How does a vacuum brake booster work

In this interesting animation, we see how a vacuum brake booster works, a fundamental component of the braking system in modern cars, whose main purpose is to reduce the effort needed to press the brake pedal. The vacuum brake booster uses the vacuum created in the intake manifold of the internal combustion engine; this vacuum is used to assist the force applied on the brake pedal.

The body of the vacuum brake booster is a cylinder, divided into two chambers by a diaphragm, which is a flexible membrane that moves in response to pressure changes. The control valve regulates the airflow between the two chambers and the push rod transmits the amplified force to the brake pump.

When the brake pedal is not pressed, both chambers of the vacuum brake booster are in communication with the intake manifold, so they are both under vacuum; when the brake pedal is pressed, the control valve closes the communication between one of the chambers and the intake manifold, opening it instead to the atmosphere, creating a pressure difference between the two chambers.

The pressure difference pushes the diaphragm and the push rod, amplifying the force on the pedal: the amplified force is transmitted to the brake pump, which in turn increases the pressure in the hydraulic brake circuit.