Vacuum booster is a component that uses vacuum (negative pressure) to increase the driver’s force on the pedal. The vacuum booster is generally located between the brake pedal and the brake master cylinder. For ease of installation, it is usually combined with the master cylinder into a component, and a part of the master cylinder penetrates into the vacuum booster housing.
When braking, the brake pedal is depressed, and the control force from the pedal mechanism pushes the control valve push rod and the control valve plunger forward. After eliminating the gap between the plunger and the rubber reaction disk, it continues to push the brake master. The cylinder push rod, the brake fluid in the master cylinder flows into the brake wheel cylinder at a certain pressure, and this force is given by the brake pedal mechanism. At the same time, under the action of the valve spring, the vacuum valve also moves forward until it presses against the valve seat of the diaphragm seat, so that the channels A and B are isolated, that is, the front and rear chambers of the servo air chamber. Insulation, the air valve leaves the vacuum valve and opens, and the air is filled into the back chamber of the servo air chamber through the filter ring, felt filter ring, the opening of the air valve and the channel B. With the filling of air, a pressure difference occurs on the two sides of the diaphragm of the servo air chamber and a thrust is generated. This thrust pushes the brake master cylinder push rod forward through the diaphragm seat and the rubber reaction disk. This force is caused by the pressure difference. give. At this time, the acting force on the brake master cylinder push rod is the sum of the pedal force and the servo air chamber reaction disc thrust force, which makes the pressure output by the brake master cylinder multiply.
When the brake is released, the control valve push rod spring moves the control valve push rod and the air valve to the right, and the vacuum valve leaves the valve seat on the diaphragm seat and opens. The front and back chambers of the servo air chamber are in communication, and both are in a vacuum state. The diaphragm seat and the diaphragm are returned under the action of the diaphragm return spring, and the brake master cylinder releases the braking effect.
If the vacuum booster fails or there is no vacuum in the vacuum pipeline, the control valve push rod will directly push the diaphragm seat and the brake master cylinder push rod to move through the air valve, so that the brake master cylinder generates braking pressure, but acts on the pedal The force should increase.