Introduction:
In a rear-end collision, one is pressed into the seat and the head moves relative to the upper body in a very rapid motion backward and forward. The stretching of the neck muscles can lead to permanent injury; a whiplash. In such a collision, the active headrest provides protection by moving forward. The head of the occupant is supported, preventing excessive neck movement.
The following image shows the scenario with an active headrest (top) and without an active headrest (bottom).
Mechanical active headrest:
In a seat with a mechanical active headrest, a pressure plate is installed that is pushed backward by the body weight. A lever mechanism moves the headrest upward and forward. The movement of the headrest catches the person’s head and decelerates the movement.
Immediately after the collision, the pressure plate and the headrest automatically return to their original positions.
Electric active headrest:
In this system, the moving mechanism is integrated solely into the headrest. The headrest consists of two elements that are pushed apart during a collision by an electromagnetic actuator. The airbag control unit manages the actuator. After activation, springs between the two elements press the cushion towards the head and neck of the person. The headrest itself does not move during a collision. After activation, the headrest can often be reset using special tools and diagnostic equipment. In other cases, it is necessary to replace the actuator.
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