CVT gearbox is controlled by hydraulic pressure, which changes the inner diameter of helical gear, produces pressure on steel belt or chain, and transmits power by friction. It should be noted that CVT gearbox transmits power through static friction, and there is no sliding friction between bevel gear and steel belt during transmission.
Because once sliding friction occurs, the friction resistance will be greatly reduced, and it must be friction and wear during the relative sliding between the steel belt and the bevel wheel. The relationship between the cone wheel and the steel belt can be likened to a person walking on the ice. When the pressure between the sole and the ice is large enough, the static friction can be increased.
People can walk on the ice, and once the sole slips and rubs against the ice, it is inevitable to slip. Friends who have been in contact with the conveyor belt should understand that applying a little butter to the machine can prevent the conveyor belt from slipping with the idler. In short, this is an example of using grease to reduce slippage; Another simpler example is that a dry towel may not stay on an inclined plane. If the towel is soaked in water or engine oil, it can stay on an inclined surface with the same inclination.
This is the principle of using the surface tension of liquid to increase the friction of contact surface, so don't look at oil narrowly, and a new conclusion will be drawn from another angle. When pressure is applied, the belt will form a pinch point in the middle of the wheel. This hug is very hard. The belt not only tightens, but also rotates.
The runway is squeezed first and then turned, which is actually the secret of CVT gearbox to overcome slippage. The pulley consists of two conical pulleys. The distance between them can be changed by hydraulic pressure. As the distance between them increases, the belt will run deeper than the surface of the pulley. On the other hand, if the distance is reduced, it will come out from the surface of the pulley, and the distance between parts will be adjusted to tension the belt. The belt has several layers of steel bars locked on both sides of the T-piece, so it can't run unless it is tightened first.
The way to solve the slip of CVT gearbox is to keep enough and proper pressure between bevel gear and steel belt. This is a complete automatic control system. Under the command of the computer, the steel strip is squeezed into the conical wheel, and the static friction force is greater than the force driving the steel strip. In this process, the movement of the steel belt is dynamic and static, and the movement makes the driving wheel rotate with the rotation of the driving wheel, and the static point of the steel belt contacts with the driving wheel and contacts with the driving wheel.
Contact with two conical wheels, no relative sliding at rest. In fact, if we simply realize the purpose of transferring kinetic energy. We can make the conical wheel rougher to increase the friction force, and we don't need to spray oil, and we don't need to spend so much effort to solve the problem by increasing the extrusion force of the conical wheel. The steel belt used in the gearbox requires very high durability, fatigue resistance and strength. Japan, Germany, the United States, Austria, Sweden, France and other countries have the highest level of cast steel, and there is still a certain gap between China and these countries.
In addition, the steel belt and steel chain of CVT gearbox are basically in the hands of Bosch and Schaeffler in Germany. Because of patent barriers, it is extremely difficult for domestic enterprises to avoid patents and manufacture steel belts. In addition, these two car companies basically monopolize CVT steel belts and steel chains, so it is naturally impossible to give up patents. Therefore, CVT transmission is not easy to slip, and its service life is greatly improved compared with the past.
But this is only relative. After all, it took a long time to disassemble the CVT, and you can still see the tapered pulley with obvious wear marks. With this word, there is absolutely no wear and tear. It doesn't exist, but don't be too nervous! Wear is everywhere, CVT is not fragile; The surface of the cone is not absolutely smooth, and the oil on the rough surface will increase the friction (under sufficient pressure). Therefore, CVT slippage is not common because it is very serious. After the machine is fixed, CVT can be used normally, so don't worry about slipping!