Airbag
An airbag or supplemental inflatable restraint is a vehicle occupant-restraint system using a bag designed to inflate in milliseconds during a collision and then deflate afterwards. It consists of an airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. The purpose of the airbag is to provide a vehicle occupant with soft cushioning and restraint during a collision. It can reduce injuries between the flailing occupant and the vehicle's interior.
The airbag provides an energy-absorbing surface between the vehicle's occupants and a steering wheel, instrument panel, body pillar, headliner, and windshield. Modern vehicles may contain up to ten airbag modules in various configurations, including driver, passenger, side-curtain, seat-mounted, door-mounted, B- and C-pillar mounted side-impact, knee bolster, inflatable seat belt, and pedestrian airbag modules.
During a crash, the vehicle's crash sensors provide crucial information to the airbag electronic controller unit, including collision type, angle, and severity of impact. Using this information, the airbag ECU's crash algorithm determines if the crash event meets the criteria for deployment and triggers various firing circuits to deploy one or more airbag modules within the vehicle. Airbag module deployments are activated through a pyrotechnic process designed to be used once as a supplemental restraint system for the vehicle's seat belt systems. Newer side-impact airbag modules consist of compressed-air cylinders that are triggered in the event of a side-on vehicle impact.
The first commercial designs were introduced in passenger automobiles during the 1970s. These designs saw limited success and caused some fatalities. Broad commercial adoption of airbags occurred in many markets during the late 1980s and early 1990s.
Active vs. passive safety
Airbags are considered "passive" restraints and act as a supplement to "active" restraints. Because no action by a vehicle occupant is required to activate or use the airbag, it is considered a "passive" device. This is in contrast to seat belts, which are considered "active" devices because the vehicle occupant must act to enable them.This terminology is not related to active and passive safety, which are, respectively, systems designed to prevent collisions in the first place, and systems designed to minimize the effects of collisions once they occur. In this use, a car Anti-lock braking system qualifies as an active-safety device, while both its seat belts and airbags qualify as passive-safety devices. Terminological confusion can arise from the fact that passive devices and systems—those requiring no input or action by the vehicle occupant—can operate independently in an active manner; an airbag is one such device. Vehicle safety professionals are generally careful in their use of language to avoid this sort of confusion. However, advertising principles sometimes prevent such semantic caution in the consumer marketing of safety features. Further confusing the terminology, the aviation safety community uses the terms "active" and "passive" in the opposite sense from the automotive industry.
History
Origins
The airbag "for the covering of aeroplane and other vehicle parts" traces its origins to a United States patent, submitted in 1919 by two dentists from Birmingham, Arthur Parrott and Harold Round. The patent was approved in 1920. Air-filled bladders were in use as early as 1951. The airbag specifically for automobile use is credited independently to the American John W. Hetrick, who filed for an airbag patent on 5 August 1952, that was granted #2,649,311 by the United States Patent Office on 18 August 1953. German patent #896,312 filed for by engineer Walter Linderer on 6 October 1951 was issued on 12 November 1953, approximately three months after American John Hetrick. The airbags proposed by Hetrick and Linderer were based on compressed air released by a spring, bumper contact, or by the driver. Later research during the 1960s showed that compressed air could not inflate the mechanical airbags fast enough to ensure maximum safety, leading to the current chemical and electrical airbags. In patent applications, manufacturers sometimes use the term "inflatable occupant restraint systems".Hetrick was an industrial engineer and member of the United States Navy. His airbag design, however, only came about when he combined his experiences working with navy torpedoes with his desire to protect his family on the road. Despite working with the major automobile manufacturers of his time, Hetrick was unable to attract investment. Although airbags are now required in every automobile sold in the United States, Hetrick's 1951 patent filing serves as an example of a "valuable" invention with little economic value to its inventor. Its first commercial use was not implemented until after the patent expired in 1971, at which point the airbag was installed in a few experimental Ford cars.
In 1964, a Japanese automobile engineer, Yasuzaburou Kobori, started developing an airbag "safety net" system. His design harnessed an explosive to inflate an airbag, for which he was later awarded patents in 14 countries. He died in 1975, before seeing the widespread adoption of airbag systems.
In 1967, a breakthrough in developing airbag crash sensors came when Allen K. Breed invented a ball-in-tube mechanism for crash detection. Under his system, an electromechanical sensor with a steel ball attached to a tube by a magnet would inflate an airbag in under 30 milliseconds. A small explosion of sodium azide was used instead of compressed air during inflation for the first time. Breed Corporation then marketed this innovation to Chrysler. A similar "Auto-Ceptor" crash-restraint, developed by the Eaton, Yale & Towne company for Ford, was soon also offered as an automatic safety system in the United States, while the Italian Eaton-Livia company offered a variant with localized air cushions.
In the early 1970s, General Motors began offering cars equipped with airbags, initially in government fleet-purchased 1973 Chevrolet Impala sedans. These cars came with a 1974-style Oldsmobile instrument panel and a unique steering wheel that contained the driver-side airbag. Two of these cars were crash tested after 20 years and the airbags deployed perfectly. An early example of the airbag cars survives as of 2009. GM's Oldsmobile Toronado was the first domestic U.S. vehicle to include a passenger airbag in 1973. General Motors marketed its first airbag modules under the "Air Cushion Restraint System" name, or ACRS. The automaker discontinued the option for its 1977 model year, citing a lack of consumer interest. Ford and GM then spent years lobbying against air-bag requirements, claiming that the devices were unfeasible and inappropriate. Chrysler made driver-side airbags standard on 1988 and 1989 models, but airbags did not become widespread in American cars until the early 1990s.
As a substitute for seat belts
Airbags for passenger cars were introduced in the United States in the 1970s. When seat-belt usage rates in the country were quite low compared to modern-day, Ford built experimental cars with airbags in 1971. Allstate operated a fleet of 200 Mercury Montereys and showed the reliability of airbags as well as their operation in crash testing, which also was promoted by the insurance company in popular magazine advertisements. General Motors followed in 1973 using full-sized Chevrolet vehicles. The early fleet of experimental GM vehicles equipped with airbags experienced seven fatalities, one of which was later suspected to have been caused by the airbag.In 1974, GM made its ACRS system available as a regular production option in full-sized Cadillac, Buick and Oldsmobile models. The GM cars from the 1970s equipped with ACRS had a driver-side airbag, and a driver-side knee restraint. The passenger-side airbag protected both front passengers, and unlike most modern systems, integrated a knee and torso cushion while also having a dual-stage deployment dictated by force of the impact. The cars equipped with ACRS had lap belts for all seating positions, but lacked shoulder belts. Shoulder belts were already mandatory in the United States on closed cars without airbags for the driver and outer front passenger, but GM chose to market its airbags as a substitute for shoulder belts. Prices for this option on Cadillac models were US$225 in 1974, $300 in 1975, and $340 in 1976.
The early development of airbags coincided with international interest in automobile safety legislation. Some safety experts advocated a performance-based occupant-protection standard rather than one mandating a particular technical solution. Less emphasis was placed on other designs as countries successfully mandated seat belt restrictions, however.
As a supplemental restraint system
Frontal airbag
The auto industry and research and regulatory communities have moved away from their initial view of the airbag as a seat-belt replacement, and the bags are now nominally designated as supplemental restraint systems or supplemental inflatable restraints.In 1981, Mercedes-Benz introduced the airbag in West Germany as an option on its flagship saloon model, S-Class. In the Mercedes system, the sensors automatically tensioned the seat belts to reduce occupants' motion on impact and then deployed the airbag on impact. This integrated the seat belts and the airbag into a restraint system, rather than the airbag being considered an alternative to the seat belt.
In 1987, the Porsche 944 Turbo became the first car to have driver and passenger airbags as standard equipment. The Porsche 944 and 944S had this as an available option. The same year also had the first airbag in a Japanese car, the Honda Legend.
In 1988, Chrysler became the first United States automaker to fit a driver-side airbag as standard equipment, which was offered in six different models. The following year, Chrysler became the first US auto manufacturer to offer driver-side airbags in all its new passenger models. Chrysler also began featuring the airbags in advertisements showing how the devices had saved lives that helped the public know the value of them and safety became a selling advantage in the late 1980s. All versions of the Chrysler minivans came with airbags starting for the 1991 model year. In 1993, The Lincoln Motor Company boasted that all vehicles in their model line were equipped with dual airbags, one for the driver's side and another for the passenger's side. The 1993 Jeep Grand Cherokee became the first SUV to offer a driver-side airbag when it was launched in 1992. Driver and passenger airbags became standard equipment in all Dodge Intrepid, Eagle Vision, and Chrysler Concorde sedans ahead of any safety regulations. Early 1993 saw the 4-millionth airbag-equipped Chrysler vehicle roll off the assembly line. In October 1993, the Dodge Ram became the first pickup truck with a standard driver-side airbag.
The first known collision between two airbag-equipped automobiles took place on 12 March 1990 in Virginia, USA. A 1989 Chrysler LeBaron crossed the center line and hit another 1989 Chrysler LeBaron in a head-on collision, causing both driver airbags to deploy. The drivers suffered only minor injuries despite extensive damage to the vehicles.
The United States Intermodal Surface Transportation Efficiency Act of 1991 required passenger cars and light trucks built after 1 September 1998 to have airbags for the driver and the front passenger. In the United States, NHTSA estimated that airbags had saved over 4,600 lives by 1 September 1999; however, the crash deployment experience of the early 1990s installations indicated that some fatalities and serious injuries were in fact caused by airbags. In 1998, NHTSA initiated new rules for advanced airbags that gave automakers more flexibility in devising effective technological solutions. The revised rules also required improved protection for occupants of different sizes regardless of whether they use seat belts, while minimizing the risk to infants, children, and other occupants caused by airbags.
In Europe, airbags were almost unheard of until the early 1990s. By 1991, four manufacturers – BMW, Honda, Mercedes-Benz, and Volvo – offered the airbag on some of their higher-end models, but shortly afterward, airbags became a common feature on more mainstream cars, with Ford and Vauxhall/Opel among the manufacturers to introduce the airbag to its model ranges in 1992. Citroën, Fiat, Nissan, Hyundai, Peugeot, Renault, and Volkswagen followed shortly afterwards.
By 1999, finding a new mass-market car without an airbag at least as optional equipment was difficult, and some late 1990s products, such as the Volkswagen Golf Mk4, also featured side airbags. The Peugeot 306 is one example of the European automotive mass-market evolution: starting in early 1993, most of these models did not even offer a driver's airbag as an option, but by 1999, even side airbags were available on several variants. Audi was late to offer airbag systems on a broader scale, since even in the 1994 model year, its popular models did not offer airbags. Instead, the German automaker until then relied solely on its proprietary cable-based procon-ten restraint system.
Variable force-deployment front airbags were developed to help minimize injury from the airbag itself.
The emergence of the airbag has contributed to a sharp decline in the number of deaths and serious injuries on the roads of Europe since 1990, and by 2010, the number of cars on European roads lacking an airbag represented a very small percentage of cars, mostly the remaining cars dating from the mid-1990s or earlier.
Many new cars in Latin America, including the Kia Rio, Kia Picanto, Hyundai Grand i10, Mazda 2, Chevrolet Spark and the Chevrolet Onix, are often sold without airbags, as neither airbags nor automatic braking systems in new cars are compulsory in many Latin American countries. Some require the installation of a minimum of only two airbags in new cars which many in this market have.