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New airbag designs promise safer future with adaptable shapes
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01/02/2007
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TRW has released details of a non-rotating driver airbag module that allows the inflating cushion to be specifically designed and shaped to fit individual vehicle interiors, writes Roger Bishop. It will appear on a European vehicle platform.
It will appear on a European vehicle platform. At the same time, the company is known to be working on even more advanced systems including bi-volume designs that use internal tethers and adaptive vents to control airbag size and hardness.
The steering wheel system increases protection potential during different crash conditions, particularly for vehicles with extreme angled windshields and or A-pillars that are involved in oblique crashes.
In addition, having a stationary steering module allows interior designers to add more convenience and aesthetic features to the steering wheel system because multifunction switches and displays remain in the same location when the steering wheel is turned.
To uncouple the rotation of the steering wheel from the driver airbag module, TRW engineers have developed a system with a circumferential gear. It uses direct force transmission from the steering wheel spokes into the steering column. This is said to improve steering feel by reducing the resistance felt by the driver when the wheel is turned.
Citroën currently has non-rotating steering wheel bosses on the C4 and the recently launched Picasso minivan.
Core development work being undertaken at TRW includes adaptive airbag systems for single stage toroidal or tubular inflators with ‘time-steered switching’ of a volume increase with the opening of an additional vent by the release of an internal tether. Release is by an actuation bolt on the inflator or by a separate tether actuation unit.
Bag volume, vent hole size and switching strategy can all be optimised for specific vehicle applications. The system adapts the pressure of the bag to occupants of different sizes.
Another scheme involves the use of dual stage tubular inflators and internal tethers that control the actual size of the airbag. The tethers are fixed above the second stage of the inflator. If a smaller occupant is detected only the first stage is fired and the tether constrains the size of the bag as it inflates. If a larger occupant is detected, the second stage of the inflator melts through the tether to release a bigger bag size.
Both designs are still in development and currently being evaluated and tested.
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Author
Roger Bishop
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