Komatsu Galeo PC800-8 Shop Manual page 211

10 Structure, function and maintenance standard
3. Fine control (control lever returned)
• When disc (5) starts to be returned, spool (1) is
pushed up by the force of centering spring (3)
and the pressure at port P1.
Because of this, fine control hole f is connected
to drain chamber D, and the pressurized oil at
port P1 is released.
• If the pressure at port P1 drops too much, spool
(1) is pushed up by metering spring (2), so fine
control hole f is shut off from drain chamber D. At
almost the same time, it is connected to pump
pressure chamber PP, so the pressure at port P1
supplies the pump pressure until the pressure re-
covers to a pressure equivalent to the position of
the lever.
• When the control valve returns, oil in drain cham-
ber D flows in from fine control hole f ' of the valve
on the side that is not moving. It passes through
port P2 and enters chamber B to fill the chamber
with oil.
4. At full stroke
• Disc (5) pushes down piston (4), and retainer (9)
pushes down spool (1). Fine control hole f is shut
off from drain chamber D, and is connected to
pump pressure chamber PP.
• Therefore, the pilot pressure oil from the main
pump passes through fine control hole f and
flows to chamber A from port P1 to push the con-
trol valve spool.
• The return oil chamber B passes from port P2
through fine control hole f ' and flows to drain
chamber D.
PC800, 850-8
SEN00384-02
49