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Created on Sunday, 21 October 2012 07:28
The seat belt, being one of the so-called passive safety systems in cars, has resulted in reduction of fatalities in accidents by 36%. The seat belt prevents the passenger from hitting the hard parts of the front of the vehicle including the steering wheel, the dashboard, and the windshield. However, it cannot protect the passengers fully against all possible impacts. The air bag system was developed as a supplement to the seat belt system reducing the fatalities of dangerous accidents to an additional 18%. This system has mechanical and electronic components.
A number of different airbags can be used for each vehicle: the most widely used are driver and front seat passenger airbags. More luxurious vehicles benefit from side airbags (covering side windows) and rear seat passenger air bags which are installed on head rests front seats. Some cars such as some models of Mercedes Benz are also equipped with roof air bags operating at times of roll over.
Main components of the electronic system
1- Crash sensors: these calculate the intensity of impact from front of the vehicle and send the appropriate signal to the electronic control unit.
2- SAS control module: This unit processes the data sent from sensors and if rapid deceleration due to collision is detected, a current signal is sent to the airbag module.
3- Clock Spring: Since the airbag module is located on the steering wheel which rotates frequently to left and right, there needs to be a robust connection between the steering wheel and the inflator which is the role of the clock spring
4- Airbag module: the current sent from the SAS unit goes to the primer in the module creating heat. This heat produces spark and flames which ignite the explosive material which produce rapidly expanding gases. These gases pass filters which reduce its noise and temperature and the cover on the steering wheel is torn by the airbag which inflates towards the face of the driver. The holes on the airbag help some of the inflating gas discharge which reduces the intensity of the shock and creates adequate visual space for the driver.
Translated by: Ehsan Taghdiri
CMM Labratory
