Airbags & seat belts

Airbags & seat belts

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  Airbags & SeatBelts ANUDEEP KAMEPALLI CB.EN.P2AEL20003
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  INTRODUCTION  For years,the trusty seat belt provided the sole form of passive restraint in our cars.  Statistics have shown that the use of seat belts has saved thousands of lives that might have been lost in collisions. Air Bags have been under development for many years. The attraction of a soft pillow to land against in a crash must be very strong.  In the 1980’s the first commercial air bags appeared in automobiles. Since 1988, all new cars have been required to have air bags on both driver and passenger sides (Light Trucks came under the rule in 1999). To date, Statistics show that air bags reduce the risk of dying in a direct frontal crash by 30 percent.  Some experts say that within the next few years, our cars will go from having dual air bags top having six or even eight air bags. Having evoked some of the controversy that surrounded seat-belt use in its early years, air bags are the subject of serious government and industry research and tests.
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  BASICS OF AIRBAGS  When a car crashes, the force required to stop an object is very great because the car’s momentum has changed instantly while the passengers’ has not much time to work with.  The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.  What an air bag wants to do is to slow the passengers’ speed to zero with little or no damage. The constraints that it has to work within are huge. The air bag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with. Even that tiny amount of space and time is valuable, however, if the system can slow the passenger evenly rather than forcing an abrupt halt to his or her motion.
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  MAIN PARTS OFAIR BAG There are three parts to an air bag that help to accomplish this feat: 1. Bag 2. Sensor 3. Inflation system BAG The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door. The powdery substance released from their sir bag, by the way, is regular talcum powder, which is used by the air bag manufacturers to keep the bags pliable and lubricated while they’re in storage.
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  SENSOR The sensor isthe device that tells the bag to inflate. It works with the control module to discriminate between crash and non-crash events. These sensors measure the severity of the impact. Inflation happens when there is a 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 contacts to close, telling the control module that a crash before airbag deployment. INFLATION SYSTEM The air bag’s inflation system reacts sodium azide(NaN3) with potassium nitrate (KNO3) to produce large volume of nitrogen gas. Hot Blasts of the nitrogen inflate the air bag from its storage site up to 322Kmph. A Second later, the gas quickly dissipates through a tiny holes in the bag, thus deflating the bag so you can move.
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  SENSORS By function, thereare 2 types- Impact sensors and safing sensors. The Forward sensors are located in various locations forward of the passenger compartment. 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 to determine that a crash has occurred. Rear safing sensors are located in various locations in the passenger compartment depending on the manufacturer. Some are integrated with the control/Diagnostic Module. The Rear safing sensor must close before the forward sensors to avoid airbag deployment in cases where the impact is not severe enough to cause deployment. When the vehicle is parked with ignition off deployment is very unlikely because there is no power to the circuits for deployment this means that someone can hit your car and sound the alarm but not deploy the airbags.
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  Mass-Type Sensor  Animpact sensor is normally fitted to the front of the vehicle as this is where a collision is likely to occur. The sensor is positioned inside the engine and a similar safety sensor is located inside the passenger zone of the vehicle. This safety sensor is required to measure the intensity of the collision to determine whether the impact is over a certain threshold to justify the release of an airbag.  Inertia sensors work on the principle of detecting a decrease in acceleration of a moving vehicle and generating an electrical impulse as shown in schematic diagram of an inertial sensor.  During a collision with another moving vehicle, the sensing mass is forced forward into the gold-plated contacts as a result of the change in the state of motion. Following the movement of this metal ball into the contacts, this metal mass makes contact with electrical terminals at either side of the metal ball which alerts the central unit of a collision
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  Roller-Type Sensor The roller-typesensor consists of a weight connected to a coil spring component. Like the mass-type sensor, during impact with an oncoming vehicle, the metal weight is forced forward which alters the tension on the coil spring to manipulate the electrical circuit that closes off the sensor contact. It is important to note that the impact and safety sensors must activate and close off at the same time to allow for the deployment of the airbag
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  Inflator Assembly When thecontrol Module activates the airbag assembly, an electric current is sent to the detonator, which ignites the sodium azide pellets. When it burns, it releases nitrogen gas very quickly and in large quantities. This is what inflates the airbag. Sodium Azide is Rocket fuel. Sodium azide is a solid propellant with a very high gas generation ratio. It is very stable in this application. The quantities produced are very small and present a very small risk of burns. The white powder residue seen after inflation is common corn-starch, used as lubricant for expansion of the airbag. Testing is underway with inflators that release argon gas.
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  WORKING  Air Bagsare designed to inflate in frontal or frontal-angle impacts in which the car strikes an immovable object at more than about 16 Kilometers per hour or another car at twice that speed.  After a collision, sensors sense an electric current to an igniter system or, in some cases, to the computerized control unit. This unit evaluates the situation and then sends an electrical impulse to the igniter system. The electric current heats a filament (wire), which then ignites a capsule.  The Ignited capsule supplies the heat to ignite gas-generating pellets. In most systems, the pellets are made of sodium azide and produce nitrogen gas when they burn. In other systems, pressurized argon gas is used instead.  The gas then expands quickly and inflates the airbag, which then breaks through a plastic cover in the steering wheel or, the dashboard on the passenger side. The whole process takes about 0.1 second from the exact moment the crash is detected.  The air bag starts to deflate immediately, venting the harmless gas through holes in the back of the bag of the through the fabric itself.
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  TYPES OF AIRBAGS Fewtypes of airbags: FRONTAL AIRBAGS SIDE AIRBAGS (SABS) REAR AIRBAGS KNEE AIRBAGS INFLATABLE SEAT BELTS SEATBELT MOTORCYCLE
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   Frontal -Frontal airbags have been standard equipment in all passenger cars since model year 1998 and in all SUVs, pickups and vans since model year 1999. These airbags are mounted on the steering wheel to offer protection for the driver and on the dash to protect the passenger. Many new cars have a weight sensor for the front passenger seat that will prevent the airbag from deploying if a small child is sitting there. For older cars without a weight sensor, the airbag's force can cause injury in younger children, so the government suggests that children under 13 should ride in the back seat.  Side - Side airbags include curtain and torso bags. Torso bags are usually situated in the seat and were placed there in order to reduce abdominal and pelvic injuries. Curtain airbags began being offered in the late 1990s and were the first door-mounted airbags. These types of airbags reduce the risk of head injuries during side-impact crashes and some even have rollover sensors that will detect if a vehicle begins to roll after a collision.  Knee - These airbags are usually situated underneath the steering wheel and glove compartment and can protect a driver or passenger from suffering knee injuries such as bruising or breaking a bone.  Rear - Includes rear-center and rear-window airbags which can prevent backseat passengers from colliding with one another and from the back window during a rear-end collision.
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   Knee Airbags Sincethe early 2000s, many vehicle manufacturers now include knee airbags, which are usually mounted under the steering wheel and deploy from under the dashboard, stopping front seat occupants' knees from hitting the hard surface. This can prevent kneecaps from shattering, which is a common injury in high-speed frontal collisions.  Inflatable Seat Belts The inflatable seat belt is only available in select models. While it gets categorized as an airbag, the inflatable seat belt really isn’t really an airbag, it merely functions like one by deploying in an accident. Most airbags cushion passengers, but the inflatable seat belt instead helps spread an accident's force over a wider area on a person's body. The result is that the accident doesn't feel as severe, since the force isn't as highly concentrated.  Motorcycle Introduced in the mid-2000s, these types of airbags are only available in some types of motorcycles and are believed to lessen the energy of the cyclist moving forward and reduce the velocity they may be thrown at from the motorcycle.
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  Airbag Injuries Although moreand more airbags have begun being implemented in vehicles in an effort to reduce the number of injuries people may suffer during a car collision, it could lead to more people suffering serious airbag injuries. Some common types of airbag injuries include: Burns Skin Abrasions Rashes Bruising Facial Injuries Damage to the Eyes Most airbag injuries are caused by the sudden inflation of the bag and the chemicals used to deploy the airbag. According to the National Highway Traffic Safety Administration, airbags have been the cause of more than 170 fatalities in the United States since 1990.Injuries from airbags may be reduced by providing adequate room between yourself and the area of deployment.
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  Airbag Checks When youget in your vehicle and turn the key, look at the dash to find your airbag or SRS light.  It should come on for 7-10 seconds and then go out. This tells you all is well with the airbag system.  If the light does not come on, have it checked. After all, it could just be 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.
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  Seat-Belts  An impactbetween two cars will cause their velocities to change suddenly. Occupants within the cars will continue to move at pre-impact speeds until they experience a force to accelerate them to the new speed of the car. For occupants who are not wearing a seatbelt, this force often occurs as they crash into the steering wheel, dashboard, and/or windshield. A seatbelt is designed to tie the occupant to the vehicle and slow the occupant at the same rate as the vehicle. Seatbelts apply collision forces to areas of the body that are able to withstand these forces without serious injury.  When paired with a properly worn seatbelt, airbags reduce the risk of sustaining fatal injuries in the event of a crash  Early seatbelts were lap-only straps that were difficult to adjust. Although they were effective in preventing occupants from being thrown out of cars, they did little to restrain the torso and head in the event of a crash. The introduction of lap and torso belts provided a significant improvement in preventing head injuries in frontal impacts.  One of the key safety features in the lap and torso belt is the locking retractor. The basic function of the retractor is to allow the shoulder portion of the seatbelt to spool out and retract.