6
. HYDRAULIC SYSTEM
6-
3-1
3
6
-3-4
Swing
1) Right Swing
(1) Pilot oil flow
When the swing control lever is moved to the right, the
oil from the pilot pump P3 flows through the port A of the
cut-off valve and the port 2 of the pilot valve (LH) to the
port b9 of the swing section to move its spool.
(2) Oil flow from hydraulic pump
The oil from the piston pump P2 flows through the port
P2 of the inlet section, the parallel passage and the port
B9 of the swing section to the port A of the brake valve,
so that the swing motor is rotated.
The return oil from the port B of the brake valve flows
back to the hydraulic oil tank through the port A9 of the
swing section, the port T of the control valve and the
return filter.
2) Left Swing
(1) Pilot oil flow
When the swing control lever is moved to the left, the oil
from the pilot pump P3 flows through the port A of the
cut-off valve and the port 4 of the pilot valve (LH) to the
port a9 of the swing section to move its spool.
(2) Oil flow from hydraulic pump
The oil flows in the opposite direction to the oil flow in the
right swing operation with regard to the swing motor.
3) Swing Motor Hydraulic Brake Operation
When the swing control lever is released (i.e., returned
to the neutral position), the oil flow to the swing motor is
blocked and the pressures at the ports A and B of the
brake valve become equal and consequently the brake
is applied. However, the swing motor continues to rotate
through inertia in a short time. This causes the motor to
act like a pump and increase the circuit pressure on the
port B side in case of rotation for the right swing opera-
tion. The brake valve is of a shockless type. The
increased pressure opens the relief valve SR1 to let the
oil on the higher pressure side escape to the line on the
port A side, so that the circuit pressure is absorbed and
cavitation is prevented on the port A side.
The port T of the swing motor has the drain function and
a circuit which directly takes in the return oil flowing from
the port T of the control valve to the hydraulic oil tank to
prevent negative pressure in the swing motor.
Summary of Contents for ViO12-2A
Page 1: ...SERVICE MANUAL EXCAVATOR ViO12 2A...
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Page 109: ...5 3 1 5 ELECTRIC SYSTEM 5 3 Wiring Diagram...
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Page 219: ...6 HYDRAULIC SYSTEM 6 7 8 1 4 3 8 7 12 10 10 15 a b c Loctite 262 0 30Nm 0 45Nm...
Page 348: ...7 ADJUSTMENT AND REPAIR 7 5 31 6 Control Levers Pilot valves Control valve...
Page 349: ...7 ADJUSTMENT AND REPAIR 7 5 32 7 Upperstructure Implement Bucket cylinder Arm cylinder...
Page 351: ...7 ADJUSTMENT AND REPAIR 7 5 34 9 Undercarriage High speed travel solenoid valve...
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Page 360: ...CHAPTER 8 PERIODIC INSPECTION AND SERVICING 8 1 List of Periodic Inspection and Servicing 8 1...
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Page 364: ...CHAPTER 9 FUEL LUBE OIL AND GREASE RECOMMENDED 9 Fuel Lube Oil and Grease Recommended 9 1...
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Page 406: ...CHAPTER 11 REFERENCE DATA 11 1 Specifications for Attachment 11 1...
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