Every motorist, when choosing a new or used car, almost immediately pays attention to the type of gearbox. If everything is very clear with the “mechanics”, then not everyone knows the difference between a variator and a classic “automatic”.
In this article we will try to answer very important questions: "What is a variator?" and “Why is it better (or worse) than the classic automatic box gear ”. So let's go!
In fact, it is very difficult to distinguish an automatic transmission from a CVT if you do not have the opportunity to drive a car. The gear lever looks exactly like a conventional "automatic" - there are traditional positions P, N, D and, of course, M (in some models, this mode allows you to force the desired gear).
But as soon as you get behind the wheel and ride, the difference becomes noticeable almost immediately. "Automatic" gets under way from a place with a slight jolt, and during a gear change, a step change is clearly felt. With the variator, the opposite is true. The speed on this type of box is recruited smoothly (the sensations are similar to an electric car), without failures, and the engine speed is always in the same range.
To fully understand how these transmissions work, it is necessary to delve deeper into the technical side of their operation.
Classic "automatic"
In an ordinary automatic transmission, the following required structural elements are present:
- A torque converter used as a clutch.
- Reducer, thanks to the gears of which the gear ratio changes.
- A special "brake" band that blocks the required gears, fixing the desired gear.
- A control unit that monitors the operation of all nodes.
As you can see, the design is not the simplest, but nevertheless, it has been worked out and proven over the years. The advantages of the classic "automatic machine" (except for high reliability) include a positive effect on the durability of the motor. The gears are switched within the limits set by the manufacturer, which allows the engine not to spin up to the maximum speed, and this has a positive effect on the resource.
Given the fact that boxes of this type were developed many years ago, they also have a number of significant disadvantages:
- Low dynamics and low gear change speed (an average automatic transmission changes gear in 0.25 seconds, when the 5th gear is reached, about 1 second will be lost);
- Fuel consumption. The use of a classic automatic transmission leads to significant fuel consumption due to the significant load on the engine;
- Huge amount of transmission fluid and weight. For trouble-free operation of the automatic transmission, it is necessary to periodically change the transmission oil. Its amount is on average 7-8 liters, which is 1.5-2 times more than in the engine paired with which the box works. Oil is not cheap, and a complete replacement of all the oil poured into the system is almost impossible (for complete replacement it is necessary to make two times, the so-called partial replacement oil or completely remove the automatic transmission from the car).
Variable speed drive
From a technical point of view, the device of the variator is much simpler. A variator is an ordinary intermediate link that transfers traction from the engine to the wheels. Initially, transmissions of this type were used in mopeds and scooters (early CVTs could not "digest" high power, this problem is partly relevant today).
In a design of this type, the transmission is (in a simplified version) two rotating cones that are directed towards each other. A special belt connects them together (this part constantly moves along the cones, which smoothly changes the torque ratio).
Among the main advantages of the variator are the following:
- A high degree of speed gain (no time wasted on gear shifting, constant connection between the motor and wheels).
- Smooth running (no jerks when changing the next gear).
- Less fuel consumption (achieved thanks to a simplified design).
But the disadvantages of this type of transmission are also quite a few:
- The CVT cannot be installed on vehicles equipped with a powerful engine (over 200 HP).
- The oil used in the variator is very expensive and, as a rule, specific (in the event of a leak, it is very difficult to determine which oil is filled, therefore, it should be replaced only at a branded service station).
- Expensive repairs and service, which at this stage is almost impossible to produce outside of an authorized dealer (also the variator design provides for a belt replacement every 100-150 thousand kilometers).
- Inability to move quickly.
Which type of box is right for you?
Each motorist must find the answer to this question on his own. The right decision can only be made after a short test drive and understanding which type of gearbox is right for you.
It is important to understand that the variator is not suitable for drivers who aggressively drive a car; for them, an automatic transmission (we will talk about mechanics or DSG in a separate material) with the ability to manually shift gears (Tip-tronic) would be a more suitable option for them. On the other hand, the CVT forgives many mistakes for inexperienced drivers and makes life easier for them on slippery surfaces in winter. This type of transmission will not allow a sharp increase in power, which means there will be less chances to allow the drive wheels to slip.
Another nuance of the variator will overtake the driver on a suburban highway while overtaking. For the desired effect and the timely completion of the maneuver, the driver must press the gas pedal 0.5-1 second before starting to enter the oncoming lane.
Most modern cars when driving in a measured city, the engine speed in the case of using a variator transmission does not exceed 1500-1700 rpm. This means reduced fuel consumption and better acoustic comfort.
And the last thing. Do not place great hopes on the "manual" mode of the variator (that is, with the ability to manually switch the "virtual" gear). As practice shows, manual gear shifting only leads to a decrease in dynamics and an increase in fuel consumption.
I hope this material helped you decide on the choice of transmission for your future car!
- , 29 Sep 2015
Which is better - a variator or "automatic"? This question is often asked by people planning to buy a new car with one or another transmission. There is a huge amount of conflicting information on the Internet, in which it is very easy to get confused. We offer you comparative features, advantages and disadvantages in the device and service, information about which is collected from the reviews. real owners machines with these two transmissions, as well as information on the design and operation of both the variator and the automatic transmission.
CVT design and operation
Before we move on to the comparative characteristics of the variator and automatic transmission, it will be useful for you to know the device and principle of operation of the first and second units. This information will help you draw the right conclusions at the end of the story. So let's start with the variator.
The main difference between a CVT (Continuosly Variable Transmission, CVT) from any transmission (both automatic and manual) is lack of fixed gears... Each such unit has a certain range in which the transmission force (number) is located under certain conditions at a particular moment in time. This becomes possible due to the fact that the operation of the variator is based on a different operating principle than that of the gearbox.
How does the variator work? Its principle of operation is to use a belt drive (most often in modern cars a metal belt or chain is used), which transfers forces between the drive shaft (from the engine) and the driven shaft (going further to the wheels). In this case, the gear ratio changes smoothly due to the smooth change in the diameter of both the driving and driven shafts. For this, special techniques are used. Every modern car manufacturer has its own experience in this area. However, all CVTs can be divided into two main types:
CVT operation
- V-belt;
- toroidal.
The basis V-belt transmission is a trapezoidal toothed belt (some automakers use a chain or belt made of metal plates). The second component is two pulleys, which are formed by tapered discs. They can change their diameter, due to which it is possible to change the speed and value of the transmitted torque.
The work takes place according to the following algorithm. When the driver presses the accelerator pedal, the drive pulley transfers rotation from the engine to the driven shaft. However, its design is created in such a way that under the action of centrifugal forces, due to the increase in revolutions, the cheeks of the discs are compressed and pushed out drive belt from the center of the pulley to its edge. And on the driven shaft, the opposite process takes place. That is, his cheeks are unclenched and the belt moves to the center of the pulley. So the gear ratio and forces change smoothly. When the accelerator pedal is released, the reverse process occurs.
The scheme of the toroidal variator
Toroidal variator has a different principle of operation. Instead of shafts, it has two wheels with a spherical surface. Rollers are clamped between. One of the wheels is driving, the second is driven. Changing the value of the transmitted torque and gear ratio arises due to a change in the frictional force between wheels and rollers. Changing the position of the rollers in the transverse plane allows you to change the gear ratio. When the roller is horizontal, the drive and driven wheels rotate at the same angular speed. When the rollers change their position, the gear ratio also changes.
However, due to the complexity of design solutions and manufacturing technologies for individual parts, toroidal variators are rarely used. Therefore, in the future we will talk about V-belt devices as the most popular in the automotive industry.
CVT oils are different from others. They have a corresponding designation - CVT. The fact is that these oils not only lubricate, but also prevent slippage... It is thanks to this property that the operation of the belt for the transmission of torque between the shafts becomes possible. In this regard, "oil starvation" should not be allowed. Otherwise, the belt or chain will begin to slip along the working surfaces of the shafts, thereby significantly wearing them out.
Automatic gearbox operation
The main elements of an automatic transmission are a torque converter and a mechanical gearbox. In this case, the torque converter acts as an automatic clutch, and the gearbox transmits mechanical force between the gears. The torque from the engine shaft is transmitted by a torque converter, which operates based on the available oil pressure. Also, the design of the automatic transmission includes steel discs with clutches, as well as clutches. They perform the mechanical function of the clutch, that is, when they are compressed and released, the necessary clutches are activated, which in this case play the role of gears in the box.
Automatic transmission has its advantages and disadvantages, which we will talk about below. They will allow us to see how the variator differs from the automatic machine and what is better in certain conditions.
CVT operation
Automatic gearbox operation
CVT advantages and disadvantages
For clarity, the pros and cons of the variator are presented in the form of a table.
| Advantages | disadvantages |
| Smoothness of movement. The vehicle accelerates without jerking, which is typical for a gearbox. The movement is reminiscent of driving an electric car (such as a Tesla) or an electric lift. | The variator cannot be installed on cars with powerful engines (from 220 hp and above). This is due to the fact that powerful engines exert significant force on the drive belt or variator pulley. |
| High efficiency. Thanks to it, the time for transferring useful power from the engine to the transmission is significantly reduced. Because of this, the car becomes more dynamic when accelerating. This is especially felt at speeds from 50-60 km / h and above. | High price transmission oil... In addition, the variator is very demanding on its quality. Therefore, as a rule, it is necessary to buy only original oil, which is much more expensive than budget counterparts. |
| Significant fuel savings. It becomes possible thanks to the smooth acceleration and braking and higher efficiency than the automatic transmission. | The presence of a large number of electronics and sensors increases the likelihood of breakdown electronic system variator control. As a result, as a result of even a minor breakdown of the electronics, the variator can be converted to emergency mode or simply disabled. |
| A machine with a variator is more environmentally friendly due to lower fuel consumption (less CO2 emissions). | The complexity of the repair. Often, when a malfunction occurs, a problem arises with the search for car services that repair variators (this is especially true for small towns). In addition, the cost of repairs will be higher than that of an automatic transmission. |
| Gentle mode of operation. The choice of operating conditions is largely carried out by electronics, which selects the optimal operating modes in order to reduce wear of parts and extend their service life. | On a machine with a variator, you must not tow a trailer or other vehicles, as well as tow the car itself with the engine off. |
Remember that a trailer or other vehicle must not be towed on a machine with a CVT. Also, you cannot tow the car itself with the engine turned off. An exception is when the drive axle is suspended.
Now, to complete the picture, let's move on to describing the advantages and disadvantages of an automatic transmission. This will give us the opportunity to make a choice, which is better - an automatic transmission or a variator.
Advantages and disadvantages of automatic transmission
We will also give information about them in the form of a table.
| Advantages | disadvantages |
| High unit reliability. Modern automatic transmissions are designed for operation with a range of several hundred thousand kilometers (more than 300 thousand kilometers are guaranteed, usually more with proper care). In this case, any operating conditions are possible. The same applies to automatic clutch, whose functions are performed by the automatic transmission. | Low efficiency caused by significant losses in the torque converter. Therefore, not all of the useful engine power is used, |
| Relative ease of repair. Unlike a variator, repairing an automatic transmission does not present any particular problems. Most of the service stations are engaged in this. In addition, the cost of repairing automatic transmissions is much lower. | High fuel consumption. This is a consequence of the previous point. Cars with automatic transmission use more fuel than cars with a CVT. |
| The automatic transmission is not so demanding on the quality of the transmission oil. It is not necessary (although desirable) to use the original oil, it is quite possible to get by with a cheaper analogue. | Worst dynamic characteristics... In particular, the acceleration of a car with an automatic transmission is slower than that of an analogue with a variator or with a manual transmission. |
| Sparing attitude to the engine. Gear shifting occurs without the need to set high engine speed. | Car jerking when automatically shifting gears (although modern multistep gearboxes are less susceptible to this disadvantage, since they have more gears). |
| A larger amount of used transmission oil (8-10 liters versus 5-8 for the variator and 2-3 for the "mechanics"). |
In short, the automatic transmission is today a more reliable system, especially when the mileage is over 100 thousand kilometers. The only condition, as in any automotive unit, is timely and sufficient care.
More information about automatic transmission
Here are a few more interesting facts, which will surely help the future car owner, and he will be able to decide which gearbox is better - an automatic or a variator.
Acceleration schedule of a car with a variator and automatic transmission
- Transmission volume more oil in the automatic transmission(although not significantly, it depends on the specific model). But this often does not affect the cost, since the price of the original CVT fluid is usually higher.
- Changing the oil and filters on the variator should be done more often.... And during operation, make sure that it does not turn black and does not lose its characteristics, since its quality is critically important for the unit.
- Usually, automakers recommend changing the oil in the variator every 60 thousand kilometers. However, according to the reviews of many car owners of cars with a variator, it is better to do this earlier, about 50 thousand... Moreover, it is necessary to replace not only the oil itself, but also the filters, since they are inexpensive.
- You cannot start abruptly on the variator.... The whole essence of its work comes down to optimizing speed and torque so that the mechanism works in a sparing mode. Therefore, if you like to "drive", then this version of the transmission is clearly not suitable for you. Also on the variator do not skid and pull trailers or other vehicles.
- Long driving at both the highest and the lowest speed is equally harmful for the variator.... The fact is that under these two conditions, the belt experiences significant mechanical stress, from which it wears out. In addition, the oil temperature rises. Additional cooling should be considered. Therefore, if you often stand or move slowly in city traffic jams, then think again about the advisability of buying a car with a CVT transmission.
- During operation cars with a variator in severe frost, be sure to warm up the engine in order to reduce the viscosity of transmission and other oils. Otherwise, the variator belt will slip, additionally wearing out its surface and the surfaces of the pulleys.
- It is undesirable to buy a car with a variator for secondary market ... There is a high probability that problems will arise with this particular node in the first place. Checking the condition of the belt is quite simple. To do this, you need to drive a car along a flat road at a low speed for a distance of about 1 kilometer. If during the ride you feel jerks, you will definitely have to refuse to buy such a car.
- Monitor the status of the speed sensor... If it fails, the electronics puts the variator into emergency mode. If this happens on the move, then "engine braking" is performed, which can be harmful to the car.
- Timely change of CVT oil is extremely important... The fact is that if the oil loses its operational properties, then the variator valve body will gradually clog, respectively, the oil pump will not be able to pump the normal operating pressure... As a result, the shafts will not be able to compress and unclench the belt, it will begin to slip on them and wear out a lot. In the worst case, it will tear and "tear" all the insides of the variator.
- Changing the drive belt must be done every 120 ... 150 thousand kilometers regardless of his condition.
To summarize ...
Despite all the shortcomings, today variators are the most perfect type of transmission... Their advantages have been appreciated by tens of thousands of drivers around the world. As for the aforementioned shortcomings, automakers are constantly working on improving the design of variators, so we can say with confidence that they will gradually replace the automatic and mechanical transmission from the market.
Finally, we will provide information in order to give a better understanding of who is more suitable for buying a car with a CVT transmission:
- the variator does not like aggressive driving style;
- it is not recommended to drive a CVT transmission for a long time at extremely low or high speeds;
- when operating the variator at very high or low temperatures, it is necessary to create special conditions;
- a car with a variator must not be towed with the engine off (it can be towed when suspended drive axle), and it is also prohibited to use it to tow other vehicles or trailers;
- it is advisable to drive only on flat roads, since the variator drive belt is afraid of significant shock loads;
- timely change the oil and drive belt.
Thus, before buying a car with a variator, you need to prepare yourself for the conditions of its future operation. Especially if you have previously used exclusively manual transmission... However, over time, you will get used to it and will probably be happy with the choice. Just do not forget to service the CVT transmission in time and follow the rules for operating the car described above.
Conclusion
Considering all the above information, we can say that there is no definite answer to the question of which is better - a variator or “automatic”. After all, these two units are very different from each other, and each has its own characteristics. Therefore, the choice must be made based on operating conditions of the machine... In addition, remember that at present on the domestic car market there are variators that are far from perfect ("raw"). Automakers are constantly working on their development, and there are all the prerequisites that in the future they will take their place in the market.
An automatic transmission can be represented by a classic automatic and a variator. When purchasing a car, a car enthusiast thinks about which gearbox to give preference to; which is better: a variator or an automatic transmission. When choosing between a variator and an automatic machine, you need to know how they differ, take into account their pros and cons, and also understand which of the devices is more reliable.
CVT transmission
Like any other gearbox, a variator is a device that converts torque from the engine to the wheels. The transmission of torque is carried out steplessly within a certain control range. Quite often, the variator is designated by the abbreviation "CVT" (Continuously Variable Transmission), which translated from English means "transmission with continuously changing torque."
CVT types
Depending on the device, the following main types of variators are distinguished:
- chain;
- V-belt;
- toroidal.
The most widespread is the V-belt.
The V-belt CVT consists of a V-belt located between two sliding pulleys. In the process of movement of the car, the pulleys are compressed, then unclenched, providing a change in the gear ratio. The main purpose of the CVT is to provide a smooth, stepless torque change. This is true for cars, scooters, snowmobiles and other equipment.
Toroidal variator In a CVT, power is transmitted by the beveled ends of the chain link pins, and pulling force is transmitted by the chain.
In toroidal variators, instead of pulleys, tapered disks are used, instead of a belt, rollers. They are capable of transmitting more torque. For the manufacture of parts for of this type CVT requires high strength steel, which ultimately affects its cost.
Advantages and disadvantages of CVT
Chain variator The main advantage of a CVT transmission is the ability to provide a continuous change in torque. This allows for better fuel consumption and vehicle dynamics.
The disadvantages of the variator include:
- The inability to install it in cars with a powerful engine.
- Maximum loads, towing or systematic driving on high revs will lead to rapid wear of the variator belt, and, accordingly, to the breakdown of the CVT.
Automatic transmission
Hydromechanical automatic transmission The automatic transmission is controlled by a shift selector located on the central tunnel or on the steering column (in American cars). Moving the selector to a certain position allows you to select the desired driving mode. Additionally, it is possible to choose special ones: winter, sports, economical. The difference in fuel consumption between normal, sport and economy modes is clear.
Consists of planetary gearbox, steering system and torque converter. The machine can be used in cars and trucks as well as buses.
Consists of pump and turbine wheels with a reactor located between them. The pump wheel is connected to the engine crankshaft, the turbine wheel is connected to the gearbox shaft. The reactor, depending on the operating mode, rotates freely or is blocked with.
The transmission to the gearbox takes place by a fluid (oil) flow ejected by the impeller blades onto the turbine blades. The gaps between the impeller and the turbine are minimal, and their blades have a specific shape that forms a continuous circle of oil circulation. Thus, there is no rigid connection between the engine and the transmission, which contributes to the smooth transmission of tractive effort.
It converts the rotational speed and the transmitted torque in a limited range, therefore, a multistage planetary gearbox is attached to it. It also provides reverse movement.
Gear shifting takes place under oil pressure using. The pressure between the clutches, in accordance with the gearbox operation algorithm, is distributed using a system of solenoid valves (solenoids) under the control of the control unit.
The disadvantages of an automatic transmission are its high cost, as well as increased fuel consumption.
Comparative characteristics of two types of gearboxes
Which device is better: a variator or an automatic machine? Let's make a comparative characteristic that allows you to identify the differences and determine which of the boxes is better and more reliable.
The difference between a variator and an automatic machine from an economic point of view
Which gearbox is better in terms of operating cost: CVT or automatic? Let's compare some indicators.
- Transmission fluid. CVT oil changes are more frequent and more expensive.
- Fuel consumption. Fuel in a car equipped with a variator is more economical.
- Repair. Maintenance and repairing the variator is much more expensive than operating the machine. CVT is a rather complex and sensitive mechanism.
Although it is more expensive to maintain a CVT, the box itself is cheaper than a machine. And with proper use of the box, it can last a long time and without repair.
Which device is better in terms of reliability
In order to determine the degree of reliability of devices, we set a number of difficult conditions:
- the possibility of towing;
- off-road;
- high speeds;
- sports riding.
The variator cannot cope with the harsh conditions. His belt will not withstand the stress. A machine gun will do better here. CVT release - smooth movement without harsh acceleration.
How to determine which device is installed in the car
- It is necessary to study the technical documentation of the machine. The designation of the variator is CVT, the automatic machine is AT.
- Take a test drive. If a variator is installed, then you will not feel the gear changes. The machine can be “listened to” and monitored by the tachometer. CVT works in one key, measured. However, there may be a special mode that simulates gear changes and allows the driver to feel them shifting.
Summarize
Today, automatic transmissions are much more common than CVTs. But the latter has great potential. Automatic transmission is safer to use in vehicles with high power and towable trailers. From the point of view of economy, the variator looks preferable.
CVT or automatic? The choice is yours. And it will depend on the characteristics of the devices that are your priority. Love the smooth city ride on a small passenger car? Your choice is CVT. If you prefer sport riding or you often use a trailer - then an automatic machine is better for you.
Should I choose a manual transmission or an automatic one? And if automatic, then an ordinary machine, "robot", or a variator? Such questions are very popular among motorists when choosing a new or a used car. The Internet is filled with gearboxes, and how useful information, and information "rubbish". Only a professional in the subject can distinguish useful from rubbish. Such is his, the Internet, a defect. Therefore, I decided to write a few lines about all these mechanics, automatic machines, robots and variators, moreover, without plunging into "nuts", so that any reader, regardless of the level of technical literacy, could understand what is at stake, and that he, PERSONALLY , will be better.
Manual Transmission
Let's start with the "mechanics". In the case of a manual transmission, under the hood we have an engine, a "black box" of a transmission, with all its shafts, gears, synchronizers and engaging couplings. And between the engine and the box is the clutch assembly. The clutch pedal was pressed - the engine and gearbox were completely separated. As long as you keep the clutch pedal depressed, the power unit and gearbox are unconnected and you can shift into any gear based on driving conditions. This is the main advantage of the "mechanics", especially for the "advanced" driver, who knows and is able to apply the techniques of active driving. For example, in the case of a front-wheel drive car, "push" the engine against the wheels of the front axle before the maneuver. And in case rear-wheel drive, "Screw" the car into a bend, go to a steeper trajectory. But, as often happens, the disadvantages are an extension of the merits. Actively "drive", of course, it is pleasant, but wielding the clutch pedal and the shift lever in the endless traffic jams of megacities is not the most pleasant experience. This is the minus.
Hydromechanical automatic transmission, or "conventional automatic"
In order not to control the gearbox "hand-to-hand", and not to strain too much with the handles-legs in the dense city traffic, an automatic transmission was invented. First, a hydromechanical automatic transmission (automatic transmission) appeared. In order to understand how it works, you need ... a fan (ordinary, household) and some kind of children's spinner-toy with a propeller-propeller similar to a fan. Turn on the fan and bring this toy to it. What's going to happen? The propeller on the toy will spin too! Now imagine that the propeller does not drive the fan motor, but the car engine. And the second screw is located on the shaft, which goes into the "black box" with gears, couplings, and everything else. Both of these screws are housed in a sealed housing filled with a special transmission fluid called a torque converter.
What are these passions for? And in order to move smoothly, shift gears as smoothly as possible without any clutch "from the driver's foot", as in the "mechanics" between the engine and the "black box" with gears. After all, in order to get under way, you need to smoothly connect the motor and the "black box" of the box. Here is the torque converter, without losing any effort from the engine, it does it. And the liquid is needed in order to transmit rotational movement through it. And then the air, it will not cope. The density of the air is low for the transfer of energy at these rotational speeds. As for the gear changes, they are performed at the command of the control unit, automatically, depending on the driving conditions. Previously, these units were hydraulic, now they are electronic.
In general, everything in the hydromechanical automatic transmission seems to be good. It goes by itself, it switches itself. The driver can only press the accelerator and brake pedals, and click the automatic selector between “Parking”, “Drive” and “Back”. Moreover, this thing works quite reliably. If you do not pretend to be Schumacher on the automatic transmission, and follow the Maintenance Regulations, then it does not break.
But there are drawbacks. Chief among them are tangible moments automatic switching ranges of automatic transmission in a "black box" with gears, and higher fuel consumption, in comparison with the "mechanics" with the same power units. Need in more comfort, rising fuel prices and environmental concerns have encouraged engineers to think about automation again.
"Variable speed drive". CVT automatic transmission
To understand what the engineers have thought of, imagine ... a bicycle. Pedals, two sprockets, with a chain between them. On rear wheel slightly more advanced models have a few sprockets so that you can change gears. I switched it to a big sprocket - pedaling is easier and you can go up a steep hill, only you have to pedal more often. At the same time, the speed of the bike drops, but this is a price for high traction. And if you ride on flat terrain, or from a mountain, then I turned on a smaller sprocket at the back - you pedal less often, and the speed of the bike increases. Now imagine that the bike has a belt instead of a chain drive. That is, instead of a chain - a belt, instead of sprockets - pulleys, only instead of a bunch of sprockets on the rear wheel - ONE pulley, but its diameter can ... smoothly change.
Have you presented? Here, in front of you, a CVT automatic transmission! One pulley is of constant size, the second is variable and its diameter changes at the command of the control unit, adjusting to the driving conditions. And between them - the strongest "belt", which is either a multi-link chain, or a composite, of metal plates. A smooth change in the diameter of one of these pulleys leads to the fact that the switching moments of the automatic transmission are not felt at all. After all, they simply do not exist, these switching moments. J Amazingly comfortable piece of work, this variator! But it was not without flaws, significant and smaller.
"Variators" are not cheap. They also strongly dislike slipping. Due to the fact that between the "black box" with pulleys and the belt you have to put the same torque converter (you need to get under way!), And also because of mechanical friction in the "black box", energy losses are quite large, fuel consumption, in comparison with the "conventional" automatic transmission, a little less. And maybe more. And you also have to "conjure" the engine programs so that it does not hum like a trolleybus at constant speed during acceleration. After all, there is no stepped gear change. Therefore, the space for research again opened up for engineers.
"Robots". Robotic transmissions
To overcome the shortcomings of hydromechanical and variable speed automatic transmissions, several design schools turned their attention to ... a conventional mechanical gearbox. But what if we replace the foot clutch actuator with an electric actuator, the gear lever and traction lever to the "black box" with gears with electric actuators, and control the clutch and shifting using an electronic unit, based on driving conditions? Of course, only a fairy tale tells itself easily and quickly. The engineers had to tinker a lot with the control programs for this unit and the reliability of the electric drive, but automated manual transmissions, which journalists dubbed "robotic" or "robots", went into mass production for small cars. They represent precisely the classic "mechanics" in which the clutch and gear changes are controlled by an electronic unit.
The main advantage of the majority of "robots" is their high fuel efficiency, for which they, first of all, were created. After all, a computer with a perfect control program never makes mistakes, never gets angry, does not get depressed and never gets tired, unlike drivers with different experience, skill and resistance to physical and mental stress. Therefore, a car with a "robot" consumes less fuel than the same car with any other gearbox, including "mechanics". And such a "robot" is cheaper than any other automatic transmission in the purchase, when ordering a new car. Like this.
But here it is not without drawbacks. No matter how hard the engineers tried to optimize the moments of switching, the "pecking" of the car with its nose during violent acceleration is very noticeable. Such "robots" are for economical and quiet driving, and not for "Schumacher". They also hate clutch slippage. The engineers had to tighten up again.
"Robots" classDSGfrom Volkswagen
Imagine a car with a six-speed mechanical box gear. Have you presented? Only this box is not quite ordinary. More precisely, it is not at all usual. It seems to consist of TWO units, with the 1st, 3rd and 5th gears connected to the engine through one clutch module, and the 2nd, 4th and 6th through the other. It turns out something like "two in one". Now imagine that all controls are fully automatic, electronic and electrical. Moreover, when you accelerate, for example, in 2nd gear, the control unit has ALREADY turned on the 3rd, and is only waiting for the best moment to make an instant "click-click" by independent clutches in order to "release" the second gear and "cut in" a previously prepared 3rd. Switching to such an automatic gearbox takes not just a split second, but milliseconds! The driver and passengers simply do not notice these changes, and acceleration is smooth and very fast. For example, in DSG, which was the first in the world to be put on the conveyor by VOLKSWAGEN, the switching times take 7 milliseconds. It's much faster than blinking your eyes. Therefore, there are no jerks and jerks, as in the "robots" described above.
The DSG 7 SPEED WARRANTY has been extended to 5 years or 150,000 km:
Concern VOLKSWAGEN AG, meeting the wishes of customers, in order to maintain customer confidence in the cars of the concern, at the expense of the manufacturer, carries out free repair or replacement of box assemblies DSG transmission 7 DQ 200 for a period of up to 5 years or until reaching 150,000 km of run from the moment the car is handed over to the first buyer. When the owner of the car contacts official dealers with a claim for the operation of DSG 7 DQ 200, diagnostics and, if necessary, free repairs will be carried out in accordance with the current technical recommendations of the concern.
In the same way, such "robotic" boxes switch not only "up", but also down. The gearbox control unit carefully "observes" the driver's actions using sensors on the pedals and steering gear, and prepares in advance best gear for driver purposes.
If I say that such "robots" of the VW DSG class work brilliantly, then this would not be an exaggeration, and not only in terms of gear changes. Their control units also do not "get tired" or "make mistakes", so the fuel consumption of a car with DSG, especially in the urban cycle, is less than with any other gearbox, including the "mechanics".
As for the shortcomings, there are few of them, but, alas, they are: High cost and unacceptability of slippage in clutch units (however, what kind of clutch does it like?).
These are the options.
Sincerely,
Denis Kozlov (DOK)
Your expert in vehicle selection and maintenance
To improve the convenience of driving, automakers began to install automatic transmissions instead of classical mechanics. Such a checkpoint allows the driver not to be distracted from the traffic situation by changing gears.
Hydromechanical and continuously variable transmissions are the most popular of automatic transmissions... There is a competitive struggle between them, and the question, a variator or an automatic machine - which is better, is still relevant for them. Both automatic and CVT transmissions have their own advantages and disadvantages, so neither type of transmission can completely supplant a competitor.
The device of the variator gearbox and the principle of its operation
The principle of operation of the variator gearbox is based on a smooth change in the gear ratio depending on external conditions. The device of the variator of the V-belt design involves a change in the diameter of the pulleys. Structurally, this is realized by the convergence and divergence of two cones mounted on the shaft. The main factors that determine the diameter of the pulley at the point of contact are load and speed.
A variator with a V-belt design includes several main parts:
- Clutch system. In the first continuously variable transmissions for connection to power unit used a torque converter similar to that used in the automatic transmission. Subsequently, automakers began experimenting with centrifugal and electromagnetic clutches to improve transmission efficiency.
- Shafts with fitted cones of variable diameter. They work under high load, therefore they are made of high-strength steel.
Rice. - "V-belt transmission"
- Belt or chain. Serves to transfer force between the pulleys. It is made of metal strips connected with special fittings.
- Transmission fluid. Automotive manufacturers do not recommend using conventional oil for automatic transmissions. For cars with a variator, special lubricants are produced (for example, DiaQueen CVT, used for Mitsubishi).
Rice. - " Original oil in CVT "
- Hydroblock. Serves to direct the oil supply to the required channel. Grease is pumped by an oil pump.
- Filters. As a rule, there are several of them: coarse and fine oil cleaning, as well as a pair of magnets that catch small metal crumbs. Filters can be installed both inside the variator and outside its housing.
Rice. - "Filters for fine oil purification"
- Radiator. The variator box works with more heat than the automatic one. Therefore, to prevent thermal degradation of the oil and its additives, cooling with a radiator is required.
- Electronic control unit. The algorithms for choosing the optimal gear ratio and sending commands to control the variator are assigned to the electronics of the continuously variable transmission. It maintains constant communication with the main ECU module, processes information from the sensors. The variator control unit can be located both in the case of the variator itself, and outside it.
Types of variators
According to their design, the following types of variators are distinguished:
- V-belt, which is the most widespread;
- chain, which is analogous to the above type, but with a chain instead of a belt;
Rice. - "Chain variator"
- toroidal, which, due to a complex device, occupies no more than 5-7% of the continuously variable transmission market.
The main difference between the toroidal continuously variable transmission is the absence of a V-belt or chain transmission. The torque in such a variator is transmitted using special rollers and tapered discs. Changing the position of the rollers leads to a change in the gear ratio.
The advantage that a toroidal CVT transmission has is more torque than a V-belt design can handle. This is possible only when using steel of the highest strength and wear resistance, which affects the price of the unit, increasing it.
What is the difference between a variator and an automatic transmission?
The main thing that distinguishes the variator from the classic automatic transmission is the absence of jerks when picking up speed. This is due to the fact that the CVT transmits torque during acceleration without stages, which are characteristic of the machine.
The differences between the variator and the automatic transmission are due to the fact that the hydromechanical transmission takes time to switch a pair of working gears. Because of this, the dynamic performance of the speed gain turns out to be worse. The absence of a break in the kinematic connection during acceleration of a car with a CVT allows the continuously variable transmission to carry out faster acceleration.
The engine, if the machine with a variator, works in a more gentle mode. This is due to the smooth maintenance of revolutions crankshaft, since the acceleration of the car occurs mainly due to the change in the gear ratio of the transmission. As a result, drivers who have changed from automatic machines and mechanics, at first, have a poor sense of the speed of the car.
Pros and cons of the variator box
The advantages that cars with CVTs have include the following:
- low fuel consumption - continuously variable transmission has a higher efficiency;
- smooth ride, not accompanied by jerks that occur in the automatic transmission when changing the gear ratio;
- gentle engine operation.
Despite all the advantages of the variator, its design is not without its drawbacks. Because of this, the continuously variable transmission never took a leading position in the auto industry. The disadvantages of the variator are as follows:
- complex repairs, which are not undertaken in many car services;
- limited resource of the belt, the cost of which is quite high;
- sophisticated electronics and high sensitivity to control unit errors;
- high oil cost.
The pros and cons of the CVT allow them to remain in demand in a narrow circle of motorists. As a general rule, driving with a CVT is rarely dynamic. The variator does not like abrupt starts from traffic lights and slippage.
Pros and cons of an automatic transmission
An automatic transmission has the following advantages over a continuously variable transmission:
- high reliability;
- lower repair cost compared to a variator;
- ease of repair.
The disadvantages of automatic transmission are as follows:
- gear shifting leads to jerks;
- speed gains slower;
- The efficiency is lower, which leads to increased consumption fuel.
It is impossible to say unequivocally which of the transmissions is better. It all depends on the preferences of a particular motorist. If smoothness and optimal fuel consumption are more important for the driver, then the choice should be made in favor of the variator. If the key criteria are durability and higher maintainability of the transmission, then it is necessary to choose an automatic transmission.
