Research and development trend of two-stage gas ge

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Research and development trend of two-stage gas generator for airbag

airbag has gas generators of different specifications. In case of vehicle collision, the gas generator inflates the airbag and deploys it to protect the safety of passengers. Since the first batch production of safety airbag in 1986, the gas generator technology has also developed from a single-stage type using sodium azide as the gas generator to a two-stage gas generator using a new solid gas generator, and the generated stored gas is heated in an instant, or as the "heated gas inflator" specially developed by Trinasolar (TRW), It makes the pressurized gas burn, thus producing a large amount of hot gas to fill the airbag. In recent years, passenger injury accidents have occurred from time to time due to the relevant coordination deviation between the airbag and passengers in the process of use, leading world-famous airbag manufacturing companies such as Trinasolar (TRW) to explore new ways to develop more accurate airbag inflation. Among them, the two-stage gas generator has a good development prospect. There are many types of two-stage gas generators. Generally speaking, the "two-stage" gas generator is equipped with two initiators to selectively produce different amounts of gas in different periods of time. In fact, the deployment time between the two pilots can be changed according to different combinations, so as to obtain an adjustable series of gas generation (which can be called "multi-stage" gas generator)

up to now, there are usually the following types of two-stage gas generators

two stage pyrotechnic gas generators, which are equipped with two independent integral gas generators connected end to end

the two-stage storage gas generator is composed of a separate gas tank and has the ability to obtain different gas release by changing the opening amount of the two pilots

whether the gas generator commonly referred to as "booster" meets its own needs. Some gas storage generators are equipped with small gas pyrotechnic devices combined with one or more igniters. This device heats the gas delivered to the gas generator, and relies on this heating method to increase the pressure of the gas in the airbag. In the two-stage storage gas generator, the amount of single-stage gas is mainly determined by the specifications of the vehicle itself and the performance evaluation standards of the vehicle manufacturer. In the two-stage gas generator, the ratio of the first stage to the second stage gas generation is 70:30, 60:40 and 50:50. Each vehicle model needs to be analyzed and tested to determine what combination method is most suitable for the design needs of the vehicle manufacturer

different levels of airbag deployment

in the two-stage gas generator airbag, the determination of inflation deployment time is a method to meet the needs of various working conditions of inflation and expansion. For example, the first stage gas generator is activated only when the sensor system detects the beginning of a car collision and decides that the airbag must enter operation. In the first stage (i.e. the first stage), when the gas generator starts to work at a low collision speed, if the sensor system further detects that the vehicle collision is serious, it will immediately start the gas generator to enter the second stage (the second stage), especially in the short time of the first stage, which can enhance our confidence within 5 - 1 OMS. If the sensor system does not detect a high crash severity, it will delay the start of the second stage (second stage)

in some vehicles, the delay of the second stage gas generation is usually applied in the "medium" serious collision with a delay time of 30 ~ 70ms. If the collision is a "low" severity event, only the first stage gas generator will be started. Of course, in order to ensure the adaptability of the gas generator, it is necessary to control (dispose) and ensure the safe operation during the transformation. The second stage gas generation is often carried out 100 ~ 125ms after the collision event. During this period, the passenger has been restrained by the airbag and bounced back on the vehicle seat. At this time, the second stage inflation and deployment of the airbag will have minimal impact on the passengers

the gas generator is triggered by the on-board collision sensor, which includes a central control module and is related to the unique shape of the vehicle itself. It can also include different kinds of acceleration sensors and other detection devices distributed on the vehicle

the sensor system must have an algorithm called collision severity judgment. According to this logic control algorithm, it can predict the severity of collision events and make different decisions on the severity of different collision accidents. Nowadays, the more advanced collision severity judgment algorithm developed successfully has been applied. It includes more stable microprocessor chip technology suitable for vehicles. These algorithms can apply not only input information from acceleration sensors, but also information from seat belt buckle switches and passenger sensing systems, such as occupant weight or existing sensors

the common misunderstanding of collision sensor is that it can reflect the vehicle speed through the collision sensor to determine the severity of collision. In fact, it can only reflect the acceleration state of the vehicle, because the acceleration of the vehicle is directly proportional to the severity of the collision accident. A typical example illustrates this point, that is, the relationship between a car and a pile or a brick wall. In the above two cases, the car collides with the target at the same speed, but the results are very different. Enable the vehicle sensor system to "see" the severity of the collision in a very short time. When a vehicle collides with an object, it will produce a deceleration acceleration (and negative acceleration), which is usually proportional to the severity of the collision. A greater acceleration means a more serious collision. That is to say, a sensor system needs to "wait" for a limited period of time in order to "see" how serious the collision is before predicting the necessity of airbag triggering. If the collision severity is predicted to be low, only the first stage gas generator will be triggered. If a serious collision accident is predicted, the second stage gas generator will be triggered. This requires the system to respond quickly, usually within the first 20ms of the beginning of the collision, while the whole collision is within 500ms (1/2 of 1 second), which is only equivalent to human blinking 2-3 times (it takes about 200ms for human blinking once)

performance of two-stage gas generator

the energy required for occupant restraint protection in vehicle collision accidents will change significantly in the whole collision range. The kinetic energy of the passenger is in direct proportion to the product of the weight (mass) of the passenger and the square of the speed. In this way, due to the speed change of the collision, the energy required to restrain the passenger increases by the square of the speed. For example, when the speed increases from 32.18km/h (20 miles/h) to 48.27km/h (30 miles/h), the energy control value is greater than twice. Similarly, the situation of heavy passengers is very different from that of light passengers, and the energy control value of occupant protection also changes with the weight of passengers

the two-stage gas generator is a powerful tool that enables engineers to better cooperate with passengers in specific collision situations. The statistical analysis of traffic accidents indicates that 75% of the samples with good breakpoints in almost all crashes belong to low crash severity. Only the first level gas generator needs to be triggered to protect the passengers, while the second level gas generator needs to be triggered in case of a serious crash to reduce the injury to the passengers


like the world's famous automotive safety system suppliers, TRW company is a supplier in the world with many core technologies such as airbags. Its initially developed passenger side airbag two-stage gas generator is used in the BMW 5 series of 1999 model year, and the original driver side airbag is also used in the Volvo V70 of 2001 model year Mercedes Benz m ◆ 1. Bio based high molecular material composition level and Jaguar XK8 models. The application and promotion of these devices are fast, and today the two-stage gas generator has been applied to almost all models in the United States and Europe

the first generation of two-stage gas generator is expensive, but like all parts on cars, its price soon fell with mass production. Today, TRW is developing the third and fourth generation of two-stage gas generators, such as pp15. This design shows the rapid progress of two-stage gas generator and the important role played by TRW in this rapid progress

the above shows the development history and latest progress of TRW gas generator. Similarly, in other countries, there have been different types of gas generator airbags used in cars. (end)

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