Improved protection for rear passengers -
New milestone of technology: active seat-belt buckle
Stuttgart - Active seat-belt buckle is a
new innovation for the rear seats which is currently under development
by safety pioneer Mercedes-Benz and will shortly go into series
production in one of the Stuttgart manufacturer's luxury-segment models.
An electric motor extends and retracts the seat belt buckle
automatically. In this way, the belt slack in the area of the pelvis and
thorax can be reduced and passengers are secured more firmly in sideways
and lengthways directions. Active seat-belt buckle fits in with
Mercedes-Benz's integrated safety concept. In keeping with an
all-embracing approach to safety, this concept covers all phases of
automotive safety: from safety during driving through safety in
hazardous situations and protection in the event of an accident to
minimisation of the consequences of accidents.
The innovation is typically Mercedes-Benz,
improving safety and comfort in one. Fastening seat belts in the rear is
also made much simpler: the seat belt buckle emerges from the upholstery
when the rear doors are opened and is provided with an illuminated
insertion slot. Simplifying use of the seat belt in this manner may
increase the percentage of rear passengers who buckle up. The innovation
also makes it easier to assist children or people who require help in
fastening their seat belts.
Active seat-belt buckle is also integrated
in the PRE-SAFEŽ preventive safety system. This means that whenever
PRE-SAFEŽ becomes active in critical driving situations or when a
critical distance from other objects is detected, reversible belt
tensioning is also effected in the rear via the active seat-belt buckle
function. The restraint system and the passengers are thus better
prepared for a possible accident situation. Active seat-belt buckle
complements the pyrotechnic belt tensioning which has featured as
standard on all outer rear seats in Mercedes-Benz vehicles for many
years now. This pyrotechnic system is triggered in the event of actual
The Mercedes safety experts have developed
active seat-belt buckle using detailed computer models of the human
body, as dummies are only able to simulate the human pelvic system along
very rough lines.
Integration in the vehicle's PRE-SAFEŽ
Active seat-belt buckle is a moving belt
buckle which can be extended by 70 millimetres and retracted by 40
millimetres via an electric motor. The belt buckle is attached via a
cable to a spindle nut which runs on a spindle, translating the electric
motor's rotary movement into a linear movement.
The following functions are carried out by
means of this movement:
Seat belt reminder/easier fastening of
the seat belt: Active seat-belt buckle is provided with an
illuminated insertion slot, attracting the occupants' attention to
the buckle. Particularly in the dark, the belt buckle is easier to
find and to connect with the seat belt tongue. In addition, the belt
buckle is extended by 70 millimetres when occupants enter the rear
of the vehicle, to facilitate fastening of the seat belt. In
extended state the belt buckle is more readily accessible and it is
easier to insert the belt tongue. Both functions are activated when
the doors are opened by passengers entering the rear of the vehicle.
Minimised belt slack: after the belt
has been inserted, the belt buckle returns to its original position.
This reduces any belt slack in the area of the pelvis and thorax,
and the belt fits correctly in the pelvis area.
PRE-SAFEŽ function for rear occupants:
Active seat-belt buckle is fully integrated in the vehicle's
PRE-SAFEŽ system. Whenever PRE-SAFEŽ becomes active in critical
driving situations or when a critical distance from other objects is
detected, reversible belt tensioning is also effected in the rear
via the active seat-belt buckle function. The restraint system and
the passengers are thus better prepared for a possible accident
system. In contrast to its extended position to facilitate fastening
of the seat belt, the belt buckle is retracted by approx. 40
millimetres. This reversible function increases the belt tensioning
on the occupant by up to 80 millimetres. In addition, the belt
buckle branches off at a lower point at the occupant's hip. This
reduces the risk of the pelvis pushing through under the belt.
Securing the occupants more effectively in this way reduces the
stress to which they are exposed in the event of an accident. Active
seat-belt buckle is set to replace the pyrotechnic belt tensioning
which has featured as standard in Mercedes-Benz vehicles for many
years now. This pyrotechnic system is triggered in the event of
POST-SAFE functionality: to facilitate
the rescue of occupants and to assist rescue personnel or the
occupants themselves in unbuckling the seat belts, the belt buckle
is extended once again as soon as the doors are opened by rescue
personnel or the occupants themselves after the system has detected
a crash and verified that the vehicle is stationary, provided that
the on-board electrical system is intact. The raised belt buckle
position allows better access from inside the vehicle, while
illumination of the buckle draws attention to the belt's opening
In keeping with Mercedes-Benz's integral
safety concept, active seat-belt buckle covers all four areas of
automotive safety – "Safe driving", "In the
event of danger", "In an accident" and "After an accident".
The Mercedes-Benz safety experts have
developed active seat-belt buckle with the aid of virtual human models,
which provide a clearer picture of what happens to a vehicle's occupants
in an accident than crash-test dummies. These digital models simulate
not only the human body's outer form, but also its internal structures,
such as bones and soft tissue.
"All the crucial biological features of
humans – joints, muscles, tendons, ligaments, bones – can only be
simulated in very rough terms with dummies," explains Dr Hakan Ipek,
expert for virtual human models at Mercedes-Benz. "Some seated
positions, such as when a rear passenger is dozing and the belt does not
pass over the pelvis in the correct manner, simply cannot be recreated
with a dummy," he adds by way of example.
With virtual human models, the
biomechanical characteristics of the human body are simulated in detail
on a computer, enabling examination of the stress to which the model is
exposed in a virtual crash test.