Function

Example of basic function sequence for unlocking vehicle via the driver's door.
By turning the key to the left in the lock cylinder the electric switch in the actuator is switched over via a rod. This switch then supplies a positive voltage to the supply pump via its control line.

The supply pump starts up and produces pressure, which is led to all pneumatic elements via a system of lines. The diaphragms in the elements are pressed upwards, operating the locks via a rod and unlocks them.
The tank flap element unlocks the flap directly. At the same time the electrical switches of the actuators in the passenger door and the trunk lid are actuated likewise by the pneumatic part of the element and supply positive voltage to the supply pump in the same way as the mechanically operated switch in the actuator of the driver's door.
If the system reaches a pressure significantly greater than 450 mbar, the supply pump is switched off by the pressure switch.

If the pneumatic line system and the elements are now vented again via the supply pump, the system is depressurized and the unlocking procedure is completed.
The locking procedure is carried out similar to the unlocking procedure. However if the supply pump is energized with a negative control voltage, the direction of rotation of the pump motor is reversed and thus the vacuum required for locking is produced.






Function schematic


Pressurizing and depressurizing (vehicles up to approx. 12/93)
In order to make possible locking immediately after unlocking or vice versa, without increased energy expenditure, the pneumatic lines to the doors are pressurized or depressurized with two electrical switchover valves.
The two valves hold the lines open in rest position. When the supply pump starts up, these valves are earthed and lock the lines.
As soon as the supply pump switches off after locking or unlocking, the earth control to the valves is cancelled. The valves open and pressurize or depressurize the pneumatic lines.

Pressurizing and depressurizing (vehicles as of approx. 01/94)
The two pressurizing and depressurizing valves below the driver's and front passenger's seat are no longer used as of the introduction of the bipressure pumps with immobilization output. For the pressurizing and depressurizing function of the central locking, the supply pump runs briefly in the opposite direction after reaching the shut-off pressure. The pressure in the system is thus reduced. As a result the vehicle can be locked immediately after unlocking or vice versa without increased use of energy.

Emergency opening
In order to facilitate the release of occupants of a vehicle which has been locked from the inside, in the event of a severe accident, the vehicle unlocks automatically.
Unlocking takes place when an acceleration of more than 4g or a vehicle inclination of more than 26° occurs and the ignition key is in position "1 or 2".
To do this, the control unit for the roll-over bar controls the supply pump for the central locking, which initiates unlocking of the vehicle after a 5 second delay.