You can not argue on the fact that the car is considered quite dangerous vehicle. Not many people know that even such a complex technical remedy As an airplane, much safer. But most of the automotive states happen due to the banal negligence of its owner. I did not see one thing, did not touch the other, did not fade there, where it is necessary - that's all that it can disrupt the technical condition motor vehicle. And sometimes it happens that this negligence brings to not the most pleasant things. To prevent this should be carefully monitoring the condition of all the units of your car. One of them is the brake system. How to diagnose brake system?
Diagnostics of the brake system - why?
If you are a supporter of the opinion that the brakes came up with panties, then we hurry you to dissuade this. The brake system is considered one of the most important systems in your car responsible for safety. That is why it is necessary to conduct its diagnosis in a timely manner. Usually, the diagnosis of the brake system is carried out when the scheduled maintenance is passed. It in turn is carried out, following the instructions of the automaker.
If you have discovered a clear deterioration in the technical condition of the brake system of your car, you can make diagnostics yourself. As a rule, in this procedure there is nothing complicated and with a simple replacement of the pads to cope with every person who is at least a bit disassembled in the technique. If you decide to entrust work to the master, you can send a car to a service where the car braking system can be checked with special equipment.
In which cases is necessary diagnostics?
Before you decide to repair the brake system yourself, it is necessary to understand whether it is really faulty. Usually, on the unsatisfactory technical condition of the brakes indicates one or more signs:
- The brake path of the car increased markedly
- The brake pedal works incorrectly - it takes deep down, then hences at all
- Brake pedal is pressed, but its movement occurs on the trajectory curve
- The brake system represented by the pads constantly makes it the hum, screenshots and strong vibration In braking
- Brake fluid, pumping system, began to be consumed too fast, clearly visible
In addition to the above explicit signs, there are more secretive problems that may also arise. If you removed the wheels and there are pads in the open access, then you can pay attention to the degree of their wear. Explicit sign that the system works incorrectly uneven wear Pad. Also, watching the car yourself in search of problems, pay attention to the hoses and brake tubes. It is possible that they were damaged.
Diagnostics of the brake system of the car on the stand
If you decide to entrust work to the masters of your business, or you just do not have time to engage in a car yourself, it will be quite reasonable to contact specialized service. The main advantage of this method is that you get highly qualified help of specialists who quickly and efficiently eliminate all brake system malfunctions. However, before their elimination, it is necessary to diagnose. In such services, it is carried out on specially intended stands.
As a rule, stands that are posted in services automotive serviceare multifunctional. On them you can measure and maximum speed Car, and overclocking time and other parameters you are interested in. However, our goal is to diagnose the brake system. When checking its technical condition, the stand provides the following indicators for analysis:
- General Temperature Specific
- The value of the relative unevenness coefficient
- Parameters asynchronous practice
It is worth understanding what equipment as a stand is quite costly pleasure, so small services cannot afford it. But the stands installed in large automotive services are divided into several types. Either they are installed as a separate equipment or are one-alone coated. The only remark, the zone for placing the car imitates the asphalt coating.
What else is in diagnostics?
In addition to the fact that the car is checked on a special stand, a visual inspection of all aggregates belonging to the brake system as a whole is carried out. This is usually the same person that launches the diagnostic process on the stand, as having studied the data on the operation of the system, you can immediately assume that it is specifically faulty.
A number of details are subject to careful inspection, which may affect the incorrect operation of the brakes, with all the resulting. As a rule, the inspection passes on the list:
- Inspection of the container with liquids for the brake system
- General condition and inspection brake discs, including drums
- Inspection brake shoes
- Technical status of the wheel bearing
- Detection for faults in the caliper section
- Cylinders and their performance
- Functioning of the amplifier of the main brake cylinder
- Inspection of brake hoses
Summing up and repair
After the car and its brake system were completely digitized, and all the details are carefully examined, the time is coming. Here you voiced a specific list of faults and details that need to be replaced.
As a rule, the full repair of the brake system is produced once every 30-40 thousand kilometers. However, it is worth considering the fact that it all depends on your driving style. If you rarely resort to emergency brakingAnd you know how to properly use the brake pedal, you can hardly have to face such a problem as a car braking system diagnostics.
As the experienced drivers say - they are not broken from the faulty accelerator pedals in the accident. But the defective brake pedal is easily. Having gained speed, the car (as a rule, weighing more than tons) gets such a supply of inertia that it takes a tremendous effort to stop it. The maintenance of the brake system is directly related to the safety of the driver and passengers.
Brake system B. modern cars It is quite reliable, otherwise automakers will not be able to certify their product. There is a built-in diagnostics of the brake system, the pipelines are made in the form of two equivalent and independent contours. Nevertheless, the statistics of the accident due to the flawed brakes are disappointing. It is not only about the inability to stop in time. Uneven distribution of effort between wheels, early blocking, lead to loss of manageability and drift. That is, the car seems to be slowed down, but the braking system itself becomes a source of danger.
The situation aggravates a large number of cars with solid mileage. The owners, as a rule, are negotious to the maintenance of such cars, because the warranty has long been over, and confidence in the reliability of its iron horse on the contrary is strengthened. BUT simple diagnosis The brake system will help not only avoid trouble, but maybe save your life.
Signs of brake system malfunction
- The usual grabity disappeared - with the same position of the pedal, the braking is more sluggish.
- Increased brake pedal stroke.
- When braking, the car takes to the side.
- The main brake cylinder has a backlash.
- Unreasonable decline in level brake fluid.
- "Potion" of brake hoses or connecting elements.
- Driving on system elements.
- Short-term lightning of the lamp "Faulty brake system" on the instrument panel.
- Outsided sounds in the area of \u200b\u200bthe wheels when braking.
- Drops of brake fluid on the site of a car.
Of course, with an obvious brake failure, the diagnosis of the brake system is not required. Urgent repair is required, since the operation of the car in this case is prohibited. If any of the listed features appears, we recommend contacting our service to examine and prevent serious breakdowns.
How often is the brake system checked?
The frequency of diagnostics is defined in the service book, there is a list of works during maintenance. There is also a daily verification that you can spend yourself. But the detailed check, with the measurement of the parameters, is possible only on professional service. If you for some reason do not conduct a regular then, our service station will help you to estimate the state of the brakes with the help of professional stand equipment.
What includes the diagnostics of the brake system?
In addition to standard dynamic tests at which the braking path is estimated, we work according to the factory algorithm.
- Checking the wear of the brake pads using the measuring instrument.
- Estimation of the condition of the caliper: fastening, guides, springs, dampers.
- Check the content of moisture in the brake fluid.
- The main brake cylinder: the condition of the cuff, the glands, connecting pipes.
- The magnitude of the working pistons.
- The performance of the brake system amplifier.
The main diagnosis of the brake system is made on the stand. Using measurements, all dynamic parameters are evaluated. The brake system is checked in workers, emergency and extreme modes. The measurement accuracy is determined by the instrument class. Our service has universal equipment on which you can not only test, but also adjust the main brake cylinder and other system elements.
Is it possible to diagnose the system yourself?
Specialists of our service categorically do not recommend this. Incorrectly carried out the diagnostics of the brake system not only can damage any component. You can make incorrect conclusions about the level of brakes. And then, in a responsible moment, the system will sum up. The same applies to non-professional specialists.
If the work is manufactured on the dealer station, the quality is guaranteed. But the cost of diagnosis will be too high. In this case, the equipment is used the same. After the diagnosis, our service will offer you an optimal cost, repair. You pay only real work, according to flexible rates. On the dealer a hundred you will be imposed of mandatory procedures installed by the manufacturer.
The cost of diagnosing the brake system
The cost of diagnosing the brake system is 400 rubles. Independently calculate the cost of repairing the brake system you can
Today, according to the current GOST 25478-91, applies two main methods of diagnosing brake systems - road and stand. For them, respectively, the following parameters are installed - during road testing:
- braking distances;
- established slowing down;
- linear deviation;
- the slope of the road on which the PBX should still be held;
- with bench tests:
- general specific brake force;
- brake system operation time;
- the non-uniformity coefficient of the brake forces of the axis wheels;
- and for the road train, even additionally: the coefficient of compatibility of the units of the road train;
- asynchronism of the timing of the brake drive.
Also, the general diagnostic parameter for both test methods is the effort on the working body of the brake system drive.
Many due to visible simplicity and cheapness seek to limit both road brake trials. This may be justified in some cases, so road brake tests are distributed abroad. But, in general, in Russia, in our climatic conditions, road brake tests can only be considered an addition to more informative stands. Already at least only because the true picture of braking unevenness can be obtained only in possessions when many subjective factors are reduced to zero.
Since it is the unevenness of the brake forces now, as the average speed of movement increases, it has an increasing impact on safety. road, if we want to really diagnose the car, and not create the visibility of this process, we should apply really "diagnostic" methods and the corresponding equipment.
Where do they do?
The full diagnosis of brakes is really possible only during stand tests.. But they are different. In the world today there are several test methods and types of stands:
- tests on power roller brake stands;
- tests on inertial roller brake stands;
- static brake tests;
- Tests on platform brake stands.
So what preferred?
The easiest and cheapest method, of course, static.
According to the physics of the process, it is similar to testing the parking brake system on a slope. From here, the result is extremely non-informational and, by virtue of a number of other reasons, an unacceptable method. Another method - tests on the platform brake stands, got widespread, mainly due to its cheapness. But it has a number of disadvantages that do not allow it to be acceptable, especially when conducting instrumental control during the GTO. For example, during road tests and on inertia brake stands in the process of braking, the wheel makes at least more than one turnover, so the entire braking surface is estimated. brake mechanism . In addition, in the field brake stands, in view of the small initial braking rates (under safety conditions) and intensive, fast braking (due to the boundedness of the brake path, which is determined by the length of the braking grounds), the braking is carried out on the part of the brake braking surface, which is unacceptable with Point of view of car safety assessment. And finally, too intensive braking (according to the above reasons) distorts the real physical picture of the car braking. GOST 25478-91 requires each measurement on brakes at least two times, i.e. Must be ensured by the repeatability of testing. In similar conditions. When testing on the road and on platform stands, the initial speed is set by the driver and may vary widely. When testing on platform brake stands, the initial velocity of the vehicle does not comply with the requirements of the traffic rules and GOST 25478-91, and it means that kinetic energy is less than what is required to correctly assess the braking system. By virtue of this, it will not be required to maximize the brake pedals for damping this energy. Thus, when testing on platform brake stands, overestimated values \u200b\u200bare obtained by specific brake power and lowered - in force on the brake-drive drive organs. The roller brake stands allow you to obtain more correct results. With each repetition of the test, they are capable of providing conditions (first of all the speed of rotation of the wheels) are absolutely the same with the previous ones, which is ensured by the exact task of the initial braking speed by an external drive. Also, when testing on power roller brake stands, a measurement of the so-called "ovality" is provided - an assessment of the non-uniformity of the brake forces in one turnover of the wheel, that is, the entire braking surface is investigated. In addition, when tested on roller brake stands, when the force is transmitted from the outside, from the brake stand, the physical pattern of braking is not violated. The brake system should absorb the income from the outside, even though the car does not have kinetic energy. Similar reasoning can be given to evaluate the effort of pressing the driving bodies of brake systems. There is another important condition - this is the safety of tests. From this point of view, the safest tests are on force roller brake stands, since the kinetic energy of the test car on the stand is zero. In case of failure of the brake system during road testing or on the platform brake stands, the probability of an emergency is very high. In addition, GOST 25478-91 limits the effort on the pedal of the working brake drive and the parking brake control body. This value, from the point of view of the theory of braking, determines the efforts in executive mechanisms The brake system required to clean the kinetic energy of the slowing car. Summing up, we can say: platform brake stands are suitable for input express - diagnostics at stations, but in no case for in-depth. Inertial brake stands are somewhat mansion. This method creates the conditions of car braking, as close as possible to real. But due to the high cost of the stand, insufficient safety, laboriousness and too much time required for the diagnosis, the stand of this type will not be profitable as part of our needs. Thus, it turns out that by the totality of its properties, it is roller stands that are the most optimal decisionFor both diagnostic lines of a hundred and equipment of instrumental control points.
Since 1998, there has been a mandatory instrumental control during the passage of the Gostechnology. Currently, regulatory and technical documents in conducting a GTO require mandatory diagnosis of brakes, environmental parameters, headlight headlights and steering status. This requirement applies only to cars from 5 years and older. But, after all, everything is affected by everything, and not only what is determined by GOST. And far from the fact that the problems associated with the aforementioned systems in the cars "younger" are uniquely absent. In general, the universal annual "dispensarization" of cars is a good matter and the entire civilized world has long been practicing it. The owner is obliged to obtain a diagnosis of the technical condition of his car. But this is not quite enough. After all, if it is forced to check the brakes - you will check only them and repair only them will be repaired. And, if once a year, the car will be checked at the maximum, then a person will surely think, even if he is not imputed to the duty to correct absolutely everything that has revealed. A reasonable person will surely understand that it is worth to correct, for example, the shock absorbers, and the collapse of the treat, and the brake fluid, really, should be replaced. And this is the work for a hundred, it is the opportunity to make money. Therefore, we recommend, when determining the composition of the diagnostic line, to calculate the benefit of direct and benefit is promising, indirect. And very often the second benefit is approximately the same order as the first. Consequently, expanding the spectrum of verified parameters today, even if we are not mandatory, who are not demanded today by gostams or traffic rules, and offering such a service to potential customers, you create a future work prospect.
Probably, none of the car systems does not need such a health as brake, otherwise about the consequences, we think there is no point in talking.
Diagnosis of brake fluid diagnosis
The periodic diagnosis of the brake system is the proof that the brakes will not let you down in any, even in the most critical situation. Well, the most important thing is to diagnose yourself for each car owner independently, in addition, such a procedure does not require any special tools or certain skills. All you need is a clean cloth, a standard set of tools, a roulette or a ruler and a small brake fluid canister.
Bring out the diagnosis of the brake system follows from controlling the level of the brake fluid. It is worth noting that a similar procedure must be carried out periodically, at least once a month, it is also required after the hydropolor was removed, and naturally, when the system itself signals the disadvantage of the fluid. The brake fluid control is a fairly simple task that can be visuallyed, since there are two divisions on the tank with brake fluid - minimum and maximum, the norm is considered when the level of the protroscheuhi is between them.
If you have installed fluid failure, then it is necessary to add it immediately - by disconnecting the tip of the wire harness, unscrew the tank cover and pour the pre-prepared (necessarily new) brake fluid to the maximum mark. After that, tightly tighten the lid, connect all the harnesses in the reverse sequence. Make sure that you have done everything correctly, you can with the engine running on the control light on dashboardwhich should light up when pressed on the tank cover.
Diagnostics of the entire brake system
After the above operation, attention should be paid to the vacuum brake amplifier. It is worth noting that this procedure must be carried out when the ignition is turned off, so if the motor has worked before that, it must be drowning. Now you need to do - press the brake with the interval, it is necessary to continue to completely disappear the hiss in the amplifier. Then, by clicking on the pedal, you need to start the engine. About the health can be judged by pedals, a little left down.
Pay attention to the goal of the parking brake lever. The fact that he is in order will tell the course of about three clicks, besides, the handbrake must hold the car standing on the descent to about 23 degrees. If at least one of the tasks parking brake It does not cope, it is necessary to replace the details of the details, we recommend not to delay with this, because you guesses the consequences, we think you think.
Well, the final stage in the diagnosis of the brake system is, we have already written about a similar procedure, therefore we will not duplicate themes. If the need for the need was established, then it is required to be carried out immediately, because with brakes, as we have already spoken more than once, the jokes are very bad.
This is such a diagnosis of the brake system on its own. Agree, with a sufficient amount of free time, the presence of patience and desire to pretrately simply. And once again encourage you when troubleshooting is detected, it is impossible to correct them, because the consequences will be extremely sad.
Finally, whatever the system in the car does not need to be diagnosed or repairing should not postpone the satisfaction of this need for a long box. Remember: iron Horse It does not forgive the negligence relationship and indifference, because he, first of all, your combat comrade, with whom you and in the fire, and in water and through copper pipes, in his dedication and reliability you must be 100% sure at any time Otherwise, even the most insignificant problem will turn into a global scale problem.
Methods and means of diagnosing brake systems are developed in relation to diagnostic parameters and requirements technological processes Car maintenance and repair. Accordingly, there are means for the general diagnosis of brakes on road conditions, for general stationary diagnostics before servicing or repairing, for elementary diagnostics in the process of maintenance and repair or after their execution.
Existing means technical diagnostics Brakes (STTT) can be classified on five grounds:
1. Upon use of the clutch forces with a support surface;
2. at the installation site;
3. By way of loading;
4. According to the mode of movement of the wheel;
5. By the design of the reference device.
Fig. 2.1. Tools of technical diagnostics of brakes.
2.1. Stands of technical diagnostics of car brakes.
All the stands of technical diagnostics of the brakes (STTT) are divided into two large groups. The first to which the main part of the stands belong is more numerous. This group of STTT works using wheel clutch forces with a support surface. In these stands, the braking torque was limited to the clutch force with the support surface of the stand, so in most of them it is impossible to realize the full braking moment of the car. The second group of stands working without the use of the clutch forces with a support surface is structurally different in that the braking torque is transmitted directly through the wheel or through the hub. This group of stands have not found wide use due to the complexity of the design and non-technological tests.
Stands, in turn, by the method of loading are powerful and inertial. The power stands of the first group on the mode of movement of the wheel on the stand can be: with partial turning of the wheel and with full turning of the wheel. The first mode is usually characteristic of platform stands, and the second is for all other stands.
According to the design of supporting devices, stands are divided into: platform, roller and tape (first group); With hanging the axes of the wheels and without hanging the axes of the wheels (second group).
In the power platform stands of the car's wheel are stationary, so when you press the brake pedal, only the shear force (breakdown) of the blocked wheels from the place changes, i.e. Friction force between brake linings and drum (disk). There are stands with one common platform for all wheels and with platforms for each wheel of the car.
Power platform stands Possess a number of significant shortcomings that exclude their widespread use. For example, when tested, the effect of movement rate on the friction coefficient of sliding and dynamic impacts in the brake system are not taken into account. The measurement results are largely dependent on the position of the wheels on the stand area, from the state of the supporting surface and the treads of the wheels. It is only measured by the effort of the place of the inhibitory wheels.
Platform inertial standshaving a movable (one common per side or for each wheel) of the site, compared with the power platform stands more perfect, since more fully take into account the dynamics of the braking forces in real conditions. However, these stands have a number of significant disadvantages: the need for acceleration of the car, a decrease in the safety level of work in diagnosing, the accuracy and accuracy of diagnostic information are not sufficient.
Inertial Load Ribbon Stands Reproduce road conditions of interaction of the tire with support surfaces. However, they have significant dimensions and do not provide sufficient stability of the car during diagnosis, and such design deficiencies, like slipping of ribbons and large mechanical losses in friction pairs.
Roller brake stands. From their number in the prevailing majority, stands based on the power diagnostics method are used. The power method allows you to determine the brake forces of each wheel with a defined force of pressing the pedal, the time of operation of the brake drive, evaluate the condition of the working surfaces of the brake linings and the drum, the ellipsity of the drums, etc. In the overwhelming majority of these stands, during the forced scrolling of the inhibited wheels of the car, the speed of movement is simulated 2-5 km / h, rarely up to 10km / h,
The most reliable is inertial method diagnosis on roller inertial stands. They measure the brake path for each individual wheel, the time of operation of the brake drive and slowing (maximum and for each wheel separately), but due to complexity, high cost and lower technological in operation these stands are used extremely limited.
To diagnose brakes in cramped conditions, as well as in order to localize faults and in-depth diagnostics, portable STTT are most effective. The essence of the work method of these devices is that the wheel of the car is forcibly spinning, and when the rotational speed reaches a specified value, the device is triggered to the brake pedal; The wheel is braked, in the process of which the time of operation of the brake drive is recorded, the time of deceleration at a specified wheel speed interval and the braking path with the installed brake force value.
Due to the small inertial mass of postended wheels, the braking process differs significantly from the real one. Bringing the results of the diagnosis of brakes to real conditions is carried out through the translated coefficients for the brake path and deceleration.
The general diagnosis of the car in road conditions is carried out by the following methods; visually on the brake path and synchronization of the start of braking by all wheels; with portable devices; at the maximum deceleration of the car; using built-in devices; By automatic alarm on achieving the diagnostic parameter of the limit value.
The diagnosis on the braking path on the dynamometer is to monitor the car with a sharp one-time press on the pedal (clutch off) and measuring the brake path. At the same time, they are observed for synchronization of braking in the trails of tires left on the road. The test site should be smooth, dry and horizontal. The normative brake path (at a speed before braking, equal to 30km / h) is for passenger cars At least 7.2 m, and for freight and buses, depending on the carrying capacity of 9.5-11m. This method does not give reliable results, and the use of them is difficult due to the need to have a fairly large part of the horizontal road with a solid, dry and even coating.
Diagnosing brakes to slower vehicles using portable instrument-desverometers is also carried out on an even horizontal portion of the road. The car is accelerated to a speed of 10-20km / h and dramatically slow down by a single press on the pedal when the clutch is turned off. At the same time measured ј MAX. Regulatory deceleration (it does not depend on the velocity of the car) for passenger cars is at least 5.8 m / s 2, and for freight, depending on the carrying capacity - from 5.0 to 4.2 m / s 2. For manual brakes, the slowdown must be within 1.5-0.5 m / c 2.
Fig. 2.2. Schematic scheme Descharometer with progressively moving mass.
1 - inertial mass;
2 - warning lamp;
3 - Plate Spring;
4- adjusting screw;
5 - Battery.
The principle of the desserometer is to fix the path of moving the moving inertial mass of the device relative to its body, fixed by car. This movement occurs under the influence of inertia strength occurs when braking the car and proportional to its slowing down. The inertial weight of the dessellometer can serve as a translationally moving cargo, pendulum, liquid or acceleration sensor, and a gear device, scale, a signal lamp, a self-director, a composter, and others. To ensure stability, the testimonometers are provided with a damper (liquid, air, spring), and for Ease of measurement - the mechanism of fixing the maximum slowdown.
To diagnose car brakes using structurally built-in devices, systems that provide information on the wear of the brake pads, the level of brake fluid, pressure in pneumatic - or hydraulic equipment, work manual brakes, malfunctions of the anti-slip device, etc.
The system consists of built-in sensors and panel pointers or emergency alarms. Built-in diagnostics provides continuous tracking of the brake state. From this point of view, it is perfect. The limited application of embedded diagnosis is due to a significant cost. The development of modern instrument making and electronics allows you to expect the rapid development of funds for the built-in diagnosis of modern cars.
General stationary express diagnostics are performed on specialized posts and lines, using high-speed platform stands inertial or power type. For general diagnosis with adjusting work The brake stands of the roller type are also used.
The principle of operation of the inertial platform stand is based on the measurement of the inertia forces (from translationally and rotationally moving vehicles) arising from its braking and attached to the contact places of wheels with dynamometer platforms.
The platform inertial stand consists of four movable platforms with a corrugated surface, which the car runs with wheels at a speed of 6-12 km / h and stops with sharp braking. The emergence of the inertia of the car correspond to the brake forces. They affect the platform of the stand are perceived by liquid, mechanical or electronic sensors and are fixed by measuring instruments located on the remote control.
The disadvantages of the stands of the platform inertial type include: the large production area occupied by them (taking into account the need to pre-overclock the car); Unstability of the clutch coefficient of tires, depending on their pollution, humidity and temperature.
The platform braking stand of the power type on the principle of action is different from the inertia in that the brake forces arising when braking in places of contact of the wheels with dynamometer platforms are obtained not due to the inertia of the car, but as a result of its forced movement through the platforms using the traction conveyor.
For elementary diagnostics at posts and maintenance and repair lines, inertial stands with running drums and power stands with rollers are used. They are divided into two classes: using clutch forces and without using these forces to scroll down.
In the first case, the inhibited wheel turns through the clutch forces arising in the wheel contact places with a drum (roller), to which an inertial torque or a moment of the electric motor directly to the car wheel is applied. In the practice of diagnosing cars, the stands of the first type are used mainly, as they are cheaper and technologies.
Inertial stands with a running or tape reference device using clutch forces can be driven from wheels of a working vehicle or drive from electric motors. A stand with a wheel drive consists of two support-drive units, kinematic interconnected and providing simultaneous testing of brakes of both axes of the car. Each reverse drive unit of the drum stand consists of a frame and two pairs of cross-country drums, which are based on the wheels of the car. Running drums are associated with fly masses.
An electric booth consists of one unit and is usually designed to alternately checking the brakes of vehicles with two driving axes of the reverse drive unit are supplied with additional supporting drums.
The principle of operation of all inertial stands using the clutch forces is the same. If the stand has an electric drive, then the wheels of the car are driven to rotation from the rollers of the stand, and if it does not, then from car Engine. In the latter case, the driving wheels of the car lead to rotation of the rollers of the stand, and from them with mechanical transmission and front, slave, wheels.
After installing the car on an inertial stand, the circumferential velocity of the wheels is brought to 50-70km / h and slowly slow down, at the same time separating all the booth carriages by turning off the electromagnetic coupling (the specified force on the brake pedal is provided by a machine or a monster with a pointer installed on the brake pedal). At the same time, in the field of contact of the wheels with rollers of the stand arise for the forces of inertia, opposing the brake forces. After a while, the rotation of the bench drums and wheels of the car stops. The paths passed by each car wheel during this time, or the corner slowing the drum will be equivalent to their brake paths and brake forces.
The braking path is determined by the frequency of rotation of the rollers of the stand, fixed by the counter, or by the duration of their rotation, measured by the stopwatch, and slow down - the angular desperometer. On the inertial bench, a direct measurement of the braking torque is also possible in the magnitude of the reactive torque that occurs on the shaft of the stand between the flywheel drum. For the accuracy of the results obtained, it is necessary that the conditions for braking the wheels of the car on the stand correspond to the real conditions of car braking on the road. This means that kinetic energy absorbed by the car brakes when they are testing on the stand should be the same as on the road.
Power stands using wheel clutch forces allow you to measure the brake forces in the process of rotation at some speed V \u003d 2 ... 10km / h. In this case, the brake power of each of the wheels of the car installed on the stand is measured by braking them in the process of rotation. Rotation of wheels is carried out by the rollers of the stand from the electric motor. Brake forces are determined by the magnitude of the torque arising from the rollers when braking the wheels.
When diagnosing brakes with hydraulic drive This method determine the dependence of the measurement of the brake force of the RT on each of the wheels of the car from the pressure force on the pH brake pedal. This dependence, called the braking diagram, gives a fairly complete characteristic of the performance of the brake system. In case of the power method of diagnosing the brakes, the total efficiency parameter is the specific brake force σр T / G A · 100%. For most cars, this force is 45-80%, the last digit is an indicator of an excellent state of brakes. The difference of brake forces on the wheels of one axis of the car, ensuring the absence of drift, should not be more than 10-15%.
Diagnosing brakes with power stands is most common. This is explained by the large adaptability of power stands to elementary diagnostics in combining diagnostic work with adjustment, relatively small cost, small or production Square and economical electricity consumption.
The undoubted advantage of inertial brake stands is the ability to diagnose brakes at high speeds. It is this factor that is fundamental to test brake systems with ABS, because This system begins its work from about 20 ... 30km / h.
