Dual Stage inflation of Airbags

Dual Stage inflation of airbags





Explanation of illustration
A. Charge 1 is activated. The pressure corresponds to approximately 70% of the maximum pressure.
B. Charge 2 is activated based on a delay calculated by the SRS control module.
X. Time (ms) between the activation of stage 1 and 2.
Y. Collision energy.

Function description
The airbags on both the driver and passenger sides inflate in two stages.
- A two stage inflation system, where the pressure rise in the airbag depends on the type of collision, reduces the stresses caused to the driver and/or passenger by the deployment of the airbag in comparison to a single stage system
- Each airbag has two stages (i.e. two charges each with its own igniter). The rise in pressure in the bag can be controlled by igniting the stages at an interval adapted for the particular situation
- The SRS control module calculates the retardation rate of the car at the moment of collision, enabling it to assess the type of collision within a few milliseconds
- These calculations allow the control module to determine when igniter 1 must be activated and the amount of delay before igniter 2 must be activated.

Note! Both stages are always activated during airbag deployment. The maximum pressure of the airbag will vary, depending on the type of collision.

Activation of airbags and seat belt tensioners
The seat belt tensioners and airbags are activated in the following sequence, depending on the force of the collision and whether or not the driver and/or passenger is wearing a seat belt:





- The trigger threshold depends on the force of the impact. Level 1 = "low" impact force, Level 5 = "high" impact force
- The three rear seat belt tensioners are activated simultaneously, always at trigger threshold 3. This is irrespective of whether anybody is sitting on the rear seats or whether or not they are wearing seat belts
- The SRS control module calculates the collision process. The force of impact is included in these calculations, which enables the control module to calculate the trigger threshold that will be reached. The components are then activated in the sequence outlined above.