SERV1852_02_TXT8

SERV1852-02October 2008

320D-336D HYDRAULIC EXCAVATORS -TIER III ENGINESDEMAND FAN SYSTEMS

Service Training Meeting Guide(STMG)

GLOBAL SERVICE LEARNING

TECHNICAL PRESENTATION

320D-336D HYDRAULIC EXCAVATORS -TIER III ENGINESDEMAND FAN SYSTEMS

AUDIENCELevel II - Service personnel who understand the principles of machine systems operation,diagnostic equipment, and procedures for testing and adjusting.

CONTENTThis presentation provides an introduction and describes the components and systems operationof the 320D-336D hydraulic excavator demand fan systems. Additional presentations willcover the machine walkaround, engines, pilot system, main control valve group, implements,swing system, travel system, and tool control systems in more detail. This presentation may beused for self-paced and self-directed training.

OBJECTIVESAfter learning the information in this presentation, the technician will be able to:

1. identify the correct operation of the demand fan systems used on the 300D Serieshydraulic excavators for engine cooling, and

2. diagnose problems in the fan systems.

REFERENCES320D Hydraulic Excavator Specalog AEHQ5856323D L and 323D LN Hydraulic Excavators HEHH3327324D Hydraulic Excavator Specalog AEHQ5663325D Hydraulic Excavator Specalog AEHQ5665328D Hydraulic Excavator Specalog AEHQ5706330D Hydraulic Excavator Specalog AEHQ5667Machine Monitoring System - Systems Operation RENR8068Self-study "300D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators SERV7032iTIM " '300C' Series Hydraulic Excavators-Electronic Control Systems" SERV2693iTIM "325C Hydraulic Excavators-Hydraulic Systems" SERV2701325D Hydraulic Schematic KENR6157

Estimated Time: 1 HourIllustrations: 41Form: SERV1852-02Date: September 2008

© 2008 Caterpillar

TABLE OF CONTENTS

INTRODUCTION ........................................................................................................................5

HYDRAULIC DEMAND FAN SYSTEM...................................................................................6Cat ET Screens for the Hydraulic Cooling Demand Fan.....................................................19Monitor Screens for the Hydraulic Cooling Demand Fan ...................................................20

VISCONIC DEMAND FAN SYSTEM (ATTACHMENT).......................................................33Cat ET Screens for the Visconic Cooling Demand Fan .......................................................46Monitor Screens for the Visconic Cooling Demand Fan .....................................................51

CONCLUSION...........................................................................................................................52

SERV1852-02 - 3 - Text Reference10/01 Demand Fan Systems


PREREQUISITES"Fundamentals of Mobile Hydraulics Self Study Course" TEMV3002"Fundamentals of Power Train Self Study Course" TEMV3003"Fundamentals of Electrical Systems Self Study Course" TEMV3004"Fundamentals of Engines Self Study Course" TEMV3001

NOTES

Nomenclature Change: During the fourth quarter of 2008, the 325D and 330Dnomenclature changed. The 325D became the 329D and the 330D became the 336D formost 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.


INTRODUCTION

There are two types of demand systems used on the 320D-336D Hydraulic Excavator to controlthe cooling fan for the engine:

- Hydraulic demand fan system (330D/336D Only): The hydraulic demand fan system ismade up of a fan motor and fan pump to cool the hydraulic oil, engine radiator, fuelcooler, and the ATAAC. A reversing fan attachment is available for the hydraulic demandfan system.

- Visconic demand fan system (320D, 321D, 323D, 324D, 325D, 328D and 329D): Thevisconic demand fan system uses a viscous coupling between the engine mounted, beltdriven fan drive hub and the fan assembly.

NOTE: The cooling fan viscous coupling is sometimes called the fan clutch. A fanclutch is a thermostatically-controlled device. When the engine is cool or even atnormal operating temperature, the fan clutch partially disengages the engine'smechanically-driven cooling fan. This decoupling saves power since the engine doesnot have to fully drive the fan.

If engine temperature rises above the fan clutch's engagement temperature setting, thefan becomes fully engaged, When the fan clutch is fully engaged, the fan draws ahigher volume of ambient air through the radiator, which in turn serves to maintain orlower the engine coolant temperature to an acceptable level.

1

320D - 336D EXCAVATORS - TIER III ENGINESDEMAND FAN SYSTEMS

© 2008 Caterpillar


2

HYDRAULIC DEMAND FAN SYSTEM

The hydraulic demand fan system is made up of a fan motor and fan pump to cool the hydraulicoil, engine radiator, fuel cooler, and the ATAAC.

The electronically controlled, variable displacement, piston fan pump is driven off of the mainhydraulic system drive pump. The fan pump flow output is controlled by the angle of theswashplate.

A solenoid on the fan pump receives a PWM signal from the Machine ECM to control thepump swashplate.

When the machine is running, the hydraulic oil temperature sender and the engine coolanttemperature sensor sends signals to the Engine ECM. The Engine ECM then sends thisinformation to the Machine ECM. The Machine ECM picks up the hydraulic temperaturethrough the monitor.

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The Machine ECMs interpret the information from these inputs to send a PWM signal to thefan pump solenoid to control the angle of the pump swashplate to control the pump flow.

A higher temperature input will cause the Machine ECM to send a reduced PWM signal to thefan pump solenoid. The reduced signal causes the pump to upstroke to increase pump flow,which increases the speed of the fan for more cooling capacity.


3

The variable displacement fan pump is driven off of the drive pump, which is part of the mainpump group (2).

The pump control valve group (3) features a pressure control solenoid (4), which is controlledby the Engine ECM.

The pump control valve group has two adjustment screws:

- The upper screw, next to the pump control solenoid, is below the cap (5). This screw isused to adjust the pump control spool.

- The lower screw (6), below the pump control valve group, is used to adjust the pressurecontrol spool.

The reservoir supply line (7) is below the fan pump housing, while the pump supply line (8) tothe motor is above the housing.

NOTE: In most cases, the two adjustment screws should not be used. The solenoid canbe calibrated through Cat ET or the monitor to correctly set the fan pump control.

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The 330D/336D engine fan (1) is hydraulically driven by a fixed displacement motor (2).

The variable displacement fan pump supplies oil to rotate the fan motor. Fan speed is varied toprovide optimized cooling. The optimum fan speed is calculated using engine coolanttemperature and hydraulic oil temperature.

Case drain oil from the fan motor is combined with the case drain oil from the swing and travelmotors. Return oil from the fan motor is sent to the return filters and into the hydraulic tank.

An internal makeup valve in the fan motor is used to prevent cavitation when flow from the fanpump stops.

The direction of the engine fan can be reversed on machines equipped with the reversible fanoption. The fan motor rotation can be changed with the monitor. The reversal of the fan motoris used to clear debris and dust from the radiator and hydraulic oil cooler.

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The radiator access compartment is located in front of the counterweight. The door is hingedon the right and has a locking latch on the left side to keep it closed. This door provides accessfor cleaning some of the cooling system components as servicing some of the fuel system andcooling system components.

- hydraulic oil cooler (1)

- Air to Air After Cooler (ATAAC) (2)

- radiator (3)

- engine coolant overflow bottle (4)

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This illustration is a schematic of the fan system with the fan at maximum controlled pressure,resulting in maximum controlled fan speed.

The hydraulic demand fan is standard on the 330D/336D Hydraulic Excavators. The fan is partof the hydraulic system, but it is controlled by the Machine ECM.

The intake manifold air temperature sensor and the coolant temperature sensor are inputs intothe Engine ECM. The Engine ECM provides information to the Machine ECM from these twosensors. The Machine ECM also receives information from hydraulic temperature sensorthrough the monitor.

The Machine ECM evaluates these three sensor inputs for controlling the fan. A target speedfor the cooling fan is assigned for each engine speed based on the output of the varioustemperature sensors. The target values for the maximum fan speeds are assigned by specificsoftware designed for the 330D/336D machine models.

The Machine ECM sends a PWM signal to the fan pump proportional solenoid to control theflow from the pump. The pump flow is directed to the fan motor, to rotate the motor, whichcauses the fan to turn to provide engine cooling.

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When engine coolant and/or hydraulic oil temperatures are high, the fan speed is increased. Ifthe temperatures are low, the fan speed is decreased. The higher the ambient temperature, thehigher the fan speed, as well.

For high temperature readings the Machine ECM sends the minimum software controlled PWMsignal to the fan pump pressure control solenoid to upstroke the hydraulic pump to increase thepump flow.

When maximum pump flow is sent to the fan motor, the fan rotates at the maximum softwarecontrolled rpm.

Cat ET or the monitor can be used to check or calibrate the fan speed. Refer to the 330D/336DTest and Adjust Manual for the calibration procedures.

Maximum mechanical pump pressure and maximum fan speed (high pressure cut-off) can beachieved by disconnecting the electrical connection to the solenoid or by using Cat ET to turnOFF the fan control (Engine ECM/Configuration screen).

If communication is lost between the Engine ECM and the fan pump pressure control solenoid,the fan will default to the maximum mechanical pressure setting (high pressure cutoff). Thisaction results in a higher system pressure. This pressure is higher than the maximum pressurecontrolled through the software. The fan speed is also higher than the maximum fan speednormally controlled by the software.

The makeup valve in the fan motor is used to prevent cavitation when flow from the fan pumpstops.


7

The Machine ECM sends the minimum PWM signal (software controlled) to the fan pumppressure control solenoid when conditions require maximum controlled fan speed.

The pressure control spool spring forces the top half of the pressure control spool up, againstthe solenoid pin and holds the lower land of the upper pressure control spool against the seatwhen the solenoid receives the minimum PWM signal.

This movement blocks most of the pump output oil in the pump control spool spring chamberfrom draining to tank through the case drain passage, which causes the pump control spoolspring chamber to become pressurized.

The force of the spring at the top of the pump control spool, plus the pressure of the oil, is nowgreater than the oil pressure at the bottom of the pump control spool. The pump control spoolmoves down, blocking pump output oil from entering the signal passage to the large actuatorpiston in the pump. The large actuator piston is open to drain around the pump control spool.

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The bias spring and the small actuator move the pump swashplate to an increased angle, whichcauses the pump to UPSTROKE. This condition provides a controlled maximum flow of oil tothe fan motor and creates the maximum controlled fan pump system pressure, which results inthe maximum controlled fan speed. If the solenoid fails (no current to the solenoid), the pumpgoes to maximum displacement.

With no current to the pressure control solenoid, the pump control spool (high pressure cut-off)will limit the maximum pressure and the fan speed to its maximum rpm. This state can beachieved by disconnecting the fan pump control solenoid or by using Cat ET to turn the fancontrol OFF. This procedure is required when making adjustments to the fan system pressuresettings.

The mechanical high pressure cutoff is adjusted using the adjustment screw. When theadjustment screw is turned in (clockwise), it increases the force of the pressure control spoolspring, which increases the the pump pressure required to unseat the land of the upper pumpcontrol spool, thereby increasing maximum cutoff pressure.

Maximum cutoff pressure will be lowered when the screw is turned out (counter-clockwise).

NOTE: The 330D/336D service manual currently does not provide test procedures forchecking the maximum and minimum fan speeds outside the control of the software.The D8T and D9T Track-type Tractor uses a similar cooling fan system. The D8T andD9T test procedures for checking the maximum and minimum fan speeds can be used asreference, however, the specifications will be different. A tee for a pressure tap will alsohave to be installed in the line to the fan motor.

The pump control spool is also shown as being adjustable. Increasing the spring settingwould create higher system pressures and higher fan speeds for a given PWM signal tothe pressure control solenoid and vice versa for decreasing the spring setting. If thespool is adjusted a pressure control solenoid calibration should be done to compensatefor the change to the pump control spring.


8

This illustration is a schematic of the hydraulic fan system with the fan at minimum speed.

When the Machine ECM sends the maximum software controlled PWM signal to the fan pumppressure control solenoid, the pump destrokes to the minimum swashplate angle. At theminimum swashplate angle the pump produces the minimum controlled flow resulting in thefan turning at the minimum fan speed.

When the fan pump pressure control solenoid is at the maximum software controlled PWMsignal, the pressure control spool is unseated by the solenoid, allowing some of pump supplyoil to drain to the tank. This action reduces the pressure in the spring chamber of the pumpcontrol spool and the pump control spool shifts up due to the higher pump supply pressure.

When the pump control spool moves up, pump flow is directed to the large actuator. Aspressure builds in the large actuator, the large actuator overcomes the bias spring and the smallactuator piston to the destroke pump. With the pump destroked, oil flow to the fan motor isreduced which reduces the fan speed.

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This illustration shows the fan control valve with the fan pump at minimum displacement.

If the input temperatures are below a certain value, the Machine ECM sends an increased PWMsignal to the pressure control solenoid to reduce the pump flow. The solenoid plunger and pinpush the pressure control spool down.

With the pressure control spool pushed down, the spring chamber above the pump control spoolis open to case drain around the seat on the lower end of the upper pressure control spool.

There is a pressure drop across the orifice above the pump control spool. The system pressureis now greater than the pump control spool spring and the pressure above the pump controlspool. The supply pressure pushes the pump control spool up to block oil in the signal passageto the actuator piston from going to drain.

The pump control spool now allows pump supply oil to flow to the large actuator piston. Theflow causes an increase in pressure in the large actuator piston. The large actuator overcomesthe combined forces of the bias spring and small actuator to move the swashplate towardminimum angle. Pump flow decreases and therefore fan speed decreases.

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With cold oil or at cold start-ups, the Machine ECM PWM signal to the pressure controlsolenoid is at the maximum. The pump control spool moves up and supply pressure is sent tothe large actuator piston to move the swashplatetoward minimum angle. The large actuatorstops moving when the vent hole through the large actuator piston is open to case drain. Thepump flow is decreased to minimum to reduce the fan speed to minimum.

10

On machines equipped with the reversing fan attachment, the Machine ECM also controls thereversing fan solenoid valve.

A bi-directional fan motor will replace the standard fan motor with the reversing fan feature.Operation of the fan pump and motor makeup valve is as previously discussed.

The Machine ECM will automatically activate the fan reversing solenoid valve atpredetermined intervals, if the machine is equipped with the optional reversing fan. Fanreversing duration may be re-configured using Cat ET or through the monitor.

When the reversing solenoid valve is energized, pilot oil is directed to the reversing spool. Thereversing spool shifts causing the flow of oil to the fan motor to be reversed. The fan motorrotates in the opposite direction.

The relief valve opens momentarily whenever there are any pressure spikes in the system. Therelief valve also opens when the fan is first commanded to change directions (either reverse orforward). The momentum of the fan prevents the fan motor from immediate directional changewhen the flow of oil is reversed. The relief valve helps dissipate excess pressure that maydamage the system during a directional change.

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Cat ET Screens for the Hydraulic Cooling Demand Fan

Using Cat ET, the status of the fan control system can be monitored.

The system status information can be helpful when troubleshooting the cooling system.


12

After connecting Cat ET, go to the configuration screens.

Under Machine Control, open up the Machine Attachments parameters to view the four coolingfan parameters.

The Engine Cooling Map parameter can be changed on all machines, but is not recommended.This parameter requires special factory passwords to change the parameter.

If the machine is equipped with a reversing fan then the Engine Reversing Feature InstallationStatus and the Engine Reverse Operation Time can also be changed.

The Engine Reversing Feature Installation Status is used to change from "Installed" to"Disabled or Not Installed."

The Engine Reverse Operation Time allows for changing the length of time the fan reversesduring a reversing cycle.


13

Through Cat ET, one of four different cooling fan maps can be selected. The cooling maps arecontrolled by software.

The fan maps were created to allow the factories the capability to select the fan map best suitedfor the marketing region each machine was being shipped to.

From the factory the 330D/336D models for NACD are only and should ONLY be configuredto High Ambient.

330D/336D machines for EAME are configured to High Ambient Temperature + Low Noiseand ISJ machines are configured to Standard + Low Noise.

The Standard cooling map is currently not being used by any of the factories.

Factory passwords are required to change the cooling fan map for the 330D/336D.

NOTE: The technician should never be required to change the cooling map. Thisparameter is for factory use only. At the first release of the 330D the software did allowthe technician to change the cooling map without a factory password, but new softwarewas sent out to prevent this from happening.


14

The configuration screen allows the technician to change from "Installed" to "Not Installed" forreversing feature for the cooling fan.

If a reversing fan attachment is not installed on the machine, changing this parameter will haveno affect on the fan operation.

On machines equipped with a reversing fan attachment, this parameter allows the technician toturn off the reversing feature if required.


15

On the Override Parameter screen there are three cooling fan parameters that can be overridden.

Parameter overrides can be used to perform various system tests that may or not be found in theService Manual.

One suggested use for the Engine Coolant Fan Sol Current Override is to enter a value of 0% todetermine the maximum mechanical system pressure and 100% to determine the minimumpressure. These two values are not part of one any of the fan cooling maps.

NOTE: The 330D/336D service manual currently does not provide test procedures forchecking the maximum and minimum fan speeds outside the control of the software.The D8T Track-type Tractor uses a similar cooling fan system. The D8T test proceduresfor checking the maximum and minimum fan speeds can be used as reference, however,the specifications will be different. A tee for a pressure tap will also have to be installedin the line to the fan motor.


16

To begin the cooling fan solenoid calibration, open up the Calibration menu under Service andSelect and select "Engine Cooling Fan Calibrations.

The fan speed calibration consist of four stages:

- standby

- minimum fan speed calibration

- maximum fan speed calibration

- finish or "succeeded"


17

The above screen shows the standby state.

Follow the directions on each screen as it appears. After the conditions are met, select "Next."


18

This screen shows the minimum fan speed calibration being performed.

To adjust the current to the solenoid, click on the arrows below the Proportional ReducingValve Adjustment Command bar.

- Select the right button to increase the current to the fan pressure reducing valve (PRV)solenoid to reduce the fan speed.

- Select the left button to decrease the current to the pressure reducing valve (PRV)solenoid to increase the fan speed.


19

This screen shows the maximum fan speed calibration being performed.

To adjust the current to the solenoid, click on the arrows below the Proportional ReducingValve Adjustment Command bar.

As the current changes, the engine rpm will change as previously discussed.


20

If the calibration was successful, "Success" will appear in the pop-up window. The technicianthen selects "Finish" to complete the calibration of the fan solenoid valve.

If the calibration was unsuccessful, "Failed" will appear in the pop-up window and thecalibration should be started over.


21

Monitor Screens for the Hydraulic Cooling Demand Fan

Calibrations of the hydraulic demand fan can be done through the monitor. From the Servicesub-menu screen select Calibrations. From the Calibrations sub-menu screen select Fan Speed.

The fan speed calibration consist of four stages:

- standby

- minimum fan speed calibration

- maximum fan speed calibration

- finish or "succeeded"

Before calibration, the technician needs to place a strip of reflective tape on the fan blade, and,setup the 9U-7400 Multitach II Group in order to read the fan speed. Do not use a phototach.The calibration must be done with the machine set at speed dial "10" and the AEC turned off.

Then access the monitor to perform the calibration & press the buttons to increase or decreasethe fan speed until it reaches the specified speed. Fan calibration is required when an ECM,fan control solenoid, fan motor, or fan pump has been replaced.

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Three parameter overrides are provided for the hydraulic demand fan.

These overrides are used to conduct system tests. These tests may or may not be covered in theservice manual.

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Both types of fan systems can be equipped with a reversing fan option.

The operation time of the reversing fan can be varied through the Service Menu. For theService Menu a password is required. From the Service Menu, the Maintenance Menu can beaccessed.

Through the Maintenance Menu, the reversing fan can be turned ON or OFF. There is noseparate switch in the cab to control the reversing fan.

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24

The length of time the fan reverses can be varied through the Service Menu.

From the Service Menu (not shown) select the Configuration Menu. From the ConfigurationMenu select the Parameter Settings Menu.

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VISCONIC DEMAND FAN SYSTEM (ATTACHMENT)

The 320D-329D Hydraulic Excavators can be equipped with an electronically controlled,viscous coupled demand fan. The speed of the engine cooling fan is controlled by the EngineECM in relation to engine coolant temperature, inlet manifold air temperature, and hydraulicfluid temperature.

A viscous coupling fan clutch is used between the engine mounted, belt driven fan drive huband the fan assembly. Inside the visconic coupling, a high viscosity, temperature stable, siliconfluid provides a means of coupling and uncoupling the fan to the fan input hub.

When the machine is running, the hydraulic oil temperature sender and the engine coolanttemperature sensor sends signals to the Engine ECM. The Engine ECM then sends thisinformation to the Machine ECM. The Machine ECM picks up the hydraulic temperaturethrough the monitor.

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The Machine ECMs interpret the information from these inputs to send a PWM signal to thefan electronic control solenoid to control the demand fan clutch.

A higher temperature input will the Machine ECM to send a reduced PWM signal to the fanelectronic control solenoid.

The reduced PWM signal causes the fan clutch to move toward full engagement to increase thefan speed for more cooling capacity. With the minimum PWM signal the fan will turn at theengine speed.

NOTE: The following illustrations show the fan clutch is various stages of disassembly.These components are not serviced separately. The clutch is serviced only as a unit.

26

The illustration above shows the flow path of the silicon fluid through the visconic fan driveassembly as well as identifies the major components. The components will be explained inmore detail later in this presentation.

The fan solenoid does not rotate with the fan blade or fan drive assembly. The fan is bolted tothe fan drive assembly.

The input plate is driven at engine speed.

The silicon fluid flows from the fluid reservoir through the open fluid control valve and entersthe working chamber through the fill hole. The silicon fluid travels through the concentricrings of the working chamber causing rotational force from the input plate to be transferred tothe front and rear housings, which causes the fan to rotate.

Depending on the amount of silicon oil in the working chamber, will determine how fast thefan turns.

The centrifugal force of the rotating drive assembly causes the fluid to travel to the outside ofthe working chamber where small passages return the fluid back to the fluid reservoir.

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The upper left illustration shows the viscous fan drive clutch assembly as viewed from theradiator side. The fan electronic control (1) is pressed onto a bearing that is mounted to theradiator side (2) of the visconic drive clutch assembly.

The illustration at the upper right shows the fan electronic control removed from the mountingbearing (2) on the fan drive assembly reservoir cover (3). Visible near the center of theelectronic fan control is the Hall Effect type speed sensor (4).

A ring magnet and bolt (5) are installed in the center of the fan drive front housing. Themagnet and bolt are fixed to the main aluminum body and rotate at the same speed as the fandrive assembly.

The ring magnet and bolt components produce six pulses per revolution of the fan driveassembly relative to the stationary Hall effect speed sensor. The Hall effect sensor produces asquare wave speed signal as the six points of the bolt head rotate within the electronic control.

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The fan fluid control valve and armature (6) and the fluid reservoir chamber (7) can be seen inthe lower left illustration. The fan fluid control valve is part of the reservoir cover and the fluidreservoir chamber is part of the front (fan side) housing (8).

The lower right illustration shows the rear (engine side), housing assembly (9) of the viscousdrive and the front (fan side) housing (8) (flipped over). A series of concentric rings in eachdrive housing form the fluid paths of the visconic drive.

28

The engine side fan drive housing assembly consists of rear (or engine side) housing (1) and aninput plate (2), which is pressed onto the input hub shaft (3).

The concentric rings (4) machined into the input plate nearly fill the space (5) (red circle)between the concentric rings of the front and rear housings. (The front housing concentricrings are not shown).

A high viscosity silicon fluid is used to fill the gaps between the concentric rings and providesthe rotational torque (internal drag) needed to turn the fan blade. The close tolerance of theconcentric rings and the high viscosity of the silicon fluid act similar to the turbine and impellersections of most torque converters.

The rotation of the input plate provides a rotating force to the front and rear drive housings.


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An electro-magnetic rotary fluid control valve is used to control the flow of the visconic fluidwithin the visconic drive assembly. The electro-magnetic valve is part of the aluminum fluidreservoir chamber cover (1) in the front drive housing. The upper illustration shows the fluidvalve in the closed (default) position. The steel electro-magnetic fluid valve armature (2)rotates within the fluid reservoir cover.

Maximum rotation of the armature is controlled by the stop pin (3) pressed into the cover. Areturn spring (4) is used to keep the armature in the closed (default) position. A stainless steelvalve arm (5) opens or closes the large fluid passage in the fluid reservoir depending on theposition of the fluid valve armature.

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Eight iron bars (6) are cast into each of the castelations of the aluminum reservoir cover. Theseiron bars act as "opposite poles" to the electro-magnetic fluid control valve armature when amagnetic flux is applied to the armature by the fan control coil.

31

The front (radiator side) housing contains the fluid reservoir chamber and has two fluidpassages leading to the working chamber of the visconic drive. The large passage (1) is openedor closed by the movement of the fluid control valve armature. As the valve armature moves,the valve arm will open or close to allow fluid to the working chamber below the reservoir.

By opening the large passage, more fluid will flow to the working chamber of the visconicdrive, and more rotational torque is transferred from the input plate to the front and rear drivehousings. With the working chamber filled with fluid, the fan will spin at nearly the speed ofthe input hub.

The small passage (2) allows the visconic fluid to flow from the working chamber back to thereservoir.

NOTE: There are two fluid drain passages from the working chamber to the fluidreservoir. Only one drain passage can be seen in the above illustration.


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This illustration shows the inner (working chamber) side of the front housing. The fluid inletpassage (1) from the reservoir allows fluid to enter the working chamber. Centrifugal force ofthe rotating fan drive will cause the fluid to travel outward from the center of the housing andfill the passages of the working chamber.

The small fluid return passages (2) constantly drain the working chamber back to the fluidreservoir. To reduce the fan speed the Engine ECM will increase the current to the coil of theelectronic control and the increased flux will cause the control valve to rotate against the returnspring and close the large fluid passage.

When the large fluid passage is closed by the fluid control valve, the remaining fluid in theworking chamber will drain back to the reservoir through the small drain passages and the fanspeed will decrease.


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The above illustration shows the electrical control coil (1) and the Hall Effect speed sensor (2)of the fan control. The electronic control coil (shown here installed upside down) is pressedonto a bearing (not visible) on the fluid reservoir cover (3).

The Engine ECM supplies a variable current to the electrical coil. The strength of the electricalcurrent increases or decreases the strength of the flux on the rotary fluid control valve. A highcurrent will induce a strong magnet flux through the rotary fluid valve armature and cause it torotate to the closed position.

The Hall Effect speed sensor uses the six points of the hexagon head retaining bolt (4) as areluctor. The retaining bolt spins at fan blade speed while the electronic control coil remainsstationary. The bolt heads provide six pulses to the Hall Effect sensor for each revolution ofthe fan hub. The square wave output signal from the Hall Effect sensor is monitored by theEngine ECM to determine fan speed.


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The intake manifold air temperature sensor and the coolant temperature sensor are inputs intothe Engine ECM. The Engine ECM provides information to the Machine ECM from these twosensors. The Machine ECM also receives information from hydraulic temperature sensorthrough the monitor.

Based on the values of these sensors the Machine ECM will vary the amount of current to thefan electronic control coil.

As the current to the fan control coil is increased, increased magnetic flux produces a rotationalmovement to the fluid control valve armature. As the fluid control valve rotates, the valve armcloses the large hole in the fluid reservoir allowing less fluid to flow into the working chamberof the visconic fan clutch. The increase in magnetic flux to the fluid valve armature causes thearmature to rotate as the outer blades of the armature try to align with the steel bars in thereservoir cover.

The spring under the fluid valve armature opposes the rotation of the armature and counterbalances the armature's rotation.

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As the armature rotates towards the steel bars, the stainless steel valve arm closes the largefluid passage in the fluid reservoir of the front housing. Completely closing the fluid passagein the front cover will allow a minimum amount of the visconic fluid to flow into the workingchamber of the drive assembly and minimum fan speed.

If a low or no current condition is present in the fan electronic control, the armature returnspring will rotate the armature blades away from the steel bars and the valve arm will open thelarge passage of the fluid reservoir resulting in maximum fan speed.

A fan speed map within the software of the Engine ECM will compare temperature sensorreadings with the desired fan speed map and plot target fan speed according to engine rpm andcurrent fan speed.

If only one sensor is reporting a high temperature, or need for increased cooling, the ECM willreduce the current to the fan control coil by a predetermined percentage of the fan speed mapand the fan speed will increase.

The Engine ECM monitors the speed of the fan blade by use of a Hall Effect type sensor builtinto the center of the electronic fan control. A ring magnet and bolt is installed in the driveassembly at the center of the fan control coil. The ring magnet and bolt will rotate at fan speedand provide an input to the speed sensor. The fan speed sensor is supplied with a 5 voltreference signal and returns a square wave frequency signal to the Engine ECM.

If no fan speed signal is supplied to the Engine ECM by the fan speed sensor the fan willdefault to maximum fan speed.

35

Cat ET Screens for the Visconic Cooling Demand Fan

Using Cat ET, the status of the fan control system can be monitored.

The system status information can be helpful when troubleshooting the cooling system.

NOTE: The 320D-329D excavators are not currently available with a reversing fan.The reversing fan solenoid parameter should always show as not installed.


36

After connecting Cat ET, go to the configuration screens.

Under Machine Control, open up the Machine Attachments parameters to view the four coolingfan parameters.

The Engine Cooling Map parameter can be changed on all machines. This parameter doesrequire special factory passwords in order to change the parameter.

NOTE: The 320D-329D excavators are not currently available with a reversing fan.The parameters related to the reversing fan should be disregarded.


37

Through Cat ET, one of four different cooling fan maps can be selected.

From the factory the 320D-329D machines for NACD are only and should ONLY beconfigured to High Ambient.

330D/336D machines for EAME are configured to High Ambient Temperature + Low Noiseand ISJ machines are configured to Standard + Low Noise.

The Standard cooling map is currently not being used by any of the factories.

Factory passwords are required to change the cooling fan map.

NOTE: The technician should never be required to change the cooling map. Thisparameter is for factory use only.


38

To obtain factory passwords go to https://fps.cat.com.

NOTE: The passwords above will only work with the machine serial number shown.


39

On the Override Parameter screen there are three cooling fan parameters that can be overridden.

Parameter overrides can be used to perform various system tests that may or not be found in theService Manual.

NOTE: The 320D-329D excavators are not currently available with a reversing fan.The parameter related to the reversing fan solenoid should be disregarded.


40

Monitor Screens for the Visconic Cooling Demand Fan

From the Service sub-menu the Override sub-menu and the Calibration sub-menu can bedisplayed.

In the Override screen, overrides for the fan can be selected.

The two fan motor overrides are used to perform system tests. These tests may or may not becovered in the service manual.

From the Calibration sub-menu, fan calibrations can be selected. Visconic fan calibration iscurrently non-functional.

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41

CONCLUSION

This presentation has provided information for the 300D Series Caterpillar HydraulicExcavators.

This section of the presentation covered the demand fans for the engine cooling systems.

When used in conjunction with the service manual, the information in this package shouldpermit 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 andMaintenance Manual, Service Manuals, and other related service publications.


SERV1852_02_TXT8

Documents

hydraulic cooling demand

d series hydraulic excavators

d hydraulic excavators

visconic cooling demand

d serieshydraulic excavators

systems operationof

tool control systems

pilot system