CVT transmission: principle of operation, owner reviews on the pros and cons of the variator

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

When buying a car (especially a new one), many motorists face the question of choosing a gearbox. And if everything is more or less clear with engines (diesel or gasoline), then the choice of transmissions is simply huge. These are mechanics, automatic, tiptronic and robot. Each of them works in its own way and has its own design features. It should be noted that the CVT is in second place in distribution after the automatic transmission. Such a transmission is often found on both Asian and European cars. In today's article, we will look at what the owner's reviews of the CVT gearbox are, how it works, what are its features and pitfalls.

It is worth noting that the CVT appeared on the Russian market relatively recently. And if many people know about the machine, then the minuses and pluses of the CVT box are far from known to everyone. But do not be so afraid of the variator. It's a pretty advanced transmission.reviews say.

Characteristic

So what does CVT mean? This is one of the types of automotive transmissions, the task of which is to smoothly transfer torque from the flywheel to the drive mechanisms (and, as a result, to the wheels) of the car. There is no gear change as such. Therefore, a CVT is also known as a continuously variable transmission. This gearbox provides a change in the gear ratio in the range specified by the computer. The amount of torque depends on how hard you press the accelerator pedal.

Thanks to a special design, such a box is able to use the power of the internal combustion engine as efficiently as possible due to the optimal coordination of the load on the car with the crankshaft speed. Thus, high fuel efficiency is achieved. Also among the features worth noting is a smooth change in torque. That is, the car picks up speed without any shocks and jerks. This has a positive effect on the smoothness of the ride.

But it's worth noting that CVTs have power limits. In view of this, such a box is used only on cars and crossovers. A vivid example of this is the Nissan X-Trail CVT gearbox. Vans and heavy duty vehicles do not use this transmission.

Types

Today there are several types of CVT:

• With V-belt (sometimes V-chain) transmission.
• Toroid type.

90 percent on carsCVT of the first category is applied. The device and principle of operation of both types of gearboxes will be considered below. By the way, the first V-belt CVT appeared on a Daf passenger car in the late 50s. Then they began to put a similar box on Ford and Fiat. Now CVT is in the list of boxes from every global manufacturer:

• "Mercedes-Benz".
• Toyota.
• "Audi".
• "Subaru".
• "Honda".
• "Opel".
• "Mitsubishi".
• Chrysler.
• "Rain".

As for toroid CVTs, they are used on Nissans. According to reviews, this checkpoint is quite expensive to maintain.

Device

The CVT design includes the following components:

• Mechanism that ensures the transmission of torque and separation of the gearbox from the internal combustion engine.
• Variable transmission.
• Electronic control system.
• Mechanism that ensures the movement of the car in reverse.

All these components are enclosed in a single metal case. This gearbox is installed in the same way as a conventional gearbox - behind the engine flywheel. To transfer torque and disconnect the transmission, one of three types of clutch can be used in the design:

• Automatic centrifugal clutch.
• Torque converter.
• Electronically controlled wet multi-plate clutch.

The most popular type today is the torque converter. This mechanism provides a smooth transmission of torque. In addition, CVTs with GTF are distinguished by a high resource compared to other CVTs - reviews say.

Belt drive

This is the main element that makes the variator work. The V-belt type CVT may consist of one or two belts. A special pulley interacts with them. It forms two conical disks. These discs can expand and retract automatically. This ensures that the pulley diameter is corrected. To reduce the distance between them, spring force, hydraulic pressure and centrifugal force are used. As a rule, the angle of inclination of the discs is 20 degrees. This ensures that the belt runs with the least resistance across the pulley surface.

It is worth noting that the first variators with such a transmission had a low resource of 50 thousand kilometers. They also had little flexibility (minimum radius - 90 millimeters) and insufficient control range. Now in modern CVTs, a metal flexible belt is used, which is made of ten strips of steel, which are interconnected by shaped parts in the shape of butterflies. The torque is transmitted due to the frictional force that occurs between the side surface of the belt and the pulley. This design is highly durable and flexible. The minimum bending radius is 30 millimeters. However, these boxes are notmake noise, as noted by the reviews.

CVT V-Chain

Audi and Subaru variant boxes use a metal chain. It is she who is the main drive element and performs the function of a belt. The chain is several plates that are interconnected by axes. They have a bending radius of 25 mm. In this design, the torque is transmitted by point contact with the conical disks of the end face of the chain. By the way, the discs themselves are very durable and are made of bearing steel. As practice shows, the V-chain variator provides the highest efficiency with the least losses.

Reverse gear

Due to design features, this box cannot provide a reverse stroke. And it doesn't matter which drive is used - a belt or a chain. Therefore, in order for such a car to have a reverse gear, a planetary gearbox is used in the design. It works on the principle of a gearbox in an automatic transmission.

The CVT control system also includes a selector lever. It is located in the cabin, and it is with it that the driver selects the desired transmission modes.

CVT operation principle

As we said earlier, the torque is transmitted using a chain or belt transmission. How does a CVT transmission work? The principle of operation of the CVT transmission is to change the diameter of the discs depending on the engine load. At the beginning of the movement, the drive pulley has the smallest diameter. In this case, the disks are decompressed bymaximum. The driven pulley has the largest diameter. With an increase in speed and speed, the electronics will change the position of the pulleys relative to each other. So, the diameter of the driven disk decreases, and the leading disk increases. This allows you to reduce the gear ratio. Thus, the car picks up a lot of speed. During acceleration, the variator maintains the optimal number of revolutions of the internal combustion engine (in the region of three thousand). This is necessary for efficient acceleration without sacrificing fuel economy.

About the Nissan box

These cars, as noted above, use a toroid variable transmission. How is it organized? Such a box includes two shafts with a spherical surface. Special rollers are clamped between the latter. The principle of operation of such a box is very simple. It consists in changing the position of the rollers relative to each other in the toroidal surface. The transmission of torque is carried out due to the forces of friction between the rollers and the working surface of the wheels.

Is it advisable to use a CVT? The pros and cons are listed below.

Benefits

The main advantage of the CVT-box in the dynamics of acceleration. After all, the electronics itself selects the optimal torque and gear ratio. A car with a CVT has good speed characteristics. Also, among the advantages of a CVT gearbox, reviews note low fuel consumption. It is at the level of mechanics, despite the fact that the whole system works like an automaton. Another advantage noted by the reviews is the smoothness of the ride. Because inthere are no gears, jerks and shocks are completely excluded during acceleration. Another plus is high efficiency. It is 10 percent more than a classic automatic transmission.

Problems and pitfalls

Among the problems that arise during the operation of this box, reviews note high maintenance requirements. Every 60 thousand kilometers it is necessary to change the oil in this transmission. Moreover, use only the original, since a low-quality analogue can affect the life of the mechanisms. Over the years, the hydraulic block clogs in the box. In view of this, the pump cannot create normal oil pressure in the system. As a result - slipping of the shafts. The latter cannot normally open / clamp the belt or chain drive. And when slipping, the drive element heats up significantly and wears out. With a high load, the belt may even break at all - reviews say. As a result, an expensive box repair will be required. Shaft mirrors can also bulge. This also negatively affects the operation of the drive element. Another disadvantage is the presence of many electronic systems. In the event of the release of any block, you need to fully diagnose the transmission. It is quite difficult to find an intelligent master who breaks in a variator (so far these boxes are not common in Russia). You have to go to the dealer and pay incredible amounts.

Well, the most significant drawback is the transmission resource. If a conventional automatic transmission runs 300 (and the old 4-speed models even more) kilometers without problems, then the variator takes care of twotimes less. And this is subject to the timely replacement of oils.

Which is better: automatic or CVT?

Here's what the experts have to say about it. If the car is new and under warranty, you can safely take it with a variable gearbox. Usually the warranty ends at 100-150 thousand. That is, in the event of unplanned malfunctions, you can always fix the problem for free. But if you're buying a used car, you should look into automatic transmissions.

As a rule, cars are sold on the "secondary" already with pretty "tired" variators and it is simply unprofitable to take them. The automatic transmission has a long resource, and if repair is necessary, it can always be carried out in any workshop. The cost of work will definitely be lower compared to the variator, and several times lower.

Conclusion

So, we looked at the pros and cons of a CVT gearbox, as well as how it works. CVT transmission is more technologically advanced than automatic transmission. However, the introduction of new technologies has significantly affected the cost of maintaining the box and its resource. Therefore, it does not always make sense to take a car with such a transmission. In the event of a breakdown, you will have to spend at least one hundred thousand rubles to restore it. Even the most dead machine gun can be brought back to life for a maximum of 60-70 thousand. And then it will serve at least another 200-300 thousand kilometers, the owners say.