The continuously variable transmission is also referred to as CVT for short. It is the abbreviation of English 'ContinuouslyVariableTransmission'. It is literally a continuously variable transmission. As the name implies, it is a gearbox with no fixed transmission ratio. Compared with the traditional automatic transmission, it has more. Available power, better fuel economy and smooth driving experience. However, the early CVT gave the owners a 'rubber band' or 'slip' driving feel. After adding the analog shift, CVT's driving experience It's much better than before, but it's still not perfect. Let's follow the car uncle to learn more about the CVT gearbox.
How does CVT work?
The CVT uses two pulleys with variable drive diameters instead of gears. Each pulley is shaped like a pair of cones. The belt or chain moves between them. One pulley connects the engine, ie the power input, the other The pulley is connected to the drive shaft, that is, the power output. Through the movement of the pulley, the contact diameter of the cone and the steel strip can be changed to change the transmission ratio.
When driving at low speed, the diameter of the input end pulley is smaller and the rotation speed is higher. The diameter of the output end pulley is larger and the rotation speed is lower. As the speed of the car increases, the diameters of the two pulleys change to increase the output end. The speed of the pulley. This is the same as the traditional transmission method. It provides different power output for the car through matching of different sizes of gears. However, because the CVT is continuously variable, theoretically, the CVT has numerous 'tooth ratio combinations. ' .
CVT driving experience
Like the regular automatic transmission, the CVT has two pedals (brake and throttle) and a shifting position with P, R, N, D modes. When driving a CVT, it will not be heard or Feeling the gearbox shift, it will only increase the engine speed according to the need to get better acceleration performance, reduce the engine speed to get better fuel economy. Of course, also because the shift feel is not strong, step on the throttle Later, I heard the engine slamming, but I did not see a significant increase in speed.
CVT gearbox advantages
Since there is no fixed gear ratio, the CVT can continue to ensure that the engine speed is in the optimal power range. In addition to keeping the power at its best, it can also control the fuel consumption at an optimal level. The CVT gearbox has a simple structure, especially with Compared with the current 9-speed automatic transmission, the CVT has no gear combination. Only two pulleys and one steel belt can be combined to have different transmission ratios. Due to the simple internal structure, the CVT failure rate will be lower. And the weight will be lighter. Because the transmission ratio is dense, the car accelerates extremely smoothly.
CVT gearbox shortcomings
Due to the natural disadvantage of the CVT's shifting logic, there is no obvious feedback on the gear ratio change, which leads the driver to mistake the gearbox for failure. In the case of rapid acceleration, the 'rubber band' feels and the engine speed rises, but It is necessary to wait for the gear ratio to be replaced before the car accelerates significantly. In addition, most CVTs cannot handle high-torque power inputs, so CVTs are often used for economical compact models. Although CVT has lower daily maintenance and use costs, maintenance costs are low. But it is relatively high, mainly because of the high cost of parts for CVT.
Difference between E-CVT and CVT
Several hybrids, including the Toyota Prius, are capable of infinitely variable speeds. Although the name is E-CVT, their transmission configuration is different from that of CVT. It uses a planetary gear set, and both the gasoline engine and the motor can provide input. The speed of the motor and the speed of the engine can also be changed, so that the engine can run at a stable speed when the car is accelerating or completely stopped.
History of CVT
Da Vinci drew the first CVT sketch in 1490, and Dutch car manufacturer DAF applied CVT to their cars for the first time in the late 1950s, but technical limitations made CVT unsuitable for more than 100 horsepower. Engine. In the late 1980s and early 1990s, Subaru applied CVT to their Justy mini-car, and Honda applied CVT to the Civic HX in the late 1990s. CVT capable of adapting to more powerful engines It was developed at the end of the last century at the beginning of this century. Nowadays, CVT can be found in cars of Nissan, Audi, Honda, Mitsubishi and several other car companies.
Uncle Shu has something to say
In the years of technological development, the CVT gearbox has gradually become more entrenched. From the early engine that is not suitable for more than 100 horsepower, to the current Civic model of the main sports also used CVT. The view that keeping the CVT not enough movement seems to have no Great fit, although the performance of CVT will have a limit, but designers continue to increase this limit. For the future of CVT, Che Shu is still optimistic.
