Komatsu PC500LC-10R Shop Manual page 347

10 STRUCTURE AND FUNCTION
Travel control system is a system that changes travel speed as the motor capacity is changed by setting the
travel speed selector switch to Hi, Mi, or Lo position.
Travel speed selector switch
Motor flow rate
Motor capacity
Travel speed
Automatic gear shift of travel speed
• Automatic gear shift corresponding to the engine speed
When the engine speed is decreased to 1200 rpm or less by using the fuel control dial, the travel speed
does not change to "Hi" if the current speed is Mi, but it changes to Mi automatically if the current speed is
Hi.
• Automatic gear shift corresponding to pump discharged pressure
• While traveling with the travel speed selector switch at Hi position, if the load increases on uphill slope,
etc., and the travel pressure is 32.3 MPa {330 kg/cm
capacity is changed automatically and the travel speed is changed to a mid-range speed (a speed
equivalent to Mi) (however, travel speed selector switch is kept at Hi position).
• While traveling at low speed set by the automatic gear shift with load, when the load decreases on a
flat or downhill slope and the travel pressure is 22.5 MPa {230 kg/cm
the motor capacity is changed automatically and the travel speed is returned to the set speed of Hi.
A: 22.5 MPa 230 kg/cm
B: 32.3 MPa 330 kg/cm
C: 0.5 seconds or more
D: 0.5 seconds or more
Pump control function when the machine travels
For details, see FUNCTION OF ENGINE AND PUMP COMBINED CONTROL SYSTEM.
Travel junction function
• This function judges if the operation is for straight travel or for steering by detecting the pilot pressure when
the travel lever is operated.
• In the straight travel operation, signals are sent to the travel junction solenoid valve to set the flow rates to
the right and left travel motors to almost the same level to prevent travel deviation and improve the straight
travel performance.
• In the steering operation, signals to the travel junction solenoid valve are blocked to set the flow rates to the
right and left travel motors independently to improve the travel performance during steering.
PC500LC-10R
Lo (Low speed)
2
2
TRAVEL CONTROL SYSTEM DIAGRAM
Mi (Mid-range speed)
90 %
Maximum
3.0 km/h
2
} or higher for 0.5 seconds or more, the motor
Hi (High speed)
80 %
Minimum
4.2 km/h
2
} or less for 0.5 seconds or more,
100 %
Minimum
5.5 km/h
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