5.3.6. Front seat belt tensioner

In the F10, the familiar three-point seat belt is the belt system used on the front seats.

Fig 1: Identifying Seat Belt Tensioners, Airbag And Automatic Reel With Adaptive Force E Limiter

Courtesy of BMW OF NORTH AMERICA, INC.

Seat belt tensioners 

The task of the pyrotechnic belt tensioner is to minimize the seat belt slack in the pelvis and shoulder areas in the event of an impact, thereby improving the restraining action.

The belt tensioners are located on the driver's seat and front passenger seat. The belt tensioners are ignited in certain crash situations.

The seat belt buckle is connected by means of a steel cable to the piston in the tensioning tube. If the squib is triggered, gas pressure is created, which moves the piston in the tensioning tube At this, the seat belt buckle is pulled down by the cable and the seat belt is tensioned.

Fig 2: Belt Tensioner System Diagram

Courtesy of BMW OF NORTH AMERICA, INC.

Automatic reel with adaptive force limiter 

For the driver and front passenger, an automatic reel is installed as on F01/F02.

With the aid of a gas generator, there is a changeover from a high to a low power level during the impact, in order to reduce the belt restraining forces.

With optimal tuning in connection with the airbags, the kinetic energy of the occupant is more uniformly reduced over the duration of the impact. Thus lower occupant stress values are achieved.

The operating principle of the adaptive force limiters in the F10 are the same as on the F01.