SERV1852-02 August 2008
GLOBAL GLO BAL SER SERVIC VICE E LEARNI LEARNING NG TECHNICAL PRESENT PRESENTA ATION
320D-336D HYDRAULIC EXCAVATORS TIER III ENGINES PILOT PILO T HYDR HYDRAULIC AULIC SYSTE SYSTEM M
Service Training Meeting Guide (STMG)
320D-336D HYDRAULIC EXCAVATORS TIER TI ER II IIII EN ENGI GINE NES S PILOT HYDRA HYDRAULIC ULIC SYST SYSTEM EM AUDIENCE Level II - Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.
CONTENT This presentation provides an introduction and describes the components and systems operation of the 320D-336D pilot hydraulic system. Additional presentations will cover the machine walkaround, engines, pumps and controls, main control valve group, swing system, travel system, and tool control systems in more detail. This presentation may be used for self-paced and self-directed training.
OBJECTIVES After learning the information in this presentation, the technician will be able to: 1. identify the components and explain the operation of the 320D-336D hydraulic excavators pilot system, and 2. diagnose problems in the pilot system.
REFERENCES 320D Hydraulic Excavator Specalog 324D Hydraulic Excavator Specalog 325D Hydraulic Excavator Specalog 328D Hydraulic Excavator Specalog 330D Hydraulic Excavator Specalog Machine Monitoring System - Systems Operation Self-study "300D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators iTIM iT IM " '30 '300C 0C'' Se Seri ries es Hy Hydr drau aullic Ex Exca cava vattor orss-E -Ellec ecttro roni nicc Con Conttro roll Sys Systtem ems" s" iTIM "325C Hydraulic Excavators-Hydraulic Systems" 325D Hydraulic Schematic
Estimated Time: 45 minutes Illustrations: 19 Form: SERV1852-02 Date: August 2008 © 2008 Caterpillar
AEHQ5856 AEHQ5663 AEHQ5665 AEHQ5706 AEHQ5667 RENR8068 SERV7032 SER SE RV2 V269 693 3 SERV2701 KENR6157
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TABLE OF CONTE CONTENTS NTS INTRODUCTION ................................................... ....................................................... .....................................................................5 ..............5 Pilot Manifold.........................................................................................................................9 Hydraulic Activation Lever ............................................... ...................................................14 Pilot Controls and Valves Valves .................................................. ..................................................16 CONCLUSION...........................................................................................................................23
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PREREQUISITES "Fundamentals of Mobile Hydraulics Self Study Course" "Fundamentals of Power Train Self Study Course" "Fundamentals of Electrical Systems Self Study Course" "Fundamentals of Engines Self Study Course"
TEMV3002 TEMV3003 TEMV3004 TEMV3001
NOTES Nomenclature Change: During the fourth quarter quarter of 2008, the 325D and 330D nomenclature changed. The 325D became the 329D and the 330D became the 336D for most arrangements. The exceptions are as follows: - The nomenclature for the 325D MH and 330D MH did not change. - The nomenclature for the 325D FM and 330D FM did not change. - The 325D HD HW did not change into 329D HD HW. HW. This model is being discontinued. However,, the 330D HD HW changed to the 336D HD HW. However HW.
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INTRODUCTION
The oil delivered from the pilot pump performs the following main functions: - Provides pilot oil pressure to the pilot control valves for implements, swing, and travel in order to perform machine operations. - Provides pilot pressure oil in order to control the output flows of the main pumps. - Provides pilot pressure oil 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: - pilot control valve circuit
- power shift pressure system
- pressure switch circuits
- straight travel valve circuit
- swing parking brake
- boom priority
- swing priority
- automatic travel speed change
- heavy lift setting of the main relief valve
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This section of the presentation will cover the focus on the pilot manifold, the implement joysticks (pilot valves), and the travel pilot valves. va lves. NOTE: In the fourth quarter of 2008, the 325D and 330D nomencla nomenclature ture changed. changed. The 325D became the 329D and the 330D became the 336D for most arrangements.
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A gear-type pilot pump (1) provides oil flow to to the pilot system. system. The pilot pump is is mechanically connected to the drive pump. The oil delivery from the pilot pump flows through the pilot oil filter (2) and into the components in the pilot system. Pilot relief valve (3) is located on the mounting base for the pilot oil filter. filter. The pilot relief valve limits the pressure in in the pilot system. The pilot relief valve setting is is adjustable. Pilot system pressure can be checked at the test port (4) on the right side of the filter base. Next to the pilot pressure test port is the hydraulic system S•O•S port (5).
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The filter element in the pilot oil filter removes contaminants from the pilot oil. If the pilot oil is extremely cold or if the flow of pilot oil through filter element becomes restricted by contaminants, the oil bypasses the filter element through the bypass relief valve. The bypass relief valve is built into the pilot oil filter base. The pilot oil flows from from the pilot pump to inlet port. When the pressure in the pilot oil system reaches the pressure setting of the pilot relief valve, part of the pilot oil flow is returned to the hydraulic tank. The pressure of the pilot system oil in outlet lines lines is equal to the pressure pressure setting of the pilot relief valve.
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Pilot Manifold
The pilot manifold is the same as the "300C" pilot manifold. The pilot manifold is accessible accessible by removing the cover plate under unde r the machine, behind the swing bearing. The manifold is located directly below the main control valve. The hydraulic activation valve (1) and solenoid (2) are located in the pilot manifold along with the swing brake solenoid (3) and the two-speed travel solenoid (4).
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Oil from the pilot pump enters the pilot manifold to be distributed to the various components of the machine. Some of the pilot oil flow flow is directed to the swing swing priority valve, to the two speed speed travel solenoid valve, and to the straight straight travel solenoid valve. The rest of the pilot oil flows through the check valve. Two Speed Travel Solenoid Valve: The two speed travel solenoid valve controls oil flow to the two-speed travel motors. In the illustration above the solenoid is energized. Pilot oil is directed to the travel motors to shift the two displacement displacement change valves (not shown). When the displacement change valves shift, the motors will destroke for higher speed. Check Valve: The pilot manifold also has a check valve. The check valve maintains pilot accumulator pressure in the pilot circuit when the engine is not running. By maintaining the pilot pressure (for a limited time) when the engine is stopped, the implements can be lowered safely to the ground.
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Pilot Accumulator: The pilot accumulator is used to release the swing brake and for lowering the boom and stick in the event of a loss loss of pilot system pressure or a dead engine. The pilot accumulator also helps to dampen pressure spikes in the pilot system, which enhances the stability of the machine control systems.
The accumulator stores pilot pressure pressure oil for use at the main control valves. During some operations, the pilot system needs more oil because there is insufficient flow from the pilot pump. Implement Hydraulic Lockout Solenoid Valve and Hydraulic Activation Valve: These two valves work together to either prevent the implement control valves and the motors from being activated or to allow them to be activated. activated. In the de-energized position, no pilot pilot oil is available to operate the implements. implements. Pilot oil is is blocked at both valves.
When the hydraulic lockout control lever in the cab is in or moved to the LOCKED position, the plunger of the the limit switch switch is NOT depressed by the control lever. The limit switch switch is in the OFF position. When hydraulic activation control lever is in the LOCKED position, the hydraulic activation solenoid soleno id is NOT ener energized. gized. The spool is held up by a spring. spring. The spool blocks the pilot supply oil from going to the pilot valves. The spool also opens a passage to drain from the pilot valves to the tank. In the locked position, if the joysticks are moved, the cylinders and the motors cannot be activated. Swing Brake Solenoid Valve: Valve: The swing brake solenoid valve energizes to release the spring applied, hydraulically-released, wet disc swing brake. The swing brake is automatically released when any joystick function is performed by the operator.
When the swing brake solenoid valve de-energized the swing brake is engaged by springs.
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When the hydraulic lockout control lever in the cab is placed in the UNLOCKED position, the limit switch closes the circuit path to the lockout solenoid solenoid valve. The lockout solenoid valve is energized. When the implement hydraulic lockout solenoid valve is energized, pilot oil is directed to move the hydraulic activation valve down. Pilot oil flows flows through the hydraulic hydraulic activation valve to the swing brake solenoid valve, the left and right joysticks (pilot valves), and the travel pilot valves. The hydraulic activation valve also supplies pilot pilot oil for the heavy lift solenoid valve. When an implement is activated the swing brake solenoid is energized by the Machine ECM. Pilot oil is directed through the swing brake solenoid valve to release the swing park brake in the swing motor group.
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The pilot accumulator (arrow) provides pressure oil to the pilot system when the pilot pump flow is low or the pilot pump has stopped. Low pilot oil flow to the pilot system may be caused by the following two reasons: - Implements are lowered while the engine is stopped and oil supply to the main control valves is stopped. - Combined implement, swing, and travel operations.
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Hydraulic Activation Lever
The hydraulic lockout lever (arrow) is shown in the LOCKED position. The engine will not start unless the hydraulic activation lever (3) is in the LOCKED position. Raise the lever activation lever to the UNLOCKED position to energize the implement hydraulic lockout solenoid valve to allow the operator to move the implements. If the machine is running, the operator can lockout the implement controls by returning the lever to the the LOCKED posit position. ion.
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A limit switch and plunger are located on a bracket with the hydraulic lockout lever. lever. When the hydraulic activation control lever is moved forward, the lever pushes the plunger down to activate the limit switch. When the hydraulic lockout control lever is shifted to the rear to the LOCKED position, the implement lockout solenoid valve is NOT energized, so the hydraulic activation valve does NOT shift to direct pilot oil to the pilot control valves. The joysticks and/or travel pedals can NOT shift a control valve in the the main control valve group when the hydraulic activation lever is in the LOCKED position.
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Pilot Controls and Valves
Pilot controls in the cab include: - left (1) and right (2) travel pedals - left left (3) and right right (4) (4) travel levers - auxiliary foot switch (5) (attachment) - straight travel (6) (attachment) - left joystick (7) to control the swing and stick stick (SAE excavator pattern) - right joystick (8) to control the bucket and boom (SAE excavator pattern) - foot rest (9 and 10) The joysticks shown above are equipped with full electronic control for the tool control system. NOTE: The switch for one touch low idle is on the right joystick. If the machine is equipped with a magnet, the trigger switch on the front of the right joystick turns the magnet on, while the trigger switch on the front of the left joystick turns the magnet off.
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The resolver block (1) is located under the cab. The resolver block provides a junction between the pilot lines to the joysticks and the pilot lines to the main control valve group as well as sensing when an an implement or the swing is activated. The resolver network in the block, directs the pilot signal pressure to the swing/implement pressure switch (2) for Automatic Engine Con trol (AEC). Two travel pressure switches (not shown) and the swing/implement pressure switch (2) are activated by pilot pressure oil. The switches close at 490 ± 49 kPa (71 ± 7 psi) and open at 290 ± 0 kPa (42 ± 0 psi). The pressure switches are inputs to the Machine ECM. The Machine ECM uses these inputs to to determine when a hydraulic function has been activated. If Automatic Engine Control (AEC)/one touch low idle is activated and the machine is at low idle the Machine ECM and will increase the engine speed to the current speed dial setting. When only the swing/implement pressure switch is activated, the Machine ECM will release the swing brake. When all three pressure switches switches are activated at the same time, time, the Machine ECM will energize the straight travel solenoid.
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When one or more of the joysticks are shifted, resolvers in the block direct the highest pilot oil pressure to the the swing/implement pressure switch. The Machine ECM will cause the engine to increase rpm to match the speed dial position.
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When the pilot joystick lever is shifted, the joystick contacts the plunger and pushes the plunger down against its spring. The plunger will contact the spool and move the the spool down against its spring. Depending on how far the joystick lever is is moved, determines how far the spool spool moves. As the spool moves down, the spool will close off the drain passage for the oil to the control valve and meter pilot pressure oil to the control valve to cause the control spool (not shown) to shift. The greater the pilot oil flow flow to the control spool, the greater the control spool travel. As pressure increases in the pilot line to the control valve, the pressure moves the spool up to a balance position against the spool and metering springs to maintain a constant pilot pressure in the pilot line. This action will maintain the control spool position in the the control valve until the joystick is moved. In summary, once the pilot joystick is shifted, the pilot valve becomes a pressure reducing valve which maintains a downstream pressure equal to the spring forces above the spool. When the joystick is released, the the joystick will return to to the NEUTRAL position due to the force of the return spring spring moving the spool up. When this action occurs, the pilot oil is blocked by the spool from flowing to the control valve to shift the control spool. Pilot oil at the control spool is drained to the tank past the spool.
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The travel pilot control valve operates similar as the implement pilot valves. Depending on how far the the travel pedal or lever is moved, will determine the amount of pilot oil directed to the respective travel control valve. A dampening function is built into the travel travel pilot control valve which allows the operational speed of the travel lever/pedal to respond only to intended movements of the operators foot. The dampening function also prevents vibration or harshness when releasing the travel pedal. When the travel lever/pedal is moved suddenly suddenly from the NEUTRAL position, the rod is pushed downward. The rod moves the dampening piston downward. The hydraulic oil below the dampening piston is pressurized. An orifice check valve allows the trapped hydraulic oil below the dampening piston to gradually flow into into the metering metering spring chamber, which is open to the tank. The gradual flow of oil through the orifice check valve provides the dampening function.
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The attachment circuits are controlled by proportional proportional solenoids valves. These valves are also called proportional reducing valve or PRV. PRV. The valves receive PWM signals from the Machine ECM to shift shift energize energize the solenoid. solenoid. The amount amount of current current sent from from the Machine Machine ECM will determine how far the solenoid spool shifts. As the solenoid spool shifts, pilot oil is metered from one of the energized solenoid valves to the attachment circuit to control the position of the control spool for the attachment. When the solenoid is de-energized de-energized the solenoid spool shifts to to block the pilot oil. The pilot supply passage to the control spool is open to the tank. NOTE: The solenoid valves also act as variable pressure reducing valves. Instead of using a spring to control the downstream pressure, the current is varied to the solenoid to control the downstream pressure to the control spool. For a fixed current the pilot pressure pres sure to the spool is maintained maintained as it was for the joysticks.
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When the joysticks are operated, the pilot control valves send pilot pump oil through the pilot lines to the pilot ports (arrows) at the main control valve group in order to shift the spools in the main control valve. Additional pilot lines are located below the main control to shift the control spools in the opposite direction.
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Pilot oil enters a control valve from either end to shift the main control spool. The control spool will shift in proportion to the amount of pilot oil sent to the control spool from the a pilot valve or solenoid. For some circuits, proportional solenoid valves are used to direct pilot oil to shift the control spool.
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CONCLUSION
This presentation has provided information for the Caterpillar 320D-336D Hydraulic Excavators. This presentation covered the the pilot control system system and pilot control valves. Additional presentations are available for each system used on these machines. When used in conjunction with the service manual, the information in this package should permit the technician to do a thorough job of analyzing a problem in these systems. For service repairs, adjustments, and maintenance, always refer to the Operation and Maintenance Manual, Service Manuals, and other related service publications.
