Komatsu PC58UU-3, Руководство по ремонту

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STRUCTURE, FUNCTION AND MAINTENANCE STANDARD PPC VALVE
PC58UU-3
10-85
12
3. In the fine control mode (operating lever
shifted back to its original position)
• As the disk (5) starts returning, the spool (1) is
pushed up by the force of the centering
spring (3) and the pressure port
P1 .
• Thus, passage between the fine control hole f
and drain chamber D becomes available,
thereby relieving pressurized oil of port P1 .
• Of port P1 pressure goes excessively low,
the spool (1) is pushed down by the metering
spring (2) and passage between the fine con-
trol hole
f and drain chamber D is shut down.
Almost at the same time, the hole is con-
nected to the pump pressure chamber
PP
and starts supplying pump pressure. This
supply continues until the port
P1 pressure
has recovered to the level equivalent to the
lever position.
• When the operation valve returns, oil in the
drain chamber
D flows in through the fine
control hole f’ on the non moving side valve.
Oil is then conducted via port P2 to fill up
chamber B .
4. In the full stroke mode
• When the disk (5) pushes down the piston (4)
and the retainer (9) pushes down the spool
(1), connection of the fine control hole
f is
switched from drain chamber D to the pump
pressure chamber PP.
• Thus, pilot pressurized oil from the control
pump passes through the fine control hole
f
and is conducted to chamber A via port P1 to
push the operation valve spool.
• Return oil from chamber B is conducted from
port P2 to drain chamber D via the fine con-
trol hole f’ .
(5)