Air Bag: Description and Operation

SRS Airbag
The SRS is a safety device which, when used in conjunction with the seat belt, is designed to help protect the driver and front passenger in a frontal impact exceeding a certain set limit. The system consists of the SRS unit (including safing sensor [side airbag models] and frontal impact sensor), the cable reel, the driver's airbag, front passenger's airbag, and side airbags (if equipped).


Side Airbags

Side airbags located in each front seat-back can help protect the upper torso of the driver or front seat passenger during a moderate to severe side impact. Sensors in each door sill and in the SRS unit detect such an impact and instantly inflate the driver's or the passenger's side airbag. Only one side airbag will deploy during a side impact. If the impact is on the passenger's side, the passenger's side airbag will deploy even if there is no passenger.

The side airbag system also includes an Occupant Position Detection System (OPDS). This system consists of sensors and a control unit located in the front passenger's seat-back. The control unit sends occupant height and position data to the SRS unit. If the SRS unit determines that the front passenger's head is in the deployment path of the side airbag, it will automatically disable the airbag. When the side airbag is disabled, the Side Airbag indicator light in the gauge assembly alerts the driver that the passenger's side airbag will not deploy in a side impact.

Operation
The main circuit in the SRS unit senses and judges the force of impact and, if necessary, ignites the inflator charges. If battery voltage is too low or power is disconnected due to the impact, the voltage regulator and the back-up power circuit respectively will keep voltage at a constant level.




For the SRS to operate
1. The side impact sensors must activate, and send electric signals to the microprocessor.
2. The microprocessor must compute the signals and send them to the side airbag inflators. However the microprocessor cuts off the signals to the front passenger's side airbag if the SRS unit determines that the front passenger's head is in the deployment path of the side airbag.
3. The inflator that received the signal must ignite and deploy the side airbag.