(LS2), and (LS3) are also merged.
PC138US, USLC-8
Operation
When any work equipment valve is operated
q
for a long stroke, LS pressures (LS1) and
(LS2) are generated and act on the face (SB)
of unload spool (1) [(P1) = (P2), (LS1) = (LS2)].
For this reason, the difference between pump
q
discharge pressure (P1) and (P2) and LS pres-
sure (LS1) and (LS2) does not reach the load
of spring (2), so spool (1) is pushed to the right
by spring (2).
As a result, pump discharge pressures (P1)
q
and (P2) and tank circuit (T) are shut off, and
all pump delivery (Q) flows to the actuator cir-
cuit.
SEN02549-02
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