Munich, 16. August 2007 – a rear-end collision can have painful consequences. Because if one’s own car is hit from behind, the occupants are threatened by the furrowed whiplash injury. It is caused by the sudden impact of energy from behind. In the process, the head is first thrown forward and then backward. Bmw now wants to take countermeasures. In fall 2007, a number of vehicles from munich will be fitted with newly developed crash-active head restraints. They will be offered as standard in the 6, 5, x5 and x3 model series.
Reduced distance to the head
The system is controlled by the vehicle’s safety electronics system. In the event of a collision, it moves the front part of the head rest forward by up to six centimeters and upward by up to four centimeters. This reduces the distance to the head even before it is thrown backwards. In this way, the risk of injury or overstretching in the cervical spine area of the vehicle occupants is reduced. If the headrest safety mechanism has been tripped, a message appears in the instrument cluster reminding that a workshop should be visited to replace the pyroactuator.
The crash-active headrest is easily recognizable by its two-part design. It consists of the support and the impact plate with padding that can be variably moved forward. In the side area, the upholstered part has a button for manual depth adjustment. This allows the position of the cushion to be varied by up to three centimeters in three locking positions. The comfort seats with electric adjustment, which are optional in most cars, already have active headrests. In the future, a second variant of the new development will be used here. It has side bolsters that extend over the entire height of the cushion.
Draw on airbag control unit
The inner workings of both versions of the crash-active head rests include a complex, spring-driven mechanism that is triggered by a pyroactuator. When the pyroactuator rounds, it drives a release pin, which in turn moves a release plate and releases two motion springs. These move the impact plate with the cushion forward and upward. The pyroactuator receives its ignition signal via the airbag control unit as soon as the sensors detect an impact from behind. Unlike bmw’s system, lexus’ advanced pre-crash system activates the head restraints when a crash is imminent. This is made possible by a microwave radar sensor at the rear, which can detect a likely accident in advance.