This page has been robot translated, sorry for typos if any. Original content here.

How does the variator. A variator is a special type of automatic gearbox.

Leafing through car collections, almost everyone met the following phrase: “A continuously variable CVT is installed on the car”. Or they could see this phrase in the table of technical features. Everyone knows (not counting, perhaps, Americans) what is a manual transmission of transmissions; everyone has also become accustomed to the “automatic” (unusually amerikosy). But CVT (CVT, Multitronic, Autotronic)
A variator is one of the types of automatic transmissions. It differs in the absence of fixed steps and provides a smooth (stepless) change of the gear ratio as acceleration or deceleration. By design, the variators are of several types, but the most common (in practice, the only one on production models) is the V-belt variator. It changes the ratio when approaching and moving away from each other conical pulleys, between which the belt is clamped. The hydraulic drive moves these pulleys under control of electronics, from time to time having several modes switched by the driver (for example, the ordinary and sports). CVT animal little known. But he is not new.

You'd be surprised, but this invention does not belong to Honda or even to Mercedes. The patent for the variator was issued at the end of the XIX century! Moreover, the first CVT was invented and completely in 1490. His creator was a good bearded man Leonardo da Vinci.

The first able-bodied car with this type of box, however, did not arise in the era of the Restoration, but later - in 500 years, in the 1950s . The variator was installed serially on a DAF car (at that time, not only trucks, but also cars were produced under this brand name). Later, something similar began to be done on Volvo, but the variators received a really wide distribution only at the moment.

In fact, the variator (the more common English designation - CVT - continuously variable transmission) is, forgive me for the tautology, a variation on the theme of an automatic box. And the car, equipped with it, at first glance, does not give out itself - there are only two pedals and the gear box shift lever - P, R, N, D - is the same as the car with the traditional automatic transmission (automatic box, gearbox machine)
Automatically switches gears, providing greater convenience and convenience, also allowing the driver to pay more attention to the road. Automatic transmission protects the engine and chassis car from overload. A car with automatic transmission usually has a great fuel consumption and a bit worse dynamics. But on the final models of automatic transmissions that have several switchable control programs (economical, sporty, winter, etc.), and (or) manual gear selection mode - this defect is almost eliminated. From an ordinary mechanical box has a couple of major differences: switching occurs here without breaking the flow of power between the engine and wheels. And, almost always (depending on the model), the automatic transmission does not allow towing a typewriter using an ordinary method, but requests that the driving axle be hung on a tow truck. In the case of a long towing on the cable automatic transmission fails. Automatic transmission. Everything is ordinary. But the CVT works in a completely different way . It has no fixed first, 2nd, tenth gear. Try to imagine how many stars in our Universe, or how many grains of sand on all the beaches of the Earth taken together - in the transmission variator all the same much more. And the "switching" between them occurs smoothly and slightly.

That is why there are no jolts when starting off and “switching”. Regardless, we wrote this word in quotes: there are no switchings like this here. CVT constantly and smoothly changes the gear ratio
The gear ratio is the ratio of the number of teeth driven to the number of teeth of the driving gear. Traditionally mentioned in the description of transmissions and various options for their implementation. A higher gear ratio in a particular (first, 2nd, and so on) gear means great traction. They say that the transfer is "shorter" or "high-torque". The motor spins faster to the highest revs - the car accelerates better. But with all this, the highest speed in this gear is reduced, and it means that there is a need for the most early switch up. The smallest gear ratio means the longest gear. Also, from time to time they talk about “close together” gear ratios in the box or “close together”. Here it is assumed the near value of the gear ratios of adjacent steps. It is used on cars of a dynamic nature - because when moving up a notch the engine loses less revolutions, remaining in the zone of the highest torque. "> Gear ratio as the car accelerates or decelerates.

There are several types of variators: wedge-type pulleys of variable width, chain, toroidal ... The first type is the most common. Let's see how it works.

Klinoremeny variator MINI.

Variable speed drive

Here's a nice example: take two pencils (cylinders), lying parallel at a certain distance from each other. We bind them with a rubber band and start spinning one of them. Here the second one starts spinning too - at the same speed. But if the pencils are of a different diameter, a completely different story begins - until one of them, which is more, makes one turn, the second, say, two.

The variator is similar, only the diameter of the "pencils" it is continuously changing. It has two pulleys, each of which is made in the form of a pair of cones, facing at each other’s ends. And between the pulleys clamped V-belt.

Changing the radius of the rounding belt driving and driven pulley, you can smoothly change the gear ratio.

Variable speed drive

Now, if any of the pairs of cones can move to each other and back, we will get pulleys with a variable working diameter. After all, when the cones move apart, the belt in contact with them with its ribs will seem to fall to the center of the pulley and run around it along a small radius. And when the cones approach each other, the radius is great.

It remains only to supply the two pulleys with a system (usually it is hydraulics, but perhaps some other servo drive), which will exactly synchronously move the halves of the first pulley and push the halves of the second. And if one pulley is on the driving shaft (which comes from the motor), and the second one is on the driven shaft (which leads to the wheels), then it is possible to organize a change in the transfer case in very wide limits.

It remains to add a node that is responsible for changing the direction of rotation of the output shaft (for reversing), and this may be, say, an ordinary Planetary gear
The system of several gears, satellites spinning around the central, solar, gear. Traditionally, the planetary gears are fixed together with a carrier. The planetary transmission may also include additional outer ring gear (ring or epicycle), having internal gearing with the planetary gears.

The planetary gear can be used as a reducer when one of the parts is fixed, or to sum up two power flows. In this embodiment, all the elements are free. "> Planetary gear. And now the gearbox is ready.

By the way, an interesting question - what belt is used here? Obviously, an ordinary belt made of rubber and fabric, like those that turn generators and other suspended equipment, would not have lived a thousand kilometers. Belts in V-belt variators have a difficult device.

The belt in the variators, as you can see, is not a belt at all, but a type-setting iron tape.

з>

It can be an iron tape with some coating or a set of iron cables (tapes) of difficult section, on which a huge number of thin trapezoidal transverse iron plates are strung, the edges of which are in contact with the pulleys. By the way, it was specifically in this way that we managed to create a pushing belt, which transmits power not only by its half, which runs from the slave to the driving pulley, but also the opposite. The ordinary belt, when trying to transfer the compressive force, would simply have been folded, and the type-setting metal one - becomes rigid.

And as a V-belt can be a wide lamellar iron chain in contact with the cones with their edges. Specifically, such a "belt" works in the variators Audi cars.

That is the chain used in the variator company Audi ..

variable speed driveз>

It is interesting that a special fluid is used for lubrication of the chain, which changes its phase state under the powerful pressure that occurs at the point of contact with the pulley. Due to this, the chain can transmit a weighty force without actually slipping, despite the extremely tiny area of ​​contact.

How exactly the variator will change the gear ratio during acceleration depends on the selected control program. if during acceleration on an ordinary car, we spin the engine on each gear, then move to the next gear and so on, then with a set speed of a car with a variator the motor remains at the same speed (say, at the speeds suitable for the greatest torque), but smoothly changing gear ratio.

It creates a few weird feelings. We press the gas to the floor, the engine goes to great speed, and so it remains on them throughout the entire acceleration, howling like a vacuum cleaner. But the acceleration rate is the highest, well, time is not spent on switching between steps.

In general, in some variants, the variator is adjusted so that acceleration with it prompts more acceleration with an ordinary box, with a gradual increase in engine speed.

Obviously, when you try to drive into a hill and when you slow down a car, despite the accelerator pedal being depressed, a reasonable variator will not leave high gear in gear. The pulleys for a confident assault the heights will vividly move back - to increase the torque at the exit of the box.

And on some machines you can choose a mode with several “virtual” programs (with 6 or even 8), set by electronics. Gears, between which the variator will jump sharply, like a classic box "automatic". Even in this embodiment, you can switch the "transfer" on their own. As on the "machine" with manual sequential (alternate) mode.

Thus, the variator has a lot of advantages. But there are shortcomings. For example, a relatively small, by modern standards, "digestible" engine power. Regardless, such boxes began their march around the world on small-class cars. Well, at the moment strong cars - all very often are equipped with either “mechanics”, or classic “automata”, or mechanized boxes.

True, progress is underway. And here it is impossible not to recall the champions. For example, on the Audi A4 2.0 TFSI, the V-belt Multitronic variator (with a chain) cope with the flow of 200 “horses” without problems.

The belt in the variators, as you can see, is not a belt at all, but a type-setting iron tape.

variable speed driveз>

You can argue that class D is not everything. For executive and business class cars, and even more so for a large jeep - 200 forces can no longer be called such a great value. But the merits of the variators that are the most up-to-date are not limited to this. So, on the Nissan Murano crossover with a 3.5 -liter V6 with a capacity of 234 horsepower, put a V-belt X-Tronic . This is one of the largest and heaviest models equipped with a CVT. And what will happen tomorrow?

The second drawback of the variators is a comparatively precious service and repair, a special, and therefore, not cheap, transmission fluid. Belt variators can every 100-150 thousand kilometers require the replacement of the belt. Oil for all this is somewhat more expensive than for the “automaton”, but you can change it a bit less often - approximately in 40–50 thousand km for various models of cars.

Nevertheless, variable-speed drives are becoming more and more widespread on typewriters of various classes, moreover, they cost, traditionally, cheaper than the excellent “automata” of the classical type.

Since variable speed drives have an infinite number of gears, they allow the engine to operate in more favorable modes - do we need (at traffic lights) the most power, or, against, smoothness and less fuel consumption (with undisturbed driving). Therefore, models with variators distinguish, for others the same, the highest economy, combined with a more solid dynamics.

The belt in the variators, as you can see, is not a belt at all, but a type-setting iron tape.

variable speed drive

By the way, in the final time, there was a tendency to increase the number of transfers from the classic "automatic". In the final models, there are already more than 8 gears (on a car, we note, a car). And this is done specifically to combine the highest dynamics and economy. Quickly see machines with 10 steps or even with twelve? But the variators are already there where ordinary machines with their switchable planetary rows will never come. After all, the number of gears in the variator is limitless.