In the world of cars there are usually a very important decision What to take when purchasing: manual or automatic transmission? Traditionally, manual gearboxes were the most popular, but in recent years it is true that automatic transmissions have been gaining ground. Not to mention that the new electric vehicles directly lack this element. Although the equation would have to include CVT shiftwhich has often been unfairly classified as an automatic, since it has its peculiarities.
What is CVT shifting?
The acronym CVT comes from the term Continuously Variable Transmissionwhat we popularly know in our country as continuous variator change. In their definition they refer to it as an automatic transmission in the sense that the user does not have to engage in gear manually. However, it differs from other automatic transmissions because It does not have a preset number of gears. That means that there are no such jumps between relationships, its behavior is completely linear and continuous (hence its name).
Origin of CVT change
Although it may not seem like it, the CVT transmission has more a century old. The first use of it was not in a car, it was in a sawmill. The invention is attributed to Milton Reeves, who in 1879 used this variable speed transmission for his saws that had to cut wood. Although shortly after it began to use in other areas and in 1911 it was seen on motorcycles for the first time. It came from tricycles and it took many years for it to spread globally to cars.
The first production car to carry it was the DAF 600 in 1958. This vehicle from the Netherlands had the Variomatic transmission, which was a continuous variator with the same concept as the current ones. It didn’t work badly for them, since they continued using it until the 1980s and it jumped to the Volvos. That era that’s when it became popular, as Ford and Fiat created their own steel band CVTs to make them more robust. Many brands have joined in since then, as we will see later.
How does the CVT shift work?
As we said, the CVT has a very different operation from that of other automatic transmissions. In the absence of gears, it is proposed as a pulley system which have a variable diameter and are normally connected by a belt or chain. The key is that the pulleys have a cone shape that allows them to increase or decrease their diameter. This means that it offers almost infinite relationships and that can be adapted to the needs of each situation.
The diameter is controlled by a hydraulic circuit, allowing the relationship to change as if it were a game between the plates and sprockets of a traditional bicycle. Only here there is no pedaling, but the constant force of the motor pushing. By the way, in models with CVT at engage reverse gear What is done is to go around the circuit through an inverter, so that the movement is the same, but in the opposite direction.
Since a picture is worth a thousand words, we leave you a video that makes it much easier to understand:
CVT Exchange Rates
The truth is that the pulley transmission is the most popular and widespread CVT transmission, but there is more. Let’s do a brief review of others that have been used over time:
- Tapered CVT: the original and simplest, used cone-shaped rollers, with a wheel that moves on its slope to modify the diameter.
- toroidal CVT: The pulleys are changed to toroid-shaped discs and rollers. It holds more torque than pulleys and, as it has an input disc and an output disc, it does not need an inverter for reverse gear.
- Ratcheting CVT: In this case a series of clutches or ratchets are used to move. It is one of the oldest, dating back to 1930.
- Epicyclic CVT: which is also known as platenary gear, used by Toyota through its spherical roller axles that tilt.
- Hydrostatic CVT– Uses a variable displacement pump and a hydraulic motor. They are more complex, but also offer a notable level of refinement.
- electric CVT: It is the one that is powered through a power source, a generator, an electric motor and a battery pack.
Models with CVT changes
As the principle used by all CVT changes is very similar, the car behavior who assemble it is also similar. The sensation is of a linear increase in speed, without the staggering provided by the gears. When the maximum is demanded, the revolutions remain fixed at a specific point, so it is less natural and many people find it difficult to get used to it. They have been improving, but years ago they gave a certain slip ratio, like the speed does not increase as fast as the engine turns.
In any case, there are many models that have carried this type of change. Probably the most popular are those from Toyota, since the entire hybrid range has had the CVT for years. Now it has been electrified, but the C-HR, RAV4, Corolla or Yaris equip it. It is also present in Nissan, under the name Xtronic and in models such as the Qashqai or the X-Trail. On the other hand, brands such as Renault, Honda and Subaru also incorporate it in some models in their range.
Pros and cons of the CVT change
Depending on what the user is looking for, the CVT transmission could be their preferred option, so let’s talk about the pros and cons it has.
Advantages of CVT:
- Smoothness and absence of jerks, greater comfort while driving
- Very efficient, usually reducing consumption and emissions
- Durability, has fewer components and very few breakdowns
- Delivers torque and power in the optimal range
Disadvantages of CVT:
- Slower and less accurate response
- The noise when anchoring at high revs
- Does not support excessively high levels of engine torque
- Yes, they have specific maintenance
Future of CVT shifting
The electrification It has also arrived at the CVT change. As we have seen, many of the models that currently use it are hybrids, since it matches very well with this type of propulsion systems. This has forced manufacturers to make adaptations so that an electric motor is responsible for converting torque and speed, without the presence of the usual belts. That in turn makes it much more efficient and simpler than previous systems. Of course, it is powered by the vehicle’s battery and is controlled from the CPU.