In autumn 2007 occupant safety in BMW cars is being optimised through the introduction of crash-activated headrests: All models in the BMW 6 and the BMW 5 Series, as well as the BMW X5 and BMW X3, now come as standard with these newly developed headrests significantly reducing the risk of cervical vertebra injury in the event of a collision from the rear. Masterminded by the car's safety electronics, these crash-activated headrests move up to 60 millimetres or 2.36" forward and up to 40 millimetres or 1.57" upward within fractions of a second in the event of a collision, reducing the gap between the headrests and the occupant's head before his head can be thrown back by the forces acting on the car. This enhances the stabilising safety function of the headrest and minimises the risk of injury or over-stretching the occupant's cervical vertebrae.
The cervical vertebra (CV) syndrome also referred to as the whiplash trauma is one of the most common types of injury in traffic accidents and is caused by sudden impacts from behind.
Highly painful in many cases, such a trauma may even result from a rear-end collision at low speeds in city traffic. To avoid collisions of this kind, BMW introduced two-stage brake lights back in 2003, the illuminated area of the brake lights becoming larger whenever the driver applies the brakes particularly hard, thus giving motorists following from behind an absolutely clear and informative signal, telling them to brake hard too. And now the new crash-activated headrests offer the occupant of a BMW additional protection in such a situation, whenever a collision can no longer be avoided.
From outside the crash-activated headrests can be clearly distinguished through their two-piece look formed by the headrest support and the impact plate together with its padding moving variably as required to the front. At the side, in turn, the padded section features a button for manual adjustment of headrest depth in the interest of enhanced driving comfort, enabling the user to vary the position of the padding within three different levels by up to 30 millimetres or 1.18". In a collision the impact plate together with the padding will instantaneously move forward by up to 60 millimetres or 2.36", reducing the gap between the headrest and the occupant's head. And at the same time the impact plate and padding will move up by up to 40 millimetres or 1.57".
A second variant of the crash-activated headrest has been developed for BMW's comfort seats, in this case featuring side supports stretching along the entire height of the headrest padding. This new version replaces the former active headrests on the comfort seats.
The interior of both types of crash-activated headrests comprises complex, spring-driven mechanical operating units activated by a pyro-actuator. As soon as the pyro-actuator ignites, it propels a release stick moving a release plate and setting two adjustment springs free. These springs, in turn, move the impact plate and the headrest padding both forward and upward.The pyro-actuator receives its ignition signal from the airbag control unit as soon as the sensors detect a relevant impact at the rear of the car, this system developed by BMW thus acting very quickly and efficiently in protecting the occupants from whiplash trauma.
The new crash-activated headrests enhance not only the stabilising and safety functions of the headrest, but also the level of comfort while motoring. Conventional headrests set to the right position are often perceived as too close to the occupant's head and therefore appear to limit his freedom of movement. The new crash-activated headrests, in turn, provide not only enhanced safety, but also an improved feeling of space, since they are not required to rest directly on the occupant's head while driving.
Once the safety mechanism in the crash-activated headrests has been actuated, an appropriate Check/Control message will appear in the instrument cluster, reminding the driver to go to a BMW workshop in order to renew the pyro-actuator in the release system.