SSP 122 – Seat belt pretensioners for Volkswagen
By wearing the seat belt—which is now also required by law—the risk of injury to vehicle occupants in collisions has been significantly reduced.
The automatic seat belt makes it easier to adapt to occupants of different body sizes and allows freedom of movement while locking in the event of an impact.
The effectiveness of the seat belt is significantly increased by the belt pretensioner. The protective effect of this additional safety system is based on the fact that a belt that fits snugly against the body restrains occupants better in an accident than a loosely fitting belt.
The safety benefit of the belt pretensioner therefore lies in the fact that the occupant is involved in the vehicle’s deceleration at an earlier stage.
In the event of a frontal collision, the belt pretensioner eliminates all belt slack. “Slack” is the technical term for a loosely fitting seat belt webbing.
Specifically, this so-called belt slack includes:
The belt webbing payout until the locking mechanism of automatic seat belts engages
Tightening of the relatively loosely wound belt (reel effect)
The distance between the belt webbing and the body, including the effect of loosely fitting clothing
The system is designed to eliminate only the slack, without injuring the occupant or pulling them back into the seat.
In the event of a frontal collision with an obstacle at a speed exceeding 15 km/h, the seat belt is tightened within 24 milliseconds. As a result, a previously loose-fitting belt is optimally tightened against the body, largely preventing injuries caused by loose seat belts.
Whether the belt pretensioner system has been triggered can be identified after removing the B-pillar trim by the missing protective cap and the piston visible from above in the cylinder tube.
After deployment, the belt pretensioner system must be replaced.