Belt Extender, Function - GF91.45-P-0001LF
Model 217
Block diagram
Function requirements, general
- No overvoltage or undervoltage
- Seat belt not fastened
- Backrest locked
- Door closed
- Front passenger seat occupied (not for initial run)
When a seat backrest is unlocked, the driver seat control unit and the front passenger seat control unit send a signal via the interior CAN to the rear control unit.
The supplemental restraint system control unit sends the status of the belt buckles and the front passenger seat occupancy via user interface CAN, electronic ignition lock control unit and interior CAN to the rear control unit.
The front door control units send the door status via interior CAN to the rear control unit.
Belt extender, general
The belt extender makes it easier to reach the front seat belt. To do so, the belt extender is automatically extended to the convenient position or this occurs when the belt extender button in the center instrument panel button group is pressed.
Extend/retract belt extender
After someone enters the vehicle (door opened and closed) and switches on circuit 15R, the seat belt extender is automatically extended to the convenient position. In addition, the seat belt extender can be manually extended to the convenient position with circuit 15R ON by pressing the seat belt extender button.
The seat occupied recognition is also taken into account on the passenger side. Because the signal of the seat occupancy recognition is only available for approx. t = 5 s after circuit 15R is switched on, only the status of the front passenger door is evaluated for the initial run.
The electronic ignition lock control unit transmits the status of circuit 15 via the interior CAN to the rear control unit. The center instrument panel button group sends the status of the belt extender button via the instrument panel LIN, front SAM control unit and interior CAN to the rear control unit.
The convenient position depends on the respective seat position. The driver seat control unit and the front passenger seat control unit send the seat position via interior CAN to the rear control unit. The rear control unit directly actuates the respective belt extender electric motor to extend or retract the belt extender. For position detection the seat belt extender Hall sensor is integrated in the seat belt extender electric motor. The rear control unit directly reads in the signals of the respective belt extender Hall sensor.
The belt extender is automatically retracted again under the following conditions:
- Door is opened
- Seat belt is fastened
- Circuit 15R is switched off
- Backrest is unlocked
- Front passenger seat is recognized as not occupied
- Convenient time lapsed
- Overload recognized
- Fault detected
The actuation voltage of the seat belt extender electric motor is reduced by 30 % 20 Hall impulses before reaching the respective end position in order to slow the seat belt extender down before it moves into the end position.
Initialization drive
If the position of the seat belt extender is lost (e.g. due to a hardware fault or external operation), an initialization run is performed. To do so, the belt extender is moved to the rear end position (determined by the blockage detection) and the location counter is set to the value "0".
Overload recognition
If a counterforce of approx. F = 100 N is recognized while extending the seat belt extender, the seat belt extender reverses back to the rear end position. After a dwell time of t = 1 s a renewed extension is requested. This process repeats itself three times.
| Electrical function schematic for belt extender | Model 217 as of model year 2018 | PE91.45-P-2050-97SEB | |
| Model 217 up to model year 2018 | PE91.45-P-2050-97SEA | ||
| Overview of system components for supplemental restraint system | GF91.60-P-9996LF |