Front Belt Tension Limiters

Front Belt Tension Limiter

The belt tension limiters for the driver and passenger seat are inertia reel seatbelts with adaptive force limitation.







A gas generator is used to switch from a high degree of force to a lower degree of force. This also has to be possible during an accident to achieve a regressive force reduction. The advantage of the adaptive belt tension limiter is the considerable reduction of the load on the chest in the event of a crash.

With optimum coordination to the airbag, the kinetic energy of the occupant is reduced evenly across the duration of the crash, thus achieving low occupant load values.

Operation

The adaptive force limitation is based on a two-stage torsion bar (stage shaft). The torsion bar consists of the two head ends left and right, the stages and the center head. The belt force is transferred to the seatbelt roller. The seatbelt roller is connected to a sleeve that contains the torsion bar. There is a shaft ring with locking pawls on the sleeve. The locking pawls transfer the torque to the torsion bar.







In the first stage, with the preset high level of force, the torque of the seatbelt roller is transferred via the locking pawls to the center head of the torsion bar.

If the seatbelt roller is turned relative to the fixed torsion bar, the force is transferred to the thicker part of the torsion bar. This produces the high power level. This is the function of a normal emergency locking retractor.







In the event of a crash, the gas generator is ignited and a plunger moves out, shifting the shaft ring axially. The locking pawls are now no longer held by the sleeve and no longer transfer more torque to the center head of the torsion bar.

The belt force is now passed across the right-hand head end into the stage shaft and runs through the entire torsion bar, The lower diameter on the right-hand side means that the torsion bar is twisted further and thus the force is reduced to a lower level.

Seatbelt Upper Anchor Position




Using new simulation methods with regard to installation and ergonomics, it was determined that there is an optimal area for all occupants to locate the seatbelt upper anchor.

The anchor point is no longer adjusted automatically based on seat movement as the system on the previous model. In addition the fitting is now designed as a roller. The low friction power (drag) of the seatbelt increases wearing comfort.