1.3. Functions, Necessity and Working principles of the brakes
1.3.1. Function of the automotive brakes:
The brake system is designed to slow down and halt the motion of the vehicle. A brake is a mechanical device which inhibits motion. Brakes are generally applied to rotating axles or to wheels. Brakes are essentially a mechanism to change energy types.
A common misconception about brakes is that brakes squeeze against a drum or disc, and the pressure of the squeezing action slows the vehicle down. This is in fact a part of the reason for slowing down a vehicle.
When brake (i.e. Torque) applied to wheel, braking force is created that force oppose the speed of wheel or rotation of force. Brakes are employed to stop or slow down the speed of vehicle within the minimum possible distance and time.
1.3.2. Necessity of a braking system:
In any brakes, (if the pressure from accelerator pedal is removed), the vehicle tends to slow up because of wind resistance, drag of engine and road friction. These forces, of course, would stop the vehicle but in the present day traffic, this, would be quite impracticable and dangerous.
The braking system provides added friction to overcome motion and to slow up and stop the Vehicle.
Early in automobile development, the brakes played a rather subordinate role because the friction in the drive train was so great that a vehicle was slowed sufficiently even without the brakes being used.
Increasing power and speed as well as constantly increasing traffic density led to the consideration in the 20s of how an appropriate brake system could provide a counterbalance to greater power and driving performance.
1.3.3. Working principles of brakes: A conversion of energy:
The momentum or kinetic energy developed by the vehicle when in motion is converted into heat energy due to friction between brake shoes and drums which is dissipated into the surrounding air i.e. conversion of energy.
This all happen by the application of brake. It undergoes to say that the brakes are one of the most important speed control system of the vehicle.
They are required to stop the vehicle within the smallest possible distance and this is done by converting the kinetic energy of the motion of the vehicle into the heat energy which is dissipated into atmosphere.
And therefore say that the automobile brake system works on the “principle of conversion of energy”.
But now days, most commonly modern brake’s used friction to convert kinetic energy into thermal energy (heat) and this heat is converted into useful required energy, though other methods of energy conversion may be employed.
For example regenerative braking system converts much of the energy to electrical energy, which may be stored for later use.
Other methods convert kinetic energy into potential energy in such stored forms as pressurized air or pressurized oil.
Eddy current brakes use magnetic fields to convert kinetic energy into electric current in the brake disc, fin, or rail, which is converted into heat. Still other braking methods even transform kinetic energy into different forms, for example by transferring the energy to a rotating flywheel.
And these are all about the examples of “principles of energy conservation” for how to save energy or energy management or utilization.
Two forms of friction play important role in automotive braking are:
Kinetic friction
Static friction
Braking action creates kinetic friction in the brakes and static friction between the tyre and road to slow the vehicle.
When brakes are applied, the vehicle’s weight is transferred to the front wheels and is unloaded on the rear wheels as shown in Fig. 1.1.
The brake system converts the kinetic energy of the moving vehicle into the heat. Various components are used in braking system to convert the momentum (Kinetic energy) in to heat energy using friction.
Actually brakes use friction of brake shoes and drums to convert kinetic energy developed by the vehicle into heat energy. When we apply brakes, the pads or shoes that press against the brake drums or rotor convert kinetic energy into thermal energy (heat) via friction. A Fig. 1.1 shows that the braking action while car is in moving.
Next blog: Classification of Automobile Brakes
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