5brake system englisg-g9165

Service Manual of RS8160 Road Roller

5 Brake System

SERVICE MANUAL

Service Manual for G9165 Grader

I

CONTENTS

5 Brake System ....................................................................................................... 5-1

51 Service Brake System .......................................................................................... 5-1

511 System Composition and Working Principle .............................................. 5-1

512 Specification and Technical Description of Main Components ................. 5-3

513 Disassembly and Assembly Single-Circuit Foot Brake Valve ................... 5-9

514 Disassembly and Assembly of Accumulator............................................. 5-11

515 Disassembly and Assembly of Prefill Valve ............................................. 5-13

516 Replacement of Brake Shoe ...................................................................... 5-15

52 Parking Brake System ....................................................................................... 5-19

521 Working Principle of Parking Brake ......................................................... 5-19

522 Disassembly and Assembly of Parking Brake Control Mechanism ......... 5-20

53 Diagnosis and Solutions for Common Faults of Brake System ........................ 5-22

523 Common Fault of Service Brake System .................................................. 5-22

524 Common Fault of Parking Brake System .................................................. 5-24


5-1

5 Brake System

The brake system of this grader consists of service brake system and parking brake system. The

function of service brake system is to realize speed reduction and stop when the vehicle is running

according to the operator’s requirements. The parking brake is used for grader to brake under

emergency conditions during operation or to keep loader stay at original position after stop,

avoiding movement in the effect of inclined road or other external forces.

51 Service Brake System

This machine adopts full hydraulic brake system. It

has advantages of smooth braking, safe and reliable,

simple structure, and convenient maintenance. The

system is designed with drum-type brake.

(Double-circuit service brake system is optional,

when a circuit fails, the other brake circuit can still

carry out braking, which improves the vehicle's

safety).

511 System Composition and

Working Principle

The service brake system is supplied by gear pump.

During driving, the oil from the pump flows into the

accumulator through prefill valve. When the

operator steps on the brake pedal, high pressure oil

stored in accumulator (or from the prefill valve)

splits into two parts, flows into the wheel side

brake cylinders respectively to engage braking.

Meanwhile, the brake lamp switch will be trigged

by pressure oil to turn on the brake lamp. Release

the brake pedal, the pressure oil circuit to the brake

valve will be cut off, and the hydraulic oil in the


5-2

wheel side brake cylinders will return to oil tank

through valve, then the brake will be released and

the brake lamp will be off.

The prefill valve always takes supplying oil to the

accumulator as first priority. The two accumulators

will be charged to set pressure as long as the

engine is running, to guarantee reliable braking.

The brake valve controls the four rear wheel side

brakes through hydraulic circuits, and braking

pressure is determined by the pressure acted on

brake valve.

Fig. 5-1 Composition of service brake system

1 Brake pump 2 Filter 3 Hydraulic oil tank 4 Joint 5 Prefill valve

6 Oil return block 7 Brake valve 8 Accumulator 9 Pressure switch

10 Brake joint block 11 Right wheel side brake 12 Left wheel side brake


5-3

512 Specification and Technical

Description of Main Components

Prefill valve

The prefill can keep the two accumulators at right

pressure. When the pressure of oil in the

accumulators drops to 12.4MPa or below, the

prefill valve will charge them immediately. When

the pressure of oil in the accumulators is charged to

16MPa, the prefill will stop charging.

Prefill valve for double-circuit brake system.

1 2 3 4

Fig. 5-2 Prefill valve

1 Port O 2 Port T

3 Port A 4 Port P

1 2 3 4 5 6

Fig. 5-3 Prefill valve

1 Low-pressure alarm switch

2 Port A1 3 Port P

4 Port A2 5 Port O

6 Port T


5-4

Brake valve

The hydraulic brake valve is composed of valve

body, oil channels and moveable valve block. Step

the brake pedal, the corresponding oil channels will

open to connect the inlet port and outlet port.

Release the brake pedal, the inlet port and outlet

port will be disconnected and the braking will be

relieved.

Foot brake valve for double-circuit brake system.

1 2 3 4

Fig. 5-4 Foot brake valve

1 Port A1 2 Port A2

3 Port T 4 Port P

1 2 3 4 5 6

Fig. 5-5 Foot brake valve

1 Port T1 2 Port T2

3 Port A1 4 Port A2

5 Port P1 6 Port P2


5-5

Bladder type accumulator

Accumulator is used to store pressure oil for braking.

Its principle is to store the pressure liquid and

capsule with pressure in a sealed housing and it is

used to brake by absorbing and releasing the liquid

due to the changing pressure. When brake pump is

working, it injects the pressure fluid into

accumulator through prefill valve to store energy.

Then, the gas is compressed in the capsule, so that

the pressure of liquid is the same with that of

capsule, to obtain energy reserves. The air in

capsules is nitrogen.

The accumulator can store sufficient pressure oil.

In case of system failure (the prefill valve is not

able to charge), the pressure oil stored in the

accumulator can conduct 6 times braking.

When the pressure of oil in accumulator is lower

than 11.5MPa, low-pressure alarm switch will be

trigged and the alarm indicator on instrument panel

will be on. You should stop the vehicle for

inspection immediately.

1

Fig. 5-6

1 Accumulator

1

Fig. 5-7

1 Lo-pressure alarm switch


5-6

Method to inflate the accumulator

1. Firstly park the machine on flat ground,

continuously operate the service brake and

parking brake several times, and drain the high

pressure oil in accumulators as far as possible.

Then slowly loosen the oil pipe on the bottom

of accumulator and drain the residual pressure

out of the accumulator.

2. Remove the protective cap of inflation valve

from top of the accumulator.

3. Connect the end with pressure gauge of

inflation tool to the inflation valve on top of

accumulator, and the other end should be

connected with nitrogen cylinder.

4. Open the switch of nitrogen cylinder. After the

inflation pressure of inflation tools is stable,

slowly open the switch on the inflation tools,

i.e., open the inflation valve in the accumulator

and fill air into the accumulator.

5. Pressure may be instantly achieved, then switch

off the nitrogen cylinders, and see whether the

pressure value still indicates the specified value

after the gauge of inflation tools come to stable.

If not, then refill it. If the pressure is high, drain

the air through the inflation plug through

inflation tools, and reduce the pressure to the

appropriate value.

6. After air is filled to required pressure, firstly

switch off nitrogen cylinders, and then close the

switch on inflation tools.

7. Remove the air inflation tool.

8. If accumulator leaks (Wipe accumulator head

with oil, and if there is leakage, bubbles will

come out. Hit the inflation valve inside the

Fig. 5-8 Working principle of accumulator


5-7

accumulator with a hammer and a screwdriver.

Pull it down, and then quickly reset it until the

sealing surface can be connected.

9. Install protection cap of accumulator inflation

valve.

Brake assembly

The brake assembly comprises brake and brake

drum.

When the operator steps on the brake pedal, high

pressure oil stored in accumulator (or from the

prefill valve) splits into two parts, flows into the

wheel side brake cylinders respectively. Brake

cylinder pushes the brake shoe to expand outside,

to produce friction resistance between the brake

and brake drum inner wall, so as to realize braking.

The brake mainly consists of brake carrier, brake

cylinder, brake shoe assembly and accessories.

The brake assembly is equipped with brake parts

clearance automatically adjustable cylinder. When

the friction plate is worn off, the clearance between

the friction plate and brake drum can be adjusted

automatically to offset the wear loss.

1 2

Fig. 5-9

1 Brake 2 Brake drum

1 2 3 4

Fig. 5-10 Brake assembly

1 Brake cylinder

2 Brake shoe assembly

3 Brake carrier 4 Return spring


5-8

Deflation of brake system

After overhauling of brake system, there will be air

in the pipeline, which will affect brake

performance. So air bleeding must be done after

the overhaul.

The air bleeding should be performed by two men

cooperatively. Each wheel side brake is designed

with deflating valve (air bleeding valve), do the air

bleeding according to the following instructions:

1. Remove the plastic cap of air bleeding bolt.

2. Connect a hose to the air bleeding bolt, and put

the other end of the hose into a container.

3. Loosen the air bleeding bolt about half a turn,

and tread down the brake pedal. Once there is

oil overflowing, tighten the bolts immediately,

and release the brake pedal.

ATTENTION

The overflowing oil could be transient, so

you need to perform the air bleeding

operation coordinately and cooperatively.

4. The air in other brakes should be drained out

according to related requirements as well.

1

Fig. 5-11

1 Plastic cap

1 2

Fig. 5-12

1 Container 2 Rubber hose


5-9

513 Disassembly and Assembly

Single-Circuit Foot Brake Valve

Disassembly of single-circuit foot brake valve

1. Tread down the brake pedal repeatedly to

unload the brake system.

2. Disconnect the oil pipes from port A, port T

and port T of foot brake valve.

ATTENTION

When dismantling the hydraulic pipes, do

not screw off the nut connecting to the oil

port rashly. Loosen the nut gradually until

the oil spills out so as to prevent the oil

splashing due to incomplete pressure relief.

When dismantling the hydraulic pipeline,

necessary protective measures shall be

taken for each pipeline and oil port to

prevent debris like dust from entering the

brake system.

3. Remove the four straight joints.

4. Remove the three connecting bolts of foot

brake valve and cab.

5. Take the brake valve out of cab.

1 2 3 4

Fig. 5-13

1 Port T 2 Port P

3 Straight joint 4 Port A

1

Fig. 5-14

1 Bolt


5-10

Assembly of single-circuit foot brake valve

1. Fix the foot brake valve on cab with three

bolts.

2. Install the four straight joints to the valve.

58±3Nm

3. Connect the oil pipes to port A, port T and port

T of foot brake valve accordingly.

45±4.5Nm

1

Fig. 5-15

1 Bolt

1 2 3 4

Fig. 5-16

1 Port T 2 Port P

3 Straight joint 4 Port A


5-11

514 Disassembly and Assembly of

Accumulator

Disassembly of accumulator

1. Remove the six connecting bolts of

accumulator periphery board and frame.

2. Tread down the brake pedal repeatedly to

unload the brake system. Remove the oil pipe

from the bottom of accumulator.

ATTENTION

When dismantling the hydraulic pipes, do

not screw off the nut connecting to the oil

port rashly. Loosen the nut gradually until

the oil spills out so as to prevent the oil

splashing due to incomplete pressure relief.

When dismantling the hydraulic pipeline,

necessary protective measures shall be

taken for each pipeline and oil port to

prevent debris like dust from entering the

brake system.

1 2

Fig. 5-17

1 Periphery board 2 Bolt

1 2

Fig. 5-18

1 Accumulator 2 Oil pipe


5-12

3. Loosen the U-shape fixing bolt of accumulator

and take down the bolts, nuts and gaskets, and

then take out the accumulator and remove the

straight joint.

ATTENTION

The accumulator may still contain pressure

even removed from the machine, and that is

so-called preload pressure. You must be

very careful when handling or operating on

the accumulator.

Assembly of accumulator

1. Fix the accumulator on the support with

U-shape bolt, rubber mat, nuts and gaskets.

2. Install the straight joint and connect the oil

pipe.

Pipe joint: 310±31Nm

Oil pipe: 70±7Nm

1 2 3

Fig. 5-19

1 U-shape bolt 2 Rubber mat

3 Accumulator

1 2 3

Fig. 5-20

1 U-shape bolt 2 Rubber mat

3 Accumulator

1 2

Fig. 5-21

1 Accumulator 2 Oil pipe


5-13

3. Install the accumulator periphery board to rear

frame with bolts.


Prefill Valve

Disassembly of prefill valve

1. Remove the six connecting bolts of

accumulator periphery board and frame.

2. Disconnect the oil pipe (to oil tank) from port

O of prefill valve.

3. Disconnect the oil pipe (to high-pressure filter

oil outlet) from port P of prefill valve.

4. Remove the T-junction from port A of prefill

valve.

5. Remove the T-junction from port T of prefill

valve.

1 2

Fig. 5-22


1 2

Fig. 5-23


1 4 2 3

Fig. 5-24

1 Oil pipe (Port O) 2 Port P

3 T-junction (Port T)

4 T-junction (Port A)


5-14

6. Remove the fixing bolts of prefill valve

periphery. Take down the valve.

Assembly of prefill valve

1. Install the fixing bolts of prefill valve

periphery.

2. Install the T-junction to port A of prefill valve.

Install the T-junction to port T of prefill valve.

70±7Nm

3. Connect the oil pipe (to high-pressure filter oil

outlet) to port P of prefill valve.

70±7Nm

4. Connect the oil pipe (to oil tank) to port O of

prefill valve.

110±10Nm

1

Fig. 5-25

1 Bolt

1

Fig. 5-26

1 Bolt

1 4 2 3

Fig. 5-27

1 Oil pipe (Port O) 2 Port P

3 T-junction (Port T)

4 T-junction (Port A)


5-15

5. Install the six connecting bolts of accumulator

periphery board and frame.

516 Replacement of Brake Shoe

1. Remove the rear wheels. Refer to 7 Frame,

Wheels & Working Device for details.

2. Remove the brake drum.

1 2

Fig. 5-28


1

Fig. 5-29

1 Tire

1

Fig. 5-30

1 Brake drum


5-16

3. Remove the end cover.

4. Remove the splined hub.

5. Remove the return spring.

ATTENTION

Be careful when disassembling the spring,

and protective measures shall be taken.

1

Fig. 5-31

1 End cover

1

Fig. 5-32

1 Splined hub

1

Fig. 5-33

1 Return spring


5-17

6. Replace the brake shoes.

7. Install the return spring.

ATTENTION

The new brake shoe must be grinded and

repaired to ensure necessary contact area

between the brake shoe and brake drum.

Besides, to avoid unbalanced braking force,

the two brake shoes should be replaced

together.

8. Install the splined hub.

1

Fig. 5-34

1 Brake shoe

1

Fig. 5-36

1 Splined hub

1

Fig. 5-35

1 Return spring


5-18

9. Install the end cover.

10. Install the brake drum.

11. Install the rear wheels.

700~800Nm

12. Recover the machine.

1

Fig. 5-39

1 Tire

1

Fig. 5-38

1 Brake drum

1

Fig. 5-37

1 End cover


5-19

52 Parking Brake System

521 Working Principle of Parking

Brake

The parking brake system is used to keep loader

stay at original position after stop, to avoid

unexpected movement due to inclined road or

external forces. The system consists of brake

handle, parking brake and fixed plate.

Hand brake operating mechanism comprises hand

brake, control handle, and control wire (flexible

shaft). When pulling up the brake control handle,

the pull rod will swing and the cylindrical can at

the end of the pull rod will rotate to expand the two

brake shoes (friction plates), the brake shoes will

press against the inner wall of rotating brake drum

to realize braking, and the hand brake indicator

light will be on.

Generally, the failure rate of parking (hand) brake

system is very small. But if basic maintenance

tasks are not being carefully addressed, phenomena

like brake slide, wear of friction plates, crack of

brake drum and brake dray (the grader is not able

to move after reliving the brake) may occur. The

brake slide is caused by severe worn friction plates.

The main causes of premature wear of friction

plate are: there is oil on friction plate, or swell of

friction plates (exposed to moisture). The brake

drag is mainly caused by swell of friction plate.

Thereby, you should clean the friction plates

periodically to keep them clean and dry.

1 2 3

Fig. 5-40 Schematic diagram of parking

brake system

1 Parking brake is relieved

2 Parking brake is engaged

3 Parking brake assembly

1

Fig. 5-41

1 Hand brake indicator light


5-20


Parking Brake Control

Mechanism

Disassembly of parking brake control

mechanism

1. Remove the fixing screws of parking brake

control handle shield.

2. Screw off the adjusting nut of flexible control

shaft.

3. Use a plier to remove the cotter pin and

connecting pin.

4. Take down parking brake assembly.

1 2

Fig. 5-42

1 Screw

2 Parking brake control handle

1 2

Fig. 5-43

1 Adjusting nut

2 Connecting pin, cotter pin


5-21

Assembly of parking brake control mechanism

1. Fix the parking brake control handle shield on

cab floor with screws. Then set the brake

handle in the lowest position (non-braking

state). Connect the flexible control shaft and

the hand brake.

2. Connecting the parking brake control shaft to

the parking brake with pin and cotter pin, and

fix the shaft on the support.

1 2

Fig. 5-44

1 Screw

2 Parking brake control handle

1 2

Fig. 5-45

1 Adjusting nut

2 Connecting pin, cotter pin


5-22

53 Diagnosis and Solutions for Common Faults of Brake System

Common faults of full hydraulic brake system are: Insufficient foot brake force, parking brake can’t

be released normally, insufficient parking brake force, accumulator charging failure or too long

charging time, no inching braking, low service brake pressure alarm indicator light is on, and the

brake lamp doesn’t work.

523 Common Fault of Service Brake System

Table 5-1

S/N Problems Diagnosis Solutions

1

Insufficient

foot brake

force

1. There is air in brake line.

2. Brake valve is faulty.

3. There is leakage in the

brake line.

4. Prefill valve does not work.

5. Accumulator is damaged.

6. Friction plate of wheel side

brake is worn to the limit.

7. The pilot pump is too old to

work.

8. There is oil (dirt) on brake

shoe

1. Drain the air. There are deflating

valves on left and right wheel side

brakes.

2. Check brake valve, detect whether

the maximum braking pressure of

brake valve outlet is equal to the

brake pressure required by the

system. If the pressure is not

normal, adjust the brake pressure or

replace the brake valve.

3. Check whether the brake pipelines

and connectors leak. If the

connector is loose, retighten it; if

the seal is damaged, replace it.

4. Replace prefill valve.

5. Check the accumulator

6. Replace friction plate.

7. Check the pressure or flow of

pump.

8. Clean the brake shoe.

2

Charging

frequency of

prefill valve

is too fast

1. Pressure of accumulator

capsules is too low.


1. Check the air pressure in the

accumulator capsules.

2. Replace prefill valve.

3

Accumulator

charging

failure

1. There is no oil or oil level

is too low in hydraulic

tank.

2. Pump is too old to work

3. There is air in accumulator.

4. Prefill valve does not work

1. Check the oil level in the tank.

2. Check the pump pressure or flow.

3. Drain the air.

4. Replace the prefill valve.


5-23

4

Accumulator

charging

time is too

long

1. Pump is too old to work

and cannot deliver all flow

or pressure.


3. Accumulator capsule is

damaged and nitrogen is

leaked.

1. Check the pressure or flow of

pump.

2. Replace the prefill valve.

3. Remove, check or replace

capsules.

5

The brake

lamp doesn’t

work

1. The brake lamp is

damaged.

2. There are system faults in

the working process of

grader and oil pressure is

decreasing.

1. Check the brake lamp.

2. Stop the machine to check it.

6

Low service

brake

pressure

alarm

indicator

light is on

1. System pressure is

inadequate, in the short

time of starting grader.

2. System failure, the oil

pressure is decreased.

1. Please wait that the alarm will stop

automatically if system oil

pressure is sufficient.

2. Stop the machine for inspection

7

Low service

brake

pressure

alarm

indicator

light is on

when service

brake is

engaged

1. There is leakage in brake

line.

2. Pressure of nitrogen in the

accumulator capsule is

abnormal (caused by

sealing failure).

1. Check whether the brake pipes and

pipe joints have leakage problem.

If the pipe joint is loose, retighten

it; if the seal is damaged, replace

the seal.

2. Unload the brake system

thoroughly before measuring the

nitrogen pressure. Methods: Shut

down the engine and tread down

the brake pedal repeatedly to

unload the brake system, and use

pressure gauge to measure the

nitrogen pressure.

8 No inching

braking Brake valve failure.

Detect whether the maximum pressure

of brake valve outlet is normal. If the

maximum pressure of export is much

greater than required system pressure,

replace the brake valve.

9

Off tracking

when

braking

Inflation pressure of the tires

are not uniform.

Try to keep the tire pressure uniform as

far as possible.


5-24

524 Common Fault of Parking Brake System

Table 5-2

S/N Problems Diagnosis Solutions

1 Parking

brake failure

1. The clearance between

brake drum and brake shoe

is too large, the contact

area is small.

2. There is oil on the brake

shoe.

3. The expansion force of the

brake shoe is not enough.

1. Readjust it as required.

2. Clean brake shoe.

3. Adjust the stroke of parking brake

control mechanism.

2

Parking

brake

control

handle

cannot be

fixed

The parking brake control

handle is faulty.

Check whether the parking brake

control handle deformed or jammed,

whether the spring is broken. If not,

check whether it is caused by screw

loose.

5brake system englisg-g9165

Documents

brake circuit

hydraulic brake system

brake pedal

brake cylinders

common faults of brake

brake lamp switch

drumtype brake

replacement of brake