Pressing the button on the C-pillar triggers the automatic closing of the rear door by the soft closure aid. Complete closure of the rear door is carried out by the soft-close automatic (SCA) function.
The door modules register the signals of the switches and sensors installed in the doors and control the drives installed in the doors. Information is received and sent via the K-CAN PERIPHERALS data bus.
The door contacts on the frames of the rear doors are used for the interior light function and the coach door lock as well as for the close function. In the case of the close function, the door contacts report statuses to the door modules in the rear doors: door closed = contact open; door open = contact closed. The door contacts are firmly wired to the door modules.
When the buttons on the C-pillar are pressed, the switch the door contacts used for the close function to ground. The buttons are wired to the door contacts in series.
The drives for automatic Soft Close are fitted in the system locks and they close the doors. The closing operation is performed by way of defined positions. When they reach the end position, the drives for automatic Soft Close are switched off automatically. The drives for automatic Soft Close are activated by the door module control modules in each of the door modules.
Two drives for the central locking system are integrated in each of the system locks. This enables the lock mechanism to be moved into the unlocked, locked and double-locked positions.
Two switches (Hall sensors) are also integrated in each of the system locks. The switches send status reports to the door modules. The rotary latch sensor reports: rotary latch completely opened (door opened) or closed (door closed). The unlocked sensor reports: lock unlocked. The locking pawl switch reports: lock has reached pre-lock position. The soft-close automatic standby switch reports: end position of the SCA drive in the rotary latch closed direction is reached.
The hydraulic drives in the rear doors consist of: the power stage for activation of an electric motor, electric motor to drive a hydraulic pump unit. The input of the power stage is wired to the door contact.
When the rear door is closed, the contact of the door contact used for the close function is opened. The button for closing the rear door is also opened. Operating the button is thus unable to trigger a function on the hydraulic pump unit.
When the rear door is open, the contact of the door contact used for the close function is closed. Pressing the button to close the rear door applies ground via the closed door contact to the power stage of the hydraulic pump unit. This means that the power stage activates the electric motor and the hydraulic pump unit is driven.
The hydraulic pump unit generates the pressure required to run a hydraulic cylinder. The rear door is closed slowly by means of the hydraulic cylinder.
When the rear door operates the door contact during the closing operation, the closed contact is opened. This interrupts the ground connection to the power stage of the hydraulic drive and the hydraulic pump unit is switched off.
At the same time, the rear door reaches the pre-lock position on the system lock. A Hall sensor reports the status change to the door module control module. Due to the status change, the soft-close automatic (SCA) function starts up and the rear door is fully closed and locked (see functional description SCA soft-close automatic, doors).
The pressure in the hydraulic system is set by an overflow valve. The pressure is selected in such a way that there is effective anti-trapping protection when closing and the door can be opened at any time without effort.