THEORY OF OPERATION - CONTINUED
HYDRAULIC SYSTEM - CONTINUED
When less flow is required, piston pump destrokes. Piston pump destrokes when force at right of flow
compensator spool becomes greater than force at left.
Flow compensator spool moves left, which allows more oil flow to actuator piston. Pressure on actuator
piston is now increased.
Increased pressure overcomes force of bias spring which moves swashplate to a reduced angle. When pres-
sure from pump outlet matches force at left of flow compensator spool, spool returns to a metering posi-
tion. Piston pump returns to a constant flow.
These conditions result in destroking piston pump:
(a) A main control spool for a bank valve is moved to HOLD.
(b) Main control spool for a bank valve is moved to a position that requires less flow.
(c) If multiple bank valves are being used, piston pump will destroke when there is a reduction in demand
from any one control valve.
(d) Engine speed increases.
N OT E
The load sensing signal pressure does not need to decrease in order to destroke piston pump.
When piston pump destrokes, supply oil pressure from pump outlet increases on right side of flow com-
pensator spool. This overcomes pressure on left side of flow compensator spool. Flow compensator spool
moves left. Supply oil flows to cavity behind actuator piston. This destrokes pump. Once flow demand is
met, flow compensator spool meters force on both ends of spool. Once forces become equal on each end of
spool, system will stabilize.