Komatsu PC58UU-3, Руководство по ремонту

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STRUCTURE, FUNCTION AND MAINTENANCE STANDARD HYDRAULIC PUMP
PC58UU-3
10-25
4. Advantages of double pump system
• Usually, if the machine is steered while it
is travelling, the motor pressure on the
drive side (outside) rises and that on the
driven side (inside) lowers in the double
pump system.
• In an ordinary single pump system, the
pressure compensation valve in the con-
trol valve works and the motor pressure
on the driven side and that on the drive
side are the same, because of the pump's
characteristics.
• That is, the pressure compensation valve
on the driven side is closed to heighten
the pressure on the driven side similarly
to the pressure in the circuit on the drive
side.
• Since the motor pressure on the driven
side in the double pump system is kept
low, lowering of the oil flow in the motor
on the drive side can be prevented.
Accordingly, the engine power is con-
trolled as shown below.
1) When ordinary single pump system is
employed
While the machine is travelling straight:
• Right pressure 9.80 MPa {100 kg/cm²} x
Right oil flow (50.0
llll
/min) + Left pressure
9.80 MPa {100 kg/cm²} x Left oil flow (50.0
llll
/min) = 8.10 kW [11.0 PS] + 8.10 kW [11.0
PS] = 16.2 kW [22.0 PS]
When the machine is steered:
• Right pressure 19.6 MPa {200 kg/cm²} x
Right oil flow (50.0
llll
/min) + Left pressure
9.80 MPa {100 kg/cm²} x Left oil flow (40.0
llll
/min) = 16.2 kW [22.0 PS] + 6.60 kW [9.0
PS] = 22.8 kW [31.0 PS]
Since the pump input horsepower is larger
than the engine horsepower, the PC control is
started (to prevent the engine from stalling):
• Right pressure 19.6 MPa {200 kg/cm²} x
Right oil flow (30.0
llll
/min) + Left pressure
19.6 MPa {200 kg/cm²} x Left oil flow (20.0
llll
/min) = 9.6 kW [13.0 PS] + 6.60 kW [9.0
PS] = 16.2 kW [22.0 PS]
The average of the oil flow on both sides is
lowered from 50.0
llll
/min to 25.0
llll
/min (by
50%).
2) When double pump system is employed:
While the machine is travelling straight:
• Right pressure 9.80 MPa {100 kg/cm²} x
Right oil flow (50.0
llll
/min) + Left pressure
9.80 MPa {100 kg/cm²} x Left oil flow (50.0
llll
/min) = 8.10 kW [11.0 PS] + 8.10 kW [11.0
PS] = 16.2 kW [22.0 PS]
When the machine is steered:
• Right pressure 19.6 MPa {200 kg/cm²} x
Right oil flow (50.0
llll
/min) + Left pressure
4.90 MPa {50.0 kg/cm²} x Left oil flow (40.0
llll
/min) = 16.2 kW [22.0 PS] + 2.90 kW [4.0
PS] = 19.1 kW [26.0 PS]
Since the pump input horsepower is larger
than the engine horsepower, the PC control is
started (to prevent the engine from stalling):
• Right pressure 19.6 MPa {200 kg/cm²} x
Right oil flow (43.0
llll
/min) + Left pressure
4.90 MPa {50 kg/cm²} x Left oil flow (33.0
llll
/min) = 14.0 kW [19.0 PS] + 2.20 kW [3.0
PS] = 16.2 kW [22.0 PS]
The average of the oil flow on both sides is
lowered from 50.0
llll
/min to 38.0
llll
/min (by
24%).
When the machine is steered, the oil flow is
lowered by 50% in the ordinary single pump
system but lowered only by 24% in the dou-
ble pump system.