CVT (continuous variable transmission), which is directly translated as continuous variable transmission, as the name suggests, is that there is no specific gear, and the operation is similar to that of automatic transmission, but the change of speed ratio is different from the skip process of automatic transmission, but continuous, so the power transmission is continuous and smooth. CVT, whose scientific name is continuously variable transmission, has a history of more than 100 years.
Chinese name CVT transmission foreign name continuous variable transmission
The difference between continuously variable transmission (CVT) and stepped transmission is that its transmission ratio is not an intermittent point, but a series of continuous values, for example, it can change from 3.455 to 0.85. CVT has simpler structure and smaller volume than traditional transmission. It has neither many gear pairs of manual transmission nor complex planetary gear sets of automatic transmission. It mainly realizes the stepless change of speed ratio by driving, driven wheels and metal.
The principle is that, like an ordinary gearbox, several groups of gears of different sizes are opened and closed under the control to form different speed ratios. For example, the pedal of a bicycle drives the wheels to rotate at different speeds through large and small wheel discs and chains. Due to the different thrust generated by different forces on each group of gears, the output speed of the gearbox also changes, so as to realize the slow rotation regardless of grade.
CVT adopts the transmission belt and ratchet with variable groove width for power transmission, that is, when the ratchet changes the groove width elbow, change the contact radius between the driving wheel and the driven wheel to change the speed. The transmission belt generally uses rubber belt, metal belt and metal chain. CVT is truly stepless. Its advantages are light weight, small volume and few parts. Compared with at, CVT has higher operation efficiency and lower fuel consumption. However, the disadvantage of CVT is also obvious, that is, the transmission belt is easy to be damaged and can not bear large load. It can only be used for low-power and low torque vehicles with a displacement of about 1 liter. Therefore, it occupies less than 4% of the automatic transmission.