The principle of operation of the vacuum assisting mechanism.
The principle of operation of the vacuum assisting mechanism, connected to the engine pickup. If the brake pedal is released, the inside of the cylinder is connected to the atmosphere, and the piston pressed down by a stop spring rests against the wall. When depressing the brake pedal, the lever system closes the valve that isolates the inside of the cylinder from the atmosphere and opens the valve at the same time, connecting the engine suction pipe to the inside of the cylinder. As the air is sucked out of the cylinder, a negative pressure is created in it 0,5-0,6 at and thanks to the pressure difference, the piston moves and is actuated via a lever (in the system of mechanical brakes) and rods brake mechanisms of the wheels or exerts additional force on the brake pedal lever. In the latter case, two forces act on the master cylinder piston: driver's legs and the assist mechanism.
When the brake pedal is released, the connection between the inside of the cylinder and the suction pipe is severed and the cylinder is open to the atmosphere.