Komatsu PC88MR-10 Shop Manual page 178

10 Structure and function
Control valve
The flows to the right and left travel motors becomes almost the same rate during straight travel to reduce
travel deviation.
The travel junction circuit is also open during steering operation, but it does not affect the steering
performance since open area (b) of travel junction spool (3) is small.
Operation
When traveling straight
Since only R.H and L.H. travel valves are operated and the work equipment control valve is not operated,
pump discharge circuits (PP1) and (PP2) and LS circuits (PLS1) and (PLS2) are divided respectively by
the merge-divider spool (See "Merge-divider valve").
When R.H. and L.H. travel spools (1) are operated, the oil delivered from the pump flows to actuator circuit
(B) through pump discharge circuits (PP1) and (PP2).
When the machine is traveled straight, R.H. and L.H. pressure reducing valves (2) are pushed to the right
and notch (a) and the connection circuit (c) are opened.
The right end of travel junction valve spool (3) is connected to the work equipment PPC pressure circuit.
However, since the work equipment control valve is not operated, no pressure occurs.
When R.H. and L.H. actuator circuits (B) are connected by travel junction circuit (c), if a difference occurs
between the flows to R.H. and L.H. travel motors, that difference is corrected to reduce travel deviation.
When steering while traveling
Since only R.H and L.H. travel valves are operated and the work equipment control valve is not operated,
pump discharge circuits (PP1) and (PP2) and LS circuits (PLS1) and (PLS2) are divided respectively by
the merge-divider spool (See "Merge-divider valve").
Steering operation is performed by supplying the demand flow corresponding with the travels of the R.H.
and L.H. travel spools (1) to the actuator circuit (B) (See "Unload valve").
When the R.H. travel spool (Right 1) is returned to neutral from the straight-travel condition and the
steering operation is performed, load pressure difference (PB) is made between R.H. and L.H. actuator
circuits (B) [(Left B) > (Right B)].
10-100 PC88MR-10