2. Braking system
The braking system used in automobiles is mainly used for helping the driver control
the deceleration of the vehicle.
It is one of the crucial systems, which is especially designed for decreasing the speed
of the fast moving vehicle.
A typical automobile braking system comprises of a braking device having different
components, which are used for slowing or stopping down a vehicle.
More precisely, these devices decrease or stop the speed of a moving or rotating body
by absorbing kinetic energy mechanically or electrically.
These systems automatically control wheel slips and prevent the wheels from
spinning.
They are widely used in motor vehicles, buses, trucks, trains, airplanes, passenger
coaches, trailers, and other types of automobiles.
Brake systems used in automobiles has come a long way in recent years.
The adoption of anti lock brake systems along with the introduction of different brake
components made of carbon fiber, steel, aluminum etc have really provided better
stopping performance in comparison with traditional braking systems.
The major manufacturers of brake systems in the world are Bendix, Bosch, Delco,
Continental Teves, Kelsey-Hayes, Nippondenso, Sumitomo, and Toyota.
3. Friction and Braking
Friction is the resistance to motion between two objects in
contact with each other.
It varies with the force applied between the sliding surfaces, the
roughness of the surfaces, and the material of which the surfaces
are made.
The three types of friction are dry, greasy, and viscous.
The automotive braking system uses dry friction to produce braking
action.
Friction in vehicle brakes
When the brakes are applied by pushing down on the brake pedal
A fluid flows through tubes or brake lines to the brake mechanisms at
the wheel.
The brake mechanisms apply force on rotating parts so the wheels are
slowed or stopped.
4. Two types of wheel-brake mechanisms
Drum brake : fluid pressure pushes lined braked shoes
against a rotating drum
Disk brake: the fluid pushes lined brake pads against a
rotating disk.
If the brakes are applied so hard that the wheels lock,
The friction between the tires and road is kinetic friction
If the brakes are applied less hard, the wheels continue to
rotate
The friction between the tires and road is static friction
6. Principle of operation
Braking begins at the brake
pedal.
Figure shows that there are two
pistons in the master cylinder.
The spaces ahead of the pistons
form two pressure chambers.
When the pedal is pushed down
closed to the end of master
cylinder, brake fluid is forced
from,
the front pressure chamber of
master cylinder to the front wheel
brakes and
the rear pressure chamber of the
master cylinder to the rear-wheel
brakes.
As the hydraulic pressure
increases, brake shoes or brake
pads are forced against the
rotating drums or discs.
The resulting friction slows or
stops the wheels and the vehicle.
7.
8.
Problem #1
The traction force of the vehicle is 12.25 kN which traveling
speed is 120 km/h. If the wheel radius of the vehicle is 20 cm
and 23% of the total power losses due to the braking system,
determine how much power should be available at the engine
crankshaft. Also determine how much develops over the
piston due to the burning of A/F mixture if the crank radius is
considered to be 5 cm and rotational speed is 2400 rpm. The
gear ration is given as 1:1.
