In fact, CVT is not a Japanese patent. It was first invented based on the concept of painter Leonardo da Vinci. As early as 1886, a V-shaped rubber belt CVT was used as a gearbox for gasoline models. In 1958, the Dutch company DAF successfully developed a double V-type rubber belt CVT and marketed it, with sales exceeding 1 million units. In early 1987, Japan's Subaru developed an electronically controlled CVT system and installed it on the Justy model. Also in the second half of 1987, Ford launched the Ford Fiesta in Europe based on the CVT transmission, while Italy's Fiat launched Uno based on CVT transmission. Audi has launched CVT models in its A4, A6 and other models.
As mentioned earlier, in 1987, Subaru developed electronically controlled CVT technology. In 1991, Subaru sold its first-generation electronically controlled CVT technology to Nissan. Later, Nissan-controlled Jetco Based on this technology, we developed our own CVT. Therefore, strictly speaking, Subaru is the originator of Japanese CVT technology. Relatively speaking, Honda and Toyota used CVT much later.
At present, the vast majority of CVT steel belts or chains in the world are produced by Bosch and Schaeffler. The steel belts produced by only Bosch have been assembled in more than 10 million cars. The reason why Most of them are because Honda produces its own steel belts.
In the early days, when electronic control technology was imperfect, CVTs did slip, especially the earliest belt-type CVTs. The friction between the cone pulley and the belt was too small, and it did slip when starting with high torque output. It is easy to slip. However, with the development of electronically controlled CVT, microcomputers are used to automatically control the pressing force of the hydraulic cylinder. At the same time, the engine's instantaneous high torque output is controlled by detecting the engine output speed and the instantaneous opening of the throttle. Therefore, in practice, The upper CVT really does not slip now. In fact, once the CVT shows signs of slipping, it will cause serious failure and even the steel belt will break.
At present, the installed capacity of CVTs in the world has already exceeded 15 million. If it is really like what some keyboard car gods said, poor quality, low life, slippage and breakage, if it is really like what these people imagine, It is so fragile and there has been overwhelming negative news for so long. However, in fact, judging from the current market feedback, CVT does not show a higher failure rate than AT or dual-clutch!
At present, the maximum torque that a chain-driven CVT can withstand is 450 Nm, while the maximum output torque of the current mainstream 2.0T turbocharged engine is about 370 Nm. Therefore, those who mention CVT Those who say the tolerable torque is too small should add more knowledge.
In fact, the acceleration ability of the CVT gearbox is not bad. In 2012, the 2.0T CVT version of the Forester launched by Subaru of Japan had an acceleration time of 6.8 seconds. The 2014 STI version of the Forester had the same acceleration time. Using CVT, the acceleration time from 0-100 is 5.6 seconds, while the Volkswagen Tiguan, which also uses 2.0T, accelerates in more than 8 seconds during the same period. Since CVT has no physical gears, its power is not interrupted during acceleration, except for the need to control the engine torque at the starting moment. Apart from the output, the rest of the time is in the acceleration period, so it is obviously more advantageous in the later stages.
Since CVT must control the engine torque output at the moment of starting and sudden acceleration, there will be a certain delay from the perspective of power response, which results in poor acceleration feeling for models using CVT gearboxes. , giving people a feeling of weak acceleration and slipping.
If you are driving in the northern winter and the outdoor temperature is lower than tens of degrees below zero, then the CVT will have certain low-temperature protection. This generally occurs when the water temperature is lower than 40°C, and the torque converter does not work at this time. Lock and limit upshifts.
At the moment of starting of the CVT gearbox, the hydraulic torque converter is not locked and uses gearbox oil to transmit power. However, before the hydraulic torque converter forms hydraulic coupling, the speed difference is relatively large. This is also relatively fuel-intensive. When driving at high speeds, when the vehicle speed exceeds 120km or more, the steel belt or steel chain that uses friction to transmit power requires greater compression force control to avoid slipping. At the same time, because it uses friction to transmit power, The transmission efficiency is relatively low, so the friction loss is also relatively large. Overall, the most fuel-efficient range of CVT is 10KM/h-110KM/H. When driving in this range, CVT has an advantage in fuel consumption, and this area is suitable for home use. However, if you repeatedly start, brake, start again and brake again, the fuel consumption of CVT will be higher than that of dual-clutch.
The speed range of general family cars is about 0-120km/h. However, due to traditional reasons, Europe has roads with no speed limits, and CVT has lost its biggest advantage of fuel saving when driving at high speeds. , coupled with the poor power response of CVT when driving at high speeds, from a market perspective, the use of CVT will not be recognized. For Japan, where the road is narrow and the speed is low, the advantages of CVT can be brought into play, which is The reason why Japan vigorously develops CVT.
It is said that the more AT gears there are, the more fuel-efficient it is, but it is too complicated and the failure rate is difficult to control. Although the dual-clutch transmits power directly and saves fuel, low-speed frustration is unavoidable. Although the CVT is smooth, it has poor acceleration. Therefore, when considering purchasing a car, you must clearly understand the purpose of the car and lock the transmission type according to the purpose of the car.
The reason why people say that CVT transmissions are bad is mainly because CVT transmissions left too many hidden dangers in the early days. They had a bad reputation at the beginning. Of course, everyone says that CVT transmissions are bad. Early CVT transmissions had extremely poor durability. The vehicle was prone to slippage when operating at higher torques. The CVT transmission was unable to accelerate, and the vehicle's responsiveness was also very low. These were all disadvantages of the CVT transmission.
But now, under the leadership of Japanese cars, CVT transmissions have undergone earth-shaking changes.
The first is the CVT transmission control technology. The CVT transmission now has a safety protection mode. If the main transmission slips or has other abnormal phenomena, the CVT transmission will immediately enter the protection mode. The transmission steel belt control oil pressure will increase, and at the same time it will Limit the engine torque and prevent the transmission steel belt from slipping.
The second is CVT transmission oil pressure control technology. With the continuous improvement of machinery manufacturing technology, CVT transmission oil pressure control has become increasingly precise. During the operation of the vehicle transmission, the transmission oil pressure is controlled very accurately and quickly. Therefore, the CVT transmission ratio and required oil pressure are better controlled. The responsiveness of the CVT transmission is also significantly improved, and the vehicle acceleration performance is enhanced. For the same vehicle, the acceleration from 100 kilometers to 100 kilometers with a CVT transmission is 7.5 to 11.5 higher than that of an AT.
Since the transmission ratio of the CVT transmission changes continuously within a certain range, the transmission ratio changes continuously when the vehicle is accelerating or driving normally. There is no shift shock when the vehicle speeds up, and there is no AT during rapid acceleration. The downshift phenomenon is eliminated, so the ride comfort of the CVT transmission is very good.
Since the transmission ratio of the CVT transmission continuously changes, the transmission can also achieve precise control of the vehicle's engine speed, and the engine speed directly determines the vehicle's fuel consumption. Therefore, the engine speed of vehicles equipped with a CVT transmission is easier to control. When driving at a lower speed, the vehicle's fuel consumption will naturally be lower. Now the fuel consumption of CVT transmission is more than 10% better than that of AT.
Today’s CVT transmissions are relatively reliable, otherwise Japanese cars would not be selling so well in China!
Introduction: Why do so many people say CVT is bad? It breaks easily, right?
Nowadays, CVT continuously variable transmission is one of the three mainstream transmissions in the world. It is often used in small-displacement cars, such as: Nissan, Subaru, Toyota, Honda, these small-displacement cars. The most used ones all have matching CVT versions.
The CVT gearbox is quite good, and it is not as bad as what is said online. Things like slippage and worn belts are actually found everywhere on the street with hundreds of thousands of kilometers on them. My cousin is a Nissan. It is matched with a CVT gearbox and has run almost 200,000 kilometers without any problems.
Therefore, the core components of CVT are the steel belt and the cone wheel. We mainly consider the service life from this point of view. The service life of the steel belt can already reach 300,000 kilometers. Since the steel belt is flexible, it is more susceptible to damage than the pulley. Therefore, the life of the CVT gearbox is generally measured according to the life of the steel belt, which means that if this thing is not broken, the others will generally not be broken.
High temperature will destroy the quality and friction characteristics of automatic transmission oil, increase friction and wear, and cause transmission noise. At the same time, sludge (impurities or dirt) will also be produced inside the transmission (such as valve body), causing the gearbox to buckle and impact. If the temperature exceeds 120°C, the rubber sealing material will begin to harden, eventually causing leakage and a decrease in hydraulic pressure. If the temperature is higher, the transmission begins to slip, which in turn causes the temperature to rise even higher.
Is the cvt gearbox really easy to slip? You can rest assured that modern CVTs are absolutely not allowed to slip. Once a cvt slips, it will be a serious failure. After the cvt slips, it will seriously wear the cone wheel and steel belt. A large amount of metal chips are produced to block the valve body, and the cvt cone wheel is a handicraft. So since the CVT gearbox is continuously variable, why does it still have a gear display? This is because automotive engineers take people's driving habits into consideration.
At the same time, it makes the car have a certain driving pleasure and makes it easier for the driver to grasp the dynamics of the car at any time. Several gears are artificially simulated in the CVT gearbox, and each gear corresponds to a certain range of Transmission ratio, for example, a transmission ratio in the range of 4.82~3.79 is first gear, a transmission ratio in the range of 3.78~2.96 is second gear, etc. Theoretically, a CVT transmission can simulate countless transmission ratios, but in order to conform to people's habits, six or seven gears are usually simulated.
Personal opinions, for reference only.
As early as 1886, a V-shaped rubber belt CVT was used as a gearbox for gasoline models. In 1958, the Dutch company DAF successfully developed a double V-type rubber belt CVT and marketed it, with sales exceeding 1 million units. In early 1987, Japan's Subaru developed an electronically controlled CVT system and installed it on the Justy model. Also in the second half of 1987, Ford launched the Ford Fiesta in Europe based on the CVT transmission, while Italy's Fiat launched Uno based on CVT transmission. Audi has launched CVT models in its A4, A6 and other models.