How does the automobile transmission work?

Now there is a relatively new term-CVT, that is, continuously variable transmission, in domestic and imported cars. Transmission is a type of automatic transmission, but few people know about it because of its narrow application in the past. The English full name of CVT is CVT, and the transmission with its device is also called CVT or CVT. The biggest difference between this kind of transmission and ordinary automatic transmission is that it omits the complicated gear combination variable speed transmission and only uses two sets of pulleys for variable speed transmission. By changing the contact radius between the driving wheel and the driven wheel drive belt, the design concept is very mysterious. It was the Dutch who invented this variable speed transmission mechanism. At the beginning, the V-belt was used for the conveyor belt, which was of poor material and low transmission torque, and had no practical value. In 1979, engineers of Dutch DAF changed to metal belt to improve and develop practical CVT system. It has the advantages of less parts, small size, light weight, higher transmission efficiency and lower fuel consumption than ordinary automatic transmission. However, the disadvantage is also obvious, that is, the transmission belt is easy to be damaged and cannot bear a large load, but it has a great market in low-power cars. Fuji, Fiat, and Ford of Germany have successively introduced CVT, and improved it and used it in their own cars. 1984, Fuji Automobile Factory, which is best at applying new technologies, developed the electronic continuously variable transmission ECVT with computer device, and put it on the Justy(J 10) car in February of 1987. Take Fuji as an example, CVT is composed of four subsystems: electromagnetic clutch system, electro-hydraulic control system, direction conversion (forward/backward) system and stepless speed change system, and CVT system is the core part. The main components of the continuously variable transmission system are two pulleys and a steel belt, and the steel belt is sleeved on the two pulleys. The pulley is composed of two splayed wheel walls, and the groove between the two wheel walls forms a V-shape. A wheel wall is controlled by a hydraulic control mechanism, which can be separated and drawn closer according to different engine speeds, and the V-shaped groove also becomes wider or narrower, raising or lowering the steel belt, thus changing the contact diameter between the steel belt and the pulley. The two pulleys are reversely adjusted, that is, when the groove of one pulley is gradually widened, the groove of the other pulley is gradually narrowed. As shown in the working principle diagram of CVT, the groove width of the driving pulley can be larger than that of the driven pulley, and the circumferential radius of the steel belt of the driving pulley is smaller than that of the driven pulley, that is, the belt is small and the belt is large, which can transmit larger torque. When the car gradually turns to high speed, one wheel wall of the driving pulley moves inward, and the groove width becomes smaller, forcing the steel belt to rise to the highest top, while one wheel wall of the driven pulley is just the opposite, and moving outward makes the groove width wider, forcing the steel belt to fall, that is, the circumferential radius of the steel belt of the driving pulley is greater than that of the steel belt of the driven pulley, becoming a big belt and a small garden, thus ensuring the speed requirements of the car at high speed. Continuously variable transmission cars have their own gears, such as parking gear P, reverse gear R, neutral gear N, forward gear D and so on. However, there is no feeling of sudden jump when the car automatically shifts gears, which is very stable. Due to the development of material technology in recent years, the endurance of metal belt has been improved, which makes the application of CVT not only limited to low-power cars, but also in high-end cars. 1999 The Audi A6 2.4-liter sedan launched in the European market is the first to be equipped with a continuously variable transmission. According to the manufacturer, the maximum torque of Audi 2.4-liter V6 engine is 230 Newton meters, while the maximum torque output of CVT is 299 Newton meters, which is more than enough. At the same time, CVT has a wider transmission ratio, which is far more flexible than manual transmission and ordinary automatic transmission. The key technology is simple in structure, the transmission can be changed only by changing the circumferential radius of pulleys at both ends of the metal belt, and the transmission parameters can be changed at any time to meet the needs of different regional markets. Of course, CVT still has its application limitations, and the key is the carrying capacity of metal belt, so it can only be applied to light vehicles at present. Recently, CVT assemblies have been introduced into some domestic automobiles, such as Audi, Guangben Fit and Chery Yun Qi.