Vacuum Servo assisted braking - reducing the effort required to press the brake pedal

Administrator posted this 14 March 2019

It is very important to feel comfortable during driving a car, especially for people who spend most of the day at the wheel. Many factors can affect driver fatigue and even the braking system. Several years ago, the driver had to rise from the place leaning on the pedal with all the weight, which, of course, could not but irritate. In order to facilitate the operation of the brake system and reduce the load when braking in the car, there is such detail as a vacuum servo assisted braking (VSAB) or simple vacuum booster.

The Purpose of the VSAB

Firstly, it is an increase in the effort with which the driver presses the brake pedal. Secondly, ensuring more efficient operation of the brake system during emergency braking.

The design of the Vacuum Booster contains 17 spare parts, but we will highlight only a few of the most important)

  • Housing (body frame)
  • Brake master cylinder (further. BMC) or main braking cylinder
  • Membrane
  • Diaphragm (divides the body into cameras)
  • Push rod (provides the connection between the brake pedal and the follow-up valve)
  • Follow-up valve (provides a connection between chambers and/or external environment)
  • The piston rod of BMC (moves under the pressure of the diaphragm)
  • Membrane return spring or brake pedal return spring (responsible for the movement of the membrane during braking and movement of the car)

Thankfully to this design, the body is divided into two chambers, atmospheric (closer to the brake pedal) and vacuum opposite to the first. The pressure in both chambers is polar to each other, high and low respectively.

The Principle of Operation of the Vacuum Servo Assisted Braking

It is important to note that the vacuum chamber is combined with a gasoline engine, but in the case of diesel cars, a special vacuum pump is necessarily installed between the two devices (it can be found on gasoline cars).

During the movement of the car in the atmospheric and vacuum chamber is maintained discharged environment (overpressure). As a result, when you press the brake, the valve closes the connection between the chambers, leaving access only to the atmospheric chamber. This system allows the brake system to operate with high efficiency. It is the pressure in the atmospheric chamber that allows increasing the braking force.

Faults of the VSAB

Breakdowns of the vacuum brake booster are possible but rare. Moreover, the signs that the driver can feel at the same time, can be caused by the output of completely different automotive systems out of order. For example: reduced braking efficiency, idling of the engine and tight pressing of the brake pedal.