Automatic changes: types, how they work and characteristics

Automatic transmission: Types and operations

The cars with automatic transmission They have more and more presence in the European market, and we have talked about them on many occasions. This time we are going to focus on the technique and in the function. Next, we are going to explain the different types that we can find in the market today, how do they work and of course their characteristics and advantages. You will learn more about gearboxes and it will be easier for you to choose your next automatic car.

In today's market we find four types of automatic transmissions. Okay, really only two are automatic changes: automatic by torque converter and continuous variator. The other two are considered changes manual with automated functions: robotic and double clutch gearbox. Anyway, we all commonly refer to them as automatics because they don't have a clutch pedal. We start with the latter.

robotic change

Robotic gear lever

The robotized manual gearbox is the simplest “two-pedal” transmission on the market. Basically we are facing a traditional manual gearbox to which the clutch management and gear change functions have been automated. In many cases it is called robotic manual transmission.

Through the electronics, many parameters are received, such as throttle position, speed or revolutions. With this data, the ECU determines if the clutch should be fully engaged or not, as well as if it should up a gear, reduce or maintain the one that is already engaged.

In the event of needing to change gear, a series of actuators are responsible for disengaging the clutch, removing the engaged gear, engaging the new ratio and engaging again. As I said before, it is the same operation that we do in a manual boxl of all life, but in this case it has those automated functions. The driver is limited to accelerating and braking.

Today there are few new cars that use a robotized manual gearbox. They are transmissions very economic because they are easy to develop and simple to manufacture, but they are very slow, usually abrupt and, to tell the truth, they are not always as intelligent and effective as we would like.

Its use is basically limited to small utilities where speed of change or comfort is not as important as in a higher-end car. Years ago it was mounted on somewhat larger vehicles. Of current models that are offered with this automatic transmission we can mention the Hyundai i10 AT, the Toyota Aygo x-shift or Fiat 500 Dualogic.

double clutch transmission

S tronic dual clutch gear lever

The change of double clutch It began to gain a lot of popularity around the year 2005 approximately and from the hand of the Volkswagen Group. It would be made known in the German giant under the trade name DSG, later called S tronic at Audi. Keep in mind that, likewise, it is not an automatic gearbox per se, but rather a double automated manual transmission. But not a manual box itself. You will soon understand.

In the traditional manual gearboxes and in the robotic gearbox seen above, we have a clutch and two gear shafts (a primary shaft and a secondary shaft). In this type of transmission we have two clutches and two pairs of gear shafts (two primary and two secondary). Hence its name is double clutch.

One of the pairs of gears is in charge of the even gears, while the other manages the odd. Logically, we have one clutch for even ratios and one for odd ratios. This makes the jumps between gears much faster.

If the electronics detect that it is close to the gear change from 3rd to 4th gear, for example, before the odd-numbered clutch disengages, the pair of even-numbered gears is already engaged (but without engaging the clutch, although it is prepared). A few moments after the odd clutch is released, the even clutch is already engaged. As we say, the change is very, very fast.

The main drawbacks of this type of transmission is that its price is much higher. In a compact model we are talking about around 2.000 euros more compared to a manual gearbox when buying a new mid-range car, so if it has to be replaced, the operation will also be expensive. And regarding maintenance, as a general rule it is replaced the oil (valvulin) at approximately 60.000 kilometers, although it depends on whether the clutches are wet (bathed in oil) or dry.

Automatic gearbox interior
Related article:
Change the gearbox oil: when, which one to use and symptoms of its lack

The double clutch transmission used in models of all kinds, from B-segment utility vehicles to supercars. We can find a Renault Clio EDC, an Audi R8 V10 S tronic or a Mercedes B-Class 7G-DCT, just to name a few examples; although the truth is that there are many current models available with double clutch.

Continuous Variator Automatic Shift (CVT)

Continuous Variator CVT Gear Lever

We jump to the continuously variable transmission, which is already a full-fledged automatic change. It is also known by its acronym CVT. This transmission is widely used by Asian manufacturers and it is already quite popular in our country. Virtually all Lexus or Toyota models use it, as well as Honda or Subaru automatics.

In this case it has nothing to do with the two types described above or with a manual gearbox. Here we meet a transmission with infinite ratios. Its operation is based on the use of two tapered pulleys that can vary their diameter -by means of oil pressures ordered by the electronics- and a belt that connects them. One of the pulleys is practically connected to the output of the crankshaft and the other sends the movement to the transmissions.

The operating principle is that of a scooter or a Vespino, to give an example; although much more effective and conveniently adapted.

Depending on the operation of the vehicle and the demands made by the driver, electronic management will vary in one way or another the diameter of the pulleys. In order to always maintain the same distance and avoid tension changes in the belt, when one pulley increases its effective diameter, the opposite decreases it. In this way the transmission ratios are completely varied.

Reverse gear is achieved by an epicyclic system.

The positive part of this type of transmission is that they have a very smooth operation at all times and that allow us to control very well the movement of the vehicle when maneuvering at very low speed; parking, for example. However, on the open road, when accelerating fully They tend to rev the engine too high. and there's a slippery feel that drivers don't usually like.

Another point to take into account is that they are transmissions with a great reliability and durability. In fact, they have a very good reputation in various markets outside of Europe, where they have historically caught on very well. In Europe not so much because of that slippage that we mentioned.

Automatic torque converter shift

Torque converter shift lever

Finally, we have the automatic transmission by torque converter. In recent years, the designer brands of these transmissions have achieved a great result, with a very smooth operation but also very quickly when it comes to jumping between the preset ratios. In some cases they work even better than some double clutches, although the losses are higher.

Its operation is somewhat more complex to explain, but surely with a short video its basic operating principle is much better understood. The first thing to keep in mind is that at the output of the crankshaft, attached to the flywheel, we find a casing inside which there are two internal turbines and blades in opposite directions to each other. This group is the torque converter itself.

Between both turbines there is transmission oil, which is responsible for transmitting movement from one to the other.

The turbine attached to the crankshaft is known as hydraulic pump. It rotates with the crankshaft, sending oil pressure to the second turbine and turning it. This second turbine is connected to the transmission output. When the driver accelerates more, logically the engine revs up. When revving up, the first turbine sends more oil pressure to the second, thus increasing the speed at the output of the torque converter towards the second part of this gearbox.

Actually the torque converter, with its turbines and oil pressure, acts as the clutch in a manual transmission.

After the torque converter (and some other parts) we find a system of epicyclic train with various shafts and satellite and planetary gears capable of creating various transmission ratios. Each transmission ratio (each gear) is achieved by blocking one or the other axes, an operation that is ordered by the mechatronics through electronics and hydraulic pressure.

To top it off, there are many car brands and models that opt ​​for this type of transmission. To name a few, most BMWs offer the 8-speed Steptronic, Audi in its higher-torque mechanics offers the Tiptronic, Mercedes also has the 8 and 9 G-Tronic. Also Volvo or Alfa Romeo. In more general brands we find Opel, Peugeot or Ford.

How do automatic cars drive?

If you are thinking of buying an automatic car and you have discovered that there are many types, you do not have to worry or be overwhelmed. All automatic cars drive exactly the same.. There will be smoother cars and others more abrupt. Some will be faster and some will be slower.

The levers for the transmission management may be different and there will also be variations in the response of the car, but the driving mode is the same.

As you know, in any car with automatic transmission we must completely forget about using the left foot, using the right one both to accelerate and to brake. Depending on the model, we may have a mode sequential operation to control the transmission ratio, an operation that can be carried out from the steering wheel itself if our vehicle has paddles for change.

On some other occasion we have already talked about whether it is manual or automatic transmission better, of the reasons why drivers purists They are not very much in favor of automatic transmissions or what are the advantages that automatic transmissions offer. automatic boxes in high-performance cars.
Subaru XV automatic transmission
Related article:
How to drive a car with automatic transmission

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      Fernando said

    Thanks for the article friends, it's always good to learn something we didn't know about transmissions... entertaining and with current and interesting information. On our website about automatic transmission we have been creating content of interest for the Motor World for some time, we are a group of friends who carry out our humble website dealing in detail with the entire universe of automatic gearboxes and transmissions.
    Cheers! and good luck?