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Air bags
- 1. AIR BAGS SYSTEM INFOUR WHEELERS
- 2. INTRODUCTION • An airbag system is an automative Safety restrain system for an occupant and as well as passenger. The system consists of a flexible fabric envelope or cushion designed to expand rapidly during collision. • It is a safety device used in four wheelers to avoid major head injuries and chest injuries from collision by providing cushion in between occupant and interior of four wheelers
- 3. PURPOSE OF AIRBAGS • The purpose of an airbag is to help the occupant in the car by reduce the speed Of occupant in case of collision, before getting injured. • To protect occupants during a crash and provide protection to their bodies before they strike interior objects such as steering wheel or a window. • Comparing to seat belt alone, air bags have reduced death by 28%, serious injury by 29% and hospitalization by 24% .
- 4. PHYSICS BEHIND THEAIRBAG DURING COLLISION • In the case of collision car starts to decelerate (lose speed) rapidly but body of the person in the car does not decelerate rapidly, it follows Newton’s first law(law of inertia) An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an external force. • It means body of the person continues its motion until it hit something like steering wheel , dash board or side window. • According to Newton’s second law of motion Force(F) = mass (m) x accelration(a) • Due to more accelration when body hits steering wheel or dashboard person affected to more force and get major injuries to avoid this major injuries airbags are used
- 5. CONTINUE..... • Accelration(a) =velocity(v)/time interval(∆t) • The injuries can be avoided by reducing the force on the body this can be done by two ways a: 1)By increasing the time interval (∆t) over the force being applied
- 6. CONTINUE..... 2) By spreadingforce over the large area
- 7. DESIGN AND CONSTRUCTIONOF AIR BAG SYSTEM 1. There are four parts in airbag safety system to accomplish the action 1.Air bags 2. Sensors 3. Air bag control unit(ACU) 4. Inflating system
- 8. AIR BAG CONTROLUNIT • The airbags in the vehicle are controlled by a central airbag control unit (ACU) . The ACU monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, side (door) pressure sensors,wheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors • In case of crash ACU Passes electric current to inflation system • An ACU includes capacitor with in its circuit so it can pass electric current when battery lose connection with ACU in case of crash.
- 9. AIR BAG INFLATIONSYSTEM • The electric current from Airbag control unit burns the propellant which generates gas to make explosion which inflates the airbag rapidly in approximately 20 to 30 milliseconds
- 10. CHEMICAL REACTIONS USEDTO GENERATE GAS TO FILL AIRBAGS • Inside the airbag is a gas generator containing a mixture of NaN3, KNO3, and SiO2. When the car undergoes a head-on collision, a series of three chemical reactions inside the gas generator produce gas (N2) to fill the airbag and convert sodium azide(NaN3) to silicate glass. The purpose of the KNO3 and SiO2 is to remove the sodium metal • The reactions in order are as follows 1. 2 NaN3 → 2 Na + 3 N2 (g) 2. 10 Na + 2 KNO3 → K2O + 5 Na2O + N2 (g) 3. K2O + Na2O + 2 SiO2 → K2SiO3 + Na2SiO3 • After chemical reactions Airbags open with the maximum speed of 98.46meters per second in minimum 42 milli seconds of crash
- 11. OPERATION SEQUENCE OFAIR BAG • Collision • Sensing and inflation • Fully deployed • Deflation
- 12. TYPES OF AIRBAGS Driver side airbag Passenger airbag Knee airbag
- 13. TYPES OF AIRBAG Curtain airbag Side thorax air bag Door mounted side airbag
- 14. THE FUNDAMENTAL CHARACTERISTCS REQUIREDBY AIRBAGS FABRIC • High bursting strength • Light weight • Good fire retardancy • Compact folding ability • Low cost • Reduced skin abrasion(softness) • High tear propagation resistance • Resistance against aging • Defined dimension stability • Air seal ability(low air permeability) • Good coating adhesion • Good fog resistance
- 15. RAW MATERIAL ANDMANUFACTURING METHOD Following fibers are mostly used in airbags • Nylon6 • Nylon66 • Polyster • PA46 PA46 has higher melting point(285°C) than nylon66(260°C) but cost of PA46 is higher Fiber Yarn Fabric Coating Cut/Sew Air bag
- 16. FINISHING PROCESS • Requiredshape from the fabric is obtained by laser cutting • Nylonn66, Polyster are used for sewing Calendaring Desizing Heat set Inspection Folding Sewing Cutting
- 17. COMPARING TWO TYPESOF AIR BAG FIBERS •Nylon Vs Polyster Properties Nylon-66 Polyster Specific heat (kj/kg.K) 1.67 1.3 Melting point(°C) 260 258 Softening point(°C) 220 220 Energy to melt (kj/kg) 589 427 Density(kg/m³) 1140 1390
- 18. CONTINUE.... • Polyester givesless thermal protection to the passenger than nylon-66 • Polyester has higher air permeability and nylon-66 has lower air permeability • Polyester has higher seam strength and nylon has lower seam strength
- 19. INTRODUCING AIRBAGS INTOCARS • 1973 - The Oldsmobile Toronado became the first car with a passenger airbag. • 1974 - Buick, Cadillac and Oldsmobile offer dual airbags as an option on several of their full-sized cars. • 1980 - Mercedes-Benz re-introduced the airbag in Germany as an option on its high-end model W126. • Mid-1980's - Ford and Chrysler introduce airbags in their vehicles;• 1990 - Ford makes airbags standard equipment in its vehicles. • 1990 - The first recorded accident between two vehicles in which an airbag deploys to protect each driver occurs on March 12, 1990. • 1995 - Volvo offers side airbags and torso side protection airbags as an option on its 850 models. • 1998 - The federal government mandates duel frontal airbags on all passenger vehicles First airbags equipped car
- 20. DEVELOPMENT OF AIRBAGS •Airbags in their earliest form, they came pre-deployed, just air filled bladders for extra cushioning in the event of accidents. The deployment system has been the largest challenge in their execution. • In 1967, a breakthrough in the development of 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.
- 21. DEVELOPMENT OF AIRBAGS •1973 Chevrolet Impala sedans. These cars came with a 1974-style Oldsmobile instrument panel and a special steering wheel that contained the driver-side air bag. Two of these cars were crash tested after 20 years and the airbags deployed perfectly. • In 1981, Mercedes-Benz introduced the airbag in West Germany as an option on its flagship saloon model, S-Class (W126). In the Mercedes system, the sensors automatically tensioned the seat belts to reduce occupants' motion on impact (now a common feature), and then deployed the airbag on impact. This integrated the seat belts and airbag into a restraint system, rather than the airbag being considered an alternative to the seat belt. • In 1991 Allen breed invention -- patent No. 5,071,161 -- was designed to "reduce the risk of secondary injuries by reducing the inflated bag's rigidity.“
- 22. HISTORY OF AIRBAGS •Airbags are an idea that has been in development since 1941. The patent for the first airbag was issued to John Hetrick in 1953.Originally the air bag was called as a “safety cushion” at that time. • In 1953 another inventor Walter Linderer got patent for his own design of an air bag.He called it as “inflatable cushion”. • In 1963 a Japanese inventor, Yasuzaburou Kobori, came up with a more reliable system, the first prototypes of what is used today. Although he received patents in 14 countries
- 23. HISTORY OF AIRBAGS •In 1967, a mechanical engineer named Allen Breed created the first reliable airbags with sensors, which many consider as the start of the airbag industry. His crash sensing technology was considered as the first electromechanical automotive airbag system in the world. Allen Breed invented to crash sensing device that cost less than ten dollars to manufacture .It was this key piece of technology that allowed the advancement of air bags to all car manufacturers. • That same year, Mercedes-Benz also started to develop airbags for its vehicles. Allen K. Breed
- 24. HISTORY OF AIRBAGS •In 1973, General Motors Oldsmobile Toronado became the first car ever with a passenger airbag. Later on, General Motors made its own air cushion restraint system (ACRS) available as an option for regular production cars such as Cadillacs, Oldsmobile and Buick models during 1974. They made cars equipped with ACRS on the driver side, driver- side knee restraint, and the passenger side. The passenger side airbag protects front passengers, and also included a dual stage deployment, which depended on the force of impact. • By 1990, Ford also made airbags as standard equipment in their vehicles.