1. Initial Status
The internal components of the HPU include 3 Normally Open (NO) valves, 2 Normally Close (NC) valves and a motor pump. The NO VALVE 3 is connected to the Simulator Chamber of the Brake Actuation Unit and it is opened when the brake is not engaged and closed when the brake is engaged.
The NO VALVE 1 and 2 are mounted between the boosting chamber and the reservoir tank of the brake actuation unit. When they are opened, the pressure in the boosting chamber is reduced.
The NC VALVE 1 and 2 are mounted between the high pressure generating motor pump and the boosting chamber. The pressure generated by the motor pump is cut off from the boosting chamber when closed and is fed to the boosting chamber when opened.
| AHB System | NO VALVE 1 | NO VALVE 2 | NO VALVE 3 | NC VALVE 1 | NC VALVE 2 | Motor |
|---|---|---|---|---|---|---|
| Mode | OFF(opened) | OFF(opened) | OFF(opened) | OFF(closed) | OFF(closed) | OFF |