hydraulic braking systems
Post on 12-Sep-2014
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HYDRAULIC BRAKING SYSTEMS
KAJA KRISHNA PHANI
BTE-09-020
AGRICULTURAL ENGINEERING COLLEGE & RESEARCH INSTITUTE
TAMILNADU AGRICULTURAL UNIVERSITY
The technology of controlling pressurized fluids to create
force and motion is known as Hydraulics .
HYDRAULIC PRINCIPLES:
Fluids cannot be compressed
Fluids can transmit Movement
Acts “Like a steel rod” in a closed container
Master cylinder transmits fluid to wheel cylinder or caliper piston bore.
Fluids can transmit and increase force
PRESSURE =FORCE / AREA
Kinetic Energy as a Function of Speed and Mass
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
180,000
30 60 90 120Speed kph
Ene
rgy
N-M
200 kg
250 kg
290 kg
Of course ,the final contact between vehicle and road made through tyres -hence it is of great importance in braking system.
Bald or defective tyres will even make the best brakes ineffective.
The braking systems which works with the help of hydraulic
principles is known as hydraulic braking systems.
HYRAULIC BRAKING SYSTEM CAN BE OPERATED BY
Vacuum, Hydro or Motor assisted
Disc System
Drum System
Dual System
DRUM BRAKE
MASTER CYLINDER
DISK BRAKE
BRAKE PEDAL
HYDRAULIC PRESSURE IS DISTRIBUTED EQUALLY IN ALL DIRECTIONS
BY THE SAME PRINCIPLE ……….
SAME LINE OF PRESSURE WILL BE EXERTED ON ALL WHEELS
The Hydraulic pressure is the same, but the applied force can be changed by the piston size.
The applied
pressure can be
raised or
lowered by
piston size
Provides a reservoir for brake fluid and contains the driving pistons in the hydraulic circuitTHEY ARE OF 2 TYPES
Front - Rear split
-One piston for front brakes and one for rear
-If a leak occurs you could lose front brakes
Diagonally split
-One piston drives one front wheel and one rear wheel
-Diagonal layout allows you to maintain directional control if a leak occurs
MASTER CYLINDER
DRUM BRAKES
Expanding shoes create force on the inner surface of the drum
Used on the rear of some trucks and SUV’s
Self-energizing design requires less activation force
Require periodic adjustment
DISC BRAKES
DISK BRAKES WORKS WITH THE HELP OF CALIPERS
FIXED CALIPERS Calipers are disc brakes that use a caliper that is FIXED
in position and does not slide.
-They have pistons on both sides of the disc.
-There may be 2 or 4 pistons per caliper
FLOATING CALIPERS-Much more common
-Single Piston
-Easier to work with
-On “inboard” side of caliper
Calipers are of two types
FIXED CALIPER
Applies two pistons to opposite sides of rotor
Caliper stays stationary
Disc Brakes require higher hydraulic pressure
APPLICATIONS-Motorcycles and some import trucks and cars use this type
-Similar to bicycle brakes
.Applies pressure to two pads on opposite sides of rotor
.Caliper
-Sliding -Fixed
.Friction Material exposed to air
SLIDING CALIPER
FRONT WHEEL LOCK
THIS CONDITION WILL OCCUR IF THERE IS MORE FRONT BRAKE TORQUE
THAN DYNAMIC FRONT WEIGHT
REAR WHEEL LOCK
THIS CONDITION WILL OCCUR IF THERE IS MORE REAR TORQUE THAN DYNAMIC REAR WEIGHT
OPTIMUM BRAKING
Optimum braking is achieved when brake torque distribution matches
dynamic weight distribution
TO ACHIEVE THIS CONDITION PROPORTIONATING VALVES ARE USED
When a vehicle brakes , weight is transferred to the front.the nose will dip as it gets heavier and rear will rise as it gets lighter.The rear needs less hydraulic pressure.
Proportionating valves are used to provide balanced braking
by reducing hydraulic pressure to rear wheel
When a large variation at axle loading takes place, such as railway wagons ,
trucks ,load or height sensitive proportionating valves regulate more hydraulic
pressure to the rear axle in the amount needed.
Some vehicles with front/ rear split braking systems have a proportionating
valve by-pass which allows full pressure to rear axle if front brakes fails.
SOME TYPES OF PROPORTIONATING VALVES
BRAKE BOOSTER OR SERVO UNIT
Mounted on firewall between the brake pedal and master cylinder ,brake boosters
vary in size andd can be single or double diaphragm
POWER BOOSTER IN CLOSED POSITION
Brake booster have two chambers :one at front which is always at constant and
another at the rear where pressure varies they are by a pressure plate and are
sealed from one another by a rubber diaphragm.
There is a vacuum in the manifold of all 4-stroke petrol engines .Boosters use
this increase the force applied to master cylinder from 3- 5 times without loos
-ing brake sensitivity or response and with reduced pedal effort.
On diesel engines, an auxiliary vacuum pump is utilised to supply vacuum.
If the engine stops this will retain enough vacuum in the booster for upto 3
brake applications.
TYPES OF BOOSTERS
Properties of Brake Fluid
Does not thicken or then with changing heat
Must not boil
Must be compatible with brake parts material
Must lubricate internal parts
Must not evaporate easily
BRAKE FLUID
The fluid through which the energy is passed in hydraulic braking systems is
known as BRAKE FLUID
THANK YOU