Golden Dragon XML6125CLE Repair Manual Download

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BR-2 Brake System BR-6125J93C-01

Structure and working principles of brake system

The driver, according to the road and traffic conditions and by a series of special devices provided in the car,

forces the road to exert on the wheels an external force in a direction that is contrary to the car travel direction, so as to
realize an enforced braking of the car. This external force controlling the car brake is called braking force and the series
special devices for producing the braking force is called braking system. The braking system is used to stop the car at a
reduced speed and to realize a parking brake.

Composition of brake system

Energy supply device: including all parts that supply and adjust the energy required by braking and improve

the energy transmission medium status. The part producing the braking energy is called the braking energy
source. Human body can also be a braking energy source;

Control device: including all parts that produce braking actions and control braking effect, such as brake

pedal and brake valve;

Transmission device: including all parts that transmit the braking energy to the brake, such as quick release

valve and relay valve;

Brake: Parts producing braking friction torque, such as brake drum and brake shoe;

Additional devices: braking force adjusting device (such as ABS), warning device, pressure protection device,

etc.

Mechanism of brake system
The brake system pipeline arrangement is as shown in the attached annexes. The compressed air produced in the

air compressor first enters the dryer, and then comes via four routes to the rear brake air reservoir, front brake air
reservoir, handbrake air reservoir and auxiliary air reservoir respectively. The compressed air in the rear brake air
reservoir and front brake air reservoir is transmitted via pipeline to the upper and lower chambers of the brake foot
valve respectively, from which the compressed air will be transmitted via pipeline to the rear relay valve and front
quick release valve when the brake pedal is stepped down. The rear relay valve will open the control air circuit to
enable the rear wheels to brake, while the front quick release valve will directly enable the front wheels to brake. After
the brake pedal is released, the passage of rear air reservoir and rear relay valve will be closed, and the relay valve will
disconnect the air line of rear brake and thereby release the rear brake. The passage between the front air reservoir
and the front quick release valve will be closed, and the quick release valve will disconnect the front braking air circuit
and the rear air braking chamber, and thereby release the front brake. The compressed air in the front and rear braking
air circuits will be rapidly released from the quick release valve and the relay valve. The compressed air in the
handbrake air reservoir will be transmitted to the hand brake and a differential relay valve to function on the rear brake
air reservoir, and now the whole braking system is fully released. When the hand brake disconnects the air circuit, the
car is in a full rear braking status. The air circuit of auxiliary air reservoir leads to the auxiliary air circuits such as
clutch booster, door pump, air horn, air bag, etc. respectively.

Generation of brake force

Under the function of an external force, the brake shoe will apply certain

brake friction force on the brake drum, which is the brake torque of the brake.
Under the function of the brake torque, the wheels will exert on the ground a
forward force while the ground will exert on the wheels a backward counterforce,
which is the brake force of the ground on the wheels. It is clear that the brake
force is dependent not only on the magnitude of the force on the brake shoe and
the coefficient of the friction between the brake shoe and the brake drum, but also
on the contact between the wheels and the ground. For example, if the wheels are
not on the ground, no matter how large the brake force may be, the braking of the

Golden Dragon XML6125CLE, Repair Manual

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