32
Occupant safety
Rack-type seat belt tensioner
In the new Transporter, a rack-type seat belt ten-
sioner is installed on the driver and front passen-
ger side instead of the familiar ball-type belt
tensioner.
Task
The belt tensioners make the seatbelts taut
against the wearer's body in a front collision and
keep the body pressed against the backrest. In
this way, the slack between belt and body is
reduced on impact.
Function
The signal from the airbag control unit ignites the
detonator of the propellant. The plunger is con-
nected to the rack. The build-up of pressure
forces the plunger upwards. The rack turns the
sprockets 1 and 2 on the pinion.
Sprocket 2 is fixed to the outer ring of the torsion
shaft freewheel. If the outer ring now turns, the
rollers are pushed inwards until force has built
up between the outer ring and the torsion shaft.
The rotary movement is now transferred to the
torsion shaft and the belt is drawn in.
Belt tension is complete when the plunger with
rack has reached the damping element.
Rest position
End of triggering
310_062a
Rollers in basic
position
Position of rollers when
outer ring/torsion shaft
are affected by force
Damping element
Sprocket 1
Pinion
Sprocket 2
Roller
Torsion shaft
Plunger with rack
Gas generator
Outer ring of
freewheel
310_093
310_062
