What is the working principle of automobile airbag generator?
Automobile safety can be divided into active safety and passive safety. Active safety refers to the automobile's ability to prevent accidents, while passive safety refers to the automobile's ability to protect passengers in case of accidents. When a car accident happens, the injury to passengers is instantaneous. For example, when a head-on collision occurs at a speed of 50 km/h, its occurrence time is only about one tenth of a second. In order to prevent passengers from being injured in such a short time, it is necessary to set up safety equipment. At present, there are mainly seat belts, anti-collision body and auxiliary inflatable restraint system (SRS).
Because many accidents are inevitable, passive safety is also very important. As a research achievement of passive safety, airbag has been rapidly developed and popularized because of its convenient use, remarkable effect and low cost.
Development history of airbag
Airbag has been patented since 1952, but it has gone through many twists and turns in its application and promotion, and has gone through a long road of more than 30 years. Until 1984, the automobile collision safety standard (FMVSS208) was re-recognized and implemented in the United States after being abolished many times. The standard stipulated that all cars manufactured after 1995 and 1 should be equipped with airbags in front of the front seats, and all new cars after 1998 should be driven. Today, this creative invention has been transformed into millions of products, and the types have also developed to front airbags, side airbags, airbags and so on. Most mid-to high-end cars produced in various countries are equipped with airbags, and some cars have included airbags as mandatory components. In China, with the implementation of CMVDR294 collision safety regulations, domestic consumers have higher and higher requirements for passive safety performance of automobiles, but at present, except for a few advanced cars equipped with side airbags, most models are only equipped with front airbags.
Composition of airbag system
The driver's Airbag is stored in the steering wheel pad, so when you see the words "SRS" or "airbag" on the steering wheel, you know that this car is equipped with airbags. The airbag system is mainly composed of sensors, microprocessors, gas generators and airbags. The sensor and the microprocessor are used for judging the collision degree and sending signals; The gas generator generates an ignition action according to the signal indication, ignites the solid fuel and generates gas to inflate the airbag, so that the airbag expands rapidly. The airbag is installed in the steering wheel hub near the seat cushion, and its capacity varies from about 50 liters to 90 liters. The fabric used for airbags has high tensile strength, mostly made of nylon, and the folded surface is stuck with dry powder to prevent airbags from sticking together and breaking when they explode. In order to prevent gas leakage, the inner layer of the airbag is coated with sealing rubber; At the same time, the airbag is equipped with a safety valve, which will automatically release some gas when it is inflated excessively or the pressure in the airbag exceeds a certain value, so as to avoid squeezing passengers and causing injuries; The gas used in the airbag is mainly nitrogen.
Working principle of airbag
A typical airbag system consists of two parts: an ignition device (or sensor) for collision detection and an airbag (or airbag) of a gas generator. When the sensor switch is started, the control circuit starts to work, and the detection loop is used to judge whether there is collision. If the signal comes from two sensors at the same time, the airbag will start to work. Because the generator and battery of an automobile are usually in the easily damaged parts of the front of the car, the control system of the airbag has its own power supply to ensure its function. After determining that the airbag deployment conditions are correct, the control loop will send current to the igniter, and the contained sodium nitride propellant will be heated and ignited instantly. At the same time, it will produce a large amount of harmless nitrogen-based gas, which will make the airbag expand to a full state. Through the powerful impact force, the cover on the steering wheel can be broken, and the airbag can be fully deployed to protect the driver's head from injury. At the same time, in the process of propellant ignition, the metal mesh cover in the igniter assembly can cool the rapidly expanding gas, and then the airbag can exhaust from the designed small exhaust port, which plays a role of gradual buffering and prevents the car body from blocking the line of sight after collision when it continues to move.
In particular, the sensor will only work when certain conditions are met. There are many sensor designs for airbags, some use pendulum or lever switches, some use spring wheels, and some products use mercury switches. But no matter what kind of sensor switch, it must have enough impact force to start the switch, and the impact force must come from the positive direction. Usually, this impact force is about equal to the result of hitting a fixed object at a speed of about 25 kilometers to 50 kilometers per hour. When the car is hit by this high-speed collision, the collision sensor installed at the front end of the car and the safety sensor installed in the middle of the car can detect the sudden deceleration of the car speed and quickly transmit this signal to the control computer of the airbag system. After computer analysis and confirmation, the electric igniter in the airbag bag will be detonated, which will make the airbag expand rapidly.
According to the calculation, the normal airbag must start working within 0.0 1 second after the automobile collision, the ignition device will start within 0.03 second, high-pressure gas will enter the airbag within 0.05 second, the airbag will expand outward within 0.08 second, and the airbag will fully expand within 0. 1 1 second. Only in this way will the driver hit the airbag.
It can be seen that whether the airbag opens or not is related to the impact angle and impact speed. Generally speaking, the airbag will not open when the car rolls over, slightly collides, collides from the side or collides from behind. For example, the upgraded version of Santana 2000 will only open the airbag if it is violently hit within 30 degrees from the front of the car. One more thing, regarding the impact speed, the airbag system measures the deceleration of the vehicle after the impact. Therefore, in the safety collision experiment, the vehicle usually hits the immovable and deformed wall directly.
Safety of airbag
Airbags can evenly distribute the impact force on the head and chest, prevent the fragile passengers from directly colliding with the car body, and greatly reduce the possibility of injury. Airbags can effectively protect passengers in a frontal collision. Even if you don't wear a seat belt, the anti-collision airbag is still enough to effectively reduce injuries. According to statistics, when a car with airbags collides head-on, the degree of passenger injury can be reduced by as much as 64%, and even 80% of passengers are not wearing seat belts! As for the collision between the side and the back seat, it still depends on the role of the seat belt.
In addition, when the airbag bursts, the volume is only about 130 decibels, which is within the human body's tolerance range; 78% of the gas in the airbag is nitrogen, which is very stable and harmless to the human body; The powder brought out during the explosion is lubricating powder to keep the airbag from sticking together in the folded state, which is harmless to human body.
Everything is a double-edged sword, and airbags also have their unsafe side. According to the calculation, if the car is driving at a speed of 60km/h, the sudden impact will stop the car within 0.2 seconds, and the airbag will pop up at a speed of about 300km/h, and the resulting impact force is about 180kg, which is unbearable for fragile parts of the human body such as the head and neck. Therefore, if the angle and strength of airbag ejection are slightly wrong, it is possible to brew a "tragedy".
Airbags have developed rapidly in recent years and their prices have dropped sharply. Cars equipped with airbags have also developed from middle and high-end cars to middle and low-end cars. At the same time, some cars are equipped with passenger airbags (double airbags) in the front row. The airbags used by passengers are similar to those used by drivers, but they are larger in size and need more gas. Since 1990s, the safety performance of airbag has been generally accepted and regarded as a modern advanced safety device. Understanding the working principle and precautions of airbags is very important for us to better protect ourselves, but for drivers, safe driving is the first priority, which is irreplaceable by any advanced safety device! Wang Peng/Wen
Do you know that?/You know what? Do you know that?/You know what? Do you know that?/You know what?
How was the airbag invented?
The airbag was invented by American john hurt Hotrich. He is a self-taught Pennsylvania engineer. 1952, after an accident, he came up with the idea of designing collision safety devices. In this accident, John slammed on the steering wheel brake to avoid obstacles. He and his wife instinctively protected their daughter sitting in the middle of the front seat with their arms. After the accident, he realized that there must be a good way to protect passengers. Two weeks later, he drew a design and gave it to the agent, which confirmed the prototype of today's airbag. 1953 18 obtained the American patent of "automobile buffer safety device" in August.
Airbags are disposable products.
Each airbag can only be used once, that is to say, as long as the airbag is detonated, it will no longer have the protection ability and cannot be plugged back for use next time. After the explosion, you must return to the factory to replace the new airbag. In the United States, it usually costs about $3,000 to reinstall a new airbag and sensor system and a complete set of computer controllers. Although expensive, but for the sake of life safety, these two money can not be saved!
Airbags should be used with seat belts.
Because airbags work by explosion, designers often look for the best scheme from most normal collision simulation tests, but in life, every driver has his own riding habits, which leads to the different positional relationship between people and airbags, which also determines the instability of airbag work. Therefore, in order to ensure that airbags really play a safe role, drivers and passengers must develop good driving habits and keep their chests at a certain distance from the steering wheel. The most effective measure is to fasten your seat belt. The airbag is only an auxiliary safety system, and it needs to be used in conjunction with the seat belt to maximize its safety protection.
Do not place objects in front of, above or near the airbag.
Be careful not to place items in front of, above or near the airbag, because these items may prevent the airbag from expanding or being thrown out in an emergency, causing greater danger. When installing radio, CD player and other accessories in the car room, you should abide by the regulations of the automobile factory, and do not modify the parts and circuits belonging to the airbag system at will, otherwise it will affect the airbag work.
When should I consider turning off the airbag?
If there are children among the passengers, you should pay special attention. Because airbag inflation may cause accidental danger to children in the front row, it is best to arrange children in the middle of the back row and fix them. Consider turning off the airbag switch when no one or children have to sit in the passenger seat.
When do you need to repair the airbag?
Pay attention to the airbag warning light on the dashboard. Under normal circumstances, when the ignition switch is turned to the "ACC" or "on" position, the warning light will light up for about 6 seconds and then go out. If the warning light is always on, it means that the airbag system is faulty and should be repaired immediately. Otherwise, the airbag may not work or pop up by mistake.
Key figures
0.0 1 sec
A normal airbag must start working within 0.0 1 s after a car collision, the ignition device will start within 0.03 seconds, high-pressure gas will enter the airbag within 0.05 seconds, the airbag will expand outward within 0.08 seconds, and the airbag will be fully inflated within 0. 1 1 s.