Types, device and principle of operation of car airbags

One of the main elements of protection for the driver and passengers in the car are airbags. Opening at the moment of impact, they protect a person from collisions with the steering wheel, dashboard, front seat, side pillars and other parts of the body and interior. Since the airbags began to be installed in cars on a regular basis, they have been able to save the lives of many people who have been involved in an accident.

History of creation

The first prototypes of modern airbags appeared in 1941, but the war disrupted the plans of the engineers. The specialists returned to the development of airbag after the end of hostilities.

It is interesting that two engineers who worked separately from each other on different continents were involved in the creation of the first airbags. So, on August 18, 1953, American John Hetrick received a patent for a system of protection against impacts against solid elements in the passenger compartment invented by him. Just three months later, on November 12, 1953, a similar patent was issued to the German Walter Linderer.

The idea for a crash cushioning device came to John Hethrick after he was involved in a traffic accident in his car. His entire family was in the car at the time of the collision. Hetrik was lucky: the blow was not strong, so no one was hurt. Nevertheless, the incident made a strong impression on the American. The next night after the accident, the engineer locked himself in his office and began to work on the drawings, according to which the first prototypes of modern passive safety devices were later created.

The invention of engineers has undergone more and more improvements over time. As a result, the first production variants appeared in Ford cars in the 70s of the twentieth century.

Airbag in modern cars

Airbags are now installed in every car. Their number - from one to seven pieces - depends on the class and equipment of the vehicle. The main task of the system remains the same - to ensure the protection of a person from a collision at high speed with the elements of the car interior.

An airbag will only provide adequate protection against impact if the person is wearing the seat belts at the time of the collision. When the seat belts are not fastened, the activation of the airbag can cause additional injuries. Recall that the correct work of pillows is to accept a person's head and “deflate” under the action of inertia, softening the blow, and not flying out towards.

Types of airbags

All airbags can be divided into several types depending on their placement in the car.

1. Frontal. For the first time, such pillows appeared only in 1981 on cars of the German brand Mercedes-Benz. They are intended for the driver and the passenger sitting next to them. The driver's pillow is located in the steering wheel, for the passenger - on the top of the dashboard (dashboard).
2. Side. In 1994, Volvo began to use them. Side airbags are necessary to protect the human body in a side impact. In most cases, they are attached to the front seat backrest. Some car manufacturers also fit side airbags in the rear seats of the vehicle.
3. Head (have a second name - "curtains"). Designed to protect the head from impact at the time of a side collision. Depending on the model and manufacturer, these airbags can be installed between the pillars, in the front or rear of the roof, protecting passengers in each row of car seats.
4. Knee pads are designed to protect the driver's shins and knees. In some car models, devices to protect the passenger's feet can also be installed under the "glove compartment".
5. The central airbag was offered by Toyota in 2009. The device is designed to protect passengers from secondary damage in a side impact. The cushion can be located either in the armrest in the front row of seats or in the center of the back of the rear seat.

Airbag module device

The design is pretty simple and straightforward. Each module consists of only two elements: the pillow itself (bag) and the gas generator.

1. The bag (pillow) is made of a thin multi-layer nylon shell, the thickness of which does not exceed 0,4 mm. The casing is able to withstand high loads for a short period of time. The bag fits into a special splint, covered with a plastic or fabric lining.
2. The gas generator, which provides the "firing" of the pillow. Depending on the vehicle model, the driver and front passenger airbags can be single-stage or two-stage gas generators. The latter are equipped with two squibs, one of which releases about 80% of the gas, and the second is triggered only in the most severe collisions, as a result of which a person needs a harder pillow. Squibs contain material with properties similar to gunpowder. Also, gas generators are divided into solid fuel (consist of a body filled with solid fuel in the form of pellets with a squib) and hybrid (consist of a housing containing an inert gas under high pressure from 200 to 600 bar and a solid fuel with an igniter). The combustion of solid fuel leads to the opening of the compressed gas cylinder, then the resulting mixture enters the pillow. The shape and type of the gas generator used is largely determined by the purpose and location of the airbag.

Principle of operation

The principle of airbags is pretty simple.

• When the car collides with an obstacle at speed, the front, side or rear sensors are triggered (depending on which part of the body was hit). Typically, the sensors are triggered in a collision at speeds above 20 km / h. However, they also analyze the force of the impact, so that the airbag can be deployed even in a stationary car when it hits it. In addition to the impact sensors, passenger seat sensors can also be installed to detect the presence of passengers in the car. If only the driver is in the cabin, the sensors will prevent the airbags for passengers from being triggered.
• They then send a signal to the SRS electronic control unit, which, in turn, analyzes the need for deployment and transmits the command to the airbags.
• The information from the control unit is received by the gas generator, in which the igniter is activated, generating increased pressure and heat inside.
• As a result of the triggering of the igniter, sodium acid instantly burns out in the gas generator, releasing nitrogen in large quantities. The gas enters the airbag and opens the airbag instantly. The airbag deployment speed is about 300 km / h.
• Before filling the airbag, nitrogen enters a metal filter, which cools the gas and removes particulate matter from combustion.

The entire expansion process described above takes no more than 30 milliseconds. The airbag retains its shape for 10 seconds, after which it begins to deflate.

The opened pillow cannot be repaired or reused. The driver must go to the workshop to replace the airbag modules, actuated belt tensioners and the SRS control unit.

Is it possible to disable the airbags

It is not recommended to disable the airbags in the car by default, as this system provides important protection for the driver and passengers in the event of an accident. However, it is possible to shut down the system if the airbag does more harm than good. Thus, the pillow is deactivated if a child is transported in a child car seat in the front seat. Child restraints are designed to provide maximum protection for small passengers without additional attachments. A fired pillow, on the other hand, can injure a child.

Also, passenger airbags are recommended to be disabled for some medical reasons:

• during pregnancy;
• in old age;
• for diseases of bones and joints.

Deactivating the airbag, it is necessary to weigh the pros and cons, since in the event of an emergency, the responsibility for preserving the life and health of passengers will lie with the driver.

The passenger airbag deactivation pattern may vary depending on the make and model of the vehicle. To find out exactly how the system is deactivated in your car, refer to your car's manual.

Airbag is an important element of protection for the driver and passengers. However, relying on pillows alone is not acceptable. It is important to remember that they are only effective when used with seat belts fastened. If at the moment of impact the person is not fastened, he will fly by inertia towards the pillow, which is firing at a speed of 300 km / h. Severe injuries in such a situation cannot be avoided. Therefore, it is important for drivers and passengers to remember about safety and to wear a seat belt during every trip.

Questions and answers:

What is called an active vehicle safety system? This is a number of design features of a car, as well as additional elements and systems that prevent road accidents.

What types of security are used in the car? There are two types of safety systems used in modern cars. The first is passive (minimizes injuries in road accidents), the second is active (prevents road accidents).