Sistema Piloto 325c

7/28/2019 Sistema Piloto 325c

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Cerrar SIS

Pantalla anterior

Producto: EXCAVATOR

Modelo: 325C EXCAVATOR CRB

Configuracin: 325C L & 325C LN Excavator CRB00001-UP (MACHINE) POWERED BY 3126 Engine

Operacin de Sistemas325C Excavator Hydraulic SystemNmero de medio -RENR5364-02 Fecha de publicacin -01/11/2003 Fecha de actualizacin -21/11/2003

i01827505

Pilot Hydraulic System

SMCS - 5050

Illustration 1 g00932427

(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

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(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)

(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 the stick and swing)

(23) Pilot line (pilot oil to pilot control valve for the 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




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(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

(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)




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Ports and solenoids at the pilot manifold

(45) Swing parking brake solenoid valve

(46) Valve (hydraulic activation)

(52) Travel speed solenoid valve

(54) Hydraulic activation solenoid valve

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:

Create pilot oil pressure in order to control the output flows of the main pumps.

Provide pilot oil pressure to the pilot control valves for implements, swing and travel in orderto perform machine operations.

Create pilot oil pressure in order to automatically operate the control devices.

Note: Each pilot circuit performs one of the functions above.

The pilot circuit is classified into the following circuits:

Power shift pressure system

Pilot control valve circuit

Pressure switch circuits




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Straight travel valve circuit

Swing parking brake

Boom priority

Swing priority

Automatic travel speed change

Power Shift Pressure System


(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

(74) Governor actuator




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(75) Engine speed sensor (flywheel housing)

During machine operation, engine and pump controller (68) receives input signals from the followingcomponents:

Engine speed dial (70)

Engine speed sensor (75) that is located on the flywheel housing

Right pump pressure sensor (71)

Left pump pressure sensor (72)

Monitor in the cab (69)

Feedback sensor (73) at governor actuator (74)

The engine and pump controller (68) continually monitors all of the input signals. The input signalsare processed by the engine and pump controller and an output signal is sent to proportional reducingvalve (63) at the right pump regulator. The proportional reducing valve assists in controlling theoutput 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. Thisreduced pressure is called power shift pressure (PS). The proportional reducing valve sends thereduced pilot oil pressure through the right pump regulator and through the left pump regulator. Theoutput flow of right pump (58) and left pump (49) is controlled in accordance with the power shiftpressure. 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 valvewill change when the engine and pump controller detects a change in any of the input signals. Thepower shift pressure that is sent to the regulators at the right pump and the left pump will change inorder to regulate the maximum allowable hydraulic pump output. The desired engine speed ismaintained.

A decrease in engine speed increases the power shift pressure. An increase in power shift pressurecauses destroke condition of the right pump and the left pump. The maximum allowable hydraulicpower 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 hydraulicpower output is increased.

Note: For more information concerning the operation of the engine and pump controller, refer toSystems 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 pilotmanifold (51). When the hydraulic activation control lever is shifted to the UNLOCKED position, theengine 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 nowflows to pilot control valves (5), (25) and (26) for implements, swing and travel in order to perform




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machine operations. When the joysticks and/or travel levers/pedals are moved, the pilot oil flows tomain control valve (11) in order to control the machine functions.


Pilot lines at the main control valve (top view)

When joystick (25) and/or joystick (26) are operated, the pilot control valves send pilot pump oilthrough the pilot lines to pilot ports at the main control valve in order to shift the spools in the maincontrol valve. Refer to Illustration 4 and Table 1 for the location of the pilot lines and machineoperations.

Pilot line Control Valve Machine Operation

(76) Boom I control valve BOOM LOWER

(77) Bucket control valve BUCKET CLOSE

(78) Swing control valve SWING LEFT

(79) Boom II control valve BOOM RAISE

(80) Stick II control valve STICK IN

(81) Right travel control valve REVERSE RIGHT TRAVEL

(82) Left travel control valve REVERSE LEFT TRAVEL

(83) Stick I control valve STICK IN

Table 1

Pilot oil from the pilot control valves flows through pilot lines to the ports on the bottom of the maincontrol valve in order to perform the opposite operation.

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 areaccomplished 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 controlvalve (26) flows through pilot line (37) to boom I control valve (17). The pilot pressure shifts the




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boom I control valve. The oil delivery from the right pump flows to the head end of the boomcylinders 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 controlvalve (26) flows through pilot line (6) to boom I control valve (17). The pilot pressure shifts theboom I control valve. The pilot oil also flows through pilot line (7) in order to open boom driftreduction 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 LOWERoperation is now performed.

Pressure Switch Circuits

Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure switch (40) isconnected to pilot control valve (25) and pilot control valve (26). When all of the joysticks and/ortravel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the pressure switches islow. Pressure switches (19), (21) and (40) are OFF. The engine and pump controller recognizes theOFF condition of all of the pressure switches. The AEC system is activated in order to lower theengine rpm.

If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, theincreased pilot oil pressure is sent to the pressure switches. If pressure switch (19), (21) and/or (40) isON, the engine and pump controller activates the AEC system in order to increase the engine rpm.

Straight Travel Valve Circuit

When a swing operation and/or implement operation is performed during a travel operation, theincrease of pilot pressure in pilot line (39) activates implement/swing pressure switch (40). Theimplement/swing pressure switch sends an electrical signal to the engine and pump controller. Theengine and pump controller energizes straight travel solenoid (13). Pilot pressure now activatesstraight travel control valve (18). The straight travel control valve maintains straight travel eventhough there is a swing operation or an implement operation during travel. For more informationconcerning the operation of the straight travel control valve, refer to Systems Operation, "ControlValve (Straight Travel)".

Swing Parking Brake

When the hydraulic activation control lever is placed in the UNLOCKED position, pilot oil inpassage (57) flows through valve (46) and passage (53) to swing parking brake solenoid valve (45).When any of the joysticks are moved from the NEUTRAL position, the increase of pilot pressure in

pilot line (39) activates implement/swing pressure switch (40). The implement/swing pressure switchsends an electrical signal to the engine and pump controller. An electrical signal from the engine andpump controller energizes the swing parking brake solenoid valve (45). Pilot oil in line (4) flows toswing parking brake (1). This oil releases the swing parking brakes. For more information concerningthe operation of the swing parking brake, refer to Systems Operation, "Pilot Valve (Swing ParkingBrake)".

Boom Priority

During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure in pilot line (36)and pilot line (38) activates the pressure reducing valve for boom priority. The pressure reducing

valve for boom priority allows priority flow to the head end of the boom cylinders during thesecombined hydraulic operations by disabling the stick II control valve. For more informationconcerning the pressure reducing valve for boom priority, refer to Systems Operation, "BoomHydraulic System".




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Swing Priority

During a swing operation, pilot oil flows from pilot control valve (25) to the pressure reducing valvefor swing priority (47). The pressure reducing valve for swing priority shifts. The pilot oil flow inpilot line (42) from pilot oil manifold (51) is blocked by the pressure reducing valve for swingpriority. Most of the left pump delivery flow goes to the swing motor. For more information

concerning the pressure reducing valve for swing priority, refer to Systems Operation, "SwingHydraulic System".

Automatic Travel Speed Change Valve

Pilot oil in passage (56) flows to travel speed solenoid valve (52). When the travel speed switch onthe right console is set at the HIGH SPEED position, the travel speed solenoid valve opens. Thisallows pilot oil to flow through travel speed solenoid valve (52) and through line (41). The oil thenflows to the displacement change valve for the left travel motor (2) and the displacement changevalve for the right travel motor (3). As the displacement change valve operates, the travel speed ismaintained at the HIGH SPEED position.

When the travel speed switch on the right console is set at the HIGH SPEED position, the pressuresensors for the pump delivery pressure control the travel speed in accordance with the travel load. Forexample, low speed during a high load condition and high speed during a low load condition.

For more information concerning the operation of the displacement change valves, refer to SystemsOperation, "Displacement Change Valve".

Copyright 1993 - 2013 Caterpillar Inc.

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Red privada para licenciados del SIS.

Tue Apr 23 15:23:43 UTC+0200 2013


Sistema Piloto 325c

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