The principle of ABS. Antilock braking system ABS. What is ABS in the car?

What is ABS (anti-lock system), or rather, as this abbreviation stands correctly, many drivers now know, but what exactly it blocks, and for what it's 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 production.

ABS is directly linked to the car's braking system, hence, to the safety of the driver, passengers, and all surrounding traffic participants. Therefore, to know how it functions will be useful to every driver. But in advance, in order to understand the principle of ABS, it is necessary to understand what "correct inhibition" 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 quickly braked 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 uniformly homogeneous, so the speed of their sliding will be different, and this is dangerous. The machine will cease to be controlled and go into a skid, which, if the driver has no 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 allow the wheels to lock rigidly and go to uncontrolled slipping. For this, there is a simple technique - intermittent braking. To do it, do not need to keep the brake pedal constantly in the pressed position, and periodically release it and press it again (as if pumping). Such seemingly simple action will not let the driver lose control of the car, as it will not allow the tire tread to lose grip on the ground.

But there is also a notorious human factor - the driver in an extreme situation can simply be confused and forget about all the rules. Here for such cases, and was invented ABS, 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 braking process of the car in a complex traffic situation (ice, wet road, etc.).

ABS is a good helper for a driver, especially a beginner, but you need to understand that it only helps in controlling the car, and does not control it, so you do not need to rely entirely on the "anti-block". The driver needs to study his car, its behavior on the road, when and how the ABS brake works, what is the length of the braking distance on different covers. Ideally, this should be checked at a specialized circuit, in order to avoid further trouble on the current road.

Something similar, but not yet ABS

The first mechanisms, the action of which resembled the principle of ABS, appeared at the beginning of the last century, only they were intended for aircraft chassis. A similar but already automotive system was developed by Bosch, a patent for which they received a patent in 1936. However, this technology was successfully introduced into a really working device only by the 1960s, when the first semiconductors and computers appeared. Moreover, General Motors, General Electric, Lincoln, Chrysler and others aspired to create a prototype ABS themselves, in addition to Bosch.

The first automotive ABS

• In the United States, what is ABS, or rather, its close analogue, was recognized in 1970 by the owners of Lincoln cars. The car was installed system, which the engineers of the company "Ford" began to develop as early as in 1954, but could "bring to mind" only to the 70th.
• Similar to the ABS mechanism in Britain, General Electric developed in conjunction with Dunlop. Tried it on a sports car Jenssen FF, it happened in 1966.
• In Europe, the concept of the "anti-lock system of the car" was learned thanks to Heinz Lieber, who developed it in 1964, working as an engineer at Teldix GmbH, and graduated in 1970, already working for Diamler-Benz. Created by him ABS-1 was tested in close cooperation with Bosch. Bosch, in turn, has already built its full-fledged ABS-2, which in 1978 was first installed on the Mercedes W116, and several years later on the BMW 7. However, in view of the high cost of the new braking system, it was used only as an option.

Full-scale serial production of cars with the "anti-block" began in 1992. It began to be installed on its products by some large automakers. And already since 2004 such a system began to equip all cars coming off the conveyors of European plants.

Elements of anti-lock system

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

• Electronic control unit.
• Speed sensors.
• The hydroblock.

The control unit (BU), in fact, is the "brain" of the system (computer), and what it performs functions is approximately understandable, but you need to talk more about the speed sensor and the hydroblock.

Principle of operation of the speed sensor

At the heart of the speed control sensors is the effect of electromagnetic induction. The coil with a magnetic core is immovably mounted in the wheel hub (on some models - in the reducer of the driving bridge).

A toothed crown is mounted in the hub, rotating together with the wheel. Rotation of the crown changes the parameters of the magnetic field, which leads to the appearance of an electric current. The magnitude of the current, respectively, depends on the speed of rotation of the wheel. And already, depending on its magnitude, a signal is generated, which is transmitted to the control unit.

Hydroblock

The hydroblock includes:

• Electromagnetic valves, divided into inlet and outlet, designed to adjust the pressure created in the brake cylinders of the car. The number of pairs of valves depends on the type of ABS.
• Pump (with the possibility of a return feed) - 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, operating principle

There are three main phases of ABS work:

1. Pressure relief in the brake cylinder.
2. Maintain constant pressure in the cylinder.
3. Increase the pressure in the brake cylinder to the required level.

First of all, it should be noted that the hydroblock in the car is integrated into the braking system in series, just behind the main brake cylinder. A solenoid valve is a kind of crane that opens and closes fluid access to the brake cylinders of the wheels.

The work and monitoring of the brake system of the car is carried out, in accordance with the data obtained by the ABS control unit from high-speed sensors.

After the start of braking, the ABS reads the readings from the wheel sensors, and smoothly reduces the speed of the car. If any of the wheels stops (starting to slide), the speed sensor instantly sends a signal to the BU. Having received it, the control unit activates the exhaust valve, which blocks the fluid access to the wheel brake cylinder, and the pump immediately starts its selection, returning it to the accumulator, thereby removing the lock. After the rotation of the wheel exceeds the specified speed limit, the "anti-block", covering the outlet and opening the intake valve, activates the pump, which starts to work in the opposite direction, pumping pressure into the brake cylinder, thereby braking the wheel. All processes are instantaneous (4-10 repetitions / sec.), And continue until the machine stops completely.

The above principle of ABS works refers to the most perfect - 4-channel system that performs a separate control of each wheel of the car, but there are other types of "anti-blocks".

Other ABS types

Three-channel ABS - this type of system contains three speed sensors: two mounted on the front wheels, the third - on the rear axle. Accordingly, and the hydroblock contains three pairs of valves. The principle of ABS of this type is in the separate control of each of the front wheels, and in the pair of rear wheels.

Two-channel ABS - in this system there is a pair control of the wheels located on one board.

A single-channel ABS sensor is mounted on the rear axle, and distributes the braking force to all 4 wheels simultaneously. Such a system contains one pair of valves (inlet and outlet). The magnitude of the pressure varies equally throughout the circuit.

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

How ABS works or ideal braking

Deciding to stop his car equipped with ABS, the driver, pressing the brake pedal, feels that it starts to vibrate slightly (the vibration can be accompanied by a characteristic sound resembling the sound of "ratchet"). This is a kind of report on the system that it has earned. The sensors read the speed indicators. The control unit monitors the pressure in the brake cylinders, preventing the wheels from rigidly locking, while quickly jerking them off. As a result, the machine gradually slows down and does not go to the user, which means that it remains manageable. Even if the road is slippery, the driver with such braking can only control the direction of the car until it stops. Thus, thanks to ABS, it turns out the ideal, and most importantly - controlled braking.

Unquestionably, the anti-lock system significantly facilitates the life of the driver, simplifying and increasing the efficiency of the braking process. However, it has a number of shortcomings that need to be known and taken into account in practice.

Disadvantages of ABS

The main disadvantage of ABS is that its effectiveness directly depends on the condition of the road.

If the roadway is an uneven, bumpy surface, then the car braking distance will be longer than usual. The reason for this is that during braking, the wheel periodically loses its grip on the road (jumps) and stops spinning. This stoppage of the wheel ABS regards as a lock, and stops braking. But when the contact with the road is restored, the specified braking program no longer corresponds to the optimal one, the system has to be rebuilt again, and this takes time, which increases the stopping distance. Reduce this effect by lowering the speed of the machine.

If the road surface is not uniform, with alternating areas, for example: snow is replaced by ice, ice - asphalt, then again ice, etc. In such an environment, getting on a slippery area, ABS, evaluating the coating, adjusts the braking process, On the asphalt "anti-block" again have to be rebuilt, because the selected braking force for a slippery surface on the asphalt becomes ineffective, this leads to an increase in the length of the braking distance.

With loose soil ABS is also not "friendly", in this case, the conventional brake system works much better, as the locked wheel brakes into the ground during braking, forming on its way a hill that prevents further travel and accelerating the stopping of the car.

At low speed, the "anti-block" is turned off altogether. Therefore, when driving on a slippery road going downhill, you need to be prepared for such an unpleasant moment, and keep in working order a "handbrake", which you can use if necessary.

In conclusion, I want to note that ABS is certainly a good addition to the braking system, which allows you not to lose control of the car during braking. However, one must always remember that this system is not all-powerful, and in some situations may render a disservice.