(1)For driver (in steering wheel pad)
The driver’s seat SRS airbag assembly is stored in the steering wheel pad. SRS airbag assembly cannot be disassembled. It consists of the inflator, bag and steering wheel pad, etc.
The airbag sensor is activated by deceleration due to severe frontal collision. Electric current flows into the initiator, located in the inflator, to ignite it. The flame spreads instantaneously to the propellant grain, from which a large amount of nitrogen gas is generated. The gas flows through the filter where cinders are removed and the gas is cooled before filling the bag. Then, as it expands, the driver’s bag tears open the wheel pad outer layer to further expand and to help to restrain the impact applied to the head of the driver.
There is also a dual type inflator that controls the deployment in two levels. According to the slide position of the seat, whether or not the seatbelt is fastened, and the impact degree of the collision, this controls the optimal deployment of the airbag.
(2)For front passenger (in instrument panel)
The inflator is comprised of an initiator, projectile, closure disk, propellant grain, high-pressure gas, etc. The bag becomes inflated by the high-pressure gas flowing from the inflator. The inflator and bag are integrated inside the case, and located in the passenger side instrument panel.
If the airbag sensor is turned on by deceleration due to frontal collision, electric current flows into the initiator, located in the inflator, to ignite it. The projectile, which was fired by the ignition of the initiator, pierces through the closure disk and collides with the action piston, which causes the primer to ignite. The flame of the primer spreads instantaneously to the ignition booster and to the propellant grain. The gas which expanded by the heat of the ignition of the propellant grain flows into the airbag via the gas release hole, thus inflating the airbag. The airbag pushes the airbag door open to further expand and to help restrain the impact applied to the head and chest of the front passenger.
There is also a dual type inflator that controls the deployment in two levels, and two each of the initiator and propellant grain. According to the degree of the collision, optimal deployment speed is performed. The degree of the impact is detected by the airbag sensor system and when the impact is large, initiator A and B are ignited at the same time. When the impact is small, the ignition timing of B is retarded to deploy the airbag at a gentler speed than the single type.
(3)For side airbag
The basic construction of the side airbag is same as that of the front passenger airbag. The side airbag assembly is integrated inside the case and located in the outer side of the seatback. The side airbag assembly is comprises of an initiator, propellant grain, high-pressure gas and pressure bulkhead.
If the airbag sensor is activated by deceleration due to side collision, electric current flows into the initiator, located in the inflator, to ignite it. The combustion gas that is generated by the combustion of the propellant grain causes the pressure bulkhead to tear, enabling the heat of the combustion gas to expand the high-pressure gas. Then, this pressure tears the rapture disc, allowing the high-pressure gas in the bottle to blow into the airbag and inflate the airbag instantly.
(4)Curtain shield airbag assembly
The inflator of curtain shield airbag assembly is installed on the rear or front pillar. The compressive bag of the curtain shield airbag assembly is installed on the roof panel. The curtain shield airbag assembly comprises an igniter, bracket, nail, break washer, bag, etc.
According to the igniting signal from the center airbag sensor assembly, electric current flows into the initiator and the igniter is ignited. This ignition starts combustion of the generator gas and the resulting heat breaks the break washer. After that the high-pressure gas passes through the outer hole to be blown into the airbag. Thus, the airbag is instantaneously deployed.
SRS Airbag Construction and Operation – Inflator and bag
(1)For driver (in steering wheel pad)