In a rear-end collision, the occupants are accelerated along with the vehicle. The upper torso and pelvis of the occupants rest against the backrest and thus absorb this acceleration at an early stage. In this case, the head is the most unresponsive part of the occupants. In the initial phase of the crash, the head remains in its initial position. Viewed in relation to the body, which moves forwards, the head moves backwards.
The pitching motion of the head leads to cervical vertebrae injuries. The danger of cervical vertebrae injuries is higher the greater the distance between the head and headrest in the initial phase of a crash.
It is only when the head makes contact with the headrest that this relative movement between head and body is limited and the head is accelerated to the same extent as the body.
Electrically extendable rear headrests are fitted in the if electrical seats are fitted as special equipment in the rear.
Electrically extendable headrests are set in such as way that the gap between the head and headrest is very small. The small gap means the head is supported in a crash at an early stage and ”whiplash” of the cervical vertebrae is prevented. This can prevent the 'whiplash' syndrome (painful stretching of the neck muscles, tendons and nerves).
The rear electrical headrests are activated from the relevant seat module.
Extending the headrests:The headrests are extended with terminal R On.
Retracting the headrests:They are returned to their home position with terminal R Off.
The activation of the headrest motors is time-controlled. The time can be coded. At vehicle voltage less than 8.5 V, the headrest motors. are not activated. However, the request remains. It is carried out when the vehicle voltage rises above 9 V.
Fault messages: the motor control sends a fault signal in the case of overload and interruption.
The following control modules are involved in the message transmission for the headrest function:
All work on the priming caps of the active headrests and on the electric motors of the rear seat headrests must only be conducted with the battery disconnected.