Komatsu Galeo PC800-8 Shop Manual page 206

SEN00384-02
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, port P1 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 down by metering spring (2), so
port P1 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 pres-
sure recovers to a pressure equivalent to the
position of the lever.
When the control valve returns, oil in drain
chamber D flows in from the valve on the side
that is not moving. It passes through port P2 and
goes to chamber B to charge the oil.
4) At full stroke
When disc (5) pushes down piston (4), and
retainer (9) pushes down spool (1), port P1 is
shut off from drain chamber D, and is connected
to pump pressure chamber PP. Therefore, the
pilot pressure oil from the control pump flows to
chamber A from port P1 to push the control
valve spool.
The return oil from chamber B passes from port
P2 and flows to drain chamber D.
44
10 Structure, function and maintenance standard
PC800, 850-8