The brake booster pump uses the principle of inhaling air when the engine is working, resulting in a vacuum on one side of the booster, creating a pressure difference relative to the normal air pressure on the other side, and using this pressure difference to strengthen the brake thrust. Even if there is only a small pressure difference between the two sides of the diaphragm, due to the large area of the diaphragm, a large thrust can still be generated to push the diaphragm to the end with a lower pressure.
In the working state, the push rod return spring makes the brake pedal in the initial position. At this time, the one-way valve at the connection position of the vacuum tube and the vacuum booster is in an open state. Inside the booster, the diaphragm divides it into vacuum. The two gas chambers can communicate with each other, and they are isolated from the outside most of the time. The gas chamber can be connected to the atmosphere by having two valve devices.
When the engine is running, step on the brake pedal. Under the action of the push rod, the vacuum valve is closed, and at the same time, the air valve at the other end of the push rod is opened. After the air enters (the reason for the panting sound when the brake pedal is pressed ) Will cause the air pressure in the cavity to be unbalanced. Under the action of negative pressure, the diaphragm is pulled to one end of the master cylinder, which in turn drives the push rod of the master cylinder, which further amplifies the strength of the legs. Function.