Inflator/Gas Generator

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Sydney Whitehead
7 years ago
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Due to high costs and limited effectiveness, the airbags disappeared temporarily. The name 'Airbag' is often misinterpreted as air bag. 'Air' stands for 'Automotive Inflatable Restraint'.

1 Advanced Extrication Tech s Airbag Basics The first airbag for passenger cars was invented and developed by an American named John Hetrick. The airbag was further developed in America during the seventies and was experimentally installed to replace the seatbelts. Due to high costs and limited effectiveness, the airbags disappeared temporarily. The name 'Airbag' is often misinterpreted as air bag. 'Air' stands for 'Automotive Inflatable Restraint'. The bag is made of nylon and is filled with Nitrogen or Argon instead of normal atmospheric air. During the eighties, the useful effect of the airbag was rediscovered. Airbags were no longer used to replace the seatbelts, but to increase the safety of the occupants. The term 'Supplemental Restraint System' (SRS) came to life: airbags as safety devices in addition to the seatbelts. At the beginning of the nineties, airbags became more and more common. Airbags were mounted in cars as part of the standard package. The development of the airbags went faster and faster. During the mid-nineties the first side-airbag was introduced and at the end of the nineties the first head airbag was optional. Today, protection methods for pedestrians are developed in addition to the development of techniques for protection of the occupants. With this application of airbags, the pedestrians have an increased survival rate. Nowadays, virtually all passenger cars, light trucks and trucks and even motorbikes are equipped with airbags. A common airbag unit consists of 3 main parts: the gas generator, the ignition, and the airbag itself. These components are explained in detail in the following section: Inflator/Gas Generator The basis for the fast deployment of airbags is an inflator, which can produce the necessary gas for the inflation of the airbag quickly enough. There are basically two different types of inflators. The first type, a pyrotechnic inflator, uses a solid propellant (usually sodium azide) that is ignited, Solid fuel gas generator after which the high-speed chemical reaction produces a large volume of nitrogen gas that fills the airbag. The second type uses gas (normally a mixture of inert gases) that is stored in a pressurized cartridge under a pressure between 200 and 700 bar. The cartridge is opened by a small pyrotechnic charge after which the gas is released into the airbag. Crushing these inflators is the second potential danger

The ignition component ignites the High Pressure Cylinder in C-pillar pyrotechnic charge of the gas inflator or releases the gas in the case of a high-pressure gas cartridge via an electrical signal

2 when dealing with airbags. First of all, the solid propellant can be health threatening when exposed. Secondary, cutting a pressurized inflator can result in flying parts or deployment of the attached airbag. Ignition element The airbag is activated using the ignition component. The ignition component ignites the High Pressure Cylinder in C-pillar pyrotechnic charge of the gas inflator or releases the gas in the case of a high-pressure gas cartridge via an electrical signal from the SRS unit. Air cushion (airbag) The airbag is folded behind a cover plate. When the ignition device receives the electrical signal from the SRS unit, the gas inflator will be activated to deploy the airbag. The deployment of these safety devices is extremely fast; an airbag needs around 0,015 seconds to deploy, much faster than the blink of an eye and with tremendous speed and force. Recognition Un-deployed frontal airbags can usually be identified by an airbag logo that is normally stamped or placed directly on the steering wheel and on the dashboard area on the passenger's side. Airbag logos normally use the word 'airbag' or abbreviations such as 'SRS' (for 'Supplemental Restraint System'), 'SRP' or something similar. Frontal collision airbags Airbags in the steering wheel and on the dashboard on the passenger's side protect the occupants in frontal / half-frontal collisions or - better explained - during accidents with a high deceleration in the longitudinal axis of the vehicle. In accidents where the deceleration is not high enough the airbag will not deploy.

3 As a supplement for the protection of the driver and passenger airbag, some manufacturers use knee airbags in the area under the steering wheel and similar on the lower area of the dashboard on the passenger s side. Below is a short overview of these types of airbags. Smart frontal airbags Recent vehicle models are equipped with smart frontal airbags that are able to adapt the airbag deployment to the characteristics of the accident, for instance the severity of the crash and the position of the occupant at the moment of impact. In these cases not only the deceleration of the vehicle but even the number and location of occupants configures the airbag deployment. The smart frontal airbags are often combined with an 'occupant detection system', see below. The inflator s for the so-called 'dual stage airbag s or 'dual-threshold airbag s, have two different stages that deploy in a special sequence. In certain scenarios it is possible that only one stage has deployed and a second stage remains standby. Occupant detection systems Occupant detection systems with different sensors in the seat and at the seat rail can detect the weight of the occupant, the position of the seat and sometimes the position of the occupant. Based on the results the airbag is switched OFF (the seat is not occupied), the airbag is filled with a smaller volume of gas (the occupant is sitting close to the airbag) or the airbag is filled with a larger volume of gas (the occupant is normal seated). It is also possible that when a child seat is detected, the deployment of the airbag will be suppressed completely. Mechanical frontal airbags The SRS control unit deploys most of the frontal airbags electrically, but there are also systems that use a mechanical sensor inside the steering wheel for the deployment. These systems are independent of the vehicle's electrical system and are active even after electrical shutdown of the vehicle is accomplished.

Knee airbags are normally deployed in sequence with the corresponding frontal airbag.

4 Knee airbags Knee airbags are designed to protect the knee and leg area of the occupant, especially if the occupant is not using the seatbelt. Depending on the manufacturer knee airbags inflate like normal airbags or in some cases the knee airbags inflates under the dashboard trim. Knee airbags are normally deployed in sequence with the corresponding frontal airbag. Side collision airbags Side and curtain airbags are designed to protect the occupants in severe side impact accidents. In addition to the reinforced side structure of the vehicle, the side airbags establish a soft protection that avoids direct contact with the hard body parts. Normally only the side and curtain airbags on the impact side are deployed. The determining factor for airbag deployment is the lateral acceleration of the vehicle (or sometimes the change of air pressure inside the door). In the following section we will look at side and curtain airbags in detail. Side airbags and are often mounted in convertibles. Side airbags protect the side of the occupant. Side airbags are either mounted inside the door or in the side of the back of the seat. Side airbags are available for first and the second seat row. It is possible that the side airbags are mounted in the side of the back of the seat. Some side airbags are big enough to protect the side and head area of the occupant. These side airbags inflate upwards Mechnical side airbags Early model side airbags are deployed by a mechanical sensor/switch that is activated by the intruding rocker panel. These systems are independent from the electrical system of the vehicle.

Side curtain airbags / Head impact airbag Side curtain airbags are designed to protect the head and shoulder area of the occupant during side collisions.

They are normally inflated over the side windows of the vehicle and (depending on length and design of the airbag) are able to protect the occupants in more than one seat row.

Another possibility is that two inflators are used to deploy a single airbag. Other airbag applications Airbags can be used for many different applications.

5 Side curtain airbags / Head impact airbag Side curtain airbags are designed to protect the head and shoulder area of the occupant during side collisions. Side curtain airbags are usually mounted in the roof rail under the roof trim. They are normally inflated over the side windows of the vehicle and (depending on length and design of the airbag) are able to protect the occupants in more than one seat row. Depending on the manufacturer is it possible that multiple head impact airbags on one side of the vehicle are mounted, for instance one for the first seat row and one for the second seat row. Another possibility is that two inflators are used to deploy a single airbag. Other airbag applications Airbags can be used for many different applications. A lot of experiments are carried out to further increase the safety for occupants. Examples of new developments are airbags for use in the seatbelt, frontal airbags for backseat occupants, anti-submarining airbags for backseat occupants and airbags for the feet area. Most of these airbags are still under development and are not used in a series-vehicle today. Below are some examples of new airbag types that are available in some of today's vehicles. Anti-submarining airbag Some car manufacturers are using anti-submarining-airbags. These airbags prevent occupants from sliding forward from under the seatbelt. When this airbag inflates, the front of the seat cushion is raised to avoid 'submarining' (occupant diving/slipping under the lap part of the seatbelt). Pedestrian protection Airbags are also used to increase the protection of pedestrians. These airbags are used to lift the engine hood, so that a pedestrian has a softer landing on the engine hood.

Airbags and Pretensioners. Emergency Response Guide

Airbags and Pretensioners. Emergency Response Guide Airbags and Pretensioners Emergency Response Guide 1 This guide specifically addresses Airbags and Pretensioners in GM Vehicles. We will provide information on vehicles equipped with frontal, door mounted,