The device of the automatic transmission of the vehicle and operation. Types of automatic transmission

In recent years, automatic transmissions are gaining increasing popularity. And for good reason. This box is more easy to operate and does not require constant “game” clutch in traffic jams. In large cities such transmission is not uncommon. But the device of the automatic transmission is significantly different from classical mechanics. Many motorists are afraid to take the car with such a gearbox. However, their fears are not justified. For proper operation of the automatic box will last no less than mechanics. But in order better to understand it, should study in detail the device of the automatic transmission of the vehicle. We will tell you in our today's article.

Varieties

There are several types of data boxes. So, distinguish:

• Hydro-mechanical automatic transmission.
• Robotic (DSG).
• Variable speed.

What is the features of each of them? Consider the below.

Classic automatic

Hydromechanical transmission – the most common type of automatic transmission. The device of such a box implies a torque Converter, mechanical transmission and control system. But such a design is practiced on cars with rear wheel drive. If it is a front wheel drive car, the transmission device adds the differential and main gear.

The torque Converter (common name – “donut”) – is the primary node in this transmission. It serves to modify and transmit torque from the engine flywheel to the mechanical box. Also, the bagel serves for damping oscillations and vibrations which occur during the transmission torque forces from the engine.

The torque Converter consists of several wheels. This:

• Turbine.
• Reactor.
• The impeller.

Once the design consists of two coupling – lock-up and freewheel. All these parts are enclosed in a separate toroidal housing which outwardly resembles a bagel (and from such a specific name).

The impeller is connected with the crankshaft of the motor. The turbine interacts with a manual transmission. Between these two elements is the reaction wheel. It, unlike all the others, is stationary. Each wheel hydraulic transformer automatic transmission has blades between which passes the working ATF fluid.

The lock-up clutch of the automatic transmission is designed to block GTP (donut) in specific engine operating conditions. A freewheel (also known as overrunning) of the reactor rotates the wheel in the opposite direction.

Job GTF

It is a closed cycle. So, ATF fluid begins to flow from the pump to the turbine, and then – in reaction wheel due to the special shape of the blades, the speed of the oil flow begins to increase steadily. ATF fluid makes faster to rotate the impeller. This increases the strength of torque. By the way, the maximum of the parameter is achieved at minimum speeds. This is necessary to ensure that the machine freely moved even under load. When the car starts to gain speed, actuates the clutch and locks the torque Converter. In this situation, made a direct torque transmission. It should be noted that the lockup clutch is activated in the automatic transmission in all gears, including at the rear.

In the modern cars use the slip clutch. This mode allows you to prevent the complete locking mechanism, which has a positive effect on fuel consumption and smooth drive.

Planetary gear

The node performs the function of a mechanical transmission. The reducer can be designed for four, six, seven or eight speeds. In rare cases, a nine-storyed automatic transmission (for example, the cars “land Rover”).

We Continue to study the structure of the automatic transmission. Planetary mechanism consists of several consecutive transmissions. They form a planetary gear set. Each of the speeds includes several elements:

• Crown gear.
• The Satellites.
• Sun gear.
• Led.

How is the change in torque? Studying the arrangement of the torque Converter of the automatic transmission, it should be noted that this operation is performed by using several elements of the planetary series. This has led, and two gears (the sun and the crown). Lock the latter allows to increase the gear ratio. Sun gear, on the contrary, reduces this ratio. A carrier performs the change of the direction of rotation of the elements.

Locking is performed using the clutch. It's kind of a brake that holds certain parts of the gear unit by linking them to the transaxle case. Depending on the brand of car («Mazda» or «Ford»), the device of the automatic transmission assumes the presence of a belt or brakes. He closes by means of hydraulic cylinders. The latter are managed from the distribution module. To prevent rotation of the carrier in a different direction, the overrunning clutch is used.

Electronic system

The structure and operation of automatic transmissions modern cars are impossible without electronic control systems. It includes:

• The control.
• The Input sensors.
• The Selector of the automatic transmission(the device will consider it later).
• Distribution module.

Note that the list of input items is quite extensive. So, this includes the sensors:

• Position the accelerator pedal.
• The temperature of the ATF fluid.
• The frequency of rotating shafts on input and output.
• The prndl.

Control Unit automatic transmission continuously processes signals that are received from data elements, and generates control pulses to the actuators. This block communicates with the engine ECU.

Control module performs the tripping of the clutches controls the flow of ATF fluid in the transmission. This module consists of spool valves and solenoid valves with a mechanical drive. These parts are enclosed in separate aluminum housing and are connected by channels.

An Important element in the automatic transmission device "Honda" is the solenoids. They are also called solenoid valves. They need to control the pressure of the transmission oil. And spools perform the operation mode box. The elements are activated from the lever to the automatic transmission.

Because the primary fluid is ATF-oil in the automatic transmission device provided with a pump of gear type. It runs from the torque Converter hub and is the basis of hydraulic transmission. Oil cooling device in the transmission «Mercedes» a special heat exchanger. It is a small radiator that is in front of the car. On some models it is enclosed with the main radiator of the engine coolant.

Selector automatic

This detail has direct control automatic transmission. There are several modes of automatic:

• Parking.
• Reverse.
• Neutral.
• Drive (move forward).

On some vehicles, “Nissan” device, the automatic transmission assumes the presence of a sport mode. For its inclusion it is necessary to translate the selector lever to position S. the Mode is characterized in that the gear shifting is performed at higher engine speeds. Thereby achieving greater torque and vehicle speed. If we consider “Nissan Qashqai”, device of the automatic transmission also implies a mode of manual switching of speeds. This box has the name "Tiptronic".

Robotized transmission of DSG

This is a development concern «Volkswagen, Audi”. There was this CAT in the mid-2000s and is installed on most passenger cars of the brand «Skoda», “Audi”, and «Volkswagen» (including the "Touareg").

A Key feature of the DSG automatic transmission – fast gear shifting without breaking the power flow. This allows to increase the productivity and efficiency of the transmission. Cars with DSG have good acceleration dynamics. While they have lower fuel consumption in comparison with classic torque converters.

The structure and operation of automatic transmissions of this type significantly differs from the previous checkpoint. So, there is no usual “donut”. Torque transmission is carried out through the use of two clutches. In addition, it can be installed anti-theft device automatic transmission of this type.

DSG Transmission

It includes:

• Dual-mass flywheel.
• Two sets of gear.
• The Main transfer and differential.
• Electronic control system.
• Double clutch.

All of this is enclosed in a metal housing box. If we talk about the double clutch, it provides power simultaneously to the first and second number of transfers. If it's a six-speed DSG, the box has a leading disk (it is connected with two-mass flywheel input hub) and the clutch. The latter are connected with the rows of gear through the main hub.

By the Way, the type of coupling may be different on DSG box. If it's a six-speed box, the design uses a wet clutch type. Oil not only provides lubrication, but also cooling of the friction discs. This significantly increases the service life of the units.

If we talk about the seven-speed transmission, are applied dry scheme. It significantly reduces the amount of used oil. If in the first case, for the work of the DSG was required not less than six and a half gallons in the second – no more than two. The pump that pumps the grease is electric. This design, according to experts, less reliable and is not very resource.

With regard to the series of gears, the first is responsible for the reverse and odd speeds. The second controls the even gears. Each of the rows represents a secondary and a primary shaft with a specific set of gears. The primary element is complete and is coaxial, and a gear rigidly connected with the shaft. At the same time, the secondary gear spin freely. Also in design is the synchronizers. They facilitate the inclusion of a speed transmission. So the car could move back in the box DSG is provided intermediate currencies it is equipped with a reverse gear.

The Management shift provides electronics. It includesvarious sensors, control unit and electro-hydraulic unit with a mass actuators. The control module is located in the sump of the automatic robotized gearbox. When you work a checkpoint, the sensors analyze the frequency of shaft rotation for output and input, oil pressure, position of plugs of inclusion of speeds, and the temperature of the lubricant. Based on these signals, the ECU implements a particular control algorithm.

Through the block manages hydraulic circuit transaxle. This system includes:

• Spools-valves. They are actuated by the gearshift lever.
• Solenoid valves. These items serve for switching speeds.
• Valves control the pressure. Thanks to them, you are working the clutch.

The Last two components relate to the Executive control mechanisms of the robotic CAT.

Also in the construction of this box is provided a multiplexer. It allows you to control the hydraulic cylinders with solenoid valves. Remarkably, the number of first half more than the second. Thus, in the initial position of the element used some cylinders and working – other.

The Algorithm robotic transmission is the sequential switching of several transmission ranks. So when the car starts moving the first, second, already engages with the second drive. After the set speed is instantly switching. Because the system does not have to choose one or the other of the shaft – the gears are already involved in the work.

Where applicable this transmission? Basically DSG is used in vehicles of class b, C and D. In many respects it all depends on the technical characteristics of the motor. So, the six-speed box is able to withstand a moment of 350 Nm. And semidiaphanous DSG – only 250. So this box is not installed on powerful cars.

CVT

This is a relatively new type automatic transmission, although the first instances were used in 59-m to year. So, the first car with variable transmission became "DAF". Further, this scheme began to practice such manufacturers as «Ford» and «Fiat". However widespread this box only got 10 years ago. Now this checkpoint applies to cars:

• «Mercedes».
• "Subaru".
• «Toyota».
• “Nissan”.
• “Audi”.
• «Ford».
• ‘Honda’.

A Key feature is that it has no transmission as such. CVT – the continuously variable transmission, which provides smooth change of gear ratios as the vehicle speed. The main advantage of this transmission – optimum matching of the load on the vehicle with the crankshaft revolutions. This achieves high fuel efficiency and performance. Also significantly improved smoothness, as jerking during dynamic acceleration is excluded.

The Machine picks up speed quickly, without jerks, smoothly. But due to certain limitations in the torque and power, variable automatic transmission is used only on passenger cars and some crossovers. Also significantly increases the cost of the machine at the CVT because the transmission is fairly high tech.

Device types

There are only two types of data transmissions. This toroid and V-belt CVT. The last is most prevalent. But regardless of type, they have the same device (automatic transmission «Toyota» is no exception). So, in the design included:

• Variable speed transmission.
• A Mechanism that ensures the transmission of torque.
• Control System.
• The Mechanism for the separation of transmission and for switching the reverse transfer.

To box can support and transmit torque, make use of the following mechanisms of friction:

• Automatic centrifugal. Applied to the variator “Transmatik”.
• Multi-disc wet. It variators “MULTIMATIC”.
• E - (the box “Hyper”, used on some Japanese cars).
• The torque Converter. As example of the transmission “Extroid”, “the MultiDrive” and “MULTIMATIC”.

The Last connection type is the most popular and resource. Note that the actuator variable transmission may be a belt or a chain.

The First type consists of one or two belt drives. Also in the device of the automatic transmission «Toyota» includes two pulleys. The last some form of conical discs that are able to slide and move between them. Thus changing the diameter of the pulley. For the convergence of cones, in the device of automatic transmission «Mazda» there is a special spring (sometimes activated by centrifugal force). The conical disk has a 20-degree angle. This ensures that movement of the drive belt with minimal resistance.

On the variator “Multitronik” used a metal chain. It is a few plates that are connected by axles. This design has a good flexibility. The bending radius is 25 mm. Unlike a belt CVT, a chain ensures the transmission of torque at the point of contact of the plates with the discs. In these areas there are highvoltage. Thanks to this scheme, there is a minimum loss in the transmission of torque and the best efficiency. Conical discs are made of high-strength bearing steel.

Because of design features and devices hydraulic unit of the automatic transmission is not able to provide reverse movement. Therefore, in the CVT for the reverse gear are used in auxiliary machinery. It is a planetary reducer. It has the same device and operation as in the classic hydrotransformer automatic transmission.

Also in the construction of this transmission has an electronic control system. It provides simultaneous adjustment of the diameter of the pulley of the variator, depending on the current engine speed. This system provides and the inclusion of reverse gear. Control of the variator is carried out through a selector that is in the cabin. Control modes – the same as on a conventional automatic transmission. The device and repair of these boxes is also similar. Note, however, that many services are afraid to receive these vehicles, simply because do not have relevant experience. A box appeared in Russia recently, and around it there are a lot of myths about the proper maintenance and repair. Experts say that this transmission just enough time to change the oil and not overheat the mechanism.

Conclusion

So we figured out what type is the automatic transmission, how it works and how it works. What to choose the ordinary motorist? Operating experience shows that the best option would be buying a car with classic hydrotransformer automatic transmission. This box is familiar to many – it can be repaired and serve in any service. Besides modern machines of this type are a good resource in the 300-400 thousand kilometers. As for the robot DSG and continuously variable, then these boxes are nursed not more than 150 thousand on our roads. Then the problems begin and a serious investment. Therefore, their purchase is to abstain.