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How is the CVT. Variator - a special subspecies of automatic transmissions.
Leafing through the collections of cars, almost all met the following sentence: "The car is set stepless variator." Or could behold this phrase in the table of technical characteristics. What is a manual transmission gear, they know everything (except, perhaps, the Americans), the "machine" is also long been accustomed to all the (unusually amerikosy). But the CVT (CVT, Multitronic, Autotronic)
Variator - a type of automatic transmissions. Varies lack of fixed stages and provides a smooth (infinitely variable) change gear as acceleration or deceleration. According to the construction of several types of variable speed attend, but the most common (almost the only mass-produced models) is a V-belt CVT. It varies the gear ratio during the approach and the distance from each other cone pulleys, which is sandwiched between the belt. Moves are hydraulically driven pulleys running electronics, from time to time a driver has multiple selectable modes (for example, everyday and sports). CVT little known animal. But it is far from new.
You will be surprised, but the invention is not owned by Honda and does not even Mercedes. The patent was issued to the CVT in the late XIX century! Most of the first CVT was invented and completely in 1490. Its creator was a good bearded Leonardo da Vinci.
First able-bodied car with Siim type box, however, did not arise in the era of Reconstruction, and later - after 500 years in
In fact, the variator (the more common English designation - CVT - continuously variable transmission) - it is, pardon the tautology, a variation on the automatic transmission. And the car is equipped with them at first glance, does not extradite themselves - only two pedals and shifter box modes - P, R, N, D - such as cars and a traditional automatic transmission (automatic transmission, a box- automatic)
Automatic transfer switches, providing greater comfort and convenience, and fortify the driver to focus more on the way. Automatic transmission keeps the engine and chassis of the car from overload. Car with automatic transmission, usually varies a great fuel consumption and a bit worse dynamics. But in the final models, automatic transmission, with multiple selectable control programs (economy, sport, winter, etc), and (or) selection mode gears manually - this defect is virtually eliminated. From an ordinary manual transmission has a couple of major differences: change happen here without breaking the flow of power between the engine and wheels. And, almost always (depending on model), automatic transmission does not allow towing of cars everyday method, and posting requests on the axis of the superconducting evacuator. In the case of a long tow rope to the automatic transmission fails. Automatic transmission. All the usual. But the CVT works
Gear ratio - a ratio of the number of teeth led to the number of teeth of gears superconducting. Traditionally referred to in the description of transmission and different options for their implementation. A higher gear ratio in a specific (first, second and etc) transfer means great traction. Talk that the transfer of "shorter" or "high-torque". The motor spins up to prytche largest turnover - a better car accelerates. But with all this reduces the maximum speed on a given transmission, and means there is a need in the most raneshnom switching "up". The lowest gear ratio means the most "long" transmission. Also, from time to time talking about the "contiguous" transfer numbers in the box, or "closing number." Here is assumed the near value of ratios of adjacent stages. It is used in the dynamic nature of the carts - because in the transition to step up the engine loses less speed, remaining in the zone of highest torque. "> Gear ratio as the acceleration or deceleration car.
Variators visit of several types: V-belt pulleys with variable diameter, chain, toroidal ... first type - the most common. Let's see how it works.
V-belt CVT MINI.
Here is a nice example: take two pencils (cylinder) lying parallel to a certain distance from each other. Contractible elastic band, and they are starting to turn some of them. It also begins to spin and the second - the same rate. But if the pencils are of different diameter, begins an entirely different story - as long as any of them, what more would make one revolution, second, say, two.
CVT is designed similar, only the width of a "pencil" it is constantly changing. He has two pulleys, each of which is made in the form of a pair of cones, facing Edged meet each other. And sandwiched between the V-belt pulleys.
By varying the radius of rounding of the superconducting and the belt pulley, it is possible to change the gear ratio plavnenko.
Now if any of the pairs of cones can move to each other and back again, we get the pulley of the variable diameter. After all, with the belt razdvizhenii cones in contact with them by their edges, would seem to fall through the center of the pulley and obegat it in a small radius. But the approach of the cones - on the great radius.
It remains only to provide the two pulley system (usually hydraulic, but perhaps also
It remains to add a node that is responsible for changing the direction of rotation of output shaft (for reverse), and this could be, say, an ordinary planetary gear
The system of multiple gears, satellites, revolving around a central, sunny, gears. Traditionally, planetary gears are fixed together with the carrier. Planetary gear may also include additional outer ring gear (crown or epicycle) which has an inner mesh with the planetary gears.
Planetary gear may be used as a gear, when one of the parts attached, or to sum the 2-power flows. In this embodiment, all items are free. "> Planetary gear. And ready-CVT gearbox.
By the way, entertaining voprosets - which is used belt? Obviously, the usual belt of rubber and fabric, such as those that twirl generators and other hanging hardware, there would not have lived, and a thousand miles. V-belt variator belts have a hard device.
Variator belt, as seen, no not the belt, and composing steel tape.
This may band with some iron-coated iron or a set of wires (ribbons) are difficult to cross, on which are strung the vast number of thin transverse plates of iron trapezoidal, and the edges are in contact with the pulleys. By the way, particularly those properly managed to push a belt transmitting power not only the half of it, which runs from the superconducting to the slave pulley, and the opposite. Everyday belt while trying to pass a compressive force would be formed simply and inlaid metal - becomes stiff.
And as a V-belt can be a wide slat iron chain in contact with the cones of its edges. Specifically, such "belt" running in the variator cars Audi.
That is such a chain is used in the variator company Audi ..
Interestingly, for the lubrication of the chain used a special fluid that changes its phase state under strong pressure arising at the contact with the pulley. With this circuit can transmit weighty effort, without actually slipping in spite of an extremely tiny area of contact.
How exactly will change the variator ratio during acceleration, depends on the management program. if the acceleration on the ordinary square we untwist each transfer engine, and then move on to the subsequent transfer and etc, then set the speed variator car with the motor remains at the same speed (say, a speed suitable to the greatest torque), but plavnenko changing the gear ratio.
This creates some weird feelings. Hit the gas to the floor, the engine goes to great speed, and so it remains in their dispersal throughout, howling like a vacuum cleaner. But the rate of acceleration - the highest, well, and switching between the stages is not wasted time.
In general, in some embodiments variator set up so that the acceleration from the acceleration prompted him more than with an ordinary box, with a gradual increase in motor speed.
Obviously, when you try to call on the mound and at slowing cars, regardless of accelerator pedal depression, intelligent CVT will not leave 'on' top gear. Pulleys for certain assault vyshiny move back alive - to increment the torque output of the box.
And on some typewriters it is possible to select multiple "virtual" gears (with 6 or even 8) controlled by electronics. Transfers, between which the CVT will jump sharply, though the classic box of "automatic". Even in this embodiment, it is possible to switch to "pass" on their own. As to the "machine" with a manual sequential (alternate) mode.
Such a way, the variator weight advantages. But there are drawbacks. For example, a comparable small by modern standards, "digest" the power of the motor. Regardless of such boxes began their march across the world on machines of small class. Well, at this point a strong car - all very often staffed or "mechanics" or the classic "guns", or motorized boxes.
However, progress is going. And here we can not remember the champions. For example, the Audi A4 2.0 TFSI V-belt CVT Multitronic (with chain) without zamorochek cope with a flow of 200 "horses".
Variator belt, as seen, no not the belt, and composing steel tape.
It is possible to argue that the Class D - that's not all. For executive cars and business class, and even more so for a large SUV - 200 forces more closely so you will not name any great quantity. But the merits of going to the most up to date on the variator does not end there. Thus, the Nissan Murano crossover with 3,
Second drawback variator - comparable valuable service and repair, special, and the means cheap, transmission fluid. Variable speed belt can tysch every
And yet, variable speed are becoming more and more common on machines a variety of classes to the same and they are traditionally less expensive excellent "machines" of classical type.
Since the variable-speed drives have an unlimited number of transfers, they permit me to run the engine on more favorable regimes - essential for us (at traffic light races), the maximum power, or against, smoother and less fuel consumption (with a serene ride). Therefore, models with variator distinguish, in other similar, the highest efficiency, combined with a more solid dynamics.
Variator belt, as seen, no not the belt, and composing steel tape.
By the way, the final time, there is a tendency to an increase in the number of transmissions from the classical "machines." In the final model more closely meets 8 speeds (in cars, notice the car). And this is done specifically for the combination of superior dynamics and efficiency. Quickly see a machine with 10 steps, or even twelve? But variable-speed drives are more closely in places where ordinary machines switched their planetary series will never come. Indeed, the number of transfers from the variator is unlimited.
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