Tech Briefs
SUV rollover protection

The system's headliner-concealed side-curtain airbags extend from the A-pillar back to the pillar behind the rear door.

During the 2001 model year, Ford Motor Co. will offer optional new rollover sensors and inflatable side curtains on its sport utility vehicles (SUVs). "Ford scientists and engineers have looked at the most threatening current driving conditions and developed new technologies to improve the protection of our SUV drivers and their families," said Helen Petrauskas, Vice President, Environmental and Safety Engineering.

The new system features headliner-concealed side-curtain airbags that extend from the A-pillar back to the pillar behind the rear door, sensors that measure the amount of horizontal vehicle "roll" or tilt, and tethers to keep the bags in place after inflation. The roll information is processed by a central control module that can trigger necessary rollover curtain bags in as little as 130 ms.

Most airbags depend on thermal expansion for volume. But when the gas within the bag is extremely hot, as it is with conventional pyrotechnic inflators, the bag loses volume rapidly as the gas cools and air escapes through the bag.

"With Ford's use of proprietary cool-gas inflators and low-porous bag materials, the gas is cooler, so there's less 'shrink' as heat is lost, and the airbags are much less porous, so they retain their volume longer," said Petrauskas. "They are designed to remain inflated for up to 6 s—approximately the time it takes an average vehicle to roll over a few times."

The side-curtain airbags help to protect passengers in both the front- and second-row seats. The new airbags will have fixed attachment points at the front and rear ends of the curtain to help prevent occupants from being thrown out of the vehicle during rollovers. The system also will help reduce the risk of head injuries for SUV occupants involved in side impacts.

An onboard computer protects against accidental deployment by instantaneously comparing tilt angle and rate-of-roll, determining whether a vehicle is going to recover, or whether a roll is inevitable. According to Petrauskas, "If the vehicle is going to roll, the system not only deploys, but also matches deployment speed to the event. A high-speed curb launch will trigger a faster deployment than a corkscrew roll on an embankment."

Approximately half of all SUV fatalities involve rollover, and these deaths often involve occupants being ejected from the vehicle. In fact, occupants thrown from the vehicle are up to 10 times more likely to be killed or seriously hurt than occupants who remain inside.

"Safety belt use is the most important factor in preventing these tragic circumstances, and occupants are best protected in SUV rollovers when they buckle up," Petrauskas explained. "However, our new inflatable curtain system will help protect occupants even when they don't use available restraints."

Jean L. Broge