Active head restraints

Developed several years ago, they have now become part of the standard equipment of several vehicles.

The mechanism that activates them is purely mechanical, and its operation is very simple: in a nutshell, when we are hit from behind, due to the impact, it first tends to push against the back of the seat and in doing so, presses the lever. – installed inside the upholstery (see photo), which extends and raises the active head restraint by a few centimeters. In this way, whiplash can be avoided and therefore the risk of injury can be minimized.

Due to its mechanical principle of operation, this system is very useful in the event of subsequent rear-end collisions (see Rear collisions), since it can always work.

Unlike, for example, airbags, which once exploded, have exhausted their effectiveness.

CHOICE BMW

Many manufacturers have opted for a mechanical active head restraint, while BMW has gone the other way. Perhaps more efficient, but certainly more expensive… Below is the press release.

Controlled by the vehicle's safety electronics, the active head restraints move forward 60 mm and up 40 mm in fractions of a second in the event of a collision, reducing the distance between the head restraint and the passenger's head before the head is pushed back by forces acting on it. a car.

This increases the safety functions of the active head restraint and minimizes the risk of injury to the cervical vertebrae of vehicle occupants. Cervical vertebrae syndrome, often referred to as whiplash, is one of the most common back impact injuries.

Minor rear-end collision injuries in low-speed urban traffic are often a major concern. To avoid this type of collision, BMW introduced two-stage brake lights in 2003, the illuminated area of ​​the brake lights becomes larger when the driver applies a particularly constant force to the brakes, this ensures the following vehicles with a clear signal. , which leads to decisive braking. New active head restraints now offer BMW passengers extra protection when a collision cannot be avoided.

Safe, comfortable and adjustable

From the outside, active head restraints can be easily recognized by the modern two-piece head restraints, head restraint holder and impact plate (forward-adjustable) that integrates the cushion. On the side there is a button for manual adjustment of the depth of the headrest for increased driving comfort, which gives the user the ability to change the position of the cushion in 3 different levels up to 30 mm. In the event of a collision, the impact plate, together with the cushion, instantly moves forward by 60 mm, reducing the distance between the head restraint and the passenger's head. This raises the impact plate and pad by 40 mm.

For comfortable seating, BMW has developed a second version of the active head restraints, in which the side bolsters extend over the entire height of the head restraint cushion. This new version replaces the active head restraints of the current comfort seats.

Activated by the airbag control unit

Both active head restraints have a spring mechanism inside, which is activated by a pyrotechnic drive. When the pyrotechnic drives are ignited, they move the locking plate and release the two adjusting springs. These springs move the impact plate and pad forward and upward. The pyrotechnic actuators receive an activation signal from the electronic airbag control unit as soon as the sensors detect an impact in the rear of the vehicle. The system, developed by BMW, quickly and effectively protects passengers from whiplash injuries.

New active head restraints not only improve safety functions, but also improve driving comfort. Regular head restraints, when properly positioned, are often perceived too close to the head and appear to restrict movement. On the other hand, the new active head restraints not only improve safety, but also increase the sense of space as they do not have to touch the head while driving.

When the safety mechanism of the active head restraints is triggered, a corresponding Check Control message appears on the combined dashboard, reminding the driver to go to a BMW workshop to reset the system.