Frankfurt a.M./Friedrichshafen. Four-wheeled, lightweight electromobiles (LEM or quadricycles) are the trend for short distances in urban areas. With the goal of offering highly effective safety systems for occupants in these vehicles, ZF has participated in the EU project BEHICLE as a system partner for occupant safety. The abbreviation stands for BEst-in-class veHICLE – a claim which is made good by the speedy three-seater electric vehicles of the same name. ZF has played a major role in this project as safety specialists that developed and integrated an innovative four-point seat belt system and airbag systems into the vehicle. ZF also contributed to simulation and testing. As the first in its category, BEHICLE is designed to receive five stars according to Euro NCAP’s testing standards. Comparable vehicles of this class have received no more than two stars up to this point.
The most sought-after vehicles in the growth market of micromobility are city rovers in the category L7e, which provide a maximum of 15 kW and weigh a maximum of 400 kg unoccupied (and without batteries). The disadvantage of these ultra-light vehicles however, is that in terms of occupant safety, up until now Euro NCAP has not listed a production model that had earned more than two stars.
“Our goal to contribute to Vision Zero naturally also covers new vehicle concepts and solutions such as the BEHICLE. From the start of the project, we were able to incorporate our expertise in the area of occupant safety. The overall result is that the BEHICLE is designed to achieve the only five-star EURO NCAP assessment of a vehicle in this class,” says Dr. Michael Büchsner, vice president and general manager of ZF’s global Occupant Safety Systems division.
The design characteristics of the vehicle such as a central driver’s seat and having no B-pillars posed a major challenge for the occupant protection concept. ZF addressed this by developing innovative passive restraint systems: a special four-point seat belt as well as new curtain and side airbags.
Tailor-made to enhance safety
The four-point seat belt – designed as a top belt – can help to further enhance occupant protection in the event of a crash compared to conventional three-point systems. It is uniquely implemented in the BEHICLE: two retractors with integrated tensioners and load limiters are included in the rear roof area. For buckling up, the two locking tongues extend laterally in front of the driver’s head and are therefore within easy reach for retraction from the headliner. The respective seat belt buckles are located to the left and right of the driver’s seat and are easy to locate thanks to illuminated technology. The straps are also equipped with ZF’s production DLT (Dynamic Locking Tongue) technology whereby a small component in the belt tongue coordinates the restraining forces of the belt in the event of a crash in such a way that the chest and shoulder area of the occupants is under less strain than the pelvic area.
Additionally, ZF’s new, reinforced side airbags (SABs) help to meet the relevant crash test requirements. In contrast to conventional vehicles, the restraint systems had to be positioned in the aluminum door beam instead of the seat backrest. The SAB design also takes into account the fact that the central driver’s seat leaves more space between the driver and the door, and that the airbags no longer adjust lengthwise to the seat.
The company’s curtain airbags (CAB), which are positioned along the A- and C-pillars with external retaining straps, provide further efficient protection in the event of impact from the side.
The passive safety systems from ZF supplement design safety optimizations implemented by other BEHICLE project partners on the front structure, passenger cabin and doors.