This system is a set of elements installed in the car, which can reduce the consequences of traffic accidents for the driver and passengers. At the moment, almost everyone, when buying a new car, can order an optional installation of a system from a dealer. It has become quite commonplace. But there are some 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 does it include? Find out the answers to these questions in our article today.
Components of the system
The SRS system may include the following components:
1. Seat belt (usually three-point and installed on each passenger and driver seat).
2. Belt tensioners.
3. Battery emergency disconnect.
4. Airbags (in the 90s they were considered an invisible luxury for motorists).
5. 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 cars have been equipped with pedestrian protection elements. On some models, there is even 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 clear-cut here. All items listed above are electronic control, which ensures the effective interaction of the various components of the SRS. What does it mean? Structurally, this system is a set of various measuring sensors, a control unit and actuators. The former perform the function of fixing the parameters at which an emergency occurs, and convert them into short electrical signals. These may include impact sensors, front row seat positions, and 3-point seat belt buckle switches. As a rule, the automaker installs 2 such devices on each side that react to shocks. Also, these sensors are closely related to active head restraints, which, when a signal is given, go into active mode. Thus, each of the components of the system passive safety closely interacts with certain sensors and, due to special impulses, in a matter of milliseconds allows you to inflate the airbag and its other components through the SRS unit.
Executing Devices
Among the performing devices in the car, the following should be noted:
- Belt tensioners.
- Pillow squibs.
- Head restraint mechanism.
- The control lamp on the instrument panel of the car, which signals the unfastened seat belts.
The activation of each of these components occurs in accordance with the software provided by the manufacturer.
What devices can be triggered in a frontal impact?
In a frontal collision, the SRS can activate several safety elements at once, depending on its strength. It can be both tensioners and pillows (possibly all together).
In a frontal-diagonal collision, depending on the angle and scale of the impact force, the following are activated in the system:
1. Belt tensioners.
2. Front airbags.
3. Pillows with tensioners.
4. 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 providing 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 car, either the belt tensioners or the side airbags may work. The latter are usually installed on cars of the middle and more prestigious classes. Budget cars are equipped only with tensioners, which are triggered upon impact, fixing the human body in the seat. Also, depending on the force of impact in the machine, the circuit breaker is activated. battery. Thus, in the event of a collision, the risk of a short circuit or the formation of a spark is completely reduced. This reduces the possibility of unauthorized ignition. vehicle as a result of a hole in the gas tank or other deformations of body elements.
What are active head restraints?
These elements began to be equipped on cars much later than the classic seat belt tensioners. Usually active head restraints are installed on the backs of the seats in the front and rear rows in the cabin. Due to the presence of such elements, the risk of a fracture in the cervical region during a rear 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 began to be installed on German Mercedes. According to their design, these head restraints are divided into two groups and can be both active and fixed. In the first case, the headrest is adjustable in height and angle. Motionless analogues are rigidly built into the seat backs. However, even such head restraints do an excellent job with their main function- reducing the risk of injury various types collisions.
Security systems that are equipped with modern cars fall into two main categories - active and passive. And it all started with the installation, which is now one of the main security tools. Belts belong to. The second most important passive means are airbags.
They are part of the SRS (Supplemental Restraint System - additional retention system), which includes a number of other devices and mechanisms.
Initially, pillows were positioned as an alternative to belts, which were previously not particularly comfortable to use. But practice has shown that only the combined use of these two means provides maximum injury safety.
Belts are now much more convenient to use, they provide good fixation of the body, but pillows have not been abandoned. And if earlier they were installed only on premium cars, now they are also available on cars budget segment. And the number of pillows is only increasing.
Main building blocks
The airbag system includes 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 security device.
shock sensors
Shock sensors are the 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 work. At first, only frontal sensors were used. The number of pillows was not large earlier and their task was to increase 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 designed so that in an accident only the necessary airbags are triggered, and not all at once. And for this it is necessary to determine the force of impact, its direction, nature. 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 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 causes the ball to move, overcoming the force of the spring, as a result, the contacts close and the impulse from the sensor goes to the control unit.
Electromechanical view of a band spring sensor
It should be noted that the stiffness of the spring 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 inertia 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 (condenser, inertial, pressure). Also, the design of electronic elements 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 fixed, the second is movable. Upon impact, the same force of inertia displaces the movable base with the plates relative to the fixed one. As a result, the capacitance of the capacitor sensor changes. This fixes the processing block, compares the received data with the table data and, based on this, generates a signal to the control block.
Capacitor Acceleration Sensor
Other types of sensors work according to this principle, the only difference comes down to their device. All of them change some parameters due to inertia, which is the basis for signal generation by the processing unit.
Note that the shock sensors are configured based on their installation location. So, the side elements are usually more sensitive than the front ones.
To detect an impact in the door area, sensors can be installed that detect 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 detecting pressure changes
The response speed of each type of sensor is also taken into account, so several types of them can be installed in the car at the same time. For example, pressure sensors are characterized by high speed, so they are often installed on the sides (in doors, racks).
The main advantage electronic sensors is to determine the nature of the blow - strength, direction. This is achieved by embedded tabular data in the processing unit.
Control block
The control unit receives information from the shock sensors and, based on them, sends signals to the required pillows. In fact, it is a distributor that directs the signal from the sensor to a specific pillow. But since the modern system often includes additional funds, then this block processes information from them as well, and also issues 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 condition of the working elements. For example, if an open circuit occurs, or the airbags have already worked, the unit will determine this, and on dashboard will light up control lamp, indicating that a security issue has occurred.
Note that it is not difficult to “bypass” the diagnostic mode, which is often used by motorists in whose cars the airbags are faulty or have worked.
gas generator
The main component of this system is the actuator - the 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 components - a squib, a charge of a substance that releases gas and directly to the pillow itself.
Steering wheel gas generator
The squib is designed to ignite the charge. He can do this in two ways - by melting the wire placed in the combustion chamber, or by using a capsule that creates a flame front in the chamber with a charge. It's simple - an electrical signal from the control unit is applied to the squib, which leads to the melting of the wiring or ignition of the primer.
The combustion chamber of the gas generator is filled with a substance that can burn out completely in the shortest possible time, releasing a large amount 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 decomposes into non-hazardous substances - nitrogen (45% of the total volume), water, carbon dioxide, solid particles.
It is worth noting that sodium azide burns completely very quickly (30-50 milliseconds, depending on the amount of substance), while burning is controlled, not explosive.
The resulting gas exits the gas generator through special channels 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 variety is a hybrid gas generator, the main substance in which is gas under pressure (argon - 98%, helium - 2%). It also contains a squib and a small amount of propellant charge. When it is triggered, the gas supply channel to the pillow opens. Hybrid gas generators differ in the design of the channel opening, due to the piston shifted by the charge at the moment of operation or destruction of the washer (membrane). There are other more rare designs.
Hybrid pressurized gas generator
The bag is usually made from nylon. For ease of deployment when inflated, the surface of the fabric is coated with talc, starch. The pillow must have perforations. The holes made in the bag are designed for blowing off after operation, and also fast (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 there are two squibs and two combustion chambers. The peculiarity of such a generator is the sequential activation of squibs.
Upon impact, the charge in the main chamber ignites first. In this case, the filling of the pillow occurs at 80%. That is, the bag is softer than when completely filled, which reduces injury when a person contacts the pillow. After a certain period of time, the squib of the auxiliary chamber is activated, and the pillow is filled with gas, but only after it has taken the blow of the body.
Additional funds
The device of the SRS system may additionally include a sensor for determining the presence of a passenger, an emergency lowering mechanism for the door windows. The control unit can also manage the operation of belt tensioners (with squibs).
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, this pillow was turned off manually, which was not very convenient. Installing the sensor solved the problem with a forgotten passenger airbag turned on or off.
Passenger seat device
The mechanism of emergency lowering of glasses is intended for elimination of pneumoshock. With the windows closed, the unfolding of the pillows leads to a rapid decrease in the volume of the passenger compartment (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 quite powerful and passengers can easily get damage to the eardrums. The mechanism of the emergency lowering of the side windows eliminates the increase in pressure and the appearance of a pneumatic impact.
The seat belts of many cars are now equipped with pretensioners, which provide short-term belt tension in an accident, ensuring the fixation of the body and eliminating its inertial movement. Moreover, the pretensioners are equipped with squibs, the operation of which is carried out from an impulse supplied from the airbag control unit.
Principle of operation
Knowing the design and functioning of all the components, it is not difficult to understand the principle of operation of the airbag: in the event of a collision, the sensors pick up 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, and also activates the pretensioner squibs (if any) and turns on the window lowering mechanism (if any).
The signal received from the block to the gas generator leads to the actuation of the squib and the charge chemical agent lights up. The released gas enters the bag, which unfolds and then immediately descends due to perforation.
Diagram of the SRS system Audi A3
Note that the main disadvantage of pillows is their disposability. That is, they work only once, after which they need to be changed. And the replacement is very expensive, so the car owners of the car on which they worked use a “trick” so that the system is normally diagnosed when the engine is started and does not bother with a constantly burning warning light.
Kinds
Used on modern cars 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 backs of the front seats);
- Head, they are also curtains (placed in the side racks or the roof).
These types of airbags are installed on many models, including budget options. Frontal are designed to reduce injury 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 front and side airbags are usually designed only to ensure the safety of the driver and front passenger. But curtains can also be installed in the rear of the cabin to reduce injury to passengers in the back seat.
There are other types of airbags, but they are much less common. These include knee and central. The first are located under the front panel and provide protection for the legs. The central cushion pops up between the front seats and is aimed at preventing injury in the event of a collision between the driver and passenger.
Airbags have proven to be really effective, so systems are 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), softening the force of a pedestrian's impact on the structural elements of the car.
AutoleekAt the moment, almost everyone, when buying a new car, can order an optional installation of a system from a dealer. It has become quite commonplace. But there are some 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 does it include? Find out the answers to these questions in our article today.
Characteristic
SRS - what is it? This system is a set of elements installed in the car, which can reduce the consequences of traffic accidents for the driver and passengers. According to its classification, the SRS Airbag belongs to the structural elements of safety. This means that all its components are installed not as an option (as may be the case with an air conditioner), but without fail. And it doesn’t matter if it’s a top-end or “base” package, both cars will still contain the same set of passive safety devices.
Thus, SRS is a collection structural elements, which are used to protect passengers and the driver from injury in an accident.
Components of the system
The SRS system may include the following components:
- Seat belt (usually three-point and installed on each passenger and driver seat).
- Belt tensioners.
- Battery emergency disconnect.
- (in the 90s they were considered an invisible luxury for motorists).
- Active headrests.
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 (as on convertibles), additional attachments for child seats, etc.
Recently, many cars began to be equipped with pedestrian protection elements. On some models, there is even 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 clear-cut here. All of the elements listed above are electronically controlled to ensure efficient interaction between the various components of the SRS. What does it mean? Structurally, this system is a set of various measuring sensors and actuators. The former perform the function of fixing the parameters at which an emergency 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 automaker installs 2 such devices on each side that react to shocks. Also, these sensors are closely related to active head restraints, which, when a signal is given, go into active mode.
Thus, each of the components of the passive safety system closely interacts with certain sensors and, due to special impulses, in a matter of milliseconds, allows you to inflate the Airbag and its other components through the SRS unit.
Executing Devices
Among the performing 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 in a frontal impact?
In a frontal collision, the SRS can activate several safety elements at once, depending on its strength. It can be both tensioners and pillows (possibly all together).
In a frontal-diagonal collision, depending on the angle and scale of the impact force, the following are activated in the system:
- Belt tensioners.
- Front airbags.
- Pillows 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 providing 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 car, either the belt tensioners or the side airbags may work. The latter are usually installed on cars of the middle and more prestigious classes. Budget cars are equipped only with tensioners, which are triggered upon impact, fixing the human body in the seat.
Also, depending on the strength of the impact in the car, the battery disconnector is activated. Thus, in the event of a collision, the risk of a short circuit or the formation of a spark is completely reduced. This reduces the possibility of unauthorized ignition of the vehicle as a result of a hole in the gas tank or other deformations of the body elements.
What are active head restraints?
These elements began to be equipped on cars much later than the classic seat belt tensioners. Usually active head restraints are installed on the backs of the seats in the front and rear rows in the cabin. Due to the presence of such elements, the risk of a fracture in the cervical region during a rear 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 began to be installed on German Mercedes. According to their design, these head restraints are divided into two groups and can be both active and fixed. In the first case, the headrest is adjustable in height and angle. Motionless analogues are rigidly built into the seat backs. However, even such head restraints do an excellent job with their main function - reducing injury risk in various types of collisions.
So, we found out what the SRS system is in a car and how it works in various collisions.
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 needs to be done if the SRS indicator on the dashboard lights up.
Deciphering what is the SRS system in a car
SRS (short for Supplementary Restraint System) is a security system for the driver and passengers in the car, which works in emergency situation(in the event of a frontal or side collision of a vehicle with a moving or static object).
The SRS system 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, fixing the moment of impact in a collision, the position of people in the car, etc.;
- Front and side airbags;
- Special pretensioners for seat belts.
Note: the SRS security system in a car helps to preserve the health, and sometimes the life of the driver and passengers in case of accidents, while the system is triggered at a car speed of more than 50 km / h in frontal 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 to do if the SRS light on the dashboard is on?
Drawing conclusions from the above, it immediately becomes clear that it is imperative to monitor the state of the SRS system (CPC) 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 the specialists in the car service so that they can diagnose and fix this problem.
The SRS security system is good because it does not need to be serviced often, it is enough to carry it out every 9-10 years complete diagnostics to make sure it good work, but it is important not to forget that airbags and squibs for them are disposable and if they are triggered in an emergency, they must be completely replaced.
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 more closely monitor its condition. Your reviews and helpful tips on the topic of what SRS is in a car, leave it in the comments to the article and share it in in social networks if it was helpful to you.
Airbag in literal translation from English is an air bag, but in Russian the name airbag has been assigned to the SRS passive safety system, consisting of many components.
SRS system - Supplemental Restraint System literally translated from of English language The Supplemental Restraint System consists of many different devices, mechanisms, electronic gauges 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 during an accident not all devices work 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 strength, the contacts of the sensors are closed and the electronic impulses from the sensor are sent to the control unit.
The SRS control unit receives information from impact sensors and sends electrical signals to trigger various actuators: air bags, seat belt squibs. For example, an airbag deploys in conjunction with the seat belt to reduce the chance of injury to the driver and front passenger from any part of the car body. In many car models, the airbag will not deploy if the passenger or driver is not wearing a seatbelt. But lately, various plugs of security locks have been especially popular with some drivers. Most often they are bought when they are too lazy to buckle up, and the constant buzzer of the signaling device for not fastened seat belts bothers with its squeak. The operation of a vehicle equipped with AIRbags with an unbelted driver or passenger is prohibited. In the event of an accident in a frontal impact, an unbelted driver or passenger can be hit in the head by an airbag much stronger than on the dashboard. The speed of the deploying airbag can reach 300km/h. Maximum safety and effectiveness from deployed airbags in a collision is only possible if the driver and front passenger are wearing their seat belts.
Airbag deploy speed can reach 300km/h
The SRS control unit, in addition to ensuring safety while driving, also performs the self-diagnosis function of the security 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 igniter connector, an open circuit has occurred, the airbag has previously deployed or is simply removed, the indicator light on the dashboard lights up, warning the driver of a malfunction in 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)
- No 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 shock sensors in the doors or in the car body
- blown fuse
- Resetting the memory of the SRS block when trying to reflash after an accident