An air bag is an inflatable cushion designed to guard vehicle occupants from severe damage within the case of a collision. The air bag is a part of an inflatable restraint system, often known as an air cushion restraint system (ACRS) or an air bag supplemental restraint system (SRS), as a result of the air bag is designed to complement the safety provided by seat belts. Seat belts are nonetheless wanted to carry the occupant securely in place, particularly in facet impacts, rear impacts, and rollovers. Upon detecting a collision, air baggage inflate immediately to cushion the uncovered occupant with an enormous gas-filled pillow.
A typical air bag system consists of an air bag module (containing an inflator or fuel generator and an air bag), crash sensors, a diagnostic monitoring unit, a steering wheel connecting coil, and an indicator lamp. These elements are all interconnected by a wiring harness and powered by the car’s battery.
Airbag programs maintain a reserve cost after the ignition has been turned off or after the battery has been disconnected. Relying on the mannequin, the backup energy provide lasts between one second and ten minutes. Since elements important to the system’s operation may sit dormant for years, the air bag circuitry performs an inside “self-test” throughout every startup, often indicated by a light-weight on the instrument panel that glows briefly at every startup.
The crash sensors are designed to stop the air bag from inflating when the automotive goes over a bump or a pothole, or within the case of a minor collision. The inflator matches right into a module consisting of a woven nylon bag and a break-away plastic horn pad cowl. The module, in flip, matches into the steering wheel for driver’s-side purposes and above the glove compartment for entrance passenger purposes.
In a frontal collision equal to hitting a strong barrier at 9 miles per hour (14.48 kilometers per hour), the crash sensors situated within the entrance of the automotive detect the sudden deceleration and ship sign activating an initiator (typically referred to as an igniter or squib). Like a gentle bulb, an initiator incorporates a skinny wire that heats up and penetrates the propellant chamber. This causes the strong chemical propellant, principally sodium azide, sealed contained in the inflator to endure a speedy chemical response (generally known as a pyrotechnic chain). This managed response produces innocent nitrogen fuel that fills the air bag. Throughout deployment the increasing nitrogen fuel undergoes a course of that reduces the temperature and removes many of the combustion residue or ash.
The increasing nitrogen fuel inflates the nylon bag in lower than one-twentieth (1/20) of a second, splitting open its plastic module cowl and inflating in entrance of the occupant. Because the occupant contacts the bag, the nitrogen fuel is vented via openings at the back of the bag. The bag is totally inflated for under one-tenth (1/10) of a second and is sort of deflated by three-tenths (3/10) of a second after influence. Talcum powder or corn starch is used to line the within of the air bag and is launched from the airbag as it’s opened.
The airbag traces its origin to air-filled bladders outlined as early as 1941 and first patented within the 1950s. Early air bag programs
had been giant and hulking, primarily utilizing tanks of compressed or heated air, compressed nitrogen fuel (N 2 ), freon, or carbon dioxide (CO 2 ). Among the early programs created hazardous byproducts. One specific system used gun-powder to warmth up freon fuel, producing phosgene fuel (COCl 2 )—an especially toxic fuel.
One of many first patents for vehicle air baggage was awarded to industrial engineer John Hetrick on August 18, 1953. Conceived by Hetrick after a close to accident in 1952, the design referred to as for a tank of compressed air underneath the hood and inflatable baggage on the steering wheel, in the midst of the dash-board, and within the glove compartment to guard entrance seat occupants, and on the again of the entrance seat to guard rear seat passengers. The pressure of a collision would propel a sliding weight ahead to ship air into the luggage. Many different inventors and researchers adopted swimsuit, all exploring barely totally different designs, in order that the precise technical path from the early designs to the current system is inconceivable to notice with certainty.
In 1968, John Pietz, a chemist for Talley Protection Methods, pioneered a strong propellant utilizing sodium azide (NaN 3 ) and a metallic oxide. This was the primary nitrogen-generating strong propellant, and it quickly changed the older, bulkier programs. Sodium azide in its strong state is poisonous if ingested in giant doses, however in automotive purposes is fastidiously sealed inside a metal or aluminum container throughout the airbag system.
For the reason that 1960s, airbag-equipped automobiles in managed assessments and on a regular basis use have demonstrated the effectiveness and reliability. The Insurance coverage Institute For Freeway Security performed a examine of the federal authorities’s Deadly Accident Reporting System utilizing knowledge from 1985 to 1991, and concluded that driver fatalities in frontal collisions had been lowered by 28 p.c in vehicles geared up with air baggage. Based on
one other examine performed in 1989 by Common Motors, the mix of lap/shoulder security belts and air baggage in frontal collisions lowered driver fatalities by 46 p.c and entrance passenger fatalities by 43 p.c.
In response to customers’ elevated security considerations and insurance coverage business stress, the federal authorities has pressured vehicle producers to improve their security options. First, Division of Transportation (DOT) rules require all automobiles, starting with mannequin yr 1990, offered in the US to be geared up with a passive restraint system. (Passive restraint programs—requiring no activation by the occupant—contain using automated seat belts and/or using air baggage.) If automotive producers select an airbag, then rules require solely a driver’ s-side system till mannequin yr 1994, when airbag-equipped automobiles should embody passive safety on the passenger’s facet as effectively. A 1991 legislation requires driver and passenger air baggage in all automobiles by the 1998 mannequin yr and in gentle vehicles and vans by 1999.
As said above, an air bag system consists of an airbag module, crash sensors, a diagnostic monitoring unit, a steering wheel connecting coil, and an indicator lamp. Each this part and the subsequent (“The Manufacturing Course of”) will deal with the airbag module itself.
An airbag module has three fundamental elements: the airbag, the inflator, and the propellant. The airbag is sewn from a woven nylon cloth and may come in numerous styles and sizes relying on particular car necessities. The motive force’s-side airbag materials is manufactured with a warmth protect coating to guard the material from scorching, particularly close to the inflator meeting, throughout deployment. Talcum powder or corn starch can be used to coat the airbag; both substance prevents the material from sticking collectively and makes it simpler to assemble. Newer silicone and urethane coated airbag supplies require little or no warmth protect coating, though talcum powder or corn starch will most likely nonetheless be used as a processing assist.
The inflator canister or physique is comprised of both stamped stainless-steel or forged aluminum. Contained in the inflator canister is a filter meeting consisting of a stainless-steel wire mesh with ceramic materials sandwiched in between. When the inflator is assembled, the filter meeting is surrounded by steel foil to take care of a seal that forestalls propellant contamination.
The propellant, within the type of black pellets, is primarily sodium azide mixed with an oxidizer and is often situated contained in the inflator canister between the filter meeting and the initiator.
The Manufacturing Course of Airbag
Airbag manufacturing includes three totally different separate assemblies that mix to type the completed finish product, the airbag module. The propellant have to be manufactured, the inflator elements have to be assembled, and the airbag have to be minimize and sewn. Some producers purchase already-made elements, similar to air baggage or initiators, after which simply assemble the entire airbag module. The next description of the manufacturing course of is for driver-side airbag module meeting. Passenger-side airbag module assemblies are produced barely in another way.
- 1 The propellant consists of sodium azide combined along with an oxidizer, a substance that helps the sodium azide to burn when ignited. The sodium azide is acquired from outdoors distributors and inspected to verify it conforms to necessities. After inspection it’s positioned in a secure storage place till wanted. On the identical time, the oxidizer is acquired from outdoors distributors, inspected, and saved. Totally different producers use totally different oxidizers.
- 2 From storage, the sodium azide and the oxidizer are then fastidiously blended underneath subtle computerized course of management. Due to the opportunity of explosions, the powder processing takes place in remoted bunkers. Within the occasion security sensors detect a spark, excessive pace deluge programs will douse entire rooms with water. Manufacturing happens in a number of redundant smaller services in order that if an accident does happen, manufacturing is not going to be shut down, solely decreased.
- Three After mixing, the propellant combination is shipped to storage. Presses are then used to compress the propellant combination into disk or pellet type.
- four The inflator elements, such because the steel canister, the filter meeting—stainless-steel wire mesh with ceramic materials inside—and initiator (or igniter) are acquired from outdoors distributors and inspected. The elements are then assembled on a extremely automated manufacturing line.
- 5 The inflator sub-assembly is mixed with the propellant and an initiator to type the inflator meeting. Laser welding (utilizing CO 2 fuel) is used to affix stainless-steel inflator sub-assemblies, whereas friction inertial welding is used to affix aluminum inflator sub-assemblies. Laser welding entails utilizing laser beams to weld the assemblies collectively, whereas friction inertial welding includes rubbing two metals collectively till the surfaces turn into scorching sufficient to affix collectively.
- 6 The inflator meeting is then examined and despatched to storage till wanted.
- 7 The woven nylon airbag cloth is acquired from outdoors distributors and inspected for any materials defects. The air bag cloth is then die minimize to the correct shapes and sewn, internally and externally, to correctly be part of the 2 sides. After the air bag is sewn, it’s inflated and checked for any seam imperfections.
Remaining meeting of airbag module
- eight The air bag meeting is then mounted to the examined inflator meeting. Subsequent, the air bag is folded, and the breakaway plastic horn pad cowl is put in. Lastly, the finished module meeting is inspected and examined.
- 9 The module assemblies are packaged in containers for cargo after which despatched to prospects.
- 10 The remaining elements of the air bag system—the crash sensors, the diagnostic monitoring unit, the steering wheel connecting coil, and the indicator lamp—are mixed with the air bag module throughout car meeting. All of the elements are related and talk via a wiring harness.
High quality Management
The standard management side of airbag manufacturing is, clearly, essential as a result of many lives depend upon the security function. Two main areas the place high quality management is important are the pyrotechnic or propellant assessments and the airbag and inflator static and dynamic assessments.
Propellants, earlier than being inserted into inflators, are first subjected to ballistic assessments to foretell their habits. A consultant pattern of inflators are pulled from the manufacturing line and examined for correct operation by a full-scale inflator check, which measures stress—created by the generated fuel inside a big tank 15.84 or 79.20 gallons (60 or 300 liters)—versus time in milliseconds. This provides a sign of the inflator system’s potential to supply an quantity of fuel at a given fee, guaranteeing correct airbag inflation. The air baggage themselves are inspected for cloth and seam imperfections after which examined for leaks.
Automated inspections are made at each stage of the manufacturing course of line to determine errors. One airbag producer makes use of radiography (x-rays) to check the finished inflator towards a grasp configuration saved within the pc. Any inflator with out the correct configuration is rejected.
The Way forward for Airbag
The long run for air baggage seems to be extraordinarily promising as a result of there are a lot of totally different purposes doable, starting from plane seating to motorbike helmets. The air baggage of the longer term shall be extra economical to supply
and lighter in weight; will contain smaller, extra built-in programs; and can use improved sensors.
Facet-impact air baggage are one other risk that might work just like driver- and passenger-side air baggage. Facet-impact air baggage will most probably be mounted within the automotive door panels and deployed in the direction of the window throughout influence to guard the top. Foam padding across the door construction would even be used to cushion the higher physique in a facet influence. Head and/or knee bolsters (power absorbing pads) to enhance the airbag system are additionally being investigated. Rear-seat air baggage are additionally being examined however client demand is just not anticipated to be excessive.
Aftermarket airbag programs—generic programs that may be put in on any car already constructed—should not presently accessible. For the reason that effectiveness of an airbag depends upon its sensors recognizing if a crash is extreme sufficient to set off deployment, a system have to be exactly tuned to the best way a particular automotive mannequin behaves in a crash. Nonetheless, firms are exploring the longer term risk of manufacturing a modified airbag system for retrofit.
A hybrid inflator is presently being examined that makes use of a mix of pressurized inert fuel (argon) and warmth from a propellant to considerably increase the fuel’s quantity. These programs would have a price benefit, since much less propellant might be used.
Airbag producers are additionally creating programs that might get rid of the sodium azide propellant, which is poisonous in its undeployed type. Work can be underway to enhance the coatings that protect the airbag and facilitate its opening. Ultimately the luggage might not want coatings in any respect.
Sooner or later, extra subtle sensors referred to as “good” sensors shall be used to tailor the deployment of the airbag to sure situations. These sensors might be used to sense the dimensions and weight of the occupant, whether or not the occupant is current (particularly within the case of passenger-side air baggage the place deployment could also be pointless if there are not any passengers), and the proximity of the driving force to the steering wheel (a driver slumped over the steering wheel might be severely injured by an airbag deployment).