"Inflatable" protection: how do airbags work and what are they? How an airbag works What are airbags made of

For many years, a reliable seat belt has been the only form of passive safety in our cars. There have been debates about their safety, especially with regard to children, but over time, most of all countries have adopted wearing seat belts as a mandatory condition on the road. Statistics show that the use of seat belts has saved thousands of lives that could have been lost in the event of a collision.

But just like seat belts, the concept of airbags - a soft support to relieve a person from the consequences of an accident - has been an idea of ​​​​engineers for many years. The first patent for an inflatable airbag for aircraft was filed during World War II. And in 1980, the first commercial airbag appeared in cars.

To date, the vast majority of not the most budget cars are equipped with airbags at least for the driver and front passenger. Statistics show that airbags reduce the risk of death in a direct frontal collision by about 30 percent. Seats and/or doors are increasingly being fitted with side airbags. Today, some vehicles go far beyond the current dual airbag standard, with six or even eight airbags for the driver and all passengers. But they are still the subject of much debate and scrutiny by government and industry.

In this article, we'll learn about the science behind these devices, how an airbag works, when it deploys, what its problems are, and how far the technology has advanced today.

Laws of motion

Before considering the specifics, let's review our knowledge of the laws of motion. First, we know that moving objects have momentum (the product of the mass and the speed of the object). If some force acts on an object and then ceases to act, then the object will still continue to move, only reducing its speed - this is called inertia. A car is made up of several objects, including the vehicle itself, loose items in the car, and, of course, the driver and passengers. If these objects are not attached to the body of the car, then they will continue to move at whatever speed the car is moving at, even if the car is stopped by a collision.

Stopping an object's momentum requires a force acting for a short period of time. In an accident, the effort required to stop an object is very large, because the momentum of the car has changed instantly, but the passengers have not, and there is not much time to work. The purpose of any secondary restraint system is to help stop the occupant while causing as little harm to him or her as possible.

The pillow is designed to slow down the speed of the passenger to zero with little or no damage. At the same time, the framework in which it must work is huge. The airbag during its operation occupies the entire space between the passenger and the steering wheel or dashboard in a split second.

The purpose of an airbag is to slow the forward movement of the passenger as evenly as possible in a fraction of a second. The pillow consists of three parts, each of which helps to accomplish this feat:

• A bag itself consists of a thin nylon fabric that folds into the steering wheel or dashboard, or, in the case of a side airbag, in the door.
• Sensor is a device that tells the bag when to inflate. The inflation occurs in a collision with a force equal to at least a collision with a brick wall at a speed of 16-24 km per hour. The mechanical switch turns to close the electrical contact. The sensors, meanwhile, receive information from an accelerometer built into the microchip.
• Inflating system serves to quickly inject gas into the cushion due to the reaction of sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas. The nitrogen explosion inflates the airbags almost instantly.

Early attempts to adapt an airbag for use in automobiles faced prohibitive costs and technical hurdles associated with storing and releasing compressed gas. The researchers asked questions:

• Where to get the necessary sufficient space in the car for the gas cylinder?
• If the gas stays in its calm state for a long time under high pressure, then it's quite dangerous, isn't it?
• How could the bag be expanded quickly and reliably at various operating temperatures and without a deafening explosion?

All questions of scientists disappeared when solid fuel came to the rescue in 1970. Solid fuel burns very quickly, creating a large volume of gas and making less noise.

Among other things, the air cushion is lubricated with a powdered substance regularly - often cornstarch or talcum powder - which keeps the bags flexible and lubricated while they are "in storage".

Any modern car has a passive safety system, which includes (depending on configuration):

• seat belts and their tensioners;
• airbags;
• battery emergency disconnect and other elements.

The most effective among them is the airbag, which protects the driver and passengers from injury as a result of their physical contact with the interior and body parts of the car during an accident.

Purpose and circuit diagram of the system

An airbag (or airbag) is a special device that is an elastic elastic shell filled with gas. It works in conjunction with the seat belt to cushion the impact and prevent injury to the driver and passengers in an accident. Videos of numerous crash tests brilliantly demonstrate its effectiveness.

However, the actual airbags in the car are only part of the whole security system, which consists of three main components:

1. airbag module (or several modules);
2. input sensors;
3. control unit (or diagnostics).

Airbag module

The airbag module device includes a lightweight nylon-based airbag, a pneumatic airbag inflator (gas generator) and a squib (actuator of the inflator). The airbag itself is made of nylon fabric material, and to increase the speed of its operation and ejection, a special lubricant based on talc (less often starch) is used.


The purpose of the gas generator is to fill the nylon shell with gas (for example, air) as quickly as possible. The squib operates as a means of forced opening of the gas generator valve, its operation and subsequent ejection of the air bag.

Input sensors

These are electronic indicators located, as a rule, in the front of the car (in the cabin and outside it). Airbag sensors come down to two main types:

• shock sensor (indexing the blow to the car body);
• passenger seat sensor (indicating the vacancy of the seat and excluding the operation of the corresponding air bag).

Their functions are to activate (or refuse to activate) under the influence of forces that have arisen during an impact and a sharp deceleration, with the subsequent transmission of an appropriate signal to the airbag control unit in the car.

Control unit (or diagnostics)

Responsible for the activation of the entire system and the operation of the airbags in the car. In addition, it performs the functions of monitoring the state of the system and (in the event of a malfunction) signals the driver about the need for service. The control unit is activated when the vehicle ignition is on. In some models, the system is equipped with a special forced shutdown button (if such a need arises).

The main types of air bags and their characteristics

The device and design of all modern models of passenger cars provide for the possibility of installing airbags. Basic car configurations, as a rule, exclude this component from the list of their equipment due to a significant increase in the cost of the model.
Currently, there are five main types of air bags. This classification is based on the principle of localization - its location in the car. Depending on this, experts distinguish front, side, head, knee and central airbags.
Frontal airbags are designed to protect the head and neck of people in the front seats of the car.
Depending on the destination, there are:

1. driver's airbag;

The driver's airbag is located inside the steering wheel, and the passenger's - in the upper part of the panel ("torpedo"). As a rule, the driver's airbag is much smaller than the passenger airbag. This is due to a significant difference in the distances between the driver and the steering wheel, on the one hand, and between the passenger and the instrument panel, on the other. Recently, frontal modules use multi-stage (two-stage or more) operation in case of accidents of varying severity. These are the so-called adaptive frontal airbags.


Side airbags perform the function of protecting the chest, abdomen and pelvis of a person. They, like the front ones, are represented by airbags for the driver and passenger, which are most often located in the cavities of the front seats. Some car models provide side airbags in the rear seats to protect passengers sitting in the back.


Head airbags (or “curtains”) are actually side modules, but they are their independent and autonomous version and are intended to protect the head from injury during a side collision and impact. As a rule, curtains are placed under the interior roof lining (near the doors and the B-pillar).
Head airbags can be represented by:

• driver's airbag;
• passenger airbag (or passengers).

The driver's and passenger's knee airbags are a special version of frontal airbags designed to protect a person's knee joints from damage and injury. They are located either under the steering wheel (driver's), or in the under-panel space - under the "glove box" (passenger).

Recently, a central airbag has come into use, providing for the possibility of reducing secondary damage to the driver and passengers in an accident. It is located in the armrest of the driver's seat ("bar") and the central section of the rear seat.

Thus, the modern device and layout of airbags allows minimizing the risk of serious injuries to people in an accident.

Principles and conditions for the operation of air bags

The system is by no means a complex device and is based on impact as the main indicator of its operation. The impact is picked up by the appropriate sensors and signaled to the control unit. However, the main conditions for the start of the action is the impact force exceeding the level set by the system. If so, the control unit activates the air bag module igniter. The gas generator instantly (within 40 ms) inflates the nylon shell with gas, which contributes to its ejection in the direction of the driver or passenger, preventing them from injury.
The system understands impacts as indicators of airbag deployment:

1. actual blows to the body of the car - straight or oblique, frontal or side;
2. collisions with large obstacles (curbs, large pits, potholes, etc.);
3. fall from a height, overturning, hard landing of the car.

The best demonstration of the functioning of air bags is, of course, video materials.

It is important to note! The system is tuned to a rational principle of operation: the activation and operation of specific airbags is determined by the specific localization of the impact. In other words, of all the airbags, only the necessary one works. So, in a frontal impact, the frontal airbags are necessarily activated. In a front-to-side impact, there is a high chance that the system will activate the front, side, and head airbags. Accordingly, in a side impact - head and side airbags.


One of the indicators may be a sharp slowdown of the vehicle (for example, emergency braking). However, this factor is not decisive when the system is triggered. The fact is that the sensors that detect the deceleration do not send automatic commands to the gas generator, but, as in the first case, they only “notify” the control device of an unusual situation. For the unit in determining the direction of the system's operation, such information is correlative, that is, it creates the conditions for the start of action (and most often for warning about a possible danger).

The algorithm and principle of operation of the system are in constant development as part of the improvement of the overall passive safety system of the car.

Features of transporting children

Transporting children in a vehicle equipped with airbags is a special mode of travel. This is due to the fact that deployed airbags can cause serious injury or even kill a child who is not wearing a seat belt.

That is why the experts were unanimous in developing special requirements for the transportation of children in a car with airbags.

Firstly, it is recommended that children be transported only in a well-secured special seat and only in the back seat.

Secondly, if it is impossible to turn off the front passenger airbag, transportation of children under 1 year old in the front seat is excluded.

Thirdly, in the case of movement with a child in a special seat in the front seat, the latter must be moved as far back as possible.

Outside (external) airbag

In 2012, the designers of the Volvo concern designed and implemented the concept of using air bags not only inside the car, but also outside it. These are pillows designed to provide maximum safety for pedestrians in direct frontal contact with the vehicle. In particular, to prevent or minimize their injury. According to statistics, in such accidents, more than three-quarters of deaths are due to the fact that a pedestrian hits his head again on the details of the exterior of the car. Proof of this are the numerous (unfortunately!) videos posted online by the owners of car recorders.

This security system is designed with the use of airbags. which, if necessary, shoots from under the hood. The hood is lifted with the help of a specialized hinge release mechanism. The air-filled rectangular elastic shell covers the most dangerous sector of the windshield and the metal front pillars of the car, softening the blow and preventing serious injuries to the pedestrian. The effectiveness of this system is well demonstrated in the video.

It is likely that such a mechanism is a future promising direction in the development of airbags.

Air bag service

Is it possible to monitor and self-maintain the system? It seems that control over the operation of air bags is more than possible, thanks to the electronic indication of its condition. So, in the event of a malfunction, a special indicator lamp will warn the driver about the prospect of a system failure and the need to visit a service center in order to diagnose and service it.

However, self-repair of the system is possible only with the involvement of highly specialized personnel of an authorized service or center. The fact is that airbags are disposable devices, and after operation, they can only be replaced with a new set. This requires additional reconfiguration and diagnostics of the entire control system.

For many years, the seat belt has protected passengers and the driver in the event of an accident. But modern technology and the automotive industry are developing, there is a need for more effective protection. With the advent of airbags, we can say about the reliable protection of people in the car. The airbag inflates in just a fraction of a second in an accident. It is able to protect the body and head from injury.

Airbag Reliability

Crash tests show how safe modern car models are. If there are no pillows in the car, then the driver and passengers risk their health and life. More reliable protection is provided by the presence of at least two pillows in front. In this regard, there were cases when a driver was injured from a blow with a pillow, and not in an accident. This arose as a result of incorrect adjustment. The airbag is fired at a speed of over 300 km/h. This is a powerful blow. If it did not work correctly, then the driver may have head injuries. And yet, during their existence, they saved many people and cases of failures in work are isolated.

How does an airbag work

The airbag has a far from 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 inflates with a sharp push with air. It is installed in the car under the plastic lining. The sensor is sensitive, it is he who releases the pillow. It is usually set up to fire the airbag at low speed in a crash. A complex device is responsible for a quick shot of the pillow and its inflation with a special composition. This is a pillow inflation system that includes electronic and chemical components. We will not consider electronics here, but the chemistry in the airbag is the subject of our interest.

When designing an airbag, the inventors had to solve the following problem. If the car crashes at low speed into any object, then the sensor reacts in connection with the load. The launcher detects this and gives a signal for instant take-off and airbag inflation.

At first, they tried to install gas cylinders in the passenger compartment, 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!

In the inflation system there are tanks with sodium azide (NaN 3) with potassium nitrate (KNO 3). In the event of an accident, electronic impact sensors initiate the ignition of a solid propellant charge, which starts a chemical reaction that produces a large amount of nitrogen. The reaction is so rapid (the total time from the start of the ignition 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 instantly bleeds through special holes. This is done for safety reasons, because if you do not blow off the pillow, then a person can be tightly clamped to it in the cabin! During the blowing of the pillows, 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 at present, models with six different pillows are being made.

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 do not allow injuring the head in a side impact. Manufacturers also took care of the protection of the legs and created a pillow that proved 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 at the same time, you must not forget to fasten your seat belts.

Each automaker, before releasing a new car on the conveyor, conducts a series of tests, including a crash test, according to the results of which a degree of protection for drivers and passengers is assigned. One of the main means of passive safety (SRS - Supplementary Restraint System) in the car are airbags (aka AirBag). Let us consider in detail where the airbags are located in the car, as well as where the airbag sensors are located.

Location of airbags

Front AirBag

First of all, cars are equipped with an airbag for the driver, since for him the risk of injury in an accident is greatest. The pillow is located in the steering wheel, so the driver needs to be at least 25-30 cm from the steering wheel so that at the time the AirBag is triggered, it will be useful, and not unnecessary harm. Also often in the base there is a second pillow - for the passenger in the front seat. It is located in the dashboard opposite the passenger, can be switched off. The purpose of these pillows is to protect the head and chest of the driver and front passenger in a frontal (frontal) impact.

Side Airbag and curtain airbags

These pillows are located in the side of each of the front seats, they are designed to protect the pelvis and chest of the driver and front passenger. The side curtains open at the level of the side windows of the front and rear rows of seats to protect the head and neck from hitting the glass in a side accident or a car overturning. They are located in the front and rear of the cabin in the window pillars.

A set of six airbags is becoming the norm for modern cars, starting even with the B-class, but some automakers are trying to make their cars as safe as possible by using some more places for the AirBag.

Knee AirBag

This pillow allows you to avoid injury to the driver's legs, is located under the steering column. Some models also have a knee pad for the front passenger, located under the glove box.

Central AirBag

The purpose of such a pillow is to protect the heads of the driver and front passenger from impact.
each other in a side impact. It is located in the armrest of the front row of seats.

BeltBag

Such a pillow is sewn into the seat belts for the rear passengers in order to protect the chest and neck of the passenger.

AirBag for pedestrian

The purpose of this pillow is to protect a pedestrian's head from hitting the windshield when hitting a pedestrian. The pillow shoots out from under the back of the hood.

Location of airbag sensors

AirBag sensors can be located both outside the car and in the passenger compartment - depending on the installed airbags. Each pillow is connected to its own sensor, so they work independently of each other. For front airbags, there are two sensors in the engine compartment, usually on the side members, for side and central airbags - in the front doors. For front curtains - in the left and right pillars of the windshield, for rear curtains - in the area of ​​\u200b\u200bthe arches of the rear wings.

For many years, the tried and true old belt has been the only passive safety protector in our cars. There was a lot of debate about the effectiveness of its use, especially for children, but over time, many countries around the world have legalized the mandatory use of seat belts in cars. Statistics have shown that the use of seat belts has saved thousands, hundreds of thousands of lives in the most serious crashes.

Just like with seat belts, the concept of an airbag, a soft cushion into which you can “land” your body in an accident, has long been in the air, literally and figuratively. The first officially registered patent for an inflatable pillow for aircraft (yes, they came to us from heaven) was issued during the Second World War. And only decades later, the first pillows appeared on cars, it happened in the 1980s.

Since 1998, most of the new passenger cars (developed mechanical engineering) have been equipped with airbags, both for the driver and for the front passenger. In 1999, this rule affected larger cars, jeeps and minivans. Further, pillows began to appear in other places, in the seats, doors and other parts of the car. Today, in some cars, the number of pillows is much more than two, 6 and even 8 pieces have become the norm.

With a similar controversy as with seat belts, airbags have been the subject of significant research, testing, and debate at the highest level.

To date, statistics confidently show that such devices reduce the risk of death by about 30%.

In this article, you will learn about the operation of these devices, how their action has been scientifically confirmed, what shortcomings they have and ways of future development.

Safety bag

The purpose of an airbag is to slow the forward movement of a person's body as evenly as possible in a fraction of a second. Here are three components of the airbag that help achieve this goal, that is, at the right time to work:

The pillow itself. Made of thin nylon, folded into the steering wheel, dashboard or seats, doors and other parts of the car.

Sensor. A device that "tells" the airbag to deploy. The triggering occurs at the impact force corresponding to a collision with a wall at a speed of 16-24 km / h. impact goes to the control unit, which in turn determines whether the airbag inflation system works or not.

Pillow inflation system combines two constituents, sodium azide (Nan3) with potassium nitrate (KNO3), to create nitrogen. He is the one who inflates the pillow.

Early attempts to adapt the airbag for use in cars ran into a number of difficulties, some of which were the incredibly high price and technical problems, including the storage and use of compressed gas.

In the early stages, researchers had to decide:

Where to place a compressed gas cylinder

Will gas stored under high pressure escape throughout the life of the vehicle?

How to make the pillow open almost instantly, while being reliable under various temperature conditions and not making a deafening sound when opened.

Gradually, all the most important issues were resolved. The impractical gas was replaced by a reliable solid-state element - a squib, this happened in the 70s of the twentieth century. In the event of an accident, the "brains" of the airbag initiate the ignition of a solid propellant charge, which burns out at a tremendous speed and creates in a short time, 30-50 milliseconds, the necessary amount of gas to fill the airbag. The dome of the pillow literally explodes, leaving its seat at a speed of up to 322 km / h, faster than the blink of an eye! Fractions of a second later, the gas under pressure escapes through special holes (it is this smoke mixed with talc in the car interior that can often be observed during an accident).

Types of airbags

In modern times, there are a large number of airbags.

The most common type are front airbags for both drivers and front passengers.

The next stage of development was side airbags. Their function is to protect the chest and pelvis of a person from damage during a side impact.

So called "curtains" or head airbags. Protect a person's head from contact with solid parts of the car in a side impact.

Airbag for knees. To reduce the risk of injury to the knee joint (which often happens in a frontal impact), a similar airbag was developed.

Seat belt with integrated airbag. Reduces the risk of chest injury.

Central airbag. Was designed not so long ago. Its task is to prevent the collision of two people sitting next to each other during a side impact or coup. It also avoids neck injury.

Security measures

From the very beginning of the use of airbags, experts who studied the issue of the operation of this means of protection realized that it can bring not only benefits, but also harm. The second option is possible if the vehicle's passive safety equipment is used incorrectly. What is meant by this?

1. The minimum distance between the airbag and the seated passenger must be at least 25 cm, otherwise, when opening, a person may be injured directly from the airbag itself.

2. The passenger must be fastened. Since the seat belt reduces the speed of movement of the human body and directs it in the right direction to the airbag.

3. If an airbag can easily injure an adult, then the situation is even more difficult with children. The first condition for the safe transportation of a child. He must be transported in a properly installed, age-appropriate seat in the back seat.

4. If a child is to be transported in the front seat on the passenger side, he must sit in a seat located in the direction of travel, and the seat must be moved as far back as possible.

5. Infants must not be transported in a reversible child seat in the front seat with the front airbag activated.