Browse Publications Technical Papers 2004-01-0844
2004-03-08

Blow-Molded Plastic Active Knee Bolsters 2004-01-0844

Deployable or active knee bolsters are being introduced by many OEMs, primarily on the driver side, as an improvement to the fixed or passive knee bolsters. There are shortcomings with the fixed knee bolster and many of them can be overcome with a deployable knee bolster. Also the deployable knee bolster has a few other advantages that make it a critical restraint system component for reducing the occupant injury numbers in frontal impact crashes.
With the latest revision of FMVSS208, vehicle manufacturers must now demonstrate occupant performance for a wide range of test conditions. OEMs are now required to evaluate the 5th percentile female and the 50th percentile male in both belted and unbelted scenarios. A wide range of crash conditions must also be evaluated, including rigid barriers, angled impacts and offset deformable barriers. To achieve compliance to all of the test conditions, deployable knee bolsters are being considered for their added restraint system tuning capabilities.
Now that NHTSA is encouraging drivers to sit at least 10 inches away from the steering wheel center (airbag), the distance between the knees and the knee bolster will tend to increase. This increase in distance between the knees and the knee bolster may have a negative impact on the lower extremity injuries in the field. Adjustable pedals are also being added to vehicles and their inclusion will contribute to this negative effect. The deployable knee bolster can play an important role as an effective injury countermeasure in such occupant sitting trends.
Conventional plastic blow-molded knee bolsters1 provide an opportunity to be converted to deployable knee bolsters, very similar to the airbag concept. These blow-molded deployable knee bolsters provide a simple and cost effective alternative to the various fabric knee airbag designs currently being introduced by some OEMs.

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