Automotive Engineering - August 2024 - 26

ZF's latest safety
advances open up,
tighten up and
DOUBLE
DOWN
Z
A prototype steering wheel with ZF
Lifetec's new top-deploy driver airbag.
ZF rethinks safety with new airbags,
belt tensioner.
by Sebastian Blanco
F knows that the steering wheel remains one of the most
relevant components in an automotive interior, because this
is where drivers have direct contact to the vehicle. As steering
wheels become adorned with more functions than some
drivers know what to do with, ZF put Marc Schledorn in charge of the
teams rethinking how the driver airbag could operate in a world with
ever-busier steering wheels.
The solution is a new type of steering wheel airbag that ZF Lifetec
(ZF's renamed Passive Safety Systems division) announced in June.
Instead of moving through a thermoplastic airbag cover mechanically
fixed in the center of the wheel, Schledorn told SAE Media, the new
design positions the airbag on the top side of the steering wheel and
then expands through the upper rim of the wheel when needed.
" The frontal opening of a conventional driver airbag has limitations
regarding design and material selection in the opening area, "
Schledorn said. " When those designs become more seamless, we
might see a need for new materials. For instance, instead of using
thermoplastic materials, [we might] use more polycarbonate materials.
That's why ZF Lifetec began development of an alternative driver
airbag concept. "
Schledorn, officially the senior manager of steering wheel systems
advanced development at ZF, said the new top-deploy airbag enables
a higher degree of design freedom and allows engineers to integrate
additional features into the steering wheel's front panel.
Meet the ACR8.S
In July, ZF Lifetec announced another new product designed to provide
engineers with even more design freedom in a vehicle's interior. A
variant of the fourth-generation ACR8 active belt tensioner, the new
ACR8.S can be integrated into a seat for a cleaner look. The integration
26 August 2024
allows the restraint to reposition the seat occupants to
be better protected in a possible crash and can tighten
the seat belt if needed.
Within milliseconds of when the ACR8.S gets information
from the vehicle's sensors that a crash will
happen, the system activates a pyrotechnic belt tensioner
to pull " the occupant's upper body back towards
the seat backrest in a fraction of a second. "
Then, during the crash, the seatbelt tensioner guides
the occupant towards the airbag. ZF Lifetec said this
tightening, like the airbag it's in sync with, is irreversible
and will only happen " in the event of a correspondingly
serious accident. "
The ACR8.S can also send tactile warnings through
the seat belt to let the driver know something, like that
they have to take over the steering wheel. This feature
requires the OEM to choose one of the nine different
modular setup combinations currently available for the
ACR8.S that includes both the webbing motion sensor
and the electric drive unit.
" In these situations, the belt system's pulses close
to the body are more efficient warning signals than
displays or LEDs and minimize the reaction time, "
Harald Lutz, head of development at ZF Lifetec, said
in a statement.
Another optional function in the ACR8.S, this one
for comfort, is a way to allow less tension in the seat
belt when it is in normal operation and the ability to
tighten slightly during " dynamic driving. "
Providing a less restrictive belt feel and opening up
space for designers to work are not the only driving
AUTOMOTIVE ENGINEERING
ZF LIFETEC
Automotive Engineering - August 2024

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