Komatsu Galeo PC800-8 Shop Manual page 798

SEN00794-02
1. Combination and operation of hydraulic
pumps
• For the work equipment and travel and swing cir-
cuit, 1 tandem pump (HPV375+375) is used.
• The oil from the front pump flows in the left 5-
spool control valve and the oil from the rear
pump flows in the right 4-spool control valve.
• The deliveries of the front pump and rear pump
are controlled with the EPC solenoid valves in-
stalled to them respectively.
• The pump controller calculates the signals from
the differential pressure sensor installed to the
left 5-spool control valve and outputs them to the
front pump EPC solenoid to carry out the NC
control of the front pump.
• The pump controller calculates the signals from
the differential pressure sensor installed to the
right 4-spool control valve and outputs them to
the rear pump EPC solenoid to carry out the NC
control of the rear pump.
• The pump controller calculates the signals from
both pump pressure sensors (front and rear) and
outputs them to the front and rear pump EPC so-
lenoid to carry out the equal horsepower control
and cut-off control.
2. Judgment of cause of trouble that "work
equipment speed is low and machine devi-
ates to left"
• The possible causes of this trouble are as fol-
lows;
1) Defective main relief valve of left 5-spool
control valve
2) Defective jet sensor of left 5-spool control
valve
3) Defective differential pressure sensor of left
5-spool control valve
4) Defective EPC solenoid valve of front pump
5) Defective servo valve of front pump
6) Defective front pump unit
• At this time, the main relief valve can be checked
by measuring the relief pressure, the jet sensor
can be checked by measuring the differential
pressure, and the differential pressure sensor
can be checked by measuring the output voltage.
• The pump EPC solenoid valve can be checked
by measuring its output pressure.
• The servo valve and pump unit can be judged by
removing and testing the servo valve or measur-
ing the stroke of the servo piston.
a Actually, perform the judgment procedure
according to "4. Judgment matrix for trouble that
work equipment speed is low and machine devi-
ates".
4
3. Judgment of cause of trouble that "work
equipment speed is low and machine devi-
ates to right"
• The possible causes of this trouble are as fol-
lows;
1) Defective main relief valve of right 4-spool
control valve
2) Defective jet sensor of right 4-spool control
valve
3) Defective differential pressure sensor of
right 4-spool control valve
4) Defective EPC solenoid valve of rear pump
5) Defective servo valve of rear pump
6) Defective rear pump unit
• At this time, the main relief valve can be checked
by measuring the relief pressure, the jet sensor
can be checked by measuring the differential
pressure, and the differential pressure sensor
can be checked by measuring the output voltage.
• The pump EPC solenoid valve can be checked
by measuring its output pressure.
• The servo valve and pump unit can be judged by
removing and testing the servo valve or measur-
ing the stroke of the servo piston.
a Actually, perform the judgment procedure
according to "4. Judgment matrix for trouble that
work equipment speed is low and machine devi-
ates".
4. Judgment matrix for trouble that work equip-
ment speed is low and machine deviates
(next page)
a Carry out troubleshootings in order from the top
one. Select the item having the most marks of q
as the cause of the trouble.
1) To check the servo valve, remove and test it or
measure the stroke of the servo piston.
a The servo piston unit shall be tested in a
specified service shop.
2) If the speed lowers largely and the pump seems
to have a trouble, check the line filter, too.
3) If the speed does not lower largely and cannot
be corrected by adjusting each component,
check the line filter, too.
4) To check the operation of the servo piston,
remove the caps from both sides and move the
piston by hand.
40 Troubleshooting
PC800, 850-8