1, with or without grades
Hydraulic automatic transmission AT is a stepped transmission, which is a combination of hydraulic torque converter and planetary gear transmission. CVT continuously variable gearbox saves complex and bulky gear combination variable speed transmission, and only uses two sets of pulleys for variable speed transmission.
2. Principles
In principle, because the range of automatic speed change and torque change of hydraulic torque converter is not large enough, in order to improve efficiency, several rows of planetary gears are connected in series behind the turbine, and the hydraulic control system will automatically control the planetary gears with the change of engine work, thus realizing automatic speed change and torque change.
The transmission pulley of CVT has a strange structure, which is divided into two movable halves, which can be relatively close or separated. The conical disk can be tightened or opened under the hydraulic thrust, and the width of the V-shaped groove can be adjusted by extruding the steel chain. When the conical disk moves inward and tightens, the steel chain will move out of the center of the circle under the extrusion of the conical disk, and vice versa. In this way, the diameter of the disc driven by the steel chain increases and the transmission ratio changes.
Step 3 use
AT doesn't use clutch to shift gears, with small shift change, stable connection and simple operation, which brings convenience to drivers and comfort to passengers.
Because CVT has no gear shift of general automatic transmission, and there is no shift process of automatic transmission, the shift frustration caused by CVT also disappears, so the power output of CVT transmission is linear and very smooth in actual driving.
4. Maintenance and repair
There is no difference between AT and CVT in maintenance and repair. It is aimed at the degree of wear, the axis and the shell to increase the service life of the transmission.
Extended data
CVT (Continuously Variable Transmission), directly translated as continuously variable transmission, is what we often call continuously variable gearbox. As the name implies, it has no specific gear, and it is similar to an automatic gearbox in operation, but the change of speed ratio is different from the trip and shutdown process of the automatic gearbox, but continuous, so the power transmission is continuous and stable.
CVT technology has once again become one of the new technologies that people pay attention to. The cars sold in the market mainly include manual transmission (MT), automatic transmission (AT), continuously variable transmission (CVT) and power shift (DCT).
AT doesn't use clutch to shift gears, with small shift change, stable connection and simple operation, which brings convenience to drivers and comfort to passengers.
However, there are also many shortcomings. First, it is slow to respond to speed changes and insensitive to manual gears, so many riders like to drive manual gears; Second, the fuel consumption is uneconomical, the transmission efficiency is low and the torque range is limited. The introduction of electronic control technology has improved this problem. Third, the mechanism is complex and it is difficult to repair. The high-speed circulating hydraulic oil in the torque converter will produce high temperature, so the specified high-temperature resistant hydraulic oil should be used. In addition, if the car cannot be started due to insufficient battery power, it cannot be started by a cart or trailer. If the faulty vehicle is towed away, the driving wheel must be off the ground to protect the automatic wave gear from damage.
References:
Baidu encyclopedia -—CVT Baidu encyclopedia -at