The mainstream gearboxes currently used in automobiles include AT gearboxes, DCT (or DSG) gearboxes and CVT gearboxes. Among them, AT gearboxes are more common, DCT (or DSG) gearboxes are currently mainly used by German cars or domestic brands, while CVT gearboxes are the favorite of Japanese cars. Of course, some domestic brands also use them.
Picture
The two more famous manufacturers of AT gearboxes are Japan Aisin and ZF, which also reflects from the side that Japan does not lack AT gearbox technology. However, in comparison, Japanese cars are still mainly equipped with CVT gearboxes, and the reason is closely related to Japan's development concept.
Picture
Japanese cars generally have lower fuel consumption. There are many factors that affect automobile fuel consumption. In addition to the engine and gearbox, there are also main reduction ratio, vehicle weight, drag coefficient, tires, etc. Among them, the engine and gearbox are the two most important factors. How much does the CVT gearbox affect fuel consumption?
CVT transmission, also known as continuously variable transmission, has a relatively simple structure, mainly including basic components such as driving wheel set, driven wheel set, metal belt and hydraulic pump. The metal belt is composed of two bundles of metal rings and hundreds of metal sheets. Both the driving wheel set and the driven wheel set are composed of movable disc and fixed disc. The pulley on the side close to the oil cylinder can slide on the shaft, while the other side is fixed.
Picture
Both the movable disc and the fixed disc are conical structures, and their conical surfaces form V-shaped grooves to mesh with the V-shaped metal transmission belt. The power output from the engine output shaft is first transmitted to the driving wheel of the CVT, then transmitted to the driven wheel through the V-shaped transmission belt, and finally transmitted to the wheels through the reducer and differential to drive the car.
The working process of the CVT transmission is to change the working radius of the meshing of the driving wheel and the driven wheel cone surface with the V-shaped transmission belt by axial movement of the movable disc of the driving wheel and the driven wheel, thereby changing the transmission ratio. The axial movement of the movable disc is achieved by the driver adjusting the oil cylinder pressure of the driving wheel and the driven wheel hydraulic pump through the control system according to the needs. Since the working radius of the driving wheel and the driven wheel can be adjusted continuously, stepless speed change is achieved.
Through the entire shifting process of the CVT transmission, it is not difficult to find several advantages of it:
First, fuel saving. Since CVT can achieve stepless speed change in a fairly wide range, it can obtain the best match between the transmission system and the engine working conditions, thereby improving the fuel economy of the whole vehicle.
Secondly, power. Due to the stepless speed change characteristics of CVT, the transmission ratio with the largest backup power can be obtained, so its power is significantly better than MT and AT transmissions.
The third is emission. The CVT has a wide speed ratio working range, which can make the engine work in the best working conditions, thereby improving the combustion process and reducing exhaust emissions.
Finally, cost. The CVT system has a simple structure and fewer parts than AT. Once automakers start mass production, the cost of CVT will be lower than AT.
