Komatsu PC88MR-10 Shop Manual page 220

10 Structure and function
Travel PPC valve
When control lever is fully operated
Lever (5) pushes down piston (4), and retainer (9) pushes down spool (1).
Fine control hole (f) is disconnected from drain chamber (D) and connected to pump pressure chamber
(PP).
The pilot pressure oil from the self-pressure reducing valve passes through fine control hole (f) and flows
from port (P1) to port (A) and pushes the control valve spool.
The oil returning from port (B) flows from port (P2) through fine control hole (f') into drain chamber (D).
10-142 PC88MR-10