Komatsu PC88MR-10 Shop Manual page 158

10 Structure and function
Control valve
When fine control operation of work equipment is performed
Work equipment: Swing, boom, arm, bucket, boom swing, attachment
Function
When the fine control operation of the work equipment is performed and the actuator demand flow is
below the flow at the pump minimum swash plate angle.
Pump discharged pressures (PP1) and (PP2) are set to LS pressures (PLS1) and (PLS2) + 2.45 MPa
{25.0 kg/cm }.
2
The differential pressure between pump discharged pressure (PP1)/(PP2) and LS pressure (PLS1)/
(PLS2) becomes the load at installed height of spring (2) (2.45 MPa {25.0 kg/cm
Unload spool (1) opens.
LS differential pressure (dPLS) becomes 2.45 MPa {25.0 kg/cm
Since the merge-divider spool is at the merge position, pump discharged pressures (PP1) and (PP2) are
merged.
LS pressures (PLS1), (PLS2), and (PLS3) are merged.
Operation
When the work equipment is controlled finely, LS pressures (PLS1) and (PLS2) are generated and act on
the left side of spool (1). (PP1 = PP2, PLS1 = PLS2) Since the open area of the work equipment control
valve spool is small, the differential pressure between LS pressure (PLS1)/(PLS2) and pump discharged
pressure (PP1)/(PP2) is large.
The differential pressure between pump discharged pressure (PP1)/(PP2) and LS pressure (PLS1)/
(PLS2) reaches the load at installed height of spring (2) (2.45 MPa {25.0 kg/cm
Spool (1) moves to the left.
Pump circuits (PP1) and (PP2) are interconnected to tank circuit (T).
10-80
2 }).
2 }.
2 }).
PC88MR-10