Retraction Tensioner
As with the seat belt tensioner, the role of the pyrotechnic retraction tensioner is to mini-
mize any looseness of the belt in the pelvis and shoulder areas in the event of impact.
The pyrotechnic retraction tensioner is located in the driver and front passenger automat-
ic seat belt tensioner. In the event of an impact of the appropriate accident severity, the
gas generator (6) is ignited and the piston (5) moves upwards. This moves the drive pin-
ion (2) which is connected to the gearwheel (1). The rotation of the gearwheel (1) turns
the disc (3) and the Seat belt retractor. This pulls the belt into the automatic seat belt ten-
sioner.
Adaptive Belt-load Limiter
The adaptive belt-load limiter in the
automatic seat belt tensioner reduces
the load on the chest of the occupant.
The seat belt tensioner, retraction tension-
er and belt-load limiter all work together.
Adaptive load limiting works in two stages. The kinetic energy is first dissipated by the
leaf spring (4) and the torsion shaft (5) in the automatic seat belt tensioners. Then the
gas generator (1) is ignited, which moves the piston (2).
The piston (2) then presses on the slider (3) which is shifted out of position and rotated
in a predefined movement. This pushes away a retaining ring and disconnects the leaf
spring (4).
In addition, the slider (3) wedges itself into the automatic seat belt tensioner housing and
the kinetic energy is dissipated via the torsion shaft (5) as the process continues. Thanks
to the optimum coordination of the airbag, the kinetic energy from the passenger is dissi-
pated more evenly over the duration of the impact. This results in low stress forces on the
passengers.
Index Explanation
1
Gas generator
2
Piston
3
Slider
4
Leaf spring
5
Torsion shaft
85
E88 Complete Vehicle
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