Types of Brake System

Types of Brakes

        Brakes may be broadly described as using friction, pumping, or electromagnetics. One brake may use several principles: for example, a pump may pass fluid through an orifice to create friction:

1.     Frictional Brake

2.     Pumping Brake

3.     Electromagnetic Brake

4.     Hydraulic Brake

5.     Air Brake

6.     Anti-Braking System(ABS)

Frictional brakes: 

                                Are most common and can be divided broadly into "shoe" or "pad" brakes, using an explicit wear surface, and hydrodynamic brakes, such as parachutes, which use friction in a working fluid and do not explicitly wear. Typically the term "friction brake" is used to mean pad/shoe brakes and excludes hydrodynamic brakes, even though hydrodynamic brakes use friction.

                                Friction (pad/shoe) brakes are often rotating devices with a stationary pad and a rotating wear surface. Common configurations include shoes that contract to rub on the outside of a rotating drum, such as a band brake; a rotating drum with shoes that expand to rub the inside of a drum, commonly called a "drum brake", although other drum configurations are possible; and pads that pinch a rotating disc, commonly called a "disc brake". 

                                Other brake configurations are used, but less often. For example, PCC trolley brakes include a flat shoe which is clamped to the rail with an electromagnet; the Murphy brake pinches a rotating drum, and the Ausco Lambert disc brake uses a hollow disc (two parallel discs with a structural bridge) with shoes that sit between the disc surfaces and expand laterally.

                                        

Pumping brakes: 

                            Are often used where a pump is already part of the machinery. For example, an internal-combustion piston motor can have the fuel supply stopped, and then internal pumping losses of the engine create some braking. Some engines use a valve override called a Jake brake to greatly increase pumping losses. Pumping brakes can dump energy as heat, or can be regenerative brakes that recharge a pressure reservoir called a hydraulic accumulator.

 Electromagnetic brakes: 

                                            Are likewise often used where an electric motor is already part of the machinery. For example, many hybrid gasoline/electric vehicles use the electric motor as a generator to charge electric batteries and also as a regenerative brake. Some diesel/electric railroad locomotives use the electric motors to generate electricity which is then sent to a resistor bank and dumped as heat. Some vehicles, such as some transit buses, do not already have an electric motor but use a secondary "retarder" brake that is effectively a generator with an internal short-circuit. Related types of such a brake are eddy current brakes, and electro-mechanical brakes (which actually are magnetically driven friction brakes, but nowadays are often just called “electromagnetic brakes” as well).

Hydraulic Brake:

                            Hydraulic Brake is an arrangement of braking mechanism which uses brake fluid, typically containing ethylene glycol, to transfer pressure from the controlling unit, which is usually near the operator of the vehicle, to the actual brake mechanism, which is usually at or near the wheel of the vehicle.

The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following:

a) Brake pedal or lever

b) A push rod (also called an actuating rod)

c) A master cylinder assembly containing a piston assembly (made up of either one or two pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir)

d) Reinforced hydraulic lines

e) Brake calliper assembly usually consisting of one or two hollow aluminium or chrome-plated steel pistons (called calliper pistons), a set of thermally conductive brake pads and arotor (also called a brake disc) or drum attached to an axle.

                        At one time, passenger vehicles commonly employed drum brakes on all four wheels. Later, disc brakes were used for the front and drum brakes for the rear. However, because disc brakes have shown a better stopping performance and are therefore generally safer and more effective than drum brakes, four-wheel disc brakes have become increasingly popular, replacing drums on all but the most basic vehicles. Many two-wheel vehicles designs, however, continue to employ a drum brake for the rear wheel.

Air Brake System:

                               It is the brake system used in automobiles such as buses, trailers, trucks, and semi-trailers. George Westinghouse created air brakes for utilizing it in trains for railway service. A secured air brake was patented by him on 5th, March 1872. At first air brake is produced for use on trains and now it is used commonly in automobiles. Westinghouse made various modifications to enhance his creation, directing to several appearances of the automatic brake which was extended to include road vehicles.

 

Compressed Air Brake System: 

                               It is a different air brake used in trucks which contains a standard disc or drum brake using compressed air instead of hydraulic fluid. Most types of truck air brakes are drum units, though there is a growing trend to the use of disc brakes. The compressed air brake system works by drawing clean air from the environment, compressing it, and hold it in high-pressure tanks at around 120 PSI.     

                             Whenever the air is needed for braking, this air is directed to the functioning cylinders on brakes to activate the braking hardware and slow the vehicle. Air brakes use compressed air to increase braking forces. The large vehicles also have an emergency brake system, in which the compressed air holds back a mechanical force using springs which will otherwise engage the brakes. If air pressure is lost for any reason, the brakes will hold and vehicle is stopped.

 

Design and Function: 

                                    The Compressed air brake system is separated into a control system and supply system. The supply system compresses, stores and provides high-pressure air to the control system and also to other air operated secondary truck systems such as gearbox shift control, clutch pedal air assistance servo, etc.,

Control system:

                            The control system is separated into two service brake circuits. They are the parking brake circuit and the trailer brake circuit. These two brake circuits are again separated into front and rear wheel circuits which gets compressed air from their individual tanks for more protection in case of air leak. The service brakes are applied by brake pedal air valve which controls both circuits. The parking brake is the air-controlled spring brake which is applied by spring force in the spring brake cylinder and released by compressed air through the hand control valve.

                            The trailer brake consists of a direct two-line system the supply line which is marked red and the separate control or service line which is marked blue. The supply line gets air from the main mover park brake air tank through a park brake relay valve and the control line is regulated through the trailer brake relay valve. The working signals for the relay are offered by the prime mover brake pedal air valve, trailer service brake hand control, and Prime Mover Park brake hand control.

 

Supply system: 

                        The air compressor is driven off of the automobile engine by crankshaft pulley through a belt or straightly off of the engine timing gears. It is lubricated and cooled by the engine lubrication and cooling systems. The Compressed air is initially directed through a cooling coil and into an air dryer which eliminates moisture and oil impurities and also contains a pressure regulator, safety valve and a little purge reservoir. The supply system is outfitted with an anti-freeze device and oil separator which is an alternative to the air dryer. The compressed air is then stored in a tank and then it is issued through a 4 - way protection valve into the front and rear brake circuit air reservoir, a parking brake reservoir and an auxiliary air supply distribution point. The Supply system also contains many check, pressure limiting, drain and safety valves.