ZF’s Latest Safety Advances Open Up, Tighten up and Double Down

July 22, 2024

Sebastian Blanco

ZF 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 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 factors for some of ZF Lifetec’s new safety announcements. Future automated vehicle provide their own challenges, which is where ZF’s new dual contour airbag comes in.

Meet the dual-contour airbag

This airbag can deploy in one of two volumes, depending on the seat position of the seat occupant (it works on the passenger or driver side). In case of a crash, a dual-stage inflator engages one or both parts of an airbag that can thus cover the additional distance between the driver in a reclined position and the steering wheel, up to between 150 and 200 mm (6-8 in). Schledorn told SAE Media the dual contour airbag could be up to 190 liters (7 cu ft), compared to the average driver-side airbag today of around 60 liters (2 cu ft).

Looking further ahead, ZF Lifetec spokesperson Knut Zimmer told SAE Media that while the Euro NCAP 2030 safety roadmap includes “Testing and assessment of assisted and automated driver support systems,” it does not include requirements for future AV possibilities like fully rotating chairs. Still, Schledorn said ZF is already starting to play in this arena.

“Look far into the future, at what’s happening in, I don’t know, 2040 or whatever,” he said. “We need to start to think about how to design airbag solutions for that. I know that we have some ideas on what to do when drivers are sitting in new positions, in rotated seats or whatever, but we need alternative approaches.”

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