Systems Operation

320C U Excavator Hydraulic System

Pilot Hydraulic System
SMCS - 5050
Shutdown SIS

Previous Screen
Product: EXCAVATOR
Model: 320C EXCAVATOR MAC
Configuration: 320C U & 320C LU Excavators
MAC00001-UP (MACHINE) POWERED BY 3066 Engine
Media Number -RENR3845-01 Publication Date -01/12/2002 Date Updated -11/12/2002

i01429693


Illustration 1 g00746497
(1) Swing parking brake
(2) Displacement change valve (left travel motor)
(3) Displacement change valve (right travel motor)
(4) Line (pilot oil from swing parking brake solenoid valve)
(5) Travel pilot control valve
(6) Pilot line (BOOM LOWER)
(7) Pilot line (boom drift reduction valve)
(8) Pilot line (STICK IN)
(9) Pilot line (stick drift reduction valve)
(10) Stick drift reduction valve

(11) Main control valve
(12) Boom drift reduction valve
(13) Solenoid valve (straight travel)
(14) Pilot line (pilot pressure to left travel pressure switch)
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(15) Pilot line (pilot oil to travel pilot control valve)
(16) Right travel control valve
(17) Boom I control valve
(18) Straight travel control valve
(19) Travel pressure switch (left)
(20) Pilot line (pilot pressure to right travel pressure switch)
(21) Travel pressure switch (right)
(22) Pilot line (pilot oil to pilot control valve for stick and swing)
(23) Pilot line (pilot oil to pilot control valve for boom and bucket)
(24) Left travel control valve
(25) Pilot control valve for stick and swing
(26) Pilot control valve for boom and bucket
(27) Variable swing priority valve
(28) Pilot line (STICK OUT)
(29) Pilot line (STICK IN)
(30) Pilot line (SWING RIGHT)
(31) Pilot line (SWING LEFT)
(32) Pilot line (BUCKET CLOSE)
(33) Pilot line (BOOM RAISE)
(34) Pilot line (BOOM LOWER)
(35) Pilot line (BUCKET OPEN)
(36) Pilot line (pilot oil from boom pilot control valve)

(37) Pilot line (BOOM RAISE)
(38) Pilot line (pilot oil to the pressure reducing valve for boom priority)
(39) Pilot line (pilot pressure to implement/swing pressure switch)
(40) Implement/swing pressure switch
(41) Pilot line (pilot pressure to displacement change valves)
(42) Pilot line (pilot oil to pressure reducing valve for swing priority)
(43) Pilot line (pilot oil to pilot control valves)
(44) Pilot line (pilot oil to straight travel control valve)
(45) Swing parking brake solenoid valve
(46) Valve (hydraulic activation)
(47) Pressure reducing valve for swing priority
(48) Pressure reducing valve for boom priority
(49) Left pump
(50) Passage (power shift pressure)
(51) Pilot manifold
(52) Travel speed solenoid valve
(53) Passage
(54) Hydraulic activation solenoid valve
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Pilot Oil Circuit
The pilot circuit pressure is limited by pilot relief valve (64) .
The oil delivery from pilot pump (59) performs the following main functions.
z
Create pilot oil pressure in order to control the output flows of the main pumps.
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Provide pilot oil pressure to the pilot control valves for implements, swing and travel in order to perform machine operations.
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Create pilot oil pressure in order to automatically operate the control devices.
The pilot circuit is classified into the following circuits and each circuit performs one of the above functions.
(55) Passage
(56) Passage
(57) Passage
(58) Right pump
(59) Pilot pump
(60) Pilot line (pilot oil flow to pilot oil manifold)
(61) Pilot filter
(62) Passage (power shift pressure)
(63) Proportional reducing valve (power shift pressure)
(64) Pilot relief valve
(65) Passage
(66) Pilot line (pilot oil flow from pilot pump to pilot oil filter)
(67) Pilot line (pilot oil flow to pump regulators)



Illustration 2 g00748938
Ports and solenoids at pilot manifold
(45) Swing parking brake solenoid valve
(46) Valve (hydraulic activation)
(52) Travel speed solenoid valve
(54) Hydraulic activation solenoid valve

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z

Power shift pressure system
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Pilot control valve circuit
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Pressure switch circuits
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Straight travel valve circuit
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Swing parking brake
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Boom priority
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Swing priority
z
Automatic travel speed change
Power Shift Pressure System


Illustration 3 g00746518
(49) Left pump
(58) Right pump
(63) Proportional reducing valve (PS pressure)
(59) Pilot pump
(68) Engine and pump controller
(69) Monitor
(70) Engine speed dial
(71) Right pump pressure sensor
(72) Left pump pressure sensor
(73) Feedback sensor
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During machine operation, engine and pump controller (68) receives input signals from the following components:
z
Engine speed dial (70)
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Engine speed sensor (75) that is located on the flywheel housing
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Right pump pressure sensor (71)
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Left pump pressure sensor (72)
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Monitor in the cab (69)
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Feedback sensor (73) at governor actuator (74)
The engine and pump controller (68) continually monitors all of the input signals. The input signals are processed by the engine and pump
controller and an output signal is sent to proportional reducing valve (63) at the right pump regulator. The proportional reducing valve assists
in controlling the output flow of right pump (58) and left pump (49) .
The oil delivery from pilot pump (59) flows through the pilot filter to proportional reducing valve (63) at the right pump regulator. The
electrical signal that is sent from engine and pump controller (68) causes proportional reducing valve (63) to regulate the pilot pressure to a
reduced pressure. This reduced pressure is called power shift pressure (PS). The proportional reducing valve sends the reduced pilot oil
pressure through the right pump regulator and through the left pump regulator. The output flow of right pump (58) and left pump (49) is
controlled in accordance with the power shift pressure. The power shift pressure is used to regulate the maximum allowable hydraulic pump
output.
The output signal that is sent from the engine and pump controller to the proportional reducing valve will change when the engine and pump
controller detects a change in any of the input signals. The power shift pressure that is sent to the regulators at the right pump and the left
pump will change in order to regulate the maximum allowable hydraulic pump output. The desired engine speed is maintained.
A decrease in engine speed increases the power shift pressure. An increase in power shift pressure causes destroke condition of the right pump
and the left pump. The maximum allowable hydraulic power output is decreased.

An increase in engine speed decreases the power shift pressure. A decrease in power shift pressure causes an upstroke condition of the right
pump and the left pump. The maximum allowable hydraulic power output is increased.
Note: For more information concerning the operation of the engine and pump controller, refer to Systems Operation/Testing and Adjusting,
"Engine and Pump Electronic Control System".
Pilot Control Valve Circuits
Oil from pilot pump (59) flows through pilot line (66), pilot filter (61) and pilot line (60) to pilot manifold (51). When the hydraulic activation
control lever is shifted to the UNLOCKED position, the engine and pump controller energizes the hydraulic activation solenoid valve (54).
The pilot oil then shifts valve (46). The pilot oil now flows through valve (46) and pilot line (43). The pilot oil now flows to pilot control
valves (5), (25) and (26) for implements, swing and travel in order to perform machine operations. When the joysticks and/or travel
levers/pedals are moved, the pilot oil flows to main control valve (11) in order to control the machine functions.
The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a stick
operation, bucket operation, travel operation and swing operation are accomplished in the same manner as the boom operation.
When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from pilot control valve (26) flows through pilot line (37) to
boom I control valve (17). The pilot pressure shifts the boom I control valve. The oil delivery from the right pump flows to the head end of the
boom cylinders in order to perform the BOOM RAISE operation.
When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (26) flows through pilot line (6) to
boom I control valve (17). The pilot pressure shifts the boom I control valve. The pilot oil also flows through pilot line (7) in order to open
boom drift reduction valve (12). The return oil from the head end of the boom cylinders flows through the boom drift reduction valve and the
boom I control valve to the hydraulic tank. The BOOM LOWER operation is now performed.
Pressure Switch Circuits
Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure switch (40) is connected to pilot control valve (25) and
pilot control valve (26). When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the
pressure switches is low. Pressure switches (19), (21) and (40) are OFF. The engine and pump controller recognizes the OFF condition of all
of the pressure switches. The AEC system is activated in order to lower the engine rpm.
If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, the increased pilot oil pressure is sent to the
pressure switches. If pressure switch (19), (21) and/or (40) is ON, the engine and pump controller activates the AEC system in order to
(74) Governor actuator
(75) Engine speed sensor (flywheel housing)

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