6.
HYDRAULIC SYSTEM
6-
6
-6
3. System Relief Valves
These relief valves are of a balance piston type and also of a cartridge type.
The relief valves are located between the pump port P in each inlet section, and the tank port T in the P2 side inlet
section. They operate as follows :
1) Relief Operation
(1) Pressure oil flows through the inside of the
piston installed in the pressure control
valve (the parent valve) and the throttle B
to the inner chamber A, so that it is filled
with oil. The pressure control valve and the
socket are securely seated, and so are the
socket and the regulating body seat.
(2) When the oil pressure in the port P
reaches the set pressure of the regulating
valve spring, the pressure oil flows through
the piston to the regulating valve to open it.
At this time, the pressure oil passes
through the inside of the piston, the throttle
B, the inner chamber A, the ring-shaped
throttle C and the drill hole D in sequence,
and flows outside the socket to the tank
passage.
(3) When the regulating valve opens, the pres-
sure in the inner chamber A is lowered,
and consequently, the pressure control
valve is opened and the pressure oil in the
port P flows directly to the tank passage
through the drill hole E.
(4) When the pressure in the port P lowers to
less than the set pressure of the regulating valve spring, the regulating valve is pressed on the seat with the
force of the regulating valve spring and the pressure in the inner chamber A becomes equal to that in the port P.
Therefore, the pressure control valve is also pressed on the seat portion of the socket and returned to the origi-
nal state.
Regulating valve spring
Piston
Throttle B
Socket
Regulating valve
Inner chamber A
Pressure control valve
Tank passage
Regulating body seat
P
Drill hole D
Ring-shaped throttle C
Drill hole E
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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