Komatsu ecot3 PC300LC-8 Shop Manual page 233

10 Structure, function and maintenance standard
2) When pressure in chamber (MA) has
become high (when rotating counterclock-
wise)
As long as the machine travel is stopped (or it
q
is travelling downhill), the check valve of coun-
terbalance valve closes chamber (MA) of the
outlet port circuit.
The motor tries to continue rotation resorting to
q
inertial force, thus pressure on the outlet port
(MA) is increased.
q As the pressure goes above the set pressure,
[Difference in areas of circles (D1) and (D3) x
Pressure] compresses spring (2).
q Poppet (1) is moved leftward and the pressur-
ized oil flows into chamber (MB) of the oppo-
site circuit.
PC300, 350-8
Operation of mechanism for varying set pres-
sure
1) When starting travel (high-pressure setting)
As the travel lever is operated, the pressurized
q
oil from the pump moves spool (19) toward
right.
q Above opens the pilot circuit to the safety
valve, conducting the pressurized oil to cham-
ber (J) via chamber (G) and passage (H).
q Piston (3) is pushed rightward, spring (2) is
compressed and the set load is increased.
q High pressure is turned on the safety valve,
providing a large tractional force to the valve.
SEN01995-01
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