Ford’s 2011 Explorer will debut next year with the industry’s first production inflatable seatbelts. The belt technology, co-developed with supplier Key Safety Systems, is designed to provide additional protection for rear-seat occupants.
Ford plans to eventually apply the new safety-belt technology across its global product portfolio, said Paul Mascarenas, Vice President of Global Product Development.
The inflatable rear seatbelts deploy in less than 14 ms, and spread crash forces over five times greater body area than conventional seatbelts. This helps reduce pressure on the torso while helping to control head and neck motion.
Ford’s market research showed that more than 90% of participants felt that the inflatable belts are more comfortable than traditional belts—a factor which could help increase rear belt usage. Ford research showed that only 62% of rear-seat passengers in the U.S. use their seatbelts vs. approximately 82% of front-seat occupants.
The new Explorer is based on a unibody architecture, a first for the nameplate. Ford planners selected the new SUV for its inflatable-belt system because it will be a “mainstream” product aimed at families, said Sue Cischke, Group Vice President, Sustainability, Environment, and Safety Engineering. She also noted it was easier to engineer into a new structure.
She explained that the system is aimed at reducing injuries to children, who often occupy the rear seats and who, along with elderly passengers, are more susceptible to crash injuries. The system is compatible with child seats and is designed to accommodate children sleeping with their heads slumped down, Cischke added.
The system hardware is impressively simple and appears very robust. The inflator cylinder developed by Key Safety Systems couples into the belt buckle; both were designed as a unit that when coupled together resemble a large bronchial inhaler. These components are mounted horizontally below the seats.
The chest belt contains the small sausage-shaped airbag constructed of 370-denier nylon. The bag is folded accordion-style inside a pocket woven into the chest belt.
Ford engineers, who have been developing the inflatable-belt concept since 2001, also experimented with locating the components in the C-pillar and in the cargo area, said Srini Sundararajan, Ford’s Advanced Engineering Manager of Passive Safety Research and the program’s technical lead.
The gas used is a mixture of argon and helium, pressurized at 4000 to 6000 psi (276 to 414 bar), noted Sundararajan. The use of cold, compressed gas instead of a heat-generating chemical reaction (used in traditional airbag systems) helps maintain the inflated belts’ temperature closer to ambient.
In the event of a frontal or side crash, the inflatable belt’s increased diameter more effectively retains the occupant in the most protective seating position, said Sundararajan. When inflated, the folded bag bursts through the belt fabric as it fills with gas, expanding sideways across the occupant’s torso.
The inflatable belts fill at a slower rate and lower pressure than traditional airbags, because the device already resides across the occupant’s torso—it does not need to close a gap between the belt and the occupant, as do the other airbags in the vehicle.
Tests show the system provides some pretension, but it does not require pretensioners to operate as designed. Cischke said pretensioners can be added depending on vehicle application. During development of the inflatable-belt system, Ford safety engineers also investigated various sophisticated belt-pretensioning systems as alternatives, according to engineers at other safety-systems Tier 1 suppliers, before selecting the new system.
Ford and Key Safety Systems share the patents. Ford and the supplier are negotiating when the system will be made available to other OEMs.