The principle of the ABS. Anti-blocking system ABS. What is ABS in a car?

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

What is ABS (anti-lock braking system), or rather, how this abbreviation is correctly deciphered, many drivers now know, but what exactly it blocks and why it is done, only very curious people know. And this despite the fact that now such a system is installed on most vehicles, both imported and domestic.

ABS is directly related to the braking system of the car, and therefore to the safety of the driver, passengers, and all surrounding road users. Therefore, knowing how it functions will be useful to every driver. But first, in order to understand the principle of the ABS, you need to understand what “correct braking” means.

The principle of "correct braking"

To stop the car, it is not enough just to press the brake pedal in time. After all, if you brake sharply during a fast ride, the wheels of the car will be blocked, and they will no longer roll, but slide along the road. It may happen that under all tires the surface will not be equally homogeneous, so their sliding speed will be different, and this is already dangerous. The car will no longer be controlled and will go into a skid, which, in the absence of the driver's skills, will be difficult to control. And an uncontrolled car is a potential source of danger.

Therefore, the main thing in braking is not to let the wheels lock up hard and go to uncontrolled slip. To do this, there is a simple trick - intermittent braking. To perform it, you do not need to keep the brake pedal constantly pressed, but periodically release and press it again (as if shaking). Such a seemingly simple action will prevent the driver from losing control of the car, as it will not allow the tire tread to lose traction.

But there is also the notorious human factor - a driver in an extreme situation can simply get confused and forget about all the rules. For such cases, ABS was invented, or in another way - anti-lock braking system.

What is ABS (ABS)

In a simple explanation, the ABS system is an electromechanical unit that controls the process of braking a car in difficult traffic conditions (icy, wet roads, etc.).

ABS is a good assistant for a driver, especially a beginner, but you need to understand that it only helps in driving the car, and does not control it, so you do not need to completely rely on the "anti-block". The driver needs to examine his car,its behavior on the road, in what cases and how the ABS brake works, what is the length of the braking distance on various surfaces. Ideally, this should be checked at a specialized circuit to avoid further trouble on a real road.

Something similar but not yet ABS

The first mechanisms, the action of which resembled the principle of the ABS, appeared at the beginning of the last century, only they were intended for aircraft landing gear. A similar, but already automotive system, was developed by the Bosch company, for which they received a patent for the invention in 1936. However, this technology was introduced into a truly working device only by the 60s, when the first semiconductors and computers appeared. Moreover, in addition to Bosch, General Motors, General Electric, Lincoln, Chrysler, and others also sought to create an ABS prototype on their own.

First automotive ABS

• In the USA, what is ABS, or rather, its close analogue, was discovered in 1970 by the owners of Lincoln cars. A system was installed on the car, which Ford engineers began to develop back in 1954, and were able to “bring it to mind” only by the 70th.
• An ABS-like mechanism was developed in Britain by General Electric in conjunction with Dunlop. We tried it on a Jenssen FF sports car, it happened in 1966.
• In Europe, the concept of "anti-lock braking system of a car" was recognized thanks to Heinz Lieber, who started its development in 1964 while working as an engineer at Teldix GmbH, and finished in 1970, already working for Diamler-Benz. Created by himABS-1 was tested in close collaboration with Bosch. Bosch, in turn, has already built its full-fledged ABS-2, which in 1978 was first installed on the Mercedes W116, and a few years later on the BMW-7. True, due to the high cost of the new braking system, it was used only as an option.

Full-fledged serial production of cars with "anti-block" began in 1992. Some major automakers began to install it on their products. And since 2004, all cars coming off the assembly lines of European factories have been equipped with such a system.

Elements of the anti-lock braking system

Theoretically, the ABS design looks simple and includes the following elements:

• Electronic control unit.
• Speed control sensors.
• Hydroblock.

The control unit (CU), in fact, is the "brain" of the system (computer), and what functions it performs is approximately clear, but we need to talk more about the speed sensor and the valve body.

How the speed sensor works

The operation of speed control sensors is based on the effect of electromagnetic induction. The coil with a magnetic core is fixedly mounted in the wheel hub (on some models - in the drive axle gearbox).

The hub has a ring gear that rotates with the wheel. The rotation of the crown changes the parameters of the magnetic field, which leads to the appearance of an electric current. current value,respectively, depends on the speed of rotation of the wheel. And already, depending on its value, a signal is generated that is transmitted to the control unit.

Hydroblock

Hydroblock includes:

• Solenoid valves, divided into intake and exhaust, designed to regulate the pressure created in the brake cylinders of the car. The number of valve pairs depends on the type of ABS.
• Pump (with the possibility of return flow) - pumps the desired amount of pressure in the system, supplying brake fluid from the accumulator, and, if necessary, taking it back.
• Hydraulic accumulator - storage for brake fluid.

ABS system, how it works

There are three main phases of ABS operation:

1. Release the pressure in the brake cylinder.
2. Maintaining constant cylinder pressure.
3. Increase the pressure in the brake cylinder to the required level.

First of all, it should be noted that the valve body in the car is built into the brake system in series, immediately after the master brake cylinder. And solenoid valves are a kind of tap that opens and closes fluid access to the brake cylinders of the wheels.

The operation and control of the vehicle's brake system is carried out in accordance with the data received by the ABS control unit from speed sensors.

After the start of braking, the ABS reads the readings from the wheel sensors, and gradually reduces the speed of the car. If any of the wheels stopped(begins to slide), the speed sensor instantly sends a signal to the control unit. Having received it, the control unit activates the exhaust valve, which blocks the access of fluid to the wheel brake cylinder, and the pump immediately begins to extract it, returning it to the accumulator, thereby removing the blockage. After the rotation of the wheel exceeds the predetermined speed limit, the “anti-block”, closing the exhaust valve and opening the intake valve, activates the pump, which starts to work in the opposite direction, pumping pressure into the brake cylinder, thereby slowing down the wheel. All processes are instantaneous (4-10 repetitions / sec.), and continue until the machine stops completely.

The above principle of ABS operation refers to the most advanced - 4-channel system, which separately controls each wheel of the car, but there are other types of "anti-blocks".

Other types of ABS

Three-channel ABS - this type of system contains three speed sensors: two are installed on the front wheels, the third is on the rear axle. Accordingly, the valve body contains three pairs of valves. The principle of operation of this type of ABS is to separately control each of the front wheels, and a pair of rear wheels.

Dual-channel ABS - in such a system, paired control of wheels located on one side takes place.

Single-channel ABS - the sensor is installed on the rear axle, and distributes the braking force to all 4 wheels at the same time. Such a system contains one pair of valves (inlet and outlet). The pressure is the same throughoutcontour.

Comparing the types of "anti-blocks", we can conclude that the difference between them lies in the number of speed control sensors and, accordingly, valves, but, in general, the principle of operation of the ABS on a car, the order of the processes occurring in it, is similar to all types of systems.

How ABS works or perfect braking

When the driver decides to stop their ABS-equipped vehicle, the driver feels that the brake pedal starts to vibrate slightly when pressing the brake pedal (vibration may be accompanied by a characteristic sound resembling the sound of a “ratchet”). This is a kind of system report that it has earned. Sensors read speed indicators. The control unit controls the pressure in the brake cylinders, preventing the wheels from locking rigidly, while slowing them down with quick “jerks”. As a result, the car gradually slows down and does not skid, which means it remains manageable. Even if the road is slippery, with such braking, the driver can only control the direction of the car until it comes to a complete stop. Thus, thanks to the ABS, it turns out perfect, and most importantly - controlled braking.

Of course, the anti-lock system makes life much easier for the driver, simplifying and increasing the efficiency of the braking process. However, it has a number of shortcomings that you need to know and take into account in practice.

Disadvantages of ABS

The main disadvantage of ABS is that its effectiveness is directly dependent on road conditions.

If the road surface is uneven,bumpy surface, then the car will have a longer braking distance than usual. The reason for this is that during braking, the wheel periodically loses traction (bounces) and stops spinning. The ABS considers such a stop of the wheel as a blockage and stops braking. But when contact with the road is restored, the set braking program no longer corresponds to the optimal one, the system has to be rebuilt again, and this takes time, which increases the braking distance. You can reduce this effect by reducing the speed of the car.

If the road surface is not uniform, with alternating sections, for example: snow turns to ice, ice to asph alt, then ice again, etc. the braking process, when switching to asph alt, the “anti-block” again has to rebuild, since the selected braking force for a slippery surface on asph alt becomes ineffective, this leads to an increase in the braking distance.

ABS is also not “friends” with loose soil, in this case, the conventional braking system works much better, since the locked wheel burrows into the ground during braking, forming a hill on its way, preventing further movement, and accelerating the stop of the car.

At low speed, the "anti-block" is generally disabled. Therefore, when driving on a slippery road going downhill, you need to be prepared for such an unpleasant moment, and keep the "handbrake" in good condition, which can be used in casenecessary.

In conclusion, I would like to note that ABS is certainly a good addition to the braking system, which allows you not to lose control over the car when braking. However, you should always remember that this system is not omnipotent, and in some situations it can do a disservice.