Principle of operation ABS by car. How the ABS is working (ABS anti-lock system). How everything functions

The system of interest to us passed on cars back in the late 1970s, so she passed the test. Currently, the absence of ABS in the staff configuration is rare. It significantly increases safety on the roads and partly reduces the demands on the driver skills. In any case, under the control of ABS, even inexperienced chances of avoiding an emergency.

In power interest

The ABS task is to maintain controllability with emergency braking. It is known that the blocked wheel with the coating of the road is lower than that of the cargo, the brake forces created by them are less, and there are no controls at all. At best, the car slides directly, at worst - on an uncontrolled trajectory with an unpredictable result. ABS also controls the operation of the wheel on the border between the maximum possible (under concrete) clutch and breaking into blocking, not allowing it to develop. Of course, the clutch coefficient itself with an ABS expensive does not depend. On ice, it may be times ten times lower than on dry asphalt, it means that the car's handling will be different. But in both cases ABS provides maximum possible. With a fairly fine tuning, it is capable of acting even more efficiently than the driver-speaker.

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The ABS operation relies on the wheel slip factor - the ratio of the velocity difference of the vehicle and the wheel speed to the velocity of the car. In various driving modes, the speed of the transportation of the car and the circumferential velocity wheel may not coincide. With intensive acceleration, the driving wheel speed is higher than the speed of the machine, during a slowdown - on the contrary. Naturally, the 100 percent slippage corresponds two modes - blocking the wheels when braking or stopping in place. Meanwhile, the best clutch of the coating tire and, therefore, the maximum transmission of the brake force is achieved with the degree of slippage of the wheels about 20%. Here ABS and supports this value at the level of 15-20%.

ANATOMY

The hydraulic circuit of the ABS module includes solenoid valves and pump. In conventional braking, the valves are not involved, the necessary pressure controls the driver's foot. But when slipping with the risk of blocking the wheel is included by ABS.

Modern ABS four-channel: This layout makes it possible to control the pressure in the brake system separately for each wheel. All circuits of the system work in a similar way in three modes - retention of pressure, its reduction and increase. With the proximity of the wheel to blocking, the system switches to pressure retention mode. The valves cut off the wheel caliper from the main brake cylinder - now the pressure of the fluid on the pistons is constant, regardless of the Press force on the pedal. But when slipping above 20%, the system reduces pressure using a pump, throwing out part of the liquid from the caliper to the main brake cylinder. When slipping becomes lower than a certain threshold, the system moves to an increase in pressure: the valves open up - and when the pedal is pressed, the pressure grows. These modes alternate until the situation changes: the braking is interrupted or substantially weakened and the slippage is not either the vehicle speed fell below 5-15 km / h (depending on the system settings). This alternate change of modes of operation and causes itching on the brake pedal. The high - leg frequency is even the best driver-pro person cannot compete in speed with ABS! When braking ABS supports slipping all wheels at one level to save the course stability. On the mix (for example, the left wheels of the car on the asphalt, and the right-wing ice) system will maintain a straight line, adjusting the pressure in the circuit of each wheel depending on the clutch of this wheel with a coating. Braking without ABS will lead to the inside of the car towards the coating with the best clutch, and when the wheels are blocked, it will reach the turn.

Almost the most important elements of ABS are wheel speed sensors. According to their impulses, the speed of each wheel is calculated and compared with the vehicle speed. Based on this information, the ABS module calculates and holds slipping of each wheel in the required level.

The selection of the designer uses passive or active sensors. Passive easy to identify on a gear ring (comb) on the wheel drive. It is very simple: when the comb rotates, the sensor displays an analog voltage signal. But, alas, with a low wheel speed, such a sensor does not give a clear signal, may be wrong.

The active sensor reads the magnetic ring labels on the hub bearing. It is characterized by a clear digital signal in the form of consecutive voltage pulses, the value of which does not depend on the rotational speed of the wheel. But the frequency of impulses reflects this speed.

All-wheel drive cars in ABS included additional G-Sensor with accelerometer longitudinal accelerations. It sends an acceleration or deceleration signal to the ABS module, taken into account when calculating the car speed correction coefficient. After all, under certain circumstances, it is impossible to measure the speed with the desired accuracy.

FORCE MAJEURE

There is nothing perfect in the world, and ABS is no exception. Conservationability is sometimes paid by increasing the brake path. If ABS is effective with a good clutch of all four wheels with an expensive, then non-standard situations are possible on the problematic coverage. The irregularities of the road leaf (comb, tram paths, etc.) cause bounce of the wheels, and when the suspension malfunction is possible, even a temporary separation of the wheel from the coating is possible. At such moments of the wheels are very unloaded, which leads to their early blocking during coincidence and, accordingly, to early ABS triggering. The same effect of early trigger is observed in the areas of asphalt, covered with sand, mud, gravel or on a naked ice. The worst scenario - departure from the road. Without ABS blocked wheels might bite the coating, at least somehow quit speed. With ABS, the braking path is greatly increasing, and in the case of braking in the drift, the car greatly leads along the arc. In December 2013, SPETSTES was described in December 2012, in which braking indicators were compared from a speed of 60 km / h on a smooth asphalt and on a comb. Two tested machines of three braking paths on the comb increased by 40%!

Better not to risk

ABS disabling is not provided. But you can get rid of it by driving a fuse. Most often do that when they go to strain on the ice trail. However, it should be remembered that modern ABS is also responsible for the distribution of brake forces on the axes with ordinary braking (earlier, independent mechanical regulators were instituted). In case of disabling ABS, any normal braking can lead to blocking the rear wheels with all the consequences arising from here.

Cabinet Therapist.

ABS has a failure indicator lamp. Provides and read fault codes. You can also track the parameters of the elements and control some of them - for example, valves and pump of the ABS module. It is best to use dealer diagnostic equipment. The system is quite reliable and includes not too many elements. Most of ABS faults are associated with external influences.

Module management errors.

Most often it is internal electronic malfunctions of the module. Sometimes such errors are random, that is, after removal, no longer arise. If errors are not deleted or reused, the control module is subject to replacement: repair is not provided.

Errors of wheel speed sensors.

Possible causes - from the fault of the wiring to the sensor itself. If an active sensor is used, the malfunction can be due to the increased backup of the hub bearing (too large an air gap between the sensor and the magnetic ring on the bearing) or the fact that when the bearing is replaced, it is simply applied not to that side. When using a passive sensor, the problem can create a comb on the drive: during the replacement of the wheel bearing or when removing the drive, it could be slightly shifted from the landing space. The signal of this sensor is sometimes weakening due to the accumulated dirt or metal particles on the ridge. Both sensors are afraid of strong vibrations, but especially - active. Because of this, the sensor is sometimes impossible to remove without damaging, because the hammer strikes are not even on it, and near! - Create it to destroy.

Today, new cars are equipped with the most different systemsWith the help of which even newcomers can easily cope with control. One of the very first systems is considered anti-lock brake system. The ABS system is installed even in basic equipment cars. This is an electromechanical block, which is in such complex road situations as slippery, wet path or ice, manages the braking of the vehicle. In essence, this is the right hand of the driver, the more newcomer.

Proper braking without ABS

Each driver should be aware that it is not enough to use the brake pedal in time. Since if at high speed to pull the brake to the brake, then the wheels of the car are blocked, as a result of which there will be no clutch wheels with a road surface. Road coating can be different, therefore, the slip speed will be different. As a result, the vehicle ceases to be manageable and can easily go into skid. If the owner of the car is inexperienced, then the control of the direction of the car may not be possible to be issued.

The most important thing in such braking is to prevent the wheels to be firmly blocked, as a result of which the vehicle goes into a skid. To avoid such cases, it is recommended to use discovery of intermittent braking. To carry out such proper braking, it is necessary to press the brake pedal periodically with a small interval, then you cannot keep the brake pedal pressed until a complete stop. With such a simple braking technique, you can control the car despite the quality of the road surface.

However, it is necessary to take into account the simple human factor - the driver in an unforeseen situation is able to be confused and all the deceleration rules can simply fly away from his head. To control the vehicle in such emergency situations And the anti-lock braking system was developed.

What is the secret of the work of ABS

It is important to know what principle the ABS works, because it has a close connection with the control system, which means that, respectively, with the security level of the route and passenger. So, the main idea of \u200b\u200bthe system of the system is that when the driver rises a brake pedal, an instantaneous control occurs, and the braking force is redistributed on the wheels. Through this, the car is manageable in any conditions, and the effect of reduced speed is achieved. However, it is impossible to rely only on various additional systems because the driver should be mastered its own car - the length of the braking path and behavior in emergency situations. It is recommended to test the abilities of the car on specialized autodromes, in order to prevent delicate situations on the road in the future.

There are still some features of the ABS work. For example, when the chauffeur decided to stop the movement of the car equipped with the ABS system, then when the brake pedal is pressed, there is a light vibration on the pedals, and the accompanying sound can be heard. Vibration and sound is a sign that the system has earned. In the meantime, the sensors read the speed indicators, and the control unit ensures pressure control inside the brake cylinders. Thus, it does not allow the locking of the wheels, and slows down with fast jerks. Due to this, the speed of the car is falling, and at the same time it does not go into a skid, which allows you to control the vehicle until the stop. Even with a slippery road, with the ABS system, the driver only needs to keep the direction of the car under control. Such ideal and manageable braking is possible only thanks to the ABS system.

The following stepships should be emphasized:

1. Dropping pressure in the brake cylinder.
2. Support for continuous pressure in the cylinder.
3. An increase in pressure to the corresponding level in the very brake cylinder.

It is important to know that the hydraulicock in the vehicle is mounted in the brake system in a row right after the main brake cylinder. As for the electromagnetic valve, this is a kind of crane that admits and blocks the inflow of the liquid substance to the brake cylinders themselves.

Control, as well as the working processes of the braking system of the car are carried out in consent with the information that entered the ABS control unit from the speed sensors.

When the braking process, ABS decrypts information from the wheel speed sensors, thanks to which the vehicle speed evenly falls. In case of stopping any wheel, the signal is instantly sent from speed sensors to the control unit. Accepting such a signal, the control module removes the lock due to the activation of the exhaust valve, which blocks the inlet of the liquid substance into the wheel brake cylinder. At this point, the pump returns the liquid into the hydroaccumulator. When the wheel turnover is increased to a permissible speed, the control unit will give the command to cover the graduation and open the inlet valve. After that, the pump is launched, which will pump pressure in the brake cylinder, with the result that the wheel will continue to slow down. These processes are performed instantly, and last until the final stop of the vehicle.

The discussed essence of the ABS works is the most new four-channel system, in which all vehicle wheels are controlled.

Other famous types

1. The single-channel consists of a sensor located on the back bridge whose task is to distribute the brake force synchronously into four wheels. This kind of system has only one pair of valves, due to which the pressure completely varies completely throughout the contour.
2. Two-channel - it takes steam control of wheels, which are located on one side.
3. Three-channel consists of three speed sensors: one is mounted on the back bridge, and the rest are mounted on the front wheels separately. In the mentioned form of the system there are three pairs of valves (intake and graduation). The action of this type of ABS consists in an individual control of the front wheels and in the pair of the rear.

Comparing different types ABS, it can be concluded that their difference is manifested only in a different number of valves themselves and speed control sensors. However, the essence of the system in the vehicle, as well as the order of the flowing processes is identical to all types of systems.

History of system implementation

Engineers leading automobile companies Diligently practiced by ABS in the first half of the 70s. Even the very first systems were quite successful, and already at that decade, such systems began to install in mass production cars.

Initially, mechanical sensors were mounted on the cars only on the same axis, which sent data to the control module on pressure change in brake circuits. Developers with Germany made another step forward in this area and began to use sensors without contacts, and this, in turn, catalyzed the transfer of information to the logical block. In addition, the number of false positives has decreased, and due to the fact that rubbing surfaces eliminated, wear disappeared. In the same principle that was used in the first anti-lock systems, a modern system works.

Component anti-lock system

The hypothetical structure of the ABS is absolutely simple, and consists of the following devices:

• hydrelclock
• speed \u200b\u200bsensors
• block electronic control

The latter plays the role of "intelligence" of the system (computer), so it is not difficult to imagine what he guides the role. As for the speed control sensors and hydroblock, a deeper analysis is necessary.

How does the speed sensor work

Sensors that control speed work on the principle of electromagnetic induction. In the gearbox of the leading bridge, the coil with a magnetic core is rigidly recorded. Also in the hub, a toothed crown is fixed, which rotates in parallel with the wheel. Then this rotation changes the parameters of the magnetic field, which in response causes the current appearance. The power of electric flow will be directly proportional to grow relative to the speed of rotation of the wheels. Stripping from this force, in turn, a signal is created, and is transmitted to the electronic control unit. The pulses are transmitted from four speed sensors that are two types: active and passive, and also differ in design.

The active type of sensor functions with a magnetic sleeve. The binary signal transmission is carried out by reading its tag. Due to the speed of rotation, there are no errors, and as a result - accurate impulse data.

In the passive type, a certain comb in the hub block is used. Thanks to such signals, the sensor is able to determine the speed of rotation. It is important to take into account one disadvantage of this design - with a small speed it may be inaccuracy.

Hydrelclock

The hydraulic block includes:

• tank for storing brake fluid - hydroaccumulator;
• intake and exhaust electromagnetic valves, due to which the pressure is regulated injected in the vehicle brake cylinders. Each type of ABS is distinguished by the number of pairs of valves;
• thanks to the universal pump, the necessary pressure is carried out in the system, as a result of which the brake fluid is supplied from the hydroaccumulator, and when it is necessary, selects it back.

Some shortcomings of ABS

One of the greatest drawbacks of the anti-lock braking system is that its effectiveness depends on the quality and condition of the road surface. With a not good road surface, the deceleration path is much longer. This is due to the fact that from time to time the wheel loses contact or adhesion with asphalt and stops rotation. ABS defines such a kind of wheel stop, like locking, and thereby stops slowing down. At the time of the hitch with asphalt, the programmed command is not consistent with the necessary in this case, and the system itself needs to be reinsured again, which requires time and increases the braking path. You can only minimize this effect only by reducing the vehicle speed.

In the case of inhomogeneous road coating, for example, snow - asphalt or ice - asphalt, getting on a wet or sliding area of \u200b\u200bthe road, ABS evaluates the coating and adjusts the braking process under this way. At the same time, when the wheels hit on the asphalt, the abs is again rebuilt, which is why the length of the Tupi braking increases again.

On the soil roads The usual braking system works much better and more reliable than anti-lock braking system. After all, with ordinary braking, the blocked wheel pushes the ground, creating a small slide that does not allow to move on vehicle. Thanks to this, the car stops very quickly.

Another definition of the anti-lock braking system is that at low speed, the system is completely disconnected. In the case when the road is under the slope and at the same time slippery, you need to remember what it may be necessary to brake reliable hand brake. Therefore, it must always be in working condition.

The regular disconnection of the anti-lock braking system in cars is not provided. Sometimes drivers want to disable this system. To do this, pull out the plug from the block. It is also necessary to take into account that in new cars from ABS depends on the redistribution of inter-axis brake forces. Therefore, by braking, rear wheels are completely blocked.

It is important to note that the ABS system is an excellent addition to the car braking system, thanks to which you can control the car in the most difficult and unusual situations. Despite this, we should not forget that it is impossible to fully rely on the machine. From the driver side, you also need to apply great efforts to keep the situation under control.

Video

Hello, dear guests and regular readers. Modern car literally stuffed various. Moreover, few people understand their direct destination, not counting pillows and seat belts. The name ABS, for our hearing, has already become familiar, many motorists know that this system is on their machines, but not everyone understands how it works. So what does this abbreviation mean, what does this system need and how does it work?

ABS - (Anti-Lock Breaking System)Or simply an ABS, this is an anti-lock system, the purpose of which is to prevent blocking wheels when braking. For example, when when braking, one or several wheels are locked and become sliding along the road, the system will weaken the pressure in the brake line of the wheel, and it will start rotation again. And while the brake pedal is constantly and strongly pressed, the blocking process and unlock will continue until the braking process is underway.

The ABS system appeared in the 80s of the last century, and since then has become the most important part of the car security system. Install it not only on cars, but also on trucks, and even on motorcycles.

What is the ABS?

As already mentioned, the ABS is intended to prevent blocking wheels and to maintain the possibility of driving a car during braking, even in emergency cases. The risk of blocking the wheels is that with a sharp braking, on a slippery road, you can lose control over the car. In the absence of ABS, with emergency pressing on the brake, in inexperienced drivers will be blocked by control wheels, and turns of the steering wheel, to any of the sides, will not have any effect, the machine will simply continue to move directly until the adhesion appears again.

It is this task that solves ABS. The system continuously controls the rotation of the wheels and, if necessary, unlocks them. Thereby ensures a constant clutch with an expensive, which allows you to perform maneuvers during stressful situations.

Often, in a pair with ABS, EBD is installed (system for the distribution of brake efforts). Imagine the situation that the car, one side, got on the wet surface of the asphalt, and the other on the dry. If there is no anti-lock system in it, then in case of emergency braking, one side will slow down more efficiently, which will lead to a turn of cars and care to unmanaged skid. This situation is most dangerous when turning when the car is already acting a side effort. The ABS system, along with EBD, will provide rectilinear, safe and uniform braking on roads with inhomogeneous clutch.

What is the system of the ABS and the principle of its work.

During its existence, the system has undergone significant changes and improvements, but the principle of operation and the main functionality, in fact, did not change. ABS consists of several acceleration sensors installed in the wheel hubs, pressure modulators that are embedded in the brake system highway, and the ECU ( the electronic unit Management), which manages signals from valves, and also receives them from acceleration sensors.

All this works like this: each of the sensors located on the hubs, measures the rotation speed of the wheels. If information about a sharp slowdown came to the sensor, or at all about the stop, then a team of a short-term opening of the valve is applied to the control unit to reduce the pressure in the brake line, which will again cause the wheels to rotate. This entire process of controlling sensors occurs very quickly, up to several tens of times in a second. Feel the work of the ABS driver can feel the weak vibrations on the brake pedal.

The system may have a different number of sensors and valves, based on this, and the ABS may be single, two-, three and four-channel. "Multichannel" is determined by the number of valves controlling pressure in the brake line. If each wheel has its own valve, then it is a four-channel ABS, if one per each front wheel And one on the entire rear axle, it is three-channel, on the valve on the axis - two-channel, and one-channel, if there is a single valve for the entire system. All modern cars are equipped with four-channel ABS, the rest can be found only on old cars.

In addition to all the above components, the anti-lock system may include a pump, which restores the pressure in the brake line, after declining due to the opening of the valves.

How to use ABS.

Probably, no driver can very often press the brake pedal to pay off the speed and not lose control. The ABS system was for that created, it is capable of performing this action at interval up to fifteen times per second. It does not allow the wheels to completely blocked, which improves car handling and resistance on the road.

Riding a car with ABS has its own features. The braking effect, with this system, is increasing. But you need to remember that the car does not change its rectilinear movement. Therefore, forget about smooth braking, by car with ABS on the brakes you need to "beat". That is, during emergency braking, a great effort must be applied to the pedals. In addition, you do not need to slow down the engine, the ABS loves to work itself. That is, with emergency braking, you need to turn off the engine from the transmission by pressing the brake pedals and the clutch simultaneously.

Cons ABS.

One of the minuses is the human factor. Many motorists who have a car with anti-lock system begin to feel illusion full securityand gradually lose concentration. As a result, cars with ABS fall into an accident more often than cars without it.

ABS really reduces the brake path on slippery roads. But if we talk about dry and smooth road surfaces, then here, on the contrary, brake path can increase.

The problem of repair and operation ABS is also sharp. For example, acceleration sensors. They are strongly polluted, as they are in the most proximity of rotating parts. Also, to bring them out of order, or give failures in their work, can the backlash bearing. It should only be noted that the system works almost without interruptions modern machinesAnd she can only break through the fault of the most motorists who neglect the safety rules.

And another problem associated with ABS is that the sensors do not always correctly react to the situation on the road. For example, imagine the rise, loss of halfway clutch with the road, and short press on the brake. The system can perceive it as a locking of the wheels, and even before the stop, the squeezed gas pedal will not help hold the car on the slope. Such a situation rarely happens, but may well be.

It will be more complicated to slow down on ice, snow and sand, with sealed tires, as the system can neutralize beneficial features rubber.

Well, after all this, you can confidently say that ABS significantly improves active security car. Today, the car is part of the life and, accordingly, manufacturers try to simplify its management as much as possible. What makes modern drivers less professional than those that were 30-40 years ago. The modern car must be as comfortable as possible and safe for beginner motorists. And no wonder since 2004, the equipment of the ABS system has become mandatory in the EU countries.

ABS, of course, a useful thing, but should not be imposed on the electronics too much hope. It is better to prevent such cases on the road when an anti-lock block system may be engaged. Safe the roads!

Today, most cars on the roads are equipped with any type of anti-lock brake system. Let's see what this system consists and how it works.

Initially, consider the basic principle of operation of the ABS system.

So how are u different manufacturers There are one versions of ABS, their specifications and parts can be called differently.

The ABS is a system that works with all four wheels, which prevents them in blocking, automatically changing the pressure in the brake system of each wheel during emergency braking.

Preventing wheel lock, the system, firstly, allows the driver to continue driving a car, and secondly, can cut the brake path.

During the usual braking of the system with ABS and without ABS, the same is equally for the driver.

During the same braking, when operating ABS on brake pedals, you can feel the pulsation, which is accompanied by the vibration of the brake pedal and characteristic sound.

Device ABS car

Cars with ABS are equipped with a pedal drive with a double brake system.

The main hydraulic brake system consists of:

• hydraulic control valve and electronic control unit.
• the main brake cylinder
• brake tubes and hoses
• brake cylinders on each wheel.

The anti-lock system consists of the following components:

• hydraulic control unit
• electronic Block ABS
• the front and rear sensors of the anti-lock system.

How the ABS car works

The anti-lock system works as follows:

When you click on the brake pedal, it presses on the liquid in and as a result the liquid is squeezed out from there under pressure.

From the main brake cylinder, the liquid enters the hydraulic control unit ABS.

In the hydraulic control unit there are 4 outputs, each of which is connected by a tube with a brake cylinder on the wheel.

At each of these outputs of the hydraulic unit of the ABS, the valve is opened in the original state.

The pressure fluid is pushed out of the hydraulic control unit and on the tubes and hoses enters the brake cylinders on each wheel.

A pressure is created in the brake cylinder on the wheel, and the fluid pushes the piston, which is associated with.

As a result brake pads Press on brake disk or drum. Because of this, friction force arises between the brake pads and the brake disc, and it slows down its rotation.

Accordingly, its rotation slows down and the wheel.

In the brake systems of equipped ABS on the hub of each wheel, a toothed disk and a sensor are fixed.

When rotating the disk teeth wheel passing near the sensor, which fixes it.

The data from the sensor is transmitted to the electronic control unit.

With a very sharp braking, the wheel can also be blocked and the sensor for slowing the rotation of the wheel will notice this.

As a result, the electronic control unit of the ABS seeing that some wheel was blocked, the signal to the hydraulic control unit and blocks the valve supplying the brake fluid to this wheel.

Since the pressure of the brake fluid is reduced to this wheel, it stops slowing down and starts rotating again.

As soon as the wheel begins to rotate, the valve on the hydraulic unit opens, and the pressure of the brake fluid is again transmitted to the brake system of this wheel.

The wheel begins to slow down again.

These actions are repeated very quickly and manifest themselves to the driver in the very characteristic sound and vibration of brake pedal when pressed.

Due to this, when braking the wheels are not blocked and the car does not go, as it is called a yuz.

After all, when driving, the car becomes unmanaged and does not respond to steering. ABS also avoids this and saves the driver with the ability to control the car.

For example, it will help to drive around the obstacle, not letting the brake pedals. There is a delusion that cars equipped with an ABS system stop at a shorter distance than cars without ABS. In reality, it is often not true.

The car with the ABS in most cases will pass a bigger way to a complete stop, but due to the fact that the driver can drive a car he can drive around the obstacle, and not just helplessly press the brake pedal and hope that the car will stop on time.

Also, the ABS system has a positive effect on the tire tread state. After all, in the absence of ABS and when blocking the wheel in braking, the tire will be drown on asphalt only by one point.

As a result of such braking, the tire can be very stealing in one place. During the operation of the ABS, this does not occur.

This is a description of the simplified principle of operation of the ABS system.

In practice, the design of the brake system and the ABS is much more complicated. For example, brake system modern car There is at least two independent contours.

This means that the front and rear wheels are controlled by separate tubes from the main brake cylinder.

ABS in different manufacturers can differ significantly.

In addition, this system can be very difficult and demanding for servicing and repairing greater experience and special tools. Therefore, an inexperienced driver should not be attempts to independently fix the ABS, and it is better to contact the specialists.

Consider the composition and operation of the main ABS blocks implementing the control algorithm.

ABS is an adaptive system that thanks feedback measures the parameters of the control object - wheels (Fig. 1).

Fig. one.

ABS includes three main functional elements: wheel speed sensor (D), electron-decisive block (ERB) or control unit (processor) and pressure modulator (M). ABS elements are included in the circuit of the standard braking TC drive, having a power supply (BP) (compressor or hydraulic pump), brake valve (TC) or main brake cylinder for brake systems with hydraulic drive, brake mechanism and control object - Wheel.

The TC wheel speed sensor is designed to measure the speed of the wheelchair. The electron-decisive block (ERB) processes information coming from the vehicle sensors, and in accordance with the ABS control algorithm forms and supplies an electrical control signal to the modulator.

The modulator according to the control signal performs a change in the pressure in the wheel cylinder, providing the foaming phase of the wheel or its braking.

The modulator is a high-speed electropneumatic or hydraulic valve in the braking actuator of the braking wheel, which provides a decrease or increase in pressure in accordance with the control signal. A functionally modulator must have high speed in cyclic braking mode in accordance with the control signals coming from the ERB. Structurally modulators are made as logic elements of a two-position type (see Fig. 7).

The modulators depending on the ABS circuit are installed in the brake drive circuit or two wheels axis. It turns on in the brake drive consistently and should not prevent the passage working fluid or air from brake crane when driving a driver. Usually, the modulator has one input and two outputs (to the brake cylinder of the wheel and in the air discharge channel or liquid drain).

Currently, ABSs operating on a three-phase cycle are common. In addition to the Phase "Braking - Raming", have phases of pressure tools in the wheel cylinder.

Consider on the example of the company BOSCH The design features of ABS (Fig. 3), which is embedded as an additional in the standard brake system and is used on many TC brands. We also note that other ABS developers use similar algorithms known on the driving engine control dynamics.

Fig. 3. 1 - wheel inductive sensor; 2 - rotor wheel sensor; 3 - wheeled cylinder; 4 - brake force regulator; 5 - main brake cylinder; 6 - Electrohydronasos; 7 - modulator; 8 - tank; 9 - control unit; 10 - warning lamp; N / p - injection and unloading electromagnetic valves; - input signals bu; - output signals bu; - brake pipeline

Between the main brake cylinder and wheel cylinders, injection (H) and unloading (P) solenoid valves are established, which are either supported at a constant level, or reduce the pressure in the wheel drives or in contours.

The solenoid valves are powered by a control unit that processes information coming from four wheel sensors, and forms in accordance with the ABS operation algorithm control signals of the pressure modulator. Based on continuously incoming data on the speed of rotation of each wheel and its changes, it determines the moment of the possible transition of the wheel to blocking. The ABS task is to avoid blocking and the wheel of the wheel to eliminate the loss of stability and maintain the controllability of the CU when braking. Therefore, it will prematurely give a pressure reset control signal and includes hydraulic pump that returns a portion of the brake fluid back to the nourishing tank of the main cylinder.

In the electro-hydraulic modulator ABS (Fig. 4), solenoid valves, hydraulic pump with liquid pressure batteries, electromagnetic valve relays and hydraulic pump relays are condensed.

Fig. four. 1 - electromagnetic valves; 2 - relay of hydraulic pump; 3 - electromagnetic valve relays; 4 - electrical connector; 5 - hydraulic pump electric motor; 6 is a radial piston element of the feed feed pump; 7 - Pressure batteries; 8 - silencers

In the hydraulic block (modulator), each brake cylinder of the wheel corresponds to one intake and one exhaust valve, which control braking within its contour.

Pressure battery is designed to receive brake fluid when resetting pressure in the brake circuit. The feed feed pump is connected when the tank of pressure accumulators is not enough, and increases the pressure reset rate. Damping chambers take the brake fluid from the pump feeder and quench its oscillations.

In the hydraulic unit, two pressure batteries and two damping chambers are installed according to the number of brake hydraulic circuits.

The inverse supply hydraulic pumps of the electro-hydraulic modulator can be both single-stage and two-stage (Fig. 5).

In a single-stage pump feed supply ABS (Fig. 5, a, b), the entire cycle volume of the brake fluid is suused and, accordingly, flows through the pipelines in one stroke of the piston. The absorption absorption required for this is sufficiently high and increases with an increase in the viscosity of the brake fluid at low temperatures. As a result, cavitation arises and the losses associated with it in the performance of the pump.

In the two-step pump of reverse supply ABS (Fig. 5, in, d), the space for the piston forms the second working chamber. Suction of the brake fluid is carried out in two receptions and occurs during both direct and reverse piston stroke, which increases twice the volume of looped fluid. Thus, the entire cycle volume of the loop fluid flows through the pipeline continuously and necessary to ensure this breakage of suction turns out to be lower, which prevents cavitation.

Fig. five. Hydraulic pump feed feed and scheme of its operation: a - suction of the working fluid with single-stage hydraulic pump; b - injection of working fluid with single-stage hydraulic pump; B is the suction of the working fluid with two-stage hydraulic pump; g - discharge of the working fluid with single-stage hydraulic pump; 1 - the injection line; 2 - piston; 3 - cylinder; 4 - suction line; 5 - the first working chamber; 6 - Second Working Camera

The operation of the ABS Bosch 2S system occurs according to the program divided into three phases: 1) normal, or ordinary, braking; 2) Pressure retention at a constant level; 3) Pressure reset.

Phase of normal braking(Fig. 6, a). In conventional braking, the voltage on the electromagnetic valves is absent, from the main cylinder, the brake fluid under pressure passes through the open solenoid valves and drives the brake mechanisms of the wheels. Hydraulic pump does not work.

Fig. 6. a - phase of normal braking; B - Pressure Pressure Phase at a constant level; in - phase discharge pressure; 1 - wheel sensor; 2 - wheel (working) cylinder; 3 - discharge pump; 4 - main brake cylinder; 5 - control unit; 6 - Pressure battery; 7 - electromagnetic valve; 8 - electrohydraulic modulator; 9 - Rotor wheelsensor;

Pressure Pressure Phase at the constant level(Fig. 6, b). When signs of blocking one of the wheels bucking, having received an appropriate signal from the wheel sensor, proceeds to the execution of a pressure retention cycle program at a constant level by separating cylinders - the main and appropriate wheel. A current of the electromagnetic valve is supplied by a current by force 2 A. The valve piston moves and overlaps the flow of the brake fluid from the main cylinder. The pressure in the working cylinder wheel remains unchanged, even if the driver continues to press the brake pedal.

Phase discharge pressure(Fig. 6, c). If the risk of blocking the wheel is preserved, the voltage of the larger sieps is cut to wind the electromagnetic valve: 5 A. As a result of the additional movement of the valve piston, a channel opens through which the brake fluid is reset into the fluid pressure battery. Pressure in the wheel cylinder drops. A bucks command on the inclusion of hydraulic pump, which takes part of the fluid from the pressure battery. The brake pedal is raised, which is felt by the biothe of the brake pedal.

To control the pressure and speed of the vehicle wheel in the ABS brake system, the wheel speed sensors (velocity) and the pressure sensors described above are used.

The principle of operation, similar to ABS 2S, is also used for ABS 2E bosch firms (Fig. 7), but this system uses a spiral cylinder to equalize the pressure in the brake drive of the rear wheels of the vehicle, which allows three electromagnetic valves instead of four electromagnetic valves. The modulator, thus, includes three electromagnetic valves, equalizing a cylinder, two-position injection hydraulic pump, two pressure batteries, pump relays and solenoid valve relays.

Fig. 7. 1 - electromagnetic valve; 2 - Pressure battery; 3 - main brake cylinder; 4 - discharge pump; 5 - bypass valve; 6 - piston of the equalization cylinder; 7 - electromagnetic valve of the rear axle; P P - Front right wheel; P l - front left wheel; S p - rear right wheel; Z l - rear left wheel

The system works as follows. In conventional braking, the brake fluid under pressure from the main cylinder enters the operating cylinders of both front wheels and the right rear wheel through three solenoid valves, which are closed in the initial position. The brake fluid is supplied to the working cylinder of the left rear wheel, through an open bypass valve of the equalizing cylinder. When the danger of blocking one of the front wheels occurs, it gives the command to the closure of the corresponding solenoid valve, preventing the pressure in the wheel cylinder. If the risk of blocking the wheel is not eliminated, the current is supplied to the electromagnetic valve, which provides the opening of the plot of the line between the wheel cylinder and the pressure battery. The pressure in the brake drive drops, after which it gives the command to turn on the hydraulic pump, which distinguishes the liquid into the main cylinder through the equalizing cylinder.

When the danger of blocking one of the rear wheels is arising, the pressure of the brake fluid will be adjusted in both rear brakes at the same time, in order to prevent the movement of the rear wheels by the USD.

The electromagnetic valve of the right rear brake drive is set to the restraint of constant pressure and overlaps the line of the line between the main and wheel cylinders. The opposite end surfaces of the piston 6 of the equalizing cylinder begins to operate the pressure of various values, as a result of which the piston moves downwards towards the smallest pressure (in the figure - up) and the valve 5 will close, disconnecting the main and wheel cylinders of the left rear brake. The piston of the equalizing cylinder due to the resulting pressure difference in the working cavities above it and under it, whenever it is established in such a position in which the pressure in the drives of both rear brakes is equally.

If the risk of locking the rear wheels is saved, the electromagnetic valve buckets the electromagnetic valve in the rear wheel circuit in 5 A. The solenoid valve spool moves and opens the contour site between the operating cylinder of the right rear brake and the fluid pressure battery. The pressure in the circuit is reduced. Hydraulus pumps the brake fluid into the main cylinder through the equalizing cylinder. As a result of a decrease in pressure in space above the piston 6, its next movement occurs, the spring of the central valve is compressed, the volume of space under the top piston increases. The pressure in the left wheeled brake cylinder is reduced. The piston of the equalizing cylinder is again set to a position corresponding to equality of pressures in the drives of both rear brakes. After eliminating the threat of blocking the wheels, the solenoid valve returns to its original position. The piston of the equalizing cylinder under the action of the spring also occupies the initial lower position.

More perfect is the ABS of the 5th series of the Bosch company with block 10. It refers to the new generation of ABS systems, representing a closed hydraulic system that does not have a channel for returning the brake fluid to the tank that feeds the main brake cylinder. The scheme of this system is shown on the example vOLVO car S40 (Fig. 8).

Fig. eight. 1 - check valves; 2 - Valve plunger pump; 3 - hydroaccumulators; 4 - pulsation suppression chambers in the system; 5 - electric motor with an eccentric plunger pump; 6 - Tank for brake fluid; 7 - Working brake pedal; 8 - amplifier; 9 - main brake cylinder; 10 - ABS block; 11 - graduation control valves; 12 - intake controlled valves; 13 - throttling valves; 14-17 - Brake mechanisms

Electronic and hydraulic components are mounted as a single node. Their number includes, besides those indicated in the scheme: relay to turn on the electric motor of the plunger pump 5 and the switching relay 12 and the outlet 11 valves. External components are: ABS Signal Lamp in dashboardwhich lights up in the event of a malfunction in the system, as well as when the ignition is turned on for 4 s; Brake switch and wheels rotation speed sensors. The unit has an output to the diagnostic connector.

The throttling valves 13 are set to reduce brake force on the rear wheels in order to avoid their lock. Due to the fact that the brake system has a setting on a more "weak" rear wheel (this means that the pressure of the rear wheels is the same, and its value is set to the closest to blocking the wheel), the throttling valve is installed one on the contour.

Brake mechanisms 14–17 include brake discs and single-surface calipers with floating cleaners and brake pads equipped with spicy lining wear brackets. The brake mechanisms of the rear wheels are similar to the front, but have solid brake discs (on the front - ventilated) and the actuator parking brakemounted to the caliper.

When you press the brake pedal 7, its lever releases the stop signal switch button, which, tripping, turns on the stop signals light bulbs and gives ABS to the duty state. Pedal movement through stock and vacuum amplifier 8 is transmitted on the pistons of the main cylinder 9. The central valve in the secondary piston and the primary piston cuff overlap the contour message with the tank 6 for the brake fluid. This leads to an increase in pressure in brake circuits. It acts on the pistons of brake cylinders in brake calipers. As a result, the brake pads are pressed against the disks. When the pedal is released, all parts are returned to its original position.

If one of the wheels are close to blocking (as indicated by the rotational speed sensor), the bucks the inlet valve 12 of the corresponding circuit, which prevents the further growth of pressure in the circuit, regardless of the pressure growth in the main cylinder. At the same time, the hydraulic plunger pump begins to work 5. If the wheel rotation continues to slow down, it opens the exhaust valve 11, allowing the brake fluid to return to the hydroaccumulators 3. This leads to a decrease in pressure in the circuit and allows the wheel to rotate faster. If the wheel rotation is overly accelerated (compared to other wheels), to increase the pressure in the circuit, it covers the exhaust valve 11 and opens the intake 12. The braking fluid is supplied from the main brake cylinder and with a plunger pump 5 of the hydroaccumulators 3. Damping chambers 4 smoothed ( Push) pulsations arising in the system when operating a plunger pump.

The stop signal circuit breaker informs the braking control module. This allows the control module to more accurately monitor the wheel rotation parameters.

The diagnostic connector is used to connect the Volvo System Tester when performing diagnostics.

The disadvantage of the ABS system is that on the loose surface (sand, gravel, snow) the use of the anti-lock system increases the braking path. On such a coating, the smallest brake path is provided with blocked wheels. In this case, before each wheel, a wedge is formed from the soil, which leads to a reduction in the braking path. IN modern designs ABS This deficiency is eliminated - the system automatically determines the nature of the surface and for each implements its braking algorithm (extended anti-lock ABSPLUS).

The ABSPLUS system is a software extension in the ABS / ESP control unit. The absplus system allows on the road without a solid coating (for example, crushed stone or sand) to reduce the brake path to 20%. Absplus uses ESP system sensors.

Based on the ABS sensors and the ABS control unit, the system recognizes the nature of the road surface. Reducing the brake path on the road without solid coating is achieved due to the short-term controlled blocking of the wheels. At the same time, the blockin of the road coating material is formed before the locked wheels, which has a braking effect and thereby shorten the braking path. After certain intervals, the wheels are periodically released and begin to rotate, as a result of which the car handling is preserved.

2. Device and operation of the ABS sensor

In the ABS brake system, wheel speed sensors (speed) and pressure sensors are used.

As wheel rotation sensors the ABS system uses passive and active wheeled sensors.

Sensors of both types allow the system to obtain data on the speed of the vehicle and, more importantly, the frequency of rotation of individual wheels. Based on the difference in the speed of rotation of the individual wheels, the system may, for example, install, are there any different wheels on the road surface with a different clutch coefficient, which would mean for the car a potential danger during braking to get into a complex dynamic situation.

Passive sensorswork without self-powering than and the name is explained. As a rule, an inductive sensitive element is used in such sensors.

For any measurement of the rotational speed, two elements are needed: sensitive and specifying. The sensor element of the sensor is made in the form of a coil 3 with an iron core (magnetic pipeline) 4 and in contact with it with a permanent magnet 5 5. The specifying element 2 is a ring with teeth (specifying ring or rotor) (Fig. 9).

Fig. nine. a - general view; b - low rotational speed; B is a high speed of rotation; 1 - magnetic field; 2 is a specifying element (metal ring with teeth); 3 - coil; 4 - iron core (magnetic circuit); five - permanent magnet; 6 - sensitive element; 7 is an oscillogram at a low rotational speed; 8 - oscillogram at high speed

Any iron object passing through the magnetic field of the sensor changes the shape and strength of this field. As a result of changing the magnetic field in the sensor coil, in accordance with the law of electromagnetic induction, EMC occurs, the measurement of which allows you to fix the fact of changing the magnetic field. From the principle of operation, the name of the sensors of this type is inductive.

The intensity of the magnetic flux passing through the winding depends on whether the sensor is opposite the tooth on the disk or opposite the gap (teeth pass). Since the magnetic flux is concentrated by the teeth of the disk, which increases the magnetic flow through the winding, then when the teeth skip approach, it weakens. Consequently, when rotating a toothed disk there is oscillations of the magnetic flux, which, in turn, generate sinusoidal voltage fluctuations in the electromagnetic winding, proportional to the speed of changing the magnetic flux. The amplitude of the oscillations of alternating voltage increases strictly in proportion to the increase in the rotational speed of the toothed disk.

Passing through the magnetic field of the sensor of each of the teeth of the specifying rotor induces, thus, the voltage in the chain of the sensor coil. Counting the number of voltage pulses for a certain time interval (frequency) allows the system to calculate the speed of rotation or wheel speed.

The advantage of passive inductive rotational speed sensors is the simplicity of their design. The disadvantage is that it is necessary to provide a certain gap between the specifying rotor and the sensor to work with high accuracy. In addition, passive inductive rotational speed sensors have a larger mass and dimensions, respectively require a lot of space to install.

From the frequency of rotation of the specifying rotor, not only the frequency of the pulses, but also their value (voltage), so with small frequencies of rotation, the passive sensor gives a signal of a smaller value than the active one.

Active rotational speed sensorsIn contrast to passive, the external supply voltage is used to work, which is about 12 V. The operation of the sensitive elements of active speed sensors is based on the principle of the Hall effect or on the principle of the magnetoresistive effect.

The active sensors also consist of two components: sensitive and specifying (Fig. 10). The sensitive component includes a magnetic field sensor and an electronic circuit. The specifying element is a plastic ring, the surface sections of which are namagged in opposite directions (magnetic ring). The North and South Poles of Magnets perform the functions of the teeth and the wheelchair.

Fig. 10. a - general view; b - low rotational speed; B is a high speed of rotation; 1 - specifying element; 2 - electronic circuit sensor; 3 - sensor housing; 4 - oscillogram; 5 - magnetic field sensor

The principle of operation is based on a quantum mechanical effect created by layers of ferromagnetic and non-ferromagnetic material (resistance increases greatly or weakens).

When the magnetic field sensor passes through the changing magnetic field, the EMU Hall arising in it changes, and its resistance changes for magnetic sensors. The faster the magnetic regions of the magnetic ring pass by the magnetic field sensor, the faster and the EMF (voltage) of the hall is changed. The frequency of rotation of the wheel with sensors of this type, as well as with passive, is determined on the basis of the voltage change frequency.

Active sensors give equally accurate results in the entire frequency range, since the strength of their signal does not depend on the measured frequency, but is determined by the proper sensor current. In addition, the active sensor has a compact design, which allows you to install it directly in the hub bearing. Digital output signal processing gives additional advantagesFor example, allows you to use the sensor to determine the direction of rotation of the wheel and stop it. An important advantage is also a high accuracy of determining low rotational speeds.

The disadvantage of such sensors is the difficulty of checking their health with an ohmmeter.

Wheel speed sensors can be attached to the wheel drive shaft, on the shaft of the driving gear drive for rear-wheel drive models of the car, on the rotary pin (Fig. 11, a) and inside the wheel hub (Fig. 11, b).

As pressure sensors piezoelectric and capacitive sensors are used in the ABS system.

Fig. eleven. a - fastening of an inductive sensor on a swivel pin; b - fastening the inductive sensor inside the wheel hub; 1 - brake disc; 2 - front hub; 3 - protective casing; 4 - screw with internal hexagon gearing; 5 - sensor; 6 - swivel pin; 7 - Wheel fastening flange; 8 - balls; 9 - sensor ring; 10 - fastening flange for suspension

molds to the hydraulic unit and serves to determine and transmit pressure to the computer in the brake system when braking. At the resulting value, the bu calculates the brake forces on wheels and the longitudinal force acting on the vehicle. If you need to perform a control cycle, the resulting value is used by the control unit to calculate the forces acting on the vehicle in turn.

The main components of the sensor are a piezoelectric element 2 under the pressure of the brake fluid, and the electronic part 1 (Fig. 12).

Fig. 12.

Under the action of the brake fluid pressure, the charge distribution in the piezoelectric element is changing, and the voltage value depends on the pressure in the brake system.

The fluid pressure sensor in the brake system can also be used capacitive sensor(Fig. 13).

Fig. 13. a - general sensor scheme; b - increase in fluid pressure; B is a decrease in fluid pressure; 1 - sensor; S 1, S 2 - the distance between the plates; C 1, C 2 - Capacity Capacitor

The condenser has the ability to accumulate and hold a certain electrical charge. The distance S between two plates provides some capacitance of Condenser C.

One of the plates is fixed. The second plate can be moved under the influence of the pressure produced by the brake fluid.

When exposed to pressure on the movable plate, the distance between two plates decreases and becomes equal to S 1, and the capacitor capacity increases and becomes equal to C 1.

In the case of a decrease in pressure, the plate is moving back under the action of the spring, the capacitance of the capacitor decreases again. Consequently, the change in the capacity is directly related to the change in pressure.