SERV1852_02_TXT2.pdf

SERV1852-02 August 2008

GLOBAL SERVICE LEARNING TECHNICAL PRESENTATION

320D-336D HYDRAULIC EXCAVATORS TIER III ENGINES PILOT HYDRAULIC SYSTEM

Service Training Meeting Guide (STMG)

320D-336D HYDRAULIC EXCAVATORS TIER III ENGINES PILOT HYDRAULIC SYSTEM 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 " '300C' Series Hydraulic Excavators-Electronic Control Systems" 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 SERV2693 SERV2701 KENR6157

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Text Reference Pilot System

TABLE OF CONTENTS INTRODUCTION ........................................................................................................................5 Pilot Manifold .........................................................................................................................9 Hydraulic Activation Lever ..................................................................................................14 Pilot Controls and 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 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. This model is being discontinued. However, the 330D HD HW changed to the 336D HD HW.

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PILOT HYDRAULIC SYSTEM Stick Cylinder Bucket Cylinder Swing Motor

Main Control Valve Group

Pilot Control Valves

Priority Valves

Pilot Manifold

Pilot Pump Fan Motor

Boom Cylinders

Travel Motors

Main Hydraulic Pumps

M Fan Pump

Tank

The Fan Motor and Pump are only used on the 330D and 336E

1

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. NOTE: In the fourth quarter of 2008, the 325D and 330D nomenclature changed. The 325D became the 329D and the 330D became the 336D for most arrangements.

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3 4

1

5

2

2

A gear-type pilot pump (1) provides oil flow to the pilot system. The pilot pump 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. The pilot relief valve limits the pressure in the pilot system. The pilot relief valve setting 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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PILOT SYSTEM FILTER FILTER RELIEF VALVE AND PILOT SYSTEM RELIEF VALVE Pilot System Relief Valve Pilot Filter Relief Valve Pilot System Filter Pilot System Relief Valve

Pilot Filter Relief Valve

Pilot System Filter

SOS

3

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 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 is equal to the pressure setting of the pilot relief valve.

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4 3 1

2

4

Pilot Manifold The pilot manifold is the same as the "300C" pilot manifold. The pilot manifold is accessible by removing the cover plate under 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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PILOT MANIFOLD

LOCKED - HIGH SPEED TRAVEL SWING BRAKE ENGAGED Straight Travel Solenoid

Heavy Lift Solenoid

Pilot Pump

Hydraulic Activation Valve

Pilot Valves

Tank


Travel Motors

Pilot Pump Two Speed Travel Solenoid

Swing Brake Solenoid Hydraulic Activation Valve

Swing Priority Valve

Implement Hydraulic Lockout Solenoid

Check Valve

Swing Brake

5

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 is directed to the swing priority valve, to the two speed travel solenoid valve, and to the 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 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 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 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. In the de-energized position, no pilot oil is available to operate the implements. Pilot oil 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 limit switch is NOT depressed by the control lever. The limit switch is in the OFF position. When hydraulic activation control lever is in the LOCKED position, the hydraulic activation solenoid is NOT energized. The spool is held up by a 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: 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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Text Reference Pilot System Implement Hydraulic Lockout Solenoid

PILOT MANIFOLD

UNLOCKED - SWING BRAKE RELEASED

Tank Hydraulic Activation Valve

Straight Travel Solenoid

Heavy Lift Solenoid

Pilot Pump


Pilot Valves

Pilot Pump

Travel Motors Two Speed Travel Solenoid

Swing Brake Solenoid Hydraulic Activation Valve

Swing Priority Valve

Implement Hydraulic Lockout Solenoid

Check Valve

Swing Brake

6

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 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 through the 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 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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7

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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8

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 LOCKED position.

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HYDRAULIC ACTIVATION LEVER

Hydraulic Activation Lever

Lever

Plunger

Limit Switch

9

A limit switch and plunger are located on a bracket with the hydraulic lockout 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 main control valve group when the hydraulic activation lever is in the LOCKED position.

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4

3

1

8 6 2

5 7

10

9

10

Pilot Controls and Valves Pilot controls in the cab include: - left (1) and right (2) travel pedals - left (3) and right (4) travel levers - auxiliary foot switch (5) (attachment) - straight travel (6) (attachment) - left joystick (7) to control the swing and 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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1

2

11

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 Control (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 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 are activated at the same time, the Machine ECM will energize the straight travel solenoid.

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Travel Pilot Valves

Pilot Manifold Travel Pilot Valves

Stick

Bucket

Swing

OUT

IN

R

L

OPEN

Boom

CLOSE

aR4

DOWN

UP

Resolver Block

Swing/Implement Pressure Switch

aR3

IMPLEMENT PILOT JOYSTICKS

bR3

bR4

bL3

bL2

bL4

aL2

12

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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PILOT CONTROL VALVE SECTION A-A

Pilot Pilot Manifold Manifold

Joystick Plate Plunger Metering Spring Seat Port B

Port A

Return Spring

Return Chamber

A

Spool

Supply Pilot Oil

A

Port A

Port B

13

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 spool down against its spring. Depending on how far the joystick lever is moved, determines how far the 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 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 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 joystick will return to the NEUTRAL position due to the force of the return 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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TRAVEL PILOT CONTROL VALVE Pedal

Rod

Orifice Check Valve

Dampening Piston

Dampening Piston

Pilot Supply

Left

Right

Tank Metering Spring

Spool

Return Spring

Pilot Supply

REV

FWD aL1

bL1

FWD bR1

Travel Pressure Switch (AEC) Travel Valve

REV aR1 Resolver

Travel Valve

14

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 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 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 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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PWM SOLENOID VALVE PWM SIGNAL DECREASE

PWM SIGNAL INCREASE

Solenoid

Plunger Spring

Spring

Tank

Tank

Control Spool

Control Spool

Pilot Oil

Pilot Oil

15

The attachment circuits are controlled by proportional solenoids valves. These valves are also called proportional reducing valve or PRV. The valves receive PWM signals from the Machine ECM to shift energize the solenoid. The amount of current sent from the 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 the solenoid spool shifts 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 to the spool is maintained as it was for the joysticks.

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16

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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Load Check Valve Parallel Feeder Passage

Port A

Port B


CONTROL VALVE FULL SHIFT

Line Relief and Makeup Valve

Pilot Valve or Solenoid

Passage to Next Valve Center Bypass Passage

17

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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18

CONCLUSION This presentation has provided information for the Caterpillar 320D-336D Hydraulic Excavators. This presentation covered the pilot control 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.

SERV1852_02_TXT2.pdf

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