Komatsu Galeo PC138US-8 Shop Manual page 167

10 Structure, function and maintenance standard
Function
When the load pressure becomes lower than
q
another actuator and the flow is going to
increase during a compound operation, this
valve compensates the load pressure. [At the
time, the load pressure of another actuator
under compound operation (the upper side) is
higher than that of the actuator on this side
(the lower side)].
Operation
When the load pressure (Ab) of another actua-
q
tor side (the upper side) rises during a com-
pound operation, the flow in the actuator circuit
(Aa) on this side (the lower side) is apt to
increase.
In this case, the LS pressure (PLS) of another
q
actuator is applied to the spring chamber
(PLS1) and pushes the pressure reducing
valve (1) and the flow control valve (2) to the
left side.
The flow control valve (2) throttles the opening
q
area between the pump circuit (PP) and the
spool upstream (PPA) and causes a pressure
loss between (PP) and (PPA).
The flow control valve (2) and the pressure
q
reducing valve (1) balance each other where
the pressure difference between (PA) applied
to the both end faces of the pressure reducing
valve (1) and (PLS) becomes the same as the
pressure loss between (PP) before and after
the flow control valve (2) and (PPA).
So, the pressure differences between the
q
upstream pressures (PPA) and the down-
stream pressures (PA) of the both spools
under compound operation become the same,
and the pump flow is distributed in proportion
to the opening area of each spool notch (a).
PC138US, USLC-8
SEN02549-02
33