Komatsu PC200-8M0 Shop Manual page 224

SEN06121-00
3. During fine control
(When control lever is returned)
When disc (5) starts to be returned, spool (1) is
q
pushed up by the force of centering spring (3)
and the pressure at port (P1).
q Because of this, fine control hole (f) is con-
nected to drain chamber (D), and the pressur-
ized oil at port (P1) is released.
q If the pressure of port (P1) is lowered exces-
sively, spool (1) is pushed down by metering
spring (2).
q Fine control hole (f) is shut off from drain
chamber (D), and it is almost simultaneously
interconnected to pump pressure chamber
(PP).
q Pump pressure is supplied until the pressure at
port (P1) recovers to the level equivalent to the
lever position.
q When the spool of the control valve returns,
the oil in drain chamber (D) flows in from fine
control hole (f') in the valve on the side that is
not working. The oil passes through port (P2)
and enters chamber (B) to replenish the cham-
ber with pressurized oil.
26
10-403
403 Hydraulic system, Part 3
4. At full stroke
Disc (5) pushes down piston (4), and retainer
q
(9) pushes down spool (1).
q Fine control hole (f) is shut off from drain
chamber (D), and is interconnected to pump
pressure chamber (PP).
q Therefore, the pilot pressure oil from the self
pressure reducing valve passes through fine
control hole (f) and flows to chamber (A) from
port (P1) to push the control valve spool.
q The oil returning from chamber (B) passes
from port (P2) through fine control hole (f') and
flows to drain chamber (D).
PC200, 200LC, 220, 220LC-8M0
PPC valve