The vacuum booster is installed between the brake pedal push rod and the brake master cylinder, and its function is to provide power for vehicle braking. When the booster is not braked, the diaphragm in the booster is suspended in the vacuum, which is balanced by the vacuum of cavities A and B and the return spring.
True air booster is a component that adds the force applied by the driver to the pedal through true air.
Most true empty boosters are located between the brake pedal and the brake master cylinder. In order to facilitate installation, it is usually combined with the master cylinder as a component, and a part of the master cylinder penetrates into the housing of the vacuum booster.
When the driver depresses the brake pedal, the brake pedal lever pushes the plunger to move to the left, and the air valve also moves to the left under the thrust of the spring, so that the channels of cavities A and B of the diaphragm are closed and the air valve is opened.
At this time, cavity a on the left side of the diaphragm is still vacuum, and cavity B on the right side of the diaphragm is vented to the atmosphere, resulting in a pressure difference on both sides of the diaphragm, forcing the diaphragm piston to move leftward, and exerting increased force on the brake master cylinder piston through the push rod, which is helpful to the driver.
When the brake is released, the brake pedal force disappears, the return spring presses the diaphragm back to the equilibrium position, and the control lever moves to the right. At this time, the air valve is closed, the vacuum valve is opened, the cavities A and B are connected, and there is similar vacuum on both sides of the diaphragm.