Komatsu Galeo PC138US-8 Shop Manual page 279

10 Structure, function and maintenance standard
Function
Travel speed select function
1. Travel speed "Manual" change
Turning the travel speed selector switch
q
"Hi" and "Lo" changes the motor capacity
and allows the machine to select travel
speed.
Travel speed selector switch
Motor capacity (cc/rev.)
Travel speed (km/h)
Travel motor swash plate angle
2. Travel speed "Automatic" change
1) Automatic selection corresponding to
engine speed
When the engine speed is lowered to
q
below 1,500 rpm with the fuel control
dial, the travel speed changes to "Lo"
automatically.
2) Automatic selection corresponding to
pump discharge pressure
If the travel pressure increases on an
q
uphill with the travel speed selector
switch in "Hi", and the travel hydraulic
pressure exceeding 32.4 MPa {330
kg/cm²} continues for 0.02 seconds or
more, the travel motor capacity is
switched to low speed (corresponds
to "Lo") automatically (the travel
speed switch position is remain "Hi").
If the travel pressure decreases on a
q
f l a t o r d o w n h i l l w i t h l o w s p e e d
(caused by the automatic gear shift-
ing due to high pressure), and the
travel hydraulic pressure below 17.7
MPa {180 kg/cm²} continues for 0.1
seconds or more, the travel motor
capacity is switched back to the set
speed of "Hi" automatically.
PC138US, USLC-8
Lo (low Hi (high
speed) speed)
79.1 44.2
2.9 5.1
Max. Min.
A: 17.7 MPa {180 kg/cm²}
B: 32.4 MPa {330 kg/cm²}
C: Min. 0.1 sec.
D: Min. 0.02 sec.
Pump control function during travel
a See "Pump and engine mutual control func-
tion" for details.
Travel junction function
When the travel lever is operated, detects the
q
pilot pressure and judges whether it is for
straight-travel or for steering.
For straight-travel, a signal is sent to the travel
q
junction solenoid valve, controlling the pump
flow between the right and left to be equal, to
prevent travel deviation and improve straight
line stability.
When steering, the signal to the travel junction
q
solenoid valve is cut-off, separating the pump
flow between the right and left, to improve
steering stability.
SEN02553-01
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