Komatsu Galeo PC800-8 Shop Manual page 199

10 Structure, function and maintenance standard
1-5 Travel brake valve
Function
• The brake valve consists of counterbalance
valve (3) and check valve (4).
• The counterbalance valve acts to prevent the
piston motor from stopping or overrunning.
• When traveling downhill, the weight of the ma-
chine makes it try to travel at a speed faster than
the rotation of the motor.
For this reason, if the machine is traveling with
the engine running at low speed, the motor will
rotate under no load or may run away, which is
extremely dangerous.
To prevent this, this valve controls the amount of
oil on the return side in order to keep the valve
pressure constant, and makes it possible to
carry out travel operations which match the oil
delivery from the motor.
PC800, 850-8
1. Cap assembly
2. Return spring
3. Counterbalance valve
4. Check valve
5. Check valve spring
Specification
Safety valve set pressure:
Counterbalance switching pressure:
1.0 ± 0.1 MPa {10 ± 1 kg/cm
Check valve switching pressure:
0.02 ± 0.01 MPa {0.2 ± 0.1 kg/cm
SEN00384-02
34 MPa {350 kg/cm }
2
}
2
}
2
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