10-09-2016, 12:28 PM
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1.INTRODUCTION
For years, the trusty seat belt provided the sole form of passive restraint inour cars. There were debated about their safety, especially relating tochildren. But over time, mush of the country adopted mandatory seat-beltlaws. Statistics have shown that the use of seat belts has saved thousandsof lives that might have been lost in collisions.Air Bags have been under development for many years. The attractionof a soft pillow to land against in a crash must be very strong – the firstpatent on an inflatable crash-landing device for airplanes was filed duringWorld War II. In the 1980’s the first commercial air bags appeared inautomobiles.Since 1988, all new cars have been required to have air bags on bothdriver and passenger sides (Light Trucks came under the rule in 1999). Todate, Statistics show that air bags reduce the risk of dying in a direct frontalcrash by 30 percent. Newer than steering Wheel mounted or Dashboard-mounted bags, but not so widely used, are seat-mounted and door mountedside air-bags. Some experts say that within the next few years, our cars willgo from having dual air bags top having six or even eight air bags. Havingevoked some of the controversy that surrounded seat-belt use in its earlyyears, air bags are the subject of serious government and industry researchand tests.
2. THE BASICS OF AIR BAGS
Before looking at specifics, let’s review our knowledge of the laws of themotion. First, we know that moving objects have momentum (the product of the mass and velocity of an object. Unless an outside force acts on anobject, the object will continue to move its present speed and direction.Cars consist of several objects, including the vehicle itself, Loose objects inthe car and, of course, passengers. If these objects are not restrained, theywill continue moving at whatever speed the car is traveling at, even if thecar is stopped by a collision.Stopping an object’s momentum requires force acting over a period of time. When a car crashes, the force required to stop an object is very greatbecause the car’s momentum has changed instantly while the passengers’ has not much time to work with. The goal of any supplemental restraintsystem is to help stop the passenger while doing as little damage to him orher as possible.What an air bag wants to do is to slow the passengers’ speed to zerowith little or no damage. The constraints that it has to work within arehuge. The air bag has the space between the passenger and the steeringwheel or dashboard and a fraction of a second to work with. Even that tinyamount of space and time is valuable, however, if the system can slow thepassenger evenly rather than forcing an abrupt halt to his or her motion.
3. DEVELOPMENT OF AIR BAGS
The idea of using a rapidly inflating cushion to prevent crash injuries has along history. The first patent on an inflatable crash-landing device forairplanes was filed during World War II.Early efforts to adapt the air bag for use in cars bumped up againstprohibitive prices and technical hurdles involving the storage and release of compressed gas.
•
If there was enough room in a car for a gas canister.
•
Whether the gas would remain contained at high pressure for thelife of the car.
•
How the bag could be made to expand quickly and reliably at avariety of operating temperatures and without emitting an ear-splittingbang.They needed a way to set off a chemical reaction that would produce thenitrogen that would inflate the bag. Small solid-propellant inflators came torescue in the 1970’s.In the early days of auto air bags, experts cautioned that the new devicewas to be used in tandem with the seat belt. Seat belts were still completelynecessary because airbags worked only in front-end collisions occurring atmore than 6 Kmph. Only Seat belts could help in side swipes and crashes(Although side-mounted air bags are becoming more common now), rearend collisions and secondary impacts. Even as the technology advances, airbags still are only effective when used with a lap/Shoulder seat belt.
4.MAIN PARTS OF AIR BAG
There are three parts to an air bag that help to accomplish this feat:1.Bag2.Sensor3.Inflation system
BAG
The bag itself is made of a thin, nylon fabric, which is folded into thesteering wheel or dashboard or, more recently, the seat or door. Thepowdery substance released from their sir bag, by the way, is regular
cornstarch or talcum powder, which is used by the air bag manufacturers tokeep the bags pliable and lubricated while they’re in storage.
SENSOR
The sensor is the device that tells the bag to inflate. It works with thecontrol module to discriminate between crash and non-crash events. Thesesensors measure the severity of the impact. Inflation happens when there isa collision force equal to running into a brick wall at 16 to 24 Km per hour.They are setup so that sudden negative acceleration will cause the contactsto close, telling the control module that a crash before airbag deployment.
INFLATION SYSTEM
The air bag’s inflation system reacts sodium azide(NaN3) with potassiumnitrate (KNO3) to produce large volume of nitrogen gas. Hot Blasts of thenitrogen inflate the air bag from its storage site up to 322Kmph. A Secondlater, the gas quickly dissipates through a tiny holes in the bag, thusdeflating the bag so you can move.
CONSTRUCTION OF AIR BAGS
Airbag are assemblies consisting of the airbag (made of Nylon), inflatormodules and sensor housing, electrical connectors (Clock spring), airbagretainer and the cover. The driver’s side bag is mounted in the center of thesteering wheel.
5.SENSOR TYPES
Ball and Magnet Type Sensor
Spring and Roller type
By function, there are 2 types- Impact sensors and safing sensors. TheForward sensors are located in various locations forward of the passengercompartment. Some are located inside the fenders, some are on the cowl,and some are attached to the core support in front of the radiator.
Rear Sensors are also known as safing sensors as their functions is todetermine that a crash has occurred. Rear safing sensors are located invarious locations in the passenger compartment depending on themanufacturer. Some are integrated with the control/Diagnostic Module.The Rear safing sensor must close before the forward sensors to avoidairbag deployment in cases where the impact is not severe enough to causedeployment. When the vehicle is parked with ignition off deployment is veryunlikely because there is no power to the circuits for deployment this meansthat someone can hit your car and sound the alarm but not deploy theairbags.
nflator Assembly
This is a diagram of a typical inflator assembly behind the steering wheel.
When the control Module activates the airbag assembly, an electriccurrent is sent to the detonator, which ignites the sodium azidepellets.When it burns, it releases nitrogen gas very quickly and in large quantities.This is what inflates the airbag.
Sodium Azide
Sodium Azide is Rocket fuel. Sodium azide is a solid propellant with a veryhigh gas generation ratio. It is very stable in this application.When Sodium azide burns, its major product is nitrogen gas, which makesup around 78% of the Earth’s atmosphere. One of the other by-products issodium hydroxide. This is commonly known as Lye, which is a causticcompound. The quantities produced are very small and present a very smallrisk of burns. The white powder residue seen after inflation is commoncornstarch, used as lubricant for expansion of the airbag. Testing isunderway with inflators that release argon gas.
6.WORKING OF AIR BAGS
Air Bags are designed to inflate in frontal or frontal-angle impacts in whichthe car strikes an immovable object at more than about 16 Kilometers perhour or another car at twice that speed. After a collision, sensors sense anelectric current to an igniter system or, in some cases, to the computerizedcontrol unit. This unit evaluates the situation and then sends an electricalimpulse to the igniter system. The electric current heats a filament (wire),which then ignites a capsule. The Ignited capsule supplies the heat to ignitegas-generating pellets. In most systems, the pellets are made of sodiumazide and produce nitrogen gas when they burn. In other systems,pressurized argon gas is used instead. The gas then expands quickly andinflates the airbag, which then breaks through a plastic cover in the steeringwheel or, the dashboard on the passenger side. The whole process takesabout 0.1 second from the exact moment the crash is detected. The air bagstarts to deflate immediately, venting the harmless gas through holes in theback of the bag of the through the fabric itself.
7.MODERN TYPES OF AIR BAGS
1.Curtain Airbags
Curtain airbags are airbags that inflate in front of vehicle windows to providepassengers better head and neck protection. The curtain airbags are part of new rollover protection system. Most equipped cars will have verticallyinflating curtain airbags in the headliner trim just above the windows, whilesome will have them inflate horizontally from the side pillar between thedoors. In some cases, curtain airbags will deploy in a fraction of a second.Sensors in the side pillar will measure the force of side-impact Collisions. If the sensors measure a strong impact, then the curtain airbags will deploy ina fraction of a second. The curtain airbag will drop straight down over the
13
windows to keep the occupants’ heads from striking the window or theintruding nose of another vehicle.
The system will use sensors that measure tipping rather than impact.These sensors send information to a central module, which will determine if the vehicle is beginning to roll over. If the vehicle is tipping into a roll, thesensors will deploy the curtain airbag. Stored in the headliner above thedoors, the cells of the inflatable curtains are inflated in less than 25thousands of a second in a triggering accident. To avoid stitches from sewingthe bag, its cells are woven on the loom directly from the yarn usingAutoliv’s one piece-weaving technology. Therefore the bag can remaininflated for several seconds, which is imperative in roll-over accidents. Coolgas will keep it inflated for up to six seconds.Laboratory tests have shown that the so-called Head Injury Criterion(HIC) can be reduced by approximately 80%. The Inflatable Curtain wasdeveloped in cooperation with Mercedes and Volvo.Car manufacturers selling car with these as standard equipment are
Alfa Romeo, Audi, BMW and Volvo.
2. Head-Thorax Bag
The Head-Thorax Side-Impact Airbag has an extension from the regularThorax Bag that protects the head. It was introduced in 1998 and developedin cooperation with Ford and Renault.
3. Inflatable Tubular Structure (ITS)
The Inflatable Tubular Structure (ITS), the world’s first airbag for headprotection, was introduced on BMW cars. It consists of a unique nylon tube,installed in the head-liner above the frontal doors that inflates to a diameterof about 15 centimeters (5 inches).
8.FUTURE OF AIR BAGS
Smart Systems
The smart airbag of the future is not just the airbag, but also a redesign of the components in the current airbag system. Features include:
Weight Sensors
This is a new sensor for the passenger seat to classify the weight and todetermine what type of occupant is in the seat, i.e. adult or child.
Infrared Occupant detection
This system will use infrared beams (just like in your TV remote control) todetect the distance the passenger is from the airbag and adapt the force of deployment accordingly.
Capacitive Reflective Occupant Sensing
These sensors will be located in the seat backs and in the dash to identifythe distance you and or your passengers are from the dashboard. Thesesensors will be able to discriminate between a human occupant andinanimate objects like your groceries. This alone will save thousands of dollars in the cases where the driver is the only occupant in the front seat
.
Updated sensors
15
The updated sensors will have the capabilities of deploying the seatbeltpretensioners faster, so in a crash situation you will be in the best position tobenefit from the airbag deployment.
Centralized electronic Control Unit
The new control units will be able to use all the input from the new sensortechnology and through new software deploys what you need when youneed it.
Prototype of a Smart Air bag
The Prototype smart air bag creates a weak electric field. Antennae locatedunder fabric or in the seat cushion measure the field and instantly updatethe airbag controller about the size and position of the occupant.When you are involved in a frontal collision somewhere in theneighborhood of at least 20 kmph, a number of things happen very quickly.The sudden deceleration of you vehicle causes 2 sensors to send anelectrical signal; to the diagnostic module. The diagnostic module self teststo confirm that a crash event is taking place, and then it allows the signal totrigger the airbag deployment.
Above is an illustration of a driver side airbag deployment. The first image isthe airbag inflation, the second depicts your contact with the airbag, and thethird is your coming to rest in the seat and the deflation of the airbag. Thisall takes place in about 30 milliseconds.In fact the entire inflation/deflation cycle takes less than ½ second. Thespeed of the airbag inflating is around 320 kmph. The vehicle hasn’t cometo a stop at this point, nor hopefully have you lost control of it.1988 is the first model for depowered bags. Unfortunately these are notstandard equipment on all cars.
Driver’s Side Airbag
The image below shows the parts of the airbag module in the steering wheel.From top to bottom we have the cover, the airbag assembly, the retainerattached to the steering wheel, the steering wheel and the clock spring.The Clock spring allows the steering wheel to move while maintaining theelectrical connection to the airbag module.
Passenger Airbag
The Passenger bag is mounted in the top of the dash on the passenger sideof the vehicle.
Airbag Checks
When you get in your vehicle and turn the key, look at the dash to find yourairbag or SRS light.It should come on for 7-10 seconds and then go out. This tells you all is wellwith the airbag system.
If the light does not come on, have it checked. After all, it could justbe a burnt out Light bulb
If the light does not go off after this period (usually 7-10 seconds)there is a problem
If the Light comes on while you are driving, it also needs attention.In addition to the front airbags, the car companies are putting airbags inthe doors for side impacts that are not covered by the primary airbags.They are putting them in the seats for the drivers and rear passengers aswell. This increases the cost6 as well as the complexity of the systems.Since 1990 the National Highway Traffic Safety Administration, which isresponsible for the Vehicle safety rules and statistics relating to vehicles,found that of 19 drivers killed by airbags, only five of them were wearingseat belts and two of them were determined to be unconscious before theairbag deployed.
18
Depowered Airbags
Starting with the 1997 model year some automobiles will be available withdepowered Airbag modules.
Inflators
Inflators are undergoing redesign toward a hybrid design using argon gasand non-adized initiators
9.DISARMING THE AIRBAG
Steps in disarming
Disconnect the battery
Wait 30 seconds. The air Bag is equipped with a capacitor and it’simportant to make sure that it is completely discharges before continuing.Change the oil while waiting
Remove the airbag fuse. The fuse Box is below the driver’s left knee; itfolds down by squeezing on a couple of tabs near the top of the box.Fuse also checks the diagram on the fuse box lid before pulling the wrongone.
Drop the sound insulator panel. This is a plastic panel underneath thesteering column. It goes: steering column; interior colored panel; blackcolored panel. The black panel is the one to remove. There are twoscrews along the top and two finger-wing nuts along the back (one nearthe accelerator and one behind the emergency brake.)
Fastened to the sound insulator panel is a yellow circuit. This is theairbag circuit. To disconnect the circuit, you’ll first have to remove agreen connector Positive Assurance lock which is for safety catch. Boththe green catch and the yellow connector are had to pull apart, but heyeventually will give.
Thus the bag is disarmed. The only problems is, now the airbag light willbe on all the time. The airbag is fastened to the steering wheel with fourTorx screws (T-30), accessible from the behind the wheel. They won’tcome all the way out they’re retained. Once you have them all loose, theairbag will try to fall out. The airbag is till connected by one or two wires.The yellow one is the airbag circuit again; it is unplugged the same wayas before, except this time the safety catch is blue.
Do not store it anyplace, which gets hotter than 130 degrees; do not heatit or apply electricity (even static).
19
10.CONCLUSION
The air bags are of greater importance in today’s vehicles since safety of human life is of prior importance. Since the count of automobiles isincreasing tremendously on our roads, the probability of accidents is alsomore. So far a safe riding and for saving the precious life the safety bagsmust be implemented. Today it is the prevail age of the high class peoplewho own high priced cars. Let’s hope every automobile manufacturerimplement the same since safety for life is inevitable
1.INTRODUCTION
For years, the trusty seat belt provided the sole form of passive restraint inour cars. There were debated about their safety, especially relating tochildren. But over time, mush of the country adopted mandatory seat-beltlaws. Statistics have shown that the use of seat belts has saved thousandsof lives that might have been lost in collisions.Air Bags have been under development for many years. The attractionof a soft pillow to land against in a crash must be very strong – the firstpatent on an inflatable crash-landing device for airplanes was filed duringWorld War II. In the 1980’s the first commercial air bags appeared inautomobiles.Since 1988, all new cars have been required to have air bags on bothdriver and passenger sides (Light Trucks came under the rule in 1999). Todate, Statistics show that air bags reduce the risk of dying in a direct frontalcrash by 30 percent. Newer than steering Wheel mounted or Dashboard-mounted bags, but not so widely used, are seat-mounted and door mountedside air-bags. Some experts say that within the next few years, our cars willgo from having dual air bags top having six or even eight air bags. Havingevoked some of the controversy that surrounded seat-belt use in its earlyyears, air bags are the subject of serious government and industry researchand tests.
2. THE BASICS OF AIR BAGS
Before looking at specifics, let’s review our knowledge of the laws of themotion. First, we know that moving objects have momentum (the product of the mass and velocity of an object. Unless an outside force acts on anobject, the object will continue to move its present speed and direction.Cars consist of several objects, including the vehicle itself, Loose objects inthe car and, of course, passengers. If these objects are not restrained, theywill continue moving at whatever speed the car is traveling at, even if thecar is stopped by a collision.Stopping an object’s momentum requires force acting over a period of time. When a car crashes, the force required to stop an object is very greatbecause the car’s momentum has changed instantly while the passengers’ has not much time to work with. The goal of any supplemental restraintsystem is to help stop the passenger while doing as little damage to him orher as possible.What an air bag wants to do is to slow the passengers’ speed to zerowith little or no damage. The constraints that it has to work within arehuge. The air bag has the space between the passenger and the steeringwheel or dashboard and a fraction of a second to work with. Even that tinyamount of space and time is valuable, however, if the system can slow thepassenger evenly rather than forcing an abrupt halt to his or her motion.
3. DEVELOPMENT OF AIR BAGS
The idea of using a rapidly inflating cushion to prevent crash injuries has along history. The first patent on an inflatable crash-landing device forairplanes was filed during World War II.Early efforts to adapt the air bag for use in cars bumped up againstprohibitive prices and technical hurdles involving the storage and release of compressed gas.
•
If there was enough room in a car for a gas canister.
•
Whether the gas would remain contained at high pressure for thelife of the car.
•
How the bag could be made to expand quickly and reliably at avariety of operating temperatures and without emitting an ear-splittingbang.They needed a way to set off a chemical reaction that would produce thenitrogen that would inflate the bag. Small solid-propellant inflators came torescue in the 1970’s.In the early days of auto air bags, experts cautioned that the new devicewas to be used in tandem with the seat belt. Seat belts were still completelynecessary because airbags worked only in front-end collisions occurring atmore than 6 Kmph. Only Seat belts could help in side swipes and crashes(Although side-mounted air bags are becoming more common now), rearend collisions and secondary impacts. Even as the technology advances, airbags still are only effective when used with a lap/Shoulder seat belt.
4.MAIN PARTS OF AIR BAG
There are three parts to an air bag that help to accomplish this feat:1.Bag2.Sensor3.Inflation system
BAG
The bag itself is made of a thin, nylon fabric, which is folded into thesteering wheel or dashboard or, more recently, the seat or door. Thepowdery substance released from their sir bag, by the way, is regular
cornstarch or talcum powder, which is used by the air bag manufacturers tokeep the bags pliable and lubricated while they’re in storage.
SENSOR
The sensor is the device that tells the bag to inflate. It works with thecontrol module to discriminate between crash and non-crash events. Thesesensors measure the severity of the impact. Inflation happens when there isa collision force equal to running into a brick wall at 16 to 24 Km per hour.They are setup so that sudden negative acceleration will cause the contactsto close, telling the control module that a crash before airbag deployment.
INFLATION SYSTEM
The air bag’s inflation system reacts sodium azide(NaN3) with potassiumnitrate (KNO3) to produce large volume of nitrogen gas. Hot Blasts of thenitrogen inflate the air bag from its storage site up to 322Kmph. A Secondlater, the gas quickly dissipates through a tiny holes in the bag, thusdeflating the bag so you can move.
CONSTRUCTION OF AIR BAGS
Airbag are assemblies consisting of the airbag (made of Nylon), inflatormodules and sensor housing, electrical connectors (Clock spring), airbagretainer and the cover. The driver’s side bag is mounted in the center of thesteering wheel.
5.SENSOR TYPES
Ball and Magnet Type Sensor
Spring and Roller type
By function, there are 2 types- Impact sensors and safing sensors. TheForward sensors are located in various locations forward of the passengercompartment. Some are located inside the fenders, some are on the cowl,and some are attached to the core support in front of the radiator.
Rear Sensors are also known as safing sensors as their functions is todetermine that a crash has occurred. Rear safing sensors are located invarious locations in the passenger compartment depending on themanufacturer. Some are integrated with the control/Diagnostic Module.The Rear safing sensor must close before the forward sensors to avoidairbag deployment in cases where the impact is not severe enough to causedeployment. When the vehicle is parked with ignition off deployment is veryunlikely because there is no power to the circuits for deployment this meansthat someone can hit your car and sound the alarm but not deploy theairbags.
nflator Assembly
This is a diagram of a typical inflator assembly behind the steering wheel.
When the control Module activates the airbag assembly, an electriccurrent is sent to the detonator, which ignites the sodium azidepellets.When it burns, it releases nitrogen gas very quickly and in large quantities.This is what inflates the airbag.
Sodium Azide
Sodium Azide is Rocket fuel. Sodium azide is a solid propellant with a veryhigh gas generation ratio. It is very stable in this application.When Sodium azide burns, its major product is nitrogen gas, which makesup around 78% of the Earth’s atmosphere. One of the other by-products issodium hydroxide. This is commonly known as Lye, which is a causticcompound. The quantities produced are very small and present a very smallrisk of burns. The white powder residue seen after inflation is commoncornstarch, used as lubricant for expansion of the airbag. Testing isunderway with inflators that release argon gas.
6.WORKING OF AIR BAGS
Air Bags are designed to inflate in frontal or frontal-angle impacts in whichthe car strikes an immovable object at more than about 16 Kilometers perhour or another car at twice that speed. After a collision, sensors sense anelectric current to an igniter system or, in some cases, to the computerizedcontrol unit. This unit evaluates the situation and then sends an electricalimpulse to the igniter system. The electric current heats a filament (wire),which then ignites a capsule. The Ignited capsule supplies the heat to ignitegas-generating pellets. In most systems, the pellets are made of sodiumazide and produce nitrogen gas when they burn. In other systems,pressurized argon gas is used instead. The gas then expands quickly andinflates the airbag, which then breaks through a plastic cover in the steeringwheel or, the dashboard on the passenger side. The whole process takesabout 0.1 second from the exact moment the crash is detected. The air bagstarts to deflate immediately, venting the harmless gas through holes in theback of the bag of the through the fabric itself.
7.MODERN TYPES OF AIR BAGS
1.Curtain Airbags
Curtain airbags are airbags that inflate in front of vehicle windows to providepassengers better head and neck protection. The curtain airbags are part of new rollover protection system. Most equipped cars will have verticallyinflating curtain airbags in the headliner trim just above the windows, whilesome will have them inflate horizontally from the side pillar between thedoors. In some cases, curtain airbags will deploy in a fraction of a second.Sensors in the side pillar will measure the force of side-impact Collisions. If the sensors measure a strong impact, then the curtain airbags will deploy ina fraction of a second. The curtain airbag will drop straight down over the
13
windows to keep the occupants’ heads from striking the window or theintruding nose of another vehicle.
The system will use sensors that measure tipping rather than impact.These sensors send information to a central module, which will determine if the vehicle is beginning to roll over. If the vehicle is tipping into a roll, thesensors will deploy the curtain airbag. Stored in the headliner above thedoors, the cells of the inflatable curtains are inflated in less than 25thousands of a second in a triggering accident. To avoid stitches from sewingthe bag, its cells are woven on the loom directly from the yarn usingAutoliv’s one piece-weaving technology. Therefore the bag can remaininflated for several seconds, which is imperative in roll-over accidents. Coolgas will keep it inflated for up to six seconds.Laboratory tests have shown that the so-called Head Injury Criterion(HIC) can be reduced by approximately 80%. The Inflatable Curtain wasdeveloped in cooperation with Mercedes and Volvo.Car manufacturers selling car with these as standard equipment are
Alfa Romeo, Audi, BMW and Volvo.
2. Head-Thorax Bag
The Head-Thorax Side-Impact Airbag has an extension from the regularThorax Bag that protects the head. It was introduced in 1998 and developedin cooperation with Ford and Renault.
3. Inflatable Tubular Structure (ITS)
The Inflatable Tubular Structure (ITS), the world’s first airbag for headprotection, was introduced on BMW cars. It consists of a unique nylon tube,installed in the head-liner above the frontal doors that inflates to a diameterof about 15 centimeters (5 inches).
8.FUTURE OF AIR BAGS
Smart Systems
The smart airbag of the future is not just the airbag, but also a redesign of the components in the current airbag system. Features include:
Weight Sensors
This is a new sensor for the passenger seat to classify the weight and todetermine what type of occupant is in the seat, i.e. adult or child.
Infrared Occupant detection
This system will use infrared beams (just like in your TV remote control) todetect the distance the passenger is from the airbag and adapt the force of deployment accordingly.
Capacitive Reflective Occupant Sensing
These sensors will be located in the seat backs and in the dash to identifythe distance you and or your passengers are from the dashboard. Thesesensors will be able to discriminate between a human occupant andinanimate objects like your groceries. This alone will save thousands of dollars in the cases where the driver is the only occupant in the front seat
.
Updated sensors
15
The updated sensors will have the capabilities of deploying the seatbeltpretensioners faster, so in a crash situation you will be in the best position tobenefit from the airbag deployment.
Centralized electronic Control Unit
The new control units will be able to use all the input from the new sensortechnology and through new software deploys what you need when youneed it.
Prototype of a Smart Air bag
The Prototype smart air bag creates a weak electric field. Antennae locatedunder fabric or in the seat cushion measure the field and instantly updatethe airbag controller about the size and position of the occupant.When you are involved in a frontal collision somewhere in theneighborhood of at least 20 kmph, a number of things happen very quickly.The sudden deceleration of you vehicle causes 2 sensors to send anelectrical signal; to the diagnostic module. The diagnostic module self teststo confirm that a crash event is taking place, and then it allows the signal totrigger the airbag deployment.
Above is an illustration of a driver side airbag deployment. The first image isthe airbag inflation, the second depicts your contact with the airbag, and thethird is your coming to rest in the seat and the deflation of the airbag. Thisall takes place in about 30 milliseconds.In fact the entire inflation/deflation cycle takes less than ½ second. Thespeed of the airbag inflating is around 320 kmph. The vehicle hasn’t cometo a stop at this point, nor hopefully have you lost control of it.1988 is the first model for depowered bags. Unfortunately these are notstandard equipment on all cars.
Driver’s Side Airbag
The image below shows the parts of the airbag module in the steering wheel.From top to bottom we have the cover, the airbag assembly, the retainerattached to the steering wheel, the steering wheel and the clock spring.The Clock spring allows the steering wheel to move while maintaining theelectrical connection to the airbag module.
Passenger Airbag
The Passenger bag is mounted in the top of the dash on the passenger sideof the vehicle.
Airbag Checks
When you get in your vehicle and turn the key, look at the dash to find yourairbag or SRS light.It should come on for 7-10 seconds and then go out. This tells you all is wellwith the airbag system.
If the light does not come on, have it checked. After all, it could justbe a burnt out Light bulb
If the light does not go off after this period (usually 7-10 seconds)there is a problem
If the Light comes on while you are driving, it also needs attention.In addition to the front airbags, the car companies are putting airbags inthe doors for side impacts that are not covered by the primary airbags.They are putting them in the seats for the drivers and rear passengers aswell. This increases the cost6 as well as the complexity of the systems.Since 1990 the National Highway Traffic Safety Administration, which isresponsible for the Vehicle safety rules and statistics relating to vehicles,found that of 19 drivers killed by airbags, only five of them were wearingseat belts and two of them were determined to be unconscious before theairbag deployed.
18
Depowered Airbags
Starting with the 1997 model year some automobiles will be available withdepowered Airbag modules.
Inflators
Inflators are undergoing redesign toward a hybrid design using argon gasand non-adized initiators
9.DISARMING THE AIRBAG
Steps in disarming
Disconnect the battery
Wait 30 seconds. The air Bag is equipped with a capacitor and it’simportant to make sure that it is completely discharges before continuing.Change the oil while waiting
Remove the airbag fuse. The fuse Box is below the driver’s left knee; itfolds down by squeezing on a couple of tabs near the top of the box.Fuse also checks the diagram on the fuse box lid before pulling the wrongone.
Drop the sound insulator panel. This is a plastic panel underneath thesteering column. It goes: steering column; interior colored panel; blackcolored panel. The black panel is the one to remove. There are twoscrews along the top and two finger-wing nuts along the back (one nearthe accelerator and one behind the emergency brake.)
Fastened to the sound insulator panel is a yellow circuit. This is theairbag circuit. To disconnect the circuit, you’ll first have to remove agreen connector Positive Assurance lock which is for safety catch. Boththe green catch and the yellow connector are had to pull apart, but heyeventually will give.
Thus the bag is disarmed. The only problems is, now the airbag light willbe on all the time. The airbag is fastened to the steering wheel with fourTorx screws (T-30), accessible from the behind the wheel. They won’tcome all the way out they’re retained. Once you have them all loose, theairbag will try to fall out. The airbag is till connected by one or two wires.The yellow one is the airbag circuit again; it is unplugged the same wayas before, except this time the safety catch is blue.
Do not store it anyplace, which gets hotter than 130 degrees; do not heatit or apply electricity (even static).
19
10.CONCLUSION
The air bags are of greater importance in today’s vehicles since safety of human life is of prior importance. Since the count of automobiles isincreasing tremendously on our roads, the probability of accidents is alsomore. So far a safe riding and for saving the precious life the safety bagsmust be implemented. Today it is the prevail age of the high class peoplewho own high priced cars. Let’s hope every automobile manufacturerimplement the same since safety for life is inevitable