Belt retractor, belt tensioner, belt tension limiter
The seat belts in the vehicle are part of the vehicle safety concept (→ Airbag system, Description)
(→ Advanced airbag system, Description) and include the following important functions:
Belt retractor
Every seat belt is equipped with an automatic belt retractor on the shoulder part of the belt. Full
freedom of movement is ensured when the shoulder belt is pulled slowly or when the vehicle is
travelling at normal speeds. However, if the belt is pulled out quickly or during sudden braking,
during travel in mountains or bends and during acceleration, the belt retractor blocks the seat
belt.
Fastened seat belts on the front seats may be tensioned automatically by the proactive occupant
protection system in critical situations, for example during an emergency stop or in the event of
oversteering or understeering. Both seat belts are slackened again if the accident does not
happen, or when the critical situation has passed. The proactive occupant protection system is
ready to be triggered again (→ Proactive occupant protection system, Description).
Belt tensioners
The seat belts for the front seat occupants are equipped with belt tensioners.
The belt tensioners are activated by sensors during severe frontal, side and rear collisions. They
tighten the seat belts against the direction in which they are pulled. Any slack in the seat belt is
retracted, which can reduce the forward movement of the vehicle occupants and their
movement in the direction of the impact. The belt tensioner works together with the airbag
system. If the vehicle rolls over, the belt tensioners will not be activated if the side airbags are
not triggered.
A fine dust may be produced when the airbags are triggered. This is quite normal and does not
mean that there is a fire in the vehicle.
Reversible belt tensioning (proactive occupant protection system)
Reversible belt tensioning may trigger in certain driving situations (→ Proactive occupant
protection system, Description). Examples include:
—Strong braking.
—Oversteer or understeer.
—Minor collisions.
Belt tension limiter
The belt tension limiter reduces the pressure exerted by the seat belt on the body during an
accident.
All safety requirements must be observed when the vehicle or components of the
system are scrapped. Qualified workshops are familiar with these requirements (→ Belt
tensioner, General safety).
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