DI8819 DI8818
WIRING
Airbags and seat belt pretensioners
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3) FRONTAL IMPACT AGAINST A FLEXIBLE
OBSTACLE
The airbag trigger speed depends in this case on
the degree of flexibility of the bodywork of the
vehicle hit.
The more flexible the other vehicle, the higher the
trigger speed (for vehicles of equal flexibility and
100 % contact, the speed is higher than 40 km/h)
(relative speed).
4) OFFSET IMPACT AGAINST A FLEXIBLE
OBSTACLE
Here the airbag trigger speed depends on the an-
gle of impact α and the flexibility of the vehicle hit
in the direction of travel.
The vehicle speed for airbag triggering is greater
when the angle of impact α is greater and the
flexibility of the vehicle hit is high.
5) SUMMARY AND CONCLUSION
- The airbag only reacts to deceleration in the direction of driving. A side impact or the vehicle rolling over
cannot trigger the airbag.
- The vehicle’s projectile energy is transformed into deformation energy of the front part of the vehicle.
Deceleration is greater when the deformation of the vehicle hit is less, meaning that the airbag will trigger
much earlier.
- The minimum speed at which the airbag is triggered is greater when the angle of impact α is large (see
above).
- If, in a frontal impact, there is no deformation at the front pillars, or engine - gearbox - sub-frame impact,
the fact that the airbag was not triggered cannot be considered as a fault since the trigger speed may not
have been reached.
- The pretensioners always trigger at a lower speed than the airbag.
- Experience has shown that the impact speeds given by customers are often not correct. Their reactions are
generally reduced by shock: there is almost always confusion between the cruising speed before the im-
pact and the actual speed of the impact which is thankfully much lower in most cases.
ADirection of travel
BCentre of gravity
CImmobilised vehicle
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