At the moment, almost everyone, when buying a new car, can order an optional installation of any system from a dealer. It has become quite commonplace. But there are options that are already included in the package, and you do not need to pay extra for them.
Among these is the SRS system. What is it and what components are included in it? You will find out the answers to these questions in the course of our today's article.
Characteristic
SRS - what is it? This system is a complex of elements installed in a car that can reduce the consequences of road accidents for the driver and passengers. According to its classification, SRS Airbag belongs to the structural elements of safety. This means that all of its components are not installed optionally (as may be the case with an air conditioner), but without fail. And it doesn't matter if it is a top-end configuration or a "base", all the same, both machines will contain the same set of devices passive safety.
Thus, the SRS is a set of structural elements that are used to protect passengers and the driver from injury in an accident.
System components
An SRS system can include the following components:
- Seat belt (usually three-point and is installed on each passenger and driver's seat).
- Belt tensioners.
- Emergency battery disconnector.
- (in the 90s, they were considered an invisible luxury for motorists).
- Active head restraints.
Depending on the make and model of the machine, the SRS may include a number of other devices. For example, it can be a rollover protection system (like on convertibles), additional attachments for child seats, etc.
Recently, many vehicles have begun to be equipped with pedestrian protection elements. Some models even have an emergency call system.
SRS Passive Safety Management
We have already found out what kind of system it is, now let's look at how it is controlled. But not everything is so simple here. All items listed above have electronic control, which allows the various components of the SRS to communicate effectively. What does it mean? Structurally this system is a set of various measuring sensors and actuators. The first ones perform the function of fixing the parameters at which an emergency situation occurs, and convert them into short electrical signals. These can be the seating positions of the front row of seats and 3-point lock switches.As a rule, the car manufacturer installs 2 such devices on each side, reacting to impacts. Also, these sensors are closely associated with active head restraints, which, when given a signal, go into active mode.
Thus, each of the components of the passive safety system closely interacts with certain sensors and, using special pulses, in a matter of milliseconds, it allows the Airbag and its other components to be inflated through the SRS unit.
Executing devices
Among the executing devices in the car, the following should be noted:
The activation of each of these components occurs in accordance with the software provided by the manufacturer.
What devices can be triggered by a frontal impact?
In a frontal collision, the SRS can activate several safety elements at once, depending on its strength. These can be both tensioners and pillows (possibly all together).
In case of a frontal-diagonal collision, depending on the angle and scale of the impact force in the system, the following are activated:
- Belt tensioners.
- Front airbags.
- Cushions together with tensioners.
- Left or Right Airbag.
In some cases (usually at speeds over 60 kilometers per hour), the system can activate all of the above elements, thereby ensuring maximum safety and minimal risk of injury to passengers in both rows of seats, as well as to the driver himself.
What devices can be triggered in a side impact?
In this case, depending on the equipment of the vehicle, either the belt tensioners or the side airbags can be triggered. The latter are usually installed on cars of the middle and more prestigious classes. Budget cars are equipped only with tensioners, which are triggered on impact, fixing the human body in the seat.
Also, depending on the force of the impact in the machine, a breaker is triggered battery... Thus, in the event of a collision, the risk of a short circuit or spark formation is reduced altogether. This reduces the possibility of unauthorized ignition. vehicle as a result of a hole in the gas tank or other deformations of body parts.
What are active head restraints?
These elements began to be completed on cars much later than the classic seat belt tensioners. Typically, active head restraints are installed on the backrests of the seats in the front and rear rows in the passenger compartment. Due to the presence of such elements, the risk of fracture in the cervical region during a posterior impact is reduced to a minimum (and this area is one of the most vulnerable to fractures). Thus, active head restraints significantly increase the chances of life, even with seemingly fatal blows. The first copies of such devices were installed on German Mercedes. By their design, these head restraints are divided into two groups and can be either active or fixed. In the first case, the headrest can be adjusted in height and angle. Immobile analogs are rigidly built into the seat backs. However, even such headrests do an excellent job with their main function - reducing the risk of injury when different types collisions.
So, we found out what the SRS system is in a car and how it works in various collisions.
Experienced drivers who own modern cars are well aware of what SRS is in a car. However, sooner or later, novice motorists have to find out about this, since it often happens that on their dashboards " iron horses»The indicator lights up, indicating a malfunction of this system. Why this happens and how to do it will be described below, but it makes sense to start with a general overview of the design of the SRS system, as well as understand how it functions.
The abbreviation SRS stands for Supplementary Restraint System, and it stands for the active safety system of the vehicle. It is she who is responsible for the state of all the elements that should ensure the protection of the driver and passengers of the vehicle in the event of various emergency situations.
The SRS system includes components such as:
- Airbags (front and side);
- Touch sensors that track the position of people in the car in real time;
- Acceleration and shock sensors;
- Seat belt pretensioners;
- Control modules;
- SRS main module;
- Active head restraints.
In addition, connecting cables, self-contained power supplies and connectors are also structural elements of the SRS system.
Frontal airbags are located directly in front of the driver (in the steering wheel) and front passenger (in the dashboard), while side airbags are located on the sides, in the seatbacks and side body elements. In their design, there are special pyrotechnical cartridges filled with dry gas and triggered by electrical impulses.
The sensors (pressure sensor and backrest position sensor) are located in the seats, and the acceleration sensor (often called the overload sensor) is located in the front of the car, directly behind the grille. It is designed like a pendulum, and if its position changes abruptly as a result of a collision, it closes the electrical circuit, thus generating a control signal that is transmitted to the main SRS module.
In most cases, it is located in the tunnel channel (or rather, in the front of it), and its most important function is to control such elements of the SRS system as airbag modules and seat belt pretensioners. The latter, in the same way as the sensor sensors, are located in the front seats, equipped with pistons with pyrotechnics: when triggered, they are the ones that are set in motion and very quickly tighten the belt. It goes without saying that the active head restraints are also located on the seats, being mounted in the upper backrests.
How SRS works
It should be noted that the SRS system is distinguished by a very high response speed, and this is what allows it to preserve the health, and sometimes the life of the driver and passengers of the vehicle in the event of serious accidents. When a vehicle traveling at a speed of more than 50 km / h hits an obstacle, an inertial sensor is triggered. It completes the electrical circuit, as a result of which the control signal is sent to the main SRS module. Through it, it is transmitted to the airbag modules, as a result of which they are deployed within 300 milliseconds.
At the same time, a signal is sent via the main airbag module to the belt pretensioners as well as to the active head restraints. As a result, the seat belts are instantly tightened more so that the person does not move forward by inertia, but remains in place. Active head restraints are moved forward to prevent so-called whiplash injuries to the neck.
It should be noted that the main SRS module, having received a trigger signal from the acceleration sensor, sends it to central locking car. This is done to unlock the doors and provide free access to the vehicle for rescuers.
The vehicle's SRS system is configured in such a way that it is only triggered when the vehicle is actually emergency situation NS. It does not work, for example, when colliding with bushes or snowdrifts. If it detects a rear impact, then the activation signal is sent only to the active head restraints, and if the impact follows from the side, then only the side airbags are triggered (in those cases, of course, if they are installed on the given car).
SRS system maintenance
The SRS system does not require frequent maintenance, but it should undergo a full diagnosis once every ten years. After the airbags have deployed, they must be completely replaced, since they are disposable. When operating the SRS system, it is necessary to ensure that its elements (especially sensors) do not heat up above +90 ° C.
It must also be remembered that the degree of effectiveness of this passive vehicle safety system largely depends on how correctly the driver and passengers are positioned in its cabin. For the seat belts and active head restraints to work properly, the seat backs must be tilted no more than 25 °. In addition, the seats should not be moved too close to the airbags.
SRS errors
As mentioned above, the SRS system is quite complex in design, and therefore, various errors can periodically occur in its operation. As practice shows, they are most often caused by such reasons as:
- Faulty wiring or contacts;
- Problems with the electronics of the control modules;
- Disconnected terminals and blown fuses.
Whatever the cause of the SRS error, it is strongly discouraged to try to fix it yourself. It is best to go to the station when it occurs Maintenance... Its specialists will conduct a thorough diagnosis of the system and fix the problem.
Video on the topic
The safety systems with which modern cars are equipped are divided into two main categories - active and passive. It all started with the installation, which is still one of the main security tools. Belts belong to. The second most important passive means are airbags.
They are part of the Supplemental Restraint System (SRS), which includes a number of other devices and mechanisms.
Initially, the pillows were positioned as an alternative to the belts, which were not very comfortable to use in the past. But practice has shown that only the complex use of these two means provides maximum injury safety.
The belts are now much more convenient to use, they provide a good fixation of the torso, but they have not given up pillows either. And if earlier they were installed only on premium cars, now they are also available on cars of the budget segment. And the number of pillows is only increasing.
Main building blocks
The airbag system has three main components:
- Shock sensors
- Control block
- Gas generators
More modern systems include additional sensors and mechanisms that make certain adjustments to the operation of the safety device.
Shock sensors
Impact sensors are elements on which the operation of the entire system depends. It is they who determine that a collision has occurred, due to which the pillows are deployed. At first, only front sensors were used. Previously, the number of pillows was not large and their task was to increase injury safety in frontal collisions. Now, many cars are equipped with side devices, so the number of sensors has increased.
An example of the location of the shock sensors of the SRS system
The operation of the entire system is built in such a way that in the event of an accident, only the necessary pillows are triggered, and not all at once. And for this it is necessary to determine the force of the blow, its direction, character. This is provided by sensors installed in different parts of the body - in the front, doors, pillars.
Electromechanical type sensors are considered traditional. They are quite simple in design, but at the same time they are quite effective. The main elements of such a sensor are a ball and a spring of a certain stiffness. It works like this: upon impact, inertia forces the ball to move, overcoming the force of the spring, as a result, the contacts close and the pulse from the sensor goes to the control unit.
Electromechanical view of the strip spring sensor
It is worth noting that the spring rate is significant. This eliminates false alarms of the system, for example, during emergency braking, a slight impact with an obstacle. So, in a collision while driving at low speed (up to 20 km / h), the airbag will not work, since the inertial force will simply not be enough to overcome the spring force.
In addition to electromechanical sensors, electronic types are also used on cars, the main element of which is an acceleration sensor (capacitor, inertial, pressure). Also, the design of the electronic components includes a signal processing unit from the acceleration sensor.
Inertial sensor device
The principle of operation of a capacitor acceleration sensor is reduced to a change in capacitance due to displacement of the plates. And this is achieved by separating the capacitor plates and fixing them on different bases, one of which is stationary, the second is mobile. Upon impact, the same inertial force displaces the movable base with the plates relative to the stationary one. As a result, the capacitance of the capacitor sensor changes. This fixes the processing unit, verifies the received data with the tabular data and, on the basis of this, generates a signal to the control unit.
Acceleration capacitor sensor
Other types of sensors work according to this principle, the only difference comes down to their device. All of them, due to inertia, change any parameters, which is the basis for signal generation by the processing unit.
Note that the shock sensors are configured based on their installation location. Thus, lateral elements are usually more sensitive than frontal ones.
To detect a blow to the door area, sensors can be installed that record changes in atmospheric pressure in the car doors. They are piezoelectric or capacitive. The first type is based on the piezoelectric effect, and the second on the principle of a capacitor sensor.
Shock sensors fixing pressure changes
The response speed of each type of sensor is also taken into account, therefore, several types of them can be installed simultaneously in the car. For example, pressure sensors are fast-acting, so they are often installed on the sides (in doors, racks).
The main advantage of electronic sensors is to determine the nature of the impact - force, direction. This is achieved due to the embedded tabular data in the processing unit.
Control block
The control unit receives information from the shock sensors and, on the basis of them, sends signals to the required airbags. In fact, it is a distributor that directs the signal from the sensor to a specific pillow. But since a modern system often includes additional means, this unit processes information from them, and also gives commands to trigger certain mechanisms.
The control unit is also involved in system diagnostics. After starting the engine, it sends control signals to the actuators, determining the integrity of the electrical circuit and the state of the working elements. For example, if there is an open circuit, or the pillows have already worked, then the unit will determine this, and on dashboard The warning light will illuminate to indicate that there is a security problem.
Note that it is not difficult to "bypass" the diagnostic mode, which is often used by motorists, in whose cars the pillows are faulty or triggered.
Gas generator
The main component of this system is an actuator - a gas generator. Its task is to generate a large amount of gas in a short time, which then fills the pillow itself.
The gas generator includes several constituent elements - an igniter, a charge of a substance that emits gas and directly the pillow itself.
Gas generator in the steering wheel
The igniter is designed to ignite the charge. He can do this in two ways - by melting a wire placed in the combustion chamber, or by means of a capsule that creates a flame front in the chamber with a charge. It's simple - an electrical signal from the control unit is fed to the igniter, which leads to melting of the wiring or ignition of the capsule.
The combustion chamber of the gas generator is filled with a substance that can completely burn out in the shortest possible time, while releasing a large volume of gas that is safe for humans. Sodium azide is usually used as such a substance (which, by the way, is poisonous). But in the process of combustion, it breaks down into non-hazardous substances - nitrogen (45% of the total), water, carbon dioxide, solid particles.
It should be noted that sodium azide completely burns out very quickly (30-50 milliseconds, depending on the amount of substance), while the combustion is controlled, not explosive.
The resulting gas through special channels leaves the gas generator and enters the fabric bag. Before that, it is filtered through a special metal filter that removes solid particles and also cools the gas.
Hybrid gas generator with charge and gas
Another type is a hybrid gas generator, the main substance in which is gas under pressure (argon - 98%, helium - 2%). It also has a squib and a small amount of propelling charge. When it is triggered, the gas supply channel to the pillow is opened. Hybrid gas generators differ in the design of the channel opening, due to the piston displaced by the charge at the moment the washer (membrane) is triggered or destroyed. There are other rarer designs as well.
Hybrid pressurized gas generator
The bag is usually made of nylon. For ease of deployment when inflating, the surface of the fabric is covered with talcum powder, starch. There is always a perforation in the pillow. The holes made in the bag are designed to deflate after triggering, and also quickly (1-2 seconds). This eliminates suffocation and trapping of passengers in the car.
Airbag deployment
Often, on modern cars, the airbag device includes a two-chamber gas generator, in which two squibs and two combustion chambers. The peculiarity of such a generator is the sequential activation of the squibs.
On impact, the charge in the main chamber is ignited first. In this case, the filling of the pillow is 80%. That is, the bag is softer than when completely filled, which reduces trauma when a person comes into contact with the pillow. After a certain period of time, the auxiliary chamber igniter is triggered, and the pillow is refilled with gas, but after it has taken a hit from the body.
Additional funds
The SRS system device may additionally include a sensor for detecting the presence of a passenger, an emergency lowering mechanism for door windows. The control unit can also control the operation of the belt pretensioners (with igniters).
The passenger presence sensor is needed so that the control unit does not activate the front passenger airbag if there is no one on the side seat. Previously, disabling this pillow was done manually, which was not very convenient. Installing the sensor solved the problem with the forgotten enabled or disabled passenger airbag.
Passenger seat device
The emergency lowering mechanism is designed to eliminate pneumatic impact. With the windows 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 rises sharply and a pneumatic shock is formed, and it is powerful enough and passengers can easily get damage to the ear membranes. The mechanism of the emergency lowering of the side windows excludes an increase in pressure and the appearance of a pneumatic shock.
The seat belts of many cars are now equipped with pretensioners, which provide short-term belt tension in the event of an accident, ensuring body fixation and eliminating its inertial movement. Moreover, the pretensioners are equipped with squibs, which are triggered by a pulse supplied from the airbag control unit.
Principle of operation
Knowing the design and functioning of all the constituent elements, it is not difficult to understand the principle of the airbag: in a collision, the sensors catch the impact and send a signal to the control unit. That, in turn, redirects the impulse to the desired gas generator. At the same time, the unit detects the presence of a passenger and decides whether to use the passenger airbag, as well as activates the pretensioner squibs (if any) and activates the window lowering mechanism (if any).
The signal from the unit to the gas generator triggers the squib and the chemical charge ignites. The released gas enters the bag, it unfolds and then immediately descends due to perforation.
Audi A3 SRS system diagram
Note that the main disadvantage of pillows is their disposability. That is, they only work once, after which they need to be changed. And the replacement is very expensive, so the car owners, on which they worked, use the "trick" so that the system is normally diagnosed when the engine is started and does not get bored with a constantly burning warning lamp.
Views
Modern cars use different types airbags. The main ones are:
- Frontal driver's and passenger's (installed in the steering wheel and front panel);
- Side (mounted in the front seat backs);
- Head, they are curtains (placed in the side racks or roof).
These types of airbags are fitted on many models, including budget options. Frontal ones are designed to reduce injuries in frontal impacts, the other two types - in side impacts. Moreover, the side ones protect the torso, and the curtains protect the head. It is noteworthy that the front and side airbags are usually only designed to provide injury protection to the driver and front passenger. But the curtains can be installed in the rear of the passenger compartment to reduce injury to passengers in the back seat.
There are other types of airbags, but they are much less common. These include the knee and center. The former are located under the front panel and provide foot protection. The center airbag pops up between the front seats and is aimed at preventing injury in a collision between the driver and passenger.
Airbags have proven to be really effective, so systems are now being actively developed that are aimed at reducing injury to pedestrians in a collision with a car. To do this, pillows are installed in the front of the car (in the bumper and in front of the windshield) to soften the force of the pedestrian's impact on the structural elements of the car.
AutoleekAirbag literally translated from English is an air bag, but in Russian the name airbag is stuck behind the SRS passive safety system, which consists of many components.
System SRS - Supplemental Restraint System literally translated from of English language The Supplemental Restraint System consists of many different devices, mechanisms, electronic sensors and sensors. Any airbag system consists of front and side impact sensors, an SRS control unit, squibs and gas generators. The operation of all sensors and devices is interconnected with each other. It is important that in the event of an accident, not all devices are triggered at the same time, but only the necessary pillows and belts. Sensors located in different parts of the car body record the impact, the direction of the impact, its force, the contacts of the sensors are closed and electronic pulses from the sensor are sent to the control unit.
The SRS control unit receives information from the shock sensors and sends electrical signals to trigger various actuators: air bags, seat belt squibs. For example, the airbag is deployed in conjunction with the seat belt, reducing the likelihood of injury to the driver and front passenger from any part of the car body. In many car models, the airbag will not work if the passenger or driver is not wearing a seatbelt. But recently, some drivers have been particularly popular with various safety lock plugs. Most often they are bought when you are too lazy to fasten your seatbelts, and the constant buzzer of the warning device of unfastened seat belts annoys you with its squeak. It is prohibited to operate a vehicle equipped with AIRbag with the driver or passenger not wearing a seatbelt. In the event of an accident in a frontal impact, an unbuckled driver or passenger may be hit in the head by an airbag much stronger than against the dashboard. The deployment speed of the airbag can reach 300 km / h. Maximum safety and effectiveness from deployed airbags in a collision is only possible when the driver and front passenger are wearing seat belts.
The airbag deployment speed can reach 300 km / h
The SRS control unit, in addition to ensuring safety while driving, also performs the function of self-diagnosis of the safety system. When starting the car engine, the SRS unit diagnoses the integrity of the actuators, the health of the airbags, the integrity of the electrical circuits and elements. If there is no contact in the seat belt squib connector, there is an open circuit, the airbag was previously deployed or simply removed, an indicator lamp on the dashboard lights up, warning the driver about a problem with the AIRbag system.
The main reasons why the AIRBAG indicator on the dashboard may light up:
- Violation of the integrity of one of the elements of the system (sensor, device, mechanism)
- Lack of signal in the electrical circuit of the system
- Disconnected or poor contact in one of the connectors
- Damage to wiring due to short circuit
- Damage to the impact sensors in the doors or in the car body
- Blown fuse
- Resetting the memory of the SRS unit when trying to reflash after an accident
In many modern cars there is an SRS system, but not many people know what it is and what this abbreviation means, so in this article we will try to figure out what SRS is in a car and what to do if the SRS indicator on the dashboard lights up.
Decoding what is the SRS system in a car
SRS (short for Supplementary Restraint System) Is a safety system for the driver and passengers in the car, which is triggered in an emergency (in case of a head-on or side collision of the car with a moving or static object).
The SRS includes the following components to ensure the safety of the driver and passengers:
- SRS system module;
- Special sensors and sensors that track the speed of the car, fix the moment of impact in a collision, the position of people in the car, etc .;
- Front and side airbags;
- Special seat belt tensioners.
Note: the SRS safety system in a car helps to maintain the health, and sometimes the life of the driver and passengers in accidents, while the system is triggered at a vehicle speed of more than 50 km / h about head-on and side impacts.
Also, do not forget that SRS will not work in a collision with soft objects (for example, when entering a snowdrift), as well as in a rear impact (for example, if another car crashed into your car from behind).
What if the dashboard SRS light is on?
Drawing conclusions from the above, it immediately becomes clear that it is imperative to monitor the state of the SRS system (SRS) in the car, since your safety depends on it.
If an error starts to appear (a signal is triggered on the dashboard with the SRS icon), then it is better to quickly contact a car service specialist so that they can diagnose and fix this problem.
The SRS safety system is good in that it does not need to be serviced often, it is enough to carry out its full diagnostics once every 9-10 years to make sure that it is working properly, but it is important not to forget that the airbags and squibs for them are disposable and if they are triggered in an emergency, their complete replacement is required.
In conclusion to the article, it can be noted that knowing what SRS means in a car and how important this system is, in the future you will closely monitor its condition. Your reviews and useful tips on the topic of what is SRS in the car, we leave it in the comments to the article and share it on social networks if it was useful to you.
