B43.10-0003-09
1 Vacuum check valve
2 Cover
3 Output shaft
4 Diaphragm
5 Force piston
6 Air inlet
7 Input shaft
8 Vacuum vent
9 Reaction disc
Operation
A - Idle
The pedal is released.
The air inlet valve is closed.
The vacuum vent valve is open.
Currently, there is constant vacuum on the two sides of the diaphragm (4). If there is no difference in pressure, the set remains idle.
B - Applied
When the pedal is actuated, the input shaft (7) pushes the force piston(5). With the movement of the piston force (5), the vacuum communication is interrupted and the air vent (6) is opened. Thus, on one side, there is atmospheric pressure, and on the other, there is vacuum. The diaphragm (4) is forced to increase the strength in the output shaft (3).
C - Balance
The output shaft (3) pushes the piston of the master cylinder, causing an increase in its hydraulic pressure. This increased pressure generates, on the reaction disc (9), a force opposite to that applied by the pedal. At this moment, the reaction disk (9) is being compressed at its edges so that its center inflates. This causes the air inlet (6) to close. As the vacuum vent (8) is already closed, the system is in balance.
When balance is reached, there is, on the front side, near total vacuum. On the other side of the diaphragm (4) a little air came in while the vent was open. So, in this case, we have a lower atmospheric pressure. Thus, the pedal movement can control the pressure of one of the sides of the diaphragm (4) and, therefore control the braking.