Renault's new airbag developments. Level one is shown on right while left shows level two.
Back seat frontal airbag.
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Renault seldom opens the doors of its Aubeyoye technical center near Rouen to journalists. But it recently agreed to lift the veil on some projects, and AEI was there to hear about them. One of the interesting safety projects under development is a two-stage airbag, expected to be fitted to premium-level cars next year and to reach small models like the Clio by 2004. Renault is also developing rear airbags.
Like some other major car manufacturers, Renault combines accidentology and biomechanical research to provide a database of how and why accidents occur and their outcome in terms of vehicle deformation and occupant injuries. It adds about 300 cases to that database each year. In 1998, Renault announced a system that involves programmed restraint with controlled airbag inflation. It is now taking the system further, with an adaptive airbag and safety belt, which it is claiming as a world first. The new technology is based around a variable-volume airbag combined with a safety belt equipped with two pretensioners. The airbag and the belt work together to impose and distribute the energy of retention upon the occupants according to the severity of the impact. What all this means is that Renault is planning to provide enhanced protection at speeds up to 65 km/h (40.4 mph) compared to 60 km/h (37.3 mph) at present "without creating parallel secondary effects in less severe impacts." It does this using a two-level airbag that can sense the severity of an impact in terms of speed and angle. A two-level pressure generator is used to inflate the airbag.
At 5 milliseconds after impact, the impact computer fires the first pre-tensioner, with the purpose of taking up all safety belt slack. During the first 10 milliseconds after impact, the system evaluates impact severity. If it is not categorized as Grade One, a small-volume airbag inflates (capacity 40 L (1.4 ft3)). However, for a Grade One impact, a second pretensioner fires after the first to restrain the occupant firmly against the seat, reducing leg and foot injuries. Simultaneously, the second airbag gas generator is ignited, inflating the airbag to maximum volume (60 L (2.12 ft3)). Initially, the two-stage airbag and pretensions are likely to appear in the new Renault Laguna, due in 2000.
Renault is also developing added protection for rear-seat passengers and is studying a new generation of back seat, frontal airbag whose principal feature is that it is built into the lap-strap of the safety belt. Unlike an inflatable diagonal belt, the lap strap configuration consists of "a true airbag." It is inflated via a gas generator positioned at floor level. This system allows the airbag to be perfectly positioned in front of the occupant, guaranteeing the same level of protection enjoyed by the front-seat occupants.
Aubeyoye has extensive facilities for testing such new systems. Established in 1982, it now has 35 km (21.7 mi.) of test tracks. There is a high-speed bowl for speeds up to some 200 km/h (125 mph), plus the usual representation of various road surfaces and a handling track. There is a wet-weather circuit and another simulates mountain roads. Extensive test laboratories are also in place at Aubeyoye, including two aerothermic wind tunnels. Aubeyoye complements Renault's other research and development centers: the Technocentre at Guyacourt responsible for the development of new models from concept to prototype production; the Rueil center focused on powertrain component engineering and manufacturing processes; and Lardy, where powertrain testing and crash tests are carried out.
Stuart Birch
