60th anniversary of the serial automobile variator
In 1958, the DAF-600 was presented for the first time - the first production DAF car and the world's first serial continuously variable transmission DAF Variomatic. Enamelled car DAF 600, produced until 1963. In fact, manual transmission and automatic transmission are much more common and much more familiar to the public. In practice, the theorist is not a novice - the first patent for a variator was issued at the end of the 19th century, and the author of the first known variator in history is Leonardo da Vinci, who put forward his idea in 1490.
The variator, also known by the English abbreviation CVT - continuously variable transmission, has received widespread use in the last twenty decades, especially in Japanese cars. From a superficial point of view, a car with a CVT is no different from a car with an automatic - the same two pedals and a gear lever with the designations P, R, N, D. But economically its operation is different. And there is a continuous and smooth change in progressive numbers when accelerating or vehicle deceleration.
There are several types of variators - V-belt with rollers with variable diameter, chain, toroidal, but the first is the most common. Basically, the variator consists of two roller assemblies, each with two low cones facing each other with their ends. A V-belt runs between the cones, and the gear ratio changes smoothly as the cones converge or diverge.
There is also a system, usually hydraulic but possibly another servo type, that synchronously gathers the halves of the first swath and separates the halves of the second. Basically, it is connected to the drive shaft of the engine, and the second one is connected to the transmission to the wheel. Finally, a node is added to reverse the rotation of the output shaft to the wheels, such as a planetary gear, so there is a rear drive, so the final CVT box is ready.
The weak point in the design is the belt, an ordinary rubber belt with a textile base is possible - it will not overcome a thousand kilometers. The variator belt has a rather complex device - rather a metal strip with some kind of coating or a set of steel cables or strips, on which a large number of belt-shaped plates are strung, the ends of which are in contact with the surface of the cones.
To lubricate the variga, a special working fluid is used, which changes its phase state under strong pressure that occurs at the point of contact with the cones. In this way, the chain manages to transmit significant torque without slipping, regardless of the small contact area.
How exactly the variator changes the gear ratio during acceleration depends on the selected control program. In a manual transmission, we increase the rpm to a certain maximum, then shift to a higher gear, while in the CVT, the rpm remains at the same level, that is, at maximum torque, but the gear ratio changes gradually. Thus, the engine remains at high speed, accelerating all the time, the dynamics are high, there is no time for switching.
In some solutions, the CVT is adjusted so that the acceleration is similar to that of a manual transmission car, gradually increasing the engine speed. Some models even offer a mode with several "virtual" gears - 6 or 8, set by the car's electronics. With this decision, the variator abruptly jumps to the appropriate level, as in a classic machine. The driver can even shift gears manually in a similar robotic gearbox.
After all, the variator has a number of advantages, but there are also disadvantages. It is no coincidence that the first CVTs will debut for small cars. Crossover Nissan Murano (http://www.nissanbook.ru/en/Murano) with a 3.5-liter V6 engine and 234 hp. A V-belt variator is also used - X-Tronic.
Another disadvantage of CVTs is the relatively expensive maintenance and repair, as well as the need for a special and therefore expensive transmission fluid. Modern belts can easily withstand 150,000 km, and their oil is changed up to 50,000 km. The advantage of CVTs is that they are generally cheaper than good classic automatics.
Thanks to countless gear ratios, the engine can operate in the most economical operating modes - whether maximum power or minimum fuel consumption is required. Last but not least, the CVT makes it easy to integrate into the vehicle's energy recovery system.
