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Training Material of Loader Brake System

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Title: Training Material of Loader Brake System


1
Training Material of Loader Brake System
  • Shandong Lingong
  • Import and Export Corp. Training Room
  • 2011

2
Contents
  • Section I Overview
  • Section II Working Principles of Brake System
  • Section III Main Components of Service Brake
    system
  • Section IV Main Components of Emergency and
    Parking Brake System
  • Section V Use, Replacement and Notes of Brake
    Fluid
  • Section VI Trouble Shooting of Brake System

3
Section I Overview
  • I. Concept of Pneumatic Transmission
  • Pneumatic Transmission refers to the process of
    taking the compressed air as power source and an
    actuating medium to achieve energy transmission,
    signal transmission and process control.
  • 1.Advantages Simple structure, low cost, easy to
    achieve stepless speed regulating
  • 2.DisadvantagesThe working pressure is low, so
    it only adapts to low-power transmission. Since
    the air is compressible, the stability of the
    pneumatic device is poor and the working speed
    often changes with the external load.

4
  • II. Requirements of Pneumatic Transmission on
    Actuating Medium
  • 1.The compressed air is required to have enough
    pressure and flow
  • 1)Without enough pressure, neither the executive
    mechanism can generate sufficient thrust, nor can
    the control mechanism act correctly
  • 2)The action speed and procedural requirements of
    the executive mechanism cannot be guaranteed
    without enough flow.

5
  • 2.The compressed air is required to have a
    certain degree of cleanliness and dryness
  • 1)Cleanliness is the degree on the content of
    oil, dust and impurity in the air
  • 2)Dryness is the amount of moisture in the
    compressed air (the water content in the air of
    the pneumatic device is required to as little as
    possible)

6
  • III. Concept of Brake
  • Brake means a sufficient large brake torque is
    produced through the brake system to consume the
    saved kinetic energy generated during the moving
    of the machine in brake to force it to slow down
    and even stop within a certain distance. The more
    frequently used method in the brake system is to
    consume the kinetic energy of the moving vehicles
    to produce the brake force by using mechanical
    friction.
  • IV. Classification of Brake System
  • It can be divided into service brake and parking
    brake according to the role or function of the
    brake.

7
  • V. Composition of Brake System
  • An energy supplying device, a control device, a
    transmission device, an actuating device and
    auxiliaries
  • 1. Energy supplying device Compressor
  • 2. Control device Oil-water separator, air brake
    valve, brake solenoid valve, hand brake valve,
    etc.
  • 3. Transmission device Booster pump, parking
    brake chamber, etc.
  • 4. Actuating device Brake caliper, parking
    brake, etc.
  • 5. Auxiliaries Gas tank, pipeline, etc.

8
Section II. Working Principles of Brake System
  • I. Service Brake System
  • It is used to lower the speed and park during the
    moving of the vehicles, which is controlled by a
    driver through a brake pedal.
  • 1.According to the brake circuit It can be
    divided into single-circuit system and
    Dual-circuit system
  • 2. According to the different mediums of the
    brake shoes It can be divided into dry brake and
    wet brake
  • The caliper disc brake is dry brake, and the ZF
    drive axle brake is wet brake.

9
  • (1)Single Circuit Brake System
  • 1)Composition An air compressor, a oil-water
    separator, a booster pump (front and rear), a
    pneumatic brake valve, a brake caliper, an air
    storage tank, pipelines, etc.
  • 2)Type Gas cap oil four-wheel forceps disc brake

10
Bake pedal
Bake
Disc brakes (fixed with axle pipe
Brake valve
To off valve
Afterburner cans
Bake master pump
Rear
Leather cup
Oil-water separator
Adjusting valve
Leather collar
Air
Air compressor
Tire charging
Air tank
1type seal ring
Filled oil Pressure air Charging air
Air
Front
Rear axle
Brake
Brake
Front axle
Air bleeding
Tire charging
Structure Chart of Single-circuit Service Brake
11
Bake
Afterburner pump
Oil-water separator
Air brake valve
Brake caliper
Air tank
Layout Diagram of Single-circuit Service Brake
12
Afterburner pump of front drive
Afterburner pump of rear drive
Schematic Diagram of Single-circuit Service Brake
1. Air Booster Pump 2. Foot Brake Valve 3. Gas
Tank 4. Oil-water Separator Combination Valve 5.
Air Compressor
13
  • (2)Dual-circuit Service Brake System
  • 1)Composition Air compressor, oil-water
    separator, booster pump (front and rear),
    pneumatic brake valve (left and right), brake
    caliper (or wet brake), air storage tank,
    pipeline, etc.
  • 2)Type Gas cap oil four-wheel forceps disc (or
    wet) brake

14
Brake caliper
Bake
Oil-water separator
Air brake valve
Front afterburner pump
Rear afterburner pump
Air tank
Layout Diagram of Dual-circuit Service Brake
15
Schematic Diagram of Dual-circuit Brake System
1.Air Booster Pump2.Shuttle Valve3.Pneumatic
Brake Valve4.Gas Tank 5.Oil-water Separator
Combination Valve 6.Brake Solenoid Valve7.Parking
Brake Chamber
Brake pump of front drive
Brake pump of rear drive
16
  • (3)Wet Brake
  • ?The ZF drive axle uses a wet brake, whose
    structure is similar to that of the gear clutch
    of the gearbox. The high-pressure brake fluid
    runs into the piston chamber during a brake,
    presses the friction plate tight by pushing the
    piston to move in order to achieve brake. Run a
    return spring to release the brake.
  • ?The structure and working principles of the
    brake are completely different from those of the
    dry brake. The requirements of brake fluid and
    brake fluid displacement in respect of the
    sealing elements of the both are also different.
  • ?Now, the ZF drive axle uses single
    (Dual)-circuit gas cap oil brake system. The
    difference lies in that the booster pump used is
    a special booster pump with low-voltage large
    displacement. The storage cup of the booster pump
    is changed into a storage drum, which is
    arranged separately on the back outside the
    driving cab and connected with a inlet of a brake
    master cylinder through an oil pipe. The brake
    fluid is SAE10 universal oil, Mobil Delvac 1310
    is recommended. (Main configuration 959?969)

17
  • II. Parking Brake System
  • It is used to brake in case of an emergency
    during the operation of the loader, and keep the
    loader at the original location after parking in
    order not to move due to the road slope or other
    external forces.
  • Brake position The brakes of the parking brake
    system are always installed on the front output
    shaft of the gearbox on the loader. Through
    manual control or chamber control, the brake
    shoes expand or clap (clap-type) the brake disc
    to achieve parking brake.

18
  • 1. Classification According to Brake Form
  • Manual parking brake, electric air-controlled
    parking brake, manual air-controlled parking
    brake.
  • 2. Divide according to the brake type
  • Caliper disc type and internal expanding shoe type

19
(1)Manual Caliper Disc Type Parking Brake
Mainly composed of ?Control Lever ?Control
Flexible Shaft ?Caliper Disc Parking Brake,
etc. 933?953?952, etc.
20
  • (2)Electric Air-controlled Parking Brake
  • 1)Composition A caliper disc type (or drum type)
    brake, a parking brake chamber, a brake solenoid
    valve, a pressure switch, a brake knob, an air
    storage tank, pipeline, etc. (936?958?959, etc.)
  • ?Brake off rotate the operation button
  • ?Emergency or parking brake press the operation
    button
  • ?Automatic protection control the pressure
    switch automatically switch off the power supply
    to the brake valve when the air pressure is lower
    than 0.4Mpa

21
1. Air Pressure Signal Lamp Switch 5. Brake
Solenoid Valve 8. Parking Brake Chamber 14.
Hand Brake 17. Pressure Switch 19. Pressure
Sensor
Structure Chart of Electric Air-controlled
Caliper Disc Type Brake System
22
Schematic Circuit Diagram of Electric
Air-controlled Brake System
Pressure switch
Brake knob
Brake magnetic valve
23
  • (3)Manual Air-controlled Caliper Disc Type Brake
  • 1)Composition A caliper disc brake, a parking
    brake chamber, a hand brake valve, an air storage
    tank, pipelines, etc. (mainly used in 956?956L)
  • 2)Working principles The brake principles of the
    manual air control and electric air control are
    basically the same, and the difference lies in
    that the hand brake valve is used instead of the
    3/2 way solenoid valves. As for the operation of
    the hand brake valve, press the button down to
    brake off and lift up the button to connect.
  • 3)Automatic protection When the brake pressure
    is lower than 0.28Mpa,the manual button will
    pop-up automatically and cut off the air supply.

24
Parking brake indicator switch connector
Schematic Diagram of Manual Air-controlled Brake
System 1. Parking Brake Chamber 2. Hand Brake
Valve 3. Oil-water Separator Combination Valve
4. Air Compressor 5. Air Storage Tank 6. Foot
Brake Valve 7.Air Booster Pump
25
Friendly Reminder
  • Since there is no rigid connection between the
    loader engine and the output shaft of the torque
    converter, its suggested that the driver should
    not only use the parking brake, but also put
    blocks under the wheels or compact the ground
    with a bucket to prevent the vehicle from sliding
    when the vehicle is stopped at the slope (uphill
    or downhill) and the driver intends to leave.

26
Section III Main Components of brake System
  • I. Air Compressor
  • The air compressor is installed in the front of
    the injection pump shaft coupling in the same
    axis with the injection pump camshaft and driven
    by the drive gear of the injection pump inside
    the gear room.
  • Lubrication the press oil is led in by the
    engine oil passage through the oil pipe fixed on
    the cylinder into the air compressor to lubricate
    bearings and then cylinder sleeves by splashing
    before returning to the oil pan via the timing
    gear chamber.

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  • Air source the air intake must pass through an
    air filter before entering the air pipe in front
    of the turbocharger connected to the air inlet of
    the air compressor.
  • Cooling use the same water circulating cooling
    system with the engine.
  • 1.Function to provide compressed air to the
    brake system.

28
Structure of Air Compressor
1 Inlet Pipe 2 Exhaust Pipe 3 Piston Pin 4
Cylinder 5 Crankcase 6 Crankshaft 7 Crankshaft
Oil Seal 8 Oil Pan 9 Return Pipe Joint 10 Drive
Joint 11 Piston Ring Set 12 Cylinder Head 13
Intake Valve 14 Exhaust Valve 15 Piston 16
Connecting Rod
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  • 2. Working Process
  • (1) Air intake
  • (2)Air compressing
  • Potential causes of faults excessive abrasion of
    cylinder, piston and piston ring, incomplete
    closure of intake and exhaust valves, etc.

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  • II. Oil-water Separator Combination Valve
  • The oil-water separator combination valve is a
    valve composed of an oil-water separator and an
    air pressure regulator.
  • 1. Functions
  • (1)Separte oil, water and other foreign matters
    in the compressed air
  • (2)Automatically regulate the working pressure of
    the brake systems air source (exhaust at
    0.784Mpa supply air at 0.686Mpa)
  • (3)Ensure the safety of the brake system
    (protection at 0.882Mpa)
  • (4)Inflate tyres.

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2. Structure Composition It mainly consists of
mid-body, upper cover, lower shell, internally
separated oil-water separation chamber, filter
element, check valve and safety valve assembly,
air pressure regulating components and air liquid
release valve, etc.
Structure Chart of Oil-water Separator
Combination Valve
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1.Upper Cover 2.Mid-body 3.Lower Shell 4.Pressure
Regulating Spring 5.Control Piston
Assembly 6.Return Spring Of Check
Valve 7.Regulating Stem 8.Regulating Valve 9.Air
Release Piston Assembly 10.Air Release
Valve 11.Air Release Piston 12.Return
Spring 13.Air Filter
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Notes for Oil-water Separator Combination Valve
  • The air pressure control screws, safety valve
    assembly and other key parts have been adjusted
    by the manufacturer before leaving the factory
    and shall not be adjusted arbitrarily in general
    conditions so as to avoid potential damages on
    the brake system for safety concerns. If the
    adjustment is necessary, then adjust the Safety
    Valve Assembly 9 first and then the Pressure
    Regulating Valve 7 to avoid an excessive increase
    of the pressure in the system.

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Common Faults of Oil-water Separator
  • 1. When the seal ring of the air release valve in
    the lower part of the exhaust piston is damaged
    or stuck with foreign matters, air leakage will
    occur for incomplete closure of the valve.
  • 2. When the return spring of the air release
    piston fails or the piston is stuck, air leakage
    will occur for incomplete closure of the valve.
  • 3. When the air hole to the atmosphere of the
    upper shell is blocked, the air release piston
    can not return effectively and air leakage will
    occur for incomplete closure of the vale.

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Common Faults of Oil-water Separator
  • 4.When the tympanic membrane ruptures, the
    pressure will become lower and the compressed air
    will leak from the air hole in the upper cover.
  • 5.When the elasticity of the regulating spring
    decrease for the long-time working, the system
    pressure will become lower.
  • 6.When the throttle orifice from chamber C to
    chamber D is blocked, the pressure regulating
    spring and the piston assembly are stuck, parts
    of the air pressure regulating functions fail
    and the air pressure exceed 0.882Mpa,the
    compressed air acts on the safety valve, breaks
    through the valve and enters into the atmosphere.

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  • III. Air Storage Tank
  • 1. Functions
  • (1)It stores the compressed air for the brake
    system. When the air compressor is not working,
    the air needed for certain number of brakes is
    ensured.
  • (2) It is equipped with a safety valve, a
    pressure sensor, an inflation valve, a drain
    valve and a pressure switch.

Structure Chart of Air Tank
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Foreign matters like water and rust may enter the
booster pump via the pipelines if the air storage
tank hasn't discharged water for a long time.
Pollution too dirty
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  • IV. Air Brake Valve
  • The brake valve is a control device controlled by
    the brake pedal for wheel brake or brake release.
  • 1. Functions
  • In the brake state, it controls the amount of
    the compressed air into the air chamber of the
    booster pump, i.e., control the air pressure of
    the booster pump for different brake effects. It
    makes the driver able to feel the brake degree
    from the pedal stroke and the size of operating
    force.

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2. Structure Composition It consists of a pedal,
a upper cover, a lower valve body and a carrier
rod, an assembly consisting of a piston, a
balance spring, an air intake valve inside the
vale body and a return valve, etc.
Structure Chart of Air Brake Valve
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  • 3. Working Process
  • (1)Brake
  • (2)Release of brake
  • (3)Funcions of balance spring

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1.Upper Cover 2.Valve Body 3.Carrier
Rod 4.Balance Spring Assembly 5.Piston 6.Return
Spring 7.Retainer Ring 8.Valve Core
Assembly 9.Return Spring 10.Air Intake
Valve 11.Valve Assembly (Spring Seat)
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Notes for Brake of Loader Driving on Ramp
  • According to the working principle of the brake
    valve, in the brake state, the brake pedal
    applies some pressure on the balance spring which
    exerts force on the piston to push the air intake
    valve core open and close the passage for the
    compressed air in the brake valve entering into
    the atmosphere. For example, by frequent
    triggering of the brake, the passage to the
    atmosphere between the piston and the top of the
    air intake valve keeps opening and closing,
    causing the constant exhaust of the compressed
    air via the duct in the middle of the air intake
    valve if the air exhausted exceeds the supply of
    the air compressor, the air in the air tank will
    decrease rapidly, and when the air pressure is
    lower than 0.4Mpa, the brake effects decrease.

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  • Current operation when driving downwards, keep
    the foot on the pedal and press properly
    according to the road conditions for different
    brake effects and pay attention to the change in
    brake pressure and do not frequently trigger the
    brake.
  • During the the brake test on 953,the consecutive
    trigger of brake for about 10 times will decrease
    the air pressure from 0.7Mpa to below 0.4Mpa.

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Common Faults of Air Brake Valve
1.Limit screw it is used to adjust the free
stroke of foot brake valve by turning clockwise
to increase the free stroke and turning
anti-clockwise to decrease when it is turned
anti-clockwise to a certain degree, the exhaust
port will close and open the air intake valve
core. 2.Air intake valve core if it is stuck in
the air intake state, when the foot brake pedal
returns, the air in the air storage tank will
enter the atmosphere via the inner hole of the
air intake valve.
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Common Faults of Air Brake Valve
  • 3.When the seal ring on top of the air intake
    valve or there are foreign matters, in the brake
    state, some air in the air storage tank leaks at
    the damaged position, thus decreasing the brake
  • 4.If the brake piston is stuck in the brake
    state, when the foot brake pedal is released, the
    lower part of the brake piston contacts the
    exhaust port and the air returning from the
    booster pump can not be exhausted or exhausted
    rapidly form the exhaust port, causing brake
    dragging and unclear classification of the faults.

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  • V. Power Cut Switch (fit for 956L only)
  • 1.Function
  • Connect or disconnect the passage for the
    compressed air to the air cut valve of the speed
    change valve for the cut-off or normal passing of
    the power oil.
  • 2. Advantage
  • The use of the power cut-off makes the loaders
    transmission system terminate the power
    transmission in the brake state, decreases the
    fault rate of the transmission system, increases
    the safety effects of the brake and makes it
    possible to apply all the power on the working
    devices when the loader shovels.

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  • 3.Disadvantages
  • In some working conditions, such as ramp
    construction, the switch shall be turned to the
    cut-off position to avoid the sliding of the
    loader for gravity at the moment of reintegration
    of the gear clutch when restarting after
    releasing the brake.

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  • VI. Air Booster Pump
  • 1.Function
  • Use the compressed air from the air brake valve
    to pressurize the brake fluid in the brake master
    pump to promote the working of the brake caliper
    piston.
  • 2. Working Process
  • 1) Brake state
  • 2)State of releasing brake

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3.Main Structure It mainly consists of a booster
cylinder, a brake pump, a air chamber piston, a
oil pressure piston, a push rod, a push rod seat,
a end cover, a return spring, a oil storage cup,
seals, etc.
Structure Chart of Air Booster Pump
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1.Brake Pump 2.Booster Cylinder 3.Repirator 4.End
Cover (Booster Pump Body) 5.Air Chamber
Piston 6.Oil Pressure Piston 7.Push Rod 8.Return
Spring 7.Push Rod Seat Assembly 8.Oil Intake
Valve 9.Central Seal Ring 10.Master Pump
Cup 11.Booster Cylinder Apron
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Common Faults of Air Booster Pump
  • 1.When the apron of the air chamber piston is
    damaged, the compressed air enters the
    low-pressure chamber from the high-pressure
    chamber and is exhausted from the breathing hole,
    and the brake force decreases.
  • 2?When the guiding seal ring of the push rod is
    damaged, the oil in the oil storage cup leaks
    from the damaged position and the brake liquid
    leaks from the breathing hole of the booster
    chamber or the joint between the cylinder and the
    end cover.
  • 3?When the piston cup of the brake pump is
    damaged, when boosting, the high-pressure brake
    liquid returns to the oil storage cup from the
    damaged cup, resulting in upward leakage of the
    brake liquid and brake weakness.
  • 4?When the seal ring at the compensation hole
    between the push rod seat and the brake pump
    piston are damaged, the upward leakage of the
    brake liquid and brake weakness also occur.

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Common Faults of Air Booster Pump
  • 5.When the seal ring at the joint of the brake
    master pump and the end cover is damaged, the
    leakage of the brake liquid will occur.
  • 6.When the seal ring in the joint of the oil
    storage cup and the end cover is damaged, the
    leakage of the brake liquid will occur.
  • 7.When the respirator in the booster is blocked,
    the brake force will become inadequate or the air
    chamber piston can not return in time, resulting
    in delay of brake release.
  • 8.When the return spring in the air chamber
    breaks, the brake force will become inadequate or
    drag.

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Leakage inside Brake Master Pump
Brake fluid ejective
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Rupture of Booster Pump Spring
55
  • VII. Caliper Disc Brake
  • 1.Function
  • The pressurized brake liquid acts on the brake
    caliper piston to facilitate the brake friction
    slice to clamp the rotating brake disk to brake.

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2.Main Structure It mainly consists of a
caliper, a brake piston, a friction slice and
rectangular seal rings.
Structure chart of Caliper-type Brake
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1.Inner caliper 2.Outer caliper 3.Seal
ring 4.Piston 5.Rectangualr seal ring 6.Dust cover
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Functions of Rectangular Seal Ring 1.Seal of the
brake liquid inside the brake caliper 2.Automatic
return of the brake caliper piston 3.Automatic
adjustment of brake clearance after the wear of
the brake pad
(a) (b) Working Conditions of
Rectangular Seal Ring 1 Rectangular Seal Ring 2
Brake Caliper 3 Piston
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  • 3. Working Process
  • (1)While braking
  • (2)After brake releasing
  • (3)Automatic compensation of the friction slice
    clearance

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?Abnormal wear of the brake disc and brake
pad ?After identification, the material quality
and hardness of the brake disc and the brake pad
are within the scope of the requirements, and the
wear is caused by sands and stones spraying on
the space between the brake pad and brake disc.
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Common Faults of Brake Caliper
  • 1.When the seal ring between the outer caliper
    and inner caliper is damaged, the leakage of the
    brake liquid will occur.
  • 2.The rusting of the brake caliper piston will
    cause malfunction of the piston.
  • 3.The air in the brake pipeline will cause
    inadequate brake force or delay of brake release.
  • 4.When the rectangular seal ring is damaged, the
    leakage of the brake liquid, inadequate brake
    force and incomplete piston return will occur.

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Section IV Main Components of Emergency and
Parking Brake Systems
  • I. Air inlet of the hand brake valve is connected
    with the air storage tank, and air outlet
    connected with the parking brake air chamber and
    exhaust port directly to the atmosphere.
  • 1.Air Pressure Protection
  • Automatic protection at pressure below 0.28Mpa.
  • 2.Working Process

Air inlet
Air outlet
Exhaust port
Figure 3.5-11 Emergency and Parking Brake
Systems 1 Control Button 2 Carrier Rod 3 Seal
Ring 4 Spring 5 Valve Body 6 Valve Assembly 7
Seal Ring 8 Bottom Cover
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1.Brake Button 2.Air Inlet 3.Air Outlet 4.Exhaust
Port
P. Connected with the air tank A. Connected with
the brake air chamber T. Connected with the
atmosphere
Picture of Hand Brake Valve
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  • II .Brake Solenoid Valve
  • Brake solenoid valve has the similar operation
    principle as the hand control valve, but the
    valve is controlled by electrical signal instead
    of hand.
  • 1. After pulling out of the control knob, connect
    the power of the solenoid valve, the solenoid
    valve core pull in and open the air passage to
    the parking brake air chamber, the air pressure
    overcomes the elastic force of spring in air
    chamber, then the parking brake is released.
  • 2. When the control knob is pushed or brake air
    pressure is below 0.4 MPa, the brake solenoid
    valve is power off, the valve core cuts off the
    air passage to the brake air chamber and open the
    passage of the brake air chamber to the
    atmosphere, thus connecting the brake.

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Common Failures 1. Line failure 2. Solenoid
valve coil failure 3. poor seal of Reversing
valve
P. Connected with air storage tank A. Connected
with brake air chamber T. Connected with the
atmosphere
Picture of Brake Solenoid Valve
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  • III .Parking Brake Air Chamber
  • 1. Function when the air pressure overcomes the
    elastic force of the spring in air chamber,
    parking brake is released when the source is cut
    off or the brake pressure is less than the
    specified value, the spring of the air chamber
    returns thus connecting the brake.

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2. Main Structure
Mainly consist of an end cover, a push rod, a
outer cylinder, pistons, springs, seals, etc.
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1. Cylinder Body 2. End Cover 3. Piston 4. Air
Chamber Apron 5. Push Rod 6. Return Spring
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  • 3. Cautions
  • If the compressive elasticity of brake spring in
    the parking brake air chamber is too great, the
    dismantling shall not made. In case of a failure,
    please replace an assembly to prevent safety
    accident.
  • For the machine equipped with the parking brake
    air chamber, if it needs to be moved by a trailer
    due to a breakdown or other reasons, the air
    chamber push rod and handle of the brake shall
    be loosened before pulling so as to avoid the
    damage of the machine.

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  • IV Hand Brake
  • 1.FunctionIn the brake state, the handle is
    lifted and the friction slices (caliper disc) act
    on the brake disc and brakes the loader in the
    state of brake released, the handle is loosened
    and the friction slices on the both sides
    automatically expand under the effect of the
    spring force, and then the brake is released.

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2. Main Structure Mainly consist of a handle, a
spring, friction slices, adjuster bolts, holders
and so on.
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Section V Use, Replacement and Cautions for Brake
Fluid
  • I .Categories of Brake Fluid
  • Three major types alcohol-based, mineral oil and
    synthetic. Among them, alcohol-based and mineral
    oil brake fluid are not commonly used, and the
    synthetic brake fluid is mostly used now.
  • 1. Synthetic Brake Fluid
  • The kind of brake fluid is made based on the
    synthetic fluid with the various additives.

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  • 2. Labeling
  • Taking HZY3 as an example, where H, Z and Y
    respectively represents the first letter of
    synthetic, brake and fluid in Chinese, the number
    3 is a mark for distinguishing each standards
    of this series without any specific meaning.
  • Our service brake system uses HZY3(DOT3)
    synthetic brake fluid. (wet brake usually uses
    Mobil Delvac 1310)

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  • II Use of Brake Fluid
  • 1.Brake fluids of different brands shall not be
    mixed so as to avoid the layering which may
    result in the brake failure
  • 2.Container of the brake fluid shall be dedicated
    so as to avoid the mixing of other oils which may
    result in reacting and the brake failure.
  • 3.The container of the brake fluid shall be clean
    and tightly covered so as to prevent the entrance
    of mechanical admixture and moisture. During the
    use, dust and foreign materials found on the
    surface of the brake fluid shall be cleared and a
    mixing is prohibited use a clean special tool to
    fill the brake fluid.

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  • III .Replacement of Brake Fluid
  • 1. When the brake fluid is mixed with mineral
    oils, such as gasoline, diesel and so on
  • 2. When the vehicle is under normal driving but
    the brake keeps an anomalistic changing
  • 3. When the brake fluid in the system becomes
    less for some reasons or the vehicle with a
    liquid level alarm gives an alarm
  • 4. When checking the brake fluid and finding the
    color of oil turns to turbid or contains
    impurities and sediments.

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  • IV .Cautions for Replacement of Brake Fluid
  • 1.Use the brake fluid specified by the Company
  • 2.When replacing the brake fluid, clean the
    raffinate in the brake system and examine new
    brake fluid
  • 3.When replacing the brake fluid, reduce the time
    for the brake contacting with the air so as to
    prevent the brake fluid absorbing moisture, thus
    lowering the performance of the brake fluid
  • 4.Before replacing the brake fluid, it could be
    better if the brake system is washed with alcohol.

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  • V .Exhaust of Brake System
  • Air entering into the brake pipeline will affect
    the brake,and the brake failure will occur if the
    case is serious. So after the replacement of the
    parts, clean the system and replace the brake
    fluid, the system shall exhaust and the steps to
    exhaust are as followed
  • 1. Fill the oil storage cup of the booster pump
    with the brake fluid
  • 2. Loosen the screw at the relief port of the
    booster pump until a stream of the fluid flows
    out, and then tighten the bleed screw

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  • 3. Start the engine, and after the air pressure
    rises to the specified value(0.68MPa), step on
    the brake valve pedal for several times to make
    the brake pipeline and brake caliper filled with
    the brake fluid in the state that the brake
    pedal is stepped down, loosen the bleed screw of
    the brake caliper to discharge the air, and
    tighten the bleed screw quickly, repeat the steps
    above until no bubble appears in the brake
    caliper and a stream of the brake fluid flows
    out, and then stop discharging the air and
    tighten the bleed screw.

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  • 4.During the process of discharging, continuously
    supply the oil cup of the brake with the brake
    fluid in order to prevent the entering of the
    air.
  • 5. After completing the air discharge, fill the
    oil storage cup with the brake fluid until the
    liquid level of the brake fluid is above
    two-thirds and then tighten the cap of the oil
    cup.

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Section VI Typical Failure Removal for Brake
System
  • Case 1
  • Failures
  • The reason why there is a brake drag in the
    loader?
  • Definition of brake drag when brake is released,
    the brake caliper has separating problems so that
    the part of brake moment is still transmitted by
    the brake caliper under the state of non-brake
    state.
  • Thread of Judgment
  • ?Air enters into the brake system
  • ?Examine whether the front and rear axle are
    jammed
  • ?Failure in brake caliper
  • ?Failure in brake valve
  • ?Failure in booster pump.

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  • Case 2
  • Failures
  • The reason why the booster pump leaks the brake
    fluid?
  • Thread of Judgment
  • ? First, observe where the brake leaks and
    distinguish whether it is internal leakage or
    external leakage
  • ? Leak from the breather of the booster cylinder
    or the joint, the guiding seal ring of the push
    rod is damaged and an internal leakage occurs
  • ? At the joint of the pump body and end cover,
    the seal ring is damaged and an external leakage
    occurs
  • ? At the joint of the oil storage cup and end
    cover, the seal ring is damaged and an external
    leakage occurs
  • ? The oil leakage occurs at the mouth of the oil
    storage cup and the oil seal of the brake pump is
    damaged the brake fluid in the high-pressure
    chamber returns to the low-pressure chamber
  • ? Damage of push rod and seal sockets can also
    cause the oil leakage of the oil storage cup.

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  • Case 3
  • Failures
  • The reason why the brake produces squeal during
    braking along with the brake heated?
  • Thread of Judgment
  • ? First, observe which part of the brake caliper
    makes the sound
  • ? The connecting bolt between the brake caliper
    and drive axle is loosened crash or abrasion are
    incurred from the friction
  • ? Hard object is between the brake lining and
    brake disc
  • ? Material quality of brake lining and brake disc.

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  • Case 4
  • Failures
  • The reason why the loader pulls to one side
    during brake ?
  • Thread of Judgment
  • ?The direct reason of pulling to one side is that
    the brake moments of left and right wheels are
    not equal.
  • ?The brake caliper on the side of the wheel is
    jammed and difficult to get away during
    running, which is usually caused by the damage of
    the rectangle seal ring which plays the return
    function in the brake caliper.
  • ?When stepping on the foot brake pedal, the brake
    caliper on one side brakes, but due to the
    internal leakage, the oil-way is jammed or piston
    of the brake caliper is corroded on the other
    side, the brake fluid cannot enter into the brake
    caliper, causing the brake moment inequality
    which results in pulling to one side.

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  • Case 5
  • Failures
  • Why the no brake occurs during the running of
    the loader? How to take the emergency measures?
  • Thread of Judgment
  • ?If a no brake suddenly occurs for the air
    pressure in the air storage tank and oil storage
    in the oil cup of the brake master cylinder
    within the prescribed limit, examine the reasons
    below
  • ?Air chamber apron in the booster pump suddenly
    anti-lips or tears, the compressed air rushes
    into the low-pressure chamber through the seals
  • ?Packing cup of the brake master cylinder
    suddenly anti-lips or tears, the brake fluid in
    the high-pressure chamber rushes into the
    low-pressure chamber
  • ?Air brake valve piston assembly is suddenly
    blocked, and cannot effectively push the intake
    valve core down to open the air inlet
  • ?In an emergency, when no brake occurs
    suddenly, lay the basket flat on the ground, and
    brakes with force downward or reverse gear.

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Case 6 Failures The brake pressure cannot be
increased, why? Thread of Judgment ?Pipeline
failure ?Oil-water separator failure ?Brake
valve failure ?Air compressor failure.
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  • THE END

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