Through testing, both virtual and actual, Delphi Corp. (Troy, MI; www.delphi.com) engineers have discovered that combining an energy absorbing steering column, collapsible knee bolster and an energy absorbing pedal structure into a single unit lets them: (1) improve occupant kinematics in a crash to the extent they can significantly reduce lower extremity injuries, and (2) reduce vehicle assembly time while improving quality.
Delphi claims its Driver Protection Module (DPM) can reduce serious injuries—especially those to the lower extremities—by as much as 27% which, in some instances, may allow OEMs to use a less-aggressive airbag deployment protocol. Reducing non-fatal injuries is the next step in safety systems, says Prof. Patrick Atkinson of Kettering University. An engineer, accident expert and advisor to Delphi, Atkinson believes the current focus on reducing vehicle crash fatalities alone is shortsighted. "Safety standards have rightly concentrated on reducing fatal injuries," he says. "However, lower extremity injuries often lead to debilitating injuries that can destroy a person's quality of life. Therefore, we should do what we can to mitigate these injuries." The DPM arose out of his research.
The module is made up of steel tubes and connected together via aluminum extrusions. These combine the separate units—steering column, knee bolster, pedals—into a single structure that eliminates separate steering column mount and knee bolster brackets, and installs as a single precisely dimensioned unit in less time. According to Jason Ridgeway, Delphi product engineer, New Product Development, “The steering column moves in the same path as the driver, which increases its ability to absorb energy from the torso, the pedals move away in a controlled manner to reduce foot injuries, and the knee bolster’s path aligns with the trajectory of the driver’s knees.” This also adds interior room because the bolster doesn’t need the padded “hump” currently required by non-active designs to control knee displacement in a frontal crash.
In an accident, the unit allows the steering column to move horizontally up to 100 mm, and the knee bolster to recede as much as 80 mm. If required, both can be fitted with small pyrotechnic pins that alter their resistance to movement. When the pins are extracted, the deformable restraining straps on the steering column and knee bolster follow a shallower “S-curve” that lessens their resistance. “This technology lets you tune for the vehicle environment, including the size and belt use status of the driver,” says Ridgway.
Delphi’s greatest concern regarding the DPM isn’t its safety, it’s how the purchasing departments at OEMs will view it. “Because this safety system combines the steering column, knee bolster, and pedals into an integrated safety system,” says Dan Crishon, Business Line Executive for Steering Columns and Intermediate Shafts, “it cuts across the functional silos around which most OEM purchasing departments are organized. Getting them to view this as a single drop-in unit could be a challenge.” Potentially working to Delphi’s advantage is the fact that this module can be used with only minor modification across platforms, and that a reduced-cost variant is under development.