Komatsu PC88MR-10 Shop Manual page 181

Function
When the travel and another actuators are operated simultaneously, discarded throttled flow of LS
pressure (PLS) is increased to loosen the pressure compensation accuracy of the travel circuit and reduce
the decrease in the travel speed.
The travel or another actuator is operated singly, the LS bleed circuit is closed.
Also, travel junction valve spool (5) is changed from large opening (c) o small opening (b) so that the flow
rate different between the R.H. and L.H. travel circuits can be corrected easily.
Operation
When normally operated
When boom spool (1) is operated, LS pressure (PLS) becomes the same as the pressure in boom circuit
(A).
Since the work equipment valve is operated, pump discharge circuits (PP1) and (PP2) and LS circuits
(PLS1), (PLS2) and (PLS3) are merged respectively by the merge-divider spool (See "Merge-divider
valve").
LS pressure (PLS) is also led to spring chamber (PLSS) of pressure reducing valve (2) of the travel valve.
Since the travel spool is not operated, notch (a) of pressure reducing valve (2) is closed, and check valves
(3) and (4) of the bleed circuit are also closed.
When the boom is operated singly, travel LS bleed circuit is closed.
When travel and another actuator are operated
When boom spool (1) is operated, LS pressure (PLS) becomes the same as boom circuit pressure (A).
Since the work equipment valve is operated, pump discharge circuits (PP1) and (PP2) and LS circuits
(PLS1), (PLS2) and (PLS3) are merged respectively by the merge-divider spool (See "MERGE-DIVIDER
VALVE").
Since the boom RAISE pressure in the actuator circuit is normally higher than the travel pressure (A > B),
the pressure in spring chamber (PLSS) of pressure reducing valve (2) on the travel side is higher than
travel circuit pressure (PB).
Pressure reducing valve (2) moves to the left and LS pressure (PLS) is transmitted through check valves
(3) and (4) of the bleed circuit and notch (a) of pressure reducing valve (2) to travel circuit (PB).
LS pressure (PLS) which is the same as boom circuit pressure (A) decreases since it released into travel
circuit (B).
PC88MR-10
10 Structure and function
Control valve
10-103