Vehicle Braking Systems Explained

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHATRONICS ENGINEERING
Session: Vehicle Braking System
11/24/2020 16MT407 - Theory of Automobile Engineering 1
MODULE 1

SESSION OBJECTIVES
 On the completion of this session, the students might
be able to understand,
 Proper selection of Braking system for your vehicle.
 Good chosen of braking material for better braking
efficiency.
 Role of electronics in Anti lock Braking system &
Traction control system.

Topics
 Introduction
 Classification of Brakes
 Ant locking braking system
 Traction Control System

INTRODUCTION
INTRODUCTION :
 Causes the vehicle decelerate or stop
 Hold the vehicle in position while stationary.
What happens when brakes applied?
 By applying the brakes to a moving vehicle, the
kinetic energy of the vehicle is transformed into
heat generated by the friction.
 Then the heat energy is dissipated to surrounding
air.

INTRODUCTION
Function of brakes : Purpose
 Stop the moving vehicle in minimum possible
time.
 Controls the speed, in turning & Crowded
places.
 Holds the vehicle in stationary position,
without the presence of drive, after it has
been brought to stop.

INTRODUCTION
Principle of Brake Operation:
 Generally Kinetic energy provided by the engine,
keeps its accelerate from standstill to a desired speed.
 While applying brake, the energy of motion or Kinetic
energy is converted into heat energy generated by the
friction.
 Kinetic energy of the vehicle during braking is,
𝐾 𝐸 =
1
2
𝑚 𝑢2
− 𝑣2
=
𝑊 𝑢2 − 𝑉2
2𝑔
∴ 𝑊 = 𝑚𝑔 𝑜𝑟 𝑚 =
𝑤
𝑔
w = Weight of the vehicles N = mg
m = Mass of the vehicle
u = Initial velocity of the vehicle m/s
V = Final Velocity of the vehicle m/s
g = acceleration due to Gravity = 9.81 m/s2
4 time KE = 4 times Brake Power

INTRODUCTION
Principle of Brake Operation: Frictional Force?
 Opposes the vehicle motion
 Consume power & Produce heat.
 It occurs b/n Tyre & Road surface when the wheels
are locked by brakes.
 To stop vehicle, it mainly rely on co-efficient of friction
b/n the contacting surfaces.
 The amount of energy absorbed by the brakes
depends up-on
 Pressure exerted on brakes
 Co-efficient of friction of brake material
 Brake surface area
 Brake geometry.

INTRODUCTION
Factors Governing Braking: Pressure exerted on the braking surface
 When the pressure applied to two
frictional surfaces, then they grip each
other harder and resist any movement
between them.

INTRODUCTION
Factors Governing Braking: Coefficient of friction b/n braking surface
 On the same surface, for moving different
material required different force.
 Each material has different frictional
characteristics or Coefficient of friction (μ).
 If “μ” is too high – Brakes may be grab or
cause wheel to slide.
 If “μ” is too low – too much pressure is
required on brake pedal to stop the
vehicle.
𝜇 =
𝐹
𝑅 𝑁
F – Tangential braking force or frictional force acting at the contact surface block & Wheel
RN – Normal Reaction

INTRODUCTION
Factors Governing Braking: Frictional Contact Surface
 The bigger brakes stops a vehicle more quickly than
the smaller brakes used on the same vehicle.
 Four wheel brakes stop a vehicle faster than a two
wheel brakes on same vehicle.

INTRODUCTION
Factors Governing Braking: Brake Geometry (Heat dissipation Capability)
 During braking, friction cause heat generation on Pad
& Disc.
 It should be properly dissipated by air. (Absorb by air)
 Mass & Potential speed of the vehicle determine the
size of braking mechanism and the friction surface
area of the pad or shoe.
 No proper heat dissipation - leads to brake fade during
hard or continuous braking.
 What will be happen?
 Lining pad or shoe become glazed
 Disc & Drum becomes hardened
 Now the μ reduced, leads to excessive pressure must
be applied to produce desired braking effect.

INTRODUCTION
Braking Force: FB
 It is the force of resistance applied to stop the vehicle
or reduce the speed..
 It depends on weight of a vehicle & rate of
deceleration which it is stopped.
 Neglecting the following thing FB Calculated.
 Air & gradient resistance
𝐹𝐵 =
𝑊. 𝑎
𝑔
𝑎 =
𝑔 . 𝐹𝐵
𝑊
W – Weight of the Vehicle
a – Rate of Deceleration
g – Acceleration due to gravity = 9.81 m/s2
 Sum of Braking forces of all wheel equal to weight of the vehicle.

INTRODUCTION
Braking Force: FB
 The limiting value of the braking force depends upon
the adhesion of wheel on the road surface.
 The ratio of adhesion to the weight of the vehicle is
called the Coefficient of friction.
𝜇 =
𝐹𝐵
𝑊
𝑜𝑟 𝜇 =
𝑎
𝑔

INTRODUCTION
Maximum Retardation Point
 Brakes applied – Wheels will either roll or skid.
 Depends upon the relative value of Friction b/n
braking surface and friction b/n the tyre & road.
 Jamming of braking surface, increase the friction &
cause wheel skid & more tyre wear.
 The maximum retardation is reached means, wheel
lock condition during braking.
 At this point friction/n Braking surface should equal to
the friction b/n Tyre & Road contact surface.
 In case the friction b/n braking surface is more than
the friction b/n tyre & road, then the brake will lock &
the tyre will start skidding.

INTRODUCTION
Weight Transfer During Braking:
 Effective braking force occurs on the
Ground
 During Braking vehicle weight & Kinetic
energy of the vehicle act through its center
of gravity.
 When applying braking to moving vehicle,
It experience pitching.
 This tendency of the vehicle is known as
“Brake dip”
 Height of Center of gravity of vehicle
above ground level, in relation to the
wheel base & suspension characteristics.

INTRODUCTION
 When applying brake, results in increase
weight on front wheel & decrease weight
on rear wheel.
 Therefore, front brakes absorbs more
kinetic energy than the rear brakes.
 Maximum amount of weight transfer
𝑊𝑇 =
𝜇 ℎ 𝑊
𝑏
When deceleration of vehicle is considered
𝑊𝑇 =
𝜇 ℎ 𝑎 𝑊
𝑏. 𝑔
WT – Weight transferred.
μ – Coefficient of friction
h – Height of center of gravity
from the ground level.
W – Gross weight of the vehicle
b – Wheel Base
a – deceleration of the vehicle
g – Acceleration due to gravity

INTRODUCTION
 During braking, weight is added to the
static weight on the front wheels and
subtracted from the static weight on the
rear wheels.
 The front wheel static weight is normally
55% of the vehicle weight.
 The front brakes are designed to absorb
extra braking effort by selecting suitable
braking system.
 Because, front wheel locks ahead of rear &
cause the vehicle to go straight & not to
spin.

INTRODUCTION
Stopping Distance:
 Distance required to stop a
vehicle during application of the
brake
 By considered a 100% Brake
efficiency, the stopping distance
may calculated.
𝑆 = 𝑢. 𝑡 −
1
2
𝑎. 𝑡2
𝑉2 − 𝑈2 = −2𝑎𝑠
 V = 0 (at end of stop)
𝑆 = 𝑢2/2𝑎
s = Distance moved by the vehicle in m
u = Initial Velocity of the vehicle in m/s
v = Final velocity of the vehicle in m/s
t = Stopping time in s
a = Deceleration of the vehicle in m/s2

INTRODUCTION
Braking Efficiency:
 Ratio of braking force produced to the weight of
the vehicle.
ȠB =
𝐹 𝐵
𝑊
× 100
 Generally less than 100% because of
insufficient road adhesion & Ineffective braking
system.
 Braking efficiency equal to Coefficient of friction.
 If ȠB = 100% means, μ = 1
 Total braking force produced at wheel = equal
to the vehicle weight.
 100% brake efficiency lead injury to passenger
 It generally vary from 50 to 80%

CLASSIFICATION OF BRAKES
Classification of Brakes: According to the purpose of the brakes
Service Brakes/Foot Brakes :
 Operated by foot pedal
 Used while in vehicle moving to stop it.

Classification of Brakes: According to the purpose of the brakes
Hand Brake or Parking Brake :
 Operated by Brake lever or Pedal
 Used to hold the vehicle in position
while stationary
 Helps in parking, Prevent vehicle
rolling @ Different road gradient/Fast
blowing wind.
 Act as Emergency brake, while service
brakes fail or prove ineffective.

Classification of Brakes: According to the construction of brake
Drum Brakes Disc Brakes

Classification of Brakes: According to the Method of operation
 Mechanical brakes
 Hydraulic Brakes
 Vacuum Brakes
 Air Brakes
 Electric Brakes

DRUM BRAKES : Components
Brake Drum : Acts as a braking surface
on wheel side
Wheel Hub : The part which Wheel &
Brake drum is attached

Back Plate : Holds all the brake
components together
Brake Shoe : This will be pushed against
the inner surface of the drum

Brake Lining :
 Provides friction b/n Brake shoe &
Inner surface of drum.
 Causes to slow down the wheel
Hold Down Spring : Holds the Brake
shoe towards the Back plate

Retaining Spring : Retaining the brake
shoe to its Resting position
Wheel Cylinder : Hydraulic Part which
pushes the brake shoe

Self Adjuster Mechanism :
 Modern drum brakes uses self adjuster
mechanism
 Which means when the lining wear's
out, the system aligning the brake shoe
to keep the clearance b/n drum surface
& Brake lining

DRUM BRAKES : Working
 To operate the brake, the brake pedal is
pressed,
 Brake shoes are pushed outwards,
 So the lining is forced against the
drum,
 The force comes from hydraulic wheel
cylinder or from the mechanical linkage
of the parking brake.
 When the brake pedal is released, it
causes the brake shoes to return to
their original position, through the
action of the brake springs.

DRUM BRAKES : Leading & Trailing Shoe
 Shoe which extends in the same direction as
the rotation of the brake drum is known as
leading shoe.
 Shoe which extends in opposite direction is
known as trailing shoe.
 Leading shoe pushed up against the inside of
the drum, and pulled along by its rotation,
causing it to expand out wards.
 Now brake shoe push harder against the drum
by applying even stronger braking force
 Known as self-servo action or self energization
action

DRUM BRAKES : Leading & Trailing Shoe
 Trailing shoe pushed by the brake drum &
apply weaker braking force.
 During trailing shoe pressed against the drum,
the friction caused by the drum rotation
subjects the shoe to forces which are centering
on the anchoring pins.
 Those forces press the shoe inside.
 Thus weakening the pressure on drum.
 Now drum rotation de-energizes the trailing
shoe by forcing it inside.
 In this way the drum speed reduced & Stopped

DRUM BRAKES : Types
Leading & Trailing shoe Type :
 Pivoted at bottom by anchor
 Opened by Wheel cylinder at
Top.
 One leading & Trailing shoe
provide constant braking force at
all time to stop vehicle.
 Used in Small rear wheel drive
cars & Front wheel drive cars

DRUM BRAKES : Types
Two Leading Shoe : Single acting type
 Unidirectional wheel cylinders are
mounted in top & bottom of the brake
drum.
 Both shoe can have self servo action
during vehicle forwarding
 High degree of braking force is generated.
 But it will reduced during vehicle
reversed.
 Because now both the shoe experience
trailing
 Used in front brakes, before the use of
disc brakes

DRUM BRAKES : Types
Two Leading Shoe : Double acting type
 Bidirectional wheel cylinders are
mounted on the top & bottom of the
brake shoes
 Provide high degree of braking force @
forward & Reverse direction of Vehicle.

DRUM BRAKES : Types
Duo Servo Type:
 Similar to Leading & Trailing shoe type
 Here brake shoes are not connected to backing
plate,
 Rather they are connected each other by a shoe
adjuster
 Advantages is both shoe act as a leading shoe.
 Disadvantage, does not provide constant braking
force

DRUM BRAKES : Brake Shoes
 Made of two parts of pressed steel
 Shoe rim & Shoe web
 Shoe rim curved profile closely match with drum inner surface
 Brake lining is attached to the rim Surface
 It has series of bent areas on the edges, where the shoe rest against the
backing plate
 Shoe web welded to the rim for
reinforcement to rim
 The other part of the brake drum like anchor,
return spring, parking brake attachment, and
adjusting mechanism are attached to the
shoe web
 Al – Shoe - good Heat dissipation, less weight

DRUM BRAKES : Brake Lining (Bonding Attachment)
 Made up of Friction material.
 Two methods followed to attached with brake shoe.
 Bonded lining is attached to shoe by high temperature
adhesive.
 Procedure
 First cleaning the break shoes
 Lining surface roughened by sanding
 The adhesive then applied to both liner & Shoe
 Then placed into the high temperature oven (150oC
to 200oC
 After curing the brake shoe is removed & allowed to
cool
 Bonded lining is preferable

DRUM BRAKES : Brake Lining (Riveting Attachment)
 Attached to the Brake shoe by a series of Brass or
Aluminum rivets.
 The rivets are pass through countersunk hole on lining
 The rivets are flattened inside the shoe rim to hold the
lining tightly in place

DRUM BRAKES : Brake Lining Material
Function :
 Designed to produce heat from friction.
 As it rubs against the rotating drum surface.
 Also known as friction material.
 Not to cause excessive wear to drum & Disc surface.
 Able to operate at high temperatures without failure.
 Made by Organic or metallic material.

DRUM BRAKES : Organic Lining
Moulded Type :
 Made of mixed compound asbestos, filler material, Powdered resin.
 Asbestos – Silicate mineral called as rock forming minerals
 Form from Serpentinite/Amphibole rocks
 Filler material - Improves coefficient of friction & Gives good
bonding b/n asbestos & resin
 To reinforce the brake lining.
 Generally Barium sulfate (barytes) used as filler material.
 Resin – Mixtures of organic compounds.
 BLR 140 - melamine resin add with Brake lining to improve
thermal & mechanical properties of friction material
 Melamine formaldehyde – organic compound (Thermosetting
plastic)
Asbestos
Serpentinite
Rocks

Moulded Type :
 The mixture organic compound is Moulded in dies to
form into shape & is placed under heat & pressure until
hard
 To get a state like Board
 After it will cut into individual segments & attached with
Brake shoe

Woven Type :
 Form from strands of Asbestos & Threads of Other
material
 And impregnated (Soak) with rubber compound
 To form organic lining for brake shoe.

DRUM BRAKES : Metallic Lining
Sintering Method :
 Process of compacting & Forming of solid mass of material by heat or pressure,
without melting it to the point of liquefaction.
 Made of sintered metal has a composition of fine powdered Copper or iron,
Graphite and some amount of inorganic fillers and friction modifier
 Inorganic Fillers – Silicon Carbide,Clacium carbonare, Dolomite, etc
 Graphite (Crystalline Carbon), Carbon – Friction modifier
 Finally lubricating oil is added for avoid segregation of different materials.
 Required form of Lining is formed by some special process like heat treatment,
etc.
 Frictional qualities is more constant than organic lining
 It can be used in Police cars, Fire brigade vehicle, Sport cars

DRUM BRAKES : Backing Plate
 It is the base unit, where all the component is
attached,
 It is fixed with rear axle or steering Knuckle.
 The anchor pin is a steel pin welded or riveted solidly
to the backing plate or threaded into steering
Knuckle through the backing plate
 It has various projection, where it holds the position
of Brake shoe & Drum.
 It also contains holes and bosses for attaching wheel
cylinder, shoe hold-down spring, and parking brake
lever

DRUM BRAKES : Brake Drum
 Made of cast iron
 Requires, Good strength, Wear Resistance, It
should Absorb heat.
 For improves heat dissipation, fins added with its
circumference

DISC BRAKES : PRINCIPLE
PASCAL’S LAW :
 The system works based on Pascal’s Law
 “Pressure Exerted anywhere in a contained
incompressible fluid is distributed equally in all
direction

DISC BRAKES : PRINCIPLE PASCAL’S LAW : Example

DISC BRAKES : COMPONENTS

DISC BRAKES : COMPONENT
Disc Rotor :
 Part of the disc brake
 Squeeze by Brake pads
 During braking, heat will generate
because of friction,
 That decelerate the wheel
 Stud holes helps to dissipate heat
from disc by allowing more air
into it.
 Optimum cooling performance is
achieved.

Housing Part :
 Also called as Caliper
 Mounted on steering Knuckle
 Through Banjo Fitting The fluid
enters into the housing
 Causes the piston to come out
with great force
 To squeeze the pads against the
Rotating Disc
 Comes in two types
 Floating Caliper design
 Fixed caliper Design

Housing Part : Floating Caliper Type
 Either comes with one piston or two
piston
 During outer pad squeeze the disk,
the caliper can slide along vehicle
frame.
 In general floating type single piston
is used on light cars.

Housing Part : Fixed Caliper Type
 Caliper solidly fixed to the steering
Knuckle.
 It uses a pair of piston.
 Located on both side of caliper
providing equal force each pad.
 It’s also incorporate one or two
piston on each side (depends on
vehicle)
 The inboard piston applies pressure
to the inner pad
 Outboard piston applies pressure to
the outer pad

Brake Pad :
 Consists of a block of friction material attached to
a stamped steel backing plate.
 The brake pad material is bonded to the backing
plate with a high temperature adhesive.
 A slit is provided on the face of the pad to indicate
the allowable limit of the pad wear.
 It also provide a path for brake dust and gas to
escape .

Brake Pad wear indicator :
 Some times attached to the one of the pads.
 Simple steel plate
 Helps the drive to notice about pad replaceable
time
 Via a screeching Noise.
 If he not notice it properly, leads to irreparable
damage to disc.

Pad to Disc Clearance Adjustment :
 Similar to self adjuster mechanism in drum brake.
 Automatic adjustment of the pad to disc clearance
is done whenever the brake is operated
 A deformable seal is placed inside the machined
groove in the housing.

DISC BRAKES : Working

Brake Fade :
 Brake drums and discs are forced to absorb
a significant amount of heat during braking..
 It describes heat generation is faster rate
than a capable of heat dissipation to
atmospheric air.
 Happen during repeated hard stops,
Overheating
 Leads to Ineffective braking or even brake
failure.
 Two causes for brake fade
 Mechanical fade
 Lining Fade

Brake Fade :
Mechanical Fade:
 Due to brake drum over heats & expand
away from the brake lining.
 Results increased brake pedal force during
travel.
Lining Fade:
 Affects both drum & Disc brake.
 Affects when the friction material overheats
to the point where the co-efficient of friction
drops off.
 In this moment Friction is reduced and
brake ability to convert added heat is
reduced

Disc Brake vs. Drum Brake :
DISC BRAKE Drum Brake
Non – energized, Non servo Brakes Self energizing , Servo brakes
Brake pad pressure is directly proportional to
brake pedal pressure
Not directly proportional
More stable Less stable
Brake disc generally stays cleaner
Drum collects all the contaminants due to
centrifugal force
Remains cooler under repeated severe
braking
Heat increase under repeated severe braking
Clamping action of disc brake pad causes no
distortion of the disc
Spreading action of drum brake shoes cause
the drum to elongate into elliptical or oval
shape
Brake pad can easily replaced Not be easily replaced
More cost Less cost
High pedal pressure is required No high pedal pressure required
Difficult to install parking brake Easy to install parking brake

Hydraulic Braking System:
 Brakes which are operated by means of
hydraulic pressure known as Hydraulic Brakes
 Works on the principle called “Pascal’s Law”
 All modern automobile brake systems use a
hydraulic system to transmit the forces from
the brake pedal to brake shoe or Brake pad
Main Components :
 Brake Pedal
 Master Cylinder
 Drum Brakes – PCV & Wheel Cylinder
 Disc Brakes

Hydraulic Braking System: Master Cylinder
 Major components of Hydraulic braking system.
 Converts the pressure applied to the brakes into
hydraulic pressure.
 Maintains the constant volume of the fluid in the brake
lines, since it has a reservoir.
 Reservoir cap equipped with float sensor about the fluid
level in the tank
Master Cylinder
Single Master
Cylinder
Tandem Master
cylinder

Single Master Cylinder : Construction
 Consists two portion, Namely Cylinder &
Reservoir.
 In reservoir Filer cap contains air vent, so
fluid can expand & Contract and still at
atmospheric pressure.
 Main cylinder has piston, Primary cup &
Secondary rubber cups, Return Spring,
Outlet check valve & a rubber seat.
 Rubber boot covers the push rod end of
the cylinder, to prevent dirt into the
cylinder.

Single Master Cylinder : Working
i. When brake pedal is pressed?
 Piston inside the cylinder forces the
fluid into the brake line.
 Fluid pressure built up in the brake
system.
 The fluid pressure acts at the piston in
the wheel cylinder or caliper.
 The outside movement of piston
causes brake pad to come into contact
with brake shoe & disc
 There by brakes applying

Single Master Cylinder : Working
i. When brake pedal is Released?
 Piston return spring move the piston
very rapidly.
 This cannot compensate by fluid
movement.
 So partial vacuum creates inside the
cylinder.
 Now fluid from intake port moves via
hole in the piston & fill the vacuum in
the cylinder.
 In contrast, fluid pressure in the line
open the outlet check valve.

Tandem Master Cylinder :
Construction
 Tandem means – inline
 Master cylinder contains two
piston in it’s inline to each other
with in a single cylinder.
 Primary piston contains two
rubber cups.
 Secondary piston contains three
rubber cups.
 Secondary cups on secondary
piston slightly different.

Working
i. When brake pedal is
pressed?
 Primary piston operation is
same as single master
cylinder.
 Secondary piston operates
by pressure built up in the
primary section
 Here the hydraulic
pressure delivered to two
independent brake lines

Working
released?
 Primary piston returns to
the retaining ring at the
end of the cylinder.
 Primary & Secondary
spring length & strength
determines the secondary
piston position during
returning.

Working
released?
 The piston stop bolt
ensure the secondary
piston return & its position
after brake release.

Advantage:
 If any leakage on any one
piston side also ensure the
brake pressure on non failure
side.
 Front wheel drive cars use a
diagonal split system.
 One piston supply pressure for
front right brake & rear left
brake
 Similarly other piston supply
pressure in opposite manner.

Advantage:
 In diagonal split system ensure
the 50% of the braking power
on one line, even failure in the
system.

Hydraulic Braking System: Proportional control valve (PCV)
 During braking, the weight of the
vehicle transfer to front portion of
the vehicle.
 Increase load on front portion,
makes the front brakes less prone
to locking.
 Meanwhile, rear wheel side load is
reduced, which increases the
possibility to lock the rear wheels.
 It causes the rear wheel to skid &
the vehicle is spin.
 The PCV is provided to reduce & maintain the rear brake pressure & maintain
with its limit.

Construction :
 Input port receive brake fluid from
master cylinder.
 A plunger actuated valve body held
open by spring force.

Working :
 When apply brake pedal, the brake
fluid pressure is transmitted to the
rear brakes via PCV

Working :
 When pressure on rear brake line
increase.
 It over come the spring force inside
the valve.
 & make it move downward.
 Now the plunger is contact with the
lip seal.
 Closing off the brake line.
 In this moment equal pressure on
Master’s & Rear wheel brake’s
 No pressure is transmitted to the
rear wheel

Working :
 When pressure is increased in
master side.
 Plunger is pushed up against the
spring
 Open valve to rear brake line.
 Now pressure is transmitted to rear
line’s.
 This cycle is continued & prevent
pressure surges on rear side
 Also prevent wheel lock
 For maintain the stability of the
vehicle.

Hydraulic Braking System: Wheel Cylinder
Construction :
 Cylinder Body made of cast iron or
Aluminum
 It is mounted on backing plate, inside the
brake drum.
 Cylinder body contains two holes
 Inlet port
 Bleeder valve
 Inlet port : Give hydraulic pressure to
extend the cylinder piston for apply brakes
 Bleeder Valve : Helps to remove air from
the system.

Construction :
 From the expanded view,
 It has two pistons with push rod
 Piston cups
 Piston cup expanders,
 Piston expanders
 Retain Spring
 Dust Boot

Working :
 When the brakes are applied, pressure is
transferred to the wheel cylinder.
 The fluid pressure behind the piston cup,
expands the piston with the help of
expander
 Now the push rod on the piston pushes the
brake pad against the drum inner surface
 To stop it’s rotation motion.
 When brakes released, the piston retracts
with the help of return spring.
 Now brake is released.

Pneumatic Braking system: Air Brakes
Working :
 In larger vehicle, even a hydraulic brakes
with vacuum booster not give effective
braking.
 It requires high power braking
 Air brakes resolves in heavy vehicles such
as, Trucks, Highway vehicle, etc.
 The air pressure is required about 900 Kpa.

Construction :
 It consists of a Air compressor unit,
Air reservoir tank, brake valve, series
of brake chambers, unloader valve,
pressure gauge and a safety valve.
 Compressor is driven by engine.
 It stores the air at reservoir
 Brake valve is operated by foot pedal.
 It is further connected to the brake
chamber
 Each brake shoe contains separate
brake chamber
 It has cam mechanism to apply brake

Working : Hand Brake on

Working : Hand Brake Release

Working : Pedal Brake Applied – Service brakes on

Working : Pedal Brake Release – Service brakes off

Antilock Brake system
 Prevents of the wheels of a vehicle from locking, when the brakes are applied.
 Maintain ability to steer the vehicle.
 Locking of front & Rear wheels of a vehicle is extremely dangerous.

 Hard brakes applied while Vehicle’s moves on slippery road surface
 Tends to front wheel locks.
 Now driver loss his control of direction and vehicle still move in a current
direction.
 Impact happens - It hit obstacle.
 If Rear Wheel locks – vehicle
starts to spin
 Now the stability of the vehicle
is affected.
 ABS Intelligently works on
such a way to prevent wheel
lock at panic situation.

 Amount of Tyre slip is known as slip factor.
 ABS works on this principle to control the brake pressure.
 Always maintain the Ideal slip factor.
 It can be derived from Vehicle speed & Wheel speed.
𝑆𝑙𝑖𝑝 𝑓𝑎𝑐𝑡𝑜𝑟 =
𝑉𝑒ℎ𝑖𝑐𝑙𝑒 𝑆𝑝𝑒𝑒𝑑 − 𝑊ℎ𝑒𝑒𝑙 𝑠𝑝𝑒𝑒𝑑
𝑉𝑒ℎ𝑖𝑐𝑙𝑒 𝑆𝑝𝑒𝑒𝑑
 Automatically controls the brake to keep the wheels in rotating condition.
 Helps the inefficient drive to apply brake safely, during hard situation.
 Driver get Steerability control of vehicle.
 Braking force limiting the performance characteristics of the vehicle.
 But ABS does not enhance it.
 It ensure that brakes operate with maximum efficiency to stop the vehicle at
minimum distance.

Antilock Brake system : Working
Speed Sensor : Provides wheel lock up
information to ECU unit.
Modulator : Controls the brake fluid
pressure to each wheel.
Electronic Control Unit :
 Controls the complete system
operation.
 Receives the signal from the wheel
sensor & controls the modulator.

 At panic situation, the wheel sensors
detects any sudden changes in wheel
speed.
 ECU – constantly monitor the vehicles
speed and compares signals received
from four wheel speed sensor.
 Calculate the slip ratio of each wheel
 Instruct the modulator to provide
optimum brake pressure
 Resulting in, wheel speed recovers to a
level which locking does not occur.

 Then ABS ECU – give signal to
modulator to reapply brake by
increasing the fluid pressure.
 Now the wheel speed drops to a level
which the locking can occur.
 This cycle continuous until the vehicle
stop with a minimum distance

Traction Control System : Tractive effort
 Traction is a force used to generate
motion between a body and a
tangential surface using dry friction.
 Accelerating of a vehicle is limited by
two factors
 Power of the engine
 Traction force b/n tyre & road
surface
 What happen if traction loss in
vehicle?
 Increase the risk of skidding
 Loss of control
 Collision

Traction Control System : Tractive effort
 What factors derive traction loss to a vehicle?
 Ice or snow roads
 Standing water on road
 Mud near farm entrance, Construction sites,
Truck crossings,
 Wet leaves on roads
 Broken or uneven road surface
 Sand or gravel found in rural areas, while
approaching curves
 Accelerating & braking too hard
 Steering too much or Quickly steered
 Enter curve with too much speed
 These factors leads to vehicle skid

Traction Control System : Need
 Thus it necessary to have traction control in order to maintain the vehicle
motion in adverse conditions like slippery or in climbing hills.

Traction Control System vs. ABS :
TCS ABS
In TCS apply brakes when the wheels
try to spin and loose traction
An ABS releases the brakes, when
wheel go into locking
It increases the traction force &
provides acceleration to the vehicle
Provides good steering, while braking
in slippery surfaces
 It is active vehicle safety feature designed to help the vehicle make effective
use of all the traction available on the road. When accelerating in slippery
condition.

Traction Control System : Working
 Compares the rotational speed of the
drive wheels of the vehicle with the help
of speed sensors of ABS.
 If any wheel encounter slippery surface
means, rotate with exceptionally high
speed.
 Then it considered as spinning wheel
 TCS immediately sends the signal to
apply brakes to cut of the power
delivered to the vehicle.
 Therefore opposite wheel on that same
axle produce more torque to drive the
vehicle.

Traction Control System : Other ways
 Brake force apply to one or more wheel
 Reduction or suppression of spark sequence to one or more cylinders.
 Reduction of fuel supply to one or more cylinders.
 Closing the throttle, if the vehicle is fitted with drive by wire
 In turbocharged vehicles, a boost control solenoid is actuated to reduce the
boost power, thereby to reduce the engine power for wheels.

END

Vehicle Braking Systems Explained

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