Oper Manual for Retayder Using on DT(WM)

7/30/2019 Oper Manual for Retayder Using on DT(WM)

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1

Chapter for the Air Over Hydraulic Type Brakes

Operation Manual for the Retarder

on Komatsu Dump Trucks

- Chapter for the Air Over Hydraulic Type Brakes -HD255-5/325-6/405-6/785-5/985-5

03-10-22

03-11-28 1 Tanaka

03-12-22 2 Watase

04-01-08 3 Watase

04-01-20 4 Watase


2/18

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- CONTENTS -

I. Regarding the brakes

1. Concepts of the brakes

2. Types of the braking operations and the brakingmechanisms being activated

3. Constructions and movements of the brakes

II. What is a retarder brake ?

1. Basic concept of using the retarder brake

2. What is the way of operating the retarder brake to causeoverheating ?

III. Safer downhill traveling

1. Setting the downhill traveling speed ( = speed stage)

(1) Measurement of the downhill traveling distance andgradient

(2) Calculation of the overall mass of the vehicle

(3) Determination of the permissible maximum speed whenmaking a downhill travel

2. Actual operations (when carrying out the dump truckoperations)

(1) Decelerating the speed to the downhill traveling speed before

reaching the starting point of the downhill inclination.(2) Making the downhill travel at a certain speed after entering

into the downhill inclination

(3) Adjusting the travel speed depending on existence of curves,road surface status and the variation of the gradient

On a road surface with curves On a slipperly road surface In case the downhill gradient varies

IV. Prohibitions when making braking operations1. Do not turn on and off the retarder brake lever frequently.

2. Do not use the service brake frequently.

3. Do not make abrupt operations of the retarder lever.

4. Do not use the retarder brake as a parking brake.

5. Do not accelerate the speed while making a downhill travelby shifting up the speed stage.

6. Do not make a downhill travel setting the shift lever to the

"N" position.

V. Auto retarder operations

1. What is an auto retarder ?

2. Regarding the auto retarder operations

3. Precautions when operating the auto retarder

4. Regarding Komatsu Auto Retarder (for reference)

- 3

- 4

- 5

- 8

- 8

- 10

- 10

- 10

- 11

- 12

- 12

- 13

- 14

- 14

- 14

- 14

- 15

- 15

- 16

- 16

- 16

- 16

- 17

- 17

- 18

- 18


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(Key point)Since the kinetic energy will increase in proportion to the square of the travel speed, the heat (= thermal energy) being

generated when the brake is activated to stop traveling of the vehicle will become proportionally large.

When the travel speed becomes 2 times faster, the thermal energy being

generated when stopping the vehicle will become 4 times more.

* To prevent occurrence of overheating by braking, do not accumulate the thermal energy.

It means that early stage braking is important before the vehicle reaches unnecessarily

higher travel speed.

I. Regarding the brakes 1/5

1.Concepts of the brakesWhen a vehicle is decelerated or stopped by a brake, the "kinetic energy" and the "potential

energy" being possessed by the vehicle will be converted into the "thermal energy" to be

discharged externally, but a portion of thermal energy will not be discharged and will remain

on the vehicle side. To carry out safe operations with less burden to the equipment, it is

important to fully understand the aforementioned fact before starting the operations. Ifsuch operations are carried out under erroneous understandings, equipment will be

damaged and, at the same time, very hazardous circumstances will occur.

In the meantime, functions of the brakes on dump trucks can be broadly categorized into the

following three different functions.

(1) To decelerate or to stop a vehicle in travel.

* While a vehicle is in travel, kinetic energy is

being possessed by the vehicle.

* When the brake is activated, the kinetic energy

will be converted into the thermal energy.

(2)To decelerate or stop a vehicle traveling on a downhill road and acceleration is occurring

by the gravity.When a dump truck travels on a downhill road, by the action of the

gravity, the "potential energy" will be added to the kinetic energy to

further increase the "thermal energy" being generated when decelerating

or stopping

the vehicle as compared with doing so on a level road.

* The "potential energy" is an energy type being accumulated in a

substance because of the existence of the substance at a "certain

position".

(3)To hold a parking vehicle at the position

When storing a vehicle, a brake will be used not to let the vehicle move

( = to hold the vehicle at the position) by external factors. ( = Parking

brake)

At this time, if it is on a level ground, no energy accumulation is occurring

in particular but if it is on an inclined surface, the "potential energy" is

occurring.

Energy

Even when the travel speed is

becoming 2 times faster, theoccurring energy = heat

becomes four times more.

Energy Energy

Energy Energy

The 3 key factors of the kinetic energy: Speed Inclination - (gradient - distance) - Load

Travel speed

"Kinetic energy" will be converted ==> "Thermal energy"


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Fro

nt

Rear

Park

ing

Exhaust

Service brakeTo decelerate to stop

a vehicle in travel at

an optional time

By depressing the

pedal by a foot *

Retarder

brake

To control traveling speed of a

vehicle on a long downhill

road at a certain level

continuously.

By adjustment of

the lever

Parking brake To park a vehicleBy turning ON and

OFF of a switch

EmergencybrakeFor emergency purpose

Exhaust

brake

An auxiliary braking to be used

when a vehicle is traveling on a

downhill road

(Interlocking with the retarder

brake)

By turning ON and OFF of a

switch

(It will be activated when the

accel pedal is released.)

Types of the

braking

operations

Using braking

mechanism

Operating

methodsApplications

2.Types of the braking operations and the braking mechanisms being

activated

Front brake

Parking brake

Rear brake- Oil cooled wet type

multi discs mechanism

is being employed.- Different from the dry

type brake mechanism,

since this mechanism

is being activated

under constant oil

cooling effect, less

abrasion occurs with

the discs.

Exhaust brakeThis is an auxiliary braking to acquire

a braking force by suppression of the

engine revolution.

Braking operations

being conducted on theoperator's seat

- Dry type disc brake

mechanism is being

employed.

- It will be activated incommon with the rear

brake when operating

the service brake.

- To be used when

parking a vehicle.

- To be also usedwhen loading or

dumping the cargo.


By turning ON and

OFF of a switch

*

*

* * *

*

*


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3.Constructions and movements of the brakes

(1) Service brake (foot brake)

* The service brake is to be used when stopping a traveling vehicle

and both of the front brake and the rear brake will be activated.

However, since the front brake is not being equipped with themechanism to cool the structure forcefully, avoid using the service

brake while the vehicle is traveling on a continuous downhill road,

except for emergency cases.

(2) Retarder brake

- Retarder brake is a device to control the travel speed

corresponding to the gradient for safe and efficient

downhill operations of a vehicle.

- The rear brake, which is being equipped with a forced

cooling mechanism, only will be activated.

The braking force can be adjusted by the

pulling extent of the lever.

The vehicle willmake a downhill

travel at a

certain speed.

Retarder

Travel speed of the vehicle

will be accelerated by the

influence of gravity.

SAFE

Without retarder brake

Zing!

DANGEROUS

Brake oil tank

Radiator

LH and RH rear brakes

Engine cooling water circuit

Brake oil cooler

EnginePump

Discs

Plates

Brake oil circuit


With retarder brake


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(When turned off) (When turned on)Retarder lever

ON Activated Activated

ONOFF Released Released

Foot brakeON Activated Activated

OFF Released Released

Accel pedalON Released Released

OFF Released Activated

OFFRetarder lever

foot brake

Accel pedalON&OFF Released Released

Exhaust brake switchTorque converter

lockupOperations

3.Constructions and movements of the brakes (continuation)

(3)Exhaust brake

- While the exhaust brake is

being activated

- Since the butterfly valve

being installed to the exhaust

piping is being opened, theexhaust gas flows smoothly.

- In this case, any power to

resist to the engine revolution

will not occur in particular.

- While the exhaust brake

is being released

- The exhaust brake makes use of the

resistance occurring to the engine

revolution when the flow of exhaust gascoming out from the engine is hindered.

- The exhaust brake will be activated

when the accel pedal is released while

the exhaust brake switch positioned on

the dashboard panel is being turned

"ON".

When the exhaust brake

switch is turned "ON"

- When the accel pedal is

released, the butterfly valve being

installed to the exhaust piping will

be closed.

- Under this status, the exhaustgas coming out from the engine

will not be discharged smoothly

and a large resistance will occur

to the revolution of the engine.

- The exhaust brake is making

use of this resistance.

- Conditions to activate the exhaust brake



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(4)Parking brake

(5)Emergency brake

- The parking brake is to be used when parking a vehicle.

- It is a lever controlled brake being positioned in front of

the operator's seat.- It consists of a separate braking mechanism from the

front brake or the rear brake.

- The emergency brake is to be used at times of emergency

like, for example, when the wheel brake becomes ineffective

by some damage of the foot brake.

- It is controlled by use of a lever being positioned beside the

speed shift lever in front of the operator's seat.

- When the emergency brake is applied, the front brake, therear brake and the parking brake will be activated.

* When the vehicle is stopped by activation of the emergency brake, apply the

chocks to the wheels immediately and be sure to repair the section where the failure

is occurring and readjust the parking brake.


3.Constructions and movements of the brakes (continuation)


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- The retarder will work to let a vehicle make a downhill travel at a certain

speed by converting the potential energy of the vehicle which is working to

let the vehicle travel downhill by the gravity into thermal energy occurring

from friction. (Divergence of thermal energy)

- The retarder thus heated up will be cooled down forcefully by the circulating

oil and the oil will be cooled by the oil cooler.- The revolution rate of the engine will influence the cooling capacity.

In consideration of the above, the important points when using the retarder

brake should be the following three points.

1. Do not accumulate the thermal energy. ( = Let the retarder diverge the thermal energy efficiently.)

2. Do not generate excessive thermal energy. ( = By operations always in an earlier stage.)

3. Let the retarder diverge the thermal energy efficiently. ( = Maximize the cooling capacity of thedevice.)

Heat

generation

Cooling

effect

Entering into a

downhill road with

an excess load

Thermal energy

being generated by

deceleration of the

vehicle upto the

starting point of a

downhill inclination

Thermal energy

being generated

by downhill

travel of a

vehicle

- Downhill travel with an excess loadA large quantity of

thermal energy will

be generated by the

excess load.

! Key point

The thermal energy being generated by braking will increase in proportion to the overall weight of the

vehicle.Therefore: "When the overall weight of the vehicle becomes 1.2 times more, the thermal energy beinggenerated by braking will also become 1.2 times more."

Now, to prevent occurrence of overheating, it is necessary to suppress the thermal energy exceeding thecooling capacity to the minimum. It means, it is important not to load a vehicles excessively.

Do not load

excessively !

Heat

HeatHeat

Furthermore, the thermal energy

being generated while making a

downhill travel with an excess

load will be quite large.

(2)The way of operating a vehicle to accumulate the thermal energy

Thermal energy being

generated by deceleration

of the vehicle upto the

starting point of a downhill

inclination

Thermal energy

being generated

by the downhill

travel

- Making a downhill travel at a speed exceeding

the cooling capacity

If the vehicle makes a downhill travel at a speed exceeding the cooling capacity of the vehicle, accumulating a

large quantity of thermal energy, overheating will occur.

Make a downhill

travel at anappropriate speed.

Heat

Making a downhill travel at a speed

exceeding the cooling capacity to

accumulate the thermal energy

Heat

Deceleration

Cooling

effect>Heat

Heat

(3)The way of operating a vehicle not to let the vehicle exhibit its cooling capacity sufficiently

Thermal energy being

generated by

deceleration of the

vehicle upto the starting

point of a downhill

inclination Thermal energy being

generated by the downhill

travel

- Making a downhill travel at lower engine revolution rates

Even if generation of the thermal energy may be appropriate, the cooling capacity of the vehicle is being kept at a

low level and overheating will occur.

Make a downhill

travel at appropriate

engine revolution

rates.

Since the engine revolution is low, the

vehicle cannot exhibit its cooling

capacity sufficiently.

Heat

Deceleration

Cooling

effect>HeatHeat

Heat

! Key point

In order to let a vehicle exhibit its cooling capacity to the maximum, "maintain the engine revolution at 1,800 to2,200rpm".

Deceleration

II. What is a retarder brake ? 2/2


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SupplementsContents of the operations

(1)Measurement of the downhill traveling distance

and gradient

(2)Calculation of the overall mass of the vehicle

*The mass of the vehicle

includes the mass of all the

equipment being installed to

the vehicle like, body liner,

various options, etc.

Setting the downhill traveling speed ( = speed stage)

To calculate the downhill traveling speed, measure the

distance of the downhill traveling range and the gradient.

When making measurement, a distance of more than 30m

should be regarded as one block.

Calculate the permissible maximum speed at

which overheat will not be occurring and, also,

calculate the optimum speed stage to shift to.

For that purpose, it is important to check the

status of the downhill road before entering into

the downhill travel and to know the actual

vehicle status (the mass under the maximum

load).

Calculate the overall mass of the vehicle while making a

downhill travel.

Overall mass of the vehicle = Mass of the vehicle* + Mass of

the load

Block "1 - 2"

Block "2 - 3"

Distance (m)Downhill gradient (%)

The equation of conversion from the angle ( ) togradient (%): Gradient (%) = sin A downhill product should be indicated in a minus figure.

An example: Traveling range measurement data

100m

400m

3.0 => 5.2%

4.0 => 7.0%

For example, in case of an HD465-7 with a load of

46.0t with additional 6.0t of the body liner:

Overall mass of the vehicle = Mass of theempty vehicle 43.7t + Mass of the load 46.0t +Operator 0.75t + Options and others 9.0t =98.775t

(Dump truck traveling range measurement drawing)

* Regarding how to cope with the cases where gradient

variations exceeding 30m occur, refer to the Section "Travel

speed adjustment corresponding to curves, road surface state

and gradient variations" being indicated on page 11.

Step(1)Check the status of

the downhill road

before entering into

the downhill travel.

Distance of the

downhill road

Gradient of the

downhill road

Step(2)Check the

specifications of thevehicle.

Overall weight of

the vehicle

Step(3)Calculate the

followings by use

of the results of

the above Step 1

and Step 2.

Downhill

traveling speed

Speed stage

Flow of setting the downhill traveling speed

If a vehicle makes a downhill travel exceeding the

specified limit of the overall mass of the vehicle, the

bearable limit of the vehicle will be exceeded to

cause overheating and other failures and, moreover,

the traveling safety will also be influenced.

Therefore, be sure to restrict the setting within the

specified limit of the overall mass of the vehicle.

If you have any question regarding the

setting of the downhill traveling speed and

the speed stage, contact a Komatsu agent

in your neighborhood.

Dumping Area

Loading Area 1 0 m

2 100m

3 500m

4 1900m

5 3100m

6 3500m

7 3800m

4 deg.

4 deg.

1.5deg.

2 deg.

Dumping Area

Loading Area 1 0 m

2 100m

3 500m

4 1900m

5 3100m

6 3500m

7 3800m

4 de

g.

4 deg.

1.5deg.

2 deg.

3deg.

Gradient

Distance

Block

Make out a layout drawing of the course for the dump truck

to travel on as shown in the drawing indicated on the RH

side and determine the optimum downhill traveling speed

and speed stage to use for each gradient range so that an

efficient traveling plan may be completed.

III. Safer downhill traveling 1/5


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(1)

(2)

(3)

(4)


Performance curve of the retarder

For selection of the permissible maximum speed

and the speed stage when making a downhill travel,

the following two methods can be used.

(Determine the actual travel speed to employ in

considerations of other factors like the road surface

state, curves, road width, visibility, etc.)

For example, in case of operating a dump truck ofmodel HD465-7, for the downhill traveling distanceof 600m, with the traveling resistance (the gradient

resistance of -13% and the rolling resistance of 2%)and with the overall mass of the vehicle of 98,775kg

Use the brake performance graph for the downhill travelingdistance of 600m. Assuming the scale point corresponding to the overall massof the vehicle as , draw a perpendicular line from the point downward. Assuming the point of intersection of the aboveperpendicular line with the traveling resistance of -11% ( = thegradient resistance of -13% + the rolling resistance of 2%) as, draw a horizontal line from the point . Assuming the point of intersection of the above horizontalline with the performance curve as , draw a perpendicularline from the point and assume the point of intersection ofthe above perpendicular line with the vehicle travel speed scaleas . By the above, the permissible maximum speed will become

40kg/h as per the point and the optimum speed stage willbecome "F5" as per the point .

Guideline for selection of the downhill traveling

speed using the retarder (A simplified table)

Appropriate speed stage and traveling speed can be

selected from the downhill traveling distance and gradient

using the simplified table indicated below.

(3)Determination of the permissible maximum speed

when making a downhill travel

On the basis of the distance, gradient and overall mass

of the vehicle calculated as per the above Sections (1)

and (2), determine the permissible maximum speed

when making the downhill travel using the "Simplified

table of the guideline for selection of the downhill

traveling speed using the retarder" or the "

Performance curve of the retarder" indicated above.

600m -13%

For example, in case of operating a dump truck of model HD465-7, the permissible

maximum speed when making a downhill travel for a vehicle of the overall mass of

98,775kg will become

Overall weight of the vehicle

98,775 kgEmpty vehicle w eight 43,700 kg

Operator 75 kgOpt ions and others 9,000 kg

Weight of the load 46,000 kg

Tire size 24.00-35

Transmission Continuous downhill 600m downhill Upper limit travel

speed stage road Gradient (%) road Gradient (%) speed (km/h)

F1 20.8 - 28.4 24.2 - 31.9 11.4

F2 16.0 - 20.8 19.4 - 24.2 16.2

F3 12.3 - 16.0 15.8 - 19.4 21.8

F4 9.6 - 12.3 13.1 - 15.8 29.5

F5 7.7 - 9.6 11.1 - 13.1 39.8

F6 6.2 - 7.7 9.7 - 11.1 53.9

F7 0 - 6.2 0 - 9.7 72.6-The gradient has be en calculated on assum ption of 2% of the rolling resistance.

-Since the r oad surface resistance w ill influence and, also, there can be cases

wher e the retarder m ay be turned off temporarily, refer to the Section

"Brake pe rformance gr aph" in the Operation and Maintenance Manual for details.

When making a downhill travel using the retarder, operate the retarder lever s o

that the engine re volution rate m ay be kept w ithin the range of 1,800 to 2,200rpm

to keep the r etarder oil temper ature gauge indication under 120 C.

In case the retarder oil tempe rature gauge indication exceeds 120 C,

lower the travel sped by shifting down the speed stage, etc.

The engine re volution should not exceed 2,450rpm.

Guideline for selection of the dow nhill traveling speed using the re tarder

Vehicle model: HD465-7

In the above case, the optimum speed stage becomes"F5" and the upper limit downhill travel speed becomes"39.8km/H".*since the vehicle weight and the specifications arebeing regarded as the same, use these selections onthe simplified table as the reference values whendetermining actual travel speed to employ.

600m (%) (%) (km/h)F5 7.7 9. 11.1 13.1 39.8F5 7.7 - 9.6 11.1 - 13.1 39.8

For example, in case of operating a dumptruck of model HD465-7:for the downhill traveling distance: 600mon the traveling road gradient: -13%

with the overall weight of the vehicle:98,775kg,The appropriate downhill traveling speedand the optimum speed stage can beselected using the table indicated on theLH side of this page.

If you have any question regarding thesetting of the downhill traveling speed and

the speed stage, contact a Komatsu agent

in your neighborhood.


Transmission

speed stage

Continuous downhill

road Gradient (%)

600m downhill road

Gradient (%)Upper limit travelspeed (km/h)

Distance Downhill gradient Permissible maximum speed (Optimum speed stage)

Block "A" 40km/h ("F5")


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- Before reaching the starting point of the downhill inclination,

release the accel pedal and operate the retarder lever to

decelerate the speed to the preset downhill traveling speed.


Frequent ON-OFF operations of the

retarder lever when making a downhill

travel

=> Large braking force will be producedintermittently and overheating may occur.

(1) Decelerating the speed to the downhill traveling

speed before reaching the starting point of the downhill

inclination.

Keep the shift lever at the "D" range.(When the travel speed is decelerated to the preset

downhill traveling speed, automatic shift down will

be made to the optimum speed stage.)

Travelspeed

0

Actual travel

speed

Deceleration

Preset downhill

traveling speed

Keep the shift lever

at the "D" range.

- Confirm the preset downhill traveling speed and

the speed stage on the shift indicator on the

Operator's seat panel.Confirm the

preset downhill

traveling speed.

Confirm the preset

speed stage.

Abrupt operation of the retarder lever

=> is dangerous since the tires may slip.

Operate the retarder lever slowly and

at an earlier stage.

=> Refer to the Section "Prohibitions

when making brake operations".

Do not make frequent ON-OFF

operations of the retarder lever when

making a downhill travel.



Use of the service brake (foot brake) when

making a downhill travel

=> Since the front wheel discs are not

equipped with the cooling mechanism, the

brake may become ineffective by

overheating.

Do not use service brake (foot brake)when making a downhill travel except

for emergency cases.



Travel speed

Speed stage

Actual operations (when carrying out

the dump truck operations)

-In case downhill traveling at the "F1" speed stage

becomes necessary as the result of surveys of thetraveling road, select the "6" range other than the

"D" range.



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!KEY POINT!

While making a downhill travel, always pay attention to

the retarder oil temperature and the current speed

stage selection.

After entering into the downhill inclination, make the

downhill travel at a certain speed using the retarder

brake.

While making a downhill travel, keep monitoring ofthe retarder oil temperature, engine revolution rate

and the current speed stage selection.

Making a downhill travel while the engine revolution is

at a lower range=> The cooling capacity of the brake oil cooler is

lowered and overheating may occur.

Keep the

retarder oil

temperature

indication within

the green zone.

Maintain the

engine

revolution rate

within the range

of1,800 to

2,200rpm.

Confirm the

current speed

stage selection

on the monitor.

(2)Making the downhill travel at a certain

speed after entering into the downhill

inclination

0

To cool down the disc brake efficiently,

maintain the engine revolution rate within

the range of 1,800 to 2,200rpm.

Optimum range

1800 - 2200rpm

Engine

tachometer (rpm)

- Making a downhill travel at a speed exceeding the

retarder capacity

- Overloading

=> The thermal energy generation will exceed the

cooling capacity to cause overheating.

Zing!

Keep the current travel speed and loading limit.

"Accelerating the speed while making a downhill travel by

shifting up the speed stage" and "making a downhill travel

setting the shift lever to the "N" (neutral) position"

=> The engine revolution comes down and overheating may

occur.

Also, "making a downhill travel setting the shift lever to the "N"

position" is very dangerous since the travel speed of the

vehicle will be accelerated to an uncontrollable range.

- Do not accelerate the speed while making adownhill travel by shifting up the speed stage.

- Do not make a downhill travel setting the shift

lever to the "N" position.

!KEY POINT!

Let us remember how far the retarder

lever should be pulled.

While carrying out a trial

travel of the vehicle, let

us remember how far

the retarder lever was

pulled when the actual

travel speed became

the preset speed.

While making a downhill travel, conduct fine

adjustment of the retarder lever depending on the

variation of the gradient, road surface status,

existence of curves, etc., in order to maintain the

appropriate and safe travel speed.

When the retarder oil temperature gauge indication enters

into the red zone, the caution lamp will turn on and the

alarm will sound. Then, promptly stop the vehicle at a

safe place to cool down the retarder oil temperature.

To cool down the retarder oil temperature, set the shift

lever to the "N" position and keep the engine revolution

rate within the range of 1,800 to 2,200rpm.

90

70

50

()

130

120

110


Travelspeed

Actual travel

speed

Deceleration

Preset downhill

traveling speed


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On a road surface with curves

Pull the retarder lever before entering into acurve to lower the travel speed to a safe

speed range.

On a slipperly road surfaceWhen making a downhill travel on a slipperly road surface like

on a muddy road, wet mud and sand surface road, snowy road,

gravel road, etc., make a trial travel at a speed where tire slips

will not occur and preset a lower travel speed than when the

road surfaces are dried up.

On a slipperly road surface, deviated retarder effect

(unsymmetrical retarder effect) may occur by the fine

difference between the LH side and RH side braking

forces.

To operate the retarder lever midway while the

vehicle is traveling on a curve

=> It is dangerous since the vehicle will slip

sidewise.

In case the downhill gradient varies

How to cope with when the gradient becomes steeper

B. In case a steep gradient continues more than 30m

Preset a new downhill traveling speed corresponding to

the gradient and decelerate the travel speed using the

retarder lever.

How to travel when the gradient becomes more gradua

Adjust the

travel speed

by acceleration

work.

To adjust the travel speed by depressing the

accel pedal after returning the retarder lever in

case a gradual gradient continues for more than

30m

=> It will cause overheating and will also worsen

the per gallon mileage.

Returning the retarder lever, preset a new

downhill traveling speed.

A. In case a gradual gradient returns to the original state

within 30mWhen the gradient becomes gradual, return the retarder lever and depress the accel

pedal to adjust the travel speed at 2,000rpm or more of the engine revolution. Then,

when the gradient returns to the original state, restore the preset speed using the

retarder lever.

B. In case a gradual gradient continues for more than 30m

Preset a new downhill traveling speed corresponding to the

gradient and decelerate the speed using the retarder lever.

Within 30m

To operate the retarder lever abruptly

=> It is dangerous since the tires will slip.

Operate the retarder lever slowly.

=> Refer to the "Prohibitions when making

braking operations".

Make sufficient decelerationbefore the vehicle enters into

the curved road.

(3)Adjusting the travel speed depending on

existence of curves, road surface status and the

variation of the gradient

Decelerate the

travel speed

using theretarder lever.

A.In case the gradient is returning to the original state

within 30m

Decelerate the travel speed using the retarder lever when the

gradient becomes steeper and return the retarder lever to the

original position when the gradient returns to the original

state to restore the preset travel speed.

Within 30m

Return the retarder

lever to the original

position when the

gradient returns to

the original state torestore the preset

travel speed.

When the gradient

returns to the

original state,

decelerate to restore

the preset speed

using the retarder

lever.



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15



2. Do not use the service brake frequently.

- While making a downhill travel, do not use the service

brake frequently except for emergencies.

- Since the front brake is not equipped with forced cooling

mechanism, frequent use of service brake while making a

downhill travel will cause overheating to reduce the braking

effect extremely and it is very dangerous to use the service

brake frequently while making a downhill travel. Also, early

stage wears of related parts will occur.

- Make it a rule to use the retarder brake when making

ordinary downhill travels.

1. Do not turn on and off the retarder brake lever

frequently.

- Do not turn on and off the retarder brake lever frequently

while making a downhill travel.

Retarder oil

temperature

(C)

Working time

- If the retarder lever is turned on and off frequently,

heat generation by decelerations will increase and,

also, since the engine revolution drops, the brake

oil cooling capacity will decrease to cause

overheating in an earlier stage.

If the retarder brake is turned on and off frequently,

the brake oil temperature also will rise and drop

repetitively and effective cooling cannot be

expected.

3. Do not make abrupt operations of the retarder

lever.

- Do not make abrupt operations of the retarder lever and

operate it gradually and in an earlier stage.

- Also, it may cause tire slips. Moreover, it may result in

generation of excessive thermal energy.

Abrupt operation of the retarder lever

=> The tires will slip and it will be very dangerous.

(Failure examples by frequent use of the service brake)The service brake was used frequently while making

downhill travels. Then, not only the braking effect has

been decreased extraordinarily, but also the brake parts

of the vehicle have been damaged greatly.

Piston

Brake pad

With the front brake, the braking force is being acquired by

the friction force occurring when the piston pushes the brake

pad onto the brake disc. However, when the service brakeis used frequently while making downhill travels, holes will

open in the brake pad finally and the piston will then push the

disc directly. In this state, necessary braking force cannot

be acquired and it will be very dangerous to drive a vehicle

with holes in the brake pad.

Brake pad (New parts)

IV. Prohibitions when making braking operations 1/2


16/18

16



When the retarder oil temperature gauge

indication enters into the red zone, the caution

lamp will turn on and the alarm will sound.

Then, promptly stop the vehicle at a safe place

to cool down the retarder oil temperature.

To cool down the retarder oil temperature, set

the shift lever to the "N" position and keep the

engine revolution rate at 2,000rpm or more.

4.Do not use the retarder brake as a

parking brake.

When you leave the vehicle, be sure to apply the parking

brake. In case of the retarder brake, if it is used as a

parking brake, the air may leak out and the vehicle may

start moving.

Chocks

-When parking the vehicle on an inclined place

from necessity, turn on the parking brake and,

after that, apply chocks to the front wheels.

5. Do not accelerate the speed while making a downhill travel

by shifting up the speed stage.

- If the travel speed is accelerated while making a downhill travel

by shifting up the speed stage, the engine revolution will drop and

sufficient cooling capacity for the retarder cannot be obtained.Therefore, adjust the travel speed while making a downhill travel

by use of the retarder lever.

Retarder

brake disc

Brake

oil

cooler

Oil tank

The flow rate of the retarder oil

into the oil cooler will be

decreased.

The engine revolution will drop and sufficient

cooling capacity for the retarder cannot be obtained

and overheating may occur.

6. Do not make a downhill travel setting the shift lever to

the "N" position.

- If the shift lever is set to the "N" position while making a

downhill travel, the engine revolution will drop and sufficientcooling capacity for the retarder cannot be obtained.

Also, if the shift lever is set to the "N" position while making

a downhill travel, the travel speed of the vehicle will be

accelerated to an uncontrollable range and very dangerous.

RELEASE

IV. Prohibitions when making braking operations 2/2

LOCK

During the summer season when theatmospheric temperature is high, since the

heat balance of the retarder oil will become

worsened corresponding to the atmospheric

temperature, operate the retarder brake in an

earlier stage.

(Operation of the retarder brake always in an

earlier stage will be more effective.)


17/18

17


1. What is an auto retarder ?

Auto retarder is a system which functions to adjust the retarder brake effects automatically so

that the operator may be able to complete a downhill travel at a certain speed preset freely by

the operator. When the auto retarder is used, it becomes unnecessary to operate the retarder

lever and the operator can concentrate to the steering wheel operations, thus improving thetraveling safety. Set the auto retarder to the speed at this point. => After setting, the vehicle will make a

downhill travel at a certain speed.

(It becomes unnecessary to operate the retarder lever to adjust the travel speed and the

operator can concentrate to the steering wheel operations.)

Atacertainspeed

Atacertainspeed

Atacertainspeed

2. Regarding the auto retarder operations

Regarding the auto retarder operations, when the travel speed reaches the preset

downhill traveling while the vehicle is making a downhill travel with the "Auto Retarder

Switch " positioned on the dashboard panel being turned ON, make the "setting

operation" of the "Auto Retarder Setting

Switch " to activate the system.

(Features of Komatsu Auto Retarder)With Komatsu Auto Retarder (ARSC), since

the travel speed settings can be made freely

using the switch being installed to the

steering column and, also, since the preset

travel speed will be indicated in the upper

section of the panel, it is very easy to use and

quick to check the current setting for the

convenience of the operator of the dump truck

equipped with Komatsu Auto Retarder.

- Even if speed stage setting error is made,

there will be no fear of"occurrence of engine

overrun or of seizure of the brake disc by

excessive load". (Even when the presetspeed is exceeding the maximum speed stage

of the current shift lever position, the retarder

brake will be activated before overrun occurs

by the function of the overrun preventive

function. In the meantime, there will be no

possibility of application of excessive load to

the brake at that time.)

The auto retarder will maintain

a certain downhill traveling

speed automatically even when

the gradient changes.

When the auto retarder is used, it becomes possible to make downhill travels at a stable travel

speed and the overall downhill traveling

speed will be increased and the cycle time

for the dump truck will be shortened as the

result.

Furthermore, since the vehicle will make

downhill travels at a stable travel speed,

cooling of the retarder oil will be carriedout efficiently and overheating will not

occur frequently.

(Refer to the diagram indicated on

the RH side.)

Acceleration

Deceleration

(1) ARSC

system switch ReleaseSet

Temperature variation of the cooling oil for the auto retarder and manual retarder

60

80

100

120

140

Overheating

C

Regarding the actual operations of the auto retarder, carefully read its instruction manual.

Overheating

V. Auto retarder operations (an optional equipment) 1/2

Manual retarder

(2) ARSCsetting lever

(4)CAUTION lamp (Red)

(5)READY lamp (Green)

(3)Preset travel speed indication


18/18


4. Regarding Komatsu Auto Retarder (for reference)

With the Komatsu's Auto Retarder System (ARSC), it is possible to set the travel speed

freely within the range of 10 to 55km/h. Also, it is possible to make fine adjustment of

the once preset downhill traveling speed within the range of 5km/h.

On the other hand, with the competing model, it is not possible to make settings at theoptional speed. (The downhill traveling speed is to be selected by positioning of the

shift lever.)

Also, it is not possible to make fine adjustments after presetting the downhill traveling

speed.

Comparisons of the basic functions of the auto retarder systems

(Komatsu's system and the competing model)

3. Precautions when operating the auto retarder

- Even when making a downhill travel by use of the auto retarder, it is necessary to carry out the

measurement work of the traveling course in advance. Using the measurement results, select the

downhill traveling speed corresponding to the performance of the vehicle to carry out the operation of the

dump truck. The engine revolution rate at that time should be 1,800rpm or more.- If a setting is made to a travel speed exceeding the permissible maximum speed when making downhill

travels which can be obtained from the brake performance graph, overheating may occur to damage the

retarder brake and it is dangerous to make such a setting. Be sure to set the travel speed within the range

not exceeding the permissible maximum speed when making downhill travels.

(When "Overheat caution" is issued while using the auto retarder, the travel speed is exceeding the

permissible maximum speed and pull the retarder lever promptly to decelerate the travel speed and make

the proper setting once again.)

- On slippery road surfaces, the tires may lock while the auto retarder is in operation. In these cases,

stop using the auto retarder.

- If an abnormality occurs in the system and when it becomes unfeasible to carry out proper controls, the

system operation will be turned "OFF" at the same time as issuance of an alarm and the auto retarder willthen be released. When necessary, control the vehicle speed using the retarder control lever and brake

pedal to park at a safe plate and turn "OFF" the auto retarder switch .

V. Auto retarder operations (an optional equipment) 2/2

Komatsu Competing model

Control method Travel speed control Engine revolution control

Operating methods

- Turn ON the ARSC system sw itch.

- Af ter entering into the dow nhill road, adjust the dow nhill

traveling speed using the retarder brake and w hen the actual

speed reaches an appropriate level, push the set s w itch.

- Af ter that, the retarder brake w ill be activated automatically

so that the preset trav el speed may be maintained.

- The above setting w ill be released w hen the accel pedal is

depressed or w hen the lever sw itch is moved tow ard the

releasing direction.

- Since the travel speed s ettings w ill be stored in the memory, it

is not necessary to make settings each time w hen making

dow nhill travels of the same dow nhill road.

- Turn ON the ARSC sw itch ON the dashboard

panel.

- Carry out gear shifts to match the gradient of the

dow nhill road to descend.

- w hen the vehicles enters into the dow nhill road,

release the accel pedal. Automatic controls w ill

be car ried out to maintain the engine revolution at

the proper level automatically. an orange indicator

ON the panel w ill Turn on.

- w hen releasing the control, activate the accel

pedal, brake or manual lever.

- the sw itch is NORMALLY ON and the sys tem is

ready for operation any time.

(it is necessary to make the positioning change of

the shift lever each time.)

Travel speed setting

It is possible to make the setting to optional travel speed. Also,by moving the sw itch up and dow n, it is poss ible to make Also,

it is possible to make fine adjustment of the once preset

dow nhill traveling speed (w ithin the range of

5km/h) eas ily.

Since the dow nhill traveling speed is selected bypositioning of the shift lever, it is not possible to

make travel s peed settings optionally.

Confirmation of the settings

Since the preset trav el speed w ill be indicated on the display in

the upper section of the panel, it is very easy to c heck the

current setting.

Since the current shif t lever position w ill not be

indicated on the panel, it becomes necessary to

make visual confirmation of the current shift lever

position.

Overheating alarm

The alarm w ill be issued in assumption of occu rrence of

overheating detecting the extent of the rise of the retarder oil

temperature.

The ordinary over heating alarm w ill be issued.

Documents

Oper Manual for Retayder Using on DT(WM)