Automatic transmission, also referred to as an automatic or a hoe, is a type of car transmission that allows you to reduce the load on the driver when driving, since the gear selection is automatic, without the participation of the driver. This fact affects all the characteristics that cars with an automatic transmission have.

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Benefits of automatic transmission

• increasing comfort when driving a car and freeing the driver from control of third-party functions;
• smooth gear shifting and matching the load on the motor with the speed and force of pressing the pedal;
• protection of the motor from any overload;
• admission to partial or full manual transmission control.

Types of automatic transmission

Automatic transmissions of modern cars can be divided into several types, differing in the control system and control over the operation of an automatic transmission. The first type of transmission is controlled by a hydraulic device, while the second is controlled by an electronic valve.

Types of automatic transmission

The internals of both transmissions are identical, however there are several layout differences that each automatic transmission has.

All 3 types of automatic boxes will be briefly considered in more detail in order to understand their difference between themselves and the principle of operation.

Types of automatic transmissions - briefly about the main thing.

Hydro-automatic - classic automatic transmission

The hydraulic type of automatic transmission is the simplest automatic transmission. Such a box excludes a direct connection between the engine and the wheels. The torque is transmitted in it by two turbines and a working fluid. Due to the improvement of the mechanism, a specialized electronic device appeared in such a box, which was also able to add such modes of operation as: "winter", "sport", economical driving.

One of the main disadvantages, in comparison with, is a little more fuel consumption and acceleration time.

Robotic automatic transmission

MTA popularly sounds like a DSG robot, structurally the most similar to a manual transmission, but in terms of control it is a typical automatic transmission, which, as a result of evolution, not only reduce fuel consumption, but also a number of other advantages, naturally with its own nuances.

CVT transmission

Although it is considered an automatic transmission, it is fundamentally different both in design and in principle of operation. In such a gearbox, there are no stages since there is no fixed gear ratio. Drivers who are accustomed to listening to the engine of their car cannot track its operation, because the torque in the CVT box changes smoothly and the tonality of the engine does not change.

Automatic transmission components

• torque converter, which replaces the clutch, and does not require the participation and management of the driver.
• instead of a block of gears in the automatic transmission is installed planetary gear set... This part helps to change the attitude in the automatic transmission when shifting the transmission.
• front and rear clutch, as well as a brake band, thanks to which the gear changes are carried out directly.
• the last and most important detail is control device, which is an assembly of the gearbox pan, pump and valve box that performs control functions. This component transmits movement data by means of signs that transmit a signal to the action of the automatic transmission itself.

The device and operation of an automatic transmission.

Of all the main components, we will pay the most attention to the torque converter of the gearbox.

The torque converter includes:

1. centrifugal pump;
2. stator;
3. centripetal turbine;
4. pump wheel;
5. turbine wheel;

The stator is a guide vane that is located between these parts. The pump wheel is connected to the crankshaft of the engine, and the turbine wheel is connected to the gearbox shaft. The reactor has 2 functions. It can be rotated or blocked by a freewheel.

The main task of the torque converter is to absorb strong shocks that are transmitted by the transmission to the engine and vice versa. This machine extends the life of these parts. With the help of liquid oil, torque is transferred from the engine to the automatic transmission.

In order for the automatic transmission to work for a long time and properly, it is necessary to regularly undergo diagnostics at a service station.

Pay attention to the following details:

• gears should be switched in 1 second, maximum time - 1.5 seconds;
• switching notification is carried out by light jerks;
• gear shifting should be quiet.

How an automatic transmission works

In a classic hydromechanical automatic transmission, gear shifting occurs due to the interaction of planetary mechanisms and a hydromechanical drive using electronic devices.

How to use a classic automatic transmission correctly?

Features of automatic transmission operation

• Automatic transmission need to warm up well before you start moving (this is especially true in winter).
• When operating an automatic transmission, translate selector lever in P and R positions while driving, strongly Not recommended.
• It is unnecessary to engage in neutral gear while descending the mountain, supposedly fuel economy, - it will not be there anyway, but problems with braking may arise.
• Engine braking is not possible in all gearbox modes. This point of operation must be studied in detail in the manual for a particular car; neglect of such a feature can cost expensive repairs.

Automatic transmission problems and remedies

The most common automatic transmission problems are considered to be:

• pronounced jerk when changing gear, as well as noise when moving the selector lever to another position;
• quite often in automatic gearboxes, the brake band of the front and rear clutch breaks;
• failure of the electrical or valve body.

The appearance of the car gave the start to an incessant race to improve all the systems and mechanisms of this vehicle. From methods and materials for the bodywork to high-tech control methods. Karl Benz invented the first device that allows the transmission of engine forces to the chassis in several modes.

The progressive thought of several generations of designers and inventors brought this device to the gearbox we know today. But car manufacturers were not going to dwell on this, and already at the beginning of the last century, attempts to automate this process began. By the 30s of the XX century, manufacturers came close to solving the problem. But it was impossible to establish mass production either technologically or economically, although it was possible to create successful prototypes.

The first production car with an automatic transmission is considered to be the Buick Roadmaster, released in 1947.... The first model had only two gears, but a few years later a three-speed automatic transmission was launched into a series, which has not fundamentally changed to this day, although the modern transmission has become several orders of magnitude more accurate and more complex.

How automatic transmission works and its types

There is no clutch pedal on machines with an automatic machine, except for those models where the possibility of switching to manual control is provided. This critical role is played by the automatic transmission.... The energy of the engine is transmitted through a complex mechanism, which will be discussed below, to the transmission. The device of the system is designed in such a way that the switching of modes is regulated by automatic equipment. How this happens can be understood by understanding the operation algorithm and the main components of the automatic transmission:

• torque converter... Represents the evolution of a clutch developed back in 1903. The place where torque is transmitted from the engine to the output shaft. The principle is simple. A pumping turbine connected to the engine propels oil inside the housing, which transfers energy to the blades of the gearbox mechanism. Thus, there is no rigid mechanical connection between the input and output shafts.... This does not transform the torque. It provides an additional element called the rotor. It is located between the turbines and the special design of the blades gives additional torque to the power plant. The force is transferred to the mechanism directly responsible for changing the gear ratio;
• planetary reductor... The main part of the automatic transmission. A complex mechanism assembled from a central or sun gear, a crown or large central gear and a set of satellites attached to a part called a carrier. By changing the position of the individual elements of the automatic transmission along the axis, several combinations are formed, transmitting several speeds of rotation of the central shaft at the output. The number of options is called transfers.... Direct analogue with manual transmission, but the circuit does not need a clutch, the function of which is performed by a fluid coupling. Such a system requires precise and complex control. It is impossible to provide effective switching of such a complex mechanism in manual mode;
• control system... Two types of devices are possible. The first is hydraulic mechanisms. Today this type is used mainly in budget cars. Cars of the middle class and above are equipped with an electronically controlled automatic transmission. In the first case, the sensors, reacting to a change in the oil pressure in the system, activate the hydraulic pushers. They activate a complex combination of clutches and brakes by mechanically changing gears. The system is configured in such a way that it is impossible to "jump" over the transmission. Switching is only possible sequential. The electronic control system is more efficient. Sensors collect more complete information about the operation of the automatic transmission. This is both the temperature of the liquid and the rotational speed of each axis. The control unit gives a signal to the actuators. The operation algorithm of a whole group of parts at once is under the control of electronics. Clutches, brakes, and solenoids, often referred to as solenoids, are almost constantly in motion while driving;
• selector lever... This is the "handle" in the cabin. All over the world, the marking of selector positions common to all automatic transmissions has been adopted. R - reverse. N - neutral gear. D - the main position of the selector when driving, from start to stop. P - Parking. S - sport mode... Some manufacturers of luxury and executive cars provide the switching unit with additional positions. For example, Tiptronic has the ability to switch from automatic mode to mechanical control of the gearbox.

The scheme considered above refers to the classic version. The principle of operation of variators and robots is different. The difference in price is also significant.

Well-developed technologies, large volumes of production of a classic automatic transmission make it more accessible to both the variator and the robotic box, which, however, have some advantages.

For example, the variator has no shifting stages at all, and the gear ratio changes are carried out by a mechanism that resembles two tapered pulleys. The moving belt simultaneously changes the input and output diameter of the shafts, which changes the output speed without power loss and jerks. The robot, on the other hand, is essentially a high-quality manual transmission with effective electronic control. Lovers of mechanics can always switch to their favorite mode.

Advantages and disadvantages

Automatic transmission has many advantages. Operating mechanics requires a lot of training and constant attention while driving. This problem does not concern owners of cars with automatic equipment. Most of the time at the moment of driving, the box is in one position - D, which means movement or drive. But these are not all bonuses. The advantages are as follows:

1. Comfort and focus on the road environment, not on devices.
2. Conservation of engine resource. The machine does not allow the mechanic to work in critical modes, which prevents wear of the main parts and consumables.
3. Safe driving in difficult climates. Together with other systems, the machine does not allow the driver to make critical mistakes in control.

However, not only pluses are noted by specialists and ordinary car owners. There are also disadvantages:

1. Higher fuel consumption than manual transmission. The efficiency of the machine can be up to 12% lower than that of mechanics. However, this does not apply to the latest generation of automatic transmissions. Improving production technology today minimizes this difference.
2. Dynamics. Automatic mode does not allow the car's systems to work in extreme conditions, which deprives the driver of the full experience of all the power and capabilities of the car. But for most city dwellers, this is not relevant. In everyday life, where the promotion is complicated by traffic jams and traffic lights, the machine is more a blessing than a disadvantage.
3. The cost of the car. Models with automatic transmission are much more expensive than their manual transmission counterparts.
4. Impossibility of towing. If the automatic transmission breaks down, you have to call a tow truck. The ability to move the switched off car is limited to a short distance at minimum speed, and even then with experience and knowledge of how to do this it is safe for the mechanics of the car.
5. Repair. The complexity of the design and the high price of spare parts and maintenance, which includes a large number of consumables, makes the owners of cars with automatic transmissions fork out.

How to properly operate a car with an automatic transmission

There are no difficulties in training and subsequent operation. Unlike mechanics, you do not need to look at the tachometer needle or determine the moment of switching by sound. The machine handle positions are as follows:

• Parking. It is designated by the letter P. In this position, the lockable output shaft prevents the vehicle from moving. On level ground, this is sufficient to maintain stability, but on an inclined surface, it is recommended to use the hand brake;
• The position of the N handle corresponds to neutral on the manual transmission. With the control system off, the machine can be moved;
• Reverse is indicated by the letter R, which means reverse. In this position, it is impossible to start the engine, and when moving forward, a sharp shift of the selector to reverse will certainly disable the gearbox;
• The main position is marked on the selector with the letter D. All gears are shifted forward, from lowest to highest, in this mode.
• Additional provisions. These include the Sport mode, marked S. This mode makes the most of the engine power. Acceleration dynamics is noticeably higher for cars with the additional Kickdown option. The Overdrive function is available for even and economical driving. Some models have a separate switch for winter mode. If the automatic transmission breaks down, the automatics can lock the mechanism in the current gear and go into emergency mode.

Features of operating a car with automatic transmission

The order of operations required to start driving on most cars with a gun is the same:

1. Insert the key and turn it to ignition mode.
2. Press the brake pedal.
3. Move the selector handle to the desired position. Either forward or backward.
4. Release the brake pedal.

The car will begin to move smoothly in the chosen direction, without even pressing the pedal, using which you can accelerate the dynamics. The machine primarily responds to the operation of the accelerator. The "Drive" mode is not switched during short stops, for example, at a traffic light... Only the brake is used. The "Parking" position is turned on for a longer stop.

• Off-road and uneven surfaces should be avoided. Ideally, slipping should be avoided altogether;
• Let the system warm up. The automatic transmission will reach the declared level only at a certain oil temperature. Therefore, even in the summer, it is better to avoid sudden accelerations and high speeds for the first few minutes of movement;
• Do not overload. The machine has more sensitive mechanics, which are designed for certain loads. Overloading the cabin or pulling a heavy trailer is strongly discouraged;
• You need to pay attention to the documentation. Is towing allowed for this type of automatic transmission. Some models are not subject to forced movement at all. Some species have strict speed and distance limits.

The global trend today is, of course, cars with automatic transmission. Performance in many respects approached highly skilled driving on a mechanic. Conveniences are undeniable and do not need additional advertising.

An automatic transmission is a device that allows the gear ratio to be selected in accordance with road conditions, terrain and speed without the direct involvement of the driver. In a car equipped with an automatic transmission, the accelerator (gas pedal) sets the speed at which the car is moving, and does not determine the engine speed - this is the principle of the automatic transmission.

History shows that the automatic transmission was invented somewhere in the thirties of the twentieth century. Since the very appearance of such a transmission, the principle of operation of an automatic transmission has practically not changed, but depending on the time and certain technical requirements, it has been constantly supplemented. Thanks to such additions, automatic transmissions appeared, differing in their options, models. They also have different technical characteristics from different manufacturers.

With distinctive characteristics, all automatic transmissions have one principle of operation. This is due to the fact that they have almost the same device, if you do not take into account some small nuances.

Automatic transmission device

Automatic transmission device

• The main one is the torque converter, which is also called the fluid coupling - this is a mechanism located between the engine of the machine and the gearbox housing. The functional task of the fluid coupling is the transmission and redistribution of torque during the start of the car;
• Torque is transmitted indirectly using planetary gearboxes;
• Friction clutches are responsible for the choice of a particular gear, they are often called a "package";
• One of the mechanisms is the overrunning clutch, which mainly performs the function of reducing the impacts in "bursts" during gear changes. In some cases, when the automatic transmission is operating, the freewheel disables engine braking;
• The box device also includes drums and connecting shafts;

The principle by which the automatic transmission works

To control the automatic transmission, there is a special set of so-called spools that direct oil under a certain pressure to the pistons located in the friction clutches and brake bands. It is possible to set the position of the spools in automatic or manual mode, using the gear shift knob.

You also need to know that the automation that controls the automatic transmission can be hydraulic and electronic. Hydraulic is an automation that uses oil pressure received from a centrifugal regulator. In turn, the centrifugal regulator is connected to the automatic transmission shaft, which is located at the outlet. The hydraulic system is designed to use oil pressure in accordance with the position of the accelerator. The machine receives information about the position in which the gas pedal is located - this is a command for the spools to switch.

Automatic transmission scheme

The electronic control system contains solenoids that are responsible for moving the spools. The solenoids are connected to the automatic transmission control unit by cables; it is also possible to connect them with the control of the ignition and fuel injection system. In this case, the movement of the solenoids is controlled by the electronic control unit. The block also controls the solenoids depending on the position of the gear shift knob, the speed at which the vehicle is moving and the position of the accelerator.

Features of using automatic transmission

In order to avoid various breakdowns and troubles, you need to know how the automatic transmission works and how to use it. Automatic vehicles are very practical and comfortable vehicles. Even though many car enthusiasts are skeptical about such transmissions, they are very popular. Usually it all depends on what the person is used to. If the driver loves dynamics, speed, then automatic transmission is not an option for him. Having considered the device, technical characteristics and how the automatic transmission works, it becomes clear that it is intended for people who prefer a more relaxed driving style.

The torque converter performs the function of smoothly connecting the box to the engine

In any case, before you start to master a car with an automatic machine, you need to study all the nuances and rules for using such a transmission. It is important to understand that neglecting some of the features, you can disable the automatic transmission in a fairly short time. You also need to know that the repair or replacement of the entire automatic transmission will cost a lot of money.

Rules for operating the machine

Even if the entire transmission is electronically controlled, the driver is required to follow certain rules for controlling it using the gear selector knob:

At the moment, there are several types of transmissions in the automotive world. But the most popular are only two. It is an automatic machine and a mechanic. The latter appeared ...

From Masterweb

At the moment, there are several types of transmissions in the automotive world. But the most popular are only two. It is an automatic machine and a mechanic. The latter appeared earlier, but now it is gradually being replaced by automatic transmission. The machine is much more convenient to use, and in terms of reliability, this box is no worse. Today we will pay special attention to this type of transmission. The device, the principle of operation of an automatic transmission and much more - further in our article.

Characteristic

So what is an automatic transmission? This is a device used to change the torque that is supplied from the engine to the drive wheels of the car. The automatic transmission is also referred to as a hydromechanical transmission.

What brands is this transmission installed on today? At the moment, almost every automaker practices the installation of automatic transmissions. Here are the brands on which the automatic transmission is installed:

• "Toyota".
• Audi.
• BMW.
• Nissan.
• Volkswagen.
• Skoda.
• Renault.
• Citroen.
• Peugeot.
• Mercedes.
• Chevrolet and many others.

Moreover, this mechanism has approximately the same structure and principle of operation. So, this node consists of:

• Torque converter.
• Planetary row (manual transmission).
• Control systems.

If we talk about front-wheel drive cars with an automatic transmission, the unit also includes:

• Differential.
• Main gear.

These elements are located directly in the box, and are not separate units, as on rear-wheel drive cars. So, let's take a closer look at the automatic transmission device.

Torque converter

This element serves to change and transfer torque from the flywheel of the internal combustion engine to a manual transmission. In addition, the torque converter helps to reduce vibrations that occur when starting the movement and when changing gears. The GDF design includes:

• Reactor wheel.
• Turbine.
• Freewheel clutch.
• Blocking clutch.

The converter has blades of a certain shape. Between them are channels for the circulation of the ATP liquid. As for the last item on the list, it serves to block the GTP in certain vehicle modes. And the freewheel allows the reactor wheel to rotate in the opposite direction. All elements of the GTP are enclosed in a single body. Inside it, there is always an ATP liquid.

Principle of operation

The torque converter operates in a closed loop. Thus, the flow of ATP liquid is transferred first to the turbine and then to the reactor wheel. Since both have blades of a certain shape, the flow rate increases. The liquid is directed to the impeller and increases its speed. This also increases the torque. The highest torque values ​​are usually achieved at minimum speed (that is, when the first gear is engaged).

With an increase in engine speed, the speed of rotation of both wheels becomes equal. This activates the blocking clutch. In this case, power is transferred directly to the manual transmission. The torque converter is locked in each gear when the rotation speed of the turbine and reactor wheels is equalized.

Note that in some automatic transmissions, the locking principle is somewhat different. So, in the automatic transmission there is a mode with a slipping clutch. It prevents complete blocking. Where is this mode used? This is necessary in conditions of acceleration and high loads. Also, this mode allows you to reduce fuel consumption and with it a smoother gear shifting is carried out.

Planetary row

This is the very same manual transmission that is part of the automatic transmission. What is this node for? It allows you to change the gear ratio, thereby adjusting the amount of torque and vehicle speed. The mechanical gearbox consists of two planetary gearboxes. They are connected in series with each other. It is necessary for them to work together and to ensure the required number of steps. Previously, only four-speed automatic transmissions were practiced on cars. Now the number of steps has increased to six (and some manufacturers also practice nine-speed boxes).

Each planetary gear consists of:

• Crown gear.
• Drove.
• Sun gear.
• Satellites.

Torque transmission is possible only if one or two of the above elements of the planetary gear set are blocked. So, thanks to the stationary sun gear, the gear ratio is reduced. And when the crown is blocked, it, on the contrary, increases. The blocking itself is carried out by the clutches and brakes. The latter allow you to hold certain parts of the automatic transmission gearbox due to the connection with the transmission housing. Brakes can be tape type or multi-disc. They, together with the clutch, are closed by means of hydraulic cylinders. Also, the automatic transmission device has a clutch that holds the carrier and does not allow it to rotate in the other direction.

Thus, the principle of operation of an automatic transmission is based on a specific algorithm for disengaging and activating different clutches and brakes.

Automatic transmission control system

Most modern boxes have an electronic control system. It includes:

• Electronic control unit.
• Input sensors.
• Selector lever.
• Distribution module.

A number of additional sensors are also used in the automatic transmission system:

• Temperatures of the ATP liquid.
• Rotation frequencies at the inlet and outlet of the box.
• Positions of the gas pedal and automatic transmission selector.

The automatic transmission ECU processes the incoming signals from the sensors and then activates the actuators. It is worth saying that the electronic unit of the box closely interacts with the engine ECU.

Valve body

The distribution module is also called a hydraulic block. This unit controls the oil flow and ensures that the clutch brakes are applied. The valve body consists of:

• Solenoid valves (solenoids).
• spool valves. They are mechanically driven and housed in an aluminum housing.

Solenoids are used to switch gears in an automatic transmission by changing the fluid pressure. For this, their device has two-position valves. These elements act on the basis of signals from the electronic control unit. As for the spools, they serve to select the operating modes of the box. They are controlled by the automatic transmission selector itself.

Pump, cooling

In order for the working fluid to circulate in the system under pressure, the automatic transmission device has a gear-type pump with internal gearing. Some boxes use a paddle element. But regardless of the type, the pump is driven by the GTP hub.

During the operation of the automatic transmission, the fluid heats up significantly. In view of this, a cooling system is provided in the design of the box. It assumes the presence of a special heat exchanger, which is included in the engine cooling system. In some cases, a separate radiator for the ATP fluid is used, placed in the front of the car.

Benefits of automatic transmission

Let's consider the main advantages of this transmission. Why did she become so popular? First of all, the automatic transmission is relevant for its ease of use. So, this box is much easier to learn how to operate (how exactly to drive a car with an automatic transmission, we will consider a little later). The driver can fully concentrate on the road conditions without worrying about grip and what speed to apply. Everything happens automatically. It is especially convenient to use a car with an automatic transmission in large cities, where frequent traffic jams are possible. The driver is much less tired as there is no need to play with the clutch.

The next plus of the automatic transmission is the smoothness of the ride. Such a box works smoother than a mechanic. The beginning of the movement is carried out without jerking. Also, many transmissions have various auxiliary modes and additional functions. It is worth noting the winter as well as the sports mode. Some cars have a mode for driving through mud and other surfaces. The box adapts itself to the given conditions.

Disadvantages of automatic transmission

But there is also a downside to the coin. First of all, it is worth noting the expensive maintenance. Take, for example, the price of an ATP liquid. One liter of it costs from a thousand rubles, while for mechanics, oil will cost 3-5 times cheaper. Also worth noting is the expensive renovation. The automatic transmission is more complicated than the mechanics. Therefore, the cost of repairs will always be 2 times higher.

The next disadvantage concerns operating restrictions. For example, a car with an automatic transmission must not be towed by a cable or in any other way. This leads to breakdowns in the automatic transmission. If the car breaks down on the way, you only need to call a tow truck.

There is one more disadvantage. This is fuel consumption. This is especially true for old four-band automatic transmissions. They are practically not used now, but you can still find them on Logans and other budget cars. So, one and the same engine on the machine will consume 10-15 percent more fuel than with mechanics. Modern six-speed gearboxes have less difference in consumption. However, owners of four-speed automatic transmissions take a long time to get used to the expense. It is not uncommon for a 1.6-liter "Logan" to spend up to 14 liters of gasoline in the city on such a machine. With mechanics under the same conditions, the car consumes no more than ten.

And perhaps one of the main drawbacks is the overclocking dynamics. It is for this reason that many abandon automatic transmission in favor of mechanics. So, a car with a machine gun will always be half a second slower than with the same engine, but on mechanics (meaning acceleration to one hundred kilometers per hour). Yes, some boxes have a manual shift option as well as a sport mode. But if we talk about B-class cars, all the same, this does not bring the acceleration speed much closer to the manual transmission.

Maintenance and repair of an automatic transmission

It is worth noting that each automatic transmission, regardless of the year of manufacture and the number of stages, needs periodic maintenance. This operation involves changing the oil. In an automatic transmission, it is subjected to higher loads because it circulates in the system under pressure and allows the transmission of torque. the regulations for each manufacturer are different. However, on average, an oil change should be carried out every 60-70 thousand kilometers.

How can you make a replacement? There are two methods in total:

• Partial. In this case, the oil does not change completely. So, first, old fluid is poured out of the drain hole. Typically, its volume is no more than 50 percent of the filling. After that, new oil is poured into the box through the dipstick. Its volume must be identical to the one that was leaked earlier. The advantage of this method is that you can do it yourself. All you need is a pit and an extension tube. But there is also a drawback. Due to the fact that the oil is not completely drained, it must be replaced twice as often. Thus, in the event of a partial replacement, the box requires attention not every 60, but 30 thousand kilometers.
• Complete. In this case, special vacuum equipment is used. The pump pumps out the entire volume of oil from the system, simultaneously driving new oil. This is a more correct replacement method, but it has a couple of drawbacks. So, this method cannot be applied with your own hands. In addition, the cost of such a replacement will be several times higher. Indeed, in addition to the cost of the master's work, you will need to purchase more ATP liquid. Typically, with a filling volume of 8 liters, about 12 liters are required for replacement.

Now about the repair. The most harmless operation is considered to be the replacement of oil seals and gaskets. As a rule, the wear of the sealing elements is evidenced by the leakage of oil on the case of the box. One of the most common operations is replacing the automatic transmission oil pan gasket.

There are also more serious repair methods. So, over time, the valve body may become dirty. This is usually dirt from the clutch packs. As a result, the spools cease to function normally, and the box begins to kick. The repair technology consists in disassembling the valve body and replacing the failed spools. In some cases, only cleaning the hydraulic plate helps.

Repair may be required in the event of a malfunction of the solenoids. The reason for their failure is trivial. These are small deposits in the oil that somehow got from the filter to the valves. As a result, the latter begin to jam and work incorrectly. The repair consists in replacing the bronze bushings and solenoid rings.

If this problem is not eliminated in time, the gap between the ring and the shaft housing will increase. This will cause oil to seep into the gap. And since the pressure in the block will drop, the pump is forced to pump oil more intensively (in order to compress the clutches). This happens until the automatic transmission pump is completely exhausted. A characteristic sign of a worn-out pump is an increased hum and howl when the automatic transmission is operating.

The electronic control unit of the box can also fail. Because of this, the electronics cannot correctly send signals to the actuators. The box is not able to change gear at high speeds, or the changes are jerky. Also, the box can get up in emergency mode. Automatic transmission repair in this case consists in replacing the unit or restoring the loops in case of damage.

As for the cost of repairing a transmission, the price depends largely on the nature of the breakdown. But often the price ranges from 30 to 90 thousand rubles.

About replacing automatic transmission

When is it advisable to replace an automatic transmission? This operation may be required in case of failure of large elements. It could be a planetary gear set. Also, replacing an automatic transmission is relevant if several systems are out of order at once. In this case, repairs will be expensive, and buying a whole box for disassembly will be cheaper. But as a rule, such actions are resorted to in the case of a high mileage of the box (300 or more thousand kilometers).

How to use an automatic transmission?

The automatic transmission has differences not only in the principle of operation, but also in use. So, consider driving a car with an automatic transmission. First, we need to start the car. In this case, the gearbox selector must be in the "Parking" position. Next, we squeeze the brake pedal (with the right foot) and turn on the mode we need. Recall that there are only a few of them:

• "Parking".
• "Reverse" (reverse gear).
• "Neutral"
• "Drive" (moving forward).

To start driving, you should move the gearbox selector to the "Drive" position. After that, move your foot to the accelerator pedal. Do not forget to remove the car from the parking brake first, if it was previously installed on it.

Driving with an automatic transmission has its own nuances. So, beginners are wondering whether it is necessary to transfer the selector to the "neutral" mode when the car is stationary (for example, in a traffic jam or at a traffic light). Experts give the following answer. It is worthwhile to transfer the automatic transmission selector to neutral mode only when the car has been stationary for a very long time (more than a minute), and keeping your foot on the brake constantly is already problematic. If the stop is short, do not switch to neutral mode. Indeed, in this case, the box is significantly loaded: the friction packs are opened, the shafts are disengaged and the solenoids are closed. And when you switch to "drive" mode, this whole process is repeated.

Thus, switching the automatic transmission to neutral should only be done in case of prolonged downtime. Otherwise, the transmission suffers significant loads. It is worth knowing that the principle of operation of an automatic transmission, in contrast to mechanics, is different, and here it will not be possible to just throw the lever into "neutral". This is especially not worth doing on the go, trying to coast. This can lead to irreversible consequences. As a result, the box kicks and the clutches slip. Yes, this does not happen immediately. But if you constantly operate the transmission in this way, you can soon get to its expensive repair. There are a lot of cases when the same box drove 100 thousand kilometers for some owners, and for others - 300 without repair. The reason for such a high resource is trivial. This is the correct operation of the transmission and its timely maintenance.

Conclusion

So, we found out what an automatic transmission is and how to use it. No matter how scolded this transmission, cars with an automatic transmission are gradually replacing mechanics. Automatic transmission is more relevant in large cities. It is chosen even under the condition that the consumption with it is 5-10 percent more than on the mechanics.

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A person has always strived for comfort and driving pleasure, as a result of which an automatic transmission was invented, this made it possible to reduce the load on the driver, and it became much easier to drive a car. It was invented in the 40s of the XX century by the General Motors concern.

The automatic transmission is quite complex and includes the following mechanisms:

• torque converter - provides transmission and change of torque from the power unit;
• gearbox - converts effort and drives the wheels;
• control system - controls the working fluid;
• lubrication and cooling system - creates pressure and circulation in the system.

Torque converter

Torque converter

Replaces the standard clutch for a manual transmission, and is also located between the transmission and the engine, attached to its flywheel. Its main task is a smooth change, transmission of torque to the drive shaft of the automatic transmission. Its design includes such elements as: pump, turbine, reactor wheels, freewheel and blocking clutch. The impeller is attached to the converter housing and rotates with it. The turbine wheel sits on the drive shaft of the planetary gearbox. On each of the wheels there are blades of a certain shape; when the engine is running, a working fluid begins to pass between them, with which it is filled.

As soon as the engine starts, the impeller begins to rotate and its blades pick up the working fluid directing it to the blades of the turbine wheel, from which it flies off to the reactor wheel (reactor) located between them. The reactor directs the flow of the returning liquid towards the direction of the impeller, two forces begin to rotate it, due to which the moment increases. When the revolutions of the pump and turbine wheels are compared, the freewheel clutch is triggered and the reactor begins to spin due to it, this moment is called the clutch point. After that, the torque converter begins to work as a fluid coupling, rotation from the engine begins to be transmitted to the drive shaft of the planetary gearbox through the working fluid. An exception is the Honda automatic transmission, where instead of a planetary gearbox, shafts with gears are installed as on manual transmissions.

But still not 100% of the power is transferred from the engine due to the viscous friction of the oil. To eliminate these costs and use it as efficiently as possible, which ultimately leads to a decrease in engine fuel consumption, there is a lock-up clutch, which turns on at about 60 km / h and more. This clutch is located on the turbine hub. As soon as the car picks up the required speed, the working fluid enters the wall of the lockup clutch on one side, and on the other, it comes up after opening the channel with the switching valve, thereby creating a low pressure zone. Due to the pressure difference, the locking piston is triggered, at this moment it is pressed against the converter housing, as a result of which the clutch begins to rotate with the converter housing.

Transmission

Different manufacturers may differ slightly, but they all have: the planetary gearbox is also called differential, overrunning and friction clutches that connect all the mechanisms, shafts, drums that act as clutches, and in some models, a brake band is used to brake the drums.

Usually consists of several planetary gear sets, clutches and brakes. Each of the planetary gears is structurally made of a sun gear and satellites, they are connected by a planetary carrier. Rotation is transmitted when one or two gearbox elements are blocked. When the carrier is blocked, the direction changes, which corresponds to the car's reverse motion. When the ring gear is locked, the gear ratio increases, and when the sun gear is locked, it decreases, this is a gear change.

Friction clutch

To hold the gearbox elements, brakes are used, and friction clutches (clutches) are used to fix the parts of the planetary gear set. Each such clutch includes a drum on the inside of which there are splines and a hub with teeth on the outside. Two types of friction discs are placed between them, the first with projections on the outside, which enter the splines of the drum, the second with projections on the inside, where the teeth of the hub enter. The clutch is triggered when the disks are squeezed by the piston inside the drum at the moment the working fluid enters it.

Overrunning clutch

It restrains the carrier from rotating in the opposite direction to reduce shocks during engaging the gear and prevents engine braking in certain operating modes of the box.

Honda Feature

Twin-shaft automatic transmission Honda

It has already been mentioned that Honda's gearboxes are different from all other automatic machines, in fact, they are ordinary mechanics with hydraulic control. The advantages of these boxes are reliability, since there is practically nothing to break there, they are easier to repair and manufacture. Such boxes consist of two or more shafts with gears and by turning on a certain combination of gears, the gear ratio changes.

One gear in each pair is constantly interlocked with its shaft, the second is connected to its own through the so-called wet clutch (friction clutch for engaging a gear), that is, all gears rotate, but one of the pair is not interlocked with the shaft and, accordingly, the torque and rotation are not transmitted to the wheels of the vehicle (neutral). The device and the principle of operation of the clutch, as on conventional machines. When the discs are compressed, the second gear meshes with its shaft, the corresponding gear is engaged.

The rear one is realized on the clutch of one of the gears. On the shaft next to the gear of one gear there is a reversible gear, these two gears are not rigidly fixed on the shaft, between them there is a bushing with teeth fixed on this shaft, and on this bushing there is an annular clutch with teeth. And depending on which side this clutch will be moved, that gear is engaged with the shaft, the annular clutch is displaced using a fork with a hydraulic drive. The reversing gear changes the direction of rotation, reverse gear is engaged.

Control system

Distributes the flow of working fluid (ATF), it consists of a set of spools, oil pump, valve body. There are two types of systems, hydraulic or electronic.

Hydraulic system

Uses oil pressure from the throttle valve, depending on the load at the moment, a centrifugal regulator connected to the output shaft of the automatic transmission. The working fluid from these regulators comes to the spool and acts on it from different sides, and depending on the pressure difference, it moves to one side or the other, opening the necessary channels, this determines which gear the box will switch to.

Electronic system

With this system, more flexible operating modes can be achieved that cannot be achieved with a fully hydraulic system. It uses solenoids (solenoid valves) to move the spools. The operation of all solenoids is controlled by the electronic control unit (ECU) of the box, sometimes combined with the engine ECU. Based on the readings from the speed sensor, oil temperature, gas pedal and gear lever, it gives signals to the solenoids. Solenoid valves are divided into pressure control, changeover control, flow distribution.

The regulating ones form and maintain within a predetermined value the pressure of the working fluid, which depends on the state of the car. The shift valves control the gears by supplying fluid to the shift clutches. Distributing flows direct fluid from one channel of the valve body to another.

When the automatic transmission mode is selected with the selector lever, a signal is sent to the mode control valve via mechanical or electronic communication. It directs ATF only to those valves that can be used to engage the gears allowed in this mode.

Valve body

Valve body device

The most complex automatic transmission unit, it consists of a metal plate with a large number of channels and the entire mechanical part of the control system (spools, solenoids). The fluid flows are redistributed in it, and through it ATF with the required pressure is provided to all elements of the mechanical part of the box.

Oil pump

It is located inside the gearbox and can be of different types (gear, trochoid, vane), can be completely controlled by electronics or have a mechanical connection with the torque converter and the engine. It continuously circulates ATF and builds up pressure in the system. The pump itself does not create pressure, but fills the hydraulic system with a working fluid, and pressure begins to form in the valve body with the help of dead-end channels. In modern automatic transmissions, an automatic (electronic) pump is increasingly used, which allows the pressure to be maintained in an optimal way.

Lubrication and cooling system

It is very important for the normal functioning of the gearbox, therefore it uses a special ATF hydraulic fluid, it is she who lubricates and cools the moving elements. The working fluid is cooled in a cooling radiator, which can be internal and external. An internal radiator (which is a heat exchanger) is located inside the engine coolant radiator. There are also more complex heat exchangers that have their own liquid cooling, they are installed on the box body. The external one is located separately and is a full-fledged radiator. On some cars, a thermostat is built into the cooling line from the automatic transmission to the radiator, which regulates the volume of oil passed through it. To prevent contamination of the system channels with particles that are formed during the wear of moving parts, a filter is installed, it cleans the working fluid.

Automatic transmission with external oil cooler

Automatic transmission with a built-in cooling radiator in the engine radiator

Automatic transmission oil cooling radiator with liquid cooling system

The gearbox is controlled by selecting the required operating mode with the selector lever. Different models may have a different combination of operating modes:

• R(Neutral) - long-term parking mode;
• N(Parking) - for short-term parking or towing;
• R(Reverse) - backward movement;
• L1, 2, 3(Low) - lowering is designed for driving in difficult road conditions (rough terrain, steep descent or ascent);
• D(Drive) - movement forward, is the main mode;
• D2 / D3- modes limiting gear shifting;
• S, P(Sport, Power, Shift) - sports driving mode;
• E(Econ) - provides a more economical driving style;
• W(Winter, Snow) - winter mode, provides for a soft start from an increased gear to prevent slipping, gear change is carried out at a reduced speed;
• +/- - function of manual gear shifting.

Some models have O / D(Overdrive) - a special button that allows you to switch to an overdrive, there is also a mode kick-down, which forcibly turns on a downshift when you press the gas pedal sharply, due to which more intense acceleration is provided.

We tried to disassemble the AKP device in the most detailed and accessible way, the principle of operation of individual elements and their interaction. But technologies do not stand still, perhaps already now they are introducing new principles of work that will appeal to any layman.