Komatsu ecot3 PC300LC-8 Shop Manual page 231

10 Structure, function and maintenance standard
The pressurized oil on the supply side flows to
q
chamber (S1) via orifice (E1) and orifice (E2) of
the spool (24).
q As the pressure in chamber (S1) goes above
the spool selector pressure, spool (24) is
pushed toward right.
q Port (MB) and port (PB) are connected, open-
ing the motor outlet port side and starting the
motor rotating.
PC300, 350-8
Operation of brake during travelling downhill
If indication of the machine runaway is sensed
q
while travelling downhill, the motor will be
caused to rotate without load to decrease the
inlet side oil pressure.
Pressure in chamber (S1) is released via ori-
q
fices (E1) and (E2).
q As the pressure in chamber (S1) goes below
the spool selector pressure, spool (24) is
returned to the left by spring (20) and outlet
port (MB) is throttled.
q The pressure at the outlet port side rises, gen-
erating rotation resistance on the motor to pre-
vent the machine from running away.
q The spool moves to a position where the pres-
sure on outlet port (MB) can be balanced
against the machine's own weight and the inlet
port pressure.
q Oil flow from the outlet circuit is reduced to
ensure the travel speed corresponded to the
pump delivery.
SEN01995-01
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