Airbag crash sensor: device, features and functions

Author: Ivan Baranov

Airbags (Airbags) are an integral element of the safety system of any modern vehicle. Therefore, in order to protect themselves and passengers while driving, the driver must always monitor the performance of this system. What functions does the airbag sensor perform and how to determine a malfunction in the system - find out from this material.

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Requirements for PD

Airbags installed in a vehicle must meet the following minimum requirements:

• Must be filled with gas composition at a certain speed.
• Gas must also leave the PD at a certain speed.
• The pillow must have a volume that ensures the safety of the passenger.
• The device must be of the required shape and geometry.
• Correct placement of airbags in the car interior.
• Inflating the pillows at certain moments.

Features of transporting children

Transporting children in a car equipped with airbags is a special driving mode. This is because deployed air bags can cause serious injury or even kill a child who is not wearing a seat belt.

That is why experts were united in developing special requirements for transporting children in a car with air bags.

Firstly, it is recommended to transport children only in a well-secured special seat and only in the back seat. » alt=»»> Secondly, if it is impossible to turn off the front passenger airbag, transporting children under 1 year in the front seat is excluded.

Thirdly, if you are driving with a child in a special seat in the front seat, the latter must be moved as far back as possible.

Required Items

Car airbags are a combination of the following elements:

• Pillow shell.
• The gas composition with which it is filled.
• Gas-forming substances.
• Side airbag crash sensor G179.
• Car seat position sensor.
• Driver side airbag crash sensor G179.
• Seat occupancy sensor.
• PB impact sensors located along the windshield, etc.
• Electronic control unit for this security system.

Additional funds

The SRS system device may additionally include a sensor for detecting the presence of a passenger and an emergency lowering mechanism for door windows. The control unit can also control the operation of belt pretensioners (with squibs).

A passenger detection sensor is needed so that the control unit does not activate the front passenger airbag if there is no one in the side seat. Previously, turning off this airbag was done manually, which was not entirely convenient. Installing the sensor solved the problem with the passenger airbag being forgotten on or off.

Passenger seat arrangement

The emergency window lowering mechanism is designed to eliminate pneumatic shock. When the windows are closed, the deployment of the pillows leads to a rapid decrease in the volume of the cabin (it is filled with bags). As a result, the air pressure in the cabin increases sharply and a pneumatic shock is formed, which is quite powerful and passengers can easily damage their eardrums. The mechanism for emergency lowering of the side windows eliminates the increase in pressure and the occurrence of pneumatic shock.

The seat belts of many cars are now equipped with pretensioners, which provide short-term tension of the belt during an accident, securing the body and eliminating its inertial movement. Moreover, the pretensioners are equipped with squibs, which are triggered by an impulse supplied from the airbag control unit.

Varieties

Airbag crash sensors are not the only sensors in the SRS system. It is assumed that they work systematically together with other elements. Here the following stands out:

• Airbag crash sensor.
• Sensor for the presence of passengers in the vehicle.
• Satellite sensor.

Let's get to know them in more detail.

How to check a car before buying

You can check the car's history before purchasing using online services. For example, through the all-Russian Internet service “Autocode”. Here you can get information in 5 minutes about whether the vehicle you are interested in was involved in an accident or not. If the car has been in a serious accident, it means that the safety devices have already been activated. But they replaced them with new ones or installed a dummy - it’s up to the potential buyer to check.

To become the owner of information about road accidents in which the car was involved, enter the VIN or state registration number. vehicle number in the search form on the main page of the Autocode website. Within five minutes you will receive information about the type and date of the traffic accident. In addition, the diagram will indicate the location of the most significant damage to the body.

In addition, a detailed report contains information about the former owners of the car, the history of registration actions, the actual mileage of the car, the dates of technical inspections, information about the presence of traffic police restrictions and other useful information about the vehicle.

To be completely sure of the desired swallow, you should inspect it for any technical problems. However, if you do not have enough experience, or you are in another city, an auto expert will do it for you! To do this, just leave a request for an on-site inspection service on the Autocode website.

Shock sensor

Many car owners are interested in where the airbag impact sensors are located. But not everyone knows their purpose.

It also consists in detecting a collision and transmitting the corresponding impulse to the system control device. The design of such a sensor can be very different. It depends on the model of a particular car.

A common example is an electromechanical controller. Accordingly, in a certain situation it will close its contacts. What happens next? When the contacts close, current begins to flow through them. As a result, this leads to the activation of actuators. They are already initiating the filling of airbags with a special gas composition.

We looked at how the airbag impact sensor works. But we must remember that to initiate his actions, only a strong blow is needed. Only then will the process be started.

In the event that at the time of a road accident there is a disruption in the battery power supply, the power banks will still work - they will be filled with gas. What is the reason for this? The system contains a special capacitor device that can accumulate charge.

Gas generator squib

The melting wire or flame front within the ignition element (primer) energizes the airbag gas generators. In modern designs, the capsule for igniting the gas generator is triggered by alternating current in order to prevent the occurrence of a short circuit in the vehicle's electrical DC power system (malfunction in the electrical wiring). To create alternating current, a capacitor is incorporated into the charging capsule and connected in series to the drive circuit, which charges, discharges, or recharges at approximately 100 kHz.

The gas generator, often called a squib (tablet) with a diameter of 10 cm and a thickness of 1 cm, uses crystals of solid fuel, the combustion of which releases gas that fills, or rather, inflates the pillow. The fuel is usually poisonous sodium azide (NaN3), 45% of the mass of which, when burned, turns into pure nitrogen, and the rest into carbon dioxide (CO2), carbon monoxide (CO), water (H2O) and particulate matter. An electrical impulse ignites the squib or melts the wire and the crystals turn into gas. The signal for triggering the squib is an electrical impulse from shock sensors (acceleration or pressure), arriving directly or through an electronic unit. Although the combustion process occurs quickly, it is not explosive. Combustion occurs in 3 stages: ignition, ignition for the fuse and combustion of the working charge. In a very short time the system develops power up to 60 kW, but no explosion occurs. Fuel combustion and inflation of the airbag with a volume of approximately 50...60 liters for the driver lasts 30...35 ms, the airbag for the passenger with a volume of approximately 100...140 liters is installed in the glove compartment area and inflates in approximately 50 ms. This time is less than the time it takes to blink an eye, which is 100 milliseconds.

To prevent injuries from inflating the driving pillow at a speed of 200...300 km/h towards the chest, modern pillows are inflated in two stages: first by about 70%, and when in contact with the body completely, two-stage gas generators are used for this.

Thanks to the radial straightening of the air bag and the sequential ignition of charges in such gas generators, the load that acts on the driver in an accident is significantly reduced. Depending on the severity and type of accident, the interval between the activation of both squibs can be approximately 5 ms. up to 50 ms. Both charges are always fired to eliminate cases when, after deployment of the airbag, there remains another squib that has not fired.

Sensor location

So where are the airbag crash sensors located? It all depends on the model of a particular car. The most common examples of controller layouts are here:

• Airbag control device.
• Inside the salon.
• In some cases, in the engine compartment of a car.

Where are the airbag crash sensors located? In the case of foreign cars, there is another additional shock sensor - this is to turn off the fuel pump. It often causes problems - in the event of a minor impact, the airbags do not deploy, but at the same time, the car cannot be started until this sensor is activated.

Renault Fluence 2011, engine Gasoline 1.6 liter., 106 hp, Front drive, Manual — parts

Comments 24

hi, tell me where this airbag unit is located on Renault Fluence... I can’t find and start the car... please tell me

Because of this, the car cannot start. It is in the central tunnel where the gearbox and handbrake are.

How to start it, please tell me

hi, tell me where this airbag unit is located on Renault Fluence... I can’t find and start the car... please tell me

How to start it in this case?

I can’t understand, did your belts work after the accident or did they stall? We had such a case, the airbags and service were on the display, they wanted to change the unit safely, in the end they just removed the errors with a clip.

the squib in the belts went off. I took them off and knocked out the balls. and the pillows are intact. They said that it was impossible to flash the block and forced me to buy everything. I’ll give the old block to my master - he will dig it up, otherwise maybe the servicemen are cheating)

Really flash it. I myself work at a dealer in Renault. Our diagnostician does.

Their senior mechanic friend dissuaded me from doing so. but I’ve already given the block to a local guru - we’ll see... I hope I won’t have to do it again)

Really flash it. I myself work at a dealer in Renault. Our diagnostician does.

hi, tell me where this airbag block is located on Renault Fluence... I can’t find and start the car... please tell me... the car won’t start after an accident, they say the block needs to be flashed...

I’ll fix your phone and show you a photo of Vova))) the culprit is in complete trouble) you’ll change your mind) the car is surprisingly strong

I will identify you by IP and spit in your mailbox! do not write me anymore!))

I’ll spit, it’s not scary... if you shit