Airbags in a car: design, principle of operation, service life

06.11.2019

Issues discussed in the material:

• How do airbags work and how do they work?
• What are the different types of airbags for?
• What is the service life of car airbags?
• How to check airbags when buying a car
• For which airbag malfunctions is it not recommended to use the car?

A mandatory attribute of a modern car is the SRS system. If it works properly, then the people in the car at the time of the accident will remain alive. Otherwise, the consequences of an accident may be irreparable.

The long history of using the airbag has shown that this invention saved many people from imminent death. This complex system comes into action a few fractions of a second after a collision occurs. This is the only way to 100% protect everyone in the vehicle. Today we will look at what airbags are in a car and how they function.

What are airbags

Airbag is a mandatory component of a car's passive safety system. A pillow is necessary to protect everyone in the car from injury in an accident. In fact, despite the name, the airbag is not at all like the usual pillow we sleep on. However, there is one common property: softness. Airbags in a car are divided into several types:

• frontal, which are located in the front area of ​​the car;
• lateral, located on the side;
• curtains placed above the side windows;
• knee, protect the legs of a person.

When you drive a car every day, you don’t even think about the fact that this mandatory attribute is present in the car. After all, airbags in a car are folded and hidden under the trim.

Operating principle

In general terms, the principle of operation of an airbag is as follows: after a car is hit, the sensors located in the car are 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).

How do airbags work in a car?

It cannot be said that the airbag design in a car is complicated. The airbag package includes several components. This is a bag, shock sensors, and a gas generator.

1. Bag

Made in the form of the thinnest nylon shell, which has several layers. Moreover, the thickness of each layer is less than 0.4 mm. Despite this, the bag is not afraid of the strongest short-term loads. It is located in a special tire, hidden behind a plastic or fabric cover.

2. Shock sensors

These elements are usually located at the front of the car. Their task is to ensure rapid deployment of the airbag in the car. Sensors instantly give her a collision signal if the speed exceeds 20 kilometers per hour. In addition, the force of the blow is also analyzed. This means that the car's airbag system will deploy even if the car was parked but another driver crashed into it with great force.

Sensors are divided into several types:

• shocks are triggered if the car has suffered a severe blow;
• Passenger seat sensors record how many people are currently in the car and prevent other airbags from deploying if only the driver is in the car at the time of the accident.

The airbag system in a car includes accelerometers. They are necessary to determine the location of the vehicle.

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3. Gas generator

Previously, the airbag system used only 1 squib. As a result, it was not easy to adjust the gas supply to the airbag based on the size and position of the passenger or driver. Today, airbags in cars are equipped with two squibs. The main one supplies 80% gas (soft landing). The other one comes into play if the blow was so strong that enhanced protection is necessary.

It is important that all elements of the airbag are in working order. Otherwise, there will be no guarantee of the effectiveness of impact protection.

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 status 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 are located in different parts of the car and will work when there are excessively sudden changes in the speed of the car.

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.

Airbag device

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.

Gas generator

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 maintenance work, the connector prevents accidental deployment of the airbag.

The airbag cover (also known as a cover) is a decorative element that hides the airbag from view until it deploys.

How do airbags deploy in a car?

What is the principle of airbag deployment in a car? If an accident occurs, the airbags must deploy. And all this happens in a few fractions of a second. This speed is possible due to the fact that they are filled with a special gas. The human eye is not able to see how the security system works. What happens when the airbag opens:

1. The car body takes a severe blow.
2. The sensors are automatically triggered and send a signal.
3. The ECU gives a command to the security system, after which the detonator is activated. It is a charge of sodium acid tablets. As a result, argon or ozone gas is heated, which comes out under a pressure of 250 MPa. Before this happens, the gas cools down as it passes through a metal filter. The airbag is completely filled and opens 30 milliseconds after the electronic sensors give a signal. An expanded pillow completely fills the free space between a person and the car body.
4. When the airbags in a car deploy, the head hits them. 90% of the impact energy is extinguished, and the person remains unharmed. In the event of an accident, impacts on the steering wheel, pillars and panels are excluded. That is, the human body hits a soft cushion, and not hard body elements. And people injured in road accidents do not receive serious injuries incompatible with life. A fairly soft airbag protects the body from internal injuries. After all, a large percentage of deaths in collisions occur due to internal organs hitting bone structures when a person suddenly slows down as a result of the impact. If the brain hits the skull bones during an accident, an injury that is incompatible with life occurs. The principle of operation of an airbag in a car is based on the fact that it gradually dampens the inertial speed of movement, and the human body does not stop so abruptly.
5. After the airbag opens, gas begins to escape little by little. This is necessary so that victims can easily leave the vehicle. The airbag in the car gradually deflates.

To understand how airbags work in a car, you need to understand the design of a particular car. After all, only two airbags can be installed in a car. The number of emergency elements can be even greater. For example, in some cars, airbags are placed in each plane.

It should be remembered that the airbag system can only protect against the first collision. However, an accident may occur in which there will be 2-3 subsequent impacts. In addition, the airbag is only used once.

In a standard situation, when you are just driving a car, the airbag will never inflate. The fact is that it is equipped with sensors. Disclosure occurs in specific circumstances, such as when a collision has occurred. And if the driver accidentally lightly touches the bumper to a high curb, the airbag system will not react to this in any way.

To learn how airbags are made and how they deploy, watch the following video:

How many airbags are there in modern cars?

Currently, outdated car models without airbags are still being produced. But over the years, their number has decreased significantly.

How many airbags are there in a car? Modern cars have 2–7 airbags. In rare cases, 8–10 items are found.

All airbags in a car are divided into several types:

1. Front

Driver and front passenger front airbags are found on most modern cars. They protect against impact to the nose of the car, for example, in a head-on collision.

Frontal airbags prevent a person from hitting the car panels and slow down the movement of the body when an accident occurs. Thanks to them, a person’s loss of speed occurs more slowly, which means that overloads are reduced and the risk of internal injuries is reduced.

The driver's front airbag is located in the central area of ​​the steering wheel, and the passenger's airbag is located at the top of the front panel. These two pillows differ in size, because the gap between the driver's head and the steering wheel is smaller than the gap between the passenger's head and the panel. In addition, the passenger airbag is equipped with a special button, by pressing which you can turn off the airbag. This is done in case there is a child in a child seat on the seat.

Your car's front airbags inflate only when a collision occurs. Please note that in a car with airbags, the front panel will have the inscription “airbag”. While driving, you should not hold luggage or any objects in your hands. Do not put your feet on the area in which the airbag is located. Otherwise, when the airbag deploys, a person may be injured and will be to blame for this.

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Frontal airbags are installed even on inexpensive cars, including Russian-made cars, such as the Lada Granta.

2. Front side airbags

Airbags of this type are not installed on cars as often as front airbags. They are usually supplied to premium cars with advanced equipment. Such airbags protect the shoulder area, sides and pelvis from impacts if a collision occurs with the side of the car. Most often they are located in the side area of ​​the front seats, where the car doors are located.

How to transport cargo in cars with side airbags? Do not leave bulky items in door pockets. After all, in the event of a collision, they can interfere with the normal opening of the airbag or cause harm to the passenger or driver.

Front side airbags are mounted on modern Russian cars, for example Lada Vesta, and on budget foreign cars, for example Renault Logan, Datsun On-Du.

3. Curtain airbags

This element is designed to protect a person's head if a side collision occurs. Curtain airbags are divided into two types:

• to protect the front row of seats;
• to protect both front and rear seats.

Curtain airbags are installed in the side area of ​​the car's roof, directly above the windows and in the side pillars. When an accident occurs, the open curtain blocks the side windows of the car. This prevents injury from broken glass and does not hit the pillars or hard elements of the car.

Curtain airbags are installed on inexpensive B-class cars, for example, Kia Rio, Hyundai Solaris.

4. Knee airbags

The purpose of the knee airbag is to prevent a person from being hit on the knees if a head-on collision occurs. The driver's airbag is located under the steering wheel at the bottom of the panel. The passenger knee cushion is located in front of the passenger seat.

If your car has such an airbag, you should adjust the driver's seat correctly. The person's feet should be at least 10 cm from the bottom of the panel.

You can find a driver's airbag of this type on C-class cars in the middle price segment, for example, Volkswagen Golf, Suzuki. The passenger knee airbag is mounted exclusively on premium SUVs, such as the Toyota LC200.

5. Rear side airbags

Why are these types of airbags needed? They prevent impacts to the shoulder, side area and pelvis of rear passengers. That is, the purpose of using the rear side airbag is the same as the front side airbag. The rear airbags are located in the lower area of ​​the side trim of the car, on the side of the rear row of seats.

Airbags of this type are installed on some modern cars, for example the Skoda Octavia.

If you see the airbag designation, it means that there is an airbag in the car in this location. The inscription is extruded onto a plastic panel or applied to a fabric tag.

Front, knee, rear side and curtain airbags are most often indicated on plastic trim elements. The location of the front airbags is indicated on fabric tags on the side of the seats.

There is no need to dismantle the interior trim near the location of the airbags if the battery is not disconnected. Otherwise, the airbag may open, resulting in injury to the person.

Some statistics

Research activity regarding the effectiveness of airbags peaked in the early 2000s. Pillows have been widely adopted since the early 90s, and a decade later, researchers have a basis to study.

In 2001, the US Highway Safety Administration (NHTSA) concluded that airbags saved more than 8,000 lives in the first decade. In 2009, NHTSA calculated that when seat belts are worn, frontal airbags reduce the risk of death by 11%.

Photo: emercedesbenz.com

In 2003, doctors Eliza Braver and Sergei Kirichenko studied accident data in the United States in 1999-2001, and came to the quite expected conclusion that the presence of side airbags in a car significantly reduces the risk of death in a side collision. Statistics were collected exclusively on then-modern cars of the 1997-2002 model years.

And now the specifics: over two years, 1,800 people died in side collisions in cars without side airbags at all, 105 people died in cars equipped only with torso airbags, and only 35 people died in vehicles with inflatable curtains to protect the head. It turns out that the presence of side airbags reduces the risk of death in an accident by one or two orders of magnitude. A good reason to think about the configuration of your car.

Photo: emercedesbenz.com

It is worth noting that any statistical analysis is something conditional. It is always difficult to identify the exact cause of a person’s death in an accident, and even more so to understand why the person who survived the accident did not die. In this case, full-scale tests of cars with airbags, that is, crash tests, are very useful.

What to do if the airbags deploy

By default, airbags deploy in the event of a severe accident. Since they are disposable, once the airbags in your car have deployed, they need to be replaced.

In addition, new electrical sensors should be installed, as well as casing parts that became unusable after the airbags exploded. Naturally, it may be necessary to repair a car damaged in a collision.

In some cases, the car owner refuses to restore the vehicle. After all, the price of repair work may be higher than the price of exactly the same new car.

How else to blow up the airbags in a car? Occasionally, airbags deploy without an emergency. For example, when an inexperienced car owner begins to disassemble the trim. Then the car enthusiast will have to buy airbags for the car. The price of the product can reach 10,000–20,000 rubles. In addition, repair costs must be taken into account.

Experts do not recommend replacing airbags yourself after an accident. The point is that in this case you will not be able to test whether they function correctly. This can only be done when an accident occurs. And this is fraught with the fact that the airbags will not work. As a result, both passengers and the driver will be injured.

Pure mechanics

Before you begin analyzing the operation of airbags, it is worth brushing up on the laws of mechanics. As you know, any moving object has momentum (mass multiplied by speed) and under the influence of some force it moves. But as soon as the force stops influencing it, the object will not stop immediately, but will continue to move, reducing speed. This is called inertia. In the case of a car, the driving force is the engine.

All loose objects in the car, including the driver and passengers, will also continue to move at the same speed as the vehicle when braking. To stop them, force must be applied for a certain period of time. Its significance is very high in the event of an accident, since the car stops abruptly, while the bodies retain inertia, which does not end instantly.

Is it possible to install additional airbags in a car?

Some car owners are interested in whether it is possible to install additional airbags. For example, at the time of purchasing the car the budget was limited. A few months later, the money had been accumulated, and the new owner of the car wanted to make the vehicle safer.

In theory, this can be done, but in practice you will have to spend a large amount. In addition, not every master will agree to perform such an installation. It will be more profitable to buy another exactly the same car, which already has additional airbags, rather than trying to install airbags in the car, as well as sensors and control units. Therefore, it should be understood that installing additional pillows is impractical and is not carried out.

General tips for replacing SRS

If you are weak in electronics, then I will immediately say that you should not start this business yourself, you will not be able to get by with just unscrewing the bolts and replacing it with a new part; you will have to rearrange the sensors and flash the control unit.

The on-board computer has its own nuances, and when the airbag is deployed, the on-board computer records an error in its memory. Therefore, it will also have to be replaced entirely, if not flashed.

Let's consider the replacement process itself, when the impact falls on the front or rear bumper; these are the situations that arise most often. To do this, we will need to replace two airbags, the driver's on the steering wheel and the passenger's.

Airbags and seat belts work together

Many inexperienced car owners are confident that when the car is equipped with airbags, the person is completely protected from injury, so it is not necessary to buckle up while driving. The most resourceful ones, so that the seat belt sensor does not work, pass it through the back and tuck it into the buckle. You can't do it this way.

The fact is that airbags were designed in such a way that they must be used in conjunction with seat belts. Therefore, when a person who was not wearing a seat belt gets into an accident, the inertia will continue to move forward. In this case, the pillow that is supposed to protect him will open in his face at a speed of 200 kilometers per hour. This means that a person can be seriously injured.

This is why it is so important to always use seat belts as intended. Plus, they can protect you even if you don't have airbags in your car. But airbags will only work correctly together with belts.

How to check airbags

If you are purchasing a used car, you should not only make sure that it is in good working order, but also test the operation of the airbags. How to check airbags when buying a car second-hand?

First of all, you should make sure that they should be in this car. Therefore, the first thing you need to do is find the SRS or Airbag designations located on the steering wheel or front panel. There should be no scratches or cracks near the inscriptions, because this indicates that the pillows have already been used. And it is unlikely that the former owner of the car would spend money on charging the airbags in the car. Even if the airbags were filled with gas, no one can guarantee that it was done correctly.

The next step is to find the date when the seat belts were made. The date must be the same for all products. Otherwise, if the data differs, it means that the belts were replaced, for example, after an accident in which the airbags deployed.

How to check the presence of an airbag in a car and its serviceability? There are several more methods:

• Turn the ignition key and look at the dashboard. The “airbag” icon will appear for a couple of seconds and then go out.

• There may be a port located under the steering wheel of the car through which the vehicle's health can be checked. We start the car, wait half a minute, close contacts 4 and 13 using a simple paper clip. This will cause the buttons on the dashboard to blink. You will see an image of a man with a pillow, and this button will blink more often than others. This means there is a malfunction in the security system.

Is the indicator not blinking at all? This indicates that this function was disabled by the former owner of the car.

The service life of an airbag in a car is 10–14 years. It all depends on the year of production of the car, make and model. After the specified time has elapsed, the cartridge discharges and the airbag stops working. Carefully examine the car glass, including the windshield. Is it obvious that they have been replaced? This means the pillows were most likely used.

Outside (external) air spring

In 2012, the designers of the Volvo automaker designed and implemented the concept of using air bags not only inside the car, but also outside it. We are talking about airbags designed to ensure maximum safety for pedestrians in direct frontal contact with the car. In particular, to prevent or minimize their injury. According to statistics, in such accidents, more than three quarters of deaths are caused by the fact that the pedestrian hits his head a second time on parts of the car’s exterior. Proof of this are numerous (unfortunately!) videos posted online by owners of car registrars.

This security system is designed using an airbag. which, if necessary, shoots out from under the hood. At the same time, the hood is raised using a specialized hinge release mechanism. An elastic rectangular shell filled with air covers the most dangerous sector of the windshield and the metal A-pillars of the car, softening the impact and preventing serious injuries to the pedestrian. The effectiveness of this system is clearly demonstrated in the video. It is likely that such a mechanism is a promising future direction in the development of air bags.

How to use pillows safely

Airbags located in the front are used to prevent injuries to both adults and children. However, the child is smaller in build, which means the pillow can cause harm to him. If there is an airbag sign on the front panel, it is prohibited to place a child in the seat. In addition, you cannot install devices in the car that could prevent the airbag from opening or injure a person.

The SRS system is equipped with a special indicator. When it lights up even after the car has been started and you have started driving, you should go to a car service center. After all, the above signs indicate an error in the system.

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Otherwise, the mounts may shoot out when the car is being repaired, for example, when troubleshooting electrical problems. As a result, the person will be injured. It is recommended to trust repair work only to experienced professionals. The firing speed of an airbag in a car is quite high, so there is no need to be fooled that the airbag is soft and will not cause harm. Often, after opening the pillow, a person is left with scratches.

Some automakers indicate the service life of airbag elements. When a special signal appears, these components should be replaced before the signal lamp stops lighting.

Emerging problems

Front airbags are designed to protect people from adults. Since children are smaller, they are at risk of injury from its operation. Therefore, they should not occupy the front seat if the car has an Airbag for the passenger. The car should not have accessories installed that could limit the deployment of the Airbag or become a missile when it is deployed. Airbag systems usually have a warning light with an indicator. If the lamp does not go out immediately after starting or comes on while driving, check the owner's manual and have it checked by a workshop. The system has detected an error.

If you don't do this, the airbags may unexpectedly deploy during repairs, especially during electrical work. This can cause serious injury, so leave repairs to qualified personnel. The airbags deploy with explosive force and are far from the big fluffy airbags some people might imagine. It is not uncommon for minor injuries and abrasions to remain from contact with the pillow. Several vehicle manufacturers determine the lifespan of airbag components. Usually the airbag warning light comes on and components must be replaced before it goes off.

System malfunctions

The SRS system most often includes airbags, seat belts, collision detection sensors, squibs, tensioners, and a control unit. The latter is responsible for the proper functioning of the security system. It shows whether it is working properly. The “airbag” icon is located on the dashboard or on the steering wheel. What to do if this inscription starts to glow? In some cases, this indicates the need to repair the airbags in the car.

The control unit records all breakdowns that occur in the SRS; it automatically starts when you start the car. Sometimes the airbag sign lights up in cases where the control unit has not found any faults. When the car is started, you see the airbag indicator light, at this moment the control unit scans the system for a malfunction.

Typically, during testing, the indicator flashes from time to time, but no more than six times. When everything is in order with the system, the light stops glowing. If the indicator does not go out, it means that a breakdown has been detected and you need to visit a car service to fix it.

There are a huge number of reasons why the airbag system in a car is not working properly. We list those that occur most often:

• errors and system failures;
• airbag is broken;
• contacts and wiring have become unusable, connectors are connected incorrectly;
• breakdown of sensors;
• there is no signal from sensors, belts and airbags;
• the control unit has failed;
• the alarm was installed incorrectly, which led to a malfunction of the airbag system;
• terminals and fuses are disconnected or faulty;
• repair work in the car interior was carried out incorrectly;
• the airbag installation was completed with errors;
• after washing or cleaning, terminals, fuses, shock sensors or connectors were disconnected;
• The steering wheel was installed incorrectly.

What should I do if the airbag indicator lights up? First of all, we check the system when the ignition key is turned. If the light is on normally, then everything is in order. However, if a breakdown is detected, you should go to a car service center for a full check.

An experienced technician will use a scanner to diagnose the system. This device reads errors in the SRS system memory, recognizes the error code, and then suggests methods by which they can be corrected.

After this, it is necessary to repair the airbag in the car, taking into account the identified faults, or replace the airbag. Upon completion of the repair work, the control unit memory should be updated; this is the only way the system will work properly.

Have you noticed that your airbag light is constantly on? This problem should be dealt with as soon as possible so that driving the car does not pose a threat. In addition, the airbag system must be periodically serviced and diagnosed. This is the only way to reduce risks on the road.

Do airbag pillows have an expiration date?

Some car owners are negligent in diagnosing the operation of airbags. They are confident that the airbags installed from the factory will last the entire life of the car and will not need to be replaced. In reality, everything is completely different. And such irresponsible behavior can cost lives.

If you purchased a used car, you need to have the SRS system checked and also find out when the last diagnosis was made. This is important to do, since the service life of airbags on used cars is only 8–15 years. Once this period has expired, new airbags should be installed. Each airbag has a date on it when it was produced; you can see it by removing the airbag from the car.

If the airbag was manufactured on, the check must be performed more painstakingly, and it is best to install new airbags. The fact is that in 2002–2015, this plant skimped on safety parts by selling defective products. As a result, Takata's fraudulent actions were exposed.

If the car is new, then it is equipped with modern airbags, which do not need to be changed during its service life. However, do not forget that cars produced today are designed to last 5 years. After this period ends, the automaker is not responsible for anything that may happen. New cars have sensors that monitor the status of the SRS system.