All about Brake Booster

Introduction

We have previously discussed brakes and their importance. Related to which we also discussed how the Anti-Lock Braking System ( ABS ) works.

Today we shall be discussing the Brake Booster that also happens to be an important mechanical component of any braking system.

What is a Brake Booster??

Brake Booster is a mechanical component that is usually situated between the Master Cylinder/Tandem Master Cylinder and the Brake pedal.

The Brake Booster uses the Vaccum created by the engine by connecting the Brake Booster with the Intake Manifold or a pump and multiplies the braking effort initiated by the driver via the brake pedal.

Why do we need a Brake Booster??

When a driver applies the brake, the force initiated by the driver to the Master Cylinder/Tandem Master Cylinder is not enough to retard the vehicle due to its inertia. Hence, we need a mechanical component that multiplies the driver’s effort and assists in efficient Braking.

Countries like India are a highly populated country and while riding on the roads one has to continuously apply the brakes.

Since the force requires braking to push master cylinder without the brake boosters is very high so it causes fatigue, so we need brake booster as a helping hand for the actuation processes.

Brake Boosters also have an advantage of prevention as it reduces the chances of brake failure and also helps efficient braking during panic situations.

Heavy vehicles like Buses, trucks, etc, are heavyweight and have high inertia and so requires a huge amount of force to stop them that could only be achieved by brake boosters.

Components of a Brake Booster

• Booster Shafts
• Valves
• Springs
• Diaphragm
• Body

Booster Shafts

There are 2 shafts namely Primary Shaft and Secondary Shafts, that links Brake Pedals, the Diaphragm and the Master Cylinder

Primary Shafts

This Shaft is responsible for the mechanical linkage between the Brake Pedals and the Diaphragm and functions to transmit the force from the pedal to the diaphragm for further force multiplication.

Secondary Shaft

This shaft is responsible for the mechanical linkage between the Diaphragm and the Master Cylinder and functions to transmit the force from the Diaphragm to actuate the master cylinder for the braking.

Valves

The Brake Booster works on the principle of air pressure where both atmospheric pressures are in action as well as the vacuum, so requires 2 valves namely Atmospheric Valve and Vaccum/One-way Valve.

Atmospheric Valve/Poppet Valve

This valve is situated at the brake pedal side of the brake booster and functions to control the entry and the exit of the atmospheric air into the brake pedal.

This valve is situated on the master cylinder side of the Brake Booster and functions to regulate the vacuum inside the Brake Booster.

Springs

There are 2 springs namely Primary and Secondary.

Primary Spring

This Spring is situated on the pedal side that allows the primary shaft to compress and de-compress for the proper functioning.

Secondary Shaft

This spring is situated to the Master Cylinder side of the Brake Booster that functions to compress and de-compress the secondary shaft for proper braking.

Diaphragm

The Diaphragm is situated inside the body at the center and is a circular disc that separates the atmospheric pressure side and the vacuum side and as the pressure at the atmospheric side is always greater so pushes the secondary shaft connecting the master cylinder for braking.

Body

It is the outer casing to the Diaphragm and prevents any foreign substance to enter, so an efficient system is maintained throughout.

Working of Brake Booster

The working of brake booster is a function of vacuum and air that helps the booster to multiply brake pedal force before sending it to master cylinder let’s just see how does it happen-

Actuation Process

When the driver presses the brake, the primary shaft attached to the brake pedal moves towards the brake booster.

Due to which the atmospheric valve opens up that allows the fresh air to enter inside the air side of the brake booster.

This air entering assists the primary shaft to push the diaphragm placed centrally inside the brake booster’s body due to the pressure difference created between the airside and vacuum side of the brake booster.

Also, the vacuum valve at the vacuum side of the brake booster constantly maintains the vacuum inside the vacuum side of the booster as it is attached to the intake manifold which assists the brake booster in maintaining the vacuum during the suction stroke.

This vacuum or negative pressure created assists the diaphragm to move that in turn multiplies the force applied by the driver.

This movement of the diaphragm allows the secondary shaft moves towards the master cylinder side that in turn pushes the master cylinder’s piston and finally braking occurs.

Releasing Process

After the braking when the driver reverts his leg off the brake pedal i.e. releasing the pedal the secondary spring attached to the secondary shaft in the vacuum side pushes the diaphragm away.

Due to this movement of the diaphragm the vacuum valve opens and pushes the left out the air inside the vacuum chamber maintaining the vacuum levels inside the booster.

Due to this movement of the diaphragm, the primary spring attached to the primary shaft also pushes the primary shaft which in turn closes the atmospheric valve.

After the complete movement of primary shaft diaphragm, spring, valves, shafts, and pedal all the components of the brake booster return to their initial place, and finally, the releasing of brakes takes place.

Conclusion

Thus, Brake Boosters could be classified as life saviors at all times and plays a vital role in the braking system.

Originally published at https://www.carengineered.com on July 17, 2020.