Week 9 : Restraint System (Air Bag) part 1

The Air Bag system

An air bag is an inflatable cushion designed to protect automobile occupants from serious injury in the case of a collision. The air bag is part of an inflatable restraint system, also known as an air cushion restraint system (ACRS) or an air bag supplemental restraint system (SRS), because the air bag is designed to supplement the protection offered by seat belts. Seat belts are still needed to hold the occupant securely in place, especially in side impacts, rear impacts, and rollovers. Upon detecting a collision, air bags inflate instantly to cushion the exposed occupant with a big gas-filled pillow.

History

The air bag traces its origin to air-filled bladders outlined as early as 1941 and first patented in the 1950s. Early air bag systems were large and bulky, primarily using tanks of compressed or heated air, compressed nitrogen gas (N₂), freon, or carbon dioxide (CO₂). Some of the early systems created hazardous byproducts. One particular system used gun-powder to heat up freon gas, producing phosgene gas (COCl₂)—an extremely poisonous gas.

Raw Materials

As stated above, an air bag system consists of an air bag module, crash sensors, a diagnostic monitoring unit, a steering wheel connecting coil, and an indicator lamp. Both this section and the next ("The Manufacturing Process") will focus on the air bag module itself.

An air bag module has three main parts: the air bag, the inflator, and the propellant. The air bag is sewn from a woven nylon fabric and can come in different shapes and sizes depending on specific vehicle requirements. The driver's-side air bag material is manufactured with a heat shield coating to protect the fabric from scorching, especially near the inflator assembly, during deployment. Talcum powder or corn starch is also used to coat the air bag; either substance prevents the fabric from sticking together and makes it easier to assemble. Newer silicone and urethane coated air bag materials require little or no heat shield coating, although talcum powder or corn starch will probably still be used as a processing aid.

The inflator canister or body is made from either stamped stainless steel or cast aluminum. Inside the inflator canister is a filter assembly consisting of a stainless steel wire mesh with ceramic material sandwiched in between. When the inflator is assembled, the filter assembly is surrounded by metal foil to maintain a seal that prevents propellant contamination.

that all for today entry.. next entry we will tell about the manufacturing proses, and also the future design of air bag.

so wait for the next entry.. see you soon.. :)