For many years, the seat belt has protected passengers and the driver in accidents. But modern technologies and the automotive industry are developing, there is a need for more effective protection. With the advent of airbags, we can talk about reliable protection of people inside the car. In the event of an accident, the airbag inflates in just a split second. It is able to protect the body and head from injury.
Airbag reliability
Crash tests show how much modern models cars are safe. If there are no airbags in the car, the driver and passengers risk their health and lives. More reliable protection is provided by the presence of at least two front airbags. In this regard, there were cases when a driver was injured from being hit by an airbag, and not in an accident. This arose as a result incorrect adjustment. The airbag is fired at a speed of more than 300 km/h. This is a powerful blow. If it does not work correctly, the driver may suffer head injuries. And yet, during their existence, they have saved many people and cases of malfunctions are rare.
How does an airbag work?
The airbag is far from a simple device and is divided into main elements: a sensitive sensor, a system that inflates the airbag and, accordingly, the airbag. It is made of nylon and when given a sharp push with air, it inflates. It is installed in the car under plastic sheathing. The sensor is sensitive, it is he who releases the pillow. It is usually configured so that the airbag fires at low speed during an accident. For a quick shot of the pillow and inflating it special composition answers complex device. This is a pillow pumping system that includes electronic and chemical components. We will not consider electronics here, but the chemistry in the airbag is a subject of our interest.
When designing an airbag, the inventors had to solve the following problem. If a car crashes into high speed into any object, the sensor reacts in connection with the load. The trigger device detects this and gives a signal for instant flight and inflation of the pillow.
At first, they tried to install gas cylinders in the car interior, which, upon impact, mechanically sent their contents into the airbag. But such solutions were too unsafe, cumbersome and slow. Inventors had to try many options before chemistry came to the rescue in 1970, which made it possible to turn the airbag into a safe and reliable means of protection!
The inflation system contains containers with sodium azide (NaN 3) and potassium nitrate (KNO 3). In the event of an accident, electronic impact sensors initiate ignition of the solid propellant charge, which triggers a chemical reaction that results in the formation of a large volume of nitrogen. The reaction is so rapid (the total time from the start of the fuse burning to the completion of the reaction is about 50 milliseconds) that the pillow breaks out of its seat at a speed of 300 km/h! After filling the pillow with gas, it is immediately released through special holes. This is done for safety reasons, because if you do not deflate the pillow, a person can be tightly pinned in the cabin! When deflating the airbags, you can observe a slight “smoke” in the cabin - this is nitrogen coming out.
Types of airbags
The standard option is two front airbags, which are equipped with most cars. But models with six different pillows are currently being manufactured.
There are two front airbags. They protect the driver and front passenger. There are also side airbags that can protect not only the body of passengers, but also the legs. Together with them, special curtains prevent head injuries in a side impact. Manufacturers also took care of protecting the legs and created a cushion that has proven itself in crash tests and minimized injuries.
The latest development is a pillow located in the center. It protects passengers from impacts in the cabin. Another pillow is installed on the belt, which can protect the chest area. Some modern models are equipped with such innovations. But this is not yet widespread.
To sum it up: an airbag saves lives in an accident. But you must remember to fasten your seat belts.
Safety in a new car is an integral part, not an option. More and more new types of systems and technologies are being developed. Let's consider the principle of operation, type and design of airbags.
Contents of the article:
An airbag is now much more often in demand as an option than, for example, an air conditioner or a modern audio system. The main purpose of airbags (in cars referred to as airbags) is considered to be to soften the impact of passengers and the driver on the steering wheel, other parts of the body, and windows. As a rule, it is used with seat belts. The security system was first introduced in 1953 when Walter Linderer published his patent.
Types of car airbags
As a rule, modern cars have several airbags. Previously, only a driver's airbag was installed, but later they added one for the front passenger. In current models they are installed around the entire perimeter, in different places of the cabin. Pillows are divided by type depending on their location. The first are the front airbags, followed by the side airbags, head airbags, center airbag, knee airbag and pedestrian airbag. The latter option is installed externally, between the hood and the windshield.
Frontal
They were first used on Mercedes-Benz cars in 1981. As a rule, these are front airbags for the driver and passenger. In turn, the passenger can be turned off at will. Often in modern cars, the design provides for two-stage or multi-stage operation. It all depends on the complexity of the accident (usually adaptive airbags). According to all the rules, the driver's airbag is installed in the steering wheel, for the front passenger - in the upper part of the front panel.
Side airbags
The main purpose of side airbags is considered to be to reduce the risk of injury to the pelvis, chest and abdominal cavity. As a rule, a side impact is one of the most unpredictable and painful. Volvo first used side airbags on its cars in 1994. This type of pillows was installed as an optional option to the main front ones.
Typically, the location of the side airbags is considered to be the back of the front seat. Although in modern cars you can also find them in the backs of the rear seats. Airbags with a two-chamber design are considered the highest quality. Their lower part is more rigid to protect the pelvis, and upper part soft to protect the chest.
Curtains or head pillows
Judging by the name, their main purpose is clear. In the list of car manufacturers they are also listed as curtains. In the event of a side impact, the curtains will protect your head from hitting the door glass. The very first this technology used by Toyota in 1998.
Depending on the model of the car, it can be located in the front part of the roof, also between the pillars and on the rear part of the roof of the cabin. Protection is provided for front and rear passengers.
Knee
The name itself speaks volumes about its purpose; protecting the knees and shins from injury is very important in the event of a collision. Often located under the steering wheel. They were first installed on Kia cars in 1996. In addition to the driver's, they are also installed for the front passenger, under the glove compartment.
Central defense
Since 2009, Toyota cars have had a central airbag. The main purpose is to reduce the secondary impact of passengers in side collisions. Often located in the armrest between the front row of seats. For the rear row of seats, it is located in the central part of the backrest.
In modern cars, except Toyota, the same ones are used in Mercedes-Benz cars (second generation Pre-Safe safety system). Thus, in the event of a side impact, this airbag softens the return impact of the passenger.
Pedestrian airbag
Since 2012, Volvo began introducing pedestrian airbags into its cars. Unlike all the above options, this type It is located outside the car, between the windshield and the hood. Thus, if a driver hits a pedestrian, the airbag softens the blow and prevents serious injuries.
Mechanism design
The device looks like a soft shell and is filled with gas at the right moment; the set also includes a gas generator and a control system. The pillow itself is made of nylon fabric; in order to lubricate the pillow and not break during operation, talc or starch is used. They can often be seen in the air during airbag deployment.
The main purpose of the gas generator is to fill the pillow itself with gas. Thus, this is already an airbag module. Gas generators differ from each other in shape (tubular and round), in the nature of operation (with two-stage and single-stage operation) and in the method of gas formation (hybrid and solid fuel).
The most common is solid fuel; it consists of a housing, a squib and a certain charge. solid fuel. Typically, the fuel is ignited by a squib, resulting in nitrogen gas.
A hybrid gas generator consists of a squib, a gas charge under high pressure argon or compressed nitrogen, housing and solid fuel charge. The filling of the pillow itself occurs with compressed gas, as a result of pushing out a charge from solid fuel.
The airbag control system includes traditional shock sensors, a central control unit and an actuator (gas generator squib).
Operating principle
The main start for activation is a blow. Depending on which part and what strength of the blow, only the right pillows security. As soon as an impact occurs, the impact sensors are activated, then information about the force and location of the impact is transmitted to the central control unit. The unit processes the received data and determines the need to deploy specific airbags, as well as their time and strength.
In parallel with the airbags, information is transmitted to other sensors and systems, for example, an emergency braking system or an SOS signal. If the impact force is not significant, then only the seat belts can work, or they can also work in conjunction with airbags.
Paired with a signal on different systems, a signal is sent to the gas generator of the relevant airbags. On average, the response time of the airbags is about 40 ms. Thanks to the gas generator, the pillows are deployed and inflated. As soon as the pillow comes into contact with a person and has worked, it ruptures and deflates.
All cars always use disposable airbags. If a fire occurs in the cabin and the temperature reaches 150-200 °C, then the airbags are automatically deployed.
Conditions for triggering
The main conditions for triggering front airbags security can be considered:
- exceeding the impact threshold (force) in a frontal collision;
- a sudden collision with a hard part at high speed (curb, sidewalk, pit wall, etc.);
- landing firmly after a car jump;
- car crash;
- an oblique or direct blow to the front of the car.
Video about how airbags work:
This is the author’s translation, with comments from Russian practice, of the article “ Air Bag Deployment Criteria", published in 2014 by Kenneth Solomon and Jesse Kendall in The Forensic Examiner®, the official peer-reviewed academic journal of the American College of Forensic Examiners, which has gained popularity and recognition as the leading forensic journal in the world.
And since our people in the bakery by taxi don’t read such magazines, this article on Pravoruba will be useful to both road accident lawyers and auto experts who read it. For lawyers - as information for interrogating in court auto experts who do not read in order to explain to them their empty conclusions, and for auto experts who read - in order not to give conclusions based on shamanic rituals.
Introduction
Airbag control modules use sophisticated algorithms to make deployment decisions based on an assessment of the severity of the crash associated with changes in vehicle speed or deceleration over time. Due to the fact that the control algorithms are manufacturer know-how, their actual speed, acceleration, or deformation (path) thresholds for airbag deployment in a crash are not known. Car manufacturers do not disclose the values of these parameters and algorithms, limiting themselves to declarative “strong impact” or “impact of sufficient force” in the owners’ manuals, and dealers simply do not know them, while performing performances in front of clients with testing instrument control modules.Indeed, such vague non-technical criteria create dead-end situations when bringing legal claims from car owners whose airbags did not deploy in an accident, or deployed arbitrarily without visible reasons. This also creates favorable soil for fraudulent staging of road accidents, which consists of “transferring” panels with deployed airbags to a practically undeformed car.
However, the values technical parameters required for airbag deployment can be determined by examining the results of laboratory crash tests of specific manufacturers' vehicles.
Objectives of the article
1. Obtain information and understand the operation of the airbag control system and its components.2. Obtaining information and understanding when airbags should or should not deploy. The article contains an introduction to airbag control systems and their deployment processes, a short history shock sensors. Describes the variables used in airbag deployment algorithms and provides comparative examples using several proprietary control systems. A method is shown to estimate the range of speed, deceleration, or deformation (path) that is the threshold for airbag deployment.
Airbag deployment process
The purpose of an airbag is to provide a resilient, soft cushion between the occupants and the vehicle's interior. To achieve this goal, the airbags must be completely filled with gas within a short period of time and before passengers come into contact with them. Rapid airbag deployment has the potential to cause fatal injury to people if they are already in contact with the airbag during deployment. Therefore, airbags must have a control system that can correctly recognize that a collision is occurring. At the same time, it is recognized early enough for the airbag to deploy safely.The airbag deploys after an electrical signal to deploy is sent to the detonator from the airbag control module. This signal initiates a chemical reaction that quickly inflates the nylon fabric air bag with gas. The gas contains dust particles from the material used to lubricate the bag (usually talc and cornstarch). Once the cushion is fully deployed, the gas escapes through small vents. The holes are sized and positioned to reduce the volume of the bag with at different speeds, depending on the type of vehicle.
History of shock sensors
Early airbag deployment systems used mechanical sensors to detect the impact, which were then phased out in the US market around 1994. Sensors such as, for example, " rolamite", contained metal rollers stabilized in the standby position by a spring or magnet.
Upon impact beyond the intended threshold, the spring or magnet could no longer hold the metal mass in place. The mass moved and pressed against the contact, sending an electrical signal to the airbag control module. Mechanical sensor systems tend to be inaccurate in interpreting small collisions. Mechanical sensors may not have enough movement in frontal collisions, causing delayed response. Modern shock sensors are now based on microelectromechanical systems (MEMS).
New impact detection systems
The new MEMS crash sensors measure acceleration with an accelerometer, which sends a continuous stream of data to the airbag control module. Accelerometers are usually piezoelectric or variable capacitive sensors. The most common MEMS accelerometer in use today is the ADXL-50 from Analog Devices.
The author has come across the conclusions of complete idiomatic “unreading” auto experts, in which they establish a malfunction of the shock sensor by visual inspection or organoleptic method. Their logic is limited to the primitive chain “there was a shock - the airbags did not work - which means the shock sensor is not working.” In fact, the testing procedures for such sensors are based on Gauss-Newton type algorithms (not approved by the Ministry of Justice, and, therefore, not recognized by state experts as scientific) and require special software and equipment. Examples of numerous tests can be viewed on YouTube, and if necessary, official testing and calibration regulations can be found on the manufacturer’s website specific model sensor
https://youtu.be/ycThnu3k_vc
As the masses aimed at the elastic elements move relative to the sensor body due to acceleration, special plates attached to the masses move closer to other stationary plates. Changing the distance between the plates affects the sensor's capacitance, or ability to hold electric charge. This change in capacitance is easily measured and then converted into a change in voltage. The change in voltage is directly related to the inertial force due to acceleration, and the reading is interpreted by the airbag control module as acceleration. The control module's algorithm can determine whether airbag deployment is necessary based on its mathematical model of acceleration pulses over time.
Decision making process
The airbag control module (ACM) receives a continuous signal from each MEMS sensor and records data for a specified period after a specific event. By using central processor(CPU) it performs algorithmic calculations and gives or does not give the command to deploy the airbag. Impact severity determination algorithms work by estimating one or more kinematic parameters (acceleration, its derivatives or integrals), a list of which is given in Table 1 below. Examples of decision algorithm flowcharts are shown in the following figures.Table 1. 
Flowchart of an algorithm using parameters: speed change, path and energy density.
Flowchart of an algorithm using the parameters: deceleration and jerk (push).
Flowchart of an algorithm using the parameters: acceleration and speed change.
Algorithm options
Impact detection systems vary greatly between patents. Most systems patented after 1995 use delta-V, acceleration, or jerk as parameters to activate the wake-up system and deploy the airbags. The latest systems also include passenger presence analysis and passenger distance analysis systems. There are significant differences in the approaches taken between 1995 and 2008 by several inventors. However, the command to deploy the airbags depends on one or more of the set of basic kinematic parameters described above.
When the airbags deploy
According to position National Administration US Department of Transportation Traffic Safety enshrined in the relevant US standard, which is also adhered to by a number of well-known foreign car manufacturers), "airbags are generally designed to deploy in frontal and near-frontal crashes that are comparable to impact with a stationary rigid barrier at speeds of approximately 8 to 14 mph." Specific thresholds are calibrated by each manufacturer according to the vehicle size and structural rigidity. The control system is activated to distinguish between events such as hitting a pothole or colliding with another vehicle. This typically occurs when two consecutive acceleration pulses of less than (approximately) -1g for small vehicles, or less than (approximately) -2g for large vehicles, occur within 10 milliseconds. Upon awakening, a decision is made to either deploy the airbags or return to normal.Due to the know-how status, the control algorithms and kinematic parameter values for airbag deployment in a crash are not known. However, using the NHTSA guideline for airbag deployment in frontal barrier impacts at speeds between 8 and 14 mph, a range of kinematic thresholds can be estimated using known vehicle stiffness values and vehicle masses.
Estimation of threshold values
In a collision, the magnitude of the deformation WITH(in inches) at a given impact speed V(in miles per hour) is related to the stiffness ratio of the vehicle k(in lb/in) and its weight w(in pounds) using the following equation:
Time from the beginning of the impact until the maximum impulse is reached upon impact:
Replacing the relation in the first expression C/V from the second expression we get: 
Vehicle stiffness k can be determined from crash test results taking into account the vehicle weight m, deformation C, and impact speed V. The stiffness of the car is calculated using the formula: 
Table 2 shows the corresponding spectrum of decelerations and deformations (displacements) in frontal impact crash tests for vehicles equipped with airbags, taking into account the estimated time for maximum impact impulse and for various vehicles in terms of severity and weight.
Table 2 
It can be seen that there is no significant correlation between the weight of the car and its stiffness. Two cars of similar weight can have very different meanings stiffness, as seen in a comparison of the 2010 Ford Fusion and 2010 Toyota Prius. Both vehicles have approximately the same car weight, but the front stiffness of the Toyota Prius is significantly greater than that of the Ford Fusion. Because the magnitude of deformation and duration of impact is greater in the Ford Fusion, the Ford Fusion airbag will need to inflate to a deceleration rate less than that required for the Toyota Prius.
Comparison of values
The conditions of real collisions often do not coincide with an impact on a rigid stationary barrier, and this must be taken into account when comparing the ranges of actual (from crash tests) and calculated parameter values. The duration of impact does not vary significantly with impact speed, but is highly dependent on the type of impact. The airbags may not deploy if there is a hard impact, such as hitting a pole, where only one part of the car is deformed. Air bags sometimes fail to deploy when the impact occurs gradually over a long period of time, such as when a car is driven under or over another object. Air bags may not deploy in collisions in which the relative severity of the colliding vehicles is very different. For example, a collision between the front of one car and the side of another car. In addition, collisions that occur at sharp angles do not always result in airbag deployment, since significant deceleration in the direction of the vehicles' longitudinal axes (in the direction measured by the impact sensor) does not occur.Example: airbags did not deploy
An example of an impact where there was a significant change in speed but the frontal airbags did not deploy was an accident involving a 2007 Chevrolet Equinox with an oncoming Harley-Davidson motorcycle. The airbag control module in the Equinox recorded a maximum speed change of 9.27 mph. This value is within the 8.0 to 14.0 mph range at which the airbags are expected to deploy (as in the case of a frontal impact with a rigid immovable barrier). However, the maximum deceleration was 3.27g. This deceleration was significantly lower than the calculated value in the deployment range from 7.5g to 13.2g, as shown in the table above. Therefore, the front airbags should not have deployed.Example: airbags deployed
An example of an impact that did not result in a significant change in speed but did inflate the airbags was a crash involving a 2007 Chevrolet Corvette that blew away several road signs, trees, and road posts very far. high speed. The vehicle struck the first object at a speed of more than 60 mph, and the airbag control module recorded a maximum change in speed of 4.96 mph, which is well below the 8.0 to 14.0 mph range in which the airbags are expected to deploy (as in the case of frontal hitting a hard, stationary barrier). Fortunately for the passenger and driver, the recorded maximum deceleration during impact was 11.3g, which is above the estimated threshold range of 6.1g to 10.6g from the table above. As a result, the airbags deployed and saved the lives of the passenger and driver.Conclusion
Airbags must have a control system that can detect impacts correctly and early enough to inflate the airbags safely. Deployment systems typically use electronic sensors that continuously report vehicle acceleration to the airbag control module. The modules use complex algorithms to make airbag deployment decisions based on one or more kinematic variables. Due to the "know-how" status of deployment algorithms, the velocity, acceleration, or deformation values used in these algorithms are unknown. Instead, ranges of impact velocities, decelerations, or deformations can be calculated from crash test data and then used to expert assessment whether the airbags should have deployed in the event of a particular collision.Linksonsources
1. Collision Safety Institute. (2011). Bosch Crash Data Retrieval System – Crash Data Retrieval. Data Analyst Course Manual.2. Huang, Mathew. (2002). Vehicle Crash Mechanics. CRC Press.
3. US Department of Transportation National Highway Traffic Safety Administration. (2003). What You Need to Know About Air Bags - DOT HS 809 575.
About the authors
Jesse Kendall received a Bachelor of Science degree in civil engineering from the University of Vermont in Burlington, Vermont. He completed his engineering internship in Denver, Colorado, working for construction consulting firms before becoming a licensed professional engineer in six states. With over fifteen years of experience in civil engineering Jesse Kendall now lives and works in California at the Institute for Risk and Safety Analysis, specializing in forensic engineering and accident reconstruction.Dr. Solomon received his BS, MS and PhD degrees in mechanical engineering from Los Angeles. Dr. Solomon also holds professional engineering licenses. Dr. Solomon has been conducting research in the field of accident reconstruction and biomechanics for more than 40 years, and has more than 200 scientific publications in international journals, reports and presentations. He and his co-authors have written 13 books. He has served as a senior fellow with the RAND Corporation, and has taught on the faculty of the RAND Graduate School, the University of California, the University of Southern California, the Naval Postgraduate School, George Mason University, and the Orange County Sheriff's Academy.
Driving safety is one of the first issues that a future driver should consider when buying a car. Among all the safety elements, airbags occupy a key place. High-quality pillows can protect against impact even when seat belts are not fastened.
Almost all modern cars are manufactured with the subsequent installation of airbags in mind, so there is no need to worry in advance about “where to install them” and “whether there is room for them in the car.” It is the principle of distinguishing airbags by location in the cabin that underlies the main classification of airbags.
Frontal
As the name implies, they are designed to absorb the impulse in a frontal collision. The driver's airbag is located in the steering wheel, and the passenger airbag is hidden in the panel. The main purpose of front airbags is to prevent injury to the most vulnerable places on the body: the head and neck. The pillow absorbs about 90% of the total impulse and also significantly softens the contact of the face with the surface in front of it.
Side (blinds)
As a rule, curtains are located in the outer cavities of the driver and passenger seats. Unlike front airbags, side airbags are designed to soften the impact of an impact on the entire body, and not just on the upper body. There is also a distinction between driver and passenger airbags. Normally, there are two curtains for each person (they are located at the edges of the head).
Head(neck)
They also cost two for each. They are a type of lateral, but more specialized. Designed to protect the head from a side impact. They are located in the roof of the car, both on the door side and in the center.
Knees
A fairly recently appeared type of pillow, the main purpose of which is to protect fragile knee joint. On the driver's side they are located under the steering wheel, on the passenger's side in the glove compartment area. It costs two.
Central
Like knee airbags, they appeared quite recently and are functionally very similar to curtain airbags (side airbags). Provide additional protection for the hands, especially in side collisions. These airbags are located in the central part of the cabin. There are a maximum of two of them for the whole car - one for the front and one for the rear (if possible) passengers.
In addition, all airbags can also be divided into passenger and driver airbags. The fact is that the driver's seat, as a rule, differs somewhat from the passenger seat in the average distance between the body and the nearest hard surfaces at the time of the collision. The biggest difference is the distance from the driver's body to the steering wheel., which varies greatly with the distance between the passenger and the dashboard.
There are other small differences in distances. In this regard, when installing airbags, their size and speed of full deployment must be selected taking into account their location and design features car. Fortunately, airbags are now beginning to appear on sale, the operation of which can be ideally adjusted based on many parameters, including even the height and weight of the driver.
Currently, development of a new type of airbags designed for rear passengers is underway. The impetus for the start of development was frequent injuries among rear passengers, whom seat belts do not always save from impact. The reason why airbags for rear passengers have not yet been created is because, in contrast to the front seats, fluctuations in the distances between the passenger and internal surfaces car. This implies that the principle of operation of the rear airbags, although it will still be based on the same squib and gas emission, it is not known how much technical modifications they will have to endure until their final implementation. However, taking into account existing advances in the development of security systems, you can be sure that they will appear on sale in the coming years.
Device
There are three main elements in any airbag:
- An airbag module, which includes the airbag itself and its accompanying fixation and deployment mechanisms (spring, slip ring and squib).
- Shock (strain) sensors.
- System operation control module.
The control module includes a system for recording data from collision sensors, a system for diagnosing the state of airbags (their serviceability) and a driver warning system in case of detection of a malfunction in the system (warning lamp).
Strain sensors are devices that stand in different areas parts of the car and will operate when there are excessively sudden changes in vehicle speed.
The main elements of the airbag module are the airbag connector, the clock spring and contact ring (for the airbag installed in the steering wheel), the squib, the gas-generating element, the cover and the airbag itself. The airbag is made of thin nylon about half a millimeter thick, which is strong enough to brake the driver’s (passenger’s) body flying by inertia.
The squib is a detonating device, which by its detonation promotes the release of gas from the gas-generating element, inflating the cushion in a fraction of a second.
The clock spring is a steering airbag-specific element that facilitates uninterrupted power supply to the module and its communication with the control module. The airbag connector provides connection of the module to the control system, as well as notification of problems in the airbag performance if the connection is poor.
During the technical work The connector prevents accidental deployment of the airbag.
The airbag cover (also known as the plug) is decorative element, hiding the airbag from view until it deploys.
Operating principle
IN general outline, the principle of operation of the airbag is as follows: after the car is hit, the sensors located in the car will be activated. Once they fire and send a signal to the airbag control device, the latter determines how many and which airbags need to be activated. Then, a signal is given and the squib located in the airbag is triggered, inflating the pillow.
Now in more detail. If a car gets into an accident, as a result of the impact the car acquires uncharacteristic acceleration and also receives damage. A sudden change in speed as a result of an impact is a condition for the airbags to deploy. These changes are instantly recorded by the corresponding sensors. The sensors transmit information to the control module, from where the signal goes to specific airbag modules.
When a signal to deploy is received, the squib in the airbag module detonates. The resulting volume of gas inflates the airbag in a matter of seconds.
How long does it take? Typically, the response time is about 15-25 milliseconds. This short period of time is due to the need to inflate the pillow before it makes contact with the body. Otherwise, the blow to the pillow will not only not soften, but can cause serious injury, and even death. Such cases occurred in the early stages of the development of airbags. Modern airbags are free of these shortcomings. In addition to instant opening, they also have such a structural feature as gas outlets. This means that the airbag begins to deflate almost immediately after deployment, thereby compensating for excessive pressure on the victim’s body, preventing him from suffocating (in the case of frontal airbags).
Bottom line
Of course, whether or not to install airbags on your car is everyone’s personal choice. However, based on long-term accident statistics, you should not refuse to install an airbag without good reason. If you have any doubts about whether you need an airbag, it is best to gain confidence by watching the video and reading the relevant literature.
On almost every car enthusiast forum there is a person asking why his airbags did not deploy during an accident. Moreover, the answers that are offered are far from the truth. In fact, whether the airbags will deploy or not depends on many factors. At the same time, we are not talking about low-speed collisions, but about catastrophes when the impact is really strong. But to understand this topic, you need to understand how airbags work.
BACKGROUND
These devices have a long history, and their development has not been smooth. 1st patent for instantaneous triggering strong impact The inflatable bag was issued in the USA in the 50s. However, mass production was not established at that time - since engineers still could not make a sensor that would send a signal in the event of a collision. Such a sensor was invented by Allen Breed in 1967. He made a suitable “switch” based on a ball sensor.
But even after this invention, mass production of airbags had not yet been launched. And all because these inflatable bags, which were designed to protect the life of the driver and passenger, were offered as a replacement for the seat belt! Accordingly, motorists treated the innovation with skepticism and were in no hurry to overpay for such a curiosity.
There were reasons for this mistrust, as there were several cases of fatal that have been reported with the use of these pillows. At the same time, there were rumors that in one of the cases death occurred not as a result of a collision, but specifically because of the deployment of the airbag: they say, the driver had a heart attack. Taking into account the growing dissatisfaction, the developers decided to postpone the introduction of pillows for a while.
This new time came in 1981, with the appearance on the market of the Mercedes-Benz S-Class in the back of the W126, which was equipped with inflatable bags. In it, the pillow did not replace the belt, but complemented it. This concept is still used today.
True, security systems are now much more complex in technical terms. The vast majority of modern cars are equipped with the SRS complex (this is a restraint system, short for Supplementary Restrain System). It includes sensors, squibs, belts, an electronic control unit and, in fact, the airbags themselves - the most important element.
OPERATION MECHANISM
Let's take a closer look at the system. There is nothing particularly intricate here: in fact, it is just a bag made of narrow nylon folded into a small capsule. The surface of the fabric is usually sprinkled with talc to prevent it from caking. In the event of an accident, this bag, in a fraction of a second, is filled with gas released from the explosion of the squib.
The design of the squib is also simple: after the control unit commands, a charge filled with a special mixture is detonated. As a result of the reaction, in about 20–50 ms, a huge amount of nitrogen, harmless to humans, is released, which fills the airbag. True, now another scheme is increasingly common in cars, in which compressed gas is stored in a special cylinder, and the squib in this cylinder serves as a plug.
But let’s return to our question: why does the airbag not always deploy during an accident?
Its operation can be affected by a huge number of reasons. One of them is the incorrect operation of the sensors that send a signal to the control unit. There are many similar detectors in a modern car - in front, behind, on the sides. Technically, their design is very reliable, but, like any other technical system, they may malfunction and not work. Or they may make a mistake - consider the blow uncritical. After all, the manufacturer deliberately puts a “reserve” in them so that, unnecessarily, they do not irritate the driver and passengers with a small explosion in the cabin.
But other prerequisites are also possible. For example, there have been cases of sensors not responding due to a voltage drop in the electrical system. Situations can be much more prosaic. Such when the driver simply did not fasten his seat belt - in this situation, the protective device will not allow the airbags to deploy. After all, if, in a collision, such a driver is hit in the face by an airbag, which flies out of its nest with an acceleration of 200–300 km/h, then it will not help, but, on the contrary, will cause damage to health, and can even kill the driver.
It is also worth considering the situation with heavily used cars that have already been in serious accidents. Often careless sellers of such cars do not want to spend money on replacing a deployed airbag. As you know, its module is disposable, and, after operation, it must be completely changed, and this is an expensive undertaking!
So various “craftsmen” put plugs in the places where the pillows should be located, and re-flash the control unit so that it does not show an error. At the same time, it is practically impossible to detect such a substitution when buying a used car. The only way to somehow protect yourself from being scammed is to find signs of an accident on the body.
Another reason for the airbags not to deploy could be obvious bagging or a lack of squib.
The main conclusion from all of the above is this: although the probability is small, the airbags may indeed not deploy in an accident. And it is very important not to rely too much on them and not to guess whether the airbags will work. Just as you shouldn’t rely too much on others latest systems safety, but you must always remember that airbags of the SRS system are not a panacea, but only an additional means that allows you to survive and minimize the risk of serious injury.
